| 摘要 |
PURPOSE:To control the rate of oxidation at the time of a drive diffusion, to balance the lowering of silicon surface concentration by the segregation effect of boron and the activation of boron by heat and to equalize surface impurity concentration in a substrate surface and in a substrate by adding oxygen into N2 gas. CONSTITUTION:In a boron diffusion method in which boron is deposited on silicon substrates 2, and heated in an atmosphere containing no boron, and a drive diffusion is conducted and boron is redistributed, the drive diffusion is accelerated in an atmosphere in which O2 is added into an inert gas such as N2 by 0.1% or 20%. Since concentration distribution on a substrate surface after the diffusion is subject to an increasingly larger effect at an increasingly earlier step of a drive diffusion process, a sufficient effect is displayed even when only a substrate insertion process is performed in said mixed atmosphere. The addition ratio of O2 is determined by impurity concentration on the substrate surface after the drive diffusion required and the whole sequence.
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