Effect of Diammonium Hydrogen Phosphate on Si3N4 and poly-Si selectivity in wet ceria based CMP Slurry

Abstract

이 논문에선 3D-Nand flesh poly stop CMP 공정과 HKMG POP(poly open polising)공정에 쓰일 수 있는 Si3N4 to poly-Si high selectivity Ceria slurry에 대해 연구하였다. 이러한 high selectivity slurry는 기존에는 Silica 기반 slurry 위주로 연구되었기에, Ceria slurry 기준으론 어떤 메커니즘에 의해 선택비기 조절되는지를 알아보려 했다. 특히나 Ceria는 Silica대비 Scratch 특성이 좋지 않으므로, 이점 역시 함께 개선해야 헀다. 고선택비를 구현하기위해선 DAHP라는 음이온성 이온과 PEO라는 non-ionic polymer 를 1wt% Ceria slurry에 첨가하였고, 두 Chemical의 농도를 적정화하여 Si3N4 to poly-Si=43:1의 고선택비 slurry를 개발하였다. 또한 기존 Ceria slurry에서 발견되었던 Scratch현상 역시도 두 Chemical을 첨가하며, 없어진 것을 확인할 수 있었다. 각 Chemical들이 어떻게 선택비에 영향을 주는지를 확인하기 위해 흡착 평가( FT-IR, Zeta potential, Contact Angle ), 표면분석(OM,SEM,AFM), 표면원소분석(XPS)를 실행하였다. DAHP와 PEO는 Ceria입자와 SI3N4 혹은 poly-Si 필름과의 흡착 특성을 조절하여, 선택비를 구현하였고 Chemical하게 polishing mechanism을 바꾸진 않았다. DAHP와 PEO는 각기 개별적으로 넣었을 때에도 선택비 향상 효과를 내었으나, 둘을 함께 넣었을 때는 Synergy효과에 의해 poly-Si 연마가 크게 억제되었고, 높은 연마 선택비를 구현 할 수 있었다.; In this paper, we have studied Si3N4 to poly-Si high selectivity ceria slurry which can be used for 3D-Nand flash poly stop CMP process and HKMG POP (poly open polishing) process. Since high selectivity slurries have been studied mainly on silica based slurries, we have tried to find out what mechanisms of ceria-based slurries will act on the selectivity To obtain a high selectivity, DAHP, an anionic ion, and PEO, a non-ionic polymer, were added to 1wt% Ceria slurry and the concentration of the two chemicals was optimized respectively, and then Si3N4 to poly-Si = 43:1 selectivity was gained. Also, the scratch phenomenon found in conventional ceria slurry disappeared by adding two chemicals. To confirm how each chemical affects the selectivity Adsorption test (FT-IR, Zeta potential, Contact Angle), surface analysis (OM, SEM, AFM), and surface element analysis (XPS) were performed DAHP and PEO adjust selectivity by controlling the adsorption characteristics between Ceria particles and SI3N4 or poly-Si films, and they did not chemically change the polishing mechanism. Both DAHP and PEO showed the effect of improving the selectivity even when they were individually inserted. However, when the two were put together, the synergy effect significantly suppressed the poly-Si polishing and achieving a high polishing selectivity.