FIG. 10. Fluxes to the wafer as a function of radius for the  $\mathrm{Ar / c - C_4F_8}$  CCP. (a) Neutral and (b) ion fluxes.  $\mathrm{CF}_3$ ,  $\mathrm{C}_3\mathrm{F}_5$ , and  $\mathrm{F}$  are the dominant radicals.  $\mathrm{Ar^{+}}$ ,  $\mathrm{C}_2\mathrm{F}_4^+$ , and  $\mathrm{CF}_x^+$ $(x = 1 - 3)$  are the dominant ions.

The figure shows the neutral flux of various species as a function of radius of the wafer.

The figure displays the ion flux of ions as a function of radius of the wafer.

| Species | Radius (cm) | Neutral Flux ($10^{17}$ cm$^{-2}$s$^{-1}$) |
|---|---|---|
|CF3 | 0 | 5.82 |
|CF3 | 4 | 5.82 |
|CF3 | 10 | 5.88|
|CF2 | 0 | 4.57 |
|CF2 | 4 | 4.59 |
|CF2 | 10 | 4.61|
|CF | 0 | 4.3 |
|CF | 4 | 4.26 |
|CF | 10 | 4.28 |
|C2F6 | 0 | 2.66 |
|C2F6 | 4 | 2.68 |
|C2F6 | 10 | 2.74 |
|C3F5 | 0 | 1.77 |
|C3F5 | 4 | 1.75 |
|C3F5 | 10 |1.77 |
|C4F7 | 0 | 1.46 |
|C4F7 | 4 | 1.46|
|C4F7 | 10 | 1.46 |
|C2F4 |  0 | 0.91 |
|C2F4 |  4 | 0.89 |
|C2F4 |  10 | 0.91 |
|CF4 | 0 | 0.78 |
|CF4 | 4 | 0.68|
|CF4 | 10 | 0.48 |
|F | 0 |0.68 |
|F | 4 | 0.68 |
|F | 10 | 0.72 |

| Species | Radius (cm) | Ion Flux ($10^{15}$ cm$^{-2}$s$^{-1}$) |
|---|---|---|
| Ar+ | 0 | 12.9 |
| Ar+ | 4 | 16.7 |
| Ar+ | 10 | 18.2 |
|C2F4+ | 0 | 8.5 |
|C2F4+ | 4 | 10.1 |
|C2F4+ | 10 | 9.7 |
|C3F5+ | 0 | 4.9 |
|C3F5+ | 4 | 6.7 |
|C3F5+ | 10 | 6.6 |
|CF+ + CF2+ + CF3+ | 0 | 3.8 |
|CF+ + CF2+ + CF3+ | 4 | 5.6 |
|CF+ + CF2+ + CF3+ | 10 | 5.4 |
|Ar+ (Step 2) | 0 | 2.3 |
|Ar+ (Step 2) | 4 | 2.2 |
|Ar+ (Step 2) | 10 | 2.2 |
|F +  | 0 | 0.5 |
|F +  | 4 | 0.45 |
|F + | 10 | 0.39 |

Answer: The argon ion is the primary species responsible for the non-uniformity observed near the edge of the wafer. The fluxes of other ions remain relatively flat across the radius. The argon ion flux exhibits a distinct rise from the center to the edge of the wafer.

Answer: CF3.

Answer: At ~ 5 cm.

Answer: CF4, C2F6 and C2F4.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/19/Plasma atomic layer etching using conventional plasma equipment.pdf


FiG. 16. Fluxes to the wafer as a function of radius for the nonsinusoidal bias PALE process. (a) Neutral and (b) ion fluxes.  $\mathrm{CF}_2$  CF,and  $\mathrm{CF}_3$  are the dominant fluorine containing neutral radicals.  $\mathrm{Ar^{+}}$ $\mathrm{CF}_3^+$ $\mathrm{CF}_2^+$  and  $\mathrm{CF^{+}}$  are the dominant ion fluxes.

The figure shows the neutral flux of various species as a function of wafer radius (0 - 6 cm).The flux is dominated by CF3 radical.

The figure shows the ion flux of various species as a function of of wafer radius (0 - 6 cm). The flux is dominated by Ar(+).

| Radius (cm) | CF2 flux (10¹⁷ cm⁻² s⁻¹) | CF flux (10¹⁷ cm⁻² s⁻¹) | C flux (10¹⁷ cm⁻² s⁻¹) | CF3 (×2) flux (10¹⁷ cm⁻² s⁻¹) | C2F3 (×2) flux (10¹⁷ cm⁻² s⁻¹) | F (×2) flux (10¹⁷ cm⁻² s⁻¹) | C2F4 (×2) flux (10¹⁷ cm⁻² s⁻¹) | C2F5 (×2) flux (10¹⁷ cm⁻² s⁻¹) |
|---|---|---|---|---|---|---|---|---|
| 0 | 5.75 | 3.75 | 2.82 | 1.65 | 1.25 | 0.9 | 0.45 | 0.3 |
| 3 | 5.64 | 3.79 | 2.68 | 1.61 | 1.34 | 0.82 | 0.51 | 0.32 |
| 6| 5.79 | 4.12 | 2.53 | 1.54 | 1.75 | 0.63 | 0.63 | 0.33 |

| Radius (cm) | Ar+ flux (10¹⁵ cm⁻² s⁻¹) | CF3+ flux (10¹⁵ cm⁻² s⁻¹)  | CF2+ flux (10¹⁵ cm⁻² s⁻¹)  | CF+ flux (10¹⁵ cm⁻² s⁻¹)  | C2F4+ flux (10¹⁵ cm⁻² s⁻¹)  | C2F5+ + C3F5+ flux (10¹⁵ cm⁻² s⁻¹)  | F+ flux (10¹⁵ cm⁻² s⁻¹) |
|---|---|---|---|---|---|---|---|
| 0 | 7 | 3.5 | 2.6 | 2.4 | 0.52 | 0.52 | 0.12 |
| 3 | 6 | 2.9 | 2.3 | 2.14 | 0.52 | 0.52 | 0.07 |
| 6 | 4.6 | 2.6 | 1.75 | 1.75 | 0.52 | 0.52 | 0.07 |

Answer: Ar(+).

Answer: C2F5(+) + C3F5(+), C2F4(+), CF(+), CF2(+), CF3(+), Ar(+)

Answer: At the center of the wafer (r = 0 cm).Since physical sputtering is driven by the bombardment of ions, the region receiving the highest flux of heavy Argon ions will experience the most intense sputtering. The Ar(+) flux shows its peak at the center of the wafer and decreases towards the edge.

Answer: CF2, CF, C, C2F3, CF3, F, C2F4, C2F5


FIG. 3. (Color online) Ion properties for the PALE cycle. (a) Ion fluxes to the wafer as a function of radius.  $\mathrm{Cl}^+$  is the major ion during step 1 (passivation) due to dissociation of the  $\mathrm{Cl}_2$  feedstock. The  $\mathrm{Ar^{+}}$  flux is higher during step 2 (etching) step due to lack of any competing processes. (b) Total IEDs averaged over the wafer. Low ion energies are necessary to minimize etching during step 1 while higher ion energies in step 2 enable etching of the  $\mathrm{SiCl}_x$  passivation. (IEADs are plotted using a log scale over 2 decades.)

The  chart shows the ion flux of different ions (Ar+, Cl+, and Cl2+) for step 1 (passivation) and step 2(etching) at various radii from the center of the wafer.

The heatmap displays the ion energy and angular distribution (IEAD) for step 1 (passivation).

