Intrinsic Junction Leakage Generated by Cobalt In-Diffusion during CoSi2 Formation

Abstract

Using solid phase diffusion, damage-free n+/p junctions are fabricated to investigate intrinsic junction leakage induced by CoSi2 formation over them. With finely adjusted junction depth, xj, the first clear and systematic investigation is successfully conducted. Leakage generation with the shallowing xj proceeds uniformly, maintaining a tight ensemble distribution. Cobalt in-diffusion deep inside the silicon substrate and resultant generation-recombination (GR) center formation are suspected to be the primary causes of the intrinsic leakage. An anomalously large cross section of the GR centers indicates cobalt clustering as a physical origin of the gap states. Caution is advised regarding the cobalt inward migration, which could threaten the realization of future metal-insulator-silicon devices.