Fig. 3. Fluorine content between 225 and  $400^{\circ}\mathrm{C}$ .

The figure presents fluorine (F) and oxygen (O) atomic concentrations measured in WNₓCᵧ films across deposition temperatures from ~225°C to 400°C. Fluorine remains consistently low (<2 at.%), reaching its minimum near 300–350°C, while oxygen remains higher (3–5 at.%), largely from post-deposition air exposure. The trends highlight the temperature region where impurity control is optimal.

| Deposition Temperature (°C)|O Content (at-%)|F Content (at-%)|
|----------------------------|----------------|----------------|
|~225|~4.8|~1.2|
|~250|~4.5|~1.0|
|~275|~5.2|~0.2|
|~300|~4.0|~0.0|
|~325|~3.5|~0.8|
|~350|~2.5–3.0|~0.2|
|~375|~3.2|~0.7|
|~400|~3.8|~1.0|

Answer: Lower fluorine levels indicate more effective ligand removal and better reduction chemistry, which leads to denser, lower-resistivity films with improved electrical and chemical stability. Since fluorine can negatively affect conductivity and barrier integrity, achieving near-zero F content at 300–350°C enhances the film’s suitability for use in advanced interconnect structures where purity and stability are critical.

Answer: Oxygen remains relatively high (4–5 at.%) at all temperatures, while fluorine drops from around 1.0–1.2 at.% at low temperatures to nearly 0 at mid-range temperatures.

Answer: Yes, impurity concentrations change with temperature, with fluorine decreasing significantly at optimal ALD temperatures.

Answer: Low fluorine concentration, Moderate but stable oxygen levels, Temperature-dependent impurity removal, Evidence of an ALD window around 300–350°C

icdar2026-competition-data/dev/atomic-layer-deposition/experimental-usecase/11/K.-E. Elers et al.pdf


(a)

The plot compares NiO film thickness versus ALD cycle number for three Ni precursors. NiO_Alanis and NiO_MeCp track each other closely and show near-linear growth up to ~400 cycles, reaching ~10.8–10.9 nm. NiO_Bu-MeAMD grows faster (steeper slope), reaching ~9.8 nm by ~250 cycles (and the series does not extend beyond that range in this panel). Overall, the main message is the growth-per-cycle difference among precursors, with Bu-MeAMD giving higher thickness at fewer cycles.

| Number of cycles | NiO_Alanis (nm) | NiO_MeCp (nm) | NiO_Bu-MeAMD (nm) |
|---|---|---|---|
| 0   | 0.0 | 0.0 | 0.0 |
| 50  | ~1.2 | ~1.3 | ~0.7 |
| 100 | ~2.6 | ~2.7 | ~3.5 |
| 150 | ~4.0 | ~4.1 | ~5.6 |
| 200 | ~5.4 | ~5.5 | ~7.8 |
| 250 | ~6.7 | ~6.8 | ~9.8 |
| 300 | ~8.1 | ~8.2 |   -  |
| 350 | ~9.5 | ~9.6 |   -  |
| 400 | ~10.8 | ~10.9 | -  |

Answer: A linear thickness increase suggests that the deposition is self-limiting and well-controlled, with a consistent amount of material deposited during each cycle. This is characteristic of ALD-type growth rather than uncontrolled CVD-like behavior.

Answer: NiO_Bu-MeAMD shows the highest growth rate per cycle.

Answer: The nearly identical slopes suggest that both precursors similarly interact with the surface, leading to comparable surface saturation behavior and reaction efficiency during each ALD cycle.

Answer: A higher growth rate can reduce processing time and improve throughput, which is attractive for large-scale fabrication. However, faster growth can sometimes come at the cost of film density, uniformity, or impurity incorporation, so the choice depends on the required film quality.

icdar2026-competition-data/dev/atomic-layer-deposition/experimental-usecase/68/Kousumi Mukherjee et al.pdf


This figure compares the growth per cycle of NiO films deposited using three different precursors as a function of temperature. At low temperature, the Bu-MeAMD precursor exhibits significantly higher growth per cycle than the Alanis and MeCp precursors. As temperature increases, the growth rates converge toward ~0.3 Å per cycle, indicating a common self-limiting growth regime. At the highest temperature, the Alanis-based film shows a modest increase, suggesting a change in surface kinetics or precursor efficiency.

| Temperature (°C) | NiO_Alanis growth (Å/cycle) | NiO_MeCp growth (Å/cycle) | NiO_Bu-MeAMD growth (Å/cycle) |
|---|---|---|---|
| 50  | ~0.34 | ~0.44 | ~0.78 |
| 100 | ~0.28 | ~0.39 | ~0.56 |
| 150 | ~0.28 | ~0.29 | ~0.43 |
| 200 | ~0.30 | ~0.31 | ~0.38 |
| 250 | ~0.31 |   -  | - |
| 300 | ~0.32 | ~0.30   |  - |
| 350 | ~0.40 |  -  |  - |

Answer: NiO_Bu-MeAMD.

Answer: At higher temperatures, surface reactions become more complete and self-limiting behavior strengthens. Excess adsorption that can inflate growth at low temperature is reduced, and weakly bound species are more likely to desorb, lowering net growth per cycle.

