COMPUTER SIMULATION OF IMPURITY GETTERING CAPABILITY IN SILICON FOR CURRENT GETTERING TECHNIQUES

摘要

Capability of impurity gettering in silicon is simulated numerically. The considered techniques are boron-gettering by heavily boron-doped p~+ substrates, thin polycrystalline silicon films on the backside of wafers (PBS), and internal gettering (IG) induced by oxygen precipitates. Dominant gettering mechanism of the boron-gettering and the that of PBS are segregation-induced types. We accurately determined equilibrium constants of the segregation reactions for iron gettering at various temperatures. Using the determined values of the equilibrium constants, and introducing iron diffusion phenomena, we have succeeded to predict an iron impurity concentration in a surface region during a device fabrication process. In case of the IG, it is essential to predict a size distribution function of oxygen precipitates which act as the gettering sites. Therefore we have developed an industrially practical computer simulation technique based on the Fokker-Planck equation to predict the size distribution function of the oxygen precipitates. The calculated results of the precipitation behavior agree well with the experimentally observed ones.