Hi Shifeng, If you can't find them then they are usually either underexposed (or really a lot overexposed) or you simply look in the wrong place. What are the dose and current and how big are your structures? Another possibility is that there's a problem with SEM imaging (or what do you use for characterisation?): PMMA is a polymer so you should either use a metal layer on top (maybe Ti or Al) or you need to use low vacuum. Otherwise charging effects are too string and you simply burn your PMMA away. Maria ________________________________ From: mems-talk-bounces@memsnet.org on behalf of li shifeng Sent: Tue 25/11/2008 05:12 To: mems-talk@memsnet.org Subject: [mems-talk] EBL on the glass substrate 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? Thanks!