Answer: It implies that Bu-MeAMD reacts readily with surface sites even at low thermal energy, possibly due to weaker ligand bonding or more favorable adsorption geometry compared to the other precursors.

Answer: No


Figure 2. Nucleation curves for ABC-type ALD of  $\mathrm{SiO}_2$  on different starting surfaces. The graphs show the thickness as a function of the number of ALD cycles as measured by in situ SE. We note that due to the use of an  $\mathbf{O}_2$  plasma as the co-reactant, the topmost layer of the starting surfaces can be oxidized during the first few ALD cycles, which was accounted for in the SE modeling of  $\mathrm{SiN}_x$ .

This multi line plot shows nucleation curves for SiO₂ deposition via an ABC-type ALD process on seven different starting surfaces (SiO₂, SiNₓ, GeO₂, WO₃, HfO₂, TiO₂, Al₂O₃). It reveals significant differences in nucleation delay: some surfaces (GeO₂, SiO₂, WO₃, SiNₓ) show immediate linear growth (~0.09 nm/cycle), while others (Al₂O₃, TiO₂, HfO₂) exhibit a delay of 10-15 cycles before growth begins. This demonstrates a pathway for selective area deposition.

| Number of Cycles | SiO₂ (nm) | SiNₓ (nm) | GeO₂ (nm) | WOₓ (nm) | HfO₂ (nm) | TiO₂ (nm) | Al₂O₃ (nm) |
|---|---|---|---|---|---|---|---|
| 0 | 0.00 | 0.15 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| 1 | 0.08 | 0.05 | 0.02 | 0.01 | 0.00 | 0.00 | 0.00 |
| 2 | 0.18 | 0.10 | 0.08 | 0.05 | 0.00 | 0.00 | 0.00 |
| 3 | 0.28 | 0.20 | 0.15 | 0.10 | 0.00 | 0.00 | 0.00 |
| 4 | 0.38 | 0.30 | 0.22 | 0.18 | 0.00 | 0.00 | 0.00 |
| 5 | 0.48 | 0.40 | 0.30 | 0.25 | 0.00 | 0.00 | 0.00 |
| 6 | 0.58 | 0.50 | 0.38 | 0.30 | 0.00 | 0.00 | 0.00 |
| 7 | 0.68 | 0.60 | 0.45 | 0.38 | 0.00 | 0.00 | 0.00 |
| 8 | 0.80 | 0.70 | 0.52 | 0.42 | 0.00 | 0.00 | 0.00 |
| 9 | 0.95 | 0.85 | 0.60 | 0.48 | 0.01 | 0.01 | 0.00 |
| 10 | 1.02 | 0.98 | 0.68 | 0.55 | 0.02 | 0.02 | 0.00 |
| 11 | 1.10 | 1.08 | 0.75 | 0.62 | 0.05 | 0.05 | 0.00 |
| 12 | 1.20 | 1.18 | 0.82 | 0.70 | 0.08 | 0.07 | 0.00 |
| 13 | 1.30 | 1.25 | 0.90 | 0.78 | 0.10 | 0.09 | 0.01 |
| 14 | 1.40 | 1.35 | 0.98 | 0.85 | 0.12 | 0.10 | 0.02 |
| 15 | 1.50 | 1.45 | 1.05 | 0.92 | 0.15 | 0.12 | 0.03 |
| 16 | 1.60 | 1.55 | 1.15 | 1.00 | 0.18 | 0.15 | 0.05 |
| 17 | 1.70 | 1.65 | 1.22 | 1.08 | 0.22 | 0.18 | 0.06 |
| 18 | 1.80 | 1.75 | 1.30 | 1.15 | 0.26 | 0.22 | 0.08 |
| 19 | 1.88 | 1.85 | 1.40 | 1.22 | 0.30 | 0.26 | 0.09 |
| 20 | 1.95 | 1.95 | 1.50 | 1.30 | 0.35 | 0.30 | 0.10 |
| 21 | - | - | 1.60 | 1.40 | 0.38 | 0.32 | 0.12 |
| 22 | - | - | 1.70 | 1.50 | 0.42 | 0.35 | 0.13 |
| 23 | - | - | 1.80 | 1.60 | 0.50 | 0.38 | 0.15 |
| 24 | - | - | 1.90 | 1.70 | 0.55 | 0.42 | 0.18 |
| 25 | - | - | 2.00 | 1.80 | 0.60 | 0.48 | 0.20 |

Answer:
Cycles 1-15: Nucleation Delay Phase – Precursor adsorbs/reacts but forms no measurable continuous SiO₂ film (thickness ~0 nm).

Cycle ~15: Nucleation Completion – Isolated SiO₂ islands coalesce into a continuous film.

Cycles 16: Linear Growth Phase – Steady-state SiO₂ deposition at ~0.09 nm/cycle.

Answer: The ABC process shows a 15-cycle delay on Al₂O₃, enabling selectivity, while the BC process shows no delay and immediate growth. The trade-off is clear: the ABC process sacrifices initial growth rate and material efficiency to achieve surface selectivity. To deposit a thin SiO₂ film only on GeO₂ and not on Al₂O₃, you must use the slower, initially non-productive ABC cycle, accepting lower throughput for the benefit of pattern definition without etching.

