Specific Process Knowledge/Thin film deposition/ALD2 (PEALD)/HfO2 deposition using ALD2
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HfO2 can be deposit by ALD using both thermal and plasma methods. The typical deposition temperature lies within 150-350 °, although using plasma the temperature can be lowered down to 100 ° without significant sacrifice of uniformity. It is worth mention that a unique feature of Picosun R-200 Advanced Plasma ALD tool, so-called - Picoflow Diffusion Enhancer, is used in the plasma process.
HfO2 deposition using TEMAHf and H2O precursors
(Results from the acceptance test)
The test was done with 400 cycles at 250 °C where the growth rate was measured to be 0.0804 nm/cycle.
| TEMAHf | H2O | |
|---|---|---|
| Nitrogen flow | 200 sccm | 150 sccm |
| Pulse time | 1.5 s | 0.1 s |
| Purge time | 6.0 s | 6.0 s |
Ellipsometry measurement
Uniformity profile across 150 mm Si wafer based on 49 measurement points measured with ellipsometer. The values for the grown oxide thickness can be seen in the table below.
| Parameter | Average | Min. | Max. | Std.Dev | %Range |
|---|---|---|---|---|---|
| Thickness (nm) | 32.16 | 31.28 | 33.29 | 0.49 | 6.2486 |
AFM measurement
The AFM measured roughness was 2.09nm. The high roughness value occurred due to formation of clustered Hf2 which are also visible in the SEM as shown in the figure below.
SEM measurement
Pernille Voss Larsen, Mikkel Dysseholm Mar and Tanja Amport, DTU Danchip, 2016-2017.
HfO2 deposition on trenches using TEMAHf and H2O precursors
(Results from the acceptance test)
The test was done with 400 cycles at 250 °C where the growth rate was measured to be between 0.954-1.22 nm/cycle depending on the depth.
| TEMAHf | H2O | |
|---|---|---|
| Nitrogen flow | 200 sccm | 200 sccm |
| Pulse time | 1.5 s | 10 s |
| Purge time | 20.0 s | 20.0 s |
SEM measurement
The SEM images below show that a higher coverage occurred at the top compared to the bottom. The difference is roughly around 10 nm.
Pernille Voss Larsen, Mikkel Dysseholm Mar and Tanja Amport, DTU Danchip, 2016-2017.
HfO2 deposition using O2 plasma
Recipe name: HfO2 O2 plasma
Temperature window: 100 °C - 350 °C
The deposition rate is measure to be 0.106 nm/cycle and 0.119 nm/cycle for 300 °C and 100 °C respectively.
| TEMAHf | O2 | |
|---|---|---|
| Nitrogen flow | 200 sccm | 150 sccm |
| Pulse time | 0.5 s | 30 s |
| Purge time | 10.0 s | 20.0 s |
Note! If deposition time is critical, the reduction of O2 plasma pulse time from 30 s to 10 s (and corresponding "RF power on" from 28 to 8 s) do not significantly impact the uniformity, also the purge step after O2 pulse can be reduced down to 10s.
PicoflowTM Diffusion Enhancer
PicoflowTM Diffusion Enhancer is optional feature and provides stop flow functionality for lengthening the time available for precursor diffusion and surface reactions on substrates without risk of back-diffusion into source lines of the reaction chamber. The RECIPE 5 page depicts programmable parameters used for controllingthe stop flow functionalities.
- The fifth recipe page of the user interface.
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To enable or disable the stop flow functionality, set the control for V6 valve to Enable/Disable.
For each source line, the selection Enable/Disable controls stop flow usage for the selected source lines.
Source Flow box marked with "sccm" sets the mass flow rate used in the source line at low flow state. The typical value is 40 sccm.
Note. Set the same source flow for every line, even if the source line is disabled for the low flow state.
The value in the box between Low Flow and V6 close
t1
) sets the time from Low flow start to V6 close. The purpose of this delay is to ensure the pressure drop of the reaction chamber before the V6 valve close. Typical value is 1.5 s.
The value in the box between V6 close and Precursor pulse sets the time from V6 close to Precursor pulse. The purpose of this delay is to ensure the V6 valve close before precursor pulse activation. Typical value is 1.3 s
The value in the box between Precursor pulse and V6 open defines how long the mass flow rates of nitrogen gas through the source lines are kept at low value.
The value in the box between V6 open and Normal flow defines how long low flow rate is kept low after opening of V6. Typical value is between 0.0 s and 1.0 s.
Note: The pulse + purge time for the enabled stop flow source line must be longer than the combined stop flow delays set in the stop flow page. For example, if the pulse + purge time is 1.0s + 6.0s = 7.0, then the sum of the four delay times must be less than 7.0s.
- The typical source line pressure curve with Picoflow.
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