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
Poly Etch data
Nitride etch @ 180 oC | Nitride etch @ 160 oC | |
---|---|---|
General description |
Etch/strip of silicon nitride |
Etch/strip of silicon nitride |
Chemical solution | H3PO4 (85 wt%) | H3PO4 (85 wt%) |
Process temperature | 180 oC | 160 oC |
Possible masking materials: |
|
|
Etch rate |
|
|
Batch size |
1-25 wafers at a time |
1-25 wafer at a time |
Size of substrate |
2-6" wafers |
2-6" wafers |