Ruilin,
Your problem has the appearance of a dirty photomask and is even reminiscent of
reflective notching found in positive photoresists.
Perhaps you can inspect the mask with a microscope and determine if the chrome
edge is clean. You might also look to see if the edge is straight or if large
pixels can be observed.
We have exposed 500 µm films of SU-8 on silicon and glass wafers without
observing this effect.
Best of luck,
Garrett Oakes
-----Original Message-----
From: 郑瑞麟(Ruilin Zheng) [mailto:[email protected]]
Sent: Tuesday, June 03, 2008 12:42 AM
To: [email protected]
Subject: [mems-talk] Wrinkles on the sidewall of SU-8 layer
Hello, everyone,
I met another problem on SU-8 process.
Wrinkles are found on the sidewall surface of SU-8 structure, like 5 X 1 X
0.4 mm cuboid and 50 X 0.1 X 0.4 mm narrow cuboid, after exposure and
development.
The soft-bake temperature is 100 celsius degree/ 2hours, and the post
exposure bake temperature is 100 celsius degree/ 1hour. The exposure doses
are from 600-1200 mJ/cm2.
Also delamination was found after development. I thought this is due to
internal stress, and I tried to lower the post-exposure-bake temp. down to
80 celsius degree/ 2 hour.
But wrinkles are still there, and the amount is not reduced obviously.
Is anyone have some idea about this problem? Please give me some advice.