FIG. 5. Saturation curve of the  $\mathrm{CF}_4$  plasma dosage.

The figure presents a saturation curve showing how the etching-per-cycle rate increases sharply during the initial seconds of CF₄ plasma treatment and then gradually plateaus as the exposure time reaches 20 seconds. This indicates a self-limiting etching behavior characteristic of atomic layer processes.

| CF4 plasma treatment (s)|Etching per cycle (nm)|
|-------------------------|----------------------|
|0|0.00|
|5|0.20|
|10|0.25|
|20|0.24|

Answer: Understanding saturation helps ensure precise, self-limiting etching in ALE processes. By identifying the plasma dose at which etching stops increasing (~10 s), operators can optimize process time, reduce energy consumption, and avoid overexposure that may damage substrates. This allows tight control of etch depth and improves film uniformity and reproducibility in nanofabrication.

Answer:
At 5 s, the etching is ~0.20 nm/cycle;
at 10 s, it rises to ~0.25 nm/cycle;
at 20 s, it remains approximately unchanged (~0.24 nm/cycle), showing saturation.

Answer: Yes

Answer: Higher plasma dosage activates more reactive fluorine species, Increased activation enhances etching-per-cycle at lower times, Beyond ~10 s, all reactive sites saturate, As a result, etching-per-cycle plateaus.


FIG. 6. Saturation curve of the DMAC dosage.

The figure shows etching per cycle as a function of DMAC pulse time: etching increases rapidly at short pulse times and then approaches a plateau (~0.23–0.25 nm per cycle) beyond about 1 s, indicating saturation of the DMAC dosage.

| DMAC pulse time (s)|Etching per cycle (nm)|
|--------------------|----------------------|
|0.0|0.00|
|0.2|0.15|
|0.5|0.16|
|1.0|0.25|
|2.0|0.23|

Answer: The plateau indicates that after approximately 1 second of DMAC pulsing, the etching process reaches its maximum efficiency, meaning the surface becomes fully saturated and additional pulse time does not significantly enhance etching. This helps identify the optimal processing window where the reaction is both time-efficient and stable, avoiding unnecessary overexposure of DMAC.

Answer: The etching increases quickly at short pulse times but remains nearly constant at around 0.23–0.25 nm/cycle at longer times.

Answer: Yes

Answer: Self-limiting reaction behavior, Saturation of available reactive sites, Limited additional etching even with longer DMAC exposure

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


Fig.1. Etched amount of the blanket  $\mathrm{TiO_2}$  as a function of the  $\mathrm{CF_4}$  plasma treatment time (30 and 60 s).

The line chart shows the relationship between plasma treatment time (s) and the etched amount (nm), indicating a linear increase.

| plasma treatment (s) | etched amount (nm) |
|---|---|
| 0 | 0 |
| 15 | 2.58 |
| 30 | 6.6 |

Answer: Yes

Answer: The error bar spans nearly 1 nm or a 6.6 nm measurement. It is a non-negligible variation. This suggests that it might be difficult to precisely control the process at the angstrom level often required for device manufacturing.

Answer: It is not self-limiting. The linearity indicates this is a continuous etching process, where the amount removed is directly proportional to time. Self-limiting process would show a plateau after a certain time.

Answer: It stays roughly constant over time.

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


Fig. 4. Cyclic number dependence of the amount of blanket  $\mathrm{TiO_2}$  etching with cyclic  $\mathrm{C_4F_8}$  and  $\mathrm{O_2}$  plasma.

The chart shows a linear relationship between the number of cycles and the amount of blanket TiO2 etched (in nm), indicating a consistent increase with each cycle.

| Number of cycles | blanket TiO2 etched amount (nm) |
|---|---|
| 0 | 0 |
| 1 | 0.69 |
| 4 | 2.89 |
| 8 | 5.66 |
| 12 | 8.65 |

Answer: Accumulated process variations.

Answer: No

Answer: Approx. 0.71 nm/cycle.

Answer: It stays at approximately the same speed.


Fig. 5. CF polymer thickness on the blanket  $\mathrm{TiO_2}$  film for different  $\mathrm{C_4F_8}$  plasma treatment times.

The line chart shows the relationship between the duration of C₄F₈ plasma treatment (in s) and the thickness of the CF polymer formed (in nm), indicating a linear relationship between them.

| C₄F₈ plasma treatment time (s) | Thickness of CF polymer (nm) |
|---|---|
| 0 | 0 |
| 10 | 3.53 |
| 30 | 13.11 |
| 60 | 26.91 |

Answer: It stays roughly constant.

Answer: 30 seconds.

Answer: The approximate deposition rate is 0.46 nm/s (based on the slope).

Answer: No, it is not. If the process were self-limiting, the graph would rise and then plateau, once the surface is fully covered. The plot shows a linear increase, meaning the polymer continues to grow thicker and thicker indefinitely as long as the plasma is applied.


FIG. 3. (a) TiN ALE etch per cycle (EPC) vs substrate table temperature. (b) EPC vs  $\Omega_2$  gas exposure time with in situ HF exposure time fixed at  $10s$  at  $300^{\circ}C$  c) EPC vs in situ HF time with  $\Omega_2$  exposure time fixed at  $2s$  at  $300^{\circ}C$  The etch rates are observed to saturate with exposure time, demonstrating the self-limiting nature of the ALE process. The dashed lines are guides to the eye.

