Characterization of mask fabrication for submicron geometries using a shaped vector electron-beam system

Abstract

The requirements for mask fabrication have increased dramatically with recent advances in lithographic techniques and new i-line, x-ray and deep UV systems. For example, phase shifting masks for 5x steppers require submicron phase shifters, tight critical dimension control and pattern alignment capabilities. X-ray steppers and other lx technologies require subhalf micron resolution and even tighter critical dimension control with excellent dimensional linearity. These requirements approach the limit of capabilities of traditional e-beam mask fabrication systems. At TRW, a Hitachi HL-700D direct write on wafer e-beam tool has been used in a production environment for a half micron CMOS technology. This shaped beam vector scan system is also capable of mask fabrication. It offers unique mask fabrication capabilities due to the implementation of advanced proximity correction algorithms to maintain submicron dimensional control and line size linearity. The system also supports a 0.10 micron x-barplus three sigma alignment capability. This paper will review a program that has been implemented to evaluate the ultimate resolution and overlay capabilities of the Hitachi system for mask fabrication. Subhalf micron mask resolution will be characterized and explained in terms of proximity correction algorithms. Different chrome etching techniques will be evaluated for critical dimensional control. Finally, an analysis of the effectiveness of the alignment system for phase shifting masks will be presented using applicable test structures