Fig. 6 (a)  $t_{\mathrm{phy}} - t_{\mathrm{ox}}$  plot, (b)  $J - V$  plot, and (c)  $J - t_{\mathrm{ox}}$  plot of the MIM capacitor with  $20 \mathrm{nm}$ -thick  $\mathrm{TiO_2}$  deposited by (black) the conventional sequence and (red) the  $\mathrm{H}_2\mathrm{O}$ -added sequence with a  $\mathrm{H}_2\mathrm{O}$  feeding time of  $10 \mathrm{s}$ .

A line chart showing the relationship between t_{hyb} [nm] and l_{0} [µm], comparing the effect of the conventional vs. the H2O-added sequence.

A scatter plot displaying leakage current density against applied voltage, comparing the effect of the conventional vs. the H2O-added sequence.

A scatter plot showing leakage current density at -0.8 V against t_{hyb} [nm], comparing the effect of the conventional vs. the H2O-added sequence.

| t_{hyb} [nm] | l_{0} [µm] Conventional | l_{0} [µm] H2O-added |
|---|---|---|
| 0 | 0 | 0 |
| 5 | 0.2 | 0.2 |
| 10 | 0.4 | 0.4 |
| 15 | 0.6 | 0.6 |
| 20 | 0.8 | 0.8 |
| 25 | 1 | 1 |

| Applied Voltage [V] | Leakage current density [A/cm^{2}] Conventional | Leakage current density [A/cm^{2}] H2O-added |
|---|---|---|
|-1.5 | 10^{-6} | 10^{-7} |
|-1.0 | 10^{-7} | 10^{-8} |
|-0.5 | 10^{-8} | 10^{-8} |
| 0.0 | 10^{-9} | 10^{-8} |
| 0.5 | 10^{-6} | 10^{-6} |
| 1.0 | 10^{-4} | 10^{-4} |
| 1.5 | 10^{-3} | 10^{-3} |

| t_{hyb} [nm] | Leakage current density @ -0.8 V [A/cm^{2}] |
|---|---|
| 0.2 | 10^{-7} |
| 0.4 | 10^{-6} |
| 0.6 | 10^{-5} |
| 0.8 | 10^{-4} |

Answer: 93.5.

Answer: 97.8.

Answer: The y-intercept reflects the interfacial properties between the TiO₂ film and the top/bottom electrodes, implying that the additional H2O step does not induce any change at the interface of the TE or the BE.

Answer: Both the J–V curves and leakage current trends show that the TiO₂ films produced by the conventional and H₂O-enhanced processes behave nearly identically, indicating that their bulk electrical and interfacial properties are the same. The similar dielectric constants, unchanged y-intercepts, and overlapping leakage current behavior suggest that adding an H₂O feeding step does not negatively impact film quality or electrode interfaces, and that both films exhibit comparable crystallinity consistent with the rutile TiO₂ phase.

icdar2026-competition-data/train/atomic-layer-deposition/simulation-usecase/42/Yeonchoo Cho et al.pdf


The figure shows the thickness of ZnO as a function of ALD cycles at different temperatures over silicon and amorphous silicon substrates.

The figure illustrates the selectivity of a process as a function of ALD cycles at two different temperatures.

| ALD Cycles | 100°C on SiO₂ (nm) | 250°C on SiO₂ (nm) | 100°C on a-Si:H (nm) | 250°C on a-Si:H (nm) |
|------------|----------------------|----------------------|------------------------|------------------------|
| 0          | 0.0                 | 0.0                 | 0.0                   | 0.0                   |
| 20         | 2.0                 | 3.0                 | 0.0                   | 0.0                   |
| 40         | 4.0                 | 6.0                 | 0.0                   | 0.0                   |
| 60         | 6.0                 | 9.0                 | 0.0                   | 0.0                   |
| 80         | 8.0                 | 12.0                | 0.5                   | 0.0                   |
| 100        | 10.0                | —                   | 1.5                   | 0.2                   |
| 120        | —                   | —                   | 3.0                   | 0.5                   |
| 160        | —                   | —                   | 6.0                   | 1.0                   |
| 200        | —                   | —                   | 8.0                   | 2.0                   |

| ALD Cycles | Selectivity @ 100°C | Selectivity @ 250°C |
|------------|----------------------|----------------------|
| 0          | 1.00                | 1.00                |
| 40         | 0.95                | 1.00                |
| 80         | 0.85                | 1.00                |
| 120        | 0.65                | 0.95                |
| 160        | 0.45                | 0.85                |
| 200        | 0.30                | 0.75                |

Answer: For a deposition temperature of 100 °C, the selectivity decreases from 1.0 to 0.96 at 80 ALD cycles. By further increasing the number of cycles, the selectivity drops to 0.85 (at 100 cycles), which corresponds to a ZnO thickness of ∼1 nm on the NGA. For a deposition temperature of 250 °C, the selectivity, S, remains 1 until 110 cycles and then decreases to 0.95 at 140 ALD cycles.

Answer: The selectivity  is abruptly lost at 350 °C.

Answer: A larger nucleation delay is observed for deposition at 250 °C with a-Si:H substrate

Answer: Yes

icdar2026-competition-data/train/atomic-layer-deposition/simulation-usecase/5/Alfredo Mameli et al.pdf


Figure 2.  $\mathrm{ZnO}$  film thickness measured by in situ SE as a function of the number of ALD cycles performed on substrates with a native  $\mathrm{SiO}_2$  surface (closed squares) and with a  $\sim 10 \mathrm{nm}$  thick a-Si/H layer (open squares). On  $\mathrm{SiO}_2$ , the  $\mathrm{ZnO}$  film thickness increases linearly after a short delay of a few cycles, whereas on a-Si/H, the  $\mathrm{ZnO}$  deposition experiences a relatively long nucleation delay. Only after 80 ALD cycles, the growth also starts on the a-Si/H and enters a linear regime at about 120 cycles. Both depositions were carried out at  $100^{\circ}\mathrm{C}$ .

The line chart shows the thickness of ZnO deposited on SiO2 (closed squared) and a-Si:H (open squares) substrates as a function of ALD cycles. The thickness increases linearly with increasing cycles.

| ALD Cycles | ZnO Thickness on SiO₂ (nm) | ZnO Thickness on a-Si:H (nm) |
|------------|-----------------------------|--------------------------------|
| 0          | 0.0                         | 0.0                            |
| 10         | 2.0                         | 0.0                            |
| 20         | 4.0                         | 0.0                            |
| 30         | 6.0                         | 0.0                            |
| 40         | 8.0                         | 0.2                            |
| 50         | 10.0                        | 0.5                            |
| 60         | 12.0                        | 1.0                            |
| 70         | 14.0                        | 2.0                            |
| 80         | 16.0                        | 3.0                            |
| 90         | —                           | 4.0                            |
| 100        | —                           | 5.0                            |
| 110        | —                           | 6.0                            |
| 120        | —                           | 7.0                            |
| 130        | —                           | 8.0                            |

Answer: Yes

Answer: On SiO2, the ZnO film thickness increases linearly after a short delay of a few cycles, whereas on a-Si/H, the ZnO deposition experiences a relatively long nucleation delay. Only after 80 ALD cycles, the growth also starts on the a-Si/H and enters a linear regime at about 120 cycles.

Answer: Both depositions were carried out at 100 °C.

Answer: Area-selective ALD of ZnO can be obtained by exploiting the difference in nucleation delays on the two surfaces. Furthermore, the nucleation curves suggest a selectivity window (expressed as the number of ALD cycles for which no deposition is obtained on the a-Si/H) of about 80 ALD cycles before deposition occurs on both surfaces and the selectivity is lost. The key reason for the difference in nucleation delay lies in the surface chemistry because dissimilar surface groups have distinct kinetic barriers toward various thermodynamically favorable end states.


Figure 6. Selectivity for  $80~\mathrm{ZnO}$  ALD cycles as a function of the deposition temperature. The insets show the top-view SEM images of patterns realized using the same EBID parameters and number of ALD cycles, but different  $\mathrm{ZnO}$  growth temperatures (100, 150, and  $250^{\circ}\mathrm{C}$ ); scale bars are  $500~\mathrm{nm}$ . The horizontal dotted line at  $S = 1$  indicates perfect selectivity.

The plot shows selectivity versus deposition temperature where selectivity increases with increasing deposition temperature.

SEM Microscopy images of samples deposited at different temperatures demonstrating selectivity

| Deposition temperature (°C) | Selectivity |
|---|---|
| 100 | 0.82 |
| 150 | 0.96 |
| 200 | 0.99 |
| 250 | 1.00 |

| 100 °C | 150 °C | 250 °C |
|---|---|---|
| ![](100°C_image.png) | ![](150°C_image.png) | ![](250°C_image.png) |

Answer: the selectivity was calculated using the ZnO surface coverage in and outside the patterned area, as measured by top-view SEM.

Answer: The SEM-measured selectivity data confirmed the results obtained using SE: the selectivity increases with the deposition temperature up to 250 °C

Answer: Yes

Answer:
The selectivity increases as follows
a.  0.83 at 100 °C
b. 0.97 at 150 °C
c. 0.99 at 200  °C
d. 0.99 at  250 °C


Figure 2. Deposition rate versus exposure of  $\mathrm{SiO}_2$  (red diamonds) and  $\mathrm{Si}_3\mathrm{N}_4$  (green circles) films deposited from chloro-silane precursors by ALD at  $450^{\circ}\mathrm{C}$  with less than  $2\%$  absolute variation on per cycle deposition rate.

The chart shows the per cycle deposition rate of SiO2 and Si3N4 as a function of exposure time in Torr·s.

| Exposure (Torr·s) | Per cycle Dep. Rate (Å) SiO₂ | Per cycle Dep. Rate (Å) Si₃N₄ |
|--------------------|-------------------------------|---------------------------------|
| 0.02              | 0.4                           | -                               |
| 0.05              | 0.8                           | -                               |
| 0.10              | 1.0                           | -                               |
| 1.0               | -                             | 0.5                             |
| 3.0               | -                             | 0.9                             |
| 10.0              | -                             | 1.1                             |

Answer: Films deposited from chloro-silane precursors by ALD at 450 °C with less than 2% absolute variation on per cycle deposition rate.

Answer: The figure compares the relative reactivity for simple chloro-silane precursors (e.g., DCS,HCDS, etc.)

Answer: No

Answer: Precursor exposure was varied by changing the exposure time, the exposure partial pressure, or both. Deposition rate was determined by measurement of the thickness after deposition and dividing by the number of ALD cycles performed. The very long precursor exposure for deposition of silicon nitride makes this process economically unviable, due to both the excessive throughput time per film deposited and the unacceptably high volume of silicon precursors consumed.

icdar2026-competition-data/train/atomic-layer-deposition/simulation-usecase/53/Ciaran A. Murray et al.pdf


Figure 2. Duo-linear plot of  $\mathrm{TiO_2}$  film thickness versus the number of cycles and a silicon reference (reprinted with permission from [6]).

The chart shows the thickness of TiO2 ALD deposited on PMMA and silicon substrates as a function of the number of cycles, showing cycle dependent GPCs.

| Number of cycles | Thickness (Å) on PMMA |Thickness (Å) on silicon |
|------------------|---------------|---------------|
| 0               | 0             |0|
| 100             | 150           |75|
| 150             | 250           |100|
| 200             | 300           |120|
| 250             | 350           |150|
| 300             | 360           |160|
| 400             | 400           |200|
| 500             | 450           |250|

Answer: It could be that PMMA as a substrate enables enhanced growth, whereas TiO2 growth on TiO2 does not enable this.

Answer: SiO2 looks more like TiO2 in structure than PMMA does so it is likely that the growth on SiO2 looks more like the growth on TiO2 than on PMMA.

Answer: After these number of cycles the substrate does not have an influence on the growth anymore and just the TiO2 acts as a starting substrate. As this is the same for both cases it is likely that the same GPC is acquired.

Answer: The GPC is 0.74 angstrom/cycle.

icdar2026-competition-data/train/atomic-layer-deposition/simulation-usecase/6/Mina Shahmohammadi et al.pdf


Figure 11. Simulated GPC data, estimated from both the thickness of the simulated thin film and from the deposited mass, compared to the growth rate reported in ref 26. The GPC estimated from the average mass includes the error bars, obtained as a standard deviation from series of simulations.

The scatter plot shows the relationship between temperature and growth-per-cycle in angstroms. Data points represent measurements from Yousfi et al., kMC (average mass), and kMC (average thickness). The trend shows increasing GPC with increasing temperature.

| Temperature / °C | Growth-per-cycle / angstrom Yousfi|Growth-per-cycle / angstrom Model|
|---|---|---|
| 0 | 0.0 |0.0 |
| 25 | 0.0 |0.0 |
| 50 | 0.25 |1.3|
| 75 | 0.6|2.2 |
| 100 |1.3| 2.6 |
| 125 | 2.0|2.6 |
| 150 | 2.1|2.6 |
| 175 | 2.1|2.6 |
| 200 | 2.0|- |

Answer: No they do not overlap in max GPC, however, the trend is similar. In addition, both methods result in an optimal deposition temperature of about 175 degrees celcius.

