Jose:

If you want very smooth surface without oxide you might try to have the
wafers CMP to remove oxide. After CMP a short HF dip might be necessary but
the results should be a very smooth surface for your device. Bob Henderson

----- Original Message -----
From: 
To: 
Sent: Thursday, February 26, 2009 2:41 AM
Subject: [mems-talk] The curious incident of the SOI wafer


> Dear all,
>
> I wrote some months ago because I had problems with etching a SOI
> wafer. I tried your suggestions but unfortunately did not get good
> results, but finally I found the problem: our SOI wafer has 700 nm of
> unexpected oxide on the top!
>
> Have any of you ever heard about something like this?
> Does anybody know a RELIABLE SOI wafer supplier where I could buy
> wafers in small quantities with a device layer of silicon in the range
> of 300-400 nm?
>
> I etched the top with 3% HF, but the surface remains too rough for my
> device. Now, I think the best solution is to buy a new wafer, but if
> somebody knows of a better etch chemistry to remove the oxide
> and get the silicon layer with optical quality it would be also
> appreciated.
>
> Thanks in advance!
> Jose