Oxygen Precipitation in Nitrogen Doped CZ Silicon

Abstract

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.

A contribution to oxide precipitate nucleation in nitrogen doped silicon

“…Ramping from 500 °C reveals most of the grown-in oxide precipitate nuclei [21]. In a previous paper, we have also shown that this BMD profile follows the theoretically simulated v/G profile, what means that it follows the vacancy supersaturation [23]. This indicates that the concentration of intrinsic point defects is of strong impact on the density of grown-in nuclei.…”

“…A RATOC MILSA IRHQ-2 light scattering tomograph with a Nd-YAG Laser (1060 nm wavelength) was used for the LST measurements. CZ reference wafer grown under similar pulling conditions [23]. These large grown-in precipitate nuclei in NCZ silicon can easily grow during thermal processing making the generation of bulk micro-defects for internal gettering very easy.…”