Wednesday, February 18, 2009

US Patent 7491661 - Immersion lithography including nanoparticle suspension topcoat

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.