DETERMINATION OF TRACE IMPURITIES ON SILICON-WAFER SURFACE BY ISOTOPE-DILUTION ANALYSIS USING ELECTROTHERMAL VAPORIZATION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY
M. Komoda et al., DETERMINATION OF TRACE IMPURITIES ON SILICON-WAFER SURFACE BY ISOTOPE-DILUTION ANALYSIS USING ELECTROTHERMAL VAPORIZATION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY, Analytical sciences, 12(1), 1996, pp. 21-25
The feasibility of coupling the isotope dilution (ID) analysis and the
electrothermal vaporization/inductively coupled plasma mass spectrome
try (ETV-ICP-MS) was studied in order to determine trace impurities on
Si-wafer surface precisely. The precision of the isotope ratio measur
ement was investigated for single element and sequential two-element d
etermination by ETV-ICP-MS. In the case of the single element determin
ation, 0.1, ng ml(-1) of Cu in a 20 mu l sample could be measured with
relative standard deviation (RSD) less than 6%, and 1 ng ml(-1) of Cu
and Zn could be measured with RSD less than 5% in the sequential two-
element determination. Coupling of ID and ETV-ICP-MS was applied to de
termine trace impurities of Cu, Zn and Pb, which were collected by etc
hing a Si-wa fer surface with a vapor mixture of nitric acid and hydro
fluoric acid. The amount of etching solution obtained from one Si-wafe
r was about 200 mu l. Those impurities were determined at 3x10(8) - 8.
7x10(9) atoms cm(-2) with an RSD of 2% by ID-ETV-ICP-MS. The amount of
Cu on the Si-wafer surface was also determined by calibration method
with ETV-ICP-MS and by graphite furnace atomic absorption spectrometry
. The results obtained by these three different methods agreed well wi
th each other.