The heatmap displays the ion energy and angular distribution (IEAD) for step 2 (etching).

| Radius (cm) | Ion Flux (1016 cm-2s-1) | Species|
|---|---|---|
| 0 | 7.93 | Ar (+) Step 2|
| 3 | 7.27 | Ar (+) Step 2|
| 6 | 5.18 | Ar (+) Step 2|
| 0 | 1.35 | Ar (+) Step 1|
| 3 | 1.2 | Ar (+) Step 1|
| 6 | 0.7 | Ar (+) Step 1|
| 0 | 3.6 | Cl (+) Step 1|
| 3 | 3.1 | Cl (+) Step 1|
| 6 | 1.89 | Cl (+) Step 1|
| 0 | 0.5 | Cl2(+) Step 1|
| 3 | 0.5 | Cl2(+) Step 1|
| 6 | 0.5 | Cl2(+) Step 1|

| Angle (deg) | Energy (eV) | Intensity |
|---|---|---|
| -15 | 14 | 0.01 |
| 0 | 14 | 0.01 |
| 15 | 14 | 0.01 |
| -15 | 16 | 0.69|
| 0 | 16 | 0.69 |
| 15 | 16 | 0.36 |
| -15 | 17 | 0.69 |
| 0 | 17 | 1 |
| 15 | 17 | 0.36 |
| -15 | 21 | 0.01 |
| 0 | 21 | 0.01 |
| 15 | 21 | 0.01 |

| Angle (deg) | Energy (eV) | Intensity |
|---|---|---|
| 0 | 42 | 0.01 |
| 0 | 51 | 0.85 |
| -9 | 51 | 0.01 |
| 9 | 51 | 0.01|
| 0 | 57 | 1 |
| 9 | 57 | 0.01 |
| -9 | 57 | 0.01 |
| 0 | 61 | 0.01 |
| 9 | 17 | 0.01 |
| -9 | 21 | 0.01 |

Answer: Cl (+).

Answer: Cl2 (+).

Answer: Perpendicular to the wafer surface (0 degrees).

Answer: ~ ± 10 degrees.


Figure 3. Various contributions to the reaction FEP for the CVE1 reaction of  $\mathrm{TiO}_2 + \mathrm{HF}\rightarrow \mathrm{TiF}_4 + \mathrm{H}_2\mathrm{O}$  at an HF reactant pressure of 0.2 Torr.

This figure plots the thermodynamic contributions to the reaction free energy profile (FEP) for the etching reaction TiO₂(bulk) + 4HF(g) → TiF₄(g) + 2H₂O(g) as a function of temperature (0–800 K) at a constant HF pressure of 0.2 Torr. It shows how the electronic energy (ΔE), zero-point correction (ΔE+ΔZPE), Gibbs free energy (ΔG), and entropic term (TΔS) evolve with temperature.

| Temperature [K] | E [eV / TiO2] |  |
|---|---|----|
| 0    | -1.4 | ΔE |
| 0    | -1.2 | ΔE + ΔZPE |
| 0    | -1.2 | ΔG |
| 0    | 0.0  | TΔS |
| 0    | 0.0  | ΔW |
| 0    | 0.0  | RT ln(Q) |
| 200  | -1.4 | ΔE |
| 200  | -1.2 | ΔE + ΔZPE |
| 200  | -1.2 | ΔG |
| 200  | -0.1 | TΔS |
| 200  | -0.03  | ΔW |
| 200  | -0.01  | RT ln(Q) |
| 400  | -1.4 | ΔE |
| 400  | -1.2 | ΔE + ΔZPE |
| 400  | -1.1 | ΔG |
| 400  | -0.2 | TΔS |
| 400  | -0.1 | ΔW |
| 400  | -0.02  | RT ln(Q) |
| 600  | -1.4 | ΔE |
| 600  | -1.2 | ΔE + ΔZPE |
| 600  | -1.0 | ΔG |
| 600  | -0.4 | TΔS |
| 600  | -0.1 | ΔW |
| 600  | -0.04  | RT ln(Q) |
| 800  | -1.4 | ΔE |
| 800  | -1.2 | ΔE + ΔZPE |
| 800  | -0.8 | ΔG |
| 800  | -0.6 | TΔS |
| 800  | -0.1 | ΔW |
| 800  | -0.1 | RT ln(Q) |
| 1000 | -1.4 | ΔE |
| 1000 | -1.2 | ΔE + ΔZPE |
| 1000 | -0.7 | ΔG |
| 1000 | -0.7 | TΔS |
| 1000 | -0.2 | ΔW |
| 1000 | -0.1 | RT ln(Q) |

Answer: Yes, it is spontaneous. At 300 K, the Gibbs free energy (ΔG) is approximately −1.2 eV, and a negative ΔG indicates a spontaneous reaction.

Answer: 700 K is better for ensuring spontaneity (more negative ΔG). The trade-off is the higher thermal budget, which may damage temperature-sensitive materials or increase energy costs, whereas 400 K offers lower thermal stress but may result in a non-spontaneous or slower etch rate.

Answer: ΔG becomes more negative (more spontaneous) as temperature increases. This is primarily driven by the large, positive TΔS term (entropy gain) due to the production of gas-phase molecules (TiF₄ and H₂O) from a solid and gas, which outweighs the endothermic enthalpy contribution at higher temperatures.

Answer: This implies that HF gas etching of TiO₂ is not feasible at room temperature (ΔG > 0). To enable etching, the process must be heated above ~500 K, or an alternative, more reactive chemistry (e.g., plasma activation) must be used to lower the kinetic barrier and drive the reaction at lower temperatures.

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 4. FEPs for the CVE1, CVE2, CVE3, SL1 SL2, and SL3 reactions for HF interacting with  $\mathrm{TiO_2}$  versus temperature. The labels X and Y correspond to the values listed in Table 1.

This multiple line chart image compares the free energy profiles (FEPs) of three Continuous Vapor Etching (CVE) reactions (red, red-dashed, blue) with their corresponding self-limiting (SL) surface modification reactions (green, green-dashed, yellow). For ideal Atomic Layer Etching (ALE), the SL reaction must be spontaneous (ΔG < 0) while the CVE reaction remains non-spontaneous (ΔG > 0), defining a “Goldilocks” window where the surface is modified but bulk etching is suppressed.

| Temperature [K] | ΔG [ev / TiO2] | Materials |
|--------|---------|---------|
| 0    | -1.2 | CVE1(Y1) |
| 0    | 2.1  | CVE2(Y2) |
| 0    | 2.2  | CVE3(Y3) |
| 0    | -2.2 | SL1(X1) |
| 0    | -1.1 | SL2(X2) |
| 0    | -0.1 | SL3(X3) |
| 200  | -1.2 | CVE1(Y1) |
| 200  | 1.7  | CVE2(Y2) |
| 200  | 1.9  | CVE3(Y3) |
| 200  | -1.6 | SL1(X1) |
| 200  | -0.8 | SL2(X2) |
| 200  | 0.2  | SL3(X3) |
| 400  | -1.1 | CVE1(Y1) |
| 400  | 1.4  | CVE2(Y2) |
| 400  | 1.7  | CVE3(Y3) |
| 400  | -0.9 | SL1(X1) |
| 400  | -0.5 | SL2(X2) |
| 400  | 0.6  | SL3(X3) |
| 600  | -1.0 | CVE1(Y1) |
| 600  | 1.1  | CVE2(Y2) |
| 600  | 1.4  | CVE3(Y3) |
| 600  | -0.3 | SL1(X1) |
| 600  | -0.2 | SL2(X2) |
| 600  | 1.0  | SL3(X3) |
| 800  | -0.8 | CVE1(Y1) |
| 800  | 0.9  | CVE2(Y2) |
| 800  | 1.2  | CVE3(Y3) |
| 800  | 0.3  | SL1(X1) |
| 800  | 0.1  | SL2(X2) |
| 800  | 1.3  | SL3(X3) |
| 1000 | -0.7 | CVE1(Y1) |
| 1000 | 0.6  | CVE2(Y2) |
| 1000 | 1.0  | CVE3(Y3) |
| 1000 | 0.9  | SL1(X1) |
| 1000 | 0.4  | SL2(X2) |
| 1000 | 1.6  | SL3(X3) |

Answer:
CVE1: 4 HF molecules.

CVE2: 2 HF molecules.

CVE3: 3 HF molecules.

Conclusion: CVE1 consumes the most reactant (4 HF).

