Block copolymer directed self-assembly using chemoepitaxial guiding underlayers with topography

Guiding underlayers are used in the directed self-assembly of block copolymers (BCPs) to form large defect free arrays. These underlayers traditionally have divided into two categories: chemoepitaxial underlayers which guide the BCP using regions of differing chemical preference and graphoepitaxial guiding underlayers which guide by topographic features built into the underlayer. However, multiple hybrid approaches have been introduced over recent years using both topographic features and chemical preference to direct the BCP film. In this work, a coarse-grained molecular dynamics model is used to explore both the geometric aspects and the chemical preferences of these hybrid underlayers and the effect these variables have on the defectivity of the BCP film. It is found that hybrid underlayers with vertical sidewalls behave in manners similar to more purely graphoepitaxial guiding underlayers, while hybrid underlayers with sloped sidewalls behave in a manner similar to chemoepitaxial guiding underlayers. With vertical sidewalls, it is found that larger topographic step heights decrease defectivity although with diminishing returns. It is found that the width of the trench in these cases should be an integer multiple of the natural repeat distance of the block copolymer although the width of the trench can have approximately 10% error before significantly affecting the defectivity of the simulated BCP. With straight sidewalls, the ideal case is to have a neutral surface on top of the mesa and at the bottom of the trench. A variety of sloped sidewalls were explored. It was found that with sloped sidewalls, there is an optimal topographic height that minimizes defectivity. It was also found that a triangular topographic feature yields far lower defectivity than a similarly sized rectangular topographic feature. (C) 2017 American Vacuum Society.