The effects of thermal nitridation on phosphorus diffusion in strained SiGe and SiGe:C

Abstract

We investigated the thermal nitridation effects on phosphorus (P) diffusion in strained Si1−x Ge x and strained Si1−x Ge x :C y with up to 18 % germanium and 0.09 % carbon. P diffusivities under thermal nitridation (vacancy injection) and effective inert condition were compared. The results show that thermal nitridation can retard P diffusion in SiGe, but the effectiveness of this retardation method decreases with the increasing Ge and C content. When 0.06 and 0.09 % carbon are present in Si0.82Ge0.18, thermal nitridation slightly increases P diffusivity compared to the inert condition. The Ge dependence can be explained by the increasing contribution from the vacancy-assisted mechanism for P diffusion in strained SiGe with the increasing Ge content. In terms of interstitial undersaturation ratio $$ \frac{\left[ I \right] }{{ \left[ I \right]^{*} }} $$ in Si0.82Ge0.18, thermal nitridation can further decrease $$ \frac{\left[ I \right] }{{ \left[ I \right]^{*} }} $$ by 31–53 % on top of the carbon effect.