Electron beam lithography, directions in direct write and mask making

Abstract

Two major categories of electron beam lithography systems have been developed over the course of many years: Direct write of chips on silicon, and patterning of optical masks on quartz and glass substrates. This paper addresses this dual role and what it implies for the different classes of electron beam lithography tools. In direct write, with dimensions at and below 0.25 μm, tool resolution, accuracy in registration and overlay, process integration, and other factors are of critical importance. Most recent advances in this area will be described. Current work on device fabrication below 0.25 μm demonstrates the capability to integrate all sectors of electron beam lithography to provide early research work for ULSI device technology demonstration. These dimensions are necessary for the fabrication of 256 MB DRAM chips, for example. For mask making it is widely ackowledged that much of the learning from direct write electron beam lithography tools becomes applicable to mask patterning as well. However, more stringent requirements are burdened in particular on x - y stage accuracy and long term overall systems stability.