Dopant enhanced H diffusion in amorphous silicon and its effect on the kinetics of solid phase epitaxy

Abstract

Dopant enhanced H infiltration into surface amorphous Si ( a-Si) layers formed by ion implantation is reported. Dopant enhanced H in-diffusion is observed for both B and P implant profiles in a-Si and the effect of this enhanced in-diffusion on the kinetics of solid phase epitaxial (SPE) crystallization is quantified. Near-surface dopant profiles were formed by multiple energy ion implantation. Anneals were performed in air over the temperature range 500–640 ° C. Secondary ion mass spectrometry (SIMS) analysis of partially annealed samples reveals that implanted dopants enhance the in-diffusion of H thereby increasing its concentration at depths well beyond the dopant implanted region. The effect of an enhanced H concentration on crystallization rates via SPE is monitored using time resolved reflectivity. Boron is found to enhance both H diffusion and SPE to a much greater extent than P. Possible links between the SPE and H diffusion mechanisms are discussed and the possibility of applying SPE models to H diffusion is explored. Implications for the formation of shallow junctions are also considered.