Thanks for all the comments. I have finally found out the problem. The UV
lamp output was much lower than expected, anyway the UV aligner is very old
(born in 1981) after all.... Now, I need to double the exposure time to
achieve the same exposure dose....

Bill

-----原始郵件-----
From: Tinka Li
Sent: Wednesday, January 23, 2013 6:13 AM
To: [email protected]
Subject: [mems-talk] Double layer SU-8 fabrication problem

Hi, Bill,



I think your problem is why your process that previously worked suddenly
failed. The expire date of your resist should not be a problem, but, most
probably, your process window is not large enough. You may have marginally
succeeded in your previous runs. All lab tools are not well
maintained/monitored. Things may have drifted, say, there was maintenance
recently, your spinner is slowing down, your hotplate temperature is getting
lower, or you just used different tools. So that your 1st Su8 was not dried
enough (or less enough than before). Btw, did you measure the 1st SU8
thickness? To remove the wrinkle, in some fabs, it is more or less standard
to do a "N2 treatment" (N2 plasma) to passivate the 1st PR layer in double
PR layer process. It may also help you.



Tinka

Prime Wafers

Van der Takstraat 8

3071 LL, Rotterdam

The Netherlands

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