Mitigation of Line Edge Roughness and Line Width Roughness in Block Copolymer Directed Self-Assembly through Polymer Composition and Molecular Weight Manipulation

摘要

The semiconductor community is well aware of the challenges that exist in developing lithographic methodsthat can pattern features at sub-20 nm periodic feature spacing (pitch, L_0). Optical lithography already utilizescomplex multiple patterning schemes to overcome diffraction limitations at 193-nm exposure wavelengths, andthe delayed insertion of EUV lithography will likely require the use of multiple patterning or other assistiveprocesses to further reduce the achievable feature sizes. An alternative to these techniques employs the directedself-assembly (DSA) of block copolymers. Block copolymers (BCPs) can naturally micro-phase separate intomorphologies such as lamellae, cylinders, spheres, and gyroids at length scales down to sub-10 nm dimensions.Using the ability of BCPs to micro-phase separate in conjunction with alignment methods such as graphoepitaxyand chemoepitaxy to produce well-ordered structures, a process referred to as DSA, offers a possible methodfor producing sub-20 nm features in conjunction with optical patterning processes at greatly reduced cost andcomplexity. One of the many challenges in implementing line-space type DSA processes is the lack of methods foreffective modulation and tuning of the pattern pitch (L_0) produced by a given BCP. Previous studies have shownthat blending homopolymer into the BCP thin films can allow for tuning of both: (1) L_0 to be larger than thatprovided naturally by the BCP's molecular weight (MW) and (2) the relative size line-space size ratio. However,this tuning ability comes at the expense of increased line edge roughness (LER) and line width roughness (LWR).It has also been shown that either higher or lower MW BCP can be blended into a primary BCP in order tomodulate and tune the pattern pitch produced from the BCP mixture, but the effects of this BCP blending onpattern LER and LWR have not been explored or reported in detail. In this study, coarse-grained moleculardynamics simulations of BCP DSA on a chemoepitaxial underlayer were implemented to characterize the impactsthat blending controlled amounts of two different MW BCPs together have on DSA pattern LER and LWR. Theblends shown here had LER and LWR values as much as 20% higher than those of pure, monodisperse BCPs;however, reducing the MW difference between the 2 BCPs could reduce this effect.