To reduce the consumption of chemicals and ultra pure water (UPW) in cleaning processes used in device manufacturing, we have developed wet processes that use electrolytic ionized water (EIW), which is generated by the electrolysis of a diluted electrolyte solution or UPW. EIW can be controlled for wide ranges of pH and oxidation-reduction potential. Anode EIW with diluted electrolyte, which has high oxidation potential, can remove metallic contamination such as Cu and Fe on Si surfaces. EIW contains less than 1/100 of the amount of chemicals contained in conventional cleaning solutions, thus drastically reduces chemical consumption in wet processes. Moreover, electrolyzed UPW can be used as a substitute for conventional UPW to achieve better rinsing characteristics. Electrolyzed UPW reduces the level of residual SO42− ions after SPM cleaning more efficiently than conventional UPW. Thus the amount of rinse water needed is reduce to 1/6 that of the conventional UPW rinse.
We also developed a method for analyzing remaining metallic contamination and residual ions in deep-submicron-diameter holes with high aspect ratios. The method is based on conventional atomic absorption spectrometry (AAS), and uses device patterns with high density contact holes. With this method, metallic (Fe) contamination on the order of 1010 atoms/cm2 can be easily analyzed inside 0.1 μm-diameter holes with an aspect ratio of 10. The residual ions in the fine holes can also be detected by thermal desorption spectroscopy (TDS).