A Characterization of New Cleaning Method Using Electrolytic Ionized Water for Poly Si CMP Process
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A CHARACTERIZATION OF NEW CLEANING METHOD USING ELECTROLYTIC IONIZED WATER FOR POLY Si CMP PROCESS N.Miyashita1,2 , Shin-ichiro Uekusa S.Seta3, T.Nishioka3 1 Meiji Univ., Dept of Electrical and Electronic Engineering, Kawasaki Japan. 2 Toshiba Co, Semiconductor Company 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8522, Yokohama Japan, [email protected] 3 Mechanical Systems Laboratory, Corporate R&D Center, Toshiba Corporation 1, KomukaiToshiba-cho, Saiwai-ku, Kawasaki Japan. ABSTRACT A Trench isolation technology has been developed and applied to high-speed bipolar LSI production. In general, the wafer surface after a conventional ploy-Si Chemical-Mechanical-Polishing (CMP) is contaminated with silica particles and chemical impurities. These contaminations produce some unexpected patterns and crystal defects in the wafer surface layer after oxidation. It is difficult to remove them by the conventional cleaning techniques. Therefore, we have established the new post CMP cleaning method, using the electrolytic ionized water containing chemical additive of a small quantity. The anode water has the cleaning effect for the metallic and organic contaminations, and the cathode water has the removing effect for the particles and the etching effect for the poly-Si surface. For this new cleaning process, it is important to avoid the chemical mechanical damages on the surface and to control the surface roughness. Our experimental work has been focused on the large numbers of the remaining particle and the surface roughness using a particle counter and an atomic force microscopy (AFM). We herein report the properties of the electrolytic ionized water and the examined results of poly-Si surface after CMP process. It was found that the electrolytic ionized water is effective for surface control, and the new cleaning process is useful for CMP process. INTRODUCTION The wafer surface after conventional CMP process is contaminated with the silica particles, the organic and the metallic impurities. The new cleaning method, using the electrolytic ionized water containing chemical additive of a small quantity, removed the contamination. The anode M5.7.1
water included ClO- ion of strong acidity/high ORP and the cathode water of the strong alkalinity /low ORP included NH3- ion. The anode water had the cleaning effects for the metallic and the organic contaminations. The cathode water had the removing effect for the particles and the organic film coated on the wafer surface. In this process, over etching had been caused by over cleaning in the cathode water process. During cathode water cleaning process, over-etching is necessary to remove all silica particles including a part of the organic film. For this new cleaning process, it is important to avoid the chemical and the mechanical damages on the surface and to control the surface roughness. EXPERIMENTAL The electrolytic ionized water generator could generate the anode water including ClO- ion of strong acidity/ high ORP and the cathode water of the strong alkaline/ low OR
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