The etch rate increases with increasing temperature.

The etch rate increases with oxygen exposure time up to 2 seconds, then plateaus.

The etch rate increases with in-situ HF exposure time up to 15 seconds, then plateaus

| Temperature (°C) | Etch rate (Å/cycle) |
|---|---|
| 150 | 1.10 |
| 175 | 1.90 |
| 200 | 2.45 |
| 250 | 3.10 |
| 300 | 3.30 |
| 350 | 3.28 |

| Oxygen exposure time (s) | Etch rate (Å/cycle) |
|---|---|
| 0.0 | 0.10 |
| 0.5 | 1.65 |
| 1.0 | 2.40 |
| 2.0 | 2.95 |
| 4.0 | 2.95 |
| 6.0 | 2.92 |

| In-situ HF exposure time (s) | Etch rate (Å/cycle) |
|---|---|
| 0.0 | -0.20 |
| 1.0 | 0.55 |
| 2.5 | 1.25 |
| 5.0 | 2.30 |
| 10.0 | 3.05 |
| 15.0 | 3.10 |
| 20.0 | 3.05 |

Answer: 2 seconds for O2 gas exposure and 10 seconds for in-situ HF exposure, both at the onset of saturation.

Answer: The saturation curves demonstrate the self-limiting nature of both half-reactions in the ALE process. In subfigure (b), the oxidation step saturates because oxygen diffusion slows as the TiO2 layer thickens. In subfigure (c), the etching step saturates because the in-situ HF selectively removes only the TiO2 layer and stops when it reaches the underlying TiN. This dual self-limiting behavior is essential for achieving precise, reproducible etch depths with angstrom-scale control in each cycle.

Answer: The etch rate increases from 1.1 Å/cycle at 150°C to 3.2 Å/cycle at 300°C due to enhanced oxygen diffusion into TiN at higher temperatures, which produces thicker TiO2 layers during each oxidation step. Above 300°C, the etch rate plateaus because the oxide thickness becomes limited by factors other than diffusion kinetics, such as the thermodynamic stability of the oxide layer or surface reaction saturation. This plateau behavior is consistent with observations in other thermal ALE processes for TiN.

Answer: Approximately 3 Å/cycle.

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


Fig. 5. EPC versus temperature plot for the ALE of  $\mathrm{Al_2O_3}$  by 30 cycles of  $\mathrm{NF_3}$  remote plasma for  $4\mathrm{s}$  and TMA for  $3\mathrm{s}$ . The etching amount was determined by ellipsometry.

This line chart represents the Etch Per Cycle (EPC) Å/cycle for Atomic Layer Etching (ALE) of Al₂O₃ as a function of substrate temperature. The process uses cycles of NF₃ remote plasma followed by TMA exposure(3 s duration). EPC slowly increases with temperature up to a point (~250°C), then a rapid etch rate is observed and then stabilizes. This thickness loss was measured via ellipsometry.

| Substrate Temperature (°C) | Etch Per Cycle (Å/cycle) |
|----------------------------|--------------------------|
| 150                        | -0.1                     |
| 175                        | -0.1                     |
| 200                        |  0.0                     |
| 225                        |  0.4                     |
| 250                        |  1.4                     |
| 275                        |  2.6                     |
| 290                        |  3.8                     |
| 300                        |  4.2                     |
| 320                        |  4.6                     |

Answer:
Exposure to NF₃ remote plasma for 4 s to fluorinate the surface.

Exposure to TMA for 3 s to perform ligand exchange and remove the surface species.

Answer: The thermal ALE process is mandatory. A plasma-enhanced removal step (Ar⁺ sputter) causes physical bombardment damage, which would destroy the atomic lattice of graphene. The thermal TMA step in this process provides a chemically selective and gentle removal mechanism via volatile AlF₃ formation, enabling damage-free etching necessary for 2D materials, despite the low or moderate temperature requirement.

Answer: Higher temperatures typically increase the thermal energy available for diffusion and reaction.

Answer: NO, At 150°C, the EPC is very low (~0.5 Å/cycle) and is on the steep part of the curve. This means tiny temperature fluctuations in the reactor could cause significant percentage variations in the etch rate, destroying the atomic-scale depth control required. For reliable control, one must operate in the temperature-independent saturation regime (near 250-300°C) where the rate is stable.

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


Figure 4. (a) Etch rates for TiN versus  $\mathrm{O}_3$  exposure time with constant HF exposure time of  $1.0\mathrm{~s}$ . (b) Etch rates for TiN versus HF exposure time with constant  $\mathrm{O}_3$  exposure time of  $3.0\mathrm{~s}$ .

The etch rate increases with increasing O₃ exposure time at 250°C

The etch rate increases with increasing HF exposure time at 250°C

| O3 Exposure Time (s) | Etch Rate (Å/cycle) |
|---|---|
| 0.0 | 0.00 |
| 0.5 | 0.08 |
| 1.0 | 0.11 |
| 1.5 | 0.17 |
| 2.0 | 0.17 |
| 2.5 | 0.20 |
| 3.0 | 0.19 |
| 4.0 | 0.22 |

| HF Exposure Time (s) | Etch Rate (Å/cycle) |
|---|---|
| 0.0 | 0.00 |
| 0.5 | 0.14 |
| 0.75 | 0.18 |
| 1.0 | 0.19 |
| 1.25 | 0.20 |
| 1.5 | 0.21 |

Answer: The saturation behavior confirms that both half-reactions are self-limiting. The O₃ reaction self-terminates because the TiO₂ layer acts as a diffusion barrier preventing further oxidation. The HF reaction self-terminates because it can only remove the finite TiO₂ layer formed during oxidation—HF does not etch TiN directly.

