Affiliation:
1. School of Microelectronics Shanghai University Shanghai 201899 China
2. Shanghai Institute of IC Materials Co. Ltd Shanghai 201899 China
3. State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 China
Abstract
AbstractIn the photolithography process of integrated circuits （IC） manufacturing, it is desired that the photoresist resins have both smaller polydispersity index (PDI) and lower trace metal ion concentrations. The commercial environmentally stable chemical amplified photoresist (ESCAP) resins for 248 nm lithography are synthesized by free radical polymerization with PDI >1.5. Although using atom transfer radical polymerization (ATRP) can result in lower PDI, the potential of high metal ion contamination is a major concern, as the reaction initiators usually are copper‐containing compounds. In this study, copolymer of p‐acetoxy styrene and tert‐butyl acrylate [poly(AOST‐co‐TBA)] is synthesized via ATRP achieving PDI as low as 1.25. It is then purified by ion exchange with two different resins, IRC747 and A15, which are effective at removing Cu and other metal ions. This reduces the total metal ion concentration in the copolymer powder to <30 ppb with individual metal ion <6 ppb. This is the first reported ATRP synthesized ESCAP resin having both low PDI and metal ion concentrations suitable for 248 nm photoresist application.