Answer: The CVE2 pathway is not viable for a spontaneous, continuous etch. Its ΔG remains positive (non-spontaneous) across the entire temperature range shown, unlike CVE1 which becomes favorable above ~700 K. To achieve continuous etching, one must use conditions that favor CVE1, accepting a higher thermal budget.

Answer: A CVE pathway produces volatile gas-phase products (e.g., TiF₄(g)), leading to complete material removal. An SL pathway produces a modified, non-volatile surface layer (e.g., TiF₄(surf)). The SL reactions are always more exothermic (more negative ΔE) than their CVE counterparts because forming a surface layer is energetically cheaper than completely breaking bonds to release gas molecules.

Answer: This implies that isotropic, continuous etching of TiO₂ with HF gas requires a high-temperature process (>700K). At lower temperatures, the reaction will self-limit, only modifying the surface. Therefore, for patterning, one must either operate at high temperature or use an alternative activation method (like plasma) to drive the CVE pathway at lower temperatures.


Figure 5. FEPs of CVE1 and SL1 showing three regions: preferred self-limiting, preferred etching, and purely etching. SL1 and CVE1 line crossing occurs at  $360~\mathrm{K}$ $(87^{\circ}\mathrm{C})$

This figure plots the Free Energy Profiles (FEPs) for the CVE1 (continuous vapor etch) and SL1 (self-limiting surface reaction) pathways for HF interacting with TiO₂. The lines cross at 360 K, defining three regimes: below 360 K, SL1 is favored (self-limiting); between 360 K and ~700 K, CVE1 becomes progressively more favored (preferred etching); above 700 K, CVE1 is strongly favored (purely etching).

| Temperature [K] | ΔG [eV / TiO2] | Label    | Region                |
|-----------------|---------------------------|----------|-----------------------|
| 0               | -2.2                      | SL1(X1)  | Preferred self-limiting |
| 0               | -1.1                      | CVE1(Y2) | Preferred self-limiting |
| 200             | -1.5                      | SL1(X1)  | Preferred self-limiting |
| 200             | -1.1                      | CVE1(Y2) | Preferred self-limiting |
| 400             | -0.9                      | SL1(X1)  | Preferred etching       |
| 400             | -1.0                      | CVE1(Y2) | Preferred etching       |
| 600             | -0.3                      | SL1(X1)  | Preferred etching       |
| 600             | -0.9                      | CVE1(Y2) | Preferred etching       |
| 800             | 0.2                       | SL1(X1)  | Purely etching          |
| 800             | -0.8                      | CVE1(Y2) | Purely etching          |
| 1000            | 0.8                       | SL1(X1)  | Purely etching          |
| 1000            | -0.7                      | CVE1(Y2) | Purely etching          |

Answer: Max Temperature: 360 K (87°C).Above 360 K, the preference switches; the bulk etching reaction (CVE1) becomes more energetically favorable than the surface modification (SL1).

Answer:
300 K (Self-limiting regime): Pro: Excellent depth control, atomic-layer precision. Con: Very slow or negligible material removal rate.
800 K (Purely etching regime): Pro: High etch rate, fast throughput. Con: Poor depth control, isotropic etching.
Trade-off: The choice is between controllability (low temp) and throughput (high temp). For precise patterning, a low-temperature, self-limiting process is necessary, sacrificing speed.

Answer: The shift is driven by entropy. The CVE1 pathway produces more gas molecules, granting it a larger, favorable entropy term (+TΔS). As temperature rises, this term dominates the free energy (ΔG = ΔH - TΔS), making the complete volatilization reaction (CVE1) increasingly favorable over the surface passivation reaction (SL1).

Answer: Yes, it should be operated below 360 K. The SL1 pathway is thermodynamically favored over CVE1. This makes the reaction inherently self-limiting, as it preferentially forms a stable surface layer rather than volatile products, ensuring precise, layer-by-layer removal essential for controlled etching.


FIG. 5. EPCs of Si PA-ALE processes obtained from MD simulations as functions of  $\mathrm{Ar^{+}}$  ion incident energy. The solid and dashed lines represent those for the thin and thick Cl layer deposition cases. Other ALE conditions are listed in Table I. The value of EPC given here is the average of etched depths per cycle from C3 to C6.

The line chart illustrates the relationship between Ar+ ion incident energy (in eV) and etch per cycleEPC (in Å) for thin and thick Cl layer deposition methods.

| Energy (eV) | Thin Cl layer deposition (Å) | Thick Cl layer deposition (Å) |
|-------------|-------------------------------|--------------------------------|
| 0           | 0                             | 0                              |
| 10          | 1                             | 2                              |
| 20          | 2                             | 4                              |
| 30          | 4                             | 6                              |
| 40          | 7                             | 10                             |
| 50          | 11                            | 14                             |
| 60          | 16                            | 19                             |

Answer: The value of EPC given here is the average of etched depths per cycle from C3 to C6.

Answer: Yes

Answer: Because from the image, it can be seen that the EPC is higher in the thick Cl layer deposition case than in the thin Cl layer deposition case

Answer:
At 20 eV Ar+ ion energy, the EPC correspond to Si monolayer as follows
1. The simulated EPCs  for thin Cl layer deposition is  1.6  Å/cycle = 1.2 Si Monolayer/cycle
2. The simulated EPC for thick Cl layer deposition is 4.2 Å/cycle = 3 Si Monolayer/cycle.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/26/Surface damage formation during atomic layer etching of silicon with chlorine adsorption.pdf


FIG. 7. Thicknesses of damaged-layers formed during the Si PA-ALE processes, obtained from MD simulations, as functions of the  $\mathrm{Ar^{+}}$  ion incident energy. The solid and dashed lines represent those for thin and thick Cl layer deposition cases. Other ALE conditions are listed in Table I. The value of the thickness here is the average of those over all six cycles, i.e., from C1 to C6.

The chart shows the relationship between energy (in eV) and thickness (in nm) for thin and thick Cl layer depositions.

| Energy (eV) | Thin Cl layer deposition (nm) | Thick Cl layer deposition (nm) |
|-------------|--------------------------------|---------------------------------|
| 0           | 0.0                            | 0.0                             |
| 10          | 0.8                            | 0.9                             |
| 20          | 1.5                            | 1.7                             |
| 30          | 1.8                            | 2.0                             |
| 40          | 2.0                            | 2.0                             |
| 50          | 1.8                            | 2.1                             |
| 60          | 1.8                            | 2.3                             |

Answer: No

Answer: The damaged-layer thickness observed here is significantly higher than the corresponding EPC at 20 eV ion energy and comparable at 60 eV

Answer:
It can be concluded that, for both thin and thick Cl layer deposition cases, the damaged-layer thicknesses weakly and more-or-less linearly increase with the increasing incident ion energy in the energy range studied here. With an increasing ion incident energy, the penetration depths of Arþ ions and recoiled Cl atoms increase but so do the etch rates. In other words, a large part of the damaged-layer formed during the desorption step is etched away at high ion incident energy. It is
also seen that the damaged-layer is slightly thicker in the thick Cl layer deposition case.

Answer:
The damaged-layer thickness was averaged over the first six cycles (i.e., from C1 to C6)
under each ALE condition


FIG. 9. Numbers of desorbed species as functions of the  $\mathsf{Ar^{+}}$  ion dose during the desorption step of the 6th cycle (C6) of Si PA-ALE processes. The ALE conditions are the same as those in Table I. The vertical axis denotes the accumulated number of species desorbed from a unit area of the substrate surface during the desorption step of this cycle. The adsorption steps for (a) and (b) and (c) are the thin Cl layer deposition and those for (c) and (d) are the thick Cl layer deposition. The incident energy of  $\mathsf{Ar^{+}}$  ions is  $20\mathrm{eV}$  for (a) and (c) and  $50\mathrm{eV}$  for (b) and (d).

The chart shows the number of species per cm² as a function of Ar⁺ ion dose for thin Cl layer deposition at 20 eV.