Answer: Neither reactant alone etches TiN-O₃ only oxidizes the surface, and HF cannot etch TiN directly. Both half-reactions are required for etching.

Answer: Self-limiting behavior ensures that etch depth depends only on cycle count, not on precise exposure timing or local reactant concentration variations. This enables atomic-level thickness control and uniform etching across large wafers, which is essential for advanced device fabrication.

Answer: 3 s for O₃ and 1 s for HF, yielding the optimized sequence 3-30-1-30 (with 30 s N₂ purges).

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


Figure 13. Etch rates at  $170^{\circ}\mathrm{C}$  for  $\mathrm{TiO_2}$ : (a)  $\mathrm{BCl_3}$  with a constant  $\mathrm{WF_6}$  dose time of  $0.2\mathrm{s}$  and (b)  $\mathrm{WF_6}$  dose time with a constant  $\mathrm{BCl_3}$  exposure time of  $1\mathrm{s}$ . The ALE reactor was conditioned with  $200\mathrm{TiO_2}$  ALD cycles after every 3 subsequent ALE runs.

The figure characterizes the saturation behavior of a thermal Atomic Layer Etching (ALE) process for Titanium Dioxide , Etch rate as a function of BCl₃ dose time at 170 °C, showing clear saturation and self-limiting behavior characteristic of thermal ALE.

Etch rate as a function of WF₆ dose time at 170 °C, also exhibiting saturation, confirming that the TiO₂ etching process follows an ALE mechanism rather than continuous etching.

| BCl₃ Dose Time (s) | Etch Rate (Å/cycle) |
|------------------:|-------------------:|
| 0.0 | 0.00 |
| 0.1 | 0.44 |
| 0.5 | 0.65 |
| 1.0 | 0.68 |
| 1.5 | 0.72 |

| WF₆ Dose Time (s) | Etch Rate (Å/cycle) |
|-----------------:|-------------------:|
| 0.0 | 0.10 |
| 0.1 | 0.50 |
| 0.2 | 0.68 |
| 0.4 | 0.60 |
| 0.5 | 0.64 |

Answer:
1 .   WF₆ pulse: 0.2 s

, 2.   N₂ purge: 45 s

, 3.   BCl₃ pulse: 1.0 s

, 4.   N₂ purge: 45 s

Answer: At 0.1 s, the process operates in the unsaturated regime (the steep slope of the curve), where the etch rate is highly sensitive to small fluctuations in gas flow or pressure. In contrast, 1.0 s is in the saturated regime (plateau), where the rate is stable. Operating at 0.1 s risks severe non-uniformity, especially in high-aspect-ratio structures where gas diffusion is slow.

Answer: Chamber Memory Effect. Without conditioning, the reactant gases (WF₆ andBCl₃) would partially react with or adsorb onto the chamber walls instead of the sample, effectively lowering the partial pressure at the wafer surface. This would likely cause the saturation curves to shift to the right (requiring longer doses) or show artificially lower etch rates until the walls eventually became seasoned.

Answer: Surface Site Saturation. The surface is fully fluorinated (or modified) by the WF₆; once all available surface bonds have reacted, no further chemical modification can occur regardless of excess exposure, limiting the material removed in the subsequent step.

icdar2026-competition-data/train/atomic-layer-etching/experimental-usecase/46/Thermal Selective Vapor Etching of TiO2.pdf


Figure 6. (a) Thickness and (b) refractive index at  $632.8~\mathrm{nm}$  of samples with  $5.5\mathrm{nm}$ $\mathrm{TiO_2}$  followed by 0, 15, 25, 50, and  $100\mathrm{WF}_6$  doses at  $220^{\circ}\mathrm{C}$ , measured with spectroscopic ellipsometry. Lines are a guide to the eye.

This line chart represents the change in film thickness with increasing WF₆ doses at 220 °C, showing a linear decrease that indicates progressive etching or consumption of the 5.5 nm TiO₂ film.

This line chart represents the change in refractive index (at 632.8 nm) with increasing WF₆ doses, showing a sharp initial drop (0–25 doses) followed by stabilization at ~1.85, indicating initial chemical modification before steady-state etching.

| Number of WF₆ Doses | Thickness (Å) |
|--------------------:|--------------:|
| 0   | 56.00 |
| 10  | 58.64 |
| 25  | 53.11 |
| 50  | 50.34 |
| 100 | 33.71 |

| Number of WF₆ Doses | Refractive Index @ 632.8 nm |
|--------------------:|----------------------------:|
| 0   | 2.31 |
| 10  | 2.29 |
| 25  | 1.88 |
| 50  | 1.83 |
| 100 | 1.90 |

Answer:
Deposition: Deposition of a 5.5 nm TiO₂ starting layer.

Treatment: Exposure to a specific number of  WF₆ doses (0, 15, 25, 50, or 100) at 220°C.

Answer: Yes. The stepwise, dose-dependent index change allows spatial patterning of the refractive index by controlling the number of WF₆ doses across different regions of the waveguide. This enables the fabrication of gradient-index profiles for improved light confinement and mode shaping.

