Questions about the Si wet etching process in SOI wafer
jimkruger at yahoo.com
Fri Jul 8 12:20:59 PDT 2011
TMAH is very selective to the thin native SiO2 on all Si, much more than KOH. I am guessing that your SOI had a little more SiO2 than your test wafer.
Use a 50:1 HF dip for 30 or 60 sec (60 sec =~ 50A) just before the TMAH, rinse but no need to dry, just into the TMAH. I don't think the doping plays much roll until very high levels of Boron.
--- On Fri, 7/8/11, Donkoun Lee <dlee76 at stanford.edu> wrote:
From: Donkoun Lee <dlee76 at stanford.edu>
Subject: Questions about the Si wet etching process in SOI wafer
To: wbgen-hpr at snf.stanford.edu
Date: Friday, July 8, 2011, 11:12 AM
Recently, I used the 25% TMAH in order to wet-etch the Si layer in SOI wafer.
Before etching a SOI wafer, when I used a Si wafer for the reference, the Si wafer was well etched.
However, when I used the SOI wafer, the Si layer (device layer) in SOI wafer was not etched at all:
The condition I used is like below:
Temperature: 45 oC
Concentration of TMAH: 25%
The Si thickness in SOI wafer: 30 ~ 50 nm
I also used the higher temperature, like ~ 70 oC. But, I could not etch the Si layer in SOI wafer.
Si layer is P-type. However, the doping concentration is around 10^15/cm2.
Furthermore, I double checked out the orientation of the Si layer and the orientation was (001)
Could you give me a tip for solving this problem?
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