Experimental and theoretical analysis of single-sided and double-sided chemical mechanical polishing of sapphire wafers

Sapphire is widely used as a new generation of optoelectronic chips. In this article, single-sided chemical mechanical polishing (SS-CMP) and double-sided chemical mechanical polishing (DS-CMP) were conducted polishing experiments on sapphire wafers. Polishing pressure, relative rotational speed, and polishing time were investigated on material removal rate (MRR), surface roughness (SR), and parallelism of sapphire wafers under the two methods. The results demonstrate both MRR and SR of DS-CMP are significantly better than SS-CMP under the same parameters. Sapphire DS-CMP can obtain a relatively stable average MRR increment of 14.016 nm/min comparing to SS-CMP and can also obtain better surface quality when subjected to greater polishing pressure. Additionally, the parallelism after SS-CMP is about 3 times that of DS-CMP under one-time processing. Finally, sapphire CMP material removal equations are established empirically and theoretically to demonstrate the exponential equation of nonlinear relationship is more suitable for the material removal of sapphire CMP, and the mean error between the theoretical and experimental results of SS-CMP and DS-CMP is within 10%, providing a quantitative and efficient solution for manufacturing sapphire wafers.

Automated summary

This article investigates the effects of single-sided chemical mechanical polishing (SS-CMP) and double-sided chemical mechanical polishing (DS-CMP) on sapphire wafers. The results show that DS-CMP achieves better material removal rate and surface roughness compared to SS-CMP, and it can also achieve better surface quality under higher polishing pressure. Additionally, the parallelism of DS-CMP is superior to SS-CMP.