Answer: WF₆ fluorination is superior for independent control. It changes the index by altering composition while also thinning the film. Simply depositing a thinner film only changes thickness, not the intrinsic index. Fluorination offers two tuning knobs (dose for index, cycles for thickness).

Answer: WF₆ fluorinates the TiO₂, converting it into a titanium oxyfluoride (TiOFₓ) or fluoride. Fluorine incorporation increases the film's band gap and lowers its density/polarizability, both of which directly cause a decrease in the refractive index.


FIG. 7. Etch per cycle as a function of  $\mathrm{Cl}_2$  impacts from MD simulations.  $1000\mathrm{Ar}^+$  ion impacts are used for the ion bombardment step in every case. The energy of the  $\mathrm{Ar}^+$  ions is  $70\mathrm{eV}$ .

The scatter plot shows the relationship between the number of Cl₂ impacts and etch per cycle.  The EPC initially increases rapidly with chlorine dose due to incomplete surface coverage, then saturates beyond ~1000 Cl₂ i impacts at ~0.9 Å/cycle. This plateau demonstrates the self-limiting behavior of ideal atomic layer etching, where additional chlorine does not increase material removal once the surface is fully chlorinated.

| Number of Cl₂ Impacts | Etch per Cycle (Å/cycle) |
|----------------------|--------------------------:|
| 0                    | 14.52                     |
| 110                  | 0.53                      |
| 250                  | 0.68                      |
| 500                  | 0.84                      |
| 1000                 | 0.85                      |
| 2265                 | 0.89                      |
| 3000                 | 0.92                      |

Answer: Because 250 impacts is in the non-saturated region (steep slope). Small fluctuations in gas flow or pressure at this point would cause large changes in the etch rate. At 1500 impacts, the process is on the plateau (saturated), so it is robust against small variations.

Answer: Speed vs. Precision. The ALE process is extremely slow (only 0.9 Å per full cycle) compared to continuous etching. The trade-off is accepting low throughput to gain atomic-level precision and control.

Answer: Site Saturation. At 500 impacts, active surface sites are still available. By 2500 impacts, every available surface bond is already occupied by a Chlorine atom (saturated). Since no new Chlorine can stick, the subsequent ion etch cannot remove any additional material, leading to the plateau.

Answer: Spontaneous Etching. It would indicate that the excess Chlorine is beginning to etch the silicon chemically on its own (without ions), destroying the self-limiting behavior that defines Atomic Layer Etching.

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. 11. (a) The effect of the substrate velocity on the etching per cycle. (b) The effect of the moving substrate on etching per cycle to illustrate the uniformity of the etch.

A scatter plot showing the relationship between velocity (mm/s) and etching per cycle (Å/cycle). The etching decreases as the velocity increases.

A scatter plot showing the etching per cycle (Å/cycle) at different substrate positions (mm) for velocities of 80 mm/s, 120 mm/s, and 160 mm/s. The etching remains relatively constant across the substrate positions for each velocity.

| Velocity (mm/s) | Etching per cycle (Å/cycle) |
|---|---|
| 0 | 0.47 |
| 50 | 0.42 |
| 100 | 0.26 |
| 150 | 0.15 |

| Substrate position (mm) | Etching per cycle (Å/cycle) 80 |Etching per cycle (Å/cycle) 120 |Etching per cycle (Å/cycle) 160 |
|---|---|---|---|
| 0 | 0.36 | 0.22 | 0.1 |
| 0.1 | 0.36 | 0.22 | 0.1 |
| 0.2 | 0.36 | 0.22 | 0.1 |
| 0.3 | 0.36 | 0.22 | 0.1 |
| 0.4 | 0.36 | 0.22 | 0.1 |
| 0.5 | 0.36 | 0.22 | 0.1 |

Answer: With increasing velocity, the exposure time is decreasing. Usually long exposure times result in better uniformity.

Answer: The parameter that is changed is the dosing time or exposure time. The exposure time scales with 1/velocity.

Answer: The saturated EPC is 0.47 A/cycle, this is reached with a velocity below 40 mm/s.

Answer: 0.36 mm/s

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


Figure 10. Etch rate as measured by change in integrated absorbance of the  $\mathrm{Ti - O}$  vibrational modes from 400 to  $960~\mathrm{cm^{-2}}$  for each HF exposure. Temperature is varied from 80 to  $300^{\circ}C$

This line chart  plots the etch rate (measured by the loss of integrated Ti-O IR absorbance per HF exposure) against temperature (80-300°C) for a titanium-based film, showing that the etch rate increases with temperature.

| Temperature (°C) | Δ Int. Abs. Loss / HF Exposure |
|-----------------:|--------------------------------:|
| 80                | 0.00                            |
| 100              | 0.02                            |
| 120              | 0.05                            |
| 140              | 0.07                            |
| 160              | 0.25                            |
| 180              | 1.00                            |
| 200              | 1.10                            |
| 220              | 1.30                            |
| 240              | 1.90                            |
| 260              | 2.10                            |
| 280              | 2.50                            |
| 300              | 3.80                            |

Answer: The cut-off temperature is approximately 150°C. Below this point, the curve is effectively flat (close to zero on the Y-axis), indicating that the reaction kinetics are insufficient to remove material.Minimum Reactor Setting: To ensure the film is successfully etched, the user must set the reactor to a minimum of 150°C (or ideally higher, such as 175°C, for a practical rate). Any setting below 150°C results in negligible absorbance loss, meaning the process essentially fails to etch the film.

