Hi--
        I generally use a 10nm Al overcoat (thermally deposited) over PMMA
for e-beam writing on insulating substrates.  This works great for JEOL
lithography at 50 kV, at 100 pA and 250 pA current.  Now, I am trying to
write at high currents--say 10 nA--and the Al film gets broken up,
destroying my alignment marks, when looking at the sample in SEM mode.
        Any suggestions for eliminating this problem?
        Thanks-

        William Lanford-Crick
        Micro and Nanotechnology Laboratory and
        Department of Electrical and Computer Engineering
        University of Illinois at Urbana-Champaign
        E-Mail: [email protected] -- Phone: 217-390-2998