Detection and Characterization of Precipitates in Annealed Cz Silicon Wafers

(Received 19 December 1994, revised 2 May 1995, accepted 24 May 1995)

Abstract
A Scanning InfraRed Microscope (S.I.R.M.), a Light Beam Induced Current mapping (L.B.I.C.), a Fourier Transform infrared spectroscope (F.T.I.R.), and a minority carrier diffusion length measurements tool have been associated to detect precipitates in annealed Czochralski (Cz) silicon wafers and to evaluate their recombination strength with or without metallic contamination. The influence of a phosphorus diffusion was also investigated. After two step annealings (750 °C - 16 h and 900 °C - 24 h or 96 h) S.I.R.M. reveals the presence of precipitates, while L.B.I.C. maps display a ring-like distribution of recombination centers and minority carrier diffusion length ( L_n) collapses to 2  m. Copper contamination does not significantly modify the preceding observations when precipitates are formed. Phosphorus diffusion near the surface shrink the precipitates revealed by M.I.R.B. but do not suppress the ring-like patterns in the L.B.I.C. maps and L_n increases slightly. These results suggest that the recombination strength of precipitates does not depend on a metallic decoration but more probably on interfacial states between the precipitates and the host crystal or on associated extended defects.