Answer: The low-temperature region is flat (low sensitivity), while the high-temperature region is steep (high sensitivity).At 300 °C, the etch rate is high, enabling fast throughput, but the process is highly sensitive to temperature variations; a ±5 °C deviation causes large fluctuations in etch rate. At 100 °C, the etch rate is stable but negligible. Thus, while intermediate temperatures may offer a trade-off, operation at 300 °C requires stringent thermal control.

Answer: Since infrared absorbance follows the Beer–Lambert law and is proportional to the number of bonds, a fourfold increase in absorbance loss indicates that approximately four times more TiO2  is removed per HF exposure at 300 °C than at 175 °C. This strong temperature dependence underscores the need for precise thermal control to ensure a stable etch rate.

Answer: At 250 °C, the etch rate shows strong temperature dependence; a 10 °C gradient (250 °C at the top vs. 240 °C at the bottom) would therefore cause slower etching at the bottom, leading to a tapered (V-shaped) profile. Achieving vertical sidewalls would require operation in a temperature-insensitive (saturated) regime, which is not observed here.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/20/Prediction and Validation of the Process Window for Atomic Layer Etching HF Exposure on TiO2.pdf


Figure 11. Arrhenius plot obtained from etch rates versus temperature presented in Figure 10. Slope of the plot yields an activation barrier of  $E_{\mathrm{a}} = 42\mathrm{kJ / mol}$ .

This figure is an Arrhenius plot (logarithm of etch rate vs. inverse temperature) derived from the data in Figure 10. The linear fit (a dashed line) yields an activation energy (Eₐ) of 42 kJ/mol for the HF etching reaction of the Ti-based film.

| 1000/T (K⁻¹) | ln[Δ Int. Abs. Loss / HF Exposure] |
|-------------:|------------------------------------:|
| 1.75         | 2.65                               |
| 1.80         | 2.50                               |
| 1.85         | 2.45                               |
| 2.00         | 2.05                               |
| 2.20         | 2.00                               |
| 2.35         | 1.30                               |
| 2.45         | 0.70                               |
| 2.55         | 0.75                               |
| 2.65         | 0.10                               |
| 2.80         | 0.25                               |

Answer: The key step is taking the natural logarithm of the etch rate (ln(k)) and plotting it against the inverse absolute temperature (1/T). This transformation linearizes the Arrhenius equation, allowing the activation energy (Eₐ) to be determined directly from the slope of the best-fit line (-Eₐ/R).

Answer:
Thermal HF Wet Etch: Pro: Selective, low damage. Con: Isotropic (etches in all directions).

Plasma-Enhanced Dry Etch: Pro: Can be highly anisotropic via ion bombardment.

Answer: An Eₐ of 42 kJ/mol (a relatively low value, ~0.44 eV) indicates the rate-limiting step is a surface chemical reaction with a moderate thermal barrier. It is not diffusion-limited (which would be lower, ~10-20 kJ/mol) nor a very high-energy bond-breaking process, suggesting a specific, activated chemisorption or ligand-exchange step controls the etch rate.

Answer: It enables predictable process tuning and scaling. Engineers can precisely calculate the temperature change needed to achieve a target etch rate (e.g., to meet throughput specs) or to maintain a constant rate despite equipment variations, ensuring reproducible results during high-volume manufacturing.


FIG. 6. Synergy plot for GaN using  $\mathrm{SF}_6$  plasma and TMA at  $300^{\circ}\mathrm{C}$ . The first 25 pulses only involve dosing  $\mathrm{SF}_6$  plasma, the next 25 pulses only TMA, and the last 75 cycles are full ALE cycles with both  $\mathrm{SF}_6$  plasma and TMA dosed. The inset shows the transition between only  $\mathrm{SF}_6$  pulses and only TMA pulses.

Synergy plot demonstrating self-limiting behavior of the GaN ALE process at 300°C. During SF6 plasma-only pulses (0-25), the film thickness remains constant after an initial ~0.7 nm drop. During TMA-only pulses (25-50), thickness is also constant. Full ALE cycles (50-125) show linear etching with EPC of 0.41 nm/cycle initially (oxidized layer) decreasing to 0.31 nm/cycle (bulk GaN).

Magnified view of the transition from SF6-only to TMA-only pulses, showing a 0.33 nm thickness decrease when TMA is first introduced, indicating that etching occurs during the TMA step.

| Pulses/Cycles | Film Thickness (nm) | Phase / Rate |
|---|---|---|
| 0 | 43.5 | Half-cycle A |
| 10 | 43.4 | Half-cycle A |
| 20 | 43.3 | Half-cycle A |
| 25 | 43.2 | Half-cycle A (End) |
| 26 | 42.9 | Half-cycle B (Start, -0.33 nm drop) |
| 40 | 42.7 | Half-cycle B |
| 50 | 42.5 | Half-cycle B (End) |
| 60 | 38.5 | ALE (~0.41 nm/cycle) |
| 70 | 34.5 | ALE |
| 80 | 31.5 | ALE (~0.31 nm/cycle) |
| 90 | 28.5 | ALE |
| 100 | 25.5 | ALE |
| 110 | 22.5 | ALE |
| 120 | 19.5 | ALE |
| 125 | 18.0 | ALE (End) |

Answer: The higher initial EPC corresponds to etching through the oxidized surface layer, while the lower EPC reflects etching of the more stoichiometric bulk GaN underneath.

