Characterizations of NiSi2-Whisker Defects in n-Channel Metal–Oxide–Semiconductor Field-Effect Transistors with $\langle 110\rangle$ Channel on Si(100)

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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 $\langle 110\rangle$ channel on Si(100) and anomalously increase the leakage current between the drain and the source. A NiSi2 whisker elongates toward the $\langle 110\rangle$ 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 $\langle 110\rangle$ channel before the Ni silicide formation. These trench-edge defects were not observed in the $\langle 100\rangle$ 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 $\langle 110\rangle$ direction during the silicidation annealing. As a result, NiSi2-whisker defects are generated toward the $\langle 110\rangle$ direction at the trench edge.
2010-12-25