Papers by Keyword: Oxygen Precipitation

Abstract: This paper presents a qualitative description and quantitative model of the technologically important problem of the transition from ineffective to effective internal gettering (IG) states in CZ silicon wafers as the precipitation of oxygen proceeds at high temperatures. Of central importance to the problem is a morphological transformation of growing oxide preciptitates from an initial strain free to a strained platelet state. The transition to effective IG occurs when approximately 107 cm-3 precipitate sites are transformed into the strained state. The transformation rates as a function of oxygen concentration and precipitate site density, deduced from etching and TEM, are presented. A model for the morphological transformation to the strained state is developed and with it a model for the annealing criteria for the threshold for effective gettering.

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.

Abstract: Thermal treatments to enhance precipitation like RTA, ramp anneal and argon anneal were performed on low oxygen 300 mm wafers without vacancy or interstitial agglomerates (“so called” defect-free material). Best results were achieved using high temperature argon anneal leading to a homogenous BMD and denuded zone formation. Furthermore the getter efficiency was positively tested by intentional Ni-contamination. Concepts to overcome the slip danger like improved support geometries and nitrogen codoping were also evaluated and are seen to be beneficial.

Abstract: The behaviors of isovalent impurities doped in Czochralski (CZ) silicon crystal have attracted considerable attention in recent years. In this article, a review concerning recent processes in the study about germanium in CZ silicon is presented. The disturbance of silicon crystal lattice in and the influence on the mechanical strength due to germanium doping is described. Oxygen related donors, oxygen precipitation and voids defects in germanium doped Czochralski (GCZ) silicon has been demonstrated in detail. In addition, the denuded zone formation and the internal gettering technology of GCZ silicon is also discussed.