High temperature oxygen implantation in silicon: Soil structure formation characteristics

Abstract

It has recently been shown that a high quality silicon-on-insulator (SOI) system may be obtained via high dose implantation of oxygen followed by an appropriate high temperature annealing. This technique appears to be a potentially powerful tool for VLSI technology applications. In the present paper we describe a study of the SOI system formation in an attempt to correlate its physical characteristics to the substrate temperature during oxygen implantation and to the high temperature annealing parameters. In order to form a buried SiO 2 layer, single-crystal, n-type, (100) Si wafers were implanted with 1.4 × 10 18 /cm 2 , 150 keV O + ions at temperatures in the range 450–750°C and subsequently annealed at temperatures between 1200 and 1300°C. The annealed samples were characterized using Rutherford backscattering (RBS)/channeling measurements, Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and cross-sectional transmission electron microscopy (TEM) analysis. The results confirm our previously reported experimental evidence showing that minimum residual damage for the “as implanted” state of the Si surface layer can be observed for an implantation temperature in the range 600–650°C. During the subsequent high temperature annealing most of the implanted oxygen is progressively removed from the Si surface layer by dissolution of the SiO 2 precipitates, followed by oxygen diffusion and trapping in the buried oxide layer. The resulting oxygen contamination of the Si surface layer drops below 10 19 at./cm 3 after a 2 h-annealing at 1300°C. During a further annealing the spatial rearrangement of the SOI structure occurs, leading to an improvement in the quality of the Si/SiO 2 interface and a decrease in the density and size of the SiO 2 precipitates. The residual oxygen concentration in the Si surface layer appears, however, to be related to the morphology of the SOI system in the “as implanted” state, and thus to the substrate temperature during implantation.