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

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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.