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/sub x/) on MOSFET performance and reliability are studied in this letter. The WSi/sub x/ process is shown to enhance the S/D lateral extent for both N- and P-channel devices via C/sub GD/ and L/sub e/ff measurements, confirming previous suspicion. 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/sub x/ devices. Both electron and hole mobility for the WSi/sub x/ device are also slightly higher and closer to the published data compared to the non-WSi/sub x/ case. These effects together yield about >5% improvement for nMOSFET and >10% improvement for pMOSFET in drive current at a given punch-through voltage. The channel hot-electron lifetime for the n-channel WSi/sub x/ device is about 10 times higher than that of the non-WSi/sub x/ one. These enhancements in both performance and reliability make the WSi/sub x/ device very attractive fog VLSI CMOS technologies.<>