Hello Andrea,

Your lithography process sounds fine.  Shipley makes S1827 positive photoresist
that is designed for thicker coat applications.  The "peeling" you describe may
be the resist is being undercut so thicker (or different) resist may not help.

Good Luck,

Mike

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Andrea Mazzolari
Sent: Wednesday, August 15, 2007 6:19 PM
To: [email protected]; General MEMS discussion
Subject: [mems-talk] photoresist suggestion


Hi all, i need to pattern a 400um thick silicon nitride film. I'm planning to
use BHF (1:7) to remove silicon nitride from unwanted areas. Etch rate of
silicon nitride is about 1nm/min, so the etch time will be about 400 min. About
photoresist: i've tried to use s1813, but it peel off after about 5 hours etch.

Here is the procedure i've followed:
spinning of primer
spinning of s1813
soft bake (2 min at 120 °C)
photolitography
hard bake (2 min at 120 °C)

How can i improve s1813 resistance to BHF? May a thicker s1813 layer help ? Or a
longer hard bake time ? Any idea about an alternative photoresist ?