Oxygen concentration dependence of as-grown defect formation in nitrogen-doped Czochralski silicon single crystals

Abstract

The interstitial oxygen concentration ([OI]) dependence of the as-grown defect (voids and dislocation clusters) behavior in nitrogen-doped silicon crystals fabricated by Czochralski technique (Cz-Si) have been investigated. Nitrogen-doped Cz-Si crystals with [OI] values of 7–8 and 1–3 × 1017 atoms cm−3 are evaluated, and it was found that the range of v/G in which as-grown defect-free (AGDF) region can be obtained become wide with decreasing [O I], where v is the crystal growth rate and G is the axial temperature gradient at the solid–liquid interface. This result indicates that as-grown defect suppression effect by nitrogen doping is enhanced at low [OI].By the analysis based on a thermodynamic model, it is shown that nitrogen–vacancy (NV) and nitrogen–oxygen (NO) complexes compete in the nitrogen-doped Cz-Si crystals and their concentration fraction changes with [OI] value. At low [OI], the concentration of the NO complex becomes low; thus, the concentration of nitrogen that can form NV complexes increases, thereby enhancing the as-grown defect suppression effect. Silicon wafers for insulated gate bipolar transistors (IGBTs) are required AGDF and oxide precipitate-free, therefore nitrogen-doped Cz-Si crystals with low [OI] values are suitable for the fabrication of silicon wafers for IGBTs.