Balancing Block Copolymer Thickness over Template Density in Graphoepitaxy Approach

Directed self-assembly (DSA) of block copolymers (BCP) is one of the most promising patterning solutions for sub-10 nm nodes. While significant achievements are demonstrated in pattern fidelity for various applications (contact shrink, line patterning), some challenges are still needed to be overcome especially regarding the defect density reduction, in order to ensure DSA insertion in high-volume manufacturing. In particular, in the case of the graphoepitaxy approach, a remaining challenge is to solve the pattern-densities-related defect issue due to BCP film thickness variation inside the guiding template. In order to address this issue, a new DSA process flow called DSA planarization is employed for contact-hole patterning, and consists in overfilling the guiding pattern cavities with a thick BCP film, followed by a plasma etch-back step. This new approach ensures a uniform control of the final thickness of the BCP inside guiding cavities of different densities, as demonstrated herein by AFM measurement. Thus, defect-free isolated and dense patterns for both contact shrink and multiplication are simultaneously resolved. Furthermore, the simulation results of BCP self-assembly overfilling the templates demonstrate that BCP domains are well-directed in vertical cylinders ordering inside guiding cavities, which confirms the experimental results and the viability of this approach.