Electrostatically Modified Ceria Particles for Restraining of Remaining Particle and Scratch in Shallow Trench Isolation (STI) Chemical Mechanical Planarization (CMP) Process

Abstract

본 연구에서는 초고집적 반도체 공정 중, 소자 분리 기술인 shallowtrench isolation (STI) chemical mechanical planarization (CMP)에서 발생되는 scratch를 줄이기 위한 목적으로 슬러리의 분산안정성 향상을 위해citric acid를 첨가하여 정전기적으로 개질된 ceria 입자에 대하여 연구하였다. ceria 슬러리의 분산안전성은 poly(methyl methacrylate)와 Citric acid의 co-adsorption에 의하여 크게 증가하였다. Citric acid는 ceria 입자의 표면에 흡착된 PMAA의 methyl methacrylate side chain 사이의 반발력에의하여 형성된 vacancy에 흡착하며, 이러한 citric acid와 PMAA의co-adsorption은 ceria 입자의 표면전하를 증가시켜 분산안정성을 향상시켰다. Citric acid의 효과에 의하여 향상된 분산안정성은 ceria 슬러리의 입도분포와 점도로 확인되었다. PMAA와 citric acid를 동시에 첨가하여 제조한슬러리는 ceria 입자들의 plasma-enhanced tetraethylorthosilicate(PETEOS) 막에 대한 흡착과 입자들 간의 응집을 억제하여 CMP 평가에서 microscratch와 remaining particle의 감소를 내타내었다.; An attempt was made to prevent the formation of scratch on the wafer surface during the shallow trench isolation (STI) chemical mechanical planarization (CMP) process by improving the dispersion stability of ceria slurry. The dispersion stability of ceria slurry was distinctively increased by co-adsorption of poly(methyl methacrylate) (PMAA) and citric acid on the ceria particle surface. Citric acid is adsorbed on the vacancy which is spontaneously formed due to ionic repulsive forces between methyl methacrylate side chains of PMAA although PMAA is adsorbed on the ceria particle surface. The co-adsorpiton of PMAA and citric acid increases the surface potential of ceria particle, which results in the improved dispersion stability. The improved dispersion stability induced by the synergetic effect of citric acid was confirmed by particle size distribution, and viscosity of ceria slurry. In CMP field evaluation of ceria slurry prepared with both PMAA and citric acid, the remaining particle and microscratches were successfully reduced by control of the agglomerated large particle and particle adhesion on the plasma-enhanced tetraethylorthosilicate (PETEOS) film surface.