FIG. 10. (Color online) The raw SE data (experimental) and the fit (simulated by Lorentz model) for  $\Delta$  and  $\Psi$  are shown as a function of photon energy for  $\mathrm{Ga}_2\mathrm{O}_3$  thin film deposited by PEALD at  $200^{\circ}\mathrm{C}$  and annealed at the temperature of  $500^{\circ}\mathrm{C}$ .

The multiple line charts represents the experimental Spectroscopic ellipsometry (SE) measurements of ψ against photon energy and fitted (simulated by Lorentz model)  for various angles (65°, 70°, 75°)

The multiple line charts represents the experimental Spectroscopic ellipsometry (SE) measurements of Δ against  photon energy and fitted (simulated by Lorentz model)  for various angles (65°, 70°, 75°), the angles were represented in different symbols and fitted line is in red for ψ and green for Δ.

| Photon Energy (eV) | ψ (degrees) | Experimental ψ (degrees) |
|--------------------|-------------|---------------------------|
| 1.5                | 26.97       | 65                        |
| 1.5                | 24.24       | 70                        |
| 1.5                | 23.21       | 75                        |
| 2.0                | 36.48       | 65                        |
| 2.0                | 33.23       | 70                        |
| 2.0                | 32.83       | 75                        |
| 2.5                | 52.22       | 65                        |
| 2.5                | 50.01       | 70                        |
| 2.5                | 47.55       | 75                        |
| 3.0                | 61.21       | 65                        |
| 3.0                | 59.27       | 70                        |
| 3.0                | 52.11       | 75                        |
| 3.5                | 37.53       | 65                        |
| 3.5                | 35.04       | 70                        |
| 3.5                | 35.96       | 75                        |
| 4.0                | 31.29       | 65                        |
| 4.0                | 30.10       | 70                        |
| 4.0                | 28.50       | 75                        |

| Photon Energy (eV) | Δ (degrees) | Experimental Δ (degrees) |
|--------------------|-------------|---------------------------|
| 1.5                | 52.45       | 65                        |
| 1.5                | 74.23       | 70                        |
| 1.5                | 94.95       | 75                        |
| 2.0                | 44.08       | 65                        |
| 2.0                | 60.44       | 70                        |
| 2.0                | 77.54       | 75                        |
| 2.5                | 29.22       | 65                        |
| 2.5                | 38.28       | 70                        |
| 2.5                | 52.07       | 75                        |
| 3.0                | 29.91       | 65                        |
| 3.0                | 45.89       | 70                        |
| 3.0                | 59.69       | 75                        |
| 3.5                | 63.37       | 65                        |
| 3.5                | 82.97       | 70                        |
| 3.5                | 103.00      | 75                        |
| 4.0                | 93.52       | 65                        |
| 4.0                | 117.11      | 70                        |
| 4.0                | 135.28      | 75                        |

Answer: Currently, the spectra in the 1.5–2.5 eV range are relatively smooth, indicating the film is likely thin enough that interference fringes are broad or minimal. If the thickness were doubled, the path length difference would increase, causing more rapid constructive and destructive interference. This would result in the appearance of distinct oscillatory fringes (waves) in both  ψ and Δ within this transparent lower-energy region.

Answer:
Acquire raw SE data (ψ and Δ spectra) at multiple angles.
Construct an optical model stack (Substrate / Thin Film / Ambient).
Select a dispersion relation (Lorentz oscillator) to parameterize the film's dielectric function.
Perform regression analysis (Levenberg-Marquardt) to minimize Mean Squared Error (MSE) between the model and experiment.

Answer: Yes, the Lorentz model is effective and the film structure is uniform.The fit is excellent across the entire spectral range and all three angles, as shown by the solid lines passing directly through the center of the symbols. This robust multi-angle agreement implies that the film is optically isotropic and homogeneous;

Answer: The feature corresponds to an interband electronic transition or optical absorption edge.

icdar2026-competition-data/dev/atomic-layer-deposition/experimental-usecase/17/F. K. Shan et al.pdf


FIG. 11. (Color online) Extracted refractive indices of  $\mathrm{Ga}_{2}\mathrm{O}_{3}$  thin films deposited by PEALD at  $200^{\circ}\mathrm{C}$  and annealed at various RTA temperatures by Lorentz simulation.

The multiple line charts represents the variation of refractive index (n) of Ga₂O₃ thin films extracted from Lorentz simulation against photon energy (eV) for different thermal treatments (As-deposit, 500°C, 700°C, and 900°C). The refractive index clearly increases with increasing photon energy.

| Photon Energy (eV) | Refractive Index (n) | Condition      |
|--------------------|-----------------------|----------------|
| 1.5                | 1.82                  | As-deposit     |
| 1.5                | 1.83                  | 500            |
| 1.5                | 1.92                  | 700            |
| 1.5                | 1.92                  | 900            |
| 2.0                | 1.85                  | As-deposit     |
| 2.0                | 1.86                  | 500            |
| 2.0                | 1.94                  | 700            |
| 2.0                | 1.95                  | 900            |
| 2.5                | 1.89                  | As-deposit     |
| 2.5                | 1.90                  | 500            |
| 2.5                | 1.99                  | 700            |
| 2.5                | 1.98                  | 900            |
| 3.0                | 1.95                  | As-deposit     |
| 3.0                | 1.96                  | 500            |
| 3.0                | 2.04                  | 700            |
| 3.0                | 2.04                  | 900            |
| 3.5                | 2.03                  | As-deposit     |
| 3.5                | 2.03                  | 500            |
| 3.5                | 2.11                  | 700            |
| 3.5                | 2.10                  | 900            |
| 4.0                | 2.14                  | As-deposit     |
| 4.0                | 2.15                  | 500            |
| 4.0                | 2.20                  | 700            |
| 4.0                | 2.19                  | 900            |

Answer:
As deposited
, 500 °C
, 700 °C
, 900 °C

Answer: The 900°C annealing route is invalid due to the temperature constraint. The trade-off is clear: higher annealing temperatures (700°C, 900°C) provide a higher refractive index (better for index contrast) but require a high thermal budget that may damage underlying layers or substrates. The lower-temperature or as-deposited films offer lower thermal budget but also lower refractive index and likely poorer film quality.

Answer: Increasing the annealing temperature generally increases the refractive index. This is because higher temperature annealing promotes densification and enhanced crystallinity, reducing porosity and increasing the atomic packing density. A denser material with fewer voids has a higher polarizability, leading to a higher refractive index.

Answer: A higher refractive index implies that the annealed Ga₂O₃ film provides a stronger optical confinement (a larger index contrast with the substrate or cladding). This allows for the design of thinner waveguide cores while still effectively confining the light mode, enabling more compact integrated photonic devices compared to using the lower-index, as-deposited film.


FIG. 3. (Color online) Auger depth profile of as-deposited  $\mathrm{Ga}_{2}\mathrm{O}_{3}$  thin film. The analysis was done by using  $4\mathrm{keV}$  As-ions. The nominal steh rate was  $0.2\mathrm{\AA / s}$ . The film is homogeneous and stoichiometric.

The multiple-line chart shows the Auger depth profile of the as-deposited Ga₂O₃ films as a function of sputter time. Si corresponds to the substrate, and small traces of carbon are also detected. Clear and well-defined Ga and O intensitites are observed throughout the profile.

| Sputter time (a.u.) | O intensity (%) | Ga intensity (%) | Si intensity (%) | C intensity (%) |
|---------------------|-----------------|------------------|------------------|-----------------|
| 0                   | 53              | 35               | 0                | 2               |
| 1                   | 53              | 34               | 0                | 2               |
| 2                   | 52              | 33               | 0                | 2               |
| 3                   | 52              | 33               | 0                | 2               |
| 4                   | 51              | 32               | 1                | 2               |
| 5                   | 50              | 31               | 3                | 2               |
| 6                   | 47              | 29               | 8                | 2               |
| 7                   | 40              | 25               | 25               | 2               |
| 8                   | 25              | 15               | 60               | 1               |
| 9                   | 5               | 2                | 90                | 0               |
| 10                  | 0               | 0                | 93               | 0               |

Answer: Surface/Bulk Ga₂O₃ Film (High O and Ga signal).Interface Region - Crossover of signals.Silicon Substrate - High Si signal.

Answer:
AES with High-Energy Ions: Pro: Faster sputtering. Con: Can cause more atomic mixing and roughening, distorting depth resolution.

XPS with Low-Energy Ions: Pro: Better depth resolution and more accurate quantification of light elements due to gentler sputtering.

Choice: For accurate light-element quantification with minimal distortion, XPS with low-energy ions is preferable. The trade-off is slower data acquisition, but it preserves interfacial sharpness for more reliable profiling.

Answer: The observed O/Ga intensity ratio is approximately 1.6 (54%/32%), close to the theoretical stoichiometric ratio of 1.5.

Answer: NO , While the sharp interface and low bulk carbon are positive, the as-deposited film likely has a high density of point defects and disorder (as suggested by the lower refractive index in the previous figure). These defects would act as charge traps, leading to poor channel mobility and unstable threshold voltage in a HEMT. Post-deposition annealing is typically required to reduce these defects and improve dielectric quality.


FIG. 6. (Color online) Leakage current curves of the  $\mathrm{Pt / Ga}_{2}\mathrm{O}_{3} / \mathrm{Si}$  structured thin films.

The muliple line chart  shows  the current density (A/cm²) as a function of gate voltage (V) for Ga₂O₃-based devices subjected to different post-deposition annealing temperatures: As-grown,500 °C,700 °C,900 °C. As-grown and 500 °C samples show higher current density, especially near 0 to –4 V, indicating higher leakage current. As annealing temperature increases to 700 °C and 900 °C, the current density decreases significantly, showing improved insulating behavior and lower leakage.

| Gate Voltage (V) | Current Density (A/cm²) | temperature |
|---|---|---|
| 0 | 10^-7 | As-grown |
| 0 | 10^-8 | 500 °C |
| 0 | 10^-7 | 700 °C |
| 0 | 10^-8 | 900 °C |
|-3 | 10^-2 | As-grown |
|-3 | 10^-3 | 500 °C |
|-3 | 10^-7 | 700 °C |
|-3 | 10^-7 | 900 °C |
|-6 | 10^-2 | As-grown |
|-6 | 10^-2 | 500 °C |
|-6 | 10^-7 | 700 °C |
|-6 | 10^-7 | 900 °C |
|-9 | -     | As-grown |
|-9 | -     | 500 °C |
|-9 | 10^-6 | 700 °C |
|-9 | 10^-7 | 900 °C |
| -12| - | As-grown |
| -12| - | 500 °C |
| -12| 10^-5 | 700 °C |
| -12| 10^-6 | 900 °C |

Answer:
As-grown

, 500 °C

, 700 °C

, 900 °C

Answer: As-grown and 500 °C samples show higher current density, especially near 0 to –4 V, indicating higher leakage current.As annealing temperature increases to 700 °C and 900 °C, the current density decreases significantly, showing improved insulating behavior and lower leakage.

