Characterization of a Czochralski grown silicon crystal doped with 10²⁰ cm^‐3 germanium

Abstract

A dislocation-free silicon single crystal doped with 10 20 cm -3 germanium (Ge) has been grown using the Czochralski (CZ) growth technique. The Ge concentration in the seed-end and tang-end of the crystal was 8×1019 cm -3 and 1.6×10 20 cm -3 , respectively. The effective segregation coefficient of Ge, the distribution of flow pattern defects (FPDs) and the wafer warpage have been characterized. Both the effective segregation coefficient and the equilibrium segregation coefficient of Ge in silicon were evaluated. Then, the density of FPDs was traced from seed-end to tang-end of the ingot, a suppression of FPDs by Ge doping was shown. That is probably because the Ge atoms consume free vacancies and thus a higher density of smaller voids is formed. Furthermore, the mechanical strength of wafers has also been characterized by batch warpage analysis. The warpage in the seed-end was larger than that in the tang-end of the ingot, showing that the mechanical strength of wafers is enhanced by Ge doping. Such improvement is interpreted by an enhanced dislocation pinning effect associated with the enhanced nucleation of grown-in oxygen precipitates in the Gedoped silicon wafers.