[mems-talk] Pyramid etch by NaOH

[Dave Goldstein]

Hi, All,  I need to obtain a uniform layer of random pyramids on the (100)
mirror-polished Si surface. I have been trying the NaOH (1-3%) + Ethyl
Glycol(0.6%) + Isopropanol (5-10%) at 78 C. Here is my questions:

1. I have already HF the sample just before the etch, so that it is
hydrophobic. But I found out that more often than not, it does not etch. Or
it just etches part of the sample. My samples ranges from 2x2cm to 5x5cm.

2. I have found out that if I RCA clean the sample before the NaOH etch, it
is harder to etch the sample.

3. If I use some diamond paste (for polishing) with grit size ranging from 3
- 9 um to rub the sample surface, the etch begins right away.

Anybody with experience in texture etching the (100) silicon surface with
NaOH? Thanks!

Dave