Answer: As-grown and 500 °C samples show higher current density, particularly between 0 and –4 V, indicating increased leakage current. In contrast, annealing at 700 °C and 900 °C significantly reduces the current density, with the 900 °C sample exhibiting the lowest leakage (≈10⁻⁹ A/cm²) due to improved oxide quality and defect reduction. Overall, higher annealing temperatures enhance dielectric stability, reduce defects, and improve the insulating behavior and performance of the films.

Answer: A 900°C annealed film would be essential as a gate oxide in a high-performance transistor. Its ultra-low leakage current (~10⁻⁹ A/cm²) minimizes static power consumption and prevents unwanted signal loss. The as-grown film's higher leakage would cause excessive power dissipation and unreliable switching, rendering it unsuitable for modern low-power electronics.


FIG. 8. (Color online) Transmission spectra of as-deposited  $\mathrm{Ga}_2\mathrm{O}_3$  thin film and of those annealed at various RTA temperatures. The inset is the bandgap energies of the thin films.

The main figure displays the optical transmission spectra of Ga2O3 thin films as a function of wavelength for various annealing temperatures (As-deposited, 500°C, 700°C, and 900°C). The data reveals a noticeable "blue shift" of the absorption edge toward shorter wavelengths as the temperature increases, indicating an increase in transparency at the UV edge.

The inset figure plots the extracted optical band gap energy (Eg) against the annealing temperature. The trend confirms a significant widening of the band gap, increasing from approximately 5.00 eV for the as-deposited sample to nearly 5.25 eV for the sample annealed at 900°C, likely due to improved crystallinity.

| Wavelength (nm) | Transmission (%) | Condition      |
|------------------|-------------------|----------------|
| 200              | 20                | As-deposited   |
| 200              | 20                | 500°C          |
| 200              | 20                | 700°C          |
| 200              | 20                | 900°C          |
| 250              | 40                | As-deposited   |
| 250              | 40                | 500°C          |
| 250              | 40                | 700°C          |
| 250              | 40                | 900°C          |
| 300              | 60                | As-deposited   |
| 300              | 60                | 500°C          |
| 300              | 60                | 700°C          |
| 300              | 60                | 900°C          |
| 350              | 80                | As-deposited   |
| 350              | 80                | 500°C          |
| 350              | 80                | 700°C          |
| 350              | 80                | 900°C          |
| 400              | 100               | As-deposited   |
| 400              | 100               | 500°C          |
| 400              | 100               | 700°C          |
| 400              | 100               | 900°C          |
| 450              | 100               | As-deposited   |
| 450              | 100               | 500°C          |
| 450              | 100               | 700°C          |
| 450              | 100               | 900°C          |
| 500              | 100               | As-deposited   |
| 500              | 100               | 500°C          |
| 500              | 100               | 700°C          |
| 500              | 100               | 900°C          |
| 550              | 100               | As-deposited   |
| 550              | 100               | 500°C          |
| 550              | 100               | 700°C          |
| 550              | 100               | 900°C          |
| 600              | 100               | As-deposited   |
| 600              | 100               | 500°C          |
| 600              | 100               | 700°C          |
| 600              | 100               | 900°C          |
| 650              | 100               | As-deposited   |
| 650              | 100               | 500°C          |
| 650              | 100               | 700°C          |
| 650              | 100               | 900°C          |
| 700              | 100               | As-deposited   |
| 700              | 100               | 500°C          |
| 700              | 100               | 700°C          |
| 700              | 100               | 900°C          |

| Temperature (°C) | Band Gap Energy (eV) |
|------------------|----------------------|
| 200              | 5.0                  |
| 400              | 5.1                  |
| 600              | 5.2                  |
|800               | 5.26               |

Answer: The most significant change occurs between 500°C and 700°C.

Answer: The band gap decreases as temperature increases. This is primarily caused by thermal lattice expansion, which increases the interatomic spacing and reduces the potential felt by electrons, lowering the energy required for electronic transitions. Additionally, increased electron-phonon interactions at higher temperatures contribute to this band gap narrowing.

Answer: Transmission spectroscopy is more practical for high-throughput screening. While photoreflectance can offer more precise determination of critical points in the dielectric function, transmission measurement is experimentally simpler, faster, and requires less complex sample preparation (e.g., no need for a Schottky contact), allowing for rapid collection of data across many samples and temperatures.

Answer:
No.

The strong temperature-dependent band gap shift means the LED's emitted UV wavelength would change significantly with operating temperature, leading to unstable output color and intensity. For a temperature-stable device, a material with a smaller temperature coefficient of the band gap (dEg/dT) is required to minimize this performance drift.


FIG.4.a  $CV(100\mathrm{kHz})$  curves and inset  $JV$  same legend) for nominal 3, 9,and  $15\mathrm{nm}$  thick ALD  $\mathrm{HfO_2}$  layers on  $50^{\circ}\mathrm{C}$  in situ passivated InGaAs. The actual  $\mathrm{HfO_2}$  and IL) thicknesses from TEM were  $3\mathrm{nm}$ $0.8\mathrm{nm}$  IL),  $9.4~\mathrm{nm}$ $0.8~\mathrm{nm}$  IL),and  $16.8~\mathrm{nm}$ $0.9 \mathrm{nm}$  IL).No significant degradation of the bulk and interface properties is observed after repeated  $CV$  measurement of the MOS structures. (b)  $CV$ $\mathrm{(H_2KHz)}$  and inset  $JV$  same legend) characteristics for in situ  $50^{\circ}\mathrm{C}$ $\mathrm{H}_2\mathrm{S}$  passivated and ex situ aqueous  $(\mathrm{NH_4})_2\mathrm{S}$  passivated devices.

The figure shows the capacitance (C) as a function of gate bias (Vg) for different film thicknesses of HfO2 gate dielectric layer (3nm, 9.4nm, 16.8nm). The channel layer is passivated in situ at 50°C. The inset shows the current density (J) as a function of gate bias.

The figure shows the capacitance (C) as a function of gate bias (Vg) for two different passivations, ex-situ ((NH4)2S and  in situ  H2S) at 50°C. The inset shows the current density (J) as a function of gate bias.

| Gate Bias Vg (V) | 3 nm   | 9.4 nm | 16.8 nm |
|-----------------------------|--------|--------|---------|
| -2                          | 0.003  | 0.0025 | 0.002  |
| -1                          | 0.004  | 0.003  | 0.0022 |
| -0.5                        | 0.005  | 0.004  | 0.0025 |
| 0                           | 0.006  | 0.005  | 0.003  |
| 0.5                         | 0.008  | 0.0065 | 0.004  |
| 1                           | 0.010  | 0.008  | 0.005  |
| 1.5                         | 0.0115 | 0.0095 | 0.006  |
| 2                           | 0.0125 | 0.0105 | 0.007  |
| 2.5                         | 0.013  | 0.0115 | 0.0078 |
| 3                           | 0.0135 | 0.012  | 0.0085 |

| Gate Bias Vg (V) | (NH4)2S | 50°C H2S |
|-----------------------------|-------------------------------|----------------------|
| -2                          | 0.003                        | 0.0028              |
| -1                          | 0.004                        | 0.0035              |
| -0.5                        | 0.005                        | 0.0045              |
| 0                           | 0.006                        | 0.0055              |
| 0.5                         | 0.0075                       | 0.0068              |
| 1                           | 0.0085                       | 0.0078              |
| 1.5                         | 0.009                        | 0.0085              |
| 2                           | 0.0095                       | 0.009               |
| 2.5                         | 0.0098                       | 0.0095              |
| 3                           | 0.010                        | 0.0098              |

Answer: VFB (Flat-Band Voltage) is the applied gate voltage where the semiconductor's energy bands are flat (no bending), indicating zero net charge in the semiconductor. In figure b, flat band voltages would be approximately -2 to -1

Answer: Although a slight Vfb shift is apparent, a similar profile is observed in the CV curves of both devices. Both devices have a similar Cmax in accumulation while the in situ passivated device appears to have slightly higher interface state density. The JV plot in the inset of (b) shows similar leakage current density at 1 V with a higher electric breakdown field for the in situ passivated device. This demonstrates that the in situ passivation approach employed in this work can achieve results comparable to those obtained using ex situ aqueous (NH4)2S passivation.

Answer: No

Answer:
The leakage current densities at 1 V are
1. For the 3 nm device, ~2x10^−6 A/cm2
2. For the 9.4 nm device, ~3x10^−8 A/cm2
3. For the 16.8nm device, ~2x10^−8 A/cm2


FIG. 2. (a) High frequency  $(100\mathrm{kHz})$  capacitance-voltage characteristics and inset leakage current density as a function of gate bias (same legend), for unpassivated and in situ passivated  $\mathrm{Pd / 9nm}$  nominal ALD  $\mathrm{HfO_2 / InGaAs / InP}$  MOS devices. (b) Multiple frequency  $CV$ , and inset hysteresis, curves for in situ  $50^{\circ}\mathrm{C}$ $\mathrm{H}_2\mathrm{S}$  passivated InGaAs MOS device. No capacitance correction was made for inductive and resistive elements in the circuit. The average frequency dispersion of the flatband capacitance  $C_{\mathrm{fb}}$ , is  $< 3.5\%$  per decade for all devices. The hysteresis measured around  $C_{\mathrm{fb}}$  at  $100\mathrm{kHz}$  was  $460\mathrm{mV}$  for the unpassivated device, and 380, 585, and  $410\mathrm{mV}$  for the 50, 200, and  $350^{\circ}\mathrm{C}$  in situ  $\mathrm{H}_2\mathrm{S}$  passivated devices, respectively.

