US Patent 7491661 - Immersion lithography including nanoparticle suspension topcoat

http://www.freepatentsonline.com/7491661.html

Higher resolution lithography is necessary to continue Moore's Law of increasing transistor density. One method to achieve such enhanced resolution is immersion lithography which uses a liquid medium to increase the index of refraction . This patent from ASML Netherlands B.V. teaches using a nanoparticle-based top layer to avoid internal reflection in immersion lithography systems. Claim 1 reads:

1. A device manufacturing method, comprising:

projecting a patterned beam of radiation through a liquid onto a resist provided on a substrate, wherein a topcoat layer is provided between the resist and the liquid, the topcoat comprising a suspension of nano-particles.