Hi Junyu,
         You should first make sure that your PMMA is appropriately baked (I
do PMMA on a 200 deg. C hotplate for 2 minutes).  But I did once have a
similar problem when using an evaporator system which had a bad pressure
gauge.  After it was discovered that the gauge was bad, I realized I had
been depositing the metal (also Ti/Gold) at about 10E-4 T, which resulted in
a problem similar to what you described.  Make sure that you have good base
pressure--about 10E-6 T or lower is best.  At higher pressures, you need
more heat to achieve the same rate.

         Good luck!
         -Bill
         -----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of MAI, JUNYU
Sent: Monday, February 13, 2006 4:16 PM
To: [email protected]
Subject: [mems-talk] prblem with Au deposition on PMMA

         Hi, I used Edwards ebeam evaporator to deposit 5nm Ti and then 50nm
Au on PMMA (A5). But the
         resulting coated PMMA has a very rough surface and it seems there
are many big and small bubbles
         bursted there.