The figure shows the capacitance (C) of a device as a function of gate bias (Vg) at various temperatures of hydrogen sulfide (H2S) passivation ( 50 °C, 200 °C and 350 °C) along with unpassivated sample for comparison. The inset provides a closer view of the current density (J) against gate bias.

The figure illustrates the capacitance (C) of a device as a function of gate bias (Vg) at different frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz) for the 50 °C H2S passivated sample. The inset provides a closer view of the capacitance at 100 kHz.

| Gate Bias Vg (V) | Unpassivated | 350°C H2S | 200°C H2S | 50°C H2S |
|-----------------------------|--------------|-----------------------|-----------------------|----------------------|
| -2                          | 0.0028       | 0.0026               | 0.0024               | 0.0022              |
| -1                          | 0.003        | 0.0028               | 0.0026                | 0.0024              |
| 0                           | 0.005        | 0.004               | 0.004                   | 0.0038              |
| 1                           | 0.006        | 0.0068              | 0.0058                 | 0.0080              |
| 2                           | 0.0072       | 0.0074              | 0.0062               | 0.0090              |
| 3                           | 0.0078       | 0.0080               | 0.0070               | 0.0010              |

Answer:
No the inset shows only the minimum hysteresis observed for   50 °C device. The hysteresis measured around Cfb at 100 kHz  is as follows,
1. 460 mV for the unpassivated device
2. 380 mV for the 50 °C in situ H2S passivated device
3. 585 mV for the 200 °C in situ H2S passivated device
4. 410 mV  for the 350 °C in situ H2S passivated device

Answer: The fact that the 50 °C passivated device, which XPS showed to have no detectable S signal at the surface, displays the best electrical properties is further evidence that S is not the primary passivating element for the in situ process. It is possible to speculate that hydrogen may be passivating the InGaAs surface. One possibility is low temperature dissociative adsorption of H2S to produce H–S and H species which may bond to As at the epitaxial layer surface.

Answer:
The minimum capacitance Cmin,  at Vg =−2 V,
1. Unpassivated sample = 0.0028   F/m2
2. Passivated at 350 °C = 0.0026  F/m2
3. Passivated at 200 °C = 0.0024  F/m2
4. Passivated at 50 °C= 0.0022 F/m2

Answer: The  in situ passivated surface at 50 °C device displays the highest maximum capacitance ( accumulation Cmax) and also exhibits the sharpest transition from minimum (depletion to accumulation).


Fig. 2. Thermogravimetric analysis of  $\mathrm{Al(DEA)}_3$  and  $\mathrm{Al(DIA)}_3$  at atmospheric pressure and  $50~\mathrm{cc / min}$  He purge gas at a  $10^{\circ}\mathrm{C / min}$  heating rate.

The line chart shows the weight percentage (Wt %) of  Al (DEA)_3 and Al (DIA)_3, as a function of temperature. Both compounds exhibit a sharp decrease in weight percentage starting around 200°C, with Al (DEA)_3 having a slightly higher initial weight percentage.

| Temperature | Al (DEA)_3 | Al (DIA)_3 |
|---|---|---|
| 0 | 100 | 100 |
| 100 | 100 | 100 |
| 200 | 95 | 55 |
| 300 | 12 | 15 |
| 400 | 10 | 12 |
| 500 | 10 | 10 |
| 600 | 10 | 10 |

Answer: The figure shows a thermogravimetric analysis of Al(DEA)3 and Al(DIA)3 with the atomic percentage plotted as a function of temperature.

Answer: Al(DEA)3 evaporates at approximately 200 °C, while Al(DIA)3 evaporates at 150 °C.

Answer: At 200°C, the atomic percentage of Al(DEA)3 is nearly 100%.

Answer: It reveals information about the thermal stability of compounds.


This figure compares optical transmittance spectra of bare glass and NiO films deposited using different precursors over the 300–1000 nm wavelength range. All NiO-coated samples show reduced transmittance relative to bare glass, particularly in the near-UV region. Among the NiO films, the Bu-MeAMD-derived film consistently exhibits the highest transmittance, followed by the MeCp-based film, while the Alanis-based film shows the lowest transmittance across most of the visible range. The spectra flatten at longer wavelengths, indicating relatively stable optical behavior in the visible to near-infrared region.

| Wavelength (nm) | Glass (%) | NiO_Alanis (%) | NiO_MeCp (%) | NiO_Bu-MeAMD (%) |
|-----------------|-----------|----------------|--------------|------------------|
| 300             | ~12       | ~10            | ~10          | ~10              |
| 350             | ~88       | ~70            | ~78          | ~85              |
| 400             | ~90       | ~75            | ~82          | ~88              |
| 450             | ~92       | ~78            | ~85          | ~90              |
| 500             | ~93       | ~80            | ~86          | ~91              |
| 600             | ~92       | ~81            | ~87          | ~92              |
| 700             | ~91       | ~80            | ~86          | ~91              |
| 800             | ~90       | ~80            | ~85          | ~90              |
| 900             | ~89       | ~81            | ~85          | ~89              |
| 1000            | ~88       | ~82            | ~86          | ~90              |

Answer: Bu-MeAMD shows the highest transmittance, followed by MeCp, with Alanis consistently lowest.

Answer: Higher transmittance can result from lower defect density, reduced absorption centers, or differences in film thickness and density. The Bu-MeAMD process may produce a more uniform film or fewer optically active defects, allowing greater light transmission.

Answer:
-Film thickness
-Surface roughness
-Grain size and microstructure
-Defect and impurity concentration
-Precursor chemistry and reaction completeness

Answer: No

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


(b)

The figure compares the optical absorption coefficients of NiO films deposited using three different precursors. All films show strong absorption in the UV region followed by a gradual decrease toward the visible and near-infrared. Across the full wavelength range, NiO_Alanis exhibits the highest absorption, NiO_MeCp shows intermediate behavior, and NiO_Bu-MeAMD displays the weakest absorption. The systematic separation between the curves indicates that precursor chemistry influences film density, defect concentration, or electronic structure, which in turn affects optical absorption.

| Wavelength (nm) | NiO_Alanis (cm⁻¹) | NiO_MeCp (cm⁻¹) | NiO_Bu-MeAMD (cm⁻¹) |
|---|---|---|---|
| 300 | ~3.5×10⁵ | ~3.0×10⁵ | ~1.5×10⁵ |
| 350 | ~1.2×10⁵ | ~8×10⁴ |  0  |
| 400 | ~1.1×10⁵ | ~7×10⁴ |  0  |
| 500 | ~1.0×10⁵ | ~6×10⁴ |   0   |
| 700 | ~8×10⁴  | ~5×10⁴ |   0    |
| 1000| ~6×10⁴  | ~4×10⁴ |  0    |

Answer: At shorter wavelengths, photons have enough energy to excite electronic transitions across the band gap or defect states, leading to strong absorption. As the wavelength increases, photon energy decreases, and fewer transitions are available, so absorption gradually weakens.

Answer: NiO_Alanis shows the highest absorption across the full wavelength range.

Answer: Lower absorption may indicate a lower defect density, reduced free-carrier concentration, or differences in film density and microstructure. These factors depend strongly on precursor chemistry and growth conditions.

Answer: Optical absorption directly affects transparency, photoconductivity, and light–matter interaction. Choosing a film with the appropriate absorption profile is essential for applications such as transparent electronics, sensors, or photovoltaic interfaces.


Fig. 10. Comparison of reaction energetics for  $\mathrm{H}_2\mathrm{O}$  reaction on the (A)  $\mathrm{SiO}_2\mathrm{-O - ZrCl}_3$  surface site, (B)  $\mathrm{Zr - O - ZrCl}_3^*$  surface site, and (C)  $\mathrm{Si - O - ZrCl}_3$  surface site.

The line chart illustrates the energy change (ΔE) in kcal/mol for different during the reaction of water with different substrates (A, B, and C).

| Reaction part | delta E, A |delta E, B |delta E, C |
| --- | --- | --- | --- |
|Start|0|0|0|
|Complex|-17|-15|-17|
| TS | 3 | 4 | 4 |
| HCl(a) | -5 | -2 | 0 |
| HCl(g) | 0 | 3 | 3 |

Answer: The reaction that costs the least energy is pathway B, this shows the least negative delta E.

Answer: It is clear that also the substrate matters. This seems to suggest that there is also an interaction of either the silicon or the zirconium with the HCl.

Answer: That there is no energy gain by reaction as well as no energy loss.

Answer: The lowest recorded delta E is -17 kcal/mol.

icdar2026-competition-data/dev/atomic-layer-deposition/simulation-usecase/24/Joseph H. Han et al.pdf


Fig. 4. PESs of  $\mathrm{H}_2\mathrm{O}$  reaction with all three Cl atoms on  $\mathrm{Zr}$ , calculated using the  $\mathrm{Si(OH)_3SiOZrCl_3}$  cluster for (A) removal of the first Cl atom, (B) removal of the second Cl atom, and (C) removal of the third Cl atom.

The chart illustrates the change in energy (ΔE) in kcal/mol for different steps in the reaction of chlorine groups at the surface with water, for the first (A), second (B), and third (C) chlorine group at the surface.

| Reaction Step | ΔE (kcal/mol) A |ΔE (kcal/mol) B |ΔE (kcal/mol) C |
|---|---|---|---|
| Start | 0 |0 |0 |
| Complex | -18|-17|-15|
| TS | 4|4|0|
| HCl (a) | -1|-3|-2|
| HCl (g)| 0.5|5|7|

Answer: The third chlorine group, this can be seen by the fact that this reaction has the lowest energy barrier.

Answer: This depends on which chlorine group has been removed. For the last chlorine group, more energy is required to have a transision of HCl (a) to HCl (g).

Answer: The energy barrier is 21 kcal/mol.

Answer: Yes this can be said, as the energy envolved decreases, for increasing number of removed chlorine groups.


Fig. 8. PESs calculated using the  $\mathrm{(SiH_3O)_3SiOZrCl_3}$  cluster for reaction of (A) removal of the first Cl atom, (B) removal of the second Cl atom, and (C) removal of the third Cl atom.

The line chart shows the energy (E) in kcal/mol during the reaction step where a chlorine group reacts with water, for either the first (A), the second (B), or the third (C) chlorine group.

| Reaction Step | ΔE (kcal/mol) A |ΔE (kcal/mol) B |ΔE (kcal/mol) C |
|---|---|---|---|
| Start | 0 |0 |0 |
| Complex | -17|-15|-15|
| TS |3|3|3|
| HCl (a) | -1| 0|2|
| HCl (g)| 2| 5|8|

Answer: The second and third chlorine atoms are equally easy to be removed as they have the same activation energy, which is lower than the one of the first chlorine atom.

