소자 분리 공정용 화학적 기계적 연마 슬러리 특성에서의 유기 첨가제 영향 연구

Abstract

With the shrinkage of device design rule, global planarization using c hemical mechanical polishing (CMP) becomes the most important technology in ultra large scale integrated (ULSI) device fabrication. The role of STI (Shallow Trench Isolation) CMP removes silicon oxide on silicon nitride to make field oxide. In STI CMP process, the use of slurry with low removal selectivity results in change of field oxide thickness and decrease of over-polishing margin. To overcome these disadvantages, organic additives have been used to increase the removal selectivity by changing surface potential of the wafer. The effect of organic additives in slurry on STI CMP performance has not been reported yet. The purposes of this research were to measure surface potential of the wafer and effects of organic additives on removal selectivity. In this study, poly(acrylic acid) was investigated as an organic additive. In this study, glutaric acid, acrylic acid, and poly(acrylic acid) were investigated as the organic additives. Zeta potential was measured by using electrophoretic light scattering technique, and additive adsorption was monitored by FT-IR. Surface of wafers was characterized by FESEM. The removal rate of wafer was evaluated by using ellipsometry. The zeta potential of the wafer was measured according to pH in solution with or without additives. glutaric acid did not change the zeta potential of silicon nitride surface. However, when acrylic acid or poly(acrylic acid) was added, silicon nitride wafer showed the more negative zeta potential value. It was believed that zeta potential of silicon nitride decreased due to the adsorption of poly(acrylic acid) on wafer surface, which was confirmed by FT-IR analysis. The zeta potential of the wafer was measured by changing of poly(acrylic acid) concentrations...