Boron retarded diffusion in the presence of indium or germanium

Experimental results of Ge and In pre-amorphization by ion implantation show that the diffusion of B is retarded by the presence of Ge or In, and that this retardation is more important than the pre-amorphization (de-channeling) effect. Result shows that In retards B diffusion more than Ge, and the retardation effect due to In becomes greater with increasing retained dose of In. Larger In doses cause larger strain, which results in more B being tied up in immobile clusters near the surface. In order to achieve adequate retained dose of In, the implanted dose of In must be increased to 5×10¹⁵ cm^-2. After anneal, the junction depth (at 10¹⁸ cm^-3) is reduced from 628 Å in the control wafer (no In co-implant) to 480 Å.