kirt,
     If you have poor surface the HF will attack this surface more than BOE.
If you prime the surface correctly vacuum vapor prime neither will attack the
interface.  Contact me for details of thick oxide etches with wafers that have
been deliberately left prior to resist coat for times up to 7 days.  Bill
Moffat

-----Original Message-----
From: kirt_williams@agilent.com [mailto:kirt_williams@agilent.com]
Sent: Thursday, May 30, 2002 5:22 PM
To: mems-talk@memsnet.org
Subject: RE: [mems-talk] HF and photoresist mask


> I want to mask HF etching with photoresist. Just now,
> somebody suggest me that
> for the same thickness of oxide I will etch. The photoresist
> could stand
> buffered HF, but for concentrated HF, it will not. Is it
> exactly the case?
> Could I be able to find some reference?

Stronger HF solutions tend to peel the photoresist off,
rather than etching it (indeed, I have sometimes measured an increase
in photoresist thickness after HF-base etches due to absorption).

Concentrated HF (49% by weight) that has been diluted more than about 3:1 by
volume
by H2O or NH4F (40% by weight), to make for example 10:1 HF or 5:1 BHF,
can be used with photoresist for at least a few minutes.

        --Kirt Williams Agilent Technologies
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