The semiconductor
industry continues to shrink the device sizes
while applying more complex shapes and using diverse materials, which
requires parallel improvements in the quality of ultrapure reagents.
The need for ultrapure reagents has led to ever-higher demands for
the performance of analytical instruments used to detect ultratrace
impurities. In this study, nonvolatile impurities in ultrapure reagents
were quantified using a scanning mobility particle sizer (SMPS). The
performances of three different sample introduction systems, i.e.,
an electrospray (ES), an aerosol generator with a heating chamber
and a Nafion desolvation membrane (NB-II), and a MicroMist nebulizer
with a heated cyclonic spray chamber and a three-stage Peltier-cooled
desolvation system (MM-APEX), were evaluated for the lower limit of
detection of a SMPS. The MM-APEX equipped with the SMPS was able to
detect NaCl additives at a concentration of 100 parts per trillion
(ppt, ng/L) in ultrapure water, which was approximately 10
4
- and 10
2
-fold lower than those of ES and NB-II, respectively.
The practical application of MM-APEX with the SMPS for commercial
isopropanol samples was also studied. The results clearly demonstrate
that the impurity concentrations presented by the NaCl-equivalent
concentrations among different sources of isopropanol were at the
ppt to parts-to-billion (ppb) scale. The SMPS system equipped with
MM-APEX is capable of recognizing impurities with concentrations ranging
from tens ppt to thousands of parts per million (ppm), which is beneficial
for an ultratrace analysis of nonvolatile impurities in semiconductor
process chemicals.