单晶碳化硅晶片高效超精密抛光工艺

High-productively ultraprecise polishing technique of single crystal SiC wafer

为改善现有碳化硅抛光方法存在的效率低、有污染、损伤大等问题,提出采用机械研磨与光催化辅助化学机械抛光组合工艺抛光单晶碳化硅晶片.光催化辅助化学机械抛光利用纳米二氧化钛在紫外光照射下生成羟基自由基的强氧化作用原子级去除碳化硅.通过L9(33)正交试验研制光催化辅助化学机械抛光抛光液,采用对碳化硅晶片表面粗糙度跟踪检测的方法确定优化加工工艺.甲基紫有机显色剂静态氧化试验结果表明:光催化剂对抛光液氧化性的影响最大,其次是电子俘获剂,再次是分散剂;较好的抛光液配方为二氧化钛0.5 g獉L-1、过氧化氢1.5 mol獉L-1、六偏磷酸钠0.1 g獉L-1.确定的优化抛光工艺为:采用5μm和2μm金刚石微粉分别研磨单晶碳化硅晶片30 min,材料去除率分别为8.72μm/h和4.56μm/h;然后采用光催化辅助化学机械抛光单晶碳化硅去除机械研磨带来的损伤,粗抛光选用0.5μm氧化铝微粉抛光60 min,精抛光选用0.05μm氧化铝微粉抛光50 min,粗抛光和精抛光的材料去除率分别为1.81μm/h和1.03μm/h.用该工艺抛光单晶碳化硅,获得的表面粗糙度约为0.47 nm,基本能满足单晶碳化硅高效、超光滑、低损伤的抛光要求.

A smoothing method for single crystal silicon carbide(SiC)especially with the combination of mechanical lapping and photocatalysis-assisted chemical mechanical polishing(PCMP)is proposed to solve the problems of traditional polishing methods,such as low efficiency,serious pollution,great damage,etc,by which the atomic smoothing of SiC wafer is removed by the powerful oxidability of UV photo-excited hydroxyl radical on nano TiO 2 particles.A orthogonal experiment(L 9(3 3))was first designed to develop efficient slurries for PCMP,and subsequently the optimized processing technology was obtained by method of detecting the surface roughness of silicon carbide wafer in the polishing process.The results show that the catalyst has greatest effect on the oxidability of slurry,and then is the electronic capture agent and the dispersing agent.The preferable slurry formula is TiO 2(0.5g·L^-1),H2O2(1.5mol·L^-1)and(Na2PO3)6(0.1g·L^-1).The proper polishing technique is the lapping SiC for 30 min with 5μm and 2μm diamond powders first,the material removal rate(R MRR)is 8.72μm/h and 4.56μm/h,respectively.And then is the removing the damage caused by mechanical lapping with PCMP,0.5μm alumina powder was used for rough polishing for 50 min,and 0.05μm alumina powder for fine polishing for 60 min in the polishing process,of which the R MRR is 1.81μm/h and 1.03μm/h,respectively.The best surface roughness R a with the proper progress can be reduced to about 0.47 nm,which may satisfy the requirements of high efficiency,ultra smooth and low damage for polishing single crystal silicon carbide.