Physical and Numerical Modeling of Impurity Gettering in Silicon

Physical and numerical modeling of gettering metallic impurities away from Si device active regions has abeen carried out. The modeled aspects include the dissolution of precipitated impurity (if any), diffusion of dissolved impurities from the gettered to the gettering region, and gettered impurity stabilization in the getttering region via segregation and/or precipitation processes. The modeledimpurities include fast diffusing interstitial (i) species and substitutional-interstitial (s-i) species. A wafer backside Al layer, wafer frontside indiffusion of P, indiffusion of P together with an Al layer (P+Al), and intrinsic gettering (IG) are the modeled gettering techniques. The gettering of i species may be rapidly accomplished using Al of IG, via segregation or precipitation processes. The gettering of s-i species involves point defects and is best accomplished by the P+Al technique. If initially impurities are precipitated, they can only be efficiently gettered in a reasonable time at temperatures much higher than the precipitation temperature.