Answer: 19 kcal/mol

Answer: 59 kcal/mol

Answer: The precursor only adsorbs to hydroxyl groups so at least one is required. More is better as this will lead to higher quality films.


Fig. 9. Comparison of reaction energetics for  $\mathrm{ZrCl_4}$  reaction on the (A)  $\mathrm{SiO_2 - OH^*}$  surface site, (B)  $\mathrm{Zr - OH^*}$  surface site, and (C)  $\mathrm{Si - OH^*}$  surface site.

The chart shows the energy change (ΔE) in kcal/mol for the reaction of ZrCl4 with different substrate complexes labeled A, B, and C.

| Reaction Step | ΔE (kcal/mol) A |ΔE (kcal/mol) B |ΔE (kcal/mol) C |
|---|---|---|---|
| Start | 0 |0 |0 |
| Complex | -17|-21|-28|
| TS | 0| -2|-8|
| HCl (g)| -5| -7|-12|

Answer: Yes there is faster saturation as there is less energy required for adsorption on SiO2 than on ZrO2.

Answer: SiO2 instead of Si or ZrO2 as this material shows the lowest activation energy.

Answer: 21 kcal/mol

Answer: C


FIG. 5. "Saturation curves" showing self-limiting removal in (a) ALE for small EPC, (b) ALE for larger EPC, and (c) ALE quasi-self-limiting. In curve (d), continuous etching is shown for comparable etch time to illustrate lack of self-limiting behavior.

icdar2026-competition-data/dev/atomic-layer-etching/experimental-usecase/15/Overview of atomic layer etching in the semiconductor industry.pdf


FIG. 7. Plasma-assisted silicon ALE, after etching  $50\mathrm{nm}$  directionally. The results show characteristic ALE benefits at all length scales: (a) excellent depth uniformity across the wafer, (b) flat silicon etch front on the feature, and (c) smooth surface. Reprinted with permission from Kanarik et al., Solid State Technol., 56, 24 (2013). Copyright 2013, Lam Research Corporation.


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

The line chart shows the film thickness of various materials (TiN, Al₂O₃, Si₃N₄, HfO₂, ZrO₂, SiO₂) over cycles at 250°C using O₃ & HF.

| Number of Cycles | TiN | Al₂O₃ | Si₃N₄ | HfO₂ | ZrO₂ | SiO₂ |
|---|---|---|---|---|---|---|
| 0 | 75 | 40 | 40 | 55 | 55 | 55 |
| 100 | 60 | 40 | 40 | 55 | 55 | 55 |
| 200 | 45 | 40 | 40 | 55 | 55 | 55 |
| 300 | 30 | 40 | 40 | 55 | 55 | 55 |
| 400 | 15 | 40 | 40 | 55 | 55 | 55 |

Answer: Only TiN is etched; Al₂O₃, HfO₂, ZrO₂, SiO₂, and Si₃N₄ show negligible thickness change.

Answer: These oxides form stable, nonvolatile fluorides (AlF₃, HfF₄, ZrF₄) when exposed to HF. Unlike TiN which forms volatile TiF₄, these metal fluorides remain on the surface and do not desorb, preventing net material removal in the oxidation-fluorination mechanism.

Answer: Approximately 0.20 Å/cycle, calculated from roughly 55 Å removal over about 300 cycles.

Answer: TiN is used as gate electrode material in CMOS and as a copper diffusion barrier, requiring selective removal without damaging surrounding dielectric materials.

icdar2026-competition-data/dev/atomic-layer-etching/experimental-usecase/19/Thermal atomic layer etching Mechanism, materials and prospects.pdf


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

Shows film thickness versus ALE cycles using Sn(acac)₂ and HF at 200°C. Al₂O₃, HfO₂, and ZrO₂ show linear thickness decrease (etchable), while SiO₂, Si₃N₄, and TiN remain constant (not etchable), demonstrating material selectivity.

Shows film thickness versus ALE cycles using TMA and HF at 300°C. Al₂O₃ and HfO₂ are etched, ZrO₂ shows slight etching, while SiO₂, Si₃N₄, and TiN are not etched, demonstrating different selectivity compared to Sn(acac)₂.

| Number of Cycles | TiN (Å) | SiO2 (Å) | HfO2 (Å) | Si3N4 (Å) | ZrO2 (Å) | Al2O3 (Å) |
|---|---|---|---|---|---|---|
| 0 | 68 | 49 | 52 | 39 | 48 | 47 |
| 50 | 70 | 48 | 52 | 40 | 47 | 35 |
| 100 | 69 | 47 | 50 | 40 | 42 | 23 |
| 200 | 69 | 47 | 45 | 40 | 28 | 0 |
| 400 | 69 | 46 | 33 | 39 | 0 | - |

| Number of Cycles | TiN (Å) | SiO2 (Å) | HfO2 (Å) | Si3N4 (Å) | ZrO2 (Å) | Al2O3 (Å) |
|---|---|---|---|---|---|---|
| 0 | 68 | 50 | 52 | 39 | 48 | 47 |
| 50 | - | 49 | 51 | - | 52 | 34 |
| 100 | - | 48 | 49 | - | 51 | 21 |
| 200 | - | - | 44 | - | 52 | 0 |
| 400 | 71 | 45 | 33 | 36 | 50 | 0 |

Answer: SiO₂ and Si₃N₄ resist etching because neither is spontaneously fluorinated by HF in the absence of water, and the Si-F bond is too strong to undergo effective ligand exchange reactions that would generate volatile Si-containing products.

Answer: TiN cannot be etched due to either the absence of stable/volatile Ti(III) reaction products or the difficulty of fluorinating Ti(IV) surface species using HF.

Answer: Linear thickness decrease indicates constant etch per cycle (EPC), confirming reproducible self-limiting etching behavior.

Answer: Al₂O₃ and HfO₂ can be etched by both; ZrO₂ is etched by Sn(acac)₂ but only slightly by TMA.


Figure 6. Expansion of first two ALE cycles in Figure 5 showing the individual mass changes during the sequential TMA and HF exposures at 250, 275, 300, and  $325^{\circ}C$ .

Figure 6 shows the mass changes during the first two Al₂O₃ ALE cycles at 250, 275, 300, and 325 °C. The first TMA exposure produces mass gains of 27–32 ng/cm², corresponding to the reaction of surface AlOH* with TMA. The subsequent HF exposure adds 33–36 ng/cm² due to the conversion of AlCH₃* species to AlF* and formation of an AlF₃ surface layer. Mass changes are nearly constant across the temperatures during these early cycles, and higher temperatures lead to slightly larger gains. The figure highlights the initial nucleation behavior and the temperature-dependent early-stage mass changes.

| Time (s) | 250°C (ng/cm^2) | 275°C (ng/cm^2) | 300°C (ng/cm^2) | 325°C (ng/cm^2) |
|----------|-----------------|-----------------|-----------------|-----------------|
| 1        | ~25             | ~25             | ~25             | ~25             |
| 30       | ~65             | ~62             | ~60             | ~58             |
| 60       | ~68             | ~62             | ~64             | ~60             |
| 90       | ~60             | ~48             | ~40             | ~20             |
| 120     | ~70             | ~60             | ~58             | ~40             |

Answer: 2 cycles of sequential TMA and HF dosing.

Answer: The mass change increase until 60 s, and then it shows a decrease in its values.

Answer: 325 °C

Answer: Higher temperatures result in a greater removal of AlF3 from the surface and greater fluorination of Al2O3.

Answer: 325 degrees results in a net decrease of around 20 nm/cm^2.

Answer: No, it seems as if the initial cycle is not temperature depentent. For all temperatures similar mass changes are recorded.

Answer: If a linear relation is expected between etch rate and temperature, the final mass change level of 300 degrees celcius should be lower (equally spaced between the level of 275 and 325 degrees celcius).

Answer: It could be that there is net adsorption of TMA at the surface after which it starts etching as opposed to etching from the start.

Answer: It indicates that mass changes occur in discrete, repeatable steps within each cycle.

Answer: 325 °C shows the largest overall mass swing within one cycle.

Answer: HF removes fluorinated surface species formed during TMA exposure, leading to controlled material removal and mass loss.

Answer: At lower temperatures, the final mass after each cycle remains higher than at elevated temperatures. This indicates smaller net mass loss over the same number of cycles. Such differences are relevant when comparing cumulative removal across temperatures.

Answer: The first HF exposure converts AlCH₃* species to AlF* via AlCH₃* + HF → AlF* + CH₄, and fluorinates the underlying Al₂O₃ through Al₂O₃ + 6HF → 2AlF₃ + 3H₂O. This spontaneous reaction (ΔG ≈ −50 kcal) creates the AlF₃ surface layer that TMA can subsequently remove through ligand-exchange, enabling cyclic etching.

Answer: Mass loss begins during the second cycle at 275°C, 300°C, and 325°C, while 250°C requires a third cycle before etching onset.

Answer: The arrows mark the timing of sequential precursor exposures—blue arrows indicate TMA doses and red arrows indicate HF doses during the ALE cycles.

Answer: At higher temperatures, TMA removes a larger fraction of the AlF₃ surface layer through ligand-exchange reactions, producing more volatile AlF(CH₃)₂ products. The percentage of AlF₃ removed increases from 19% at 250°C to 74% at 325°C, explaining the pronounced mass loss at 325°C.

Answer: Etching occurs at ~65 seconds (TMA pulse).

Answer: No, the final mass is effectively higher (or barely changed) compared to the start of the cycle.

Answer: At 250°C (Red), the mass drop is negligible, implying the thermal energy is insufficient to drive the ligand-exchange reaction between TMA and the fluorinated surface. In contrast, at 325°C (Green), the massive drop indicates the barrier has been overcome, enabling rapid and efficient volatilization. This strong temperature dependence confirms the process is kinetically controlled by a significant energy barrier.

Answer: Ideally, an ALE step should be self-limiting, showing a sharp drop followed by a flat plateau (saturation). The slight continuous downward slope seen in the Green line (325°C) suggests a loss of self-limiting behavior, potentially due to thermal desorption of the film itself or a secondary CVD-like reaction. This instability makes precise depth control more difficult compared to the stable plateaus seen at intermediate temperatures (e.g., 300°C, Black line).

