Diffusion of substitutional impurities in silicon at short oxidation times: An insight into point defect kinetics

Abstract

Oxidation-enhanced diffusion of phosphorus, arsenic, and boron and oxidation-reduced diffusion of antimony in silicon have been studied as a function of oxidation time. Data for the early phase of oxidation in dry oxygen from 5 to 60 min have been obtained. Oxidation-enhanced diffusivities show a steady decrease with decreasing oxidation rate for phosphorus, arsenic, and boron, with enhancements at long oxidation times in agreement with previously reported results. Antimony shows a reduction in diffusivity during oxidation. A model allowing calculation of diffusivity enhancement or reduction for all elements and oxidation times has been developed. The present data support the theory of a dual vacancy-interstitialcy diffusion mechanism for all the elements studied. The fraction of interstitialcy diffusion fI has been calculated, yielding fI=0.38 for phosphorus at 1000 °C, fI=0.30 for boron at 1000 °C, fI=0.35 for arsenic at 1090 °C, and fI=0.015 for antimony at 1100 °C. It has also been shown that the oxidation-induced supersaturation of self-interstitials is accompanied by an undersaturation of vacancies during oxidation. This undersaturation can be explained by a rate-limited bimolecular annihilation mechanism. This theory yields, for the first time, values for the vacancy-interstitial recombination-limited intrinsic vacancy lifetime in silicon under near-equilibrium conditions at high temperature; it also indicates the presence of an energy barrier to this recombination of the order of 1.4 eV.

Point defects and dopant diffusion in silicon

“…It was observed that antimony diffusion was retarded while phosphorus and boron diffusion were enhanced. The kinetics leading to this steady-state situation were first investigated by Antoniadis and Moskowitz (1982a). By investigating the short-time OED kinetics, they were able to gain some insight into the process of interstitialvacancy recombination at typical processing temperatures (900 C -1100 C).…”

“…The CV technique was also used by Antoniadis and Moskowitz (1982a) to measure short-time enhancements in the OED and oxidation-rate dependence of dopants.…”

Gedanken experiment on point defects in unidirectional solidified single crystalline silicon with no dislocations

“…It is therefore important to select t (min) fitting parameters to calculate the distribution of point defect concentrations. Based on the parameter set including the melting point values for equilibrium concentrations and diffusivities, energies of migration and formation [16], properties such as equilibrium concentrations and diffusion coefficients of vacancies and interstitials are determined by the following equations: DG IV is determined using the time constant of the recombination reaction, which is 2000 s at 1100 1C [17]. The heat carried by a vacancy and an interstitial, Q V n and Q I n , are determined using the model presented by Brown et al [4], which are defined as…”

A method for temperature profile measurement of silicon wafers in high-temperature environments

“…Dopant diffusion enhancement by oxidation depends on the fraction of diffusion due to the intersticialcy mechanism, as opposed to the vacancy mechanism, for a particular dopant. Several researchers have measured this fractional contribution for boron and phosphorus, with varying results, 15,16 but Antoniadis et al 17 suggest that phosphorus may have a slightly higher fraction of intersticialcy diffusion. In this case, the diffusivity of phosphorus would be more affected by the process of oxidation, and the phosphorus peak would diffuse more quickly than predicted, reducing the difference in concentration between dopants and increasing the resistivity.…”