Resist Schemes for Submicron Optical Lithography

In this paper we will first try to explain why optical lithography with single layer positive resist is still a dominant technology today, even for submicron resolution. To this end we will indicate how the materials and processes have been improved to cope with the more stringent requirements. Next we will look at the future, at feature sizes under 0.7 ¿m and down to 0.3¿m. For these small sizes the limitations imposed by the imaging equipment and the transfer processes call for new resist systems. The type of systems that are most promising are the pseudo monolayer and bilayer systems. Their relative merits are compared, and issues relating to the implementation in fab environments are discussed.