Henry,
      In my experience the priming between the oxide and the resist was the
total secret.  If you allowed moisture to remain on the surface the resist
bond was poor at that point and either BOE or straight HF gave poor adhesion.
More so in the case of the straight HF.  If you use Vacuum Vapor Prime you
dehydrate in a vacuum and while in the vacuum prime with HMDS creating a
Hydrophobic surface that repels moisture for weeks.  One example I personally
tested at AMD was 17,000 angstroms of SiO2, treated with H2O2/H2SO4 to emulate
a rework and create a wet surface.  35 wafers were then vacuum vapor primed
and every 24 hours 5 more wafers were coated with resist.  Then all 35 wafers
were exposed, developed, baked and etched in BOE for approx 17 minutes.  The 7
day old wafers had no problems at etch.  Bill Moffat

-----Original Message-----
From: Henry Yang [mailto:[email protected]]
Sent: Thursday, May 30, 2002 3:09 PM
To: [email protected]
Subject: Re: [mems-talk] HF and photoresist mask


Hi Jing,

I had exprimented with PR (SJR 5740 from Shipley) in both concentrated HF
and BOE. In 49% HF bubbles form from underneath the resist and peel the
resist off. I do not know how the 49% HF penetrate the PR, but some
reaction does take place between the PR and oxide interface. In BOE,
however, the PR held up rather well. Of course it is dependent upon your
process condition of the PR. If you hardbake the PR for longer, it is
usually more resistant to HF.

Good luck!

Henry

--------------------------------------------------------------
Henry Yang
Mechanics and Micromechanics Group
IBM Almaden Research Center
408-927-2319



                      Jing Liu
                                          cc:
                      Sent by:                 Subject:  [mems-talk] HF and
photoresist mask
                      mems-talk-admin@m
                      emsnet.org


                      05/30/2002 12:34
                      PM
                      Please respond to
                      mems-talk





To who may concern,

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?

BTW, we have Shipley 1813, AZ 5214, Az 9245 in the lab. Does anyone have
some
date of how fast they will etched in HF?

Thanks,

Jing
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