Photolithographic Methods for Vlsi: Myths and Beliefs

Abstract

The technology of imaging for transferring a desired pattern onto the semiconductor wafer comes in the forefront in an effort to scale down geometries in LSI/VLSI. Conventionally, semiconductor imaging technology involves first fabrication of a mask and then transferring the pattern onto the wafer through lithographic techniques. Tremendous strides have been made in this area over the last decade. While the ultimate objective would be to eliminate the intermediate step of mask fabrication, it does not seem to be achieveable in the foreseable future.

This paper attempts to analyse the various imaging technologies available such as optical, X-ray, E-beam etc. and brings out certain hard facts about each of these technologies, which would hopefully help one in choosing the right option. The paper also provides a discussion on mask materials, photoresist systems and the effect of defects upon yield and reliability of LSI/VLSI.

Indexing Terms:

• Semiconductor Imaging Technology
• Mask Fabrication
• Photoresists
• VLSI
• ICs
• Lithography