Answer: They exhibit linear growth immediately from the first cycle, implying that there is no nucleation barrier and the precursor adsorption is favorable on the starting substrate surface.

Answer: No — the SF₆/TMA etching chemistry is not suitable for processes limited to <150 °C.

icdar2026-competition-data/dev/atomic-layer-deposition/simulation-usecase/4/Alfredo Mameli et al.pdf


Figure 3. Apparent thickness as measured after every reactant dosing pulse on (a)  $\mathrm{Al}_2\mathrm{O}_3$  and (b)  $\mathrm{SiO}_2$ . The left-hand part of the figure represents 3 AC cycles with Hacac (A) and  $\mathrm{O}_2$  plasma (C) pulses, the middle part 3 ABC cycles with Hacac (A), BDEAS precursor (B), and  $\mathrm{O}_2$  plasma (C) pulses, and the right-hand part 3 BC cycles with BDEAS precursor (B) and  $\mathrm{O}_2$  plasma (C) pulses. The apparent thickness is used to reflect that the SE modeling did not take into account the dielectric function of the surface groups such that the thickness after step A might not correspond to the physical thickness. The starting surfaces were prepared by regular ALD.

This in-situ spectroscopic ellipsometry (SE) data tracks the apparent thickness after every reactant pulse during different ALD cycle types (AC, ABC, BC) on Al₂O₃ starting surfaces. It reveals how different pulse sequences interact with each surface, showing pulses that increase thickness (film growth) or decrease it (etching/ligand exchange).

This in-situ spectroscopic ellipsometry (SE) data tracks the apparent thickness after every reactant pulse during different ALD cycle types (AC, ABC, BC) on SiO₂ starting surfaces. It reveals how different pulse sequences interact after 3 cycles where a steep increase can be observed.

| Number of Cycles | Apparent Thickness (nm) | Step        |
|------------------|--------------------------|-------------|
| 0                | —                        | A - Hacac   |
| 0                | —                        | B - BDEAS   |
| 0                | —                        | C - O₂ Plasma |
| 0.5              | —                        | A - Hacac   |
| 0.5              | —                        | B - BDEAS   |
| 0.5              | 0                        | C - O₂ Plasma |
| 1                | 0.36                     | A - Hacac   |
| 1                | —                        | B - BDEAS   |
| 1                | —                        | C - O₂ Plasma |
| 1.5              | —                        | A - Hacac   |
| 1.5              | —                        | B - BDEAS   |
| 1.5              | 0.07                     | C - O₂ Plasma |
| 2                | 0.33                     | A - Hacac   |
| 2                | —                        | B - BDEAS   |
| 2                | —                        | C - O₂ Plasma |
| 2.5              | —                        | A - Hacac   |
| 2.5              | —                        | B - BDEAS   |
| 2.5              | 0.07                     | C - O₂ Plasma |
| 3                | 0.33                     | A - Hacac   |
| 3                | —                        | B - BDEAS   |
| 3                | —                        | C - O₂ Plasma |
| 3.5              | —                        | A - Hacac   |
| 3.5              | —                        | B - BDEAS   |
| 3.5              | 0.05                     | C - O₂ Plasma |
| 4                | 0.32                     | A - Hacac   |
| 4                | 0.31                     | B - BDEAS   |
| 4                | —                        | C - O₂ Plasma |
| 4.5              | —                        | A - Hacac   |
| 4.5              | —                        | B - BDEAS   |
| 4.5              | 0.04                     | C - O₂ Plasma |
| 5                | 0.34                     | A - Hacac   |
| 5                | 0.33                     | B - BDEAS   |
| 5                | —                        | C - O₂ Plasma |
| 5.5              | —                        | A - Hacac   |
| 5.5              | —                        | B - BDEAS   |
| 5.5              | 0.04                     | C - O₂ Plasma |
| 6                | 0.34                     | A - Hacac   |
| 6                | 0.33                     | B - BDEAS   |
| 6                | —                        | C - O₂ Plasma |
| 6.5              | —                        | A - Hacac   |
| 6.5              | —                        | B - BDEAS   |
| 6.5              | 0.04                     | C - O₂ Plasma |
| 7                | —                        | A - Hacac   |
| 7                | 0.21                     | B - BDEAS   |
| 7                | —                        | C - O₂ Plasma |
| 7.5              | —                        | A - Hacac   |
| 7.5              | —                        | B - BDEAS   |
| 7.5              | 0.08                     | C - O₂ Plasma |
| 8                | —                        | A - Hacac   |
| 8                | 0.26                     | B - BDEAS   |
| 8                | —                        | C - O₂ Plasma |
| 8.5              | —                        | A - Hacac   |
| 8.5              | —                        | B - BDEAS   |
| 8.5              | 0.18                     | C - O₂ Plasma |
| 9                | —                        | A - Hacac   |
| 9                | 0.36                     | B - BDEAS   |
| 9                | —                        | C - O₂ Plasma |
| 9.5              | —                        | A - Hacac   |
| 9.5              | —                        | B - BDEAS   |
| 9.5              | 0.28                     | C - O₂ Plasma |
| 10               | —                        | A - Hacac   |
| 10               | —                        | B - BDEAS   |
| 10               | —                        | C - O₂ Plasma |

