Selective plasma etching of silicon-containing high chi block copolymer for directed self-assembly (DSA) application

Abstract

Directed self-assembly (DSA) of block copolymers (BCPs) is an advanced patterning technique being investigated to obtain small and dense patterns for future technological nodes. In order to demonstrate the potential of DSA to extend optical lithography, poly(styrene-b-methyl methacrylate) (PS-b-PMMA) has been the most commonly used block copolymer in different applications, such as line/space and contact hole patterning as well as uniformity repair. However, the minimum pitch for the PS-b-PMMA system is limited to around 24 nm due to its relatively weak segregation strength. Therefore, block copolymers with stronger microphase segregation have been developed to enable sub-10 nm patterning, thus obtaining the so-called “high chi” BCPs. In this article, the silicon-containing high chi system investigated is the poly(styrene-b-1,1-dimethylsilacyclobutane) (PS-b-PDMSB) presenting a pitch of 18 nm. A one-step top coat and PS removal based on H2/N2 plasma that presents good selectivity and profile has been studied. The H2/N2 gas ratio has been investigated to understand the trade-off between obtaining high selectivity and avoiding pattern collapse. Using this approach, the pattern transfer into different underlayers is demonstrated for the high chi PS-b-PDMSB.