Control of morphological defects at the boundary between the periodic and non-periodic patterns in directed self-assembly process

Abstract

In this study, we investigated a directed self-assembly (DSA) flow that could include a non-periodic pattern (i.e., wide line) lying in between the periodic line/space patterns, in a relatively simple and inexpensive way. A symmetric poly(styrene-block-methyl methacrylate) (PS-b-PMMA) with the natural periodicity (L0) of 30 nm was employed here. Our DSA flow has two key features. First, we used a hybrid approach that combined chemoepitaxy and graphoepitaxy methods to generate PMMA-attractive pinning guide patterns directly from ArF resist. Second, we attempted to utilize both the perpendicular lamellae in the periodic regions and the horizontal lamellae on the non-periodic pattern as an etch template. The advantage of this process will be a reduction of the number of lithographic processes, whereas the challenge is how to control the mixed morphologies at the boundary between the periodic and non-periodic regions. Our preliminary results from simulations and experiments showed that, in order to generate the horizontal lamellae on the non-periodic pattern, the PS-b-PMMA thickness on top of the non-periodic guide pattern should roughly match to ~1 L0, and the width of the non-periodic pattern should be larger than ~3-4 L0. In addition, the space between the periodic and non-periodic regions was found to be critical and it should be basically equal to the space between the guiding pins in the periodic regions (~75 nm) to minimize the formation of fingerprint morphology at the boundaries.