The chart shows the number of species per cm² as a function of Ar⁺ ion dose for thin Cl layer deposition at 50 eV.

The chart shows the number of species per cm² as a function of Ar⁺ ion dose for thick Cl layer deposition at 20 eV.

The chart shows the number of species per cm² as a function of Ar⁺ ion dose for thick Cl layer deposition at 50 eV.

| Ar⁺ Ion Dose (×10¹⁶/cm²) | Si   | Cl   | SiCl | SiCl₂ | SiCl₃ |
|---------------------------|------|------|------|-------|-------|
| 0                        | 0    | 0    | 0    | 0     | 0     |
| 5                        | 1    | 2    | 3    | 0.5   | 0.2   |
| 10                       | 2    | 3    | 4    | 0.8   | 0.3   |
| 15                       | 3    | 4    | 4.5  | 1.0   | 0.4   |
| 18                       | 3.5  | 4.5  | 5    | 1.2   | 0.5   |

| Ar⁺ Ion Dose (×10¹⁶/cm²) | Si   | Cl   | SiCl | SiCl₂ | SiCl₃ |
|---------------------------|------|------|------|-------|-------|
| 0                        | 0    | 0    | 0    | 0     | 0     |
| 5                        | 10   | 1    | 2    | 0.5   | 0.2   |
| 10                       | 20   | 1.5  | 2.5  | 0.8   | 0.3   |
| 15                       | 30   | 2    | 3    | 1.0   | 0.4   |
| 18                       | 35   | 2.2  | 3.2  | 1.2 | -   |

| Ar⁺ Ion Dose (×10¹⁶/cm²) | Si   | Cl   | SiCl | SiCl₂ | SiCl₃ |
|---------------------------|------|------|------|-------|-------|
| 0                        | 0    | 0    | 0    | 0     | 0     |
| 5                        | 0.5  | 25   | 3    | 1.0   | 0.5   |
| 10                       | 1    | 28   | 4    | 1.5   | 0.8   |
| 15                       | 1.2  | 30   | 4.5  | 1.8   | 1.0   |
| 18                       | 1.5  | 32   | 5    | 2.0   | 1.2   |

| Ar⁺ Ion Dose (×10¹⁶/cm²) | Si   | Cl   | SiCl | SiCl₂ | SiCl₃ |
|---------------------------|------|------|------|-------|-------|
| 0                        | 0    | 0    | 0    | 0     | 0     |
| 5                        | 10   | 20   | 3    | 1.0   | 0.5   |
| 10                       | 20   | 25   | 4    | 1.5   | 0.8   |
| 15                       | 30   | 28   | 4.5  | 1.8   | 1.0   |
| 18                       | 35   | 30   | 5    | 2.0   | 1.2   |

Answer: These images focus on the accumulated numbers of desorbed species in the desorption step of C6 as functions of the Ar+ ion dose under various conditions

Answer:
The accumulated numbers of desorbed monoatomic Si atoms and SiCl radicals, which are the next highest after monoatomic Cl, are almost the same initially. However, as the amount of Cl on the
surface depletes, the rates of desorption for SiCl and SiCl2 decrease while monoatomic Si atoms continue to desorb. Furthermore, the desorption rate of monoatomic Si decreases as that of monoatomic Cl also decreases. It should be noted that the desorption of monoatomic Si does not mean the etching is purely due to physical sputtering. The physical sputtering yield of Si by 20 eV Ar+ ion bombardment is null essentially. The enhanced desorption of monoatomic Si atoms is likely caused by the bond breaking of Si atoms by Cl atoms remaining in the substrate

Answer:
1. For thin Cl deposited films at high Ar+ ion, Si atoms mostly desorb as Cl bonded species in an
early stage of the desorption step
2. For thick Cl deposited films, the desorption of SiClm is observed only in the very early stage of the Ar+ ion injection

Answer: Yes


FIG. 3. (a) Contributions of Ga-O and Ga-N to the Ga3d peak area plotted as a function of sputter depth. The vertical dashed line indicates the spectra shown in (b). (b) The Ga3d signal after  $20\mathrm{s}$  of sputtering, highlighting the positions of the Ga-O and the Ga-N peaks at  $20.5$  and  $19.3\mathrm{eV}$ , respectively.

XPS depth profile showing the Ga-N and Ga-O contributions to the Ga3d peak area as a function of sputter depth. The Ga-O signal is highest at the surface and decreases with depth, indicating an oxidized surface layer extending approximately 10 nm into the film. The Ga-N signal increases with depth, reaching a maximum in the bulk region.

Fitted Ga3d XPS spectrum after 20 s of sputtering, showing deconvolution into Ga-N (19.3 eV) and Ga-O (20.5 eV) components. At this depth, both bonding environments contribute to the signal.

| Sputter depth (nm) | Ga-N Area (CPS eV) | Ga-O Area (CPS eV) |
|---|---|---|
| 0 | 2200 | 4100 |
| 1 | 3500 | 2800 |
| 3 | 4200 | 1900 |
| 5 | 4500 | 1500 |
| 10 | 4900 | 1000 |
| 20 | 5400 | 600 |
| 30 | 5800 | 100 |
| 35 | 5600 | 0 |
| 40 | 3500 | 0 |
| 45 | 100 | 0 |

| Binding Energy (eV) | Envelope (Norm.) | Ga-N Component (Norm.) | Ga-O Component (Norm.) |
|---|---|---|---|
| 23.0 | 0.00 | 0.00 | 0.00 |
| 21.5 | 0.15 | 0.00 | 0.15 |
| 20.6 | 0.90 | 0.45 | 0.45 |
| 19.8 | 1.00 | 0.80 | 0.20 |
| 19.4 | 0.90 | 0.85 | 0.05 |
| 18.0 | 0.20 | 0.20 | 0.00 |
| 16.0 | 0.00 | 0.00 | 0.00 |

Answer: It marks the sputter depth (after 20 s of sputtering) corresponding to the spectrum shown in subfigure (b).

Answer: The oxidized layer represents surface contamination that the ALE process aims to remove, and it affects the initial etch rate before reaching stoichiometric GaN.

Answer: The Ga-O signal is highest at the surface (~4000 CPS·eV) and decreases rapidly within the first 10 nm, indicating a heavily oxidized surface layer. Beyond ~25 nm sputter depth, the Ga-O signal becomes negligible while Ga-N dominates, representing the transition to stoichiometric GaN in the bulk. This oxidized layer formed during storage in ambient conditions.

Answer: Ga-N is at 19.3 eV and Ga-O is at 20.5 eV.

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. 4. Gibbs free energy change  $(\Delta G)$  as a function of temperature for the fluorination half-cycle considering both the conversion (blue) and chemical vapor etching (red) reactions. Solid lines indicate plasma fluorination reactions (F radicals), while the thermal fluorination reactions (HF) are indicated by dashed lines. A vertical dashed line at  $450^{\circ}C$  highlights the change for the plasma fluorination reactions from the preferred conversion regime to the preferred etching regime. The ligand-exchange half-cycle is also included (dashed-dotted line, green) and shows a negative  $\Delta G$  over the entire evaluated temperature range.

DFT simulation results showing Gibbs free energy change (ΔG) vs. temperature for GaN ALE reactions. Plasma fluorination (F radicals, solid lines) shows both conversion and CVE reactions are thermodynamically favorable (ΔG < 0), with conversion preferred below 450°C. Thermal fluorination (HF, dashed lines) shows conversion is only favorable below ~250°C and CVE is unfavorable at all temperatures. The TMA ligand-exchange reaction (dash-dotted green) is favorable across the entire temperature range.

| Temperature (°C) | F radical etching (eV/GaN) | F radical conversion (eV/GaN) | TMA Ligand-exchange (eV/GaN) | HF etching (eV/GaN) | HF conversion (eV/GaN) |
|---|---|---|---|---|---|
| -200 | -18.0 | -20.8 | -0.6 | 0.2 | -2.3 |
| 0 | -16.6 | -18.6 | -1.5 | 0.4 | -1.4 |
| 200 | -15.2 | -16.4 | -2.3 | 0.7 | -0.6 |
| 300 | -14.5 | -15.2 | -2.6 | 0.8 | -0.1 |
| 400 | -13.8 | -14.1 | -3.0 | 0.9 | 0.5 |
| 450 | -13.5 | -13.5 | -3.2 | 1.0 | 0.9 |
| 500 | -13.1 | -13.0 | -3.4 | 1.1 | 1.2 |

Answer: The DFT simulations show that F radical reactions have much more negative ΔG values than HF reactions, indicating stronger thermodynamic driving force. For HF, the conversion reaction becomes unfavorable above ~250°C and CVE is never favorable. In contrast, F radical conversion remains favorable up to 450°C with ΔG values around -15 to -20 eV/GaN, explaining why GaN is resistant to thermal fluorination but can be effectively fluorinated using plasma.

