| Summary: | 碩士 === 國立中興大學 === 材料工程學研究所 === 84 === In this study, we report a new set of experimentalresults on
oxygen precipitation carried out usingCzochralski silicon wafers
: a low-high two stepheat-treatment in N2 ambient was employed :
thefirst step heat-treatment low temperature ( at 450℃ for 0 -
1024 hours ) is for SiO2 precipitatenucleation and the high
temperature step ( at 1000℃ for 0 - 40 hours ) is for
precipitate growth. Theoxygen precipitation rate is monitored by
measuring the interstitial oxygen concentration in the
siliconwafer. Two precipitation retardation phenomena
wereobserved on wafers that received prolonged nucleationheart-
treatment. First retardation peak whick is morepronounced
occurred on the wafers which received l6h - 64 h at 450 ℃ with
the microdefect features observed in this study , we believed
that thisretardation phenomenon reported by Tan and Kung on 750
℃ - 1050 ℃ two-step heat-treatment testSecond retardation peak
occurred on the wafersheat-treated at 450 ℃for 512 h or longer.
Thisretardation peak is relatively weak. And we still notquiet
understand the mechanism of this retardationphenomenon. A set
of idential wafers were preheated at 1200 ℃ / 1 h in dry N2,
prior to the two-step heat-treatment described above. The short
hightemperature pre-heat-treated wafers enhanced theoxygen
precipitation rate and also revealed thesimiliar retardation
phenomena described above, wereport the microdefect features and
FT/IR spectra onthe final stage of two-step heat-treatments.
Aprofound model is still needed to cover all thephenomena
observed.
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