Device structure and fabrication process of SOI nMOSFET depleted partially are p roposed for multi-gigahertz RF applications.Many advanced techniques for deep submiron MOSFETs are incorporated into the proposed device.Main steps and condit ions in process are given in details,with simulation and optimization by using t he process simulator,Tsuprem4.Experiment results of 0.25μm SOI RF nMOSFET are i n consistence with simulated ones,and excellent or acceptable parameters of devi ce performance are obtained for multi-gigahertz RF applications.
This paper presents the fabrication and performance of a 0.18μm nMOSFET for RF applications. This device features a nitrided oxide/poly-silicon gate stack, a lightly-doped-drain source/drain extension, a retrograde channel doping profile, and a multiple-finger-gate layout,each of which is achieved with conventional semiconductor fabrication facilities. The 0.18μm gate length is obtained by e-beam direct-writing. The device is fabricated with a simple process flow and exhibits excellent DC and RF performance： the threshold voltage of 0.52V, the sub-threshold swing of 80mV/dec, the drain-induced-barrier-lowering factor of 69mV/V, the off-state current of 0.5nA/μm, the saturation drive current of 458μA/μm （for the 6nm gate oxide and the 3V supply voltage）, the saturation transconductance of 212μS/μm,and the cutoff frequency of 53GHz.
A novel local-dielectric-thickening technique i s presented for performance improvements of Si-based spiral inductors.This technique employs the processes of deposition,photolithography,and wet-etching,to locally thicken the oxide layer under the inductor,which can decrease the substrate loss and improve the inductor performance.Both the structures and processes are compact,economical,and compatible with CMOS processing.Several square spiral inductors with different inductances are fabricated,and the quality factors and the self-resonant frequencies both increase clearly with this proposed technique:for the 10nH,5nH,and 2nH inductors,the peak quality factors are effectively improved by 46.7%,49.7%,and 68.6%,respectively;however,the improvement percents of the self-resonant frequencies are more significant,which are 92.1%,91.0%,and no less than 68.1% respectively.
