Streamlined etch integration with a unique neutral layer for self-assembled block copolymers (BCPs)

摘要

A multifunctional hardmask neutral layer (HM NL) was developed to improve etch resistance capabilities, enhance reflectance control, and match the surface energy properties required for polystyrene block copolymers (PS-b-PMMA). This HM NL minimizes the number of substrate deposition steps required in graphoepitaxy directed self-assembly (DSA) process flows. A separate brush layer is replaced by incorporating neutral layer properties into the hardmask to achieve microphase separation of BCP during thermal annealing. The reflection control and etch resistance capabilities are inherent in the chemical composition, thus eliminating the need for separate thin film layers to address absorbance and etch criteria. We initially demonstrated successful implementation of the HM NL using conventional PS-b-PMMA. A series of BCP formulations were synthesized with L_0 values ranging from 28 nm to 17 nm to test the versatility of the HM NL. Quality "fingerprint" patterns or microphase separation using 230°-250℃ annealing for 3-5 minutes was achieved for an array of modified BCP materials. The HM NL had water contact angles at 78°-80° and polarities in the 5-6 dyne/cm range. The scope of BCP platform compositions evaluated consists of a 20° water contact angle variance and a 10-dyne/cm range in polarities. All BCP derivatives were coated directly onto the HM NL followed by thermal annealing followed by SEM analysis for effective "fingerprint" patterns. We offer a simplified alternative path for high etch resistance in a graphoepitaxy DSA flow employing a single-layer hardmask for etch resistance demonstrated to be compatible with diverse BCP-modified chemical formulations.