Effects of co-doping nitrogen and germanium on dislocation gliding in Czochralski silicon: Implication for improving mechanical strength

Abstract

Improving the mechanical strength of Czochralski (CZ) silicon is of significance for increasing the manufacturing yield of integrated circuits. In this work, we have comparatively investigated the dislocation gliding behaviors in the conventional CZ silicon, nitrogen (N)-doped CZ silicon, germanium (Ge)-doped CZ silicon as well as Ge and N co-doped CZ silicon subjected to the indentations for 30 min at different temperatures in the range of 850–1050 °C with an interval of 50 °C. It is found that the suppressing effect of N-doping on the dislocation gliding is strongest at 950 °C and becomes slightly weakened at higher temperatures, while Ge-doping does not exert a remarkable suppressing effect on the dislocation gliding until the temperature exceeds 950 °C. The co-doping of N and Ge impurities takes both advantages of N- and Ge-doping to suppress the dislocation gliding in CZ silicon at the aforementioned temperatures. More importantly, at 1000 and 1050 °C that are the typical processing temperatures for integrated circuits, the N and Ge co-doping exhibits a stronger suppressing effect on the dislocation gliding in CZ silicon than the single Ge- or N-doping. This indicates that the mechanical strength of CZ silicon in terms of the resistance of dislocation gliding at a high temperature can be further improved by co-doping Ge and N impurities. It is believed that the N-doping can result in the formation of larger grown-in oxygen precipitates and N–O complex-related pinning agents within the dislocations to suppress the dislocation gliding at 850–1050 °C with the strongest suppressing effect at 950 °C, while the suppressing effect of Ge-doping on the dislocation gliding at the temperatures exceeding 950 °C is tentatively ascribed to the formation of Ge–O complexes near the front of the dislocation lines.