(404f) Predicting Process Windows for Block Copolymer Directed Self-Assembly with Chemoepitaxial Guiding Underlayers with Pattern Density Multiplication
Directed self-assembly (DSA) of block copolymers (BCPs) using pattern density multiplication is a technique of producing patterns with small pitches utilizing guiding template patterns printed as larger feature sizes and pitches. A chemoepitaxial guiding underlayer is one such method for achieving this density multiplication. This nominally topographically flat guiding underlayer is composed of a pinning region, or stripe if referring to lamellae, which will chemically interact preferentially with one microphase of the BCP, as well as a second region that is often referred to as “neutral” to both phases of the BCP. Typically, the pinning stripe is the width of a single lamellae of the phase separated BCP, while the neutral stripe is some odd number of lamellae widths. In this work, detailed simulation studies have been performed to explore the effects that variables such as guiding stripe size or chemical composition of the neutral stripes have on the process window of DSA pitch sub-division patterning processes. The impact of such factors on both the overall alignment of the BCP film as well as the quality of the resulting lamellae (e.g. whether various compositions are more prone to induce footing in their respective lamellae or not) have been evaluated. Such process windows and lithographic parameters have been studied for different pitch sub-division conditions for ratios of pinning stripe width to neutral stripe width of 1:3 and 1:5. It is found that the center of the processing window with respect to alignment occurs at a composition of the “neutral stripe” such that it is slightly to somewhat strongly preferential to the type of polymer of opposite type to that attracted by the pinning stripe, and that this ideal “neutral stripe” composition becomes more neutral as the density multiplication increases. This ideal composition for alignment is near, though not necessarily the same as, the ideal composition for achieving the best lamellae quality, such as in the case of a 1:3 pattern where the best lamellae quality occurs at a higher composition than the best alignment.