基于聚氨酯垫的4H-SiC单晶衬底研磨性质研究

Grinding Properties of 4H-SiC Single Crystal Substrate Using Polyurethane Pad

4H-SiC单晶是典型的难加工材料,研磨加工后表面损伤的密度和深度直接影响后续抛光工序的质量和效率。采用普通铸铁盘研磨工艺会导致晶圆表面划痕多、边缘破片以及去除率不稳定等问题。本实验采用聚氨酯垫研磨工艺,减少研磨划痕,提高了研磨后的表面质量,实现了SiC衬底的精准研磨。通过改变金刚石磨料粒度、磨抛盘转速、研磨压强进行SiC衬底的研磨实验,探究最优工艺参数及各条件对研磨效果的影响规律。实验结果表明:随着研磨盘速度增大,研磨的去除率增大,其对应的粗糙度先降低后升高;增大金刚石磨料的粒径会增大研磨的去除率,但研磨后表面粗糙度也会持续增大;通过增加研磨压强,材料的去除率和表面粗糙度都将增加,但去除率增加的速率由快变慢,而粗糙度增加的速率逐渐加快。综合考虑,采用聚氨酯垫研磨时,较优研磨工艺参数为:金刚石研磨液浓度为3%,金刚石粒径为1μm,研磨液供给速度为5 mL/min,研磨压强为47 kPa,研磨转速35 r/min。该工艺下SiC材料的去除率为0.7μm/h,研磨后SiC衬底的表面粗糙度为24 nm。

4H-SiC single crystal is a typically difficult material to process.The density and depth of surface damage after grinding directly affect the quality and efficiency of subsequent polishing operations.Grinding using traditional cast iron discs always results in significant scratches,broken edges,and an unstable removal rate for SiC substrates.In this experiment,a polyurethane pad was used to reduce post-grinding scratches,improve post-grinding surface quality,and achieve precise grinding of SiC substrates.The grinding experiments were carried out by changing the particle size of diamond abrasives,the rotating speed of discs,and the pressure added to the carrier disc.Our results show that the removal rate of SiC substrates increases with the increase of the rotating speed of discs,and the corresponding surface roughness after grinding decreases first and then increases.The removal rate of the SiC substrate increases with the increase of the particle size of diamond abrasives,but the surface roughness continues to increase.As the pressure added to the carrier disc increases,both removal rate and surface roughness after grinding increase,however,the increasing rate for the former would decrease,and the increasing rate for the latter would increase.Based on the experiment results,the optimal grinding conditions are as follows:the mass ratio of diamond in the slurry is 3%,the particle size of diamond abrasives is 1μm,the supply rate for slurry is 5 mL/min,the pressure added on the carrier disc is 47 kPa,and the rotating speed of the disc is 35 r/min.Under this condition,a removal rate of 0.7μm/h and surface roughness after grinding of 24 nm are achieved.