Answer: For too high temperatures, there can be desorption of surface species, this can result in lower GPC.

Answer: Yes

Answer: That the temperature of the process is always higher than the bubbler temperature, such that condensation does not occur.

icdar2026-competition-data/train/atomic-layer-deposition/simulation-usecase/8/Timo Weckman et al.pdf


Figure 12. GPC as a function of temperature in the case where the barriers for the second ligand elimination reaction (LE2) have been increased by  $0.10\mathrm{eV}$ . The elimination of the MEZ from the surface is clearly the crucial step in the deposition process. Increasing the barrier shifts the observed behavior to higher temperature as the ligand-elimination reaction can occur only at elevated temperatures.

The scatter plot shows the relationship between temperature and growth-per-cycle in angstroms. This is shown for experimental data, a kMC model, and an additional model with different input variables.

| Temperature / °C | Growth-per-cycle / angstrom Yousfi|Growth-per-cycle / angstrom Model|Growth-per-cycle / angstrom Model LE2 +0.1 eV|
|---|---|---|---|
| 0 | 0.0 |0.0 |0.0 |
| 25 | 0.0 |0.0 |0.0 |
| 50 | 0.25 |1.3|0.0 |
| 75 | 0.6|2.2 |0.6|
| 100 |1.3| 2.6 |1.8|
| 125 | 2.0|2.6 |2.4|
| 150 | 2.1|2.6 |2.5|
| 175 | 2.1|2.6 |2.7|
| 200 | 2.0|- |-|

Answer: Yes, this is especially the case for the lower temperatures where there seems to be a short delay or thresshold temperature.

Answer: This needs to be overcome by added energy via increased temperature.

Answer: 2.3 angstrom per cycle

Answer: This is not yet visible in the graph for this temperature range, but if the model behaves according to the actual physical situation this should be the case.


Figure 13. Fraction of persisting ligands as a function of temperature in the simulation. Experimental data, obtained from ref 12, are measured for low and high water exposures. Low and high water exposures correspond to  $10^{4}$  and  $10^{7} \mathrm{~L}$ , respectively.

The scatter plot shows the fraction of ethyl-ligands persisting at various temperatures. The simulated data points are represented by red squares, while the experimental data points are shown by gray triangles. The graph shows the fraction of ethyl-ligands persisting decreasing with increasing temperature.

| Temperature / °C | Fraction of ethylligands persisting Simulated |Fraction of ethylligands persisting Long exposure |Fraction of ethylligands persisting short exposure |
|---|---|---|---|
| 25 | 0.83 |-|-|
| 50 | 0.6 |-|-|
| 75 | 0.5 |-|-|
| 100 | 0.45 |0.3|0.75|
| 120 | 0.45 |-|-|
| 150 | 0.45 |0.15|0.55|
| 180 | 0.45 |-|-|
| 200 | - |0.05|0.12|

Answer: Both for long and short water exposures the experimental data does not overlap with the simulated data indicating that the model is incomplete.

Answer: Water is supposed to react with the ligands and remove them. If the exposure is shorter, it could be that there are less ligand removing reactions.

Answer: The fraction is close to one, this means that the ligands are not removed and therefore also not replaced with reactive surface sites to which new precursor molecules can adsorb. This means it is unlikely there will be any substantial growth at this temperature.

Answer: The layers grown with ALD are usually used in devices where carbon from ligands can degrade the material properties making them incompatible with the application of interest.


Figure 14. W ALE using  $\mathrm{O}_2 / \mathrm{O}_2$ ,  $\mathrm{BCl}_3$ , and HF as reactants at  $207^{\circ}\mathrm{C}$ . (a)  $\mathrm{WO}_3$  thickness increases after  $\mathrm{O}_2 / \mathrm{O}_3$  exposure and decreases after  $\mathrm{BCl}_3 / \mathrm{HF}$  exposure. (b) W etching occurs with an etch rate of  $2.44\mathrm{\AA}/$  cycle. Reproduced with permission from ref 32. Copyright 2017 American Chemical Society.

The figure shows the thickness of WO₃ after exposure to O₂/O₃ and BCl₃/HF as a function of the number of half-cycles.

The figure shows the thickness of W as a function of the number of half-cycles at 207 °C, with O2/O3, BCl3 and HF exposure. The figure shows an etch rate of 2.44 Å/cycle.

| Number of Half-Cycles | WO₃ Thickness (Å) After O₂/O₃ | WO₃ Thickness (Å) After BCl₃/HF |
| --- | --- | --- |
| 0 | 38 | 27 |
| 10 | 43 | 35 |
| 20 | 37 | 30 |
| 30 | 33 | 25 |
| 40 | 30 | 23 |
| 50 | 26 | 20 |
| 60 | 26 | 17 |

| Number of Half-Cycles | W Thickness (Å) |
|---|---|
| 0 | 230 |
| 10 | 215 |
| 20 | 200 |
| 30 | 190 |
| 40 | 175 |
| 50 | 170 |
| 60 | 155 |

Answer: The experiment was performed at 207 °C with the following exposure: 3150 mTorr s of O2/O3, 329 mTorr s of BCl3, and 2800 mTorr s of HF.

Answer: The W thickness decreases as the number of half-cycles increases.

Answer: As can be seenin the figure, the etch per cycle is 2.44 Å/cycle.

Answer: The thickness of the WO3 increases after exposure to O2/O3 because it can oxidize the surface. However, it decreases after exposure to BCl3/HF.

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/14/Mechanisms of Thermal Atomic Layer Etching.pdf


Figure 5. Film thickness versus number of ALE cycles for various materials using HF as fluorine reactant and (a) TMA or (b) DMAF as metal precursor for ligand-exchange. Reproduced with permission from ref 23. Copyright 2016 American Chemical Society.

The chart shows how the film thickness of various materials (TiN, ZrO₂, SiO₂, Si₃N₄, HfO₂, Al₂O₃) changes over cycles at 300°C using TMA.

The chart shows how the film thickness of various materials (TiN, SiO₂, Si₃N₄, ZrO₂, HfO₂, Al₂O₃) changes over cycles at 250°C using DMAC.

| Number of Cycles | TiN | ZrO₂ | SiO₂ | Si₃N₄ | HfO₂ | Al₂O₃ |
|---|---|---|---|---|---|---|
| 0 | 68 | 50 | 48 | 40 | 55 | 44 |
| 50 | - | 48 | - | - | 50 | 20 |
| 100 | - | 53 | - | - | 43 | 0 |
| 200 | 70 | 48 | 43 | 42 | 37 | 0 |

| Number of Cycles | TiN | SiO₂ | Si₃N₄ | ZrO₂ | HfO₂ | Al₂O₃ |
|---|---|---|---|---|---|---|
| 0 | 70 | 50 | 40 | 50 | 50 | 48 |
| 25 | 70 | 51 | 40 | 22 | 40 | 40 |
| 50 | 70 | 50 | 40 | 5 | 20 | 38 |
| 100 | 70 | 50 | 40 | 0 | 0 | 18 |

Answer: Only Al2O3, HfO2, and ZrO2 exhibit etching behavior. For the other materials, the film thickness remains constante over the number of cycles.

Answer: TiN has the highest film thickness values.

Answer: The TMA ALE cycle was performed at 300 °C.

Answer: As can be seen in the figure, Al2O3 exhibit the highest etch rates using TMA as reactant.


Figure 6. Thickness change versus number of ALE cycles for crystalline and amorphous  $\mathrm{HfO}_2$  using HF and  $\mathrm{TiCl}_4$  as reactants. Reproduced with permission from ref 29. Copyright 2020 American Vacuum Society.

The chart shows the thickness change of crystalline and amorphous HfO₂ as a function of the number of ALE cycles at 250°C using HF/TiCl₄. The etch rate is 0.02 Å/cycle for the crystalline sample and 0.35 Å/cycle for the amorphous.

| Number of ALE Cycles | crystalline | amorphous |
| --- | --- | --- |
| 0 | 0 | 0 |
| 50 | 0 | -18 |
| 100 | 0 | -30 |
| 150 | -2 | -45 |
| 200 | -3 | -80 |
| 300 | -5 | -95 |

Answer: At 250 °C.

Answer: In both cases the film thickness decreases, but the change is more significant for the amorphous HfO2 film.

Answer: HF and TiCl4 were used as reactants.

Answer: The etch rate is 0.02 Å/cycle for the crystalline film and for the amorphous film: 0.36 Å/


Figure 7. Temperature dependence of  $\mathrm{Al}_2\mathrm{O}_3$  ALE using  $\mathrm{SF}_4$  and  $\mathrm{Sn(acac)}_2$ . Etch rate increases from  $0.04 \mathrm{Å / cycle}$  at  $150^{\circ}\mathrm{C}$  to  $0.25 \mathrm{Å / cycle}$  at  $225^{\circ}\mathrm{C}$ .

The figure presents the film thickness of Al₂O₃ as a function of the number of atomic layer etching (ALE) cycles at four different temperatures: 150 °C, 175 °C, 200 °C, and 225 °C. Each dataset shows a monotonic decrease in thickness with increasing cycles, but the rate of etching significantly depends on temperature. At 150 °C, the change is minimal, indicating very slow etching, while the steepest decrease is observed at 200 °C and 225 °C, demonstrating a higher etch rate. The linearity in most cases suggests a consistent per-cycle removal, particularly at elevated temperatures.

| Number of Cycles | Thickness at 150 °C (Å) | Thickness at 175 °C (Å) | Thickness at 200 °C (Å) | Thickness at 225 °C (Å) |
|------------------|--------------------------|--------------------------|--------------------------|--------------------------|
| 0                | 190                      | 190                      | 190                      | 190                      |
| 50               | 189                      | 187                      | 182                      | 180                      |
| 100              | 188                      | 184                      | 174                      | 170                      |
| 200              | 187                      | 179                      | 160                      | 155                      |

Answer: The Al₂O₃ thickness consistently decreases with increasing ALE cycles at all temperatures, but the rate of this decrease varies. At 150 °C, the reduction in thickness is minimal, indicating limited etching. In contrast, at 200 °C and 225 °C, the film is etched more aggressively, with a sharp decline in thickness over 200 cycles. This suggests that higher temperatures enhance the etch efficiency, likely by improving precursor reactivity or facilitating the removal of reaction byproducts.

Answer: 150 °C.

Answer: Increased SF₄ and Sn(acac)₂ reactivity at higher temperatures, enhanced byproduct desorption, improved surface diffusion.

Answer: Yes

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/17/SF4 as the Fluorination Reactant for Al2O3 and VO2.pdf


Figure 10. Review of literature data of physical sputter rates reported for Si versus the square-root of Ar ion energy up to energies of  $400\mathrm{eV}^{95,118 - 132}$  along with SRIM simulation results. The threshold for physical sputtering of Si is  $\approx 20\mathrm{eV}$ . The large scatter with regard to the threshold energy of physical sputtering for Si shows the difficulty of controlling experimental conditions.

This figure presents a comparative scatter plot of experimentally reported physical sputter yields of silicon (Si) as a function of the square root of Ar⁺ ion energy, compiled from multiple literature sources. The wide dispersion of data points highlights strong experiment-to-experiment variability, particularly near the sputtering threshold. A SRIM simulation curve is included as a reference, indicating an approximate threshold energy of ~20 eV for Si sputtering. The figure emphasizes the inherent difficulty in achieving precise control in physical sputtering processes.

| Ion Energy [eV] | Square Root of Ion Energy [eV^1/2] | Sputter Yield [Si/Ar^+] |
|---|---|---|
| 0 | 0 | 0 |
| 25 | 5 | 0.05 |
| 100 | 10 | 0.1 |
| 225 | 15 | 0.2 |
| 400 | 20 | 0.3 |

Answer: This comparison highlights the sensitivity of physical sputtering to ion energy, especially near the threshold region. In ALE, precise control of ion energy is essential to remain within the ALE window, avoiding uncontrolled sputtering. The observed scatter emphasizes the need for carefully tuned plasma and ion conditions to achieve repeatable, layer-by-layer etching.

Answer: ~20 eV, as suggested by both experimental data and SRIM simulations.

Answer: Yes. Higher ion energies generally lead to increased physical sputtering of Si.

Answer: Variations in ion energy calibration, Differences in surface condition and crystallinity, Experimental setup and measurement uncertainty, Ion incidence angle and beam conditions

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/2/Atomic Layer Etching at the Tipping Point An Overview.pdf


Figure 11. Review of literature data of physical sputter rates for  $\mathrm{SiO_2}$  versus the square-root of Ar ion energy up to energies of  $400\mathrm{eV}^{95,122,124,128,133 - 137}$  The threshold for physical sputtering of  $\mathrm{SiO_2}$  is  $\approx 45\mathrm{eV}$ .

