Highly Sensitive and Accurate Infrared Absorption Measurement of Carbon Concentration in Si Crystal

Abstract

Infrared absorption (IR) measurement of carbon concentration ([C]) in silicon crystal around 1015 cm-3 was examined. Measurement of 605 cm-1 absorption was difficult due to the overlapping double phonon peak. Absorption of CiOi complexes at 862 cm-1 induced by electron irradiation was a good measure of [C] below 1015 cm-3. Also, electron irradiation was successfully utilized to reduce the substitutional carbon concentration in the reference sample by nearly one order of magnitude. Second harmonic vibrational mode at 1206 cm-1 was observed in samples with [C] down to 1016 cm-3. One mm thick samples and commercial wafers can be measured. Charged particle activation analysis was applied to samples with [C] around 1015 cm-3 and evaluated by IR.