Answer: The process transitions from the preferred conversion regime to the preferred etching regime, making it unsuitable for self-limiting ALE.

Answer: The reaction is thermodynamically favorable and can proceed spontaneously.

Answer: No. The ligand-exchange reaction has negative ΔG across the entire evaluated temperature range, so it does not thermodynamically constrain the process window.


FIG. 13. (Color online) Trends in the ALE synergy  $(S_{y})$  as a function of pulse times for an AR of 4. (a)  $S_{y}$  as a function of ion bombardment time  $(T_{I})$  for three values of passivation time  $(T_{P})$ . (b)  $S_{y}$  as a function of  $T_{I}$  and  $T_{P}$ . The solid black line represents  $\mathrm{EPC} = 1$  and the dotted lines bound the range  $0.9 < \mathrm{EPC} < 1.1$ .

The line chart illustrates the relationship between ALE synergy and ion bombardment time, showing a peak at around 0.5 seconds.

The heatmap visualizes the ALE synergy across different passivation times and ion bombardment times, with color intensity indicating the level of synergy.

| Ion Bombardment Time (Ti, s) | ALE Synergy (%) Tp = 44 ms | Tp = 66 ms | Tp = 88 ms |
|------------------------------|----------------------------|------------|------------|
| 0.00                         | 90                         | 85         | 82         |
| 0.25                         | 93                         | 91         | 86         |
| 0.50                         | 92                         | 89         | 87         |
| 0.75                         | 89                         | 87         | 86         |
| 1.00                         | 87                         | 86         | 85         |
| 1.25                         | 85                         | 84         | 82         |
| 1.50                         | 84                         | 83         | 81         |

| Passivation Time (Tp, ms) | Ion Bombardment Time (Ti, s) | ALE Synergy (%) |
|---------------------------|------------------------------|------------------|
| 5                         | 0.30                         | ~75             |
| 25                        | 0.30                         | ~85             |
| 45                        | 0.30                         | ~90             |
| 64                        | 0.30                         | ~88             |
| 84                        | 0.30                         | ~85             |
| 104                       | 0.30                         | ~82             |

Answer: For short TI (<0.15 s), a large fraction of the passivated Si which covers the surface of the feature is not removed during the ion bombardment step. The continuous etching produced by ions in the passivation phase then makes a significant contribution to the total rate of etching, which then lowers Sy.

Answer: For long TI (>1 s), the passivated Si covering the feature is completely removed and the now bare silicon is exposed to ion bombardment for an extended time. The continuous etching produced during the ion bombardment step by the presence of chlorine radicals and physical sputtering then accounts for a significant portion of the EPC, which then lowers Sy

Answer: In general, to minimize nonidealities during ALE, the  optimized process should use the shortest pulse times which result in ~1ML material removal per cycle for the largest AR feature being etched. These optimized process times will be given by the point closest to the origin on the solid line in image (b). These conditions also correspond to the smallest contribution of continuous chemical sputtering, and will result in the smoothest surface and widest processing window in terms of AR.

Answer: Yes

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/3/Atomic layer etching of 3D structures in silicon Self-limiting.pdf


Figure 3. Electronic potential energies  $(\Delta E)$  and Gibbs free energies  $(\Delta G^{80^{\circ}C})$  of nickel formate  $\left(\mathrm{Ni}(\mathrm{FA})_{2}\right)$  and formamidinate (Ni $\left(\mathrm{FAmd}\right)_2)$  oligomer (olig.) complexes relative to the monomer (mono.) complex. Energy differences are normalized by nuclearity (nucl.) for comparison on a per-metal atom basis.

Multiple line chart comparing electronic potential energies (ΔE) and Gibbs free energies (ΔG at 80 °C) per metal atom for nickel formate (FA) and formamidinate (FAmd) oligomers. The FA system shows its lowest ΔG at the dimer stage, while the FAmd system reaches its minimum ΔG at the trimer. These trends indicate ligand-dependent stabilization as oligomer size increases.

| Oligomer State | ΔE_FA (eV) | ΔG_FA (80°C)(eV) | ΔE_FAmd(eV) | ΔG_FAmd (80°C)(eV) |
|----------------|-------------|------------------|--------------|------------------|
| Monomer | 0.0    | 0.0    | 0.0     | 0.0     |
| Dimer   | ~ -1.0 | ~ -0.5 | ~ -1.50 | ~ -0.75 |
| Trimer  | ~ -1.0 | ~ -0.4 | ~ -1.90 | ~ -1.25 |
| Tetramer| ~ -0.6 | ~ 0.00 | ~ -1.10 | ~ -0.25  |

Answer: The Trimer.

Answer: No

Answer: The FA complexes reach their lowest Gibbs free energy at the dimer stage, after which stability decreases for larger oligomers. In contrast, the FAmd complexes continue to stabilize beyond the dimer, reaching a minimum at the trimer before becoming less favorable at the tetramer. This indicates that ligand chemistry strongly influences the preferred oligomer size.

Answer: Ligand systems that favor specific oligomer sizes may influence volatility, transport, or surface reactivity in vapor-phase processes. The observed preference for FA dimers and FAmd trimers suggests that ligand choice can tune aggregation behavior, which may be relevant when designing precursors for controlled deposition or etching.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/31/Thermodynamics of Atomic Layer Etching Chemistry on Copper and Nickel Surfaces from First Principles.pdf


Figure 4. Adsorption energies of different terminations of the  $\mathrm{Ni / N}$ ,  $\mathrm{Cu / N}$ ,  $\mathrm{Ni / O}$ , and  $\mathrm{Cu / O}$  systems as a function of coverage. The labels "PR" and "MP" represent the "pairing row" and "missing row" reconstructions of the (110) surfaces, respectively.

Multiple line chart showing Gibbs free energy of adsorption (ΔG_ads^80 °C) versus nitrogen coverage for the Ni/N system across several crystallographic facets. Adsorption becomes progressively less favorable with increasing coverage for all facets.

Multiple line chart showing ΔG_ads^80 °C versus nitrogen coverage for the Cu/N system. Adsorption energies are consistently more positive than in Ni/N, indicating weaker nitrogen binding on Cu surfaces.

Multiple line chart showing ΔG_ads^80 °C versus oxygen coverage for the Ni/O system, including labeled surface reconstructions such as (100) p(2×2), (110) (2×1)-MR, and (3×1)-MR. Oxygen adsorption is strongly favorable at low coverage and weakens with increasing coverage.