Answer: Yes

Answer:
1. The first TMA exposure displays mass gains of ΔMTMA = 27−32 ng/cm2 at 250−325 °C
2. The first HF exposure shows mass gains of ΔMHF = 33−36 ng/cm2 at 250−325 °C.

Answer: The fluorination reaction Al2O3 + 6HF → 2AlF3 + 3H2Ois spontaneous over the temperature range from 250 to 325 °C

Answer:
After the first HF exposure, the next TMA exposure removes the AlF3 layer on the Al2O3 substrate. Figure shows that mass losses during the TMA and HF cycles begin with the second TMA and HF cycle for temperatures from 275−325 °C. The
TMA and HF cycles at 250 °C show a mass loss after the third ALE cycle. The higher temperatures produce both a larger mass loss for the removal of AlF3 by TMA and a larger mass gain for the subsequent fluorination of Al2O3 by HF.

Answer: 250°C, 275°C, 300°C and 325°C.

Answer: After 60 seconds, which corresponds to the beginning of the second ALE cycle.

Answer: These mass gains result from the reaction of AlOH* surface species with TMA according to AlOH* + Al(CH3)3 → AlOAl(CH3)2* + CH4.

Answer: After the first ALE cycle, the mass loss during TMA exposure increases with temperature (roughly from 10 ng/cm^2 to 40 ng/cm^2), whereas the mass gain during HF exposure remains constant around 35-38 ng/cm^2.

Answer: 2 cycles.

Answer: The first TMA exposure causes a mass gain because TMA reacts with Al₂O₃ surface, leaving Al–CH₃–containing surface species. This methylation increases the measured mass. After HF converts the surface into an AlF₃-like fluorinated layer, TMA mainly acts as the etch step by reacting with that fluoride to form volatile AlF(CH₃)₂ that desorbs, producing the mass drop.

Answer: The TMA exposure half-cycle shows the strongest temperature dependence. This is indicated by the increasing magnitude of the mass drop during TMA as temperature rises, meaning TMA removes a larger fraction of the fluorinated surface at higher temperature. By comparison, the HF step’s mass gain changes much less across the same temperature range, consistent with it reaching a self-limited endpoint under the pulse conditions used.

Answer: 250°C

Answer: Increasing temperature reduces the net mass retained after each cycle. While all temperatures show stepwise increases during TMA exposure and decreases during HF exposure, the 325 °C trace exhibits significantly lower mass accumulation, indicating enhanced etching or reduced adsorption at higher temperature.

Answer: TMA exposures.

Answer: Yes

Answer: 250 °C ,275 °C ,300 °C , 325 °C

Answer: Yes. Higher temperatures lead to slightly larger mass gains during both TMA and HF exposures, reflecting more efficient surface reactions.

Answer: TMA exposure: AlOH reacting with Al(CH₃)₃ → formation of AlOAl(CH₃)₂, HF exposure: AlCH₃ reacting with HF → formation of AlF and AlF₃ surface layer

Answer: It helps determine the nucleation behavior, confirms self-limiting reactions, and allows estimation of the thickness of the AlF₃ surface layer, which is critical for precise etch depth control in ALE processes.

Answer: The first TMA exposure reacts with surface AlOH* species, resulting in a mass gain of 27–32 ng/cm² depending on the temperature. The subsequent HF exposure converts AlCH₃* species to AlF* and forms an AlF₃ surface layer, producing an additional mass gain of 33–36 ng/cm². These sequential reactions illustrate the self-limiting and surface-specific nature of the ALE process during the early cycles.

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


Figure 8. Temperature dependence of (a)  $\Delta M_{\mathrm{TMA}}$  and  $\Delta M_{\mathrm{HF}}$  and (b) MCPC for  $\mathrm{Al}_2\mathrm{O}_3$  ALE.

The multiple line chart shows how ΔM_TMA and ΔM_HF vary with temperature. As temperature increases, ΔM_TMA becomes more negative, indicating greater mass loss during TMA exposure, while ΔM_HF increases, indicating greater mass gain during HF exposure.

The line chart shows MCPC as a function of temperature. MCPC decreases steadily with increasing temperature, indicating a larger net mass loss per cycle at higher temperatures.

| Temperature (°C) | ΔM_TMA (ng/cm²·cycle) | ΔM_HF (ng/cm²·cycle) |
|------------------|------------------------|-----------------------|
| 250              | ~-15                   | ~5                    |
| 275              | ~-20                   | ~10                   |
| 300              | ~-30                   | ~15                   |
| 325              | ~-40                   | ~20                   |

| Temperature (°C) | MCPC (ng/cm²·cycle) |
|------------------|---------------------|
| 250              | ~-10                |
| 275              | ~-15                |
| 300              | ~-20                |
| 325              | ~-25                |

Answer: No

Answer: 250 °C

Answer: TMA

Answer: No, this is not given as at a certain point desorption can have a roll. Thereby eliminating the ALE mechanism.

Answer: For this MCPC 300 degrees celcius should be chosen as temperature.

Answer: It indicates a larger net mass loss per ALE cycle.

Answer: Since the etch rate per cycle (MCPC) changes significantly with temperature, small variations in temperature across a wafer would lead to different amounts of material being removed. Therefore, precise and uniform temperature control is essential to achieve uniform etching depths and consistent device performance across the entire substrate.

Answer: At 250°C, the MCPC is nearly zero, meaning the mass added by HF is almost exactly canceled by the mass removed by TMA, resulting in no net etch. The penalty is that the process effectively stops working as an etch; to remove any significant thickness, the cycle count would need to be prohibitively high, or the process would simply stagnate.

Answer: This implies the process is robust across this temperature range, with the opposing half-cycles compensating. A production tool can select a temperature based on throughput (higher T) or precision (lower T) without drastically altering the net etch depth per cycle, simplifying process window definition.

Answer: As ΔMTMA mass losses increase  at higher temperatures compared to ΔMHF and the MCPC also decreases with increase in temperature, it can be concluded that the temperature dependence of ΔMTMA observed in graph a dominates the temperature dependence observed in the MCPC shown in graph b

Answer:
The ΔMTMA/MCPC ratio for different temperatures are as follows

1.  250  °C, 2.55
2.  275 °C, 1.94
3.  300 °C, 1.83
4.  325 °C, 1.81

Answer: As the change in mass loss during TMA exposure is larger than the mass gain during HF exposure, the MCPC decreases with temperature.

Answer: The temperature dependence of the mass change during TMA exposure.

Answer: No

Answer: At  325 °C, the MCPC point is below zero, which means the net mass change per cycle is negative. That implies the process is etch-dominated at this temperature.  In other words, deposition during the HF half-cycle does not fully compensate the loss from the TMA half-cycle, so you get net etching.

Answer: 250 °C

Answer: Yes

Answer: Low temperature → higher MCPC, Mid temperature → moderate MCPC, High temperature → lowest MCPC

Answer: Higher temperature reduces surface reaction uptake and lowers mass change.

Answer: Yes

Answer: Mass loss increases progressively with temperature after TMA exposure.

Answer: The TMA dose seems to be more temperature dependent as the curve has a higher absolute slope.

Answer: The MCPC can be caluclated by adding both the delta M of TMA and HF, which gives an MCPC of -20 ng/cm^2.

Answer: ΔM_TMA and ΔM_HF change in opposite directions with increasing temperature. ΔM_TMA becomes more negative, indicating greater mass loss during the TMA step, while ΔM_HF becomes more positive, indicating greater mass gain during the HF step. Together, these opposing trends influence the net mass change per cycle.

Answer: 325 °C yields the largest ΔM_HF value.

Answer: 250°C: 0.14 Å/cycle; 275°C: 0.34 Å/cycle; 300°C: 0.51 Å/cycle; 325°C: 0.75 Å/cycle.

Answer: Higher temperatures enable TMA to remove a larger fraction of the AlF₃ surface layer during the ligand-exchange reaction. At 250°C, only ~19% of the AlF₃ layer is removed, while at 325°C, ~74% is removed. When more AlF₃ is removed, more fresh Al₂O₃ is exposed for fluorination in the subsequent HF step, leading to greater net material removal per cycle.

Answer: Greater AlF₃ removal by TMA exposes more Al₂O₃ surface, which allows more fluorination (and thus larger mass gain) during the subsequent HF exposure.

Answer: It allows the etch rate to be tuned by adjusting process temperature, providing flexibility for different application requirements.

Answer: HF acts as the surface modification agent, reacting with the oxide to form a solid fluoride layer (adding mass). TMA acts as the removal agent, reacting with that fluoride layer to form volatile species that leave the surface (removing mass). The cycle works because the mass removed by TMA is greater than the mass added by HF.

Answer: The increase in (ΔM(HF)  implies that at higher temperatures, fluorine penetrates deeper or saturates the surface more densely. This creates a larger reservoir of Al-F bonds available for the ligand-exchange reaction. Consequently, the TMA step consumes this thicker layer, resulting in a proportionally larger negative mass loss (ΔM(TMA)).

Answer: Yes. Followed same  reaction sequence of 2−30−1−30 on initial Al2O3 substrates.

Answer: ΔMTMA shows progressively larger mass losses at higher temperatures. In contrast, ΔMHF reveals progressively larger mass gains at higher temperatures.

Answer: As the temperature increases, the mass change during TMA exposure keeps decreasing linearly.

Answer: As temperature increases, the mass change during HF exposure keeps increasing linearly.

Answer: TMA half-cycle (|−40| > |+15|).

Answer: ΔM_TMA becomes increasingly negative with temperature, indicating greater mass loss during TMA exposure, while ΔM_HF increases, indicating greater mass gain during HF exposure. This suggests that both half-reactions become more pronounced at higher temperatures.

Answer: Temperature.

Answer: 250 °C, 275 °C, 300 °C, 325 °C

Answer: As the temperature increases, both ΔMTMA and ΔMHF drop steadily, which shows that each reaction step contributes less mass compared with lower temperatures. This trend suggests reduced reaction uptake at elevated temperatures, which is typical when surface adsorption becomes less favorable in ALE conditions.


