Looking at the profiles it looks like reflections - diffusion will have more
uniform line widening
shay

-----Original Message-----
From: Christoph Friese
Sent: Thursday, September 29, 2005 12:54 PM
To: [email protected]
Subject: [mems-talk] SU-8 over-exposure

Hello,

I'm working on SU-8 2010 for layers with a thickness of about 20µm on Pyrex.

I exposed these layers with 120sec, 60sec and 30sec (with 9mW/cm2) and I'm
observing some kind of overexposure (extrem with 120sec and nearly invisible

at 30sec).

[Pictures at http://www.imtek.de/micro-optics/SU8/SU8_2010_Exp.jpg]

All three wafers are treated the same way, except the exposure dose. Could
someone tell me what is exactly happening in the areas between the tines?

Is this kind of a diffusion of the activated acid or just internal
reflections between the substrate (Pyrex) and the mask?