Answer: 100%.

Answer: The synergy plot shows that neither SF6 plasma alone nor TMA alone causes continuous etching. The 0.33 nm thickness drop when switching from SF6-only to TMA-only pulses indicates that etching occurs during the TMA ligand-exchange step, which removes the fluorinated surface layer. Since no continuous etching is observed for either half-cycle individually, the process exhibits 100% synergy.

Answer: Removal of adventitious carbon, the heavily oxidized GaN surface layer, or changes in optical properties due to surface fluorination.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/27/Isotropic atomic layer etching of GaN using SF6 plasma and Al(CH3)3.pdf


FIG. 9. RMS roughness as a function of etched thickness, plotted alongside the fitted change in RMS roughness as obtained using the curvature-dependent model from Ref. 85.

RMS roughness evolution during GaN ALE at 300°C, comparing experimental data with a curvature-dependent smoothing model. Roughness decreases from ~2.6 nm to ~1.9 nm after 25 nm of etching. The rate of smoothing slows with increasing etch depth, in agreement with the model using a fitted diffusion parameter ε = 0.05×10⁻⁹ m.

| Etched thickness (nm) | RMS roughness (nm) |
|---|---|
| 0 | 2.8 |
| 5 | 2.4 |
| 10 | 2.2 |
| 15 | 2.0 |
| 20 | 1.9 |
| 25 | 1.8 |

Answer: The rate of smoothing decreases as the etched thickness increases. Initially, roughness drops rapidly from ~2.6 nm to ~2.2 nm within the first 10 nm of etching. Beyond this, the smoothing rate slows and begins to plateau. This behavior is captured by the curvature-dependent model, where high-curvature surface features etch faster initially, but as the surface becomes smoother, further improvement becomes more gradual.

Answer: It represents a measure of the fluorine diffusion rate into the GaN surface during the modification step.

Answer: GaN has a lower ε (0.05×10⁻⁹ m) compared to amorphous Al2O3 (1.50×10⁻⁹ m), indicating GaN is more resistant to fluorination.

Answer: Approximately 1.9 nm.


The scatter plot displays the variation in the nitrogen-to-silicon atomic ratio (N_N/N_Si) as a function of HF dose, expressed in HF/nm². Initially, the ratio begins around 1.3, then decreases to a minimum near 1.05 at approximately 80–100 HF/nm², before gradually increasing again toward the initial value. A fitted curve highlights this non-linear trend, suggesting that HF exposure initially disrupts nitrogen content before stabilizing or reversing the effect at higher doses. A horizontal dashed line serves as a reference level, possibly corresponding to the stoichiometric or ideal N_N/N_Si ratio prior to treatment.

| Dose (HF/nm²) | N_N/N_Si |
|---------------|----------|
| 0             | 1.3      |
| 20            | 1.2      |
| 40            | 1.15     |
| 60            | 1.10     |
| 80            | 1.05     |
| 100           | 1.07     |
| 120           | 1.12     |
| 140           | 1.18     |
| 160           | 1.22     |
| 180           | 1.26     |
| 200           | 1.3      |

Answer: As the HF dose increases from 0 to around 100 HF/nm², the N_N/N_Si ratio decreases, reaching a minimum, indicating a loss or displacement of nitrogen relative to silicon. Beyond this point, further HF exposure leads to a recovery in the N_N/N_Si ratio, suggesting re-equilibration or re-incorporation of nitrogen species. The resulting U-shaped trend suggests dose-dependent etching or modification behaviour.

Answer: Yes

Answer: Around 80–100 HF/nm².

Answer: Initial HF doses may deplete nitrogen content, a threshold dose exists where nitrogen loss peaks, higher doses may help restore or stabilise nitrogen levels

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/33/Atomistic Simulation of HF Etching Process of Amorphous.pdf


(b)

The scatter plot displays the etching yield of silicon nitride (Si₃N₄) as a function of the electronic input energy (Eₙ) during HF-based processing. As the input energy increases from 0 to 50 eV, the etching yield steadily rises in a nonlinear fashion. The data points are fit with a dashed curve, showing an accelerating increase, suggesting that higher Eₙ values significantly enhance the reaction efficiency. The inclusion of error bars indicates variability in the measurements, particularly at higher energies.

| $E_{\mathrm{in}}$ (eV) | Etching yield ($\mathrm{Si}_3\mathrm{N}_4$/HF) |
|---|---|
| 0.00 | 0.00 |
| 10.00 | 0.01 |
| 20.00 | 0.04 |
| 30.00 | 0.06 |
| 40.00 | 0.07 |
| 50.00 | 0.08 |

Answer: As the input energy increases from 0 to 50 eV, the etching yield of Si₃N₄ increases in a nonlinear manner. At low energies, the increase in yield is modest, but the trend becomes steeper at higher energies, indicating enhanced reaction kinetics or more efficient bond breaking with increasing Eₙ. This suggests that a threshold energy is required to initiate etching effectively, and further increases in Eₙ significantly boost the reaction rate.

Answer: Yes

Answer: Around 40 eV.