Multiple line chart showing ΔG_ads^80 °C versus oxygen coverage for the Cu/O system, including pairing-row reconstructions. Adsorption becomes less favorable with increasing oxygen coverage and approaches thermoneutral behavior at high coverage.

| Coverage θ_N (Å⁻²) | Blue Solid | Green Dash | Red Dash-Dot | Blue Dash | Purple Dash Dot | Yellow Solid |Teal Dash |
|---|---|---|---|---|---|---|---|
| 0.025 | ~ -0.6 | ~ +0.1 | ~ +0.3 | ~ 0.0  | ~ -0.25 | ~ +0.0 |~ +0.2 |
| 0.05  | ~ -0.4 | ~ +0.1 | ~ +0.3 | ~ +0.1 | ~ +0.00 | ~ +0.1 |~ +0.2 |
| 0.10  | ~ +0.25| ~ +0.4 | ~ +0.9 | ~ +0.4 | ~ +0.20 | ~ +0.5 |~ +0.5 |
| 0.15  | ~ +1.0 | ~ +1.1 | ~ +1.5 |   -    | ~ +0.90 | ~ +1.0 |~ +1.0 |

| Coverage θ_N (Å⁻²) | Blue Solid | Green Dash | Red Dash-Dot | Blue Dash | Purple Dash Dot | Yellow Solid |Teal Dash |
|---|---|---|---|---|---|---|---|
| 0.025 | ~ +0.8 | ~ +1.5 | ~ +1.7 | ~ +1.4 | ~ +1.00 | ~ +1.2 |~ +1.2 |
| 0.05  | ~ +0.8 | ~ +1.5 | ~ +1.6 | ~ +1.5 | ~ +1.00 | ~ +1.2 |~ +1.2 |
| 0.10  | ~ +1.5 | ~ +1.8 | ~ +2.1 |   -    |   -     | ~ +1.8 |~ +1.5 |
| 0.125 | ~ +1.8 | ~ +0.0 | ~ +2.9 |   -    |   -     | ~ +2.1 |~ +2.3 |

| Coverage θ_O (Å⁻²) | Blue Solid | Green Dash | Red Dash-Dot | Blue Dash | Purple Dash Dot | Yellow Solid |Teal Dash |
|---|---|---|---|---|---|---|---|
| 0.05 | ~ -2.1 | ~ -1.8 | ~ -1.9 | ~ -1.9 | ~ -2.1  | ~ -2.0 |~ -2.0 |
| 0.10 | ~ -1.6 | ~ -1.5 | ~ -1.5 | ~ -1.6 | ~ -1.75 | ~ -1.6 |~ -1.5 |
| 0.15 | ~ -1.25| ~ -1.3 | ~ -0.9 | ~ -1.4 | ~ -1.25 | ~ -1.2 |~ -1.3 |
| 0.20 |   -    |   -    | ~ -0.5 | ~ -1.0 | ~ -1.00 | ~ -0.9 |~ -1.0 |

| Coverage θ_O (Å⁻²) | Blue Solid | Green Dash | Red Dash-Dot | Blue Dash | Purple Dash Dot | Yellow Solid |Teal Dash |
|---|---|---|---|---|---|---|---|
| 0.05 | ~ -1.6 | ~ -1.4 | ~ -1.3  | ~ -1.4 | ~ -1.60 | ~ -1.4 |~ -1.5 |
| 0.10 | ~ -1.3 | ~ -1.2 | ~ -0.75 | ~ -1.2 | ~ -1.20 | ~ -1.0 |~ -1.2 |
| 0.15 | ~ -0.3 | ~ -0.6 | ~ -0.00 | ~ -0.9 | ~ -0.90 | ~ -0.6 |~ -0.9 |
| 0.20 |    -   |    -   |   -     | ~ -0.4 | ~ -0.50 |    -   |~  0.0 |

Answer: 80 °C (indicated by the superscript in ΔG_ads^80 °C).

Answer: No, the energy generally increases (becomes more positive/less stable) as coverage increases.

Answer: Subfigure (c) explicitly labels several surface reconstructions for the Ni/O system. For the (100) facet, it identifies $p(2 \times 2)$ and $c(2 \times 2)$ structures, while for the (110) facet, it highlights $(2 \times 1)-MR$ and $(3 \times 1)-MR$ "missing row" reconstructions. At the lowest coverage shown, the $(110) (2 \times 1)-MR$ reconstruction (marked with a green cross) appears to be the most stable, having the lowest $\Delta G$ value below -2.0 eV.

Answer: The Ni/N system (a).


(a)

The chart compares the total energy per atom over time between two computational methods: Density Functional Theory (DFT) and a Neural Network Potential (NNP). The x-axis represents time in picoseconds (ps), while the y-axis shows energy in electron volts per atom (eV/atom). Both methods exhibit similar dynamic energy profiles with overlapping fluctuations, suggesting that the NNP method reliably captures the same energy behavior as the more computationally expensive DFT. This highlights NNP’s potential for efficient and accurate simulations in extended time or larger systems.

| Time (ps) | DFT (eV/atom) | NNP (eV/atom) |
|-----------|---------------|---------------|
| 0         | -7.20         | -7.22         |
| 10        | -7.05         | -7.07         |
| 20        | -6.95         | -6.98         |
| 30        | -7.10         | -7.13         |
| 40        | -6.90         | -6.92         |
| 50        | -7.00         | -7.03         |
| 60        | -6.85         | -6.88         |
| 70        | -6.95         | -6.97         |

Answer: The NNP model closely mirrors the energy profile predicted by DFT over the full simulation time, maintaining similar fluctuation amplitudes and trends. While minor deviations are visible at certain time points, the overall agreement between the two methods supports the accuracy of the NNP in reproducing DFT-level energy predictions, making it suitable for large-scale simulations.

Answer: Yes

Answer: DFT

Answer: Reduced computational cost, Faster simulation times, Comparable accuracy for energy predictions, Scalability to larger systems or longer timescales

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


(a) Figure 6. (a) The number of Si, N, H, and F atoms in the simulation cell during the etching process at  $E_{\mathrm{in}} = 50 \mathrm{eV}$  and  $\theta_{\mathrm{in}} = 0^{\circ}$ . (b) Etching yield as a function of incident energy. The black dashed line represents the fitted function of the universal etching behavior.[52] The error bars indicate the standard deviations among three independent runs.

This figure presents the number of Si, N, H, and F atoms in a system as a function of HF dose. As HF exposure increases from 0 to 200 HF/nm², both silicon (Si) and nitrogen (N) atoms show a steady decline, indicating progressive etching or transformation. Fluorine (F) atoms increase significantly at lower doses and then level off, suggesting that surface fluorination saturates over time. Hydrogen (H) levels remain relatively constant, suggesting limited involvement or a dynamic equilibrium. Together, these trends reveal the elemental evolution occurring during HF exposure and suggest that nitrogen and silicon are preferentially removed or transformed while fluorine accumulates on the surface.

| Dose (HF/nm²) | Si | N | H | F |
|---------------|----|----|----|----|
| 0             | 400 | 500 | 100 | 0   |
| 50            | 370 | 460 | 110 | 120 |
| 100           | 340 | 420 | 110 | 140 |
| 150           | 310 | 390 | 110 | 150 |
| 200           | 280 | 360 | 110 | 150 |

Answer: As the HF dose increases, the number of nitrogen and silicon atoms steadily decreases, indicating progressive material removal or chemical transformation. In contrast, the number of fluorine atoms increases sharply at lower doses and then plateaus, suggesting surface saturation or limited incorporation beyond a certain dose. The hydrogen atom count remains nearly constant, implying either low reactivity or steady-state behaviour. These trends highlight the distinct chemical roles each element plays during HF exposure.

Answer: Fluorine (F)

Answer: Yes

Answer: Si and N are progressively removed ,Fluorine accumulates , Hydrogen remains constant


Figure 2. Etch per cycle of TiN films with varying  $\mathbb{C}\mathbb{C}\mathbb{I}_4$  pulse time at  $460^{\circ}C$  6 s long  $\mathbb{N}_2$  purges were used. The figure compares the EPC for the binary process (red) to the CVE process (blue).

