Preliminary results from a prototype projection electron-beam stepper-scattering with angular limitation projection electron beam lithography proof-of-concept system

We have designed and constructed a proof-of-concept projection electron beam Lithography system based on the scattering with angular limitation projection electron beam lithography principle. In this system, a thin membrane mask is used in a 4:1 reduction projection system at 100 keV. Image contrast is formed by scattering in the mask and subsequent aperturing of the scattered electrons in the back focal plane of the projection system. We have employed a step-and-scan architecture which uses continuously moving mask and wafer stages to trace out the full pattern. The electron beam can thus be kept small (1x1 mm in our case) which greatly simplifies the design of the electron optical system. In addition, the membrane areas can be kept small in linear dimension in one direction, minimizing in-plane pattern distortions. Our system will be constructed in two stages. In the first stage, the mask stage is static and the wafer stage operates in step-and-repeat mode. This initial version of the system allows for critical experiments regarding the mask, resist exposure, and electron optics to be performed. Later, a continuously moving stage system will be integrated. In this article, we report on the initial results from the static system. We have printed features as small as 80 nm and measured a 75 mu m depth of focus for nominal 0.25 mu m features in negative tone P(SI-CMS) resist. (C) 1996 American Vacuum Society.