OPTICALLY MATCHED TRILEVEL RESIST PROCESS FOR NANOSTRUCTURE FABRICATION

A novel trilevel resist process has been developed which enables high- contrast imaging of periodic structures with spatial periods down to 2 00 nm in thick resist on highly reflective substrates, using lambda=35 1.1 nm argon-ion laser exposure. The process utilizes a 200-nm-thick, high-contrast, imaging resist layer, a thin (similar to 15-nm) evapora ted dielectric interlayer, and a 300-600-nm-thick bottom antireflectio n coating (ARC) which suppresses reflections from the substrate. Our t rilevel resist scheme has been implemented in a manufacturing process which utilizes a high-contrast interferometric lithography system for the formation of large-area, 200-1000 nm period grating and dot array images. The choice of interlayer is the most critical feature of this process. This material must have good deposition and adhesion properti es, must be optically matched to the resist and ARC, must etch quickly during the reactive-ion etching (RTE) pattern transfer from the resis t into the interlayer, must display very high selectivity to the ARC d uring the RIE pattern transfer into the bottom layer, and must be easi ly stripped after the trilevel resist structure has served its purpose . We also report on computer modeling which elucidates the factors inf luencing standing wave formation and present results of tests with sev eral interlayer materials which display good optical matching and sele ctivities of up to 240:1 during RIE of the ARC. (C) 1995 American Vacu um Society.