Fabrication And Characterization Of Germanium Channel Schottky Barrier MOSFET

With downscaling of MOSFET to its physical limitation, germanium has been extensively investigated as channel material to replace Si due to its high carrier mobilities. Schottky barrier MOSFET is expected for the competitive MOSFET devices due to its advantages of shallow junction preparation, low resistance contact preparation, low temperature process and process simplification.Ge SB-MOSFETs were simulated by TCAD. Both pn junction source/drain MOSFET and SB-MOSFET were designed and fabricated on bulk Ge, Si, GOI and SOI substrates. The performance of these devices were characterized and comparatively analyzed.1、P-type Ge channel Schottky barrier MOSFET (SB-MOSFET) was studied by simulation using silvaco TCAD. The simulation results indicate that the device based on GOI substrate has a better transfer characteristics and smaller off-state current(Ioff) compared to the one based on Ge substrate. The on-state current of the SB-MOSFET increases with the increase of its electron Schottky barrier height (eSBH) in the drian and source. On the other hand, its off-state current could be lowered by the reduction of the Ge thickness of the GOI substrate.2、Ge-and Si-channel MOSFET with pn junction S/D were prepared and characterized. The effective hole mobility of the Ge MOSFET reaches200cm2.V-1s-1, which is a little larger than universal Si device and three times over the control Si device. The performance of the devices are suffered from the large source/drain contact resistance due to the low doping concentration and gate leakage current with the degradation of the gate dielectric by annealing under high temperature, which leads to limited drive current.3、Si-and Ge-channel MOSFET with Schottky barrier S/D are prepared respectively. The Si channel MOSFET gets a small subthreshold swing(SS) and a large Ion/Ioff ratio. Its SS is smaller than170mV/dec and the Ion/Ioff ratio larger than103. The SB-MOSFET based on Ge substrate gets a Ion/Ioffratio of4.5×102, a SS of278mV/dec and a83%enhancement of effective hole mobility over the universal Si device. Despite of the device fabricated on GOI substrate has a large off-state current due to its large channel doping concentration, it gets a peak effective hole mobility of300cm2.V-1s-1.