This figure compiles experimental literature data and SRIM simulation results showing the physical sputter yield of SiO₂ as a function of the square root of Ar⁺ ion energy. The data reveal a clear sputtering threshold around ~45 eV, above which the sputter yield increases approximately linearly with ion energy. The wide scatter among experimental points highlights strong sensitivity to experimental conditions such as surface state, angle of incidence, and ion flux, emphasizing challenges in precise sputter control at low energies.

| Ion Energy [eV] | Sputter Yield [SiO₂/Ar⁺] |
|---|---|
| 0 | 0.0 |
| 5 | 0.0 |
| 10 | 0.0 |
| 15 | 0.0 |
| 20 | 0.0 |
| 25 | 0.0 |
| 30 | 0.0 |
| 35 | 0.0 |
| 40 | 0.0 |
| 45 | 0.0 |
| 50 | 0.0 |
| 55 | 0.0 |
| 60 | 0.0 |
| 65 | 0.0 |
| 70 | 0.0 |
| 75 | 0.0 |
| 80 | 0.0 |
| 85 | 0.0 |
| 90 | 0.0 |
| 95 | 0.0 |
| 100 | 0.0 |
| 105 | 0.0 |
| 110 | 0.0 |
| 115 | 0.0 |
| 120 | 0.0 |
| 125 | 0.0 |
| 130 | 0.0 |
| 135 | 0.0 |
| 140 | 0.0 |
| 145 | 0.0 |
| 150 | 0.0 |
| 155 | 0.0 |
| 160 | 0.0 |
| 165 | 0.0 |
| 170 | 0.0 |
| 175 | 0.0 |
| 180 | 0.0 |
| 185 | 0.0 |
| 190 | 0.0 |
| 195 | 0.0 |
| 200 | 0.0 |
| 205 | 0.0 |
| 210 | 0.0 |
| 215 | 0.0 |
| 220 | 0.0 |
| 225 | 0.0 |
| 230 | 0.0 |
| 235 | 0.0 |
| 240 | 0.0 |
| 245 | 0.0 |
| 250 | 0.0 |
| 255 | 0.0 |
| 260 | 0.0 |
| 265 | 0.0 |
| 270 | 0.0 |
| 275 | 0.0 |
| 280 | 0.0 |
| 285 | 0.0 |
| 290 | 0.0 |
| 295 | 0.0 |
| 300 | 0.0 |
| 305 | 0.0 |
| 310 | 0.0 |
| 315 | 0.0 |
| 320 | 0.0 |
| 325 | 0.0 |
| 330 | 0.0 |
| 335 | 0.0 |
| 340 | 0.0 |
| 345 | 0.0 |
| 350 | 0.0 |
| 355 | 0.0 |
| 360 | 0.0 |
| 365 | 0.0 |
| 370 | 0.0 |
| 375 | 0.0 |
| 380 | 0.0 |
| 385 | 0.0 |
| 390 | 0.0 |
| 395 | 0.0 |
| 400 | 0.0 |

Answer: Understanding the sputtering threshold and energy-dependent yield is critical for ALE because it defines the narrow ion-energy window where material removal is controllable and self-limiting. Operating below the physical sputtering regime enables selective, damage-minimized etching, while exceeding it risks uncontrolled material loss and reduced process selectivity.

Answer: The sputter yield of SiO₂ increases approximately linearly with the square root of ion energy once the sputtering threshold is exceeded.

Answer: Yes. The sputter yield remains near zero at low ion energies and increases only after exceeding a threshold of approximately 45 eV.

Answer: Surface condition of SiO₂, Ion incidence angle, Ion energy distribution, Experimental setup variations, Measurement methodology differences


Figure 5. Thickness measurements were acquired after etching of amorphous as-deposited ALD  $\mathrm{MoS}_2$  films on  $\mathrm{SiO}_2$  coupons at  $200^{\circ}\mathrm{C}$ . Both SE and XRR thickness measurements show a linear decrease in film thickness. A linear fit of the data produces an etching rate of 0.05 nm/cycle for amorphous  $\mathrm{MoS}_2$ .

Panel (a) shows no change in thickness when only Hhfac is used, even after 20 pulses.

Similarly, panel (b) indicates no measurable thickness reduction with H₂ plasma alone.

In contrast, panel (c) demonstrates a steady linear decrease in film thickness when both Hhfac and H₂ plasma are applied in combination, highlighting the synergistic effect of this treatment for etching. These results suggest that neither precursor nor plasma alone is sufficient to etch the surface, but their combination results in controlled material removal.

| Number of pulses/cycles | Thickness change (nm) |
|--------------------------|------------------------|
| 0                        | 0                      |
| 5                        | 0                      |
| 10                       | 0                      |
| 15                       | 0                      |
| 20                       | 0                      |

| Number of pulses/cycles | Thickness change (nm) |
|--------------------------|------------------------|
| 0                        | 0                      |
| 5                        | -0.5                   |
| 10                       | -1.0                   |
| 15                       | -1.5                   |
| 20                       | -2.0                   |

Answer: The thickness decreases by approximately 2.0 nm after 20 cycles.

Answer: (a): Hhfac, no thickness change, (b): H₂ plasma, no thickness change , (c): Hhfac + H₂ plasma, linear decrease in thickness

Answer: In atomic layer etching, precursor adsorption alone often does not result in material removal due to the lack of activation energy. Similarly, plasma exposure alone may not modify the surface sufficiently for etching to occur. The combination of Hhfac and H₂ plasma enables a two-step mechanism where Hhfac modifies the surface chemically, and the H₂ plasma provides energetic species to drive desorption or reaction of surface-bound fragments.

Answer: No

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/22/Thermal Atomic Layer Etching of MoS2 Using MoF6 and H2O.pdf


Figure 4. Expansion showing thickness of  $\mathrm{ZnS}$  film during the first 5  $\mathrm{ZnS}$  ALE cycles in Figure 3.

The line chart shows an expanded view of the ZnS thickness evolution over the first few ALE cycles. It plots the ZnS film thickness as a function of ZnS ALE cycle number using HF and TMA as reactants at 300 °C, focusing only on the 0–5 cycle region. The initial ZnS films used for ALE were deposited by ALD at 100 °C.

| ALE Cycles | ZnS Thickness (Å) | Stage                    |
|------------|--------------------|-----------------------------|
| 0          | 203             | Initial ZnS thickness       |
| 0          |   -                 | After HF Exposure           |
| 0          |     -               | After TMA Exposure          |
| 0.5        |     -               | Initial ZnS thickness       |
| 0.5        | 203.52      | After HF Exposure        |
| 0.5        |       -             | After TMA Exposure          |
| 1          |         -           | Initial ZnS thickness       |
| 1          |         -           | After HF Exposure           |
| 1          | 203.62        | After TMA Exposure       |
| 1.5        |       -             | Initial ZnS thickness       |
| 1.5        | 201.9         | After HF Exposure           |
| 1.5        |       -             | After TMA Exposure          |
| 2          |         -           | Initial ZnS thickness       |
| 2          |         -           | After HF Exposure           |
| 2          | 201.58        | After TMA Exposure       |
| 2.5        |        -            | Initial ZnS thickness       |
| 2.5        | 200             | After HF Exposure           |
| 2.5        |         -           | After TMA Exposure          |
| 3          |        -            | Initial ZnS thickness       |
| 3          |          -          | After HF Exposure           |
| 3          | 199.4          | After TMA Exposure       |
| 3.5        |           -         | Initial ZnS thickness       |
| 3.5        | 198             | After HF Exposure           |
| 3.5        |        -            | After TMA Exposure          |
| 4          |          -          | Initial ZnS thickness       |
| 4          |          -          | After HF Exposure           |
| 4          | 197.25        | After TMA Exposure      |
| 4.5        |        -            | Initial ZnS thickness       |
| 4.5        | 196             | After HF Exposure           |
| 4.5        |      -              | After TMA Exposure          |
| 5          |        -            | Initial ZnS thickness       |
| 5          |         -           | After HF Exposure           |
| 5          | 195.1            | After TMA Exposure          |

Answer:
1) HF Exposure: Fluorinates/modifies the ZnS surface.

2) Thickness Measurement.

3) TMA Exposure: Removes the modified layer.

4) Thickness Measurement. Measuring after each step verifies the self-limiting nature of each half-reaction and quantifies the individual contribution to the total etch per cycle.

Answer:
HF/TMA ALE: Pro: Chemically selective to ZnS; SiO₂ is resistant to HF under these conditions.

Thermal Decomposition: Con: Non-selective; relies on volatility, likely attacking both ZnS and SiO₂.

Answer: The larger drop after HF indicates it causes the major physical removal or volumetric change, likely by converting crystalline ZnS into a porous, volatile, or low-density zinc fluoride (ZnF₂) compound. The subsequent TMA step then cleans up this modified layer, causing a smaller but essential thickness change to complete the cycle.

Answer: This enables digital etch trimming of quantum dot layers with sub-nanometer precision. Engineers can remove exact numbers of monolayers to tune quantum confinement and emission wavelength after growth, or to expose a specific subsurface dot layer with minimal damage to adjacent layers.

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/23/Thermal Atomic Layer Etching of Zinc Sulfide.pdf


Figure 5. Thickness change of  $\mathrm{ZnS}$  film vs number of  $\mathrm{ZnS}$  ALE cycles at 225, 250, 275, and  $300^{\circ}\mathrm{C}$ . Initial  $\mathrm{ZnS}$  ALE films were grown at  $100^{\circ}\mathrm{C}$ .

The multiple line chart shows the reduction in ZnS film thickness with increasing ALE cycles (0–20) at temperatures from 225 °C to 300 °C for films initially deposited at 100 °C. All values display a linear decrease in thickness, confirming a constant etch per cycle and a well-controlled, self-limiting ALE process. The slope increases with temperature, indicating thermally activated etching, with the highest etch rate at 300 °C (~2.1 Å/cycle) and the lowest at 225 °C (~1.25 Å/cycle).

| Number of ALE Cycles | Change in ZnS Thickness (Å)  | Temperature |
|------------|------------------|-------------|
| 0          | 0                | 225 °C      |
| 0          | 0                | 250 °C      |
| 0          | 0                | 275 °C      |
| 0          | 0                | 300 °C      |
| 2          | -1.23            | 225 °C      |
| 2          | -1.86            | 250 °C      |
| 2          | -2.35            | 275 °C      |
| 2          | -3.59            | 300 °C      |
| 4          | -3.59            | 225 °C      |
| 4          | -5.20            | 250 °C      |
| 4          | -6.56            | 275 °C      |
| 4          | -7.80            | 300 °C      |
| 6          | -6.68            | 225 °C      |
| 6          | -8.91            | 250 °C      |
| 6          | -10.77           | 275 °C      |
| 6          | -11.88           | 300 °C      |
| 8          | -10.27           | 225 °C      |
| 8          | -12.25           | 250 °C      |
| 8          | -14.72           | 275 °C      |
| 8          | -16.71           | 300 °C      |
| 10         | -12.37           | 225 °C      |
| 10         | -15.84           | 250 °C      |
| 10         | -19.31           | 275 °C      |
| 10         | -20.79           | 300 °C      |
| 12         | -15.84           | 225 °C      |
| 12         | -19.18           | 250 °C      |
| 12         | -23.02           | 275 °C      |
| 12         | -24.87           | 300 °C      |
| 14         | -18.56           | 225 °C      |
| 14         | -23.02           | 250 °C      |
| 14         | -27.47           | 275 °C      |
| 14         | -29.94           | 300 °C      |
| 16         | -21.16           | 225 °C      |
| 16         | -27.22           | 250 °C      |
| 16         | -32.04           | 275 °C      |
| 16         | -34.27           | 300 °C      |
| 18         | -23.02           | 225 °C      |
| 18         | -30.93           | 250 °C      |
| 18         | -35.76           | 275 °C      |
| 18         | -38.24           | 300 °C      |
| 20         | -26.48           | 225 °C      |
| 20         | -34.27           | 250 °C      |
| 20         | -40.46           | 275 °C      |
| 20         | -43.18           | 300 °C      |

Answer: The process is thermally activated. Increasing the temperature from 225°C to 300°C nearly doubles the material removal: at 225°C, roughly -25 Å is removed after 20 cycles, whereas at 300°C, roughly -42 Å is removed.

Answer:
300°C Process: Advantage: Faster, higher-throughput etch. Disadvantage : Risk of thermal damage to the underlying sensitive layer.

225°C Process: Advantage: Lower thermal budget, safer for the underlying layer. Disadvantage: Much slower etch rate, reducing throughput.

For a temperature-sensitive substrate, the 225°C process is preferable. The trade-off is accepting a slower etch rate to preserve the integrity of the underlying material.

