Do a 1-minute etch in a moderately fast isotropic silicon etchant.
If you don't have one already made up, use the one described in
http://microlab.berkeley.edu/labmanual/chap1/JMEMSEtchRates2(2003).pdf
This will smooth out notches in the sidewalls somewhat.
For the DRIE parts I did this to, I got about 2X as much motion motion
before fracture.
    --Kirt Williams

----- Original Message -----
From: "Qing Yao" 
To: "MEMS-talk" 
Sent: Thursday, May 27, 2004 9:04 AM
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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