HYDROGEN DIFFUSION AND THE CATALYSIS OF ENHANCED OXYGEN DIFFUSION IN SILICON AT TEMPERATURES BELOW 500-DEGREES-C

The relaxation of stress-induced dichroism of the 9-mu-m oxygen infrared absorption band has been investigated for Czochralski silicon annealed isothermally at various temperatures in the range 225-350-degrees-C while the material was immersed in a hydrogen plasma. The indiffusion of hydrogen atoms enhanced the rate of oxygen diffusion so that the dichroism was lost progressively from the external surfaces of samples. Comprehensive ancillary measurements demonstrated that the oxygen diffusion jumps were catalyzed by collisions with diffusing hydrogen atoms, rather than some other fast-diffusing species. The measurements allowed the hydrogen diffusion coefficient to be estimated as 1.7 x 10(2) exp( - 1.2 eV/kT) cm2 s-1 for the range of temperatures investigated. Increased rates of thermal donor formation were also found due to enhanced long-range oxygen diffusion. The new data are related to previous reports of enhanced oxygen diffusion jumps found in Czochralski silicon given post-growth heat treatments in hydrogen gas. It is implied that concentrations of hydrogen atoms as low as 10(8) cm-3 may significantly enhance oxygen diffusivity.