You can etch Pyrex in 6:1 BOE (Buffered Oxide Etch) at the rate of 2-3
microns/hr.  I have found photoresist to have rather poor adhesion to Pyrex.
Therefore I typically deposit chrome as an adhesion layer, process the
resist, wet etch the chrome, then etch the Pyrex.

Even with the chrome adhesion layer, the undercut when wet etching the Pyrex
is rather severe; ~20 microns undercut for a 5 micron etch depth.  I prefer
to use SF6 RIE for the Pyrex, which tends to be anisotropic, with very
little undercut.  In this case the chrome will serve as an etch mask, as the
Pyrex tends to etch slower than the resist.

Roger Shile

----- Original Message -----
From: "Tom Fan" 
To: 
Sent: Friday, July 18, 2003 1:39 AM
Subject: [mems-talk] Pyrex Etch


>
>
> I've dug through the MEMS-talk archives trying to find out some info on
wet
> etching of Pyrex. Most of the posts address to deep glass etching and most
> people use Cr/Au as etching masks. I want to do a shallow etch (4 um)
instead.
> Would photoresist be able to stand HF for such a shallow etch or Cr/Au
still
> need to be used? I also learned from the past discussion that photoresist
does
> not adhere well to Pyrex wafers. Is this true? This is the reason that Cr
is
> deposited before the photoresist, but what is the role of Au then?
>
> Thanks,
> Tom Fan
>
>
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