| Number of Cycles | Apparent Thickness (nm) | Step         |
|------------------|--------------------------|--------------|
| 0                | —                        | A - Hacac    |
| 0                | 0                        | B - BDEAS    |
| 0                | 0                        | C - O₂ Plasma |
| 0.5              | 0.02                     | A - Hacac    |
| 0.5              | —                        | B - BDEAS    |
| 0.5              | —                        | C - O₂ Plasma |
| 1                | —                        | A - Hacac    |
| 1                | —                        | B - BDEAS    |
| 1                | 0.001                    | C - O₂ Plasma |
| 1.5              | 0.001                    | A - Hacac    |
| 1.5              | —                        | B - BDEAS    |
| 1.5              | —                        | C - O₂ Plasma |
| 2                | —                        | A - Hacac    |
| 2                | —                        | B - BDEAS    |
| 2                | 0.004                    | C - O₂ Plasma |
| 2.5              | 0.001                    | A - Hacac    |
| 2.5              | —                        | B - BDEAS    |
| 2.5              | —                        | C - O₂ Plasma |
| 3                | —                        | A - Hacac    |
| 3                | —                        | B - BDEAS    |
| 3                | 0.004                    | C - O₂ Plasma |
| 3.5              | 0.001                    | A - Hacac    |
| 3.5              | —                        | B - BDEAS    |
| 3.5              | —                        | C - O₂ Plasma |
| 4                | —                        | A - Hacac    |
| 4                | 0.21                     | B - BDEAS    |
| 4                | 0.09                     | C - O₂ Plasma |
| 4.5              | 0.12                     | A - Hacac    |
| 4.5              | —                        | B - BDEAS    |
| 4.5              | —                        | C - O₂ Plasma |
| 5                | —                        | A - Hacac    |
| 5                | 0.31                     | B - BDEAS    |
| 5                | 0.19                     | C - O₂ Plasma |
| 5.5              | 0.21                     | A - Hacac    |
| 5.5              | —                        | B - BDEAS    |
| 5.5              | —                        | C - O₂ Plasma |
| 6                | —                        | A - Hacac    |
| 6                | 0.42                     | B - BDEAS    |
| 6                | 0.29                     | C - O₂ Plasma |
| 6.5              | —                        | A - Hacac    |
| 6.5              | —                        | B - BDEAS    |
| 6.5              | —                        | C - O₂ Plasma |
| 7                | —                        | A - Hacac    |
| 7                | 0.52                     | B - BDEAS    |
| 7                | 0.43                     | C - O₂ Plasma |
| 7.5              | —                        | A - Hacac    |
| 7.5              | —                        | B - BDEAS    |
| 7.5              | —                        | C - O₂ Plasma |
| 8                | —                        | A - Hacac    |
| 8                | 0.62                     | B - BDEAS    |
| 8                | —                        | C - O₂ Plasma |
| 8.5              | —                        | A - Hacac    |
| 8.5              | —                        | B - BDEAS    |
| 8.5              | 0.50                     | C - O₂ Plasma |
| 9                | —                        | A - Hacac    |
| 9                | 0.72                     | B - BDEAS    |
| 9                | —                        | C - O₂ Plasma |
| 9.5              | —                        | A - Hacac    |
| 9.5              | —                        | B - BDEAS    |
| 9.5              | 0.60                     | C - O₂ Plasma |
| 10               | —                        | A - Hacac    |
| 10               | —                        | B - BDEAS    |
| 10               | —                        | C - O₂ Plasma |

Answer: It implies the as-deposited film from BDEAS on SiO₂ is already more fully oxidized or denser than on Al₂O₃, requiring less further modification by the O₂ plasma.

Answer:
Pulse A (Hacac): Apparent thickness decreases (ligand exchange/etch).

Pulse B (BDEAS): Apparent thickness increases (precursor adsorption/Si–O deposition).

Pulse C (O₂ plasma): Apparent thickness increases slightly (oxidation/ densification).

Answer: On Al₂O₃, the Hacac pulse causes a significant thickness decrease, indicating active ligand-exchange or etching. On SiO₂, it causes little to no change. This reveals a critical balance which is Hacac is an effective surface modifier for Al₂O₃ (enabling subsequent ABC selectivity), but it also etches Al₂O₃, which could be detrimental if not tightly controlled. On SiO₂, it is inert, providing no benefit but also no harm.

Answer: This difference in behaviour allows both selective growth and gentle etch-back. In a pattern containing Al₂O₃ and SiO₂, the ABC cycles would grow SiO₂ only on the Al₂O₃ regions, while slightly thinning the Al₂O₃ and leaving the SiO₂ regions unchanged. This helps fill features on one material while cleaning unwanted film from the other, improving the overall pattern quality.


