DEVELOPMENT OF ULTRAPRECISION CLEANING SYSTEM USING HIGH-VELOCITY SHEAR FLOW AND ELECTROCHEMICAL ETCHING PROCESS IN ULTRAPRE WATER

提出了一种利用超纯水沿被清洗表面高速剪切流去除颗粒污染的超精密清洗新方法。搭建了超纯水高速剪切流实验装置，对直径为0.4 ~ 7.0μm的硅颗粒预污染的硅片表面进行了超纯水清洗实验。并对沉积在硅片上的非晶硅、氧化铟锡（ITO）、tin和有机化合物进行了清洗。结果表明，完全去除基质上的污染颗粒是可能的。此外，还进行了空气中的净化过程，并证实了空气中的过程比超纯水中的过程更有效，因为空气中的过程比超纯水中的过程需要更少的超纯水。作为第二步，我们提出了另一种新的清洁工艺，利用超纯水中OH^-离子诱导的金属电化学蚀刻工艺去除金属污染物。为了增加超纯水中OH^-离子的密度，我们制作了羧基化石墨电极的原型，因为羧基功能具有将水分子解离成H+和OH^-离子的能力。以羧基化石墨电极为阴极，待清洗衬底为阳极，观察H+和OH^-离子诱导的电解电流，并将阳极衬底上的Cu板蚀刻掉。从这些结果中，我们得出结论，我们新提出的清洁工艺对于完美去除基材上的颗粒和金属污染物是有用的。

A new method of ultraprecision cleaning process for removing the particle contamination using high-velocity shear flow of ultrapure water along the surface to be cleaned was proposed. We constructed a new experimental apparatus which can supply high-velocity shear flow of ultrapure water, and performed cleaning processes in ultrapure water of Si wafer surfaces which are pre-contaminated by silica particles whose diameters are 0.4〜7.0μm. Cleaning processes of amorphous Si, ITO (indium tin oxide), TIN and organic compound deposited on Si wafer were also performed. It was confirmed that perfect removal of contaminated particles on the substrates are possible. In addition, cleaning processes in the air were also conducted, and it was confirmed that the processes in the air are more effective than the one in the ultrapure water, since the processes in the air require smaller amount of ultrapure water than the ones in ultrapure water.As the second step, we proposed another new cleaning process for removing metal contaminations applying electrochemical etching process of metal induced by OH^-ions in ultrapure water. In order to increase the density of the OH^-ions in ultrapure water, we prototyped carboxylated graphite electrodes, since the carboxyl function has the ability of dissociation of the water molecules into H+ and OH^-ions. Applying the carboxylated graphite electrodes as cathodes and the substrates to be cleaned as anodes, electrolysis current induced by H+ and OH^-ions was observed, and Cu plate on the anode substrates was etched off. From these results, we concluded that our newly proposed cleaning processes are useful for perfect removal of contaminations of particles and metal on substrates.