The precipitation of oxygen in silicon

Abstract

The precipitation of oxygen in silicon has been studied over a wide temperature range, using a number of experimental methods including: kinetic rate data from infra red absorption in the 9 μm band at 4.2 K, Particle densities by optical scattering between 1.5-3.0 μm (large precipitates), chemical etching of defects (medium precipitates) and small angle neutron scattering (small precipitates). From the Ham theory of diffusion limited precipitation, a direct relation between the kinetic time constants and the equilibrium numbers and sizes of particles is predicted - which is confirmed by the results. This places emphasis on the need for precise diffusion data over a wide range. This has been explored by extending the above work with classical oxygen in-diffusion measurements up to 1250°C and stress dichroism in the range 350ȁ400°C, from which a value of D is obtained over 12 orders of magnitude with a single activation energy ȲE = 2.50 ± 0.15 eV. Recent results throw some light on the basic diffusion mechanism and the role of supersaturation and other impurities in the nucleation stage of this process.