FIG. 1. (Color online) (a) Crystalline  $\mathrm{SiO}_2$  sample used for the molecular dynamics investigation in this article. (b) The  $\mathrm{SiO}_2$  sample after 100 impacts of  $20\mathrm{eV}\mathrm{CF}_2^+$  ions. (c) The  $\mathrm{SiO}_2$  sample after 200 impacts of  $20\mathrm{eV}\mathrm{CF}_2^+$  ions. FIG. 3. Fluorine concentration in the sample as a function of sample height for different numbers of  $20\mathrm{eV}\mathrm{CF}_2^+$  ion impacts.

The line chart shows the fraction of fluorine (F) as a function of height (h) in angstroms (Å). The chart includes three lines representing different impact scenarios: 100 impacts, 200 impacts, and 400 CF2+ impacts

| Height h (Å) | 100 impacts (%) | 200 impacts (%) | 400 impacts (%) |
|---|---|---|---|
| 18 | 0 | 0 | 0 |
| 20 | 0 | 0.5 | 2 |
| 21 | 1 | 3 | 7 |
| 22 | 3 | 7 | 12 |
| 23 | 5 | 11 | 22 |
| 24 | 8 | 15 | 32 |
| 25 | 18 | 30 | 48 |
| 26 | 35 | 52 | 60 |
| 27 | 60 | 62 | 63 |
| 28 | 78 | 58 | 65 |
| 29 | - | 67 | 68 |

Answer: The F concentration increases and the profile broadens slightly as more ions impact the surface. However, the changes between 200 and 400 impacts are small, indicating the system approaches quasi-steady-state around 250 impacts. The passivation layer thickness remains approximately constant at ~8 Å.

Answer: Around h = 18–20 Å.

Answer: The fluorocarbon passivation process is self-limiting. As F accumulates at the surface, available bonding sites become saturated and incoming CF₂⁺ ions increasingly reflect or sputter existing material rather than adding new F. This leads to a dynamic equilibrium where deposition and removal balance.

Answer: About 8 Å.

icdar2026-competition-data/dev/atomic-layer-etching/simulation-usecase/1/A molecular dynamics investigation of fluorocarbon based SiO2.pdf


FIG. 10. Number of  $\mathrm{F}$  and  $\mathrm{C}$  atoms in the Si sample after bombardment with  $\mathrm{CF}_2^+$  ions. Results have been plotted for (a)  $10\mathrm{eV}$  and (b)  $20\mathrm{eV}$  ion energies.

The line chart shows the number of atoms (F and C) as a function of the number of CF₂⁺ ion impacts at 10 eV.

The line chart shows the number of atoms (F and C) as a function of the number of CF₂⁺ ion impacts at 20 eV.

| Number of CF2+ Ion Impacts | F (Number of Atoms) | C (Number of Atoms) |
|---|---|---|
| 0 | 0 | 0 |
| 50 | 15 | 6 |
| 100 | 30 | 12 |
| 150 | 42 | 20 |
| 200 | 48 | 24 |
| 250 | 62 | 31 |
| 300 | 73 | 32 |
| 350 | 72 | 32 |
| 400 | 78 | 34 |
| 450 | 83 | 36 |
| 500 | 85 | 37 |
| 600 | 85 | 36 |

| Number of CF2+ Ion Impacts | F (Number of Atoms) | C (Number of Atoms) |
|---|---|---|
| 0 | 0 | 0 |
| 50 | 25 | 8 |
| 100 | 45 | 10 |
| 150 | 56 | 12 |
| 200 | 63 | 11 |
| 250 | 68 | 11 |
| 300 | 62 | 9 |
| 350 | 72 | 10 |
| 400 | 80 | 10 |
| 450 | 80 | 8 |
| 500 | 78 | 8 |
| 550 | 70 | 6 |
| 600 | 71 | 5 |

Answer: At 10 eV, the film contains substantial carbon (C ~ 35–40 atoms at steady state) alongside fluorine. At 20 eV, carbon content drops to below 10 atoms while F remains around 75–80. This occurs because higher energy ions sputter C more efficiently, as F–Si bonds are stronger than C–Si bonds.

Answer: Around 450 CF₂⁺ ion impacts for both energies.

Answer: Because the F–Si bond is stronger than the C–Si bond.

Answer: 10 eV.


FIG. 11.  $\mathrm{F}$  density as a function of sample height in the Si sample with the fluorocarbon overlayer. Results have been plotted for  $100$ ,  $300$ , and  $600\mathrm{eV}$  ion impacts on the initial crystalline sample.  $\mathrm{CF}_2^+$  ion energies are (a)  $10$  and (b)  $30\mathrm{eV}$ .

F density versus height at 10 eV for 100, 300, and 600 CF₂⁺ impacts. The F layer is narrow (~5 Å) and remains at a fixed position, indicating minimal substrate disturbance.

F density at 30 eV. The profile is much broader, and the peak shifts to lower heights with increasing impacts, indicating that Si etching occurs simultaneously with passivation.

| Height h (Å) | 100 impacts (Atoms/Å³) | 300 impacts (Atoms/Å³) | 600 impacts (Atoms/Å³) |
|---|---|---|---|
| 38 | 0.000 | 0.000 | 0.001 |
| 39 | 0.000 | 0.001 | 0.005 |
| 40 | 0.000 | 0.005 | 0.015 |
| 41 | 0.001 | 0.018 | 0.030 |
| 42 | 0.008 | 0.035 | 0.048 |
| 43 | 0.020 | 0.055 | 0.060 |

| Height h (Å) | 100 impacts (Atoms/Å³) | 300 impacts (Atoms/Å³) | 600 impacts (Atoms/Å³) |
|---|---|---|---|
| 28 | 0.000 | 0.000 | 0.000 |
| 30 | 0.000 | 0.000 | 0.005 |
| 31 | 0.000 | 0.002 | 0.025 |
| 32 | 0.000 | 0.005 | 0.038 |
| 33 | 0.000 | 0.015 | 0.025 |
| 34 | 0.001 | 0.028 | 0.010 |
| 35 | 0.003 | 0.033 | 0.002 |
| 36 | 0.008 | 0.022 | 0.001 |
| 37 | 0.018 | 0.010 | 0.000 |
| 38 | 0.024 | 0.005 | 0.000 |
| 39 | 0.018 | 0.002 | 0.000 |
| 40 | 0.012 | 0.000 | 0.000 |
| 42 | 0.005 | 0.000 | 0.000 |
| 44 | 0.001 | 0.000 | 0.000 |

Answer: At 30 eV, the CF₂⁺ ions have enough energy to etch the underlying Si while depositing the fluorocarbon layer. As Si is removed, the surface recedes and the F-containing layer moves downward. At 10 eV, the ion energy is too low for significant etching, so the passivation layer remains at a fixed position.

Answer: The local atomic number density of fluorine at each height in the sample.

Answer: About 5 Å.

Answer: Below 30 eV, ideally around 10–20 eV.


FIG. 12. (a) Number of Si atoms that are sputtered from the Si sample with the fluorocarbon overlayer (10 eV  $\mathrm{CF}_2^+$ , 300 impacts) as  $\mathrm{Ar^{+}}$  ions of different energies are bombarded on it. (b) Fraction of initial F left in the sample as  $\mathrm{Ar^{+}}$  ions of different energies are bombarded on the Si sample with the fluorocarbon overlayer (10 eV  $\mathrm{CF}_2^+$ , 300 impacts).

Number of sputtered Si atoms versus Ar⁺ ion impacts at 20, 30, and 40 eV. At 20 eV, Si sputtering is self-limiting and virtually stops after ~500 impacts. At 40 eV, etching continues throughout.

Fraction of initial F removed from the sample versus Ar⁺ impacts. F is consumed faster at higher energies, correlating with enhanced Si etching.

| Ar+ Ion Impacts | 20 eV (Sputtered Si Atoms) | 30 eV (Sputtered Si Atoms) | 40 eV (Sputtered Si Atoms) |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 200 | 2 | 10 | 15 |
| 400 | 7 | 15 | 18 |
| 600 | 8 | 16 | 23 |
| 800 | 11 | 17 | 26 |
| 1000 | 11 | 19 | 28 |
| 1200 | 11 | 20 | 29 |
| 1400 | 12 | 21 | 30 |
| 1600 | 13 | 22 | 32 |
| 1800 | 13 | 22 | 33 |
| 2000 | 14 | 23 | 35 |

| Ar+ Ion Impacts | 20 eV (F Fraction Removed) | 30 eV (F Fraction Removed) | 40 eV (F Fraction Removed) |
|---|---|---|---|
| 0 | 0.00 | 0.00 | 0.00 |
| 200 | 0.05 | 0.28 | 0.30 |
| 400 | 0.20 | 0.33 | 0.37 |
| 600 | 0.24 | 0.38 | 0.43 |
| 800 | 0.24 | 0.44 | 0.48 |
| 1000 | 0.24 | 0.45 | 0.50 |
| 1200 | 0.27 | 0.47 | 0.50 |
| 1400 | 0.27 | 0.48 | 0.51 |
| 1600 | 0.30 | 0.48 | 0.51 |
| 1800 | 0.30 | 0.48 | 0.51 |
| 2000 | 0.30 | 0.48 | 0.51 |

Answer: At 20 eV, once the readily accessible surface F is consumed or reacted, the remaining F is either too deep in the substrate or bonded too strongly to participate in reactive ion etching. The Ar⁺ ions lack sufficient energy to access this buried F or to physically sputter Si without chemical assistance.

Answer: They are correlated: higher F removal corresponds to higher Si sputtering, since F enables reactive ion etching of Si.

Answer: At 20 eV, where Si sputtering virtually stops after the initial etching phase.

Answer: Below 30 eV.


