Environmentally-benign cleaning for giga DRAM using electrolyzed water
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Environmentally-benign cleaning for giga DRAM using electrolyzed water Kunkul Ryoo and Byeongdoo Kang Department of Advanced Materials Engineering Soonchunhyang University, Eupnae-ri, Shinchang-myun Asan, Chungnam, Korea
ABSTRACT A present semiconductor cleaning technology is based upon RCA cleaning technology which consumes vast amounts of chemicals and ultra pure water(UPW) and is the high temperature process. Therefore, this technology gives rise to the many environmental issues, and some alternatives such as functional water cleaning are being studied. The electrolyzed water was generated by an electrolysis system which consists of anode, cathode, and middle chambers. Oxidative water and reductive water were obtained in anode and cathode chambers, respectively. In case of NH4Cl electrolyte, the oxidation-reduction potential and pH for anode water(AW) and cathode water(CW) were measured to be +1050mV and 4.8, and -750mV and 10.0, respectively. AW and CW were deteriorated after electrolyzed, but maintained their characteristics for more than 40 minutes sufficiently enough for cleaning. Their deterioration was correlated with CO2 concentration changes dissolved from air. It was known that AW was effective for Cu removal, while CW was more effective for Fe removal. The particle distributions after various particle removal processes maintained the same pattern. In this work, RCA consumed about 9 chemicals, while EW did only HCl electrolyte or 600 NH4Cl electrolyte. It was hence concluded that EW cleaning 400 technology would be very effective for eliminating environment, safety, and health(ESH) issues in the next generation semiconductor manufacturing.
INTRODUCTION The cleaning process takes an important role technically and economically in semiconductor manufacturing processes. Ultraclean wafer surface must be achieved in terms of particle free, metallic impurity free, organic free, moisture free, native oxide free, surface micro-roughness free, charge-up free, and hydrogen-terminated.[1-3] Many wet cleaning processes that aim to eliminate contaminants have been developed based on RCA cleaning.[4-5] As the diameter of Si wafers increases and the semiconductor devices shrinks, the number of cleaning process units increases so that the amount of chemicals and ultra pure water(UPW) consumed in RCA cleaning process increases drastically and production cost increases as well. Therefore RCA cleaning technology gives the economic and environmental issues, which would be expected to be considered mandatorily in near future. In order to resolve these issues, advanced cleaning methods have been studied applying functional water such as the hydrogenated ultra pure water(H2-UPW)[6], ozonized water(O3-UPW)[78], and electrolyzed water.[9-11] It is expected that application of EW would increase in semiconductor manufacturing because the characteristics of EW are able to be controlled more easily and accurately than other functional waters.
EXPERIMENTAL DETAILS EW generation apparatus used in this study is shown schematically in
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