Answer: The constant slope proves that the surface chemistry resets perfectly after every cycle. There is no "memory effect," residue accumulation, or surface roughening that inhibits (or accelerates) the reaction over time; the 20th cycle removes exactly as much material as the 1st cycle, confirming the robust, self-limiting nature of the ALE mechanism.

Answer: This enables the precise tuning of optical cavity lengths in ZnS-based micro-resonators or filters. By running an exact number of ALE cycles, the thickness of a ZnS waveguide layer can be reduced with sub-nanometer accuracy, allowing for post-fabrication trimming of the device's resonant wavelength to a specific target value without degrading surface smoothness.


FiG. 3. Surface roughness variation of AlGaN as a function of etch depth of the AlGaN film after (a) BT step, (b) RIE, (c) ALE using  $\mathrm{Cl}_2$  plasma, and (d) ALE using  $\mathrm{Cl}_2$  gas.

The line chart shows the relationship between etch depth and RMS roughness variation for different treatments, including RIE, ALE with Cl2 gas or Cl2 plasma, with the reference after BT.

| Etch Depth (nm) | RMS Roughness Variation (nm) RIE |RMS Roughness Variation (nm) Cl2 gas |RMS Roughness Variation (nm) Cl2 plasma |
|---|---|---|---|
| 0 | 0 |0 | 0 |
| 3 | 0.05|0.01|0|
| 5 | 0.15 |0.05|0|
| 7 | 0.2|0.05|0|
| 10 | - |-|-0.01|
| 15 | - |-|-|

Answer: RIE is increasing the roughness of the substrate, this is likely due to the sort of random distribution of ion influences on the substrate.

Answer: In the case of perfect ALE, all bumps and holes on a substrate are equally etched so the average roughness does not change.

Answer: The roughness changes with 0.15 nm.

Answer: The Cl2 plasma process seems to slightly decrease the roughness but remains constant, the Cl2 gas process increases the roughness on the other hand.

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/29/Atomic layer etching of AlGaN using Cl2 and Ar gas.pdf


FIG. 7.  $\mathrm{Al}_2\mathrm{O}_3$  film thickness vs cycle number of pALE for various process temperatures.

The figure compares Al₂O₃ film thickness across increasing pALE cycle numbers at four different temperatures. Higher temperatures (350–400°C) show significantly greater film removal per cycle, while lower temperatures (250–300°C) show slower and less pronounced thinning, indicating a clear temperature-dependent etch rate.

| Cycle number of pALE|250°C|300°C|350°C|400°C|
|---------------------|-----|-----|-----|-----|
|0|0|0|0|0|
|50|-5|-7|-9|-18|
|100|-7|-10|-12|-25|
|150|-8|-15|-18|-34|

Answer: The figure indicates that higher temperatures significantly accelerate Al₂O₃ removal during pALE, allowing for deeper etching in fewer cycles. Conversely, lower temperatures produce minimal thinning and offer finer control for delicate processing. Understanding this temperature-dependent response helps identify the optimal balance between etch rate, precision, and thermal stability for specific applications.

Answer: At higher temperatures such as 400°C, the film becomes much more negative (up to −34 nm), while at 250°C the thickness only decreases slightly (around −5 to −8 nm).

Answer: Yes

Answer: Higher thermal energy increases etch reactivity, Faster surface removal at elevated temperatures, Lower temperatures show slower, limited thinning

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/34/CF4 plasma-based atomic layer etching of Al2O3.pdf


Fig. 10. Cyclic number dependence of the blanket  $\mathrm{TiO_2}$  etched amount at different stage temperatures: (O) both steps had temperatures of  $60^{\circ}\mathrm{C}$ ,  $(\Delta)$  the  $\mathrm{C_4F_8}$  plasma had a temperature of  $20^{\circ}\mathrm{C}$  and the  $\mathrm{O_2}$  plasma a temperature of  $60^{\circ}\mathrm{C}$ ,  $(\square)$  and the  $\mathrm{C_4F_8}$  plasma had a temperature of  $60^{\circ}\mathrm{C}$  and the  $\mathrm{O_2}$  plasma a temperature of  $20^{\circ}\mathrm{C}$ . The plasma treatment time was  $30\mathrm{s}$  under all conditions.

The scatter plot shows the etched amount of TiO₂ against the number of cycles for different plasma conditions ("60 °C (C₄F₈ plasma), 60 °C (O₂ plasma)", "20 °C (C₄F₈ plasma), 60 °C (O₂ plasma)", "60 °C (C₄F₈ plasma), 20 °C (O₂ plasma)"). The condition "60 °C (C₄F₈ plasma), 60 °C (O₂ plasma)" results in the highest amount etched over cycles.

| Number of cycles | blencket TiO2 etched amount (nm) | Measurement |
|---|---|---|
| 0 | 0 | 60 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 1 | 0.79 | 60 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 4 | 2.94 | 60 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 8 | 5.58 | 60 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 12 | 8.68 | 60 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 0 | 0 | 20 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 1 | 0.96  | 20 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 3 | 2.19  | 20 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 5 | 3.86 | 20 °C (C₄F₈ plasma), 60 °C (O₂ plasma) |
| 0 | 0 | 60 °C (C₄F₈ plasma), 20 °C (O₂ plasma) |
| 1 | 0.6 | 60 °C (C₄F₈ plasma), 20 °C (O₂ plasma) |
| 3 | 1.03 | 60 °C (C₄F₈ plasma), 20 °C (O₂ plasma) |
| 6 | 1.54 | 60 °C (C₄F₈ plasma), 20 °C (O₂ plasma) |

Answer: O₂ plasma step is more temperature dependent. Lowering C₄F₈ plasma step temperature has little effect. Lowering the temperature for the O₂ plasma step significantly reduces the etch amount.

Answer: This suggests the step (the removal of the modified layer)  is thermally activated.

Answer: 60 °C C₄F₈ plasma, 20 °C O₂ plasma (smallest error bars and least fluctuation).

Answer: 60 °C C₄F₈ plasma, 60 °C O₂ plasma (largest error bars and highest variability).

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/36/Cyclic C4F8 and O2 plasma etching of TiO2.pdf


Fig. 14. Sidewall  $\mathrm{TiO_2}$  thicknesses of the trench pattern samples as deposited and after the cyclic processes.

The scatter plot shows the relationship between depth and sidewall TiO2 thickness as deposited and  for different plasma treatments (30s and 60s oxygen plasma treatment, after 8 cycles).

| Depth (nm) | Sidewall TiO2 thickness (nm) | Measurement |
|---|---|---|
| 681 |  9.04 | as TiO2 deposited |
| 1391 |  9.55 | as TiO2 deposited |
| 2091 |  9.78 | as TiO2 deposited |
| 2786 |  9.20 | as TiO2 deposited |
| 3496 | 9.69 | as TiO2 deposited |
| 51 |  8.88 | after 8 cycles, 30 s oxygen plasma |
| 695 |  5.35 | after 8 cycles, 30 s oxygen plasma |
| 1400 |  5.88 | after 8 cycles, 30 s oxygen plasma |
| 2095 |  6.33 | after 8 cycles, 30 s oxygen plasma |
| 2800 |  6.15 | after 8 cycles, 30 s oxygen plasma |
| 3496 |  5.59 | after 8 cycles, 30 s oxygen plasma |
| 27.8 |  5.88 | after 8 cycles, 60 s oxygen plasma |
| 690 |  4.47 | after 8 cycles, 60 s oxygen plasma |
| 1391 |  5.21 | after 8 cycles, 60 s oxygen plasma |
| 2100 |  4.74 | after 8 cycles, 60 s oxygen plasma |
| 2800 |  5.10 | after 8 cycles, 60 s oxygen plasma |
| 3496 |  5.82 | after 8 cycles, 60 s oxygen plasma |

Answer: Not uniform, as the top remains unetched while the deeper sections show significant material removal.

Answer: 60 s plasma treatment.

Answer: ~ 4.4 nm.

Answer: The protective layer is thicker at the top of the trench. This is demonstrated by the significantly smaller amount of etched TiO₂ at the trench opening compared to the deeper sidewalls under identical plasma conditions. The thicker protective layer at the top prevents  the underlying material from being etched for longer, until the layer is fully removed.


Fig. 3. (a) Depth dependence of the sidewall  $\mathrm{TiO_2}$  thicknesses before and after  $\mathrm{CF_4}$  plasma treatment for  $30~\mathrm{s}$  and (b) the sidewall etched amount.

The chart compares the sidewall TiO2 thickness in nm for pristine TiO2 and TiO2 after plasma etching as a function of depth. Sidewall thickness after etching is lower than before.

The scatter plot shows the sidewall TiO2 etched amount in nm as a function of depth. The etching at lower depths is higher.

| depth (nm) | Sidewall TiO2 thickness (nm): Pristine | Sidewall TiO2 thickness (nm): after RIE |
| --- | --- | --- |
| 20 | 9,83 | 4,35 |
| 39 | 9,79 | 7,76 |
| 60 | 9,65 | 7,81 |
| 80 | 9,97 | 8,08 |
| 101 | 9,60 | 8,13 |
| 119 | 9,83 | 8,13 |
| 139 | 9,83 | 8,13 |
| 160 | 9,56 | 8,27 |
| 179 | 9,60 | 8,45 |
| 199 | 9,65 | 8,41 |
| 219 | 9,65 | 8,31 |
| 240 | 9,79 | 8,36 |
| 257 | 9,60 | 8,45 |
| 280 | 9,79 | 8,50 |
| 299 | 9,47 | 8,04 |

| depth (nm) | sidewall TiO2 etched amount (nm) |
|---|---|
| 19 | 5,46 |
| 38 | 2,08 |
| 58 | 1,92 |
| 78 | 1,92 |
| 97 | 1,43 |
| 119 | 1,62 |
| 139 | 1,57 |
| 159 | 1,41 |
| 178 | 1,11 |
| 200 | 1,22 |
| 218 | 1,43 |
| 239 | 1,43 |
| 259 | 1,22 |
| 280 | 1,27 |
| 300 | 1,41 |

Answer: It was uniform.

Answer: Tapered (because the etching is stronger at the top opening than deep inside).

Answer: Top 20 nm.

Answer: The etching gets weaker. The etched amount drops from ~5.5 nm at the top to ~1.5 nm at the bottom. This happens because plasma is mostly being consumed at the top and can't reach the bottom effectively.


FIG.4. (a) Plted etch depth vs ALE cycle. Dashed line marks the transition between AlGaN and GaN layers. AFM scans of various steps (b) 25, (c) 100, (d) 300, and (e) 400 cycles.

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/38/High synergy atomic layer etching of AlGaNGaN.pdf


FIG.5. Atomic concentrations of Ti, N, O, F, and C vs Ar milling time and estimated depth for (a) original and (b) ALE-treated TiN thin films. The dashed lines are guides to the eye.

Depth-profiling XPS data for the original TiN film showing atomic concentrations versus Ar sputtering time and estimated depth. At the surface, oxygen (~16%) and carbon (~12%) are elevated due to native oxide and adventitious carbon. After ~60 s of sputtering (~2 nm depth), concentrations plateau to bulk values: Ti (~49%), N (~42%), O (~6%), C (~2%), and F (~1%).

Depth-profiling XPS data for the ALE-treated TiN film. The surface shows significantly lower oxygen (~8%) compared to the original film, while fluorine is slightly elevated (~6.5%). Bulk composition remains essentially unchanged from the original film, confirming that ALE affects only the top few nanometers.

| Sputtering time, s | Estimated depth, nm | Ti (%) | N (%) | F (%) | O (%) | C (%) |
|---|---|---|---|---|---|---|
| 0 | 0 | 32 | 38 | 3 | 15 | 12 |
| 60 | 2 | 46 | 45 | 3 | 5 | 2 |
| 120 | 3 | 48 | 43 | 2 | 6 | 2 |
| 180 | 5 | 48 | 43 | 2 | 6 | 2 |
| 240 | 7 | 48 | 42 | 2 | 6 | 2 |
| 300 | 8 | 50 | 42 | 2 | 6 | 2 |
| 360 | 10 | 48 | 41 | 2 | 6 | 2 |

| Sputtering time, s | Estimated depth, nm | Ti (%) | N (%) | F (%) | O (%) | C (%) |
|---|---|---|---|---|---|---|
| 0 | 0 | 34 | 41 | 6 | 7 | 12 |
| 60 | 2 | 47 | 46 | 2 | 5 | 2 |
| 120 | 3 | 49 | 44 | 2 | 5 | 2 |
| 180 | 5 | 49 | 43 | 2 | 5 | 2 |
| 240 | 7 | 50 | 43 | 1 | 6 | 2 |
| 300 | 8 | 50 | 43 | 1 | 6 | 2 |
| 360 | 10 | 49 | 42 | 1 | 6 | 2 |

Answer: The compositional gradient in the first 2 nm reflects the presence of a modified surface layer on the TiN film. At the surface, native oxide formation from atmospheric exposure causes elevated oxygen content, while adventitious carbon contamination adds to the carbon signal. As the Ar ion beam sputters through this surface layer, it reaches the bulk TiN film where the composition stabilizes at the stoichiometric values determined by the ALD growth process. This depth-dependent behavior confirms that surface contamination and oxidation are confined to a thin surface region.

