hi, shifeng

I think you'd better increase the strip time of gold, maybe the residue gold
layer prevent the development. And loger develop time will be better, 60s goes
well for PMMA in my lab. Did you use the pure IPA to fix the patterns after the
development? This process should not be omited.

When you use SEM to check the patterns, you shold use the lowest voltage and the
shorter exposure the better, otherwise the SEM electrons will turn the resist to
black. And depositing 1~2nm gold layer give a big help in SEM observing for the
insulating substrate. And you should make sure what you observed is the
patterned side, because it is very easy to make mistake for the transparent
substrate.

Liwei Shang



On 25/11/2008, at 3:12 PM, li shifeng  wrote:
Hi, guy
I'm trying to write some patterns on glass substrate. Here is my process:
Spin coat 500nm PMMA 950 C4,
Sputtering 5nm gold
EBL exposure
Strip gold using TFA gold etcant for 6 second
Develop in MIBK : IPA= 1:3 for 30 sec
The problem is I cannot find any pattern on the substrate afterwards. What are
the possible reasons for that?  Anyone have similar experiences on this or has a
working recipe to share?