Specific Process Knowledge/Etch/Wet Silicon Nitride Etch
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Wet Silicon Nitride Etch
Wet Etching of silicon nitride - stoichiometric and Si-rich - is done in a dedicated wetbench with an integrated quartz tank. The quartz tank can take up to 25 6" wafer carrier. The wetbench is placed in cleanroom D-3. The process is mainly used to strip silicon nitride (maskless), but can also be used for masked etching of silicon nitride using some kind of silicon oxide as etch mask. However, the wet silicon nitride etch is isotropic - meaning that the under-etching (etch-bias) at least amounts to the thickness of the silicon nitride layer.
The etch solution is initially 85 wt% H3PO4 which is heated up to the boiling temperature - ca. 160°C the selectivity RSi3N4 / RSiO2.
NB: Great care has to be taken in this process due to risk of "shock-boiling" Therefore it is essential, that you stir thorough during heat up, before you start heating, at 50°C and last time at 100°C
The user manual, user APV and contact information can be found in LabManager:
Nitride etch info page in LabManager,
Wet Silicon Nitride Etch
| Nitride Etch @ 160 oC | |
|---|---|
| Generel description | Etch/strip of silicon nitride |
| Link to safety APV and KBA | see APV here |
| Chemical solution | H3PO4 (85 wt%) |
| Process temperature | 160 oC |
| Possible masking materials |
|
| Etch rate |
|
| Selectivity RSi3N4 / RSiO2 | The selectivity (sirich nitride:oxide) is higher at 160 oC than at 180 oC |
| Batch size |
1-25 wafer at a time |
| Size of substrate |
2-6" wafers |
| Allowed materials |
|