Answer: Higher Eₙ values result in greater etching yields, threshold below which etching is inefficient, Nonlinear increases suggest diminishing returns at very high energies.


Figure 4. Comparison of reaction energies during etching MD calculated using DFT  $(E_{\mathrm{rxn}}^{\mathrm{DFT}})$  and NNP  $(E_{\mathrm{rxn}}^{\mathrm{NNP}})$ . Each point refers to individual reactions. The density of data points on the color bar indicates the local density of reaction events in the vicinity of each point, accounting for the superposition of many data points.

The figure presents a parity plot comparing reaction energies computed via Density Functional Theory (DFT) and a Neural Network Potential (NNP) model. Each point represents a single reaction’s predicted energy from both methods, with the color intensity indicating the density of data points at that value. The data clusters tightly along the diagonal parity line (dashed), suggesting strong agreement between DFT and NNP predictions across a broad energy range (from -5 eV to 10 eV). This indicates that the NNP model is well-trained and capable of accurately reproducing DFT-level energetics for the evaluated reactions.

| $E_{\mathrm{rxn}}^{\mathrm{DFT}}$ (eV) | $E_{\mathrm{rxn}}^{\mathrm{NNP}}$ (eV) |
|---------------------------------------|----------------------------------------|
| -5                                    | -5                                     |
| -3                                    | -2.9                                   |
| 0                                     | 0.1                                    |
| 2                                     | 2.1                                    |
| 5                                     | 5.2                                    |
| 8                                     | 8.3                                    |
| 10                                    | 10                                     |

Answer: The plot indicates a strong linear correlation between the reaction energies predicted by the neural network potential (NNP) and those calculated via density functional theory (DFT). Most points cluster along the diagonal, which represents perfect agreement. This suggests that the NNP model closely replicates DFT-calculated values across a wide range of reaction energies, validating its reliability as a surrogate model for high-throughput or large-scale simulations.

Answer: Yes

Answer: Around 0 eV.

Answer: It can replace DFT in large-scale simulations with high accuracy, It provides significant computational speed-up while preserving fidelity.


Figure 4. Scatter plot showing the adsorption energy versus oxygen coverage of the minima shown in Figure 3. All of the points were fit to a parabola for eye-guiding purposes. The highlighted points are cross-referenced to the configurations shown in Figure 3. Brown, white, and red spheres represent carbon, hydrogen, and oxygen atoms, respectively.

The figure shows adsorption energy as oxygen coverage increases. At low coverage, adsorption is strongly favorable. Stable species such as H₂O are formed. At higher coverage, adsorption becomes less stable. New bonds form and the polymer structure begins to break.

| Coverage [O/nm²] | Adsorption Energy [eV/nm²] | Annotated chemical event |
|------------------|----------------------------|--------------------------|
| 0.5              | −2.02 (global minimum)     | Initial adsorption |
| 3.0              | −1.00 (local minimum)      | H₂O formation (O₅) |
| 6.8              | +0.10 (local maximum)      | O₂H compound formed (O₁₁) |
| 8.0              | +0.09                      | C–O–OH unstable state (O₁₃) |
| 9.0              | −0.21                      | Benzene ring rupture (O₁₄–O₁₅) |
| 9.5              | −0.20                      | C–O–C bridge bond formed (O₁₆) |
| 12.5             | −0.20                      | O₃ formation (O₁₉) |

Answer: At low oxygen coverage, reactions favor stable adsorption and low-energy products such as water. As coverage increases, the surface begins to form OH and peroxide-like species. At even higher coverage, the chemistry becomes destructive, leading to bond bridging, ozone formation, and ring rupture. This shows a transition from surface functionalization to surface damage.

Answer: Adsorption is more energetically favorable at low oxygen coverage.

Answer: The appearance of C–O–C bridges and benzene ring rupture indicates that the polymer backbone is being altered. These reactions go beyond surface functionalization and involve structural damage. This suggests reduced mechanical and chemical stability at high oxygen loading.

Answer: In surface treatment processes, controlled functionalization is often desired without damaging the material. This figure shows that excessive oxygen leads to polymer degradation. Identifying the onset of ring rupture helps define safe processing limits. This is critical for plasma and oxidative treatments of polymers.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/35/Density Functional Theory Study of Oxygen Adsorption on Polymer Surfaces for Atomic-Layer.pdf


FIG. 15. Normalized atomic Cl counts as a function of  $\mathsf{Ar}^+$  fluence. Subfigure (a) shows the results for OES experiments (where the ion energy is estimated to be about  $85\mathrm{eV}$ ) and subfigure (b) shows results from MD ALE simulations where the ion energy is  $80\mathrm{eV}$ . In both cases, the results are normalized using the value observed at the peak.

The experimental scatter plot shows a sharp decrease in Cl count with increasing ion dosage up to about 10–15 × 10¹⁵ Ar⁺/cm². After that, the count levels off around 0.5 arb. units, suggesting that most Cl atoms have been desorbed or sputtered and that the system has reached a steady state.

