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 SO4
2− 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).