YES HMDS can help.  HMDS reacts with hydrogen and or water.  If you
truly dehydrate vacuum and heat is best and can protect the wafer from
seeing moisture laden atmosphere you can get perfect adhesion.   HMDS is
NH-(Si(CH3)3)2.  The NH reacts with the H on the wafer and produces NH3,
ammonia and leaves behind Si(CH3)3.  An inorganic/organic molecule,
perfect for an organic/inorganic bridge.  If the HMDS reacts with an
hydroxyl ion it sticks forever.  If it reacts with a loose water
molecule you get the same outside effect that looks good but it can
release with harsh processing causing rough edges and poor adhesion.

Bill Moffat

-----Original Message-----
From: mems-talk-bounces+bmoffat=yieldengineering.com@memsnet.org
[mailto:mems-talk-bounces+bmoffat=yieldengineering.com@memsnet.org] On
Behalf Of hui yan
Sent: Monday, January 24, 2011 9:56 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] AZP4620 peels off


i m using positive photoresist AZP4620 for photolithography. However,
during the development step, the resist layer peels off when washed with
DI water; though i have tried numerous times and have shorten the
development time to 20s.

I have cleaned my wafer using piranha solution, followed by DI water
rinse, then rinsing with acetone, IPA, DI water. And then dehydrate my
wafer at 120 C for 30 min.

Does HMDS primer helps? if so, what is the recipe for spin coating it?

Regards,
Hui Yan
Mechanical Engineering
National University of Singapore