(226n) Pattern Density Multiplication of Block Copolymer Directed Self-Assembly Using a Chemoepitaxial Guiding Underlayer with Topography

Pattern density multiplication in the directed self-assembly (DSA) of block copolymers (BCPs) is often achieved through a chemically patterned guiding underlayer, also known as a chemoepitaxial guiding underlayer. These underlayers are typically considered flat underlayers composed of a pinning stripe region (i.e. a region that is highly preferential to one block of the BCP) and a neutral stripe region (i.e. a region that is non-preferential or weakly preferential to the opposite block of the BCP as compared to the pinning stripe).  However, in reality it is likely that some level of topography will be introduced when producing these chemoepitaxial underlayers, possibly by improper backfilling or etching, which then has the ability to affect the resulting microphase separation and alignment processes.  This topography may also cause deformations in any resulting lamellae, which may interfere with subsequent pattern transfer etching steps. Due to the complexity of creating test patterns to study such effects and the difficulty in performing adequate metrology on such test samples, detailed mesoscale molecular dynamics simulations have been used in this work to probe the effect of topography on chemoepitaxial DSA processes. The current work presented in this paper systematically explores the effect that topography in these chemoepitaxial underlayers, such as a raised or lowered pinning stripe, has on the alignment of the BCP film. The effect of even small levels of topography is found to be potentially profound.  For example, it is found that small amounts of topography which raise the pinning stripe can greatly alter the ideal composition of the neutral stripe in these systems, shifting the composition to a more neutral value. This topography can also cause increased defects buried within the film due to the compression of lamellae within the trenches of the topography.  Likewise, processes that result in depressed pinning stripes also alter the process windows and behavior of such processes.  A complete discussion of these effects will be provided.