PERFORMANCE AND RELIABILITY ENHANCEMENT FOR CVD TUNGSTEN POLYCIDED CMOS TRANSISTORS DUE TO FLUORINE INCORPORATION IN THE GATE OXIDE

The impacts of CVD tungsten polycide (WSi(x)) on MOSFET performance an d reliability are studied in this letter. The WSi(x) process is shown to enhance the S/D lateral extent for both N- and P-channel devices vi a CGD and L(eff) measurements, confirming previous suspicion [1]. This enhanced S/D extent is found to be easily modulated by drain-to-gate bias, which is favorable for achieving both higher drive currents and higher S/D punch-through voltages than those of non-WSi(x) devices. Bo th electron and hole mobility for the WSi(x) device are also slightly higher and closer to the published data compared to the non-WSi(x) cas e. These effects together yield about > 5% improvement for nMOSFET and > 10% improvement for pMOSFET in drive current at a given punch-throu gh voltage. The channel hot-electron lifetime for the n-channel WSi(x) device is about 10 times higher than that of the non-WSi(x) one. Thes e enhancements in both performance and reliability make the WSi(x) dev ice very attractive for VLSI CMOS technologies.