HVVFET™: A new 0.25µm channel length RF POWER MOSFET with ultra low feedback capacitance

A novel short channel vertical RF MOSFET (termed HVVFET™) has been developed for avionics and L-band radar applications. The HVVFET employs a silicided polysilicon spacer that is formed along a vertical dielectric sidewall to serve as the gate. A second silicided poly layer is sandwiched between the gate interconnects and the Si wafer, thereby completely shielding the gate from the drain. Consequently, the HVVFET exhibits superior device characteristics such as a state of the art BVD_SS-R_ON-SP combination and very low capacitances, in particular, to the authors´ knowledge, a record low C_gd. The packaged HVVFET device with a total gate width of 64.5 mm shows a C_gd of 2.67×10^-18 and 2.32×10^-18 F/um at 25V and 40V respectively. The capacitance values are 1.65×10^-18 and 1.3×10^-18 F/um for a bare die under the same biases, representing a five-fold improvement over similar devices in the literature. The packaged HVVFET device exhibits superior RF performances in the 1.0-1.2GHz band, including a 19dB power gain, 0.8W/mm output power at ldB compression and 45% PAE, and a 20:1 load mismatch survivability.