Figure 2 illustrates the etch per cycle (EPC) of TiN films as a function of CCl₄ pulse time at 460 °C, comparing two etching processes: the NbF₅–CCl₄ binary process and the CCl₄-only CVE process. The EPC increases with CCl₄ pulse time for both processes, with the binary process showing higher etch rates (up to ~0.8 Å at 3 s) compared to the CVE process (~0.5 Å at 3 s). No clear saturation of EPC is observed for either process, and no etching occurs when only NbF₅ is applied, consistent with computational predictions.

| CCl₄ pulse time [s] | Etch per cycle NbF₅–CCl₄ [Å] | Etch per cycle CCl₄-only CVE [Å] |
|---|---|---|
| 0.0 | 0.0 | 0.0 |
| 0.5 | 0.3 | 0.3 |
| 1.0 | 0.4 | 0.4 |
| 3.0 | 0.8 | 0.5 |

Answer: No

Answer: For both processes, the etch per cycle increases with increasing CCl₄ pulse time. The NbF₅–CCl₄ binary process consistently shows higher EPC values than the CCl₄-only CVE process. At 3 s pulse time, the EPC reaches approximately 0.8 Å for the binary process and 0.5 Å for the CVE process. No clear saturation is observed, indicating a nearly linear increase across the measured pulse times.

Answer: Enhanced reactivity of CCl₄ with fluorinated TiN surfaces, Formation of more volatile etch products such as TiCl₄ instead of less volatile species (TiCl₃, TiOCl, TiF₃), Possible three-dimensional etching due to fluorine diffusion through TiN grain boundaries, Self-limiting reactions of NbF₅ pulses followed by catalyzed CCl₄ adsorption at Nb sites

Answer: Approximately 0.5 Å.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/4/Combining Experimental and DFT Investigation.pdf


Figure 3. Effect of etch temperature on etch per cycle for the binary process (blue curve) as well as  $\mathrm{CCl_4}$  alone (blue curve) process. Both the precursor pulses and the purge times were fixed to 1 and 6 s, respectively.

Figure 3 shows the effect of etch temperature on the etch per cycle of TiN films for the NbF₅–CCl₄ binary process and the CCl₄-only process. The etch per cycle increases with temperature for both processes, with the binary process consistently exhibiting higher etch rates. No significant etching occurs below 370 °C, and the trend is approximately linear up to 460 °C.

| Etch temperature [°C] | Etch per cycle NbF₅–CCl₄ [Å] | Etch per cycle CCl₄-only [Å] |
|---|---|---|
| 370 | 0.03 | 0.07 |
| 380 | 0.10 | 0.12 |
| 390 | 0.20 | 0.18 |
| 400 | 0.40 | 0.22 |
| 460 | 0.55 | 0.30 |

Answer: No

Answer: The etch per cycle increases with temperature for both processes. The NbF₅–CCl₄ binary process consistently shows higher EPC values than the CCl₄-only process. At 370 °C, the EPC is 0.03 Å for the binary process and 0.07 Å for CCl₄-only. By 460 °C, the EPC rises to 0.55 Å for the binary process and 0.3 Å for the CCl₄-only process, demonstrating a nearly linear increase with temperature.

Answer: Enhanced reactivity of CCl₄ with fluorinated TiN surface, Formation of more volatile etch products such as TiCl₄ instead of less volatile species, Self-limiting reactions of NbF₅ followed by catalyzed CCl₄ adsorption, Higher activation of surface reactions at elevated temperatures

Answer: Approximately 0.4 Å.


Figure 4. A change in the thickness values with total number of etch cycles at  $460^{\circ}\mathrm{C}$  for TiN,  $\mathrm{SiO_2}$ ,  $\mathrm{Al}_2\mathrm{O}_3$ , and  $\mathrm{Si}_3\mathrm{N}_4$  films. A TiN is selectively etched away by  $\mathrm{CCl_4}$  alone over other materials.

Figure 4 shows the change in film thickness with the total number of etch cycles at 460 °C for TiN, SiO₂, Al₂O₃, and Si₃N₄ films. The TiN film is selectively etched by the CCl₄-only CVE process, with thickness decreasing linearly at approximately 0.3 Å per cycle, reaching about 13 nm after 500 cycles. In contrast, the thickness of Al₂O₃, SiO₂, and Si₃N₄ remains unchanged even after 1000 etch cycles, demonstrating the high selectivity of TiN etching over other materials.

| Etch cycles | TiN (ALD) | Al₂O₃ (ALD) | SiO₂ (TOx) | Si₃N₄ (LPCVD) |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 100 | 3 | 0 | 0 | 0 |
| 300 | 9 | 0 | 0 | 0 |
| 500 | 13 | 0 | 0 | 0 |
| 1000 | 30 | 0 | 0 | 0 |

Answer: no

Answer: The TiN film thickness decreases linearly with the number of etch cycles, reflecting an etch rate of approximately 0.3 Å per cycle. In contrast, the thicknesses of Al₂O₃, SiO₂, and Si₃N₄ remain essentially unchanged even after 1000 cycles. This demonstrates the high selectivity of TiN etching over the other materials under the same process conditions.

Answer: Enables precise patterning and removal of TiN without damaging other substrate materials, Maintains integrity of dielectric layers (Al₂O₃, SiO₂) and nitride layers (Si₃N₄), Reduces the risk of contamination or undesired etching in multi-layer devices, Facilitates reliable manufacturing in microelectronics and nanofabrication processes

Answer: Approximately 13 nm.


Figure 7. An XPS depth profiling through remaining TiN film after partial etching at  $460^{\circ} \text{C}$ . Total 300 cycles were performed with  $0.5 \text{s}$  of both  $\text{NbF}_5$  and  $\text{CCl}_4$  pulse lengths with  $6 \text{s}$  of  $\text{N}_2$  purges.

Figure 7 presents an XPS depth profile of a partially etched TiN film after 300 cycles of the NbF₅–CCl₄ etch process at 460 °C, with 0.5 s pulses and 6 s N₂ purges. The surface initially contains high carbon (~26%) and oxygen (~31%), along with nitrogen (~20%), titanium (~15%), niobium (~5%), and small amounts of fluorine and silicon (<2%). After 15 s of argon sputtering, carbon decreases to ~4% and further to ~3% after 60 s, while Ti, N, and O stabilize at ~24–32%. Nb and F remain at 5–6% and 0.9–1.7%, respectively, indicating partial incorporation or diffusion within the TiN surface layer. Si originates from the underlying SiO₂. The profile confirms the elemental distribution and partial etch depth of the TiN film.

| Sputter time [s] | C1s (%) | N1s (%) | O1s (%) | F1s (%) | Si2p (%) | Ti2p (%) | Nb3d (%) |
|---|---|---|---|---|---|---|---|
| 0 | 26 | 20 | 31 | 1.5 | 1.5 | 15 | 5 |
| 15 | 4 | 32 | 28 | 1.0 | 1.5 | 24 | 5.5 |
| 60 | 3 | 32 | 28 | 0.9 | 1.5 | 24 | 6 |

Answer: Yes

Answer: Initially, the surface contains a high carbon concentration (~26%) and lower Ti (~15%) and N (~20%). After 15 s of argon sputtering, carbon decreases sharply to ~4%, while Ti, N, and O increase slightly and stabilize at ~24–32%. After 60 s of sputtering, carbon drops further to ~3%, and Ti, N, and O remain stable, reflecting the bulk composition of the remaining TiN film. This trend shows that surface contamination diminishes with depth while the elemental composition of the film core is revealed.

Answer: Determines the elemental distribution within the remaining TiN film, Reveals surface contamination and its removal with sputtering, Confirms partial incorporation of Nb and F into the TiN surface layer, Helps assess the effectiveness and uniformity of the etch process, Provides information about possible diffusion or adsorption mechanisms during etching

Answer: Approximately 24%.


Fig. 5 (a) Density profile of Ge and Cl element change before and after 200 times Ar bombardment with different bombardment energy on  $25\mathrm{eV}$  chlorinated surface. (b) Total etched number change (blue: Ge, red: Cl) with Ar bombardment energy for each chlorination condition, averaged from three samples with error bars calculated.

The line chart shows the number density of Ge and Cl atoms at different z distances for initial and final states on 25 eV chlorinated surface.

The line chart shows the number density of Ge and Cl atoms at different z distances for initial and final states on 50 eV chlorinated surface.

The line chart shows the number density of Ge and Cl atoms at different z distances for initial and final states on 75 eV chlorinated surface.

