Three-dimensional x-ray metrology for block copolymer lithography line-space patterns

Abstract

We report on the development of a new measurement method, resonant critical-dimension small-angle x-ray scattering (res-CDSAXS), for the characterization of the buried structure of block copolymers (BCP) used in directed self assembly (DSA). We use resonant scattering at the carbon edge to enhance the contrast between the two polymer blocks and allow the determination of the three-dimensional shape of the native lamella in a line–space pattern by CDSAXS. We demonstrate the method by comparing the results from conventional CDSAXS to res-CDSAXS on a 1:1 DSA BCP sample with a nominal 50-nm pitch. The res-CDSAXS method provides substantially improved uncertainty in the fit of the line shape and allows the determination of the buried structure.