Specific Process Knowledge/Etch/Wet Polysilicon Etch
Wet Poly Etch
The wet Poly Etch is an isotropic silicon etch. This holds for both a poly-silicon thin-film as well as single-crystalline material such as a Si(100) surface. The Poly Etch process is placed in a dedicated PP-tank in a laminar-flow bench in cleanroom 4.
The Poly Etch is typically used for opening holes in poly-silicon thin-films, using photoresist as an etch mask. Due to its isotropic nature the under-etching (etch-bias) at least amounts to the thickness of the poly-silicon layer. Another example of usage is etching of "circular-shaped" holes in silicon substrates.
The Poly Etch is based on the combined oxidation of silicon followed by dissolution of the silicon oxide. The etch solution consists of:
HNO3 : BHF : H2O - (20 : 1 : 20)
NB: The life time of the solution is only a few days.
Poly Etch data
| Poly Etch @ room temperature | |
|---|---|
| General description |
Etch of poly-si/Si(100) |
| Chemical solution | HNO3 : BHF : H2O (20 : 1 : 20) |
| Process temperature | Room temperature |
| Possible masking materials: |
|
| Etch rate |
|
| Batch size |
1-25 wafers at a time |
| Size of substrate |
2-4" wafers |