Figure 12. Calculated potential energy profiles for the reaction between  $-\mathrm{Si(OH)}_3$  species and surface  $-\mathrm{OH}$  group.

The plot relates reaction pathways and the energy changes along these different pathways between the transtition states, reactants and products

| Reaction Pathway | Energy (kcal/mol) |
|------------------|------------------|
| R               | 0                |
| TS (a)            | 20.8               |
| TS  (b)            | 30               |
| TS  (c)            | 34.5               |
| P(a)            | -10.2              |
| P(b)            | 7.3            |
| P(c)            | 4.8           |

Answer: Yes

Answer: Reaction between the −SiH3 Intermediate with the Surface −OH Group Followed by Oxidation. To grow a denser and purer SiO2 film via ALD, the −SiH3 intermediate species on the surface could react with a surface −OH group to form a −SiH2 group.

Answer:
The calculated activation energy  are
1. For Path a 36.8  kcal/mol
2. For Path b 37.1 kcal/mol
3. For path c is 41.9 kcal/mol

Answer:
Thermodynamically, this process is moderately endothermic with the calculated reaction energy of 10.3 kcal/mol. The structure of the final product (Pc)
exhibits a modest geometric strain with the O−Si−O angle of 117.1°, which deviates slightly from the typical angle of 109.8° expected for sp3 hybridization. The calculated Si−O distance is 1.679 Å in the final state, significantly longer than the corresponding values in SiO2 single crystal (1.610 Å)

icdar2026-competition-data/dev/atomic-layer-deposition/simulation-usecase/58/Liang Huang et al.pdf


Figure 13. Calculated potential energy profiles of the whole reaction.

The figure illustrates a reaction pathway involving the dissociation of DSBAS (Dihydrogen Silicate Borate Ammonium Salt) into Si(OH)2* through various transition states (TS) and intermediates.

| Reaction Pathway | Energy (kcal/mol) |
|----------------------------|----------------|
| OH* (DSBAS Dissociation)   | 0              |
| TS (DSBAS Dissociation)    | 6.1            |
| SiH₃                                              | -5             |
| TS (H₂ elimination Path a) | 36.8           |
| TS (H₂ elimination Path b) | 41.9           |
| TS (H₂ elimination Path c) | 37.1           |
| TS (oxidation)             | 12.7           |
| SiH₂                                 | -25            |
| SiH₂(OH)*                   | -121           |
| TS (Oxidation)             |-109.2          |
| SiH(OH)₂                         | -225           |
| TS (Oxidation)             | -219.5         |
| Si(OH)₃                             | -340           |
| TS (H₂O elimination Path a)| -319.2         |
| TS (H₂O elimination Path b)| -310           |
| TS (H₂O elimination Path c)| -305.5         |
| Si(OH)₂* (Path a)          |  -330          |
| Si(OH)₂* (Path b)          |  -340          |
| Si(OH)₂* (Path c)          |  -350          |

Answer: Yes

Answer: The ALD process is initiated by the dissociative chemisorption of DSBAS, which is both thermochemically and kinetically facile. Elimination of H2 through reaction between the resultant −SiH3 species and a nearby surface hydroxyl group is kinetically prohibitive. Thus, further reactions along this pathway can be essentially ruled out.

Answer:
Although there are three possible pathways for the −Si(OH)3 species to react with the adjacent surface hydroxyl groups, only one of them is both
thermodynamically and kinetically favorable, which leads to growing a SiO2 thin film in a crystalline structure

Answer: The thin film deposited with DSBAS and ozone to be dense and conformal and suitable for  low-temperature deposition of SiO2 films.


Figure 7. Calculated potential energy profiles for the reaction between  $-\mathrm{SiH}_3$  species and surface  $-\mathrm{OH}$  group.

The chart illustrates a reaction pathway with energy changes at various points, including reactants (R), transition state (TS), and products (P) for three reaction pathways - a, b, c.

| Reaction Pathway | Energy (kcal/mol) |
|------------------|------------------|
| R               | 0                |
| TS (a)      | 36.8             |
| TS (b)      | 37.1            |
| TS (c)      | 41.9             |
| P(a)            | -22              |
| P(b)            | 11             |
| P(c)            | 1             |

Answer: No

Answer:
1. For Path a = 36.8 kcal/mol
2. For path b = 37.1 kcal/mol
3. For path c = 41.9 kcal/mol

Answer: Process b was found to be modestly endothermic with the reaction energy of 0.2 kcal/mol  and for path C thermodynamically, the process is moderately endothermic with the calculated reaction energy of 10.3 kcal/mol

Answer: From the figure, path a and path c have the same transition state energy profile.


Figure 3. (a) Mass change after the TMA exposure  $(\Delta M_{\mathrm{TMA}})$ , mass change after the HF exposure  $(\Delta M_{\mathrm{HF}})$  and mass change per cycle (MCPC) versus number of ALE cycles at  $300^{\circ}\mathrm{C}$ . (b)  $\Delta M_{\mathrm{TMA}} / \mathrm{MCPC}$  ratio versus number of ALE cycles.

