Improved Layout Dependence in High Performance SiGe Channel CMOSFETs

The device degradation problem due to compressive STI in devices with narrow width or small diffusion length can be greatly relieved in SiGe channel devices with the post-STI epitaxy process. The (110)SiGe PMOS realizes 77% current gain over (100)Si PMOS at 1um gate width, and current gain is increased to 112% at 0.12um gate width. A 42% current improvement in (100)SiGe NMOS at 0.12um gate width is also reported. Moreover, for diffusion length ranging from 2.71um to 0.26um, less than 4% current variation is obtained in SiGe channel devices compared to the 8~12% current variation in Si channel devices. The improved layout dependence is resulted from the lower STI stress in post-STI SiGe epitaxy process.