Characterizations of NiSi2-Whisker Defects in n-Channel Metal?Oxide?Semiconductor Field-Effect Transistors with Channel on Si(100)

Electrical and physical characteristics of nickel disilicide (NiSi2)-whisker defects in n-channel metal–oxide–semiconductor field-effect transistors (nMOSFETs) on Si(100) have been investigated. NiSi2-whisker defects are easily generated in narrow-channel-width nMOSFETs with the channel on Si(100) and anomalously increase the leakage current between the drain and the source. A NiSi2 whisker elongates toward the direction along the trench edge and pierces the channel region. These physical properties of NiSi2-whisker defects were revealed by detailed failure analyses. The influence of the recessed depth of trench-fill oxides on NiSi2-whisker defects was also investigated. Furthermore, it is found that trench-edge defects, such as Si(111) stacking faults, are generated in the channel before the Ni silicide formation. These trench-edge defects were not observed in the channel. We also propose a generation model for NiSi2-whisker defects. The nucleation of NiSi2 precipitates might be generated at trench-edge defects, and Ni atoms diffuse toward the direction during the silicidation annealing. As a result, NiSi2-whisker defects are generated toward the direction at the trench edge.