Directed self-assembly of diblock copolymers in multi-VIA configurations: effect of chemopatterned substrates on defectivity

Abstract

Directed self-assembly (DSA) of block copolymers has gained much attention for its potential as a low-cost, high-throughput patterning tool to supplement existing lithographic techniques, and in particular for its ability to easily pattern vertical interconnect accesses (VIAs).1 Single-hole shrink has been extensively explored, but the continued push towards higher-resolution patterns requires more efficient, less space-consuming approaches. The lithographic resolution limits the minimum distance between two features, and the single-hole templates take up valuable real estate on the wafer.2 To accommodate denser features and relax the resolution requirements of the lithographic techniques, it is prudent to move to multi-VIA configurations in which two or more features are assembled in a single guiding template (such as a peanut,3 or a rounded rectangle4). This allows considerably denser feature patterning, but comes at the cost of more plentiful and complicated defect modes than those found in single-hole shrink features. Most systems contain persistent horizontal structures (eg. rings, U-defects, or bars as shown in Figure 1) that prove detrimental to the etch process and yield undesirable configurations. Largely unexplored is the tandem use of chemoepitaxy and graphoepitaxy to suppress defect modes in multi- VIA templates. Specifically, chemically selective patterning of the substrate beneath a template could act synergistically with the template's lateral guidance to lower defectivity. In this study, we use three-dimensional self-consistent field theory (SCFT) simulations to investigate the equilibrium and metastable defective configurations of di-block copolymer DSA systems in the presence of chemically selective or neutral template sidewalls and preferentially attractive striped substrates. We identify chemo-patterning schemes that maximize defect energies, including sidewall interaction strength and chemical preference. In addition, we discuss chemo-patterning schemes that backfire, creating even more complicated and persistent defect modes such as horizontal half-cylinders on the system substrate.