Development of new advanced resist materials for microlithography

This paper reviews development of advanced resist materials which I have been involved in for more than a quarter century. First, our attempts to increase the main chain scission susceptibility are described. Next, a simple lift-off process for fabrication of magnetoresistive heads for storage devices is presented, which became the industry-standard-manufacturing technology. Then, the major focus is going to be placed on the development of chemical amplification resists. Chemical amplification resists achieve a high sensitivity through a catalytic action of a photochemically generated acid. This drastically novel imaging concept was considered laboratory curiosity initially. However, the very first chemically amplified tBOC resist was quickly implemented in mass production of 1 megabit dynamic random access memory devices by deep UV lithography at IBM. Since then the chemical amplification concept has become the paradigm of advanced resist systems, enabling the industry to continue to migrate to shorter wavelengths (from 365 to 248, and then to 193 nm) for higher resolution and to follow the Moore's law. The chemical amplification resist invented for 1 mu m resolution can now resolve < 30 nm equal line/space patterns and continues to play a pivotal role in microlithography in the foreseeable future.