Junction Leakage Generation by NiSi Thermal Instability Characterized Using Damage-Free n+/p Silicon Diodes

Abstract

Using n+/p junctions formed by solid phase diffusion, a clear correlation between junction leakage and NiSi thermal instability was readily established. After forming an NiSi layer on damage-free junctions, various post-annealing processes at around the silicidation temperature were applied. A consistent and systematic rise of the leakage level was observed with the increase of the annealing time and the temperature. The migration of the released Ni atoms away from the NiSi layer, the subsequent clustering of the migrant Ni atoms, and the eventual formation of generation-recombination centers deep inside the Si substrate were identified as the basic components of the principal leakage mechanism. Detailed analysis of the thermally stimulated ingressive movement of the leakage-depth profiles revealed a substantial Ni burst at an early stage of annealing. This anomalous Ni burst imposes severe restrictions on junction shallowing for NiSi technology and sets a strict upper limit on the allowable process temperature for effective leakage suppression.