1-micron MOSFET VLSI technology. VI - Electron-beam lithography

This paper discusses the fabrication of 1-micron minimum linewidth FET polysilicon-gate devices and circuits. These were designed for the tight dimensional ground rules (resolution, linewidth control, and overlay) achievable using direct wafer write scanning electron-beam lithography with individual chip registration. The present work focuses on vector-scan electron-beam technology and processing, while other papers in this series discuss other aspects of the work. Different types of 1-micron MOSFET chips were written on 57-mm Si wafers using a totally automated electron-beam system which performs table stepping, registration to fiducial marks, and pattern writing in a vector-scan mode (on an individual shape basis) with control of exposure dose for individual shapes. The pattern data were prepared by batch processing which includes proximity correction as well as sorting of shapes to achieve data compaction and minimal distance between shapes. A novel two-layer positive resist system has been developed to achieve reproducible liftoff profiles over topography and better linewidth control.