Thermal stability of Cu/NiSi-contacted p(+)n shallow junction

Abstract

The thermal stability of Cu/NiSi-contacted p(+)n shallow junction diodes was investigated with respect to their electrical characteristics and metallurgical reactions. The TaN/Cu/NiSi/p(+)n junction diode remained intact after 30min thermal annealing at temperatures of up to 350degreesC. Upon annealing at 375degreesC, a marked increase in reverse bias leakage current occurred, and secondary ion mass spectrometry (SIMS) analysis indicated that Cu started to penetrate into the NiSi-contacted shallow junction region. After a higher temperature annealing at 425degreesC, a Cu3Si phase was formed. The failure of the TaN/ Cu/NiSi/p(+)n junction diodes is attributed to the penetration of Cu through the NiSi layer into the junction region, leading to junction degradation by introducing deep-level trap states and the eventual formation Of Cu3Si.