The TCE of silicon and SU8 are very different and the SU8 profile tend to
have slightly negative slopes or 'undercutting' sometimes which makes
demolding different.

Try to use DRIE structure in Silicon as the mold

Shay

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Meifang Lai
Sent: Wednesday, July 09, 2008 11:51 AM
To: 'General MEMS discussion'
Subject: [mems-talk] adhesion problem for SU-8 on Si when hot-embossing

Hi all,

I am developing a mold for hot-embossing by using SU-8 2050 on Si wafer. At
present, I can get beautiful structures on Si after the photolithography
process  (including hard bake at 150 ?C for 30 min). However, when I was
trying to transfer the structure to PMMA (1 inch square) by hot embossing
(pressure is 300 Kg, 125 ?C for 10min, and the demolding temperature is 90
?C), all the Su-8 structures stayed in PMMA and separated from Si wafer. I
have tried the HMDS, but it seems no difference. Does anyone have similar
experience? Any suggestion will be appreciated.