Answer: Ti, N, F, O, C

Answer: The surface oxygen decreases from approximately 16% in the original film to about 8% in the ALE-treated film, representing a 49% reduction.

Answer: No, the ALE process does not alter the bulk composition. Both the original and ALE-treated films show nearly identical bulk atomic concentrations after sputtering beyond 2 nm depth: approximately 49% Ti, 42% N, 6% O, 2% C, and 1% F. This indicates that the plasma-thermal ALE process selectively modifies only the surface region while preserving the intrinsic film properties. This characteristic is important for applications where maintaining bulk superconducting or electronic properties is essential.

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/40/Isotropic plasma-thermal atomic layer etching of.pdf


FIG. 2. (a) Etch rate of  $\mathrm{TiO}_2$  (red circles) and TiN (blue squares) vs the  $\mathrm{SF}_6{:}\mathrm{H}_2$  flow rate ratio. The green shaded area represents the flow rate ratios for which selective etching of  $\mathrm{TiO}_2$  over TiN was achieved. The vertical dashed black line at a ratio of 0.2 represents the ratio used in the ALE experiments. (b) TiN thickness change vs number of cycles with exposure only to  $\mathrm{O}_2$  gas (red triangles), in situ HF (green squares), full ALE process at  $200^{\circ}\mathrm{C}$  (purple circles), and  $300^{\circ}\mathrm{C}$  (blue diamonds). The dashed lines are guides to the eye.

The etch rate of TiO₂ and TiN as a function of SF₆:H₂ flow rate ratio.

The thickness change of materials with different treatments as a function of the number of cycles

| SF₆:H₂ flow rate ratio | TiO₂ (Å s⁻¹) | TiN (Å s⁻¹) |
|---|---|---|
| 0 | 0.00 | -0.05 |
| 0.05 | 0.00 | -0.05 |
| 0.10 | 0.18 | -0.03 |
| 0.15 | 0.45 | -0.02 |
| 0.20 | 0.58 | 0.00 |
| 0.25 | 0.65 | 0.16 |
| 0.30 | 0.73 | 0.33 |

| Number of cycles | O₂ gas (nm) | In-situ HF (nm) | ALE 200°C (nm) | ALE 300°C (nm) |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 20 | 0 | 0 | -5 | -6.5 |
| 40 | 0 | 0 | -10 | -13 |
| 60 | 0 | 0 | -15 | -19 |
| 80 | 0 | -1 | -20 | -26 |
| 100 | 0 | -1 | -24 | -33 |

Answer: A ratio of 0.2 was selected for the ALE experiments, as indicated by the vertical dashed line in the figure. This ratio was chosen because it lies at the upper boundary of the selective etching window (0.1 to 0.2) where TiO2 is etched while TiN remains unetched. At this ratio, the SF6/H2 plasma produces sufficient in-situ HF to etch the oxide layer, but the fluorine radical concentration remains low enough to avoid spontaneous etching of TiN. This maximizes the etch rate of the modified layer while maintaining selectivity.

Answer: When the SF6:H2 ratio exceeds 0.2, the concentration of fluorine radicals in the plasma becomes sufficient to spontaneously etch TiN. At lower ratios, hydrogen radicals combine with fluorine radicals to form HF molecules, which do not etch TiN due to its 3+ oxidation state. However, at higher ratios, excess fluorine radicals are available that can directly attack the TiN surface, leading to uncontrolled etching of both TiO2 and TiN and loss of selectivity.

Answer: The green shaded region represents the range of SF6:H2 flow rate ratios (0.1 to 0.2) where selective etching of TiO2 over TiN is achieved.

Answer: The etch rate at 300°C (3.2 Å/cycle) is approximately 33% higher than at 200°C (2.4 Å/cycle).


FIG. 7. Resistivity vs temperature for an original  $60~\mathsf{nm}$  TiN film (blue squares), an ALE-treated film of  $50~\mathsf{nm}$  thickness (red circles), and a  $50~\mathsf{nm}$  ALD TiN film (black diamonds) for comparison. The difference in  $T_{c}$  between the  $50~\mathsf{nm}$  ALD film and the ALE-treated  $50~\mathsf{nm}$  film is negligible. The dashed lines are guides to the eye.

Resistivity versus temperature (1.7 to 6 K) showing superconducting transitions for three TiN films. The 60 nm ALD film (blue) has Tc ≈ 3.22 K and resistivity ~222 μΩcm. The ALE-treated 50 nm film (red) and 50 nm ALD reference (black) show nearly identical Tc ≈ 3.1 K, demonstrating that ALE does not degrade superconducting properties beyond the expected thickness dependence.

| Temperature, K | 60 nm ALD (μΩcm) | 50 nm after ALE (μΩcm) | 50 nm ALD (μΩcm) |
|---|---|---|---|
| 2.0 | 0 | 0 | 0 |
| 2.5 | 0 | 0 | 0 |
| 2.9 | 0 | 0 | 0 |
| 3.0 | 0 | 0 | 85 |
| 3.05 | 0 | 5 | 110 |
| 3.1 | 15 | 150 | 150 |
| 3.15 | 65 | 165 | 175 |
| 3.2 | 150 | 185 | 190 |
| 3.3 | 185 | 195 | 210 |
| 3.5 | 210 | 200 | 220 |
| 4.0 | 215 | 202 | 225 |
| 5.0 | 218 | 203 | 227 |
| 6.0 | 220 | 205 | 228 |

Answer: The ALE-treated 50 nm film has Tc ≈ 3.13 K, which is nearly identical to the 50 nm ALD reference film at Tc ≈ 3.11 K. This negligible difference demonstrates that the ALE process does not introduce damage that would degrade superconducting properties. The small Tc reduction from the 60 nm film (Tc ≈ 3.22 K) is consistent with expected thickness-dependent behavior.

Answer: The figure demonstrates that the plasma-thermal ALE process is low-damage. Conventional etching methods often degrade superconducting properties through subsurface damage or contamination. Here, the ALE-treated film maintains the same Tc as an as-deposited film of equal thickness, confirming that ALE removes material without harming the remaining film quality.

Answer: The ALE-treated film has lower resistivity (~201 μΩcm) compared to the 50 nm ALD film (~227 μΩcm) due to reduced native oxide after etching. The authors hypothesize that fluorine incorporation during ALE may also act as a diffusion barrier, slowing reoxidation when exposed to atmosphere.

Answer: Four-point resistivity measurements using a Quantum Design DynaCool Physical Property Measurement System (PPMS) from 6 K down to 1.7 K.


Figure 2. (a) Film thickness versus number of HF and  $\mathrm{Sn(acac)}_2$  reaction cycles at  $200^{\circ}\mathrm{C}$  for a variety of materials. (b) Film thickness versus number of HF and  $\mathrm{Sn(acac)}_2$  reaction cycles at  $200^{\circ}\mathrm{C}$  for  $\mathrm{Al}_2\mathrm{O}_3$ ,  $\mathrm{HfO}_2$ , and  $\mathrm{ZrO}_2$  showing etch rates.

The figure shows the film thickness of various materials (TiN, SiO₂, Si₃N₄, HfO₂, ZrO₂, Al₂O₃) at 200°C when Sn(acac)2 is used for etching.

The figure illustrates the atomic layer deposition (ALE) rates when Sn(acac)2 is used for etching for HfO₂, ZrO₂, and Al₂O₃ at 200°C over cycles.

| Film Thickness (Å) | TiN | SiO₂ | Si₃N₄ | HfO₂ | ZrO₂ | Al₂O₃ |
|-------------------|-----|------|-------|------|------|-------|
| 0                | 70  | 50   | 40    | 30   | 0    | 30    |
| 1-30-1-30         | 68  | 48   | 38    | 32   | 0    | 28    |
| 200°C             | 66  | 46   | 36    | 30   | 0    | 26    |

| Number of Cycles | HfO₂ ALE: 0.06 Å/cycle | ZrO₂ ALE: 0.14 Å/cycle | Al₂O₃ ALE: 0.23 Å/cycle |
|------------------|------------------------|------------------------|-------------------------|
| 0                | 50                     | 50                     | 50                      |
| 100              | 45                     | 45                     | 40                      |
| 200              | 40                     | 40                     | 25                      |
| 400              | 35                     | 35                     | 0                       |

Answer: Sequential exposures of HF and acetylacetone (acacH, Sigma-Aldrich >99%) did not lead to the etching of Al2O3 at 200 °C. Without the metal acetylacetonate precursor, acetylacetone alone does not yield thermal ALE.

Answer:
From the film thicknesses after 50, 100, 200, and 400 ALE cycles using sequential HF and Sn(acac)2 exposures at 200 °C, Al2O3, ZrO2, and HfO2 films were etched linearly versus the number of ALE cycles. In contrast, there were no measurable
thickness changes for the SiO2, Si3N4, and TiN films.

Answer: The slopes from the linear least-squares fittings of the data in image b yielded etch rates of 0.23 Å/cycle, 0.14 Å/cycle, and 0.06 Å/cycle for the Al2O3, ZrO2, and HfO2 films, respectively

Answer: Additional control experiments were performed on the Al2O3, ZrO2, and HfO2 films to determine if both HF and Sn(acac)2 were necessary for the thermal ALE. Experiments using 200 cycles of HF exposures observed negligible thickness changes for the Al2O3, ZrO2, and HfO2 films.

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/42/Selectivity in Thermal Atomic Layer Etching.pdf


Figure 3. (a) Film thickness versus number of HF and TMA reaction cycles at  $300^{\circ}\mathrm{C}$  for a variety of materials. (b) Film thickness versus number of HF and TMA reaction cycles at  $300^{\circ}\mathrm{C}$  for  $\mathrm{Al}_2\mathrm{O}_3$ ,  $\mathrm{HfO}_2$ , and  $\mathrm{ZrO}_2$  showing etch rates.

The figure shows the film thickness of various materials (TiN, ZrO₂, SiO₂, Si₃N₄, HfO₂, Al₂O₃) at 300°C using TMA and HF for ALE etching.

The figure illustrates the atomic layer etching (ALE) rates of ZrO₂, HfO₂, and Al₂O₃ at 300°C using TMA and HF

| Number of Cycles | TiN (Å) | SiO₂ (Å) | Al₂O₃ (Å) | Si₃N₄ (Å) | HfO₂ (Å) | ZrO₂ (Å) |
|-------------------|---------|----------|-----------|-----------|----------|----------|
| 0                | 65      | 50       | 45        | 45        | 55       | 50       |
| 50               | 65      | 49       | 30        | 44        | 50       | 49       |
| 100              | 65      | 48       | 15        | 43        | 48       | 48       |
| 150              | 65      | 47       | 5         | 42        | 40       | 47       |
| 200              | 65      | 46       | 0         | 42        | 38       | 46       |

| Number of Cycles | Al₂O₃ (Å) | HfO₂ (Å) | ZrO₂ (Å) |
|-------------------|-----------|----------|----------|
| 0                | 45        | 55       | 50       |
| 50               | 20        | 50       | 49       |
| 100              | 0        | 48       | 48       |
| 150              | -         | 40       | 47       |
| 200              | 0         | 38       | 47       |

Answer: All the ALE processes on different materials with HF and TMA are thermal processes conducted at 300 °C.

Answer: The film thicknesses after 25, 50, 100, and 200 ALE cycles using sequential HF and TMA exposures at 300 °C. The Al2O3 and HfO2 films were etched linearly versus the number of ALE cycles. There were negligible thickness changes during 200 ALE cycles for the ZrO2, SiO2, Si3N4, and TiN films.

Answer: No

Answer:
Etch rates of 0.45 Å/cycle and 0.10 Å/cycle were measured for the Al2O3 and HfO2 films, respectively. The etch rate of Al2O3 is in agreement with the value measured earlier by quartz crystal microbalance
(QCM) and SE experiments.


Figure 4. (a) Film thickness versus number of HF and DMAC reaction cycles at  $250^{\circ}\mathrm{C}$  for a variety of materials. (b) Film thickness versus number of HF and DMAC reaction cycles at  $250^{\circ}\mathrm{C}$  for  $\mathrm{Al}_2\mathrm{O}_3$ ,  $\mathrm{HfO}_2$ , and  $\mathrm{ZrO}_2$  showing etch rates.

The figure shows the film thickness of various materials (TiN, SiO₂, Si₃N₄, ZrO₂, HfO₂, Al₂O₃) at 250°C for various DMAC and HF etch cycles.

