Electrolyzed water as the novel cleaning media in ultra-large-scale integration and liquid crystal display manufacturing

Electrolyzed water (EW) has been applied to the wet cleaning in ultra-large-scale integration (ULSI) and liquid-crystal display (LCD) manufacturing processes. For supplying ultrapure EW as cleaning solutions in this field, an electrolytic cell composed of three chambers is developed. The cell generates EW featuring wide ranges of pH and oxidation-reduction potential with quite high purity similar to that of ultrapure water (UPW). EW generated by the cell has demonstrated the excellent abilities in removing contaminants from both ULSI and LCD substrates, despite the extremely low concentrations of chemicals. By dipping into anode water at room temperature, Cu above 10(12) atoms/cm(2) adhered on a Si wafer has been removed to below 10(10) atoms/cm(2), which meets the acceptable cleanliness in current ULSI device manufacturing. This anode water was generated from 10 mM HCl, which is less than 1/100 of chemicals compared with the conventional cleaning solution including several percentage points of each HCl and H2O2 and usually used in 60-70 degrees C, The mechanism of Cu removal by anode water has been clarified that the oxidative potential of ClO- produced by anodic oxidation from Cl- and acidic pH are the keys of the cleaning ability. Cathode water demonstrates excellent particle removal abilities. In the cleaning process after chemical mechanical polishing (CMP), cathode water removes SiO2 particles from above 20 000 to below 100. Particles adhered on an LCD substrate have also been removed efficiently by cathode water. It is presumed that reductive potential and increased cavitation, when used with ultrasonic wave irradiation, are the essential factors for the cleaning ability of cathode water. EW cleaning is the method which produces the necessary amount of effective component on site; thus, it can reduce chemicals and UPW consumption drastically. The EW cleaning method is highly expected not only to improve efficiency of surface cleaning but also to help the industrial manufacturing activities harmonize the protection of the global environment.