FIG. 13. F density as a function of sample height in the Si sample with the fluorocarbon overlayer (10 eV  $\mathrm{CF}_2^+$ , 300 impacts). Results have been plotted for the initial sample and after 300 and  $600\mathrm{Ar^{+}}$  ion impacts.  $\mathrm{Ar^{+}}$  ion energies are (a) 20 and (b)  $40\mathrm{eV}$ .

| Height h (Å) | 0 impacts (Atoms/Å³) | 300 impacts (Atoms/Å³) | 1000 impacts (Atoms/Å³) |
|---|---|---|---|
| 25 | 0.000 | 0.000 | 0.001 |
| 28 | 0.000 | 0.000 | 0.005 |
| 30 | 0.000 | 0.000 | 0.012 |
| 32 | 0.000 | 0.002 | 0.015 |
| 34 | 0.000 | 0.005 | 0.015 |
| 36 | 0.005 | 0.015 | 0.018 |
| 38 | 0.045 | 0.028 | 0.022 |
| 39 | 0.058 | 0.030 | 0.025 |
| 40 | 0.025 | 0.015 | 0.010 |

| Height h (Å) | 0 impacts (Atoms/Å³) | 300 impacts (Atoms/Å³) | 1000 impacts (Atoms/Å³) |
|---|---|---|---|
| 20 | 0.000 | 0.000 | 0.000 |
| 25 | 0.000 | 0.002 | 0.002 |
| 28 | 0.000 | 0.008 | 0.004 |
| 30 | 0.000 | 0.010 | 0.006 |
| 33 | 0.000 | 0.003 | 0.004 |
| 36 | 0.005 | 0.005 | 0.002 |
| 39 | 0.058 | 0.008 | 0.001 |
| 41 | 0.005 | 0.002 | 0.000 |

Answer: At 40 eV, the CF₂⁺ ions have enough energy to etch the underlying Si while depositing the fluorocarbon layer. As Si is removed, the surface recedes and the F-containing layer moves downward. At 10 eV, the ion energy is too low for significant etching, so the passivation layer remains at a fixed position.

Answer: About 5 Å.

Answer: The local atomic number density of fluorine at each height in the sample.

Answer: Below 30 eV, ideally around 10–20 eV.


FIG. 2. F and C atoms in the  $\mathrm{SiO}_2$  sample as a function of the number of  $20\mathrm{eV}\mathrm{CF}_2^+$  ion impacts.

Number of F and C atoms in the SiO₂ sample versus CF₂⁺ ion impacts at 20 eV. F accumulates to ~100 atoms and saturates after ~250 impacts, while C remains low (~15 atoms), producing a strongly F-rich passivation layer.

| Number of CF2+ Ion Impacts | F (Number of Atoms) | C (Number of Atoms) |
|---|---|---|
| 0 | 0 | 0 |
| 25 | 18 | 5 |
| 50 | 32 | 8 |
| 75 | 42 | 10 |
| 100 | 52 | 11 |
| 125 | 62 | 12 |
| 150 | 72 | 13 |
| 175 | 85 | 13 |
| 200 | 88 | 15 |
| 225 | 90 | 16 |
| 250 | 98 | 15 |
| 275 | 102 | 15 |
| 300 | 98 | 14 |
| 350 | 96 | 12 |
| 400 | 94 | 10 |
| 450 | 105 | 11 |

Answer: Approximately 6–7 (F ~ 100, C ~ 15), indicating a strongly F-rich film.

Answer: At energies above 10 eV, carbon is sputtered more easily from the surface than fluorine because the F–Si bond is stronger than the C–Si bond. This preferential C removal results in a passivation layer enriched in fluorine.

Answer: About 250 CF₂⁺ ion impacts.

Answer: No, the composition has already saturated.


FIG. 4. (Color online) The  $\mathrm{SiO}_2$  sample after (a) 200 and (b) 400 impacts of  $20\mathrm{eV}\mathrm{CF}_3^+$  ions. FIG. 5. F and C atoms in the  $\mathrm{SiO}_2$  sample as a function of the number of  $20\mathrm{eV}\mathrm{CF}_3^+$  ion impacts.

Number of F and C atoms in the SiO₂ sample versus CF₃⁺ ion impacts at 20 eV. F reaches ~75 atoms at steady-state while C remains extremely low (~5 atoms). Compared to CF₂⁺, saturation takes longer (~400 impacts) and the film contains less of both species.

| Number of CF3+ Ion Impacts | F (Number of Atoms) | C (Number of Atoms) |
|---|---|---|
| 0 | 0 | 0 |
| 50 | 14 | 3 |
| 100 | 25 | 4 |
| 150 | 32 | 3 |
| 200 | 48 | 3 |
| 250 | 50 | 4 |
| 300 | 55 | 4 |
| 350 | 68 | 5 |
| 400 | 75 | 5 |
| 450 | 75 | 5 |
| 500 | 76 | 5 |
| 550 | 75 | 5 |
| 600 | 70 | 5 |

Answer: CF₃⁺ yields ~75 F atoms versus ~100 F atoms for CF₂⁺, resulting in a thinner passivation layer.

Answer: At 20 eV, a larger fraction of CF₃⁺ ions reflect from the surface without reacting. This occurs because CF₃⁺ has fewer carbon dangling bonds available for bonding, and the accumulating F at the surface terminates available sites, making the ions less reactive.

Answer: CF₃⁺ has only one C atom per three F atoms, and C is preferentially sputtered at 20 eV.

Answer: CF₂⁺.


FIG. 6. Effect of  $\mathrm{Ar^{+}}$  ion energy on the number of Si and O atoms sputtered from the  $\mathrm{SiO}_2$  sample with a fluorocarbon overlayer grown using  $\mathrm{CF}_3^+$  ions (400 impacts).

The chart shows the number of sputtered Si atoms as a function of the number of Ar⁺ ion impacts at different energies (50 eV, 40 eV, and 20 eV). The data points form step-like curves indicating cumulative counts.

The chart shows the number of sputtered O atoms as a function of the number of Ar⁺ ion impacts at different energies (50 eV, 40 eV, and 20 eV). The data points form step-like curves indicating cumulative counts

| Number of Ar+ Ion Impacts | 20 eV (Sputtered Si Atoms) | 40 eV (Sputtered Si Atoms) | 50 eV (Sputtered Si Atoms) |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 50 | 2 | 4 | 7 |
| 100 | 4 | 6 | 8 |
| 200 | 5 | 7 | 12 |
| 300 | 9 | 8 | 14 |
| 400 | 9 | 13 | 16 |
| 500 | 9 | 13 | 16 |
| 600 | 9 | 13 | 16 |
| 700 | 9 | 13 | 17 |
| 800 | 9 | 13 | 18 |

| Number of Ar+ Ion Impacts | 20 eV (Sputtered O Atoms) | 40 eV (Sputtered O Atoms) | 50 eV (Sputtered O Atoms) |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 100 | 2 | 15 | 25 |
| 200 | 5 | 30 | 45 |
| 300 | 8 | 42 | 60 |
| 400 | 10 | 62 | 70 |
| 500 | 11 | 63 | 78 |
| 600 | 12 | 65 | 85 |
| 700 | 13 | 72 | 100 |
| 800 | 14 | 73 | 115 |

Answer: In crystalline SiO₂, each Si atom is bonded to four O atoms (~16.8 eV total to liberate), while each O atom is bonded to only two Si atoms (~8.4 eV). This lower energy requirement allows O atoms to continue exiting the material even after Si sputtering has ceased.

Answer: The surface becomes oxygen-deficient due to preferential O sputtering.

Answer: At 50 eV, Si continues to etch even after F is depleted.

Answer: Yes, Si sputtering plateaus at 40 eV, indicating self-limiting behavior.


FIG. 7. Effect of  $\mathrm{Ar^{+}}$  ion impact on  $\mathrm{F}$  density in the  $\mathrm{SiO}_2$  sample with a fluorocarbon overlayer grown using  $\mathrm{CF}_3^+$  ions (400 impacts). Results have been plotted for (a)  $20\mathrm{eV}$  and (b)  $50\mathrm{eV}$ $\mathrm{Ar^{+}}$  ion energies.

The line chart shows the F density (Atoms/Å³) at different heights (Å) for an initial sample and after 200 and 400 Ar⁺ impacts at 20 eV.

The line chart shows the F density (Atoms/Å³) at different heights (Å) for an initial sample and after 200 and 400 Ar⁺ impacts at 50 eV

| Height h (Å) | Initial sample (Atoms/Å³) | 200 Ar+ Impacts (Atoms/Å³) | 400 Ar+ Impacts (Atoms/Å³) |
|---|---|---|---|
| 16 | 0.000 | 0.000 | 0.001 |
| 18 | 0.000 | 0.000 | 0.003 |
| 20 | 0.000 | 0.005 | 0.006 |
| 21 | 0.000 | 0.009 | 0.008 |
| 22 | 0.003 | 0.010 | 0.012 |
| 23 | 0.010 | 0.012 | 0.010 |
| 24 | 0.019 | 0.016 | 0.009 |
| 25 | 0.019 | 0.015 | 0.010 |
| 26 | 0.019 | 0.015 | 0.010 |
| 27 | 0.020 | 0.012 | 0.008 |
| 28 | 0.021 | 0.009 | 0.004 |

| Height h (Å) | Initial sample (Atoms/Å³) | 200 Ar+ Impacts (Atoms/Å³) | 400 Ar+ Impacts (Atoms/Å³) |
|---|---|---|---|
| 12 | 0.000 | 0.000 | 0.002 |
| 14 | 0.000 | 0.000 | 0.005 |
| 16 | 0.000 | 0.002 | 0.002 |
| 18 | 0.000 | 0.008 | 0.004 |
| 20 | 0.000 | 0.010 | 0.007 |
| 22 | 0.004 | 0.006 | 0.005 |
| 24 | 0.019 | 0.008 | 0.002 |
| 26 | 0.019 | 0.004 | 0.002 |
| 28 | 0.021 | 0.004 | 0.002 |

Answer: At 20 eV, F atoms are removed from the surface but the distribution remains narrow and localized. At 50 eV, higher energy ions push F atoms deeper into the SiO₂ bulk, causing the profile to broaden significantly. This buried F becomes less accessible for reactive ion etching.

Answer: About 15 Å (spanning from h ≈ 10 to h ≈ 25 Å).

Answer: Buried F becomes inaccessible to incoming Ar⁺ ions and cannot participate in reactive etching of Si.

Answer: 20 eV.


icdar2026-competition-data/dev/atomic-layer-etching/simulation-usecase/22/Review Paper -- Overview of atomic layer etching in the semiconductor industry.pdf


Figure 10. Change in the Gibbs free energy with temperature for various fluorination ALEt-half-reactions.

The chart shows the change in Gibbs free energy (ΔG) for various reactions (R2-R6) of different surface states with NbF5 at different temperatures. In these models, '0%-slab' denotes a bare Al2O3 surface, while '100%F-slab' and '100%Cl-slab' represent surfaces fully terminated with fluorine or chlorine atoms, respectively.

| temperature [°C] | R2: Al₂O₃ → AlF₃ + NbOF₃ | R3: 0%-slab → 100%F-slab + NbOF₃ | R4: 100%-slab → 166%-F-slab + NbOF₃ | R5: 100%-Cl-slab → 166%-F-slab + NbClF₄ + NbOF₃ | R6: 100%-Cl-slab → 100%-F-slab + NbClF₃ |
|---|---|---|---|---|---|
| 100 | -48 | -48 | -23 | -80 | -100 |
| 300 | -58 | -58 | -33 | -100 | -122 |
| 600 | -71 | -71 | -47 | -135 | -165 |

Answer: R6.

