碱性条件下铝CMP的机理分析及实验优化

依据铝的电化学腐蚀特性,阐明了碱性条件下铝化学机械抛光(CMP)的机理。由于铝的硬度较低,在抛光过程中容易产生微划伤等缺陷,因此首先探索出适宜铝化学机械抛光的低压条件(4 psi,1 psi=6.895 kPa)。此外,提出两步抛光的方法,在抛光初期采用压力4 psi,抛光液由质量分数为40%的纳米级硅溶胶与去离子水(DIW)以体积比1∶1配制,氧化剂(H2O2)体积分数为1.5%,FA/O I型表面活性剂体积分数为1%,调节FA/OⅡ型螯合剂pH值为11.0,获得了较高的铝去除速率(341 nm/min)。在抛光后期采用低压1.45 psi,抛光液主要成分为体积分数5%的FA/O表面活性剂,并在较大体积流量(300 mL/min)的条件下进行抛光,充分利用表面活性剂的作用,对实验方案进行优化。采用优化后的实验方案,铝表面的划伤和缺陷显著减少。

Mechanism Analysis and Experimental Optimization of Al CMP Under Alkaline Condition

According to the electrochemical corrosion characteristics of aluminum,the mechanism of chemical mechanical polishing(CMP) under alkaline condition was analyzed.Aluminum has low hardness,and it is easy to generate micro-scratches and other defects in polishing.So the appropriate low pressure condition(4 psi,1 psi=6.895 kPa) for aluminum CMP was explored firstly.In addition,the method of two steps polis-hing was proposed.In the early period of poli-shing,when the pressure is 4 psi,the polishing slurry consists of silica sol(the mass fraction of which is 40% and abrasive size is nm level) and deionized water(DIW) with the volume ratio of 1∶1.Besides that,the volume ratio of the oxidant(H2O2) is 1.5%,the volume ratio of FA/O I-type surfactant is 1%,the pH value adjusted by FA/O II-type chelating agent is 11.0.Then,higher aluminum removal rate(341 nm/min) was acquired.In the later polishing period,with lower pressure 1.45 psi,the main composition of the slurry is FA/O surfactant with the volume ratio of 5%,and the polishing volume flow is large(300 mL/min).The experimental program was optimized with the surfactant fully utilized.After applying the optimization scheme,the defects and scratches at the surface of aluminum are reduced significantly.