Hi Shweta,

your question is a little bit confusing to me. HF doesn't etch Si at all.
And I can just hardly imagine that you oxidize your Si-Wafer with an 80k
Angstrom thick oxide. I etched 5k Angstrom thick oxide in HF (approximately
6-7 minutes) and this is no problem with S1813. Why don't you just pattern
your SiO2 and etch the trenches into Si with TMAH for about 4 minutes?

Andreas Jahn
Office: (301)975 4710

-----Original Message-----
From: R. Brent Garber [mailto:[email protected]]
Sent: Monday, March 17, 2003 9:49 AM
To: [email protected]; General MEMS discussion
Subject: Re: [mems-talk] HF attack of PR Shipley 1813


I don't know what is on you Si, but I dry etch Si in SF6 @ 5mT in a RIE at
70 watts with a 4min/um rate.  Resist will never withstand a 4um etch in my
experience and wet etching that deep will not be easy.

Brent

Shweta Humad wrote:

> Hi all,
> I was thinking of a process which would involve a last step of HF wet
> etching to create 4 micron deep trenches in silicon. I'm not sure how
> long the photo resist can withstand the HF. The photo resist would be
> Shipley 1813. I could use BOE also instead of HF but that would take
> even longer. Has anyone does this before?
>
> Thank you
> --
> Shweta Humad
> Office: (404) 385-4306/2400
>
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