Papers by Keyword: Impurity Diffusion

Abstract: We present ultra-shallow diffusion profiles performed by short-time diffusion of boron from the gas phase using controlled surface injection of self-interstitials and vacancies into the ntype Si(100) wafers. The diffusion profiles of this kind are found to consist of both longitudinal and lateral silicon quantum wells of the p-type that are self-assembled between the layers of microdefects, which are produced by previous oxidation. These layers appear to be passivated during short-time diffusion of boron thereby forming neutral d - barriers. The fractal type selfassembly of microdefects is found to be created by varying the thickness of the oxide overlayer, which represents the system of microcavities embedded in the quantum well plane.

Abstract: We present a unified simulation of diffusion in silicon (Si) and silicon dioxide (SiO2) that is based on the diffusing dopant species and point defects that primarily contribute to the diffusion. We first present the simulation of phosphorus (P) diffusion in Si based on the integrated diffusion model that we have developed and elucidate the mechanism of the appearance of the anomalous P in-diffusion profile. The vacancy mechanism governs P diffusion in the plateau region, while the kick-out mechanism governs it in the deeper region, where Si self-interstitials dominate in the kink region and P interstitials dominate in the tail region. Next, we present the simulation of boron (B) diffusion and Si self-diffusion in SiO2. We examined the co-diffusion of implanted B and 30Si in thermally grown 28SiO2, which shows increasing diffusivities with decreasing distance between the diffusers and Si/SiO2 interface and with higher B concentration in SiO2. We propose a model in which SiO molecules generated at the interface and diffusing into SiO2 enhance both B diffusion and Si self-diffusion. The simulation showed that the SiO diffusion is so slow that the SiO concentration at the B and 30Si region critically depends on the distance from the interface. In addition, the simulation predicts the possibility of time-dependent diffusivities for B and Si because more SiO molecules should be arriving from the interface with time, and this time dependence was experimentally observed. Moreover, based on the B concentration dependence, the simulation result indicates that B and Si atoms in SiO2 diffuse correlatively via SiO; namely, the enhanced SiO diffusion by the existence of B enhances B diffusion and Si self-diffusion.

Abstract: Diffusion in a metal under an elevated hydrogen pressure is interesting in view of the fact that the diffusion is enhanced owing to the injection of a large amount of vacancies into the metal. This is peculiar to an elevated hydrogen pressure because diffusion in a metal is generally suppressed under a hydrostatic pressure. In the present article, the effect of an elevated hydrogen pressure on interdiffusion and impurity diffusion is reviewed in the Au-Fe system which has a large difference in the hydrogen solubilities between g -Fe and Au under an elevated hydrogen pressure.