Try using polyimide. Make sure you get the solvent based polyimide, not
water based. Do a spin on and then cure it, I would try 20,000
angstroms. I think it should resist BOE and HF, and you can strip it
with a long oxygen plasma.

The only possible issue might be delamination, but polyimide has fairly
good adhesion.

Ed

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Yu Wang
Sent: Monday, September 21, 2009 3:53 PM
To: General MEMS discussion
Cc: Celik-butler, Zeynep
Subject: [mems-talk] Transparent layer protecting Al,PolySi and nitride
from BOE/HF dip


Hi,

I'm looking for a transparent layer that can protect my Al, polysilicon
and nitride patterns from BOE/HF dip for 200-300minutes. There are three
strict requirements:

(1) The layer can withstand BOE/HF dip for 200-300minutes

(2) The adhesion of the layer to its underlying Al, Polysilicon and
nitride patterns is strong enough so that it will not be peeled off by
BOE/HF dip.

(3) The layer is easily stripped by ite remover without damaging the Al,
Polysilicon and nitride patterns.

I have tried SU8. It is good in (1), but bad in (2) and (3).

Any suggestions will be appriciated.

Thanks,

Yu Wang