Study on the Polishing Performance of Silicon Carbonitride (SiCN)

Abstract

Chemical mechanical polishing (CMP) becomes a major process in IC integration as gate length shrinkage. Moreover, its usage becomes wider at sub-14nm device manufacturing due to new structure and new material introduction. Enabling new material for planarized structure, polishing performance is required. Silicon carbonitride (nitrogen-doped silicon carbide (SiC) or SiCN) thin film is one of the new materials for sub-14nm device fabrication. SiCN thin film becomes more and more attractive as capping dielectric layer and diffusion barrier in addition to etch stopping layer. We have developed a process to form SiCN with tunable carbon concentration (5-15%). And SiCN thin film is applied for poly opening CMP (POC) process scheme. In order to enable SiCN as POC, polishing performance with enough selectivity between SiCN and silicon dioxide (SiO2) need to be achieved. For this purpose, this paper provides experimental results of SiCN polishing performance with silica-based slurry. Effects of polishing variables and slurry chemistry on the removal rate are intensively explored and post CMP defect performance is investigated as well. The results suggest acidic silica slurry with optimized recipe would be suitable for SiCN polishing.