We have developed a processing method that employs direct surface imaging of a surface-modified silicon wafer to
define a chemical nanopattern that directs material assembly, eliminating most of the traditional processing steps.
Defining areas of high and low surface energy by selective alkylsiloxane removal that match the polymer period length
leads to defect-free grating structures of poly(styrene-block-methyl methacrylate) (PS-b-PMMA). We have performed
initial studies to extend this concept to other wavelengths beyond 157 nm. In this present paper, we will show that electron beam lithography can also be used to define chemical nanopatterns to direct the assembly of PS-b-PMMA films. Half-pitch patterns resulted in the directed assembly of PS-b-PMMA films. Electron beam lithography can also be used to prepare surfaces for pitch division. Instead of the deposition of an HSQ pinning structure as is currently done, we will show that by writing an asymmetric pattern, we can fill in the space with smaller lamellar period block copolymers to shrink the overall pitch and allow for 15-nm features.
A potential extension of water-based 193-nm immersion lithography involves transition to a higher refractive index
organic immersion fluid coupled with a higher index last lens element. While considerable progress has been made in
improving the photo-durability of the immersion fluid itself, photo-induced contamination of the last lens element
caused by laser exposure in the presence of such organic fluids remains a major concern. In this work, we study
remediation strategies for such contamination, which would be compatible with conventional lithographic production
environments. In general, surface photocontamination layers were found to be highly graphitic in nature, where the
first monolayer is strongly bound to the substrate. We have attempted to develop a surface passivation treatment for
altering the monolayer chemistry and preventing large-scale contamination, but found such treatments to be unstable
under laser irradiation. On the other hand, using hydrogen peroxide as a in-situ cleaning solution has been shown to be
extremely effective. We also present first laser-based durability results of LuAG, which is a leading candidate
material for high index last element to be used with high index fluids.