酸性环境下GaN晶圆的化学机械抛光工艺研究

The Chemical Mechanical Polishing of C-plane Free-standing GaN Wafers with Acidic Slurry

本文详细研究了4英寸自支撑GaN晶圆的化学机械抛光(CMP)工艺。使用硅溶胶抛光液,以NaClO为氧化剂,详细研究了不同工艺参数,包括压力、抛光盘转速、抛光液流量、NaClO浓度和抛光液p H值对GaN CMP工艺的材料去除率(MRR)和表面粗糙度(Sa)的影响。研究发现,无论是影响化学作用的因素,还是影响机械作用的因素,都对MRR有着极大的影响。在优化的工艺条件下(压力为50 kPa、抛光头转速为60 rpm、抛光盘转速为100 rpm、流量为40 mL/min、抛光液pH为4.0、氧化剂浓度为3 vol.%),最大材料去除率为1.07μm/h。在10μm×10μm的区域内,抛光后的平均表面粗糙度为0.109 nm。

The chemical mechanical polishing(CMP) process of 4 inch free-standing c-plane GaN wafers has been studied. Effect of processing parameters,such as oxidizer(NaClO) concentration, flow rate, polishing pressure, plate speed, and pH of the slurry, on the material removal rate(MRR) and surface quality(roughness) have been studied in detail by using colloidal silica based polishing slurry. It has been found that the improvement of chemical action and mechanical action can greatly increase MRR. The maximum material removal rate has been found to be 1.03 μm/h under conditions of 50 kPa pressure, 60 rpm head speed, 100 rpm plate speed, flow rate 40 ml/min, slurry pH 4.0, and 3 vol.% oxidizer concentration. Average surface area roughness(Sa) of 0.109 nm over scanning area of 10μm×10 μm has been achieved on polished Ga-faced.