The effect of a temperature gradient upon As diffusion was investigated. Wafers implanted with As were subjected to temperature gradients of the order of 100C/cm in a rapid thermal annealing apparatus. No measurable differences were observed in the As profiles upon changing the direction of the temperature gradient in low (1014/cm2) dose (111) and (100) material. There was also no measurable difference in the As profiles in high (6 x 1015/cm2) dose (100) material due to a temperature gradient. However, in high-dose (111) material, the As penetrated deeper on the cold side. The difference in As penetration into the cold and hot sides of the sample was of the order of 10 to 15nm for a 10 to 90s anneal. The Soret effect contribution to isothermal diffusion was estimated by solving the diffusion equation. The calculated results agreed well with measured results for low and high-dose (100) material. However, they disagreed in the case of high-dose (111) material. It was suggested that a defect-enhanced Soret effect, which coupled the As diffusion flux to the heat flux in the highly disordered crystal, could cause the observed temperature gradient dependence of the As penetration.

A.Feygenson, J.N.Zemel: Thin Solid Films, 1988, 157[1], 49-57