Hi,

Thanks for your reply, I do have a dehydration bake step before spinning
HMDS. The bake temp was 150c (oven) for 5min. Also, i allow the sample to
cool after i bake (leave it for couple of min).

if you have any suggestions please let me know.

regards

bala




----- Original Message -----
From: "Bill Moffat" 
To: 
Sent: Wednesday, July 03, 2002 11:10 AM
Subject: RE: [mems-talk] Problems with liftoff(on quartz)


> Balaji,
>        The problem is that you are wetting the quartz and the HMDS reacts
with
> the hydrogen in the moisture on the quartz surface.  Partial cure is a
very
> good dehydration bake and a very fast move to spin on HMDS.  At a previous
> company I had a problem layer with 17,000 angstroms of thermal Silicon
Dioxide
> with a 15 minute BOE.  If we waited over 4 hours for the HMDS spin the
resist
> lifted off.  The total cure is vacuum vapor prime, when we put this in we
did
> the following test.  35 wafers with thermal silicon dioxide, ran through
> H2SO4/H2O2 to emulate a rework and get the wafers moist.  Then we vacuum
vapor
> primed all 35 wafers and left them in a work station exposed to room air.
> Every 24 hours we coated 5 wafers and at the end of 7 days took all 35
wafers
> and processed them together.  Soft bake, expose, develop, hard bake and
etch.
> Not a single problem with the 7 day old wafers.  The act of vacuum vapor
> priming dehydrates the wafers under vacuum and while still in a vacuum the
> prime takes place.  This produced a Hydrophobic wafer that resists
moisture
> attacks for weeks.  Let me know if you have any further adhesion
questions, or
> if you want to test vacuum vapor prime.  Bill Moffat
>
> -----Original Message-----
> From: Balaji Lakshminarayanan [mailto:[email protected]]
> Sent: Wednesday, July 03, 2002 5:04 AM
> To: [email protected]
> Cc: [email protected]
> Subject: [mems-talk] Problems with liftoff(on quartz)
>
>
> Hi,
>
> I am having problems with developing photoresist on quartz wafer. The
> photoresist is not sticking to the quartz. Has anyone experienced similar
> problems. In particular, with AZ 5214E which i want to use for patterning
> metal using liftoff. The procedure that i followed is
>
> a) 1.50 HF dip for 15sec
> b) spin-on HMDS+AZ5214
> c) soft back @ 90C/60sec
> d) Expose for 8sec
> e) Hard bake for 110C/45sec
> f) Flood expose for 85sec.
>
> I followed the above procedure on glass and it worked well. Any help on
the
> same will be appreciated
>
> thanks
>
> bala
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