Try dry thermal oxidation, but be aware that it consumes some of the
silicon.
See: Juan W H and Pang S W 1998 "Controlling sidewall smoothness for
micromachined Si mirrors and lenses" J. Vac. Sci. Technol. B 1480-4

Ariel



----- Original Message -----
From: "Qing Yao" 
To: "MEMS-talk" 
Sent: Thursday, May 27, 2004 5:04 PM
Subject: [mems-talk] Si surface roughness in DRIE process


> Hi,
>
>
> I ran BOSCH process on a ICP-DRIE system to make some high-aspect-ratio
> structure by etching through a 400 micron thick single crystal Si (110)
> wafer. The structure turned out to be very brittle and can't withstand
> perturbation in horizontal directions. I checked the sidewalls and found
> they are pretty rough and there are many straw-like features in vertical
> directions (from the top to bottom). I think they result in serious stress
> concentration and cause this problem.
>
> I was wondering if there are some methods or post-process which could make
> the sidewalls smoother. Please let me know if you have some suggestions or
> comments. Thanks!
>
>
>
> Best Regards,
>
>
> Qing Yao
> ___________________
> M&IE @ UIUC
>
>
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