The figure illustrates the atomic layer etching (ALE)  etch rates of HfO₂, Al₂O₃, and ZrO₂ at 250°C

| Film Thickness (Å) | TiN | SiO₂ | Si₃N₄ | ZrO₂ | HfO₂ | Al₂O₃ |
|-------------------|-----|------|-------|------|------|-------|
| 0                | 65  | 50   | 40    | 40   | 50   | 45    |
| 25               | 65  | 50   | 40    | 30   | 40   | 40    |
| 50               | 65  | 50   | 40    | 20   | 30   | 35    |
| 100              | 65  | 50   | 40    | 0    | 0    | 20     |

| Film Thickness (Å) | HfO₂ ALE: 0.77 Å/cycle | Al₂O₃ ALE: 0.32 Å/cycle | ZrO₂ ALE: 0.96 Å/cycle |
|-------------------|-------------------------|-------------------------|-------------------------|
| 0                 | 50                      | 45                      | 50                      |
| 25                | 40                      | 40                      | 35                      |
| 50                |20                      | 35                      | 10                      |
| 100               | 0                       | 20                       | 0                       |

Answer:
The film thicknesses after 10, 25, 50, and 100 ALE cycles using sequential HF and DMAC exposures at 250 °C show linear etching
 for the ZrO2, HfO2, and Al2O3 films. While no measurable thickness changes were  observed for the SiO2, Si3N4, and TiN films

Answer: 250 °C

Answer:
1. Al2O3
, 2. HfO2
, 3. ZrO2

Answer: Etch rates of 0.96 Å/cycle, 0.77 Å/cycle, and 0.32 Å/cycle were determined for the ZrO2, HfO2, and Al2O3 films, respectively. Al2O3 etched at the slowest rate compared to the other two materials.


Figure 5. (a) Film thickness versus number of HF and  $\mathrm{SiCl}_4$  reaction cycles at  $350^{\circ}\mathrm{C}$  for a variety of materials. (b) Film thickness versus number of HF and  $\mathrm{SiCl}_4$  reaction cycles at  $350^{\circ}\mathrm{C}$  for  $\mathrm{Al}_2\mathrm{O}_3$ ,  $\mathrm{HfO}_2$ , and  $\mathrm{ZrO}_2$  showing etch rates.

The figure shows the film thickness of various materials (TiN, Al₂O₃, SiO₂, Si₃N₄, HfO₂, ZrO₂) at 350°C using SiCl₄ as function of number of cycles

The figure compares the film thickness of Al₂O₃, HfO₂, and ZrO₂ with different atomic layer deposition (ALE) rates at 350°C using SiCl₄.

| Number of Cycles | TiN (Å) | SiO₂ (Å) | Al₂O₃ (Å) | Si₃N₄ (Å) | HfO₂ (Å) | ZrO₂ (Å) |
|-------------------|---------|----------|-----------|-----------|----------|----------|
| 0                | 65      | 50       | 45        | 45        | 55       | 50       |
| 100              | 65      | 48       | 44        | 44        | 50       | 35       |
| 200              | 65      | 47       | 44        | 43        | 48       | 20       |
| 300              | 65      | 46       | 43        | 42        | 46       | 10       |
| 400              | 65      | 45       | 43        | 42        | 44       | 5        |

| Number of Cycles | Al₂O₃ (Å) | HfO₂ (Å) | ZrO₂ (Å) |
|-------------------|-----------|----------|----------|
| 0                | 45        | 55       | 50       |
| 100              | 45        | 50       | 35       |
| 200              | 45        | 48       | 20       |
| 300              | 45        | 46       | 10       |
| 400              | 45        | 44       | 5        |

Answer: Yes

Answer: The film thicknesses after 50, 100, 200, and 400 ALE cycles using sequential HF and SiCl4 exposures at 350 °C. The ZrO2 and HfO2 films were etched linearly versus the number of ALE cycles. In contrast, there were no measurable thickness changes during 400 ALE cycles for the Al2O3, SiO2, Si3N4, and TiN films

Answer:
Al₂O₃ ALE: 0 Å/cycle
, HfO₂ ALE: 0.05 Å/cycle
, ZrO₂ ALE: 0.14 Å/cycle

Answer: Image b shows only those materials which get etched with HF anf SiCl4 from the group shown in image a


Figure 6. (a) Etch rates for  $\mathrm{ZrO}_2$  and  $\mathrm{HfO}_2$  versus  $\mathrm{SiCl}_4$  exposure time with constant HF exposure time of  $1.0~\mathrm{s}$ . (b) Etch rates for  $\mathrm{ZrO}_2$  and  $\mathrm{HfO}_2$  versus HF exposure time with constant  $\mathrm{SiCl}_4$  exposure time of  $2.0~\mathrm{s}$ .

The etch rate of ZrO₂ and HfO2 increases slightly with increasing SiCl₄ exposure time at 350°C.

The etch rate of ZrO₂ increases significantly while HfO2 only slightly with increasing HF exposure time at 350°C.

| SiCl₄ Exposure Time (s) | ZrO₂ Etch Rate (Å/cycle) | HfO₂ Etch Rate (Å/cycle) |
|--------------------------|---------------------------|---------------------------|
| 0.0                      | 0.00                     | 0.00                     |
| 0.5                      | 0.13                     | 0.05                     |
| 1.0                      | 0.14                     | 0.06                     |
| 1.5                      | 0.14                     | 0.06                     |
| 2.0                      | 0.14                     | 0.06                     |

| HF Exposure Time (s)     | ZrO₂ Etch Rate (Å/cycle) | HfO₂ Etch Rate (Å/cycle) |
|--------------------------|---------------------------|---------------------------|
| 0.0                      | 0.00                     | 0.00                     |
| 0.5                      | 0.07                     | 0.03                     |
| 1.0                      | 0.12                     | 0.05                     |
| 1.5                      | 0.15                     | 0.06                     |
| 2.0                      | 0.17                     |  0.06                     |

Answer:
The etch rates for both ZrO2 and HfO2 are self-limiting versus SiCl4 exposure. The etch rates are constant at progressively larger SiCl4 exposure times. The etch rates at each SiCl4 exposure time were determined using at least 3−4 measured film
thicknesses after different numbers of ALE cycles.

Answer:
1. Saturated etch rate for ZrO2 = 0.14 Å/cycle
, 2. Saturated etch rate for HfO2 = 0.06 Å/cycle
, at HF exposure of 1 s and SiCl4 exposure of 1s

Answer: Yes

Answer: The etch rate for ZrO2 begins to level off at higher HF exposures. The slight increases at larger HF exposures for ZrO2 can be attributed to the difficulty purging HF from the reactor after longer HF exposures. Residual HF remaining in the reactor will lead to chemical vapor etching (CVE) during  the SiCl4 exposure. Similar influences of CVE on thermal ALE have been observed earlier after longer HF exposures.


Figure 8. Thermochemical calculations for the ligand-exchange reactions between  $\mathrm{SiCl_4}$  and  $\mathrm{AlF}_3,$ $\mathrm{HfF_4}$  and  $\mathrm{ZrF_4}$  Ligand exchange is assumed to proceed completely to  $\mathrm{SiF_4}$  and the corresponding metal chloride.

The chart shows the change in Gibbs free energy (ΔG) for three different chemical reactions as a function of temperature.

| Temperature (°C) | ΔG for SiCl₄ + AlF₃ / SiF₄ + AlCl₃ (kcal/mol) | ΔG for SiCl₄ + HfF₄ / SiF₄ + HfCl₄ (kcal/mol) | ΔG for SiCl₄ + ZrF₄ / SiF₄ + ZrCl₄ (kcal/mol) |
|------------------|-----------------------------------------------|-----------------------------------------------|-----------------------------------------------|
| 0                | 45                                           | 8                                            | 5                                            |
| 100              | 40                                           | 5                                            | 2                                            |
| 200              | 35                                           | 2                                            | 0                                            |
| 300              | 30                                           | -2                                           | -5                                           |
| 400              | 25                                           | -6                                           | -10                                          |
| 500              | 20                                           | -10                                          | -15                                          |

Answer: The thermochemistry of the ligand exchange was determined assuming complete ligand exchange to form SiF4 and the fully chlorinated metal in the original metal fluoride.

Answer:
The thermochemical results for the ligand exchange between SiCl4 and AlF3, ZrF4 and HfF4 can be seen in the image. These
results reveal that the ligand exchange between SiCl4 and ZrF4 or HfF4 is thermochemically favorable at >200 °C. In contrast,
the ligand exchange between SiCl4 and AlF3 is not thermchemically favorable at any temperature.

Answer: ZrF4 and HfF4 can both undergo ligand exchange with SiCl4 at 350 °C because these reactions are spontaneous with ΔG ≈ −10 kcal/mol. On the other hand, Al2O3 can not be etched at 350 °C because the ligand exchange between SiCl4 and AlF3 is not spontaneous with ΔG ≈ + 26 kcal/mol.

Answer: No


Fig. 3. Mass change per cycle as a function of (a)  $\mathrm{NF_3}$  remote plasma time or (b) TMA pulse time at  $250^{\circ}\mathrm{C}$ . The TMA pulse time was  $3\mathrm{~s~}$  in (a), and the  $\mathrm{NF_3}$  remote plasma time was  $4\mathrm{~s~}$  in (b).

This two-panel figure shows Mass Change Per Cycle (MCPC) (ng/(cm²·cycle)) data for the Atomic Layer Etching (ALE) of Al₂O₃, MCPC varies the NF₃ plasma time (with fixed 3s TMA)

Mass Change Per Cycle (MCPC) (ng/(cm²·cycle)) varies the TMA pulse time (with fixed 4s NF₃). Both plots show the mass loss saturating, proving each half-reaction is self-limiting.

| NF₃ Remote Plasma Time (s) | MCPC (ng/(cm²·cycle)) | Symbol    |
|---|---|---|
| 0 | 0 |NF₃ remote plasma (square) |
| 1.5 | -25 | NF₃ remote plasma (square) |
| 2.0 | -60 | NF₃ remote plasma (square) |
| 3.0 | -70 | NF₃ remote plasma (square) |
| 4.0 | -60 | NF₃ remote plasma (square) |
| 4.0 | -2  | NF₃ gas (circle) |

| TMA Pulse Time (s) | MCPC (ng/(cm²·cycle)) |
|---|---|
| 0.0 | 0 |
| 0.5 | -25 |
| 1.5 | -45 |
| 3.0 | -55 |
| 4.5 | -58 |

Answer: The curve would still rise but plateau at a lower maximum mass loss. With an undersaturated TMA dose, not all the fluorinated layer is removed each cycle. The process would not be fully self-limiting or stable, as the etch depth would depend on the incomplete removal step, leading to poor control and possible residue accumulation.

Answer: The grey region represents an incubation or threshold period. During these short exposures, the incoming fluorine radical flux is too low to fully fluorinate the Al₂O₃ surface to the depth needed for the subsequent ligand-exchange reaction with TMA. Because a sufficient coverage of surface fluoride (AlFₓ) species has not yet formed, TMA cannot remove material, resulting in nearly zero MCPC.

Answer: 60 ng/(cm²·cycle corresponds to roughly 2.0 Å/cycle

Answer:
NF₃ Remote Plasma Exposure (4 s)

, Purge

, TMA Exposure (3 s)

, Purge

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/43/Surface reaction during thermal atomic layer etching of aluminum oxide.pdf


Figure 10. X-ray reflectivity and spectroscopic ellipsometry measurements of TiN film thickness versus number of  $\mathrm{H}_2\mathrm{O}_2$  and HF reaction cycles at  $250^{\circ}\mathrm{C}$ .

The line chart shows the film thickness in Ångströms (Å) over the number of cycles for XRR and SE methods at 250°C using H₂O₂ and HF

| Number of Cycles | XRR (Film Thickness, Å) | SE (Film Thickness, Å) |
|---|---|---|
| 0 | 63 | 73 |
| 50 | 58 | 66 |
| 100 | 51 | 61 |
| 200 | 39 | 46 |
| 400 | 6 | 12 |

Answer: Using both X-ray reflectivity and spectroscopic ellipsometry provides independent verification of the thickness measurements. XRR also yields additional information about film density and surface roughness. The close agreement between techniques (0.14 vs 0.15 Å/cycle) confirms measurement reliability.

Answer: The H₂O₂/HF etch rate (0.15 Å/cycle) is slightly lower than the O₃/HF etch rate (0.20 Å/cycle) at 250°C, reflecting O₃'s stronger oxidizing power.

Answer: Linearity confirms that each ALE cycle removes a constant, reproducible amount of material, demonstrating true self-limiting behavior rather than uncontrolled continuous etching.

Answer: SE measured ~73 Å initial thickness; XRR measured ~63 Å. This offset is maintained throughout but both yield the same etch rate slope.

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/45/Thermal Atomic Layer Etching of Titanium Nitride.pdf


Figure 3. X-ray reflectivity and spectroscopic ellipsometry measurements of TiN film thickness versus number of  $\mathrm{O}_3$  and HF reaction cycles at  $250^{\circ}\mathrm{C}$ .

