纳米CeO2颗粒的制备及其化学机械抛光性能研究

以硝酸铈和六亚甲基四胺为原料制备出不同粒径的纳米CeO2粉体颗粒,将纳米CeO2粉体配制成抛光液并用于砷化镓晶片的化学机械抛光.结果表明,不同尺寸的纳米磨料具有不同的抛光效果,采用粒度8 nm的CeO2磨料抛光后微观表面粗糙度最低(0.740 nm),采用粒度小于或大于8 nm的CeO2磨料抛光后其表面粗糙度值均较高.通过简化的固-固接触模型分析,认为当粒度过小时,磨料难以穿透软质层,表现为化学抛光为主,表面凹坑较多,表面粗糙度较高;当粒度大于一定值时,随着磨料粒度增加,嵌入基体部分的深度加大,使得粗糙度出现上升趋势.提出当磨料嵌入晶片表面的最大深度等于或接近于软质层厚度时,在理论上应具有最佳的抛光效果.

Preparation of CeO2 Nanoparticles and Their Chemical Mechanical Polishing as Abrasives

CeO2 nanoparticles were prepared using cerium nitrate and hexamethylenetetramine as starting materials, and the prepared powders were collocated into polishing slurry for chemical mechanical polishing of GaAs wafer. Various size of nanoparticles had the different polishing effect, of which the 8 nm particles exhibited the best polishing effect with the lowest surface roughness 0. 740 nm, and those smaller or bigger than such size got higher surface roughness. By taking simplified solid-solid contact models into consideration, the chemical polishing manner played a dominant role and resulted the worse surface performance because it is difficult for abrasives to penetrate into the soft layer if the particles were too small. On the contrary, when the particles were larger than certain size, the surface roughness increased because the depth which particles embeded into martrix increased. The best polishing can be obtained while the depth of particles indented into wafer surface was equal to or near to the thickness of soft layer.