Thin gate oxide radio frequency （RF） PDSOI nMOSFETs that are suitable for integration with 0.1μm SO1 CMOS technology are fabricated, and the total ionizing dose radiation responses of the nMOSFETs having four different device structures are characterized and compared for an equivalent gamma dose up to 1 Mrad （Si）, using the front and back gate threshold voltages, off-state leakage, transconductance and output characteristics to assess direct current （DC） performance. Moreover, the frequency response of these devices under total ionizing dose radiation is presented, such as small-signal current gain and maximum available/stable gain. The results indicate that all the RF PDSOI nMOSFETs show significant degradation in both DC and RF characteristics after radiation, in particular to the float body nMOS. By comparison with the gate backside body contact （GBBC） structure and the body tied to source （BTS） contact structure, the low barrier body contact （LBBC） structure is more effective and excellent in the hardness of total ionizing dose radiation although there are some sacrifices in drive current, switching speed and high frequency response.
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.
0.5μm-gate-length lateral double-diffused metal-oxide-semiconductor field-effect transistors （LDMOSFETs） with low barrier body contact （LBBC） and body tied to the source （BTS） were fabricated on silicon-on-insulator （SOI） substrates. The back-gate effects on front-channel subthreshold characteristics, on-resistance, and off-state breakdown characteristics of these devices are studied in detail. The LDMOSFETs with the LBBC structure show less back-gate effect than those with the BTS structure due to better control of the floating body effect and suppression of the parasitic backchannel leakage current. A model for the SOl LDMOSFETs has been given,including the front- and back-channel conductions as well as the bias-dependent series resistance.
The effects of total ionizing dose radiation on direct current （DC） and small-signal radio frequency （RF） performance of multi-finger RF partial deplete silicon-on-insulator lateral double diffused MOS （PDSOI LDMOS） transistors are investigated. The radiation response of the LDMOS transistors with different device structures is characterized for an equivalent gamma dose up to 1Mrad（Si） at room temperature. The front and back gate threshold voltages, off-state leak- age, transconductance, and output characteristics are measured before and after radiation, and the results show a significant degradation of DC performance. Moreover, high frequency measurements for the irradiated transistors indicate remarkable declines of S-parameters, cutoff frequency, and maximum oscillation frequency to 1Mrad（Si） exposure levels. Compared to the transistors with the BTS contact structure,the transistors with the LBBC contact do not show its excellent DC radiation hardness when the transistors operate at alternating current （AC） mode.