Answer: R4, R2,R3, R5, R6

Answer: All of them.

Answer: The fully chlorinated surface (100%-Cl-slab) is the most reactive (the most negative ΔG).

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


Figure 11. Change in the Gibbs free energy with temperature for possible chlorination or halide-exchange reactions.

The chart shows the change in Gibbs free energy (ΔG) for various reactions (R8-R14) of different surface states with CCl4 at different temperatures. In these models, '0%-slab' denotes a bare Al2O3 surface, while '100%F-slab' and '100%Cl-slab' represent surfaces fully terminated with fluorine or chlorine atoms, respectively.

| temperature [°C] | R8: Al₂O₃(s) → AlCl₃ + COCl₂ | R9: 0%·slab → 100%Cl-slab + COCl₂ | R10: 100%F-slab → 100%Cl-slab + CFCl₃ | R11: 100%F-slab → 66%Cl-slab + CFCl₃ + AlCl₃ | R12: 166%F-slab → 100%Cl-slab + CFCl₃ + AlCl₃ | R13: 100%F-slab → 0%·slab + CFCl₃ + AlCl₃ | R14: 166%F-slab → 0%·slab + CFCl₃ + AlCl₃ |
|---|---|---|---|---|---|---|---|
| 100 | -74 | -49 | 50 | 30 | 23 | -4 | -10 |
| 300 | -72 | -49 | 43 | 6 | -3 | -56 | -63 |
| 600 | -62| -40 | 26 | -31 | -43 | -136 | -143 |

Answer: R10.

Answer: Unmodified Al2O3 surface.

Answer: The over-fluorinated surface (166%F-slab).

Answer: No.


Figure 3.  $\mathrm{AlF}_x[\mathrm{O}]$  film thickness vs variation in total  $\mathrm{NbF}_5$  exposure time at 400 and  $460^{\circ}\mathrm{C}$ . The total  $\mathrm{NbF}_5$  exposure time is calculated by multiplying the  $\mathrm{NbF}_5$  pulse time by the total number of cycles. The  $\mathrm{NbF}_5$  pulse times of 4.5 and  $3\mathrm{~s~}$  were used at 400 and  $460^{\circ}\mathrm{C}$ , respectively. Each  $\mathrm{NbF}_5$  pulse was separated by a  $6\mathrm{~s~}$  long  $\mathrm{N}_2$  purge step.


Figure 5. Change in EPC with etch temperature for the  $\mathrm{NbF}_5$  and  $\mathrm{CCl_4}$  cyclic etching process and compared to no-etching by  $\mathrm{CCl_4}$  only. A total of 150 etch cycles were performed per data point. The EPC at etch temperatures below  $380^{\circ}\mathrm{C}$  stayed zero for both curves.

The chart shows the relationship between etch temperature and etch per cycle for two different sequences: NbF5 +  CCl4 (3/6/3/6s) and CCl4 (3/6s). CCl4 alone produces no etching.

| etch temperature [°C] | NbF5 +  CCl4 (3/6/3/6s): etch per cycle [A/Cycle] |CCl4 (3/6s): etch per cycle [A/Cycle] |
|---|---|---|
| 380 | 0.03 | -0.07 |
| 400 | 0.225 | -0.06 |
| 460 | 1.45 | -0.06 |

Answer: No. An ALE window would look like a plateau, where the EPC remains roughly constant across wide range of temperatures. Here, the EPC rises continiously.

Answer: CCl4 sequence (9 seconds vs. 18 seconds in NbF5/CCl4 sequence).

Answer: Wihtout NbF5 step, no etching occurs.

Answer: Highly sensitive (EPC jumps from 0.2 Å/Cycle at 400 °C to 1.45 Å/Cycle at 460 °C)


Figure 7. XPS depth profile of  $\mathrm{Al}_2\mathrm{O}_3$  exposed to  $\mathrm{NbF}_5$  for a total of 450 s at  $460^{\circ}\mathrm{C}$ . The atomic percentage of elements found in the converted film is plotted with respect to the sputter time.

The chart shows the XPS depth profile of various species (C 1s, O 1s, F 1s, Al 2p, Nb 3d), shown as at.% against sputter time. It reveals a high surface fluorine concentration that gradually decreases with sputter time, while the oxygen signal significantly increases deep into the film. The  aluminum content rises slightly and niobium remains low.

| sputter time [min] | atomic % | Species |
|---|---|---|
| 0,00 | 49,27 | F1s |
| 0,26 | 56,54 | F1s |
| 0,51 | 53,77 | F1s |
| 1,02 | 46,38 | F1s |
| 1,53 | 36,81 | F1s |
| 2,00 | 26,08 | F1s |
| 2,78 | 12,69 | F1s |
| 3,51 | 5,88 | F1s |
| 4,26 | 2,88 | F1s |
| 5,00 | 1,96 | F1s |
| 0,02 | 14,65 | O1s |
| 0,26 | 16,85 | O1s |
| 0,52 | 19,96 | O1s |
| 1,01 | 25,96 | O1s |
| 1,50 | 34,15 | O1s |
| 2,00 | 44,08 | O1s |
| 2,75 | 54,46 | O1s |
| 3,49 | 59,77 | O1s |
| 4,26 | 62,08 | O1s |
| 4,99 | 61,50 | O1s |
| 0,02 | 19,62 | Al2p |
| 0,27 | 23,42 | Al2p |
| 0,52 | 24,35 | Al2p |
| 1,01 | 25,85 | Al2p |
| 1,53 | 27,58 | Al2p |
| 2,01 | 29,65 | Al2p |
| 2,79 | 31,96 | Al2p |
| 3,52 | 33,69 | Al2p |
| 4,26 | 33,81 | Al2p |
| 4,99 | 32,31 | Al2p |
| 0,02 | 14,77 | C1s |
| 0,25 | 2,19 | C1s |
| 0,51 | 1,62 | C1s |
| 1,01 | 1,50 | C1s |
| 1,51 | 0,92 | C1s |
| 2,01 | 0,12 | C1s |
| 2,75 | 0,46 | C1s |
| 3,49 | 0,23 | C1s |
| 4,23 | 0,23 | C1s |
| 5,02 | 0,12 | C1s |
| 0,01 | 1,38 | Nb 3d |
| 0,27 | 1,15 | Nb 3d |
| 0,51 | 0,92 | Nb 3d |
| 1,01 | 0,69 | Nb 3d |
| 1,51 | 0,92 | Nb 3d |
| 2,00 | 0,69 | Nb 3d |
| 2,75 | 0,58 | Nb 3d |
| 3,52 | 0,46 | Nb 3d |
| 4,28 | 0,12 | Nb 3d |
| 4,99 | 0,12 | Nb 3d |

Answer: Fluorine

Answer: Oxygen.

Answer: In the bulk.

Answer: The fluorination extends significantly deep into the film. Even after 3-4 minutes of sputtering, F signal is still detectable. Since sputtering removes material over time, the persisiting signal indicates that the fluorination happens not only on the surface.


Figure 8. XPS depth profile of the remaining  $\mathrm{Al}_2\mathrm{O}_3$  after removing about  $18\mathrm{nm}$  film by the  $\mathrm{NbF}_5$  and  $\mathrm{CCl}_4$  ALEt process. A zoomed picture at the top right corner focuses on Nb, F, and Cl signals.

A chart showing the XPS elemental depth profile (at.% agains sputter time) of C, O, Al, Nb and Cl on the Al2O3 surface after approx. 18 nm were removed.

| sputter time [min] | atomic % | species |
|---|---|---|
| 0.0 | 26.4 | C1s |
| 0.3 | 0.4 | C1s |
| 0.5 | 0.2 | C1s |
| 1.0 | 0.0 | C1s |
| 1.5 | 0.4 | C1s |
| 2.0 | 0.0 | C1s |
| 2.8 | 0.2 | C1s |
| 0.0 | 26.4 | F1s |
| 0.2 | 1.4 | F1s |
| 0.5 | 0.2 | F1s |
| 1.0 | 0.5 | F1s |
| 1.5 | 0.4 | F1s |
| 2.0 | 0.5 | F1s |
| 2.8 | 0.2 | F1s |
| 0.0 | 26.4 | Nb 3d |
| 0.3 | 0.3 | Nb 3d |
| 0.5 | 0.2 | Nb 3d |
| 1.0 | 0.5 | Nb 3d |
| 1.5 | 0.4 | Nb 3d |
| 2.0 | 0.5 | Nb 3d |
| 2.8 | 0.2 | Nb 3d |
| 0.0 | 24.6 | Al 2p |
| 0.2 | 34.6 | Al 2p |
| 0.5 | 34.9 | Al 2p |
| 1.0 | 35.0 | Al 2p |
| 1.5 | 35.4 | Al 2p |
| 2.0 | 35.2 | Al 2p |
| 2.4 | 35.2 | Al 2p |
| 2.7 | 35.1 | Al 2p |
| 0.0 | 41.9 | O1s |
| 0.2 | 63.6 | O1s |
| 0.5 | 64.1 | O1s |
| 1.0 | 64.8 | O1s |
| 1.5 | 64.8 | O1s |
| 2.0 | 64.3 | O1s |
| 2.8 | 64.7 | O1s |
| 0.0 | 0.0 | Cl 2p |
| 0.3 | 0.0 | Cl 2p |
| 0.5 | 0.3 | Cl 2p |
| 1.0 | 0.0 | Cl 2p |
| 1.5 | 0.0 | Cl 2p |
| 2.0 | 0.0 | Cl 2p |
| 2.8 | 0.0 | Cl 2p |

Answer: No, the etching process leaves minimal precursor contamination on the remaining surface. The XPS depth profile demonstrates that residues of Niobium and Chlorine are negligible. It is indicating that the volatile  reaction products or unreacted precursors were successfully removed.

Answer: Oxygen

Answer: Oxygen

Answer: The removal is not compelte, a thin residual fluorinated layer persists on the surface.