The line chart shows the number density of Ge and Cl atoms at different z distances for initial and final states on 100 eV chlorinated surface.

The line chart illustrates the total etched numbers of Ge atoms at different Ar energies.

The line chart illustrates the total etched numbers of Cl atoms at different Ar energies.

| z distance (Å) | Density Ge_initial | Density Cl_initial | Density Ge_final | Density Cl_final |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 50 | 75 | 75 | 65 | 50 |

| z distance (Å) | Density Ge_initial | Density Cl_initial | Density Ge_final | Density Cl_final |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 50 | 75 | 75 | 50 | 25 |

| z distance (Å) | Density Ge_initial | Density Cl_initial | Density Ge_final | Density Cl_final |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 50 | 75 | 75 | 40 | 10 |

| z distance (Å) | Density Ge_initial | Density Cl_initial | Density Ge_final | Density Cl_final |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 50 | 75 | 75 | 15 | 5 |

| Ar energy (eV) | Ge_5eV | Ge_10eV | Ge_25eV | Ge_50eV |
|---|---|---|---|---|
| 25 | 100 | 150 | 250 | 400 |
| 50 | 150 | 250 | 350 | 550 |
| 75 | 500 | 500 | 600 | 700 |
| 100 | 550 | 600 | 700 | 800 |

| Ar energy (eV) | Ge_5eV | Ge_10eV | Ge_25eV | Ge_50eV |
|---|---|---|---|---|
| 25 | 50 | 100 | 200 | 300 |
| 50 | 100 | 200 | 250 | 400 |
| 75 | 250 | 250 | 400 | 500 |
| 100 | 250 | 300 | 450 | 600 |

Answer: The threshold energy decreases as the chlorination energy increases.

Answer: Figure 5 demonstrates that both the chlorination energy and the Ar bombardment energy have a strong and interrelated influence on the onset and efficiency of etching. As the chlorination energy increases, the surface becomes more disordered and vulnerable to atom detachment, which lowers the threshold Ar energy required to initiate etching. At the same time, higher bombardment energies lead to increased etching of both Ge and Cl atoms, indicating higher etching rates. However, for lower chlorination energies, the etched atom numbers tend to reach a plateau as the available chlorine becomes limited, reflecting a self-limiting chemical etching process. In contrast, higher chlorination energies delay this plateau because more chlorine is initially present, allowing etching to continue over a larger range of bombardment energies before transitioning into physical sputtering.

Answer: The Cl density peak starts to decrease and the Ge surface begins to recede already at an Ar bombardment energy of 25 eV, with the etching effect becoming more obvious at 50 eV.

Answer: Complete etching occurs between 60–75 eV for the 5 eV chlorinated surface, 75-100 eV for the 10 and 25 eV chlorinated surfaces, and above 100 eV for the 50 eV chlorinated surface.

icdar2026-competition-data/train/atomic-layer-etching/simulation-usecase/5/Computational modelling of atomic layer etching of chlorinated germanium surfaces by argon.pdf


FIG.2.  $\mathbb{C}\mathbb{I}_2$  mass flow, pressure, and DC bias during one 7 s ALE cycle. The applied DC bias is  $-65\mathrm{V}$  for this case. The Ar flow (80 SCCM) is on continuously throughout the cycle. ICP power is 250 W.

The multi-axis chart shows the evolution of DC self-bias voltage, chlorine gas flow, and chamber pressure over time. The process is divided into four clearly marked steps, each showing how plasma conditions and gas flow influence system parameters. The other panels are not separate figures but sub-intervals within (a). Their summaries have been removed to avoid redundancy and reflect the unified timeline.

| Time (s) | DC Self-Bias (V) | Cl₂ Flow (seccm) | P (mTorr) |
|----------|------------------|------------------|-----------|
| 0        | 0                | 0                | 22        |
| 1        | 0                | 20               | 22        |
| 2        | -60              | 20               | 21        |
| 3        | -60              | 0                | 20        |
| 4        | -60              | 0                | 20        |
| 5        | 0                | 20               | 21        |
| 6        | 0                | 0                | 22        |
| 7        | 0                | 0                | 22        |

Answer: Step 1: Cl₂ On, ICP Off, Bias Off; Step 2: ICP On, Bias On; Step 3: Cl₂ Off, Bias Off; Step 4: All Off

Answer: Yes

Answer: Pressure decreases slightly with ICP on, then returns to baseline; Cl₂ flow toggles between 20 seccm and 0 based on step.

Answer: DC Self-Bias (V), Cl₂ Flow (seccm), Pressure (mTorr)

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


FIG. 4. Gibbs free energy change  $(\Delta \mathbb{G})$  as a function of temperature for the fluorination half-cycle considering both the conversion (blue) and chemical vapor etching (red) reactions. Solid lines indicate plasma fluorination reactions (F radicals), while the thermal fluorination reactions (HF) are indicated by dashed lines. A vertical dashed line at  $450^{\circ}C$  highlights the change for the plasma fluorination reactions from the preferred conversion regime to the preferred etching regime. The ligand-exchange half-cycle is also included (dashed-dotted line, green) and shows a negative  $\Delta \mathbb{G}$  over the entire evaluated temperature range.

The chart illustrates the change in Gibbs free energy (ΔG) per unit GaN with respect to temperature for various etching methods.

| Temperature (°C) | ΔG (eV/GaN) HF CVE |ΔG (eV/GaN) HF conversion |ΔG (eV/GaN) TMA ligand-exchange |ΔG (eV/GaN) F radical CVE |ΔG (eV/GaN) F radical conversion |
|---|---|---|---|---|---|
|-200 | 0 |-3|-0.5|-18.5|-21|
|-100 | 0 |-2|-1|-18|-20|
|0 | 0.5 |-2|-1.5|-16|-19|
|100 | 1 |-1|-2|-16|-18|
|200 | 1 |0|-2.5|-15|-17|
|300 | 1|0|-3|-14|-16|
|400 | 1.5 |1|-3.5|-14|-14|
|500 | 1.5 |1.5|-4|-14.5|-13|

Answer: The use of F radicals in a plasma as this lowers the gibbs energy the most.

Answer: F radical conversion, as this has lower delta gibbs energies. Only from 450 degrees celcius and up will there be etching.

Answer: The chance decreases.

Answer: +1 eV/GaN

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


Fig. 7. Schematic of the energy conversion process and snapshots of the density distribution with time evolution, the distributions on excited-state and ground-state potential energy curves are represented by solid and dashed lines, respectively. The vertical line  $Z = Z_{d}$  is the defined critical value, the  $\mathrm{SiCl_2}$  molecule crossing this line can be identified as to be completely desorbed. Since the distribution for  $Z > Z_{d}$  is small, it was multiplied by a factor of  $4\times 10^{5}$  if  $Z > Z_{d}$  to make it visible.

The figure illustrates the potential energy of a system as a function of surface coordinate Z at various time points (t=0 fs, t=5 fs, t=10 fs, t=400 fs). It shows the transition between the ground state and excited state, with terms like 'Excitation', 'Quenching', and 'Evolving' indicating the dynamics of the system.

| Surface coordinate Z (Å) | Potential energy (eV) Ground state | Potential energy (eV) Excited state | Density Ground state |Density Excited state |
|---|---|---|---|---|
|-0.7 | 3 |4.2|-|-|
| 0 | 0 |3.1|Peak|Peak|
| 1 | 1.6 |2.6|-|-|
| 2 | 2.4 |2.5|-|-|
| 3 | 2.5 |2.5|-|-|
| 4 | 2.5 |2.5|-|-|

Answer: The critical distance is 3 angstroms, this is the distance from which a SiCl2 unit is defined to be fully desorbed.

Answer: Quenching is the transition from the excited state to the ground state by energy dissipation in the system, so from the red line to the blue line.

Answer: The excited state is induced by the absorption of photons with the correct energy. The amount of excited species reduces over time in the system, explaining the trend in the densities for the excited state and the ground state.

Answer: The desorption energy is 2.5 eV

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