The line chart illustrates the decrease in film thickness over cycles for TiN ALE at 250°C using O₃ & HF

| Number of Cycles | SE (Film Thickness, Å) | XRR (Film Thickness, Å) |
|---|---|---|
| 0 | 73 | 63 |
| 25 | 68 | 61 |
| 50 | 63 | 57 |
| 100 | 52 | 47 |
| 150 | 45 | 26 |
| 200 | 34 | 27 |
| 300 | 16 | 6 |

Answer: SE gives 0.19 Å/cycle and XRR gives 0.20 Å/cycle—essentially identical within experimental uncertainty, validating both measurement approaches.

Answer: The offset (~10 Å difference in initial thickness) arises from different optical/structural models used by each technique. SE uses a Lorentz optical model while XRR measures electron density contrast. Despite this absolute offset, both yield the same etch rate slope.

Answer: The optimized sequence was 3-30-1-30: 3 s O₃ exposure, 30 s N₂ purge, 1 s HF exposure, 30 s N₂ purge.

Answer: Approximately 60 Å of TiN is removed after 300 cycles, reducing the film from ~70 Å to ~10 Å (based on XRR data).


Figure 5. Film thickness versus number of  $\mathrm{O}_3$  and HF reaction cycles at  $250^{\circ}\mathrm{C}$  for  $\mathrm{Al}_2\mathrm{O}_3$ ,  $\mathrm{HfO}_2$ ,  $\mathrm{ZrO}_2$ ,  $\mathrm{SiO}_2$ ,  $\mathrm{Si}_3\mathrm{N}_4$ , and TiN.

The figure demonstrates selective TiN etching using O₃/HF at 250°C. TiN (gray diamonds) shows linear thickness reduction while Al₂O₃, HfO₂, ZrO₂, SiO₂, and Si₃N₄ remain essentially unchanged over 400 cycles. This confirms high selectivity of the ALE process for TiN over common dielectrics and barrier materials.

| Number of Cycles | TiN | Al₂O₃ | Si₃N₄ | SiO₂ | ZrO₂ | HfO₂ |
|-----------------|-----|-------|------|-----|------|------|
| 0              | 75  | 40    | 40   | 55  | 55   | 55   |
| 100            | 40  | 40    | 40   | 55  | 55   | 55   |
| 200            | 20  | 40    | 40   | 55  | 55   | 55   |
| 300            | 10  | 40    | 40   | 55  | 55   | 55   |
| 400            | 5   | 40    | 40   | 55  | 55   | 55   |

Answer: Etched: TiN only. Unchanged: Al₂O₃, HfO₂, ZrO₂, SiO₂, and Si₃N₄.

Answer: These metal oxides form stable, non-volatile fluorides (AlF₃, HfF₄, ZrF₄) when exposed to HF. Unlike TiF₄ which sublimes at 284°C, these fluorides remain on the surface and cannot be removed thermally under ALE conditions.

Answer: Dry HF (without H₂O present) cannot etch SiO₂. The HF/SiO₂ reaction requires water as a catalyst for effective etching.

Answer: Selective etching allows precise removal of one material while preserving adjacent structures. For TiN, selective ALE enables controlled thinning or removal without damaging surrounding dielectrics like HfO₂ gate oxides or SiO₂ interlayer dielectrics.


FIG. 1. Amount of silicon etched as a function of cycle number. For these results, one cycle corresponds to 2255  $\mathrm{Cl}_2$  impacts and  $1000\mathrm{Ar}^+$  impacts. Each line corresponds to results for a different  $\mathrm{Ar}^+$  ion energy: blue (lowest curve)  $-40\mathrm{eV}$ , green (second lowest curve)  $-60\mathrm{eV}$ , red (second highest curve)  $-80\mathrm{eV}$ , and black (highest curve)  $-100\mathrm{eV}$ . The vertical dashed lines separate the  $\mathrm{Cl}_2$  and  $\mathrm{Ar}^+$  portions of the ALE cycles.

The figure shows silicon ALE using cyclic Cl₂ adsorption and Ar⁺ bombardment, producing a characteristic stair-step etch profile. Material removal occurs only during the ion step, confirming the self-limiting ALE sequence. The etch per cycle increases with ion energy, from ~3 Å at 40 eV to ~11 Å at 100 eV after 8 cycles, indicating that higher energies may exceed the monolayer-limited regime.

| Cycle number | Si etched (Å) | Ion energy (eV) |
|-------------:|--------------:|---------------:|
| 1 | 0.3 | 40  |
| 1 | 0.6 | 60  |
| 1 | 1.0 | 80  |
| 1 | 1.4 | 100 |
| 2 | 0.5 | 40  |
| 2 | 1.0 | 60  |
| 2 | 1.7 | 80  |
| 2 | 2.6 | 100 |
| 3 | 0.8 | 40  |
| 3 | 1.6 | 60  |
| 3 | 2.5 | 80  |
| 3 | 3.6 | 100 |
| 4 | 1.2 | 40  |
| 4 | 2.2 | 60  |
| 4 | 3.5 | 80  |
| 4 | 5.0 | 100 |
| 5 | 1.7 | 40  |
| 5 | 3.0 | 60  |
| 5 | 4.8 | 80  |
| 5 | 6.7 | 100 |
| 6 | 2.1 | 40  |
| 6 | 3.9 | 60  |
| 6 | 5.8 | 80  |
| 6 | 8.0 | 100 |
| 7 | 2.6 | 40  |
| 7 | 4.5 | 60  |
| 7 | 6.8 | 80  |
| 7 | 9.2 | 100 |
| 8 | 3.1 | 40  |
| 8 | 5.2 | 60  |
| 8 | 7.7 | 80  |
| 8 | 10.8| 100 |

Answer: Spontaneous Chemical Etching. Ideally, Cl_2 should only adsorb. If the line rises, it means the chlorine is etching the silicon spontaneously without ion activation, destroying the precision of the ALE process.

Answer: 40 eV (Blue). Although slower, the lower energy ensures the etch is strictly limited to the surface surface. The 100 eV ions would cause sidewall sputtering or corner rounding, ruining the shape of the delicate nano-fin.

Answer: 100 eV (Black). It removes >1.3 Å per cycle (steeper steps). This poses a risk of sub-surface damage or amorphization, as the high-energy ions penetrate deeper than the chemically modified surface layer.

Answer: The line would stay flat. Without the kinetic energy of the Ar^+ ions to knock off the chlorinated layer, no material would be removed, resulting in a 'missed step' in the staircase pattern.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/15/Molecular dynamics study of silicon atomic layer etching by chlorine gas and argon ions.pdf


FIG. 2. Chlorine uptake (in units of equivalent monolayers) as a function of cycle number for the cycles described in Fig. 1. Each line corresponds to results for a different  $\mathrm{Ar}^+$  ion energy: blue (lowest curve)  $-40\mathrm{eV}$ , green (second lowest curve)  $-60\mathrm{eV}$ , red (second highest curve)  $-80\mathrm{eV}$ , and black (highest curve)  $-100\mathrm{eV}$ . The vertical dashed lines separate the  $\mathrm{CI}_2$  and  $\mathsf{Ar}^+$  portions of the ALE cycles.

This graph illustrates the cyclic nature of the Atomic Layer Etching (ALE) process over 8 cycles. The "sawtooth" pattern represents the alternating addition of Chlorine (rising slope) and removal of material via Argon ion bombardment (falling slope). The distinct colored lines show that higher ion energies (e.g., 100 eV) result in deeper removal of the chlorinated layer compared to lower energies (e.g., 40 eV).

| Cycle number | Cu uptake (ML) | Ion energy (eV) |
|--------------|---------------:|-----------------:|
| 1            | ~1.39          | 40               |
| 1            | ~1.05          | 60               |
| 1            | ~1.17          | 80               |
| 1            | ~1.04         | 100              |
| 2            | ~1.50          | 40               |
| 2            | ~1.45          | 60               |
| 2            | ~1.40          | 80               |
| 2            | ~1.35          | 100              |
| 3            | ~1.80          | 40               |
| 3            | ~1.70          | 60               |
| 3            | ~1.60          | 80               |
| 3            | ~1.50          | 100              |
| 4            | ~1.95          | 40               |
| 4            | ~1.85          | 60               |
| 4            | ~1.75          | 80               |
| 4            | ~1.60          | 100              |
| 5            | ~2.00          | 40               |
| 5            | ~1.95          | 60               |
| 5            | ~1.85          | 80               |
| 5            | ~1.55          | 100              |
| 6            | ~2.05          | 40               |
| 6            | ~2.00          | 60               |
| 6            | ~1.95          | 80               |
| 6            | ~1.60          | 100              |
| 7            | ~2.20          | 40               |
| 7            | ~2.10          | 60               |
| 7            | ~1.95          | 80               |
| 7            | ~1.70          | 100              |
| 8            | ~2.10          | 40               |
| 8            | ~2.15          | 60               |
| 8            | ~1.60          | 80               |
| 8            | ~1.40          | 100              |

Answer:
Chlorination (Cl_2 Exposure): Represented by the rising edge where Cl uptake increases.
Ion Bombardment (Ar^+Irradiation): Represented by the steep downward slope.
Physical Action: The downward slope corresponds to the removal (etching) of the chlorinated surface layer by the argon ions.

Answer: Higher Residual Contamination. They are accepting a trade-off where the surface retains significantly more Chlorine (approx. 0.5–0.6 ML vs 0.2 ML) after every cycle, which could alter the starting conditions for the next layer of growth or etch.

Answer: The 40 eV ions possess lower kinetic energy, which is insufficient to break all the bonds holding the chlorinated species to the surface. This results in an incomplete etch, leaving a "residue" of chemically modified material (0.8 ML). In contrast, 100 eV ions have enough energy to sputter away nearly the entire modified layer, resulting in a cleaner surface.

Answer: It implies process drift and a loss of the "self-limiting" characteristic essential for ALE. If the residual chlorine accumulates with every cycle, the surface chemistry changes continuously, likely leading to variations in etch rate or surface roughness over time. A 500-cycle run would likely fail to meet tight tolerance specifications due to this cumulative error.


FIG. 5. Etch per cycle as a function of  $\mathsf{Ar}^+$  ion energy. For the "High Fluence" simulation results, one cycle corresponds to  $2255\mathrm{Cl}_2$  impacts and  $1000\mathrm{Ar}^+$  impacts, while for "Low Fluence," one cycle corresponds to  $2255\mathrm{Cl}_2$  impacts and  $68\mathrm{Ar}^+$  impacts. Solid red circles are physical sputtering results from the MD simulations, open red circles are ALE results from the "High Fluence" MD simulations, and open red triangles are ALE results from the "Low Fluence" MD simulations. Solid blue squares are experimental physical sputtering results, while open blue squares are experimental ALE results, both from Park et al. (Ref. 11). The dotted lines indicate where the supposed ALE window is located from experimental results.

The scatter plot represents that Atomic Layer Etching produces a much higher EPC than physical sputtering at the same ion energies, demonstrating the advantage of chlorine surface modification. An optimal “ALE window” (~70–90 eV) allows selective removal of the modified layer without damaging bulk silicon, while sufficient ion fluence is essential, as low fluence yields negligible etching despite chlorination. Etch per cycle is shown as a function of Ar⁺ ion energy. For the “High Fluence” simulation results, one cycle corresponds to 2255 Cl₂ impacts and 1000 Ar⁺ impacts, while for “Low Fluence,” one cycle corresponds to 2255 Cl₂ impacts and 68 Ar⁺ impacts. Solid red circles represent physical sputtering results from MD simulations, open red circles represent ALE results from the “High Fluence” MD simulations, and open red triangles represent ALE results from the “Low Fluence” MD simulations. Solid blue squares are experimental physical sputtering results, while open blue squares are experimental ALE results, both from Park et al. (Ref. 11). The dotted lines indicate the experimentally identified ALE window.

| Ar⁺ Energy (eV) | Etch per Cycle (Å/cycle) | Process / Condition |
|-----------------|--------------------------:|---------------------|
| 40              | 0.031                     | Physical Sputtering (Simulation) |
| 40              | 0.458                     | ALE (Simulation, High Fluence) |
| 40              | 0.181                     | ALE (Simulation, Low Fluence) |
| 40              | 0                         | Physical Sputtering (Experiment) |
| 40              |                            | ALE (Experiment) |
| 50              | 0.083                     | Physical Sputtering (Simulation) |
| 50              | 0.5941                    | ALE (Simulation, High Fluence) |
| 50              | 0.233                     | ALE (Simulation, Low Fluence) |
| 50              | 0                         | Physical Sputtering (Experiment) |
| 50              |                            | ALE (Experiment) |
| 60              |                            | Physical Sputtering (Simulation) |
| 60              | 0.739                     | ALE (Simulation, High Fluence) |
| 60              | 0.205                     | ALE (Simulation, Low Fluence) |
| 60              | 0.167                     | Physical Sputtering (Experiment) |
| 60              | 0.233                     | ALE (Experiment) |
| 70              | 0.289                     | Physical Sputtering (Simulation) |
| 70              | 0.894                     | ALE (Simulation, High Fluence) |
| 70              |                            | ALE (Simulation, Low Fluence) |
| 70              | 0.200                     | Physical Sputtering (Experiment) |
| 70              | 1.105                     | ALE (Experiment) |
| 80              | 0.425                     | Physical Sputtering (Simulation) |
| 80              | 1.020                     | ALE (Simulation, High Fluence) |
| 80              |                            | ALE (Simulation, Low Fluence) |
| 80              | 0.360                     | Physical Sputtering (Experiment) |
| 80              | 1.076                     | ALE (Experiment) |
| 90              | 0.598                     | Physical Sputtering (Simulation) |
| 90              | 1.175                     | ALE (Simulation, High Fluence) |
| 90              |                            | ALE (Simulation, Low Fluence) |
| 90              |                            | Physical Sputtering (Experiment) |
| 90              |                            | ALE (Experiment) |
| 100             | 0.763                     | Physical Sputtering (Simulation) |
| 100             | 1.320                     | ALE (Simulation, High Fluence) |
| 100             |                            | ALE (Simulation, Low Fluence) |
| 100             | 0.894                     | Physical Sputtering (Experiment) |
| 100             | 1.316                     | ALE (Experiment) |

Answer: The "Low Fluence" step uses only 68 $Ar^+ impacts, which is mathematically insufficient to cover and clear the surface sites generated by the 2255 Cl₂ impacts.