Evolution of mass changes during Al₂O₃ ALE at 300 °C, showing the mass change after TMA exposure (ΔM_TMA), the mass change after HF exposure (ΔM_HF), and the mass change per cycle (MCPC). After a short nucleation period, ΔM_TMA and ΔM_HF reach constant values, resulting in a steady-state MCPC of approximately −15.9 ng/(cm²·cycle).

ΔM_TMA/MCPC ratio as a function of ALE cycles, which stabilizes at approximately 1.8 after the first three cycles. This steady ratio is used to define the stoichiometry of the ALE reactions and indicates consistent, repeatable mass changes.

| Number of cycles | ΔM_HF (ng/cm²) | MCPC (ng/(cm²·cycle)) | ΔM_TMA (ng/cm²) |
|------------------|----------------|-----------------------|------------------|
| 0   | ~35 | ~ -15 | ~ -30 |
| 20  | ~15 | ~ -15 | ~ -30 |
| 40  | ~15 | ~ -15 | ~ -30 |
| 60  | ~15 | ~ -15 | ~ -30 |
| 80  | ~15 | ~ -20 | ~ -30 |
| 100 | ~15 | ~ -15 | ~ -30 |

| Number of cycles | ΔM_TMA / MCPC |
|------------------|---------------|
| 0   | ~0.5 |
| 20  | ~2.0 |
| 40  | ~2.0 |
| 60  | ~2.0 |
| 80  | ~2.0 |
| 100 | ~2.0 |

Answer: This value can be used to calculate the stoichiometry of the reactions.

Answer: For every cycle the mass changes are constant showing the self-limiting and controlable behaviour of ALE.

Answer: It could be that there are some defects on the substrate to which HF can adsorb. Similar for TMA.

Answer: A near-constant ratio indicates that the TMA-related mass change scales proportionally with the net per-cycle mass change. This suggests the TMA half-reaction contribution remains consistent across most cycles. Such behavior is consistent with a stable surface chemistry after the initial transient.

Answer:
-Monitor whether ΔM_TMA/MCPC remains near ~2
-Flag sustained drift away from this value
-Treat early outliers as startup behavior and focus on the stable regime

Answer: A constant ratio of ~1.8 indicates stable reaction stoichiometry throughout the ALE process.

Answer: Roughness changes usually alter surface site density.

Answer: The ΔMTMA/MCPC ratio shows a steady-state value of 1.8 after the first three ALE cycles. The ΔMTMA/MCPC ratio will be employed to define the stoichiometry of the Al2O3 ALE reactions

Answer: After a short nucleation period,  MCPC attains a steady state value of −15.9 ng/(cm2 cycle).

Answer: First two cycles.

Answer: Yes

Answer: No

Answer: First three cycles → ΔMTMA/MCPC increases, After three cycles → ratio becomes steady

Answer: A constant MCPC shows that the mass change per cycle is reproducible and self-limiting.

Answer: The ΔMTMA/MCPC ratio provides a measure of the relative mass contribution from TMA during each cycle. By monitoring this ratio, researchers can define the stoichiometry of the ALE reactions and verify that the process remains consistent across cycles. A stable ratio ensures predictable etching behavior and allows optimization of process parameters for precise Al₂O₃ removal.

Answer: The mass change per cycle remains relatively constant throughout the number of cycles.

Answer: As we can see in the figure, the difference between the mass change after HF exposure and the mass change after TMA exposure leads to the MCPC being closest to the TMA mass change values, meaning that TMA exposure has the greatest impact on the mass change per cycle.

Answer: This means that the value of the last cycle is more negative than that of the previous one. For this reason, the difference between the two is still negative.

Answer: Around 180 ng/cm² is removed.

Answer: The MCPC is calculated by adding both the ΔM's of the TMA and HF subcycles together.

Answer: ΔM_HF is the mass change measured after the HF half-reaction. ΔM_TMA is the mass change measured after the TMA half-reaction. MCPC is the net mass change over a full ALE cycle, reflecting the combined outcome of both steps.

Answer:
-Most stable: ΔM_HF, which stays near ~15 ng/cm² after the initial cycle
-Also largely stable: ΔM_TMA around −30 ng/cm²
-Largest deviation: MCPC, which shows a deeper negative point near ~80 cycles

Answer: The first cycles establish the initial AlF₃ surface layer on the hydroxylated Al₂O₃ substrate (nucleation period).

Answer: ΔM_TMA (blue): mass change after TMA exposure; ΔM_HF (red): mass change after HF exposure; MCPC (black): total mass change per cycle.

Answer: Yes. The constant values over 100 cycles demonstrate highly reproducible, steady-state etching behavior.

Answer:
1.  HF Exposure: Fluorinates the Al₂O₃ surface, forming a non-volatile AlF₃-like layer (mass gain).

2.  Purge: Removes excess HF and byproducts.

3.  TMA Exposure: Performs ligand-exchange, converting the AlF₃ layer to volatile species that desorb (mass loss).

4.  Purge: Clears volatile etch products and residual TMA.
Measuring mass change after each half-cycle with a quartz crystal microbalance (QCM) allows direct, real-time monitoring of the fluorination and ligand-exchange reactions. This confirms each step is self-limiting and enables precise control over the etch amount per cycle.

