Mixed e-beam/optical lithography process for the fabrication of sub-0.25-μm poly gates

Abstract

In this paper we investigate the use of two negative resists, a commercially available negative tone electron beam resist (CAR), and AX-E, an IBM resist, with a 50 KeV variable shaped electron beam system. All aspects of processing and tooling were investigated to understand the impact on critical dimension control. Post applied and post exposure bake times and temperatures were examined in an effort to optimize resist contrast, resist profile, and gate linewidth variations. Proper tool set-up and proximity correction were also investigated. SEM metrology as well as high resolution SEM cross-section metrology were extensively used in the process optimization. A complete understanding of the resist, processing, tool and metrology have resulted in the fabrication of working devices and circuits with physical gate linewidth dimensions down to 0.10 micrometers with a 3(sigma) better than +/-0.03 micrometers across a wafer.