Oxygen diffusion in silicon and the influence of different dopants

Abstract

The diffusion of oxygen in silicon is an important process with respect to the planar technology of semiconductor devices. A sensitive method was developed to measure oxygen concentration profiles in silicon by means of the nuclear reaction 18O( p,n) 18F. By this activation technique oxygen concentrations as low as 1015 atoms cm−3 can be registered in a silicon layer of 5 μ thickness. In a subsection we discuss the difficulties and limitations caused by the always present natural oxide layer on the surface of the sample. The temperature dependence of the diffusion constant has been determined between 1000 and 1280 °C. An activation energy for the diffusion of oxygen in silicon of 3.15 eV has been extracted from these data. In addition, the influence of other dopants as Ga, Al, B, and P to the oxygen diffusion has been investigated. The deviations we found in the oxygen concentrations appear to be produced by the preparation techniques of the samples rather than by a direct influence of the different dopants.