Development Status of High Performance Materials for Immersion Lithography

This paper concentrates on the affect of resist elution to immersion lithography. Resist elution negatively impacts resist performance and causes contamination to the optics in immersion lithography. Two concepts will be discussed that minimize the resist elution issue when water is used as the immersion fluid. One countermeasure approach is to optimize the resist formulation and the resist process. Our study indicates that the process influences elution during resist exposure and baking steps and optimization of these steps is necessary. Also, resist components, such as photo acid generator, amine quencher, and casting thinner, can affect elution. The second approach is the application of a cover material on the resist film. A new developable cover material will be introduced that would eliminate both the elution issue as well as an additional removal step. The new developable cover material will also offer good imaging performance for 45nm lines, using a two-beam interference exposure tool.