Use of positive and negative chemically amplified resists in electron-beam direct-write lithography

This article describes the performance of available deep-ultraviolet (UV) resists for electron-beam direct-write lithography applications, Shipley XP9402, JSR KRF-K2G, acid JSR KRF-L7 positive resists were evaluated for dark-field layers and Shipley XP90166 negative resist for clear-field layers. We investigate in detail the resolution capability, sensitivity, exposure latitudes and proximity, and postexposure delay (FED) time stability for isolated and dense features, as well as for contact holes. The influence of baking conditions on resolution and stability will be described. FED time effect in air and vacuum is measured for features with dimensions down to 0.2 mu m. No linewidth variations are observed down to 200 nm feature size with XP9402 for a delay time of 1 h in air if the postexposure bake (PEB) is done at low pressure in He ambience. Feature sizes down to 0.25 mu m are kept within +/- 10% of the coded size, for a FED in air of 90 min if the FEB is done using a conventional hot plate in air. A process for printing 0.2 mu m contact holes is established. Resolution down to 0.15 mu m for dense, 0.12 mu m for isolated features, and 0.2 mu m for contact holes is obtained with KRF-K2G for FED of 11/2 h in air using a top coating. FED stability of more than 2 h and resolution down to 0.2 mu m for contact holes is obtained with KRF-L7 without applying a top coating. For clear-field layers we focus on a negative tone process. Resolution and process latitude issues using reduced resist thickness will be described. With 560-nm-thick XP90166. resist lines smaller than 0.2 mu m are resolved over polytopography with better than 25% exposure latitude. Further reducing the resist thickness to 500 nm, poly-Si gates with size down to 0.15 mu m are defined on the shift register of a 0.25 mu m random logic complementary metal-oxide-semiconductor design. (C) 1995 American Vacuum Society.