Answer: The process at 300°C is preferable for consistent etch rate. At lower temperatures, the reaction kinetics are slower, potentially leading to incomplete reactions and longer transients before stabilization. The 300°C data shows stable ΔM_TMA and ΔM_HF values after few cycles, indicating rapid achievement of steady-state surface conditions, which ensures a reproducible etch rate critical for multi-cycle etching.

Answer: The stable mass changes imply a highly suitable process. The consistent, self-limiting half-reactions guarantee uniform etching per cycle, enabling precise depth control (critical for the 10 nm target). Furthermore, the self-limiting nature ensures perfect conformality in high-aspect-ratio trenches, as reactions proceed equally on all surfaces, preventing lateral etching or bowing.

Answer: Yes

Answer: MCPC is defined by mass change after TMA and HF exposure. MCPC = ΔMTMA + ΔMHF.

Answer: 13 ng/cm^2.

Answer: -29 ng/cm^2.

Answer: 16 ng/cm^2.

Answer: According to the authors, this ratio can be used to gain information about the stoichiometry  of the ALE reactions that occur on the Al2O3 substrate.

Answer: TMA exposure.

Answer: A positive ΔMHF means the HF step increases the surface mass, consisting with fluorinating the surface. A negative ΔMTMA means the TMA step decreases the surface mass, indicating it removes material by converting the surface species into volatile products that leave the surface. Overall, HF builds a fluorinated layer, and TMA strips it.

Answer: 300 °C.

Answer: All three remain relatively steady throughout the experiment. ΔM_HF stays slightly positive and ΔM_TMA remains slightly negative with only small drifts, while MCPC stays near a low positive value. The trends suggest that the etching mechanism does not significantly change over time.

Answer: ΔM_HF, ΔM_TMA,  MCPC.

Answer: Yes, the figure shows that after an initial nucleation period, both ΔMTMA and ΔMHF become very constant, indicating that the ALE process has reached a steady state. This steady behavior demonstrates the self-limiting nature of the sequential TMA and HF reactions.

icdar2026-competition-data/dev/atomic-layer-etching/experimental-usecase/24/Trimethylaluminum as the Metal Precursor for the Atomic LayerEtching.pdf


Figure 9. X-ray reflectivity and spectroscopic ellipsometry measurements of  $\mathrm{Al}_2\mathrm{O}_3$  film thickness versus number of  $\mathrm{Al}_2\mathrm{O}_3$  ALE cycles for initial  $\mathrm{Al}_2\mathrm{O}_3$  ALD films grown using  $150\mathrm{Al}_2\mathrm{O}_3$  ALD cycles.

The multiple line chart shows Al₂O₃ thickness as a function of the number of cycles at 300 °C. Thickness decreases approximately linearly with increasing cycles. Measurements from XRR and SE closely agree across the full range, indicating consistent thickness reduction per cycle.

| Number of cycles | Thickness (Å), XRR | Thickness (Å), SE |
|------------------|--------------------|--------------------|
| 0                | ~170               | ~165               |
| 50               | ~130               | ~135               |
| 100              | ~100               | ~105               |
| 200              | ~50                | ~55                |

Answer: The figure shows both X-ray reflectivity and ellipsometry measurements of Al2O3 films.

Answer: Yes

Answer: Yes

Answer: For both growth temperatures (200 °C and 300 °C), Al2O3 thickness decreases as the number of etching cycles increases.

Answer: The highest deposition rate is achieved at 200 degrees C as there the initial thickness is higher.

Answer: Such a difference is not visible as for both the substrates the slope is equal.

Answer: 100 cycles of etching.

Answer: In this specific instance both SE and XRR yield the same thicknesses.

Answer: Thickness is plotted only at specific integer cycle counts rather than continuously in time.

Answer: The difference is largest at 200 ALE cycles.

Answer: For the same number of ALE cycles, the thickness values at 200 °C are consistently higher than those at 300 °C. This difference is visible at intermediate and high cycle counts. The separation between the curves persists across the full range.

Answer: Plotting thickness versus cycle number allows direct tracking of material removal as processing proceeds. It provides a simple way to compare outcomes under different conditions. This is useful for assessing repeatability across cycles.

Answer: Yes, both techniques yield an etch rate of 0.46 Å/cycle at 300°C.

Answer: The slightly higher y-intercepts (~142 Å vs. 141 Å measured) result from mass gain during the nucleation period of the first ALE cycle.

Answer: No, the growth temperature does not affect the etch rate. Films grown at 200°C and 300°C both exhibit identical etch rates of 0.46 Å/cycle when etched at 300°C. This indicates the ALE process is determined by the etching temperature and chemistry, not the initial film deposition conditions.

Answer:
Open red circles: XRR measurements for Al₂O₃ grown at 300°C
Filled blue triangles: SE measurements for Al₂O₃ grown at 300°C
Open black squares: XRR measurements for Al₂O₃ grown at 200°C
Filled green triangles: SE measurements for Al₂O₃ grown at 200°C

Answer:
1. Begin an ALE cycle (HF/TMA exposures) on the Al₂O₃ film.