Answer: At 100 eV, the selectivity decreases because Physical Sputtering (uncontrolled removal) becomes a dominant fraction of the total etch. Operating at 70 eV maintains a larger gap between the ALE rate and the Sputtering rate (Solid Square is low, ~0.2 Å/cycle). This ensures the etching is primarily driven by chemical modification, not brute-force kinetic damage.

Answer: Chlorination weakens the surface binding energy. The adsorption of Chlorine atoms draws electron density away from the silicon-silicon backbonds, lowering the energy threshold required to break them. This allows the same 80 eV ions to remove significantly more material than they could from a pristine, unmodified surface.

Answer: Above the window, the physical sputtering component becomes too high, causing ions to penetrate and damage the underlying lattice even after the chlorinated layer is removed.


FIG. 6. Etch per cycle as a function of irradiation time for  $70\mathrm{eV}\mathrm{Ar}^+$  ions. Red circles are from MD simulations, while blue squares are experimental results from Park et al. (Ref. 11). For the simulation results, the chlorination step consists of  $2255\mathrm{Cl}_2$  impacts, while for experiments  $20\mathrm{SCCM}$  of  $\mathrm{Cl}_2$  is supplied for  $20\mathrm{s}$ . It is assumed a  $30\mathrm{s}$  ion irradiation time corresponds to  $1000$  impacts in the simulation. The dotted line is the experimentally saturated EPC (1.36 Å/cycle).

The scatter plot compares simulated and experimental etch per cycle (EPC) as a function of Ar⁺ ion irradiation time at 70 eV. Both datasets show EPC increasing with time before saturating, with the simulation (red circles) closely matching the trend and saturation value (~1.36 Å/cycle) of the experimental results (blue squares).

| Ar⁺ Irradiation (s) | Etch per Cycle (Å/cycle) | Source      |
|--------------------|--------------------------:|-------------|
| 8                  | 0.49                      | Simulation  |
| 8                  |                           | Experiment  |
| 10                 |                           | Simulation  |
| 10                 | 0.20                      | Experiment  |
| 15                 | 0.62                      | Simulation  |
| 15                 |                           | Experiment  |
| 20                 |                           | Simulation  |
| 20                 | 0.97                      | Experiment  |
| 30                 | 0.89                      | Simulation  |
| 30                 | 1.12                      | Experiment  |
| 35                 |                           | Simulation  |
| 35                 | 1.29                      | Experiment  |
| 37                 | 1.06                      | Simulation  |
| 37                 |                           | Experiment  |
| 40                 |                           | Simulation  |
| 40                 | 1.40                      | Experiment  |
| 45                 | 1.02                      | Simulation  |
| 45                 | 1.35                      | Experiment  |
| 50                 |                           | Simulation  |
| 50                 | 1.37                      | Experiment  |
| 60                 | 1.31                      | Simulation  |
| 60                 |                           | Experiment  |

Answer:
1.    Simulate the chlorination step with 2255 Cl₂ impacts.

2.     Simulate the bombardment step with Ar⁺ ions (70 eV) for a duration corresponding to the target irradiation time.

3.    Calculate the etch depth by comparing surface positions before and after the simulated cycle.
The correlation (30 s ≈ 1000 impacts) calibrates the simulation's timescale to real-world tool parameters, enabling direct quantitative comparison between the model and physical experiment.

Answer: Yes. The close agreement validates the model's predictive power for this chemistry. It can rapidly and inexpensively screen irradiation times to identify the saturation point, significantly reducing the number of costly experimental trials needed for initial reactor recipe development.

Answer: EPC increases with irradiation time then saturates. This occurs because the Ar⁺ ions can only remove the finite-thickness chlorinated (Si-Clₓ) layer created in the prior step. Once all the chlorinated material is sputtered away, additional ion bombardment does not increase the etch depth, leading to the observed saturation.

Answer: This implies precise depth control is achievable. By running a calculated number of cycles (e.g., ~15 cycles), one can etch to a target depth of ~20 Å with atomic-scale accuracy. The self-limiting, saturating behavior ensures each cycle removes a consistent thickness, which is critical for such a shallow etch.


Fig. 12. The vacuum pressure versus etching per cycle relationship for several substrate velocities.

The scatter plot shows the relationship between vacuum pressure (in Pa) and etching per cycle (in Å/cycle) at different speeds (60 mm/s, 90 mm/s, and 120 mm/s).

| Vacuum pressure (Pa) | Etching per cycle (Å/cycle) 60mm/s |Etching per cycle (Å/cycle) 90mm/s |Etching per cycle (Å/cycle) 120mm/s |
|---|---|---|---|
|-200 | 0.37 |0.25|0.13|
|-150 | 0.40 |0.30|0.20|
|-100 | 0.40 |0.33|0.22|
|-50 | 0.40 |0.33|0.26|

Answer: In the ideal case the vacuum pressure between the sample and the table does not have an influence on the trend. I.e. a straightline should be observed.

Answer: It could be that the process gases are pumped away during the dosing, due to the low vacuum pressure.

Answer: 0.41 Å/cycle and 0.33 Å/cycle respectively.

Answer: Linear increase

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/16/Multiscale computational fluid dynamics modeling.pdf


Fig.7. t  t divided wafer in Fig. 2b to the bottom.

The partial pressure of HF is plotted against substrate position for reactors G0 under different conditions. Each has four different dwell times (1.0 s, 0.3 s, 0.2 s, 0.1 s) represented by different markers.

The partial pressure of HF is plotted against substrate position for reactors G1 under different conditions.

The partial pressure of HF is plotted against substrate position for reactors G2 under different conditions.

The partial pressure of HF is plotted against substrate position for reactors G3 under different conditions.

| Substrate Position | 0.1 s | 0.2 s | 0.3 s | 1.0 s |
|--------------------|-------|-------|-------|-------|
| 1                  | 08    | 38    | 58    | 68    |
| 2                  | 9       | 39    | 59    | 68    |
| 3                  | 10    | 40    | 60    | 68   |
| 4                  | 11    | 41    | 61    | 68    |
| 5                  | 12    | 42    | 62    | 68   |
| 6                  | 13    | 43    | 62    | 68    |
| 7                  | 13    | 43    | 62    | 68    |
| 8                  | 12    | 42    | 62    | 68    |
| 9                  | 11    | 41    | 61    | 68    |
| 10                 | 10    | 40    | 60    | 68    |
| 11                 | 9    | 39    | 59    | 68    |
| 12                 | 8    | 38    | 58    | 68    |

Answer: The reactor with the inclined plate (G3) has the most uniform flow pattern at every time step, in which the largest pressure deviation is 2.9 Pa at 0.2 s.

Answer: Among G0, G1 and G2, G2 reactor has uniform flow at the shortest time of 0.1s

Answer: Yes

Answer:
For every group (G0–G3), partial pressure increases strongly with longer HF pulse time: 0.1 s < 0.2 s < 0.3 s ≪ 1.0 s.
The 1.0 s trace is near the upper limit (~68–70 Pa) and essentially flat. Across-substrate uniformity: Pressures are lower at the edges and higher near the center, especially at the shorter pulses (0.1–0.3 s). The center‑to‑edge difference is ~4–10 Pa depending on dose and group.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/17/Multiscale computational fluid dynamics modeling of thermal atomic layer etching.pdf


Fig.10. Selective etching of TiN at  $250^{\circ}C$  using  $\mathrm{O_3}$  and HF in the presence of other surrounding materials of  $\mathrm{Al}_2\mathrm{O}_3$ $\mathrm{HfO_2}$ $\mathrm{ZrO_2}$ $\mathrm{SiO_2}$  and  $\mathrm{Si_3N_4}$  . Reproduced from Ref. [20].

The line chart shows the film thickness of different materials (TiN, Al₂O₃, Si₃N₄, HfO₂, ZrO₂, and SiO₂) after 0 to 400 cycles. There is a linear decrease for TiN, while the others show a plateau.

| Number of Cycles | TiN | Al₂O₃ | Si₃N₄ | HfO₂ | ZrO₂ | SiO₂ |
|---|---|---|---|---|---|---|
| 0 | 75 | - | 40 | 55 | 50 | 50 |
| 100 | 50 | 50 | 40 | 55 | 50 | 50 |
| 200 | 35 | 50 | 40 | 55 | 50 | 50 |
| 300 | 20 | 48 | 40 | 55 | 50 | 50 |
| 400 | - | 42 | 40 | 55 | 50 | 50 |

Answer: The etching of TiN was studied at 250 °C in the presence of other materials such as Al2O3, Si3N4, HfO2, ZrO2, and SiO2, using O2 and HF.

Answer: The film thickness of TiN decreases from approximately 75 Å to 20 Å as the number of cycles increases from 0 to 400.

Answer: TiN.

Answer: As can be seen, the Si3N4 film, shows a slight increase in thickness that could be related to the growth of the material.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/24/Review Paper -- Thermal atomic layer etching Mechanism, materials and prospects.pdf


Fig. 5. Selective etching of  $\mathrm{Al_2O_3}$ ,  $\mathrm{HfO_2}$ ,  $\mathrm{ZrO_2}$ ,  $\mathrm{SiO_2}$ ,  $\mathrm{Si_3N_4}$ , and TiN by the metal ALE using fluorination and ligand-exchange reactions: (a)  $\mathrm{Sn(acac)}_2$  at  $200^{\circ}\mathrm{C}$  and (b) TMA at  $300^{\circ}\mathrm{C}$ . Reproduced from Ref. [29].

The figure shows the changes on the film thickness of various materials (TiN, SiO_2, Si_3N_4, HfO_2, Al_2O_3, ZrO_2) over cycles with Sn(acac)2 at 200 °C.

The figure shows the changes on the film thickness of various materials (TiN, SiO_2, Si_3N_4, HfO_2, Al_2O_3, ZrO_2) over cycles with TMA at 300 °C.

| Number of Cycles | TiN | SiO_2 | Si_3N_4 | HfO_2 | Al_2O_3 | ZrO_2 |
|---|---|---|---|---|---|---|
| 0 | 70 | 50 | 40 | 50 | 48 | 50 |
| 100 | 70 | 50 | 40 | 48 | 20 | 40 |
| 200 | 70 | 50 | 40 | 45 | 0 | 30 |
| 300 | - | - | - | - | - | - |
| 400 | 70 | 50 | 40 | 38 | 0 | 0 |

| Number of Cycles | TiN | SiO_2 | Si_3N_4 | HfO_2 | Al_2O_3 | ZrO_2 |
|---|---|---|---|---|---|---|
| 0 | 70 | 50 | 40 | 50 | 48 | 50 |
| 100 | - | - | - | 48 | 20 | 50 |
| 200 | - | - | - | 45 | 0 | 53 |
| 300 | - | - | - | - | - | - |
| 400 | 75 | 48 | 38 | 35 | 0 | 50 |

Answer: The film thickness for TiN remains approximately constant for the ALE cycle with Sn(acac)2, but increases for the ALE cycle with TMA.

Answer: The film thickness was studied as a function of the number of cycles.

Answer: As the number of cycles increases the thickness of the HfO2, ZrO2 and Al2O3 film decreases, but the thickness of the TiN, SiO2 and Si3N4 films remains approximately constant.

Answer: As can be seen in the subfigure a, Al2O3 has the lowest film thickness at 100 and 200 cycles. Then, at 300 cycles, both Al2O3 and ZrO3 exhibit a value of 0.