蓝宝石衬底CMP中氧化硅磨粒粒度分布对抛光液体系性能影响研究

目的 化学机械抛光(CMP)包含化学腐蚀和机械磨削两方面，抛光液pH、磨粒粒径和浓度等因素均会不同程度地影响其化学腐蚀和机械磨削能力，从而影响抛光效果。方法 采用30~150 nm连续粒径磨粒抛光液、120 nm均一粒径磨粒抛光液、50 nm和120 nm配制而成的混合粒径磨粒抛光液，分别对蓝宝石衬底晶圆进行循环CMP实验，研究CMP过程中抛光液体系的变化。结果 连续粒径磨粒抛光液中磨粒大规模团聚，满足高材料去除率的抛光时间仅有4 h，抛光后的晶圆表面粗糙度为0.665 nm;均一粒径磨粒抛光液中磨粒稳定，无团聚现象，抛光9 h内材料去除率较连续粒径磨粒抛光液高94.7%，能至少维持高材料去除率18 h，抛光后的晶圆表面粗糙度为0.204 nm;混合粒径磨粒抛光液初始状态下磨粒稳定性较高，抛光9 h内材料去除率较连续粒径磨粒抛光液高114.8%，之后磨粒出现小规模团聚现象，后9 h材料去除率仅为均一粒径磨粒抛光液的59.6%，18 h内材料去除率仅为均一粒径磨粒抛光液的87.7%，但抛光后的晶圆表面粗糙度为0.151 nm。结论 一定时间内追求较高的材料去除率和较好的晶圆表面粗糙度选用混合粒径磨粒抛光液，但需要长时间CMP使用均一粒径磨粒抛光液更适合，因此，在工业生产中需要根据生产要求配合使用混合粒径磨粒抛光液和均一粒径磨粒抛光液。

Effect of Silica Abrasive Particle Size Distribution on the Properties of Polishing Slurry System in Sapphire Substrate CMP

Chemical mechanical polishing (CMP) includes chemical corrosion and mechanical grinding. Factors such as pH of polishing slurry, particle size and concentration of abrasive particles will affect its chemical corrosion and mechanical grinding ability to varying degrees, thus affecting the polishing effect. UNIPOL-1200S automatic grinding and polishing machine and SUBA-600 polishing pad were used in the experiment to conduct the cyclic polishing experiment on the 2-inch sapphire substrate wafer in the C-direction of single crystal. 30-150 nm continuous particle size abrasive polishing slurry, 120 nm uniform particle size abrasive polishing slurry, 50 nm uniform particle size nano silica and 120 nm uniform particle size nano silica were mixed according to 4:6 (volume ratio) to form a mixed particle size abrasive polishing slurry, and 2% chelating agent (citrate), 2% oxidant (hydrogen peroxide) and 0.1% surfactant (fatty alcohol polyoxyethylene ether) were added to each type of polishing slurry. The flow rate of polishing slurry was 100 mL/min. The sapphire substrate wafer rotated clockwise at 30 rpm. The polishing pad rotated counterclockwise at 60 r/min. The load was 15.5 kg. Three types of polishing slurry were used to conduct cyclic CMP experiments on sapphire substrate wafers to study the changes of polishing slurry system during CMP process. In the continuous particle size abrasive polishing slurry, the abrasive particles aggregated on a large scale, and the polishing time required for high material removal rate was only 4 hours. The surface roughness of the polished wafer was 0.665 nm. The abrasive particles in the polishing slurry with uniform particle size were stable without agglomeration. The material removal rate within 9 hours of polishing was 94.7%, higher than that of the continuous particle size abrasive polishing slurry, which could maintain a high value for at least 18 hours. The surface roughness of the polished wafer was 0.204 nm. In the initial state of mixed particle size abrasive polishing slurry, the stability of the abrasive particles was relatively high. Within 9 hours of polishing, the material removal rate was 114.8%, higher than that of continuous particle size abrasive polishing slurry. Afterwards, the abrasive particles exhibited small-scale agglomeration, and the material removal rate was only 59.6% of that of uniform particle size abrasive polishing slurry after 9 hours. Within 18 hours, the material removal rate was only 87.7% of that of uniform particle size abrasive polishing slurry, but the surface roughness of the polished wafer was 0.151 nm. The free flowing small abrasive particles in the mixed particle size polishing slurry can wash and impact the remaining small protrusions and micro defects on the wafer surface, and can better fill the grooves and pits on the wafer surface, promoting more uniform grinding of the wafer surface. The uniformity of material removal is better than that of other two types of polishing slurry. In pursuit of high material removal rate and good wafer surface roughness for a certain period of time, mixed particle size abrasive polishing slurry is chosen, but it is more suitable to use uniform particle size abrasive polishing slurry for CMP over a long period of time. Therefore, in industrial production, mixed particle size abrasive polishing slurry and uniform particle size abrasive polishing slurry need to be used in combination according to production requirements.