Specific Process Knowledge/Thin film deposition/ALD2 (PEALD)/AlN deposition using ALD2
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General Information
The AlN process should never run above 350 °C due to the decomposition of the trimethylaluminium. As already mentioned in the general ALD2 (PEALD) page oxides and nitrides cannot be deposited at the same time. Since the aluminium nitride requires the plasma source we only run all nitride processes without the thermal lid. Hence the chamber volume is bigger than with the thermal lid which causes that the substrate temperature is around 50 °C lower than the setpoint.
Result from acceptance test
Deposition of AlN using TMA and NH3 plasma
Recipe name: AlN NH3 plasma
Temperature window: 250 °C - 350 °C
The deposition rate is measure to be 0.137 nm/cycle for 350 °C with growth delay of 144 cycles.
| TMA | NH3 | |
|---|---|---|
| Nitrogen flow | 100 sccm | 150 sccm |
| Pulse time | 0.1 s | 5 s |
| Purge time | 8 s | 30 s |
| Plasma source settings | ||||
|---|---|---|---|---|
| RF power (W) | Ar carrier flow (sccm) | Plasma gas flow (sccm) | t1 stabilization (s) | t2 RF Power on (s) |
| 3000 | 150 | 100 | 1 | 3.4 |
Note! Remember to obey the relation: [Pulse time - (t1+t2)] > 0.5 s
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Deposition function for AlN with NH3 plasma (350 °C)
Evgeniy Shkondin, DTU Nanolab, 2020.
Spectroscopic ellipsometry
Refractive index and permittivity
Thickness distribution and uniformity
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Thickness distribution across the 100 mm wafer (350C 500cycles) -
Thickness distribution across the 100 mm wafer (350C 568cycles) -
Thickness distribution across the 100 mm wafer (350C 852cycles) -
Thickness distribution across the 100 mm wafer (350C 1136cycles) -
Thickness distribution across the 100 mm wafer (350C 1704cycles) -
Thickness distribution across the 100 mm wafer (350C 2272cycles)
| Ellipsometry results for AlN deposited with TMA and NH3 plasma | ||||||
|---|---|---|---|---|---|---|
| Number of cycles | Temperature (°C) | Average thicknes (nm) | Minimum thickness (nm) | Maximum thickness (nm) | Standard deviation | Procent deviation (%) |
| 500 | 350 | 42.9565 | 41.7422 | 43.4888 | 0.42652 | 2.0331 |
| 568 | 350 | 66.1824 | 64.2685 | 67.4074 | 0.7256 | 2.3714 |
| 852 | 350 | 103.8306 | 100.8147 | 106.1143 | 1.2407 | 2.552 |
| 1136 | 350 | 128.1302 | 124.8565 | 131.037 | 1.444 | 2.4118 |
| 1704 | 350 | 203.6618 | 198.1933 | 210.8584 | 2.7121 | 3.1094 |
| 2272 | 350 | 298.1225 | 293.8553 | 305.0185 | 2.3923 | 1.8723 |
Evgeniy Shkondin, DTU Nanolab, 2020.