Analysis of localized vibration of nitrogen complexes in CZ silicon

Abstract

Nitrogen doping reduces secondary defects in CZ silicon. It is necessary to establish the infrared measurement method of nitrogen (N) and nitrogen–oxygen (N–O) point defect (N–V) complex concentrations. In this study, we examine the vibration of N–O and N–V complexes by the molecular orbital calculation. First, we analyze the NNO and NNOO in as-grown crystal. The structures used for calculation are Si 40N 2O(and O 2)H 54. Vibration mode and induced dipole moment by localized vibration are obtained by vibrational calculation. We have shown that the sum of absorption of N and N–O peaks is closely related to the total N concentration measured by SIMS. It is to be noted that oscillator strength is proportional to square of induced-dipole. Weighted sum of absorption coefficient inversely proportional to oscillator strength is used in determining the conversion coefficient to N concentration. Next, we calculate the frequency and dipole moment of normal vibration modes of NNV and NNVV which are thought to be formed and affect the defect formation at high temperature. The structures used to calculate are Si 34N 2H 36 and Si 42N 2H 42. H 2O-type and BF 3-type asymmetric stretch vibrations are obtained. The frequency of NNV is 940 cm −1 in H 2O-type and 867 cm −1 in BF 3-type. In NNVV 909 and 920 cm −1 are obtained corresponding to H 2O-type and the BF 3-type vibrations, respectively. We are trying to find these peaks experimentally.