2. After the cycle completes, pause the process and allow conditions to stabilize.

3. Perform an SE measurement scan over a range of photon energies.

4. Fit the SE data with an optical model to extract the new film thickness.
This sequence integrates metrology directly into the process flow, enabling real-time, non-destructive monitoring of etch depth without breaking vacuum.

Answer: For sub-Å precision on a 20 Å film, 200°C is preferable. The slower rate provides the necessary resolution for fine trimming, despite the longer process time.

Answer: Higher temperature increases the etch rate. The fundamental reason is the increased thermal energy, which accelerates the kinetics of both the surface fluorination (HF) and ligand-exchange (TMA) reactions, allowing each cycle to remove material more completely and rapidly.

Answer: This capability allows precise tuning of a transistor's threshold voltage (Vₜ). The gate oxide thickness directly influences Vₜ; by using ALE to trim the Al₂O₃ dielectric layer by a few Ångströms, the Vₜ can be adjusted post-deposition to meet exact specifications, improving chip performance and yield.

Answer:
The initial Al2O3 films grown are
1. At 300 °C, it is 141 Å
2. At 200 °C, it is 170 Å

Answer: The film thickness from XRR versus number of ALE cycles yields an etch rate of 0.46 Å/cycle. Thenspectroscopic ellipsometry (SE) measurements on these same samples also yield an etch rate of 0.46 Å/cycle. In addition, the etch rates determined by XRR and SE are similar to the etch rate obtained by the in situ QCM experiments at at 300 °C.

Answer:
These slightly larger thicknesses originate from the mass gain that occurs during the nucleation
of the ALE process on the first ALE cycle.

Answer: Yes

Answer: 300 °C

Answer: Yes

Answer: 200 °C, 0 cycles.

Answer: By taking the thickness loss over a cycle interval and dividing by the number of cycles. From 0 to 200 cycles, 300 °C sample drops from 140 Å to 49 Å, so (140−49)/200=0.46 Å/cycle. At 200 °C, XRR gives (167−84)/200 = 0.42. SE measurement gives a slightly different result: (170−84)/200 = 0.43  Å/cycle.

Answer: For both temperatures, Al₂O₃ thickness decreases approximately linearly as the number of cycles increases. This indicates a steady removal of material per cycle rather than abrupt or saturating behavior.

Answer: X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE).

Answer: Yes

Answer: 200 °C, 300 °C

Answer: The etch rate is the same for both films, approximately 0.46 Å/cycle, showing that initial growth temperature does not affect ALE etch rate.

Answer: Film thickness by X-ray reflectivity (XRR), Film thickness by spectroscopic ellipsometry (SE), Refractive index (n ≈ 1.67–1.68)

Answer: Both XRR and SE measurements show a consistent linear decrease in Al₂O₃ thickness with ALE cycles, confirming the etch rate is uniform and independent of initial ALD film growth temperature. This consistency demonstrates that the ALE process can be reliably used for precise, controllable thinning of Al₂O₃ films in applications requiring accurate nanoscale thickness control.

Answer: Yes


Figure 6. Etched thickness of  $\mathrm{Al}_2\mathrm{O}_3$ ,  $\mathrm{SiO}_2$ , and  $\mathrm{Si}_3\mathrm{N}_4$  as a function of the number of etch cycles at  $460^{\circ}\mathrm{C}$ . The  $\mathrm{NbF}_5$  and  $\mathrm{CCl_4}$  pulse times are 3 and  $0.5\mathrm{~s}$ , respectively. The  $\mathrm{N}_2$  purge time was kept constant at 6 s.

The chart shows the etched thickness of Al2O3 (ALD), SiO2 (TOx), and Si3N4 (LPCVD) as a function of etch cycles. For  Al2O, the thickness increases linearly with etch cycles. For Si3N4 (LPCVD) and SiO2 (TOx), no etching is observed.

| etch cycles | etched thickness [nm] | Film |
|---|---|---|
| 1 | 0,40 | Al2O3 (ALD) |
| 60 | 5,49 | Al2O3 (ALD) |
| 100 | 12,19 | Al2O3 (ALD) |
| 149 | 17,05 | Al2O3 (ALD) |
| 0 | 0,51 | SiO2(TOx) |
| 60 | 0,48 | SiO2(TOx) |
| 100 | 0,44 | SiO2(TOx) |
| 150 | 0,44 | SiO2(TOx) |
| 0 | 0,32 | Si3N4(LPCVD) |
| 50 | 0,40 | Si3N4(LPCVD) |
| 100 | 0,44 | Si3N4(LPCVD) |
| 150 | 0,44 | Si3N4(LPCVD) |

Answer: 0.11 nm/cycle. The trendlineshown on the image is  y = 0.11x - 0.49. The slope of the line represents the rate of removal per cycle.

Answer: SiO2 and Si3N4.

Answer: EPC is constant (as the trendline is linear)

Answer: 98%

icdar2026-competition-data/dev/atomic-layer-etching/simulation-usecase/30/Thermal Atomic Layer Etching of Aluminum Oxide (Al2O3) Using Sequential Exposures of Niobium Pentafluoride.pdf