No abstract

Gettering of Cu and Ni in wafers with low and high concentrations of interstitial oxygen was investigated by haze tests. The RTA induced getter effects for Cu and Ni in low-oxygen and high-oxygen wafers are based on two different getter mechanisms, internal gettering by oxide precipitates and internal gettering by nanometer sized voids (noids), respectively. Both types of internal gettering contain a defect denuded zone below the surface. While gettering by noids is active immediately after RTA, efficient gettering by oxide precipitates requires a certain annealing time in order to achieve a high enough density and size of precipitates. It was found that the getter effect of noids is destroyed by annealing at temperatures ≥ 800 °C.

Nitrogen doping of CZ silicon results in an early formation of large precipitate nuclei during crystal cooling, which are stable at 900°C. These are prone to develop stacking faults and high densities of defects inside defect denuded zones of CZ silicon wafers. Simultaneous doping of FZ silicon with nitrogen and oxygen results in two main stages of precipitate nucleation during crystal cooling, an enhanced nucleation around 800°C, which is nitrogen induced, and a second enhancement around 600°C, which depends on the concentration of residual oxygen on interstitial sites. A combined technique of ramping with 1K/min from 500-1000°C with a final anneal at 1000°C for 2h and lateral BMD measurement by SIRM provides a possibility to delineate v/G on nitrogen-doped silicon wafers. Surface segregation of nitrogen and oxygen during out-diffusion can explain the enhanced BMD formation in about 105m depth and the suppressed BMD formation in about 405m depth below the surface. The precipitate growth is enhanced in regions where nitrogen is filled up again after a preceding out-diffusion.