Early stages of oxygen precipitation in si: morphology and structure

Abstract

Intrinsic gettering in Si - VLSI technology depends on a controlled initial stage of oxygen precipitation and is characterized by a complicated interaction of growth-induced microdefects, self interstitial (SiI) generation and strain caused by SiO2 precipitate growth and secondary defects, table 1. We address the controversial issues of the identity of ribbon-like defects (RLDs) and of the nature of oxygen precipitate nuclei.RLDs were initially identified by HRTEM as coesite, a high pressure phase of SiO2. Recently, both Bourret and Reiche et al have interpreted the RLDs as hexagonal Si, or agglomerates of Si. We wish to make the point that the evidence against coesite is, as yet, not conclusive, and present circumstantial evidence in favour of coesite: (1) The loss of interstitial oxygen correlates with the density of RLDs (Fig. 1) at 450 - 485°C.