Extending optical lithography with immersion

As the semiconductor industry looks to the future to extend manufacturing beyond 100nm, ASML have developed a new implementation of an old optical method for lithography. Immersion lithography can support the aggressive industry roadmap and offers the ability to manufacture semiconductor devices at a low k1. In order to make immersion lithography a production worthy technology a number of challenges have to be overcome. This paper provides the results of our feasibility study on immersion lithography. We show through experimental and theoretical evaluation that we can overcome the critical concerns related to immersion lithography. We show results from liquid containment tests focussing on its effects on the scan speed of the system and the formation of microbubbles in the fluid. We present fluid-to-resist compatibility tests on resolution, using a custom-built interference setup. Ultimate resolution is tested using a home build 2 beam interference setup. ASML built a prototype full field scanning exposure system based on the dual stage TWINSCAN(TM) platform. It features a full field 0.75 NA refractive projection lens. We present experimental data on imaging and overlay.