Deep UV Pattern Definition in PMMA

We have patterned polymethyl methacrylate (PMMA) resist by exposing it with the fifth harmonic (213 nm) of an Nd:YAG source through metallized apertures in contact with the resist. Interference patterns with both near- and far-field origins were observed. In order to test the contrast and uniformity of exposure, we deposited germanium onto developed areas to form arrays with feature sizes of approximately 200 nm. We present a straightforward model for interference effects generated in our process, and discuss opportunities for direct-write lithography through single apertures.