Hi

We are trying to coat su8 10 over the silicon wafer for a thickness of
resist 20 um. The protocol specified by Micro chem is followed for this
thickness.Spin speed of 1590 rpm with acceleration of 300 rpm and 30
seconds. The problem is, after coating the Su8 over the wafer, suddenly
resist form islands over the wafer (resist balling up and leaving small
empty pores). Thus the channels of 10 um is not possible to form.

We also tried to coat an HMDS coating to improve the adhesion. But the
balling up effect increased. Instead of small diameter pores, It form large
diameter vacant spaces.

We done an HF dip (1: 5 ratio) before the coating of su8 and dehydration of
wafer with 150 C at about 10 minutes.Is it problem of lack of cleaning of
wafer. Any other cleaning procedure should follow for this?

Please suggest me some remedy for this

--
Sajeesh P
Mechanical Engineering Dept
IIT Madras
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