The MD simulation results mirror this trend but show a steeper and more sustained decline. Initial Cl counts are slightly higher in simulation, but decrease more rapidly, falling below 0.2 arb. units by 50 × 10¹⁵ Ar⁺/cm². The more aggressive decline in simulations may reflect idealized surface models with fewer defect traps or re-adsorption pathways

| Ion Dosage (Ar⁺/cm²) × 10¹⁵ | Cl Count (arb. units)  |
|-----------------------------|------------------------|
| 0                           | 1.20                   |
| 2                           | 1.00                   |
| 4                           | 0.90                   |
| 6                           | 0.80                   |
| 8                           | 0.70                   |
| 10                          | 0.65                   |
| 12                          | 0.60                   |
| 14                          | 0.58                   |
| 16                          | 0.55                   |
| 18                          | 0.53                   |
| 20                          | 0.52                   |
| 25                          | 0.51                   |
| 30                          | 0.50                   |
| 35                          | 0.50                   |
| 40                          | 0.50                   |
| 45                          | 0.50                   |
| 50                          | 0.50                   |

| Ion Dosage (Ar⁺/cm²) × 10¹⁵ | Cl Count (arb. units)  |
|-----------------------------|------------------------|
| 0                           | 1.60                   |
| 2                           | 1.20                   |
| 4                           | 1.00                   |
| 6                           | 0.80                   |
| 8                           | 0.65                   |
| 10                          | 0.55                   |
| 12                          | 0.48                   |
| 14                          | 0.42                   |
| 16                          | 0.38                   |
| 18                          | 0.34                   |
| 20                          | 0.30                   |
| 25                          | 0.27                   |
| 30                          | 0.24                   |
| 35                          | 0.22                   |
| 40                          | 0.20                   |
| 45                          | 0.19                   |
| 50                          | 0.18                   |

Answer: Cl desorption, Surface sputtering, Bond breakage, Cl depletion over time

Answer: In both the experimental and simulation results, Cl count decreases as ion dosage increases. The experimental data shows a rapid initial drop followed by a plateau near 0.5 arb. units, indicating surface saturation or depletion. In contrast, simulations exhibit a sharper and more sustained decline, reaching much lower final values. This suggests that Cl is more easily removed in the idealized simulation environment, while experimental surfaces may retain Cl due to surface defects or incomplete reactions.

Answer: Around 15 × 10¹⁵ Ar⁺/cm²

Answer: Yes

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/6/Dynamics of plasma atomic layer etching Molecular.pdf


The line chart illustrates the relationship between film thickness and pulses/cycles, showing a decreasing trend if both reactants are dosed.

| Pulses/Cycles | Film thickness (nm) |
|---|---|
| 0 | 43 |
| 25 | 43 |
| 50 | 42 |
| 75 | 33 |
| 100 | 25 |
| 125 | 18 |

Answer: At 25 pulses/cycles the SF6 plasma dosing is switched with TMA dosing, here a drop of 0.33 nm is observed. So based on this part of the graph the EPC is 0.33 nm.

Answer: It could be that there are temperature differences as an higher temperature can main a higher EPC.

Answer: It could be that the flurination step increases the thickness slightly with the incorporation of fluorine.

Answer: It requires roughly 30 cycles.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/8/Isotropic atomic layer etching of GaN using SF6 plasma and AI(CH3)3.pdf


The line chart shows the relationship between etched thickness and RMS roughness, with experimental data points and a curvature-dependent model curve.

| Etched thickness (nm) | RMS roughness (nm) |
|---|---|
| 0 | 2.65 |
| 5 | 2.4 |
| 10 | 2.2 |
| 15 | 2.0 |
| 20 | 2.0 |
| 25 | 1.9 |

Answer: It could be that there is dust incorporated in the film or the deposition method with which the GaN is made is not uniform.

Answer: This is not likely, even for infinite etch thickness, a material can never be perfectly flat.

Answer: At least 20 nm must be etched away.

Answer: Yes


Fig. 3. (a) Potential energy curve for  $\mathrm{SiCl_2}$  on the optimized Si(111) surface, here blue dots are the calculated data, and red line is the fitting function.  $Z = 0$  represents the equilibrium position, and insets are the local views of the desorbed species. (b) Potential energy curve for the Si-adatom (atom A1 in Fig. 2(a)) in the absence of chlorine, insets are the local views of the desorbed species.

The figure shows a potential energy curve as a function of surface coordinate Z, with calculated data points and a fitted line for the desorption of a SiCl2 unit.

The figure shows a potential energy curve as a function of surface coordinate Z, with calculated data points and a fitted line for the desorption of a rest silicon atom.

| Surface coordinate Z (Å) | Potential energy (eV) |
|---|---|
|-1 | 8 |
|-0.5 | 1.2 |
|0 | 0 |
|0.5 | 0.8 |
|1 | 1.5 |
|1.5 | 2.2 |
|2 | 2.4 |
|2.5| 2.5|

| Surface coordinate Z (Å) | Potential energy (eV) |
|---|---|
|-1 | 8 |
|-0.5 | 1 |
|0 | 0 |
|0.5 | 0.5 |
|1 | 2 |
|1.5 | 3.2 |
|2 | 4.3 |
|2.5|5.2|

Answer: In principle can silicon be etched continuously, however an energy of 6.1832 eV is required per silicon atom to do this.

Answer: 6.1832 eV

Answer: The SiCl2 unit has zero potential energy when it is in a standing up position on the surface.

Answer: The desorption energy is 2.5159 eV which is provided by energetic ions from the argon plasma.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/9/Mechanism of photoassisted atomic layer etching of chlorinated Si(111) surfaces Insight.pdf