FIG. 7. Amount of Si etched in units of  $\dot{A}$  (blue lines) and Cl uptake (red lines) during the final cycle for the  $\mathrm{Si - Cl_2 - Ar}$  ALE simulation using  $100\mathrm{eVAr^{+}}$  The final portion of the ion bombardment step (purple dashed-dotted line) is used to calculate the etch yield shown as the purple dashed-dotted line. The purple dashed-dotted line is extrapolated to the estimated experimental  $\mathsf{Ar}^+$  fluence.

This multi-axis chart illustrates the relationship between species dosage (Cl₂ or Ar⁺/cm²) and two parameters: Si etching depth and chlorine uptake. The red curve (left y-axis) represents silicon etching at 100 eV Ar⁺, which begins only after Cl₂ exposure has saturated the surface. Etching increases steadily with Ar⁺ dosage and plateaus at ~9.8 Å, indicating the removal of one atomic layer of Si. The blue curve (right y-axis) shows Cl uptake, which rises quickly during Cl₂ exposure and saturates around 1.35 × 10¹⁵ Cl/cm². The dashed lines and arrows illustrate the sequential process: first Cl uptake during Cl₂ exposure, followed by Si etching upon Ar⁺ bombardment, revealing a synergistic etch mechanism.

| Species Dosage (Cl₂ or Ar⁺/cm²) × 10¹⁵ | Si Etched (Å) | Cl Uptake (Cl/cm²) × 10¹⁵ |
|----------------------------------------|---------------|----------------------------|
| 0                                      | 0             | 0                          |
| 10                                     | 0             | 0.75                       |
| 20                                     | 0             | 1.25                       |
| 25                                     | 0             | 1.35                       |
| 30                                     | 1.5           | 1.35                       |
| 50                                     | 4             | 1.35                       |
| 75                                     | 6.5           | 1.35                       |
| 100                                    | 9.0           | 1.35                       |
| 125                                    | 9.8           | 1.35                       |

Answer: Chlorine uptake increases rapidly during initial Cl₂ exposure and saturates near 1.35 × 10¹⁵ Cl/cm², showing a self-limiting surface reaction. In contrast, silicon etching does not begin during Cl₂ exposure but increases progressively during the Ar⁺ dosage phase. This distinction highlights that Cl₂ alone does not etch Si, but pre-functionalises the surface, enabling etching when energy is provided by Ar⁺ bombardment. The etching depth reaches a maximum around 9.8 Å, corresponding to the removal of a single Si layer.

Answer: 1.35 × 10¹⁵ Cl/cm².

Answer: Cl adsorption, Surface saturation, Ar⁺ bombardment, Si–Cl bond breaking, Silicon etching

Answer: No


FIG. 11. Al2p XPS peak area and peak binding energy after 30 ALE cycles as a function of table temperature. The binding energies of  $\mathrm{AlF}_3$  and  $\mathrm{Al}_2\mathrm{O}_3$  have been included as dashed lines to show the transition between the two binding environments. The insets show the fitted Al2p XPS spectra for the films etched at 100 and  $200^{\circ}\mathrm{C}$ .

The chart shows the relationship between the table temperature and the Al2p peak area and peak binding energy of AlF3 and Al2O3.

The inset spectra chart displays the intensity of Al2p peaks at different binding energies.

| Table temperature°C | Al2p peak area (CPS eV) | Peak binding energy (eV) |
|---|---|---|
| 100 | 17000 | 76.0 |
| 125 | 17000 | 76.0 |
| 150 | 15000 | 76.0 |
| 175 | 5000 | 75.7|
| 200 | 2000 | 74.7 |
| 225 | 2000 | 74.5 |
| 250 | 2000 | 74.7 |
| 275 | 2000 | 74.5 |
| 300 | 2000 | 74.6 |

| Binding energy (eV) | Intensity (CPS) |
|---|---|
| 72 | 0 |
| 74 | 0 |
| 76 | Peak |
| 78 | 0 |
| 80 | 0 |

Answer: It seems that upon etching there is a shift in binding energy.

Answer: All data points are from films after 30 cycles of etching. There is way less al2p peak intensity for 200 degrees celcius indicating a higher EPC.

Answer: A reason could be that fluorine species get more volatile at higher temperatures, meaning they will leave the surface, resulting in more Al2O3.

Answer: Temperatures above 200 degrees celcius show almost no fluorine.

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