Study Of RF Model Of 3D FinFET And Its Model Parameters Extraction Method

The size of field-effect transistors(FETs)is continuing to shrink under the instruction of the Moore's Law,and the structure of the device has become three dimensional.The parasitic effects of these new 3D devices are particularly complicated in radio frequency(RF)circuit,so the accurate model is necessary to apply the deep nanometer fin field-effect transistors(Fin FETs)to RF circuit.This paper presents an improved RF small-signal equivalent circuit model of Fin FETs and a novel parameter extraction method.The model we proposed matches well with the device-simulation data up to 300 GHz.The maximum error of the model is under 3.74% in both saturation and linear region.The main points of this paper are as follows:The characteristics of Fin FET and the limitation of the equivalent circuit model of planar MOSFET are first discussed in this paper,which proves that the existing modeling techniques are often insufficient for new devices.Then,an accurate RF model of Fin FETs and a novel parameter extraction method are proposed.All the parameters in the model are obtained based on the nonlinear rational function fitting.First,the extrinsic gate-to-drain/source capacitances,source/drain resistances,and substrate elements are obtained from Y-parameters under the off state.Then,the intrinsic electrical parameters are analytically determined through the de-embedding method.It's calculated that the maximum error of the model is less than 3.74% by comparing the simulation results of the equivalent circuit model in ADS with the device simulation data of TCAD.Through the analysis of the RF quality factors,the proposed model is proved to be physically meaningful as well.The bias and geometry dependency of the small-signal parameters are also discussed in this paper.Under the influence of the short channel effect and 3D channel structure,some model parameters like ?m vary differently with device size and bias,comparing with traditional long channel device.Based on this,RF performance of Fin FET is also discussed.Finally,the process variation dependency of the small-signal parameters are analyzed by changing the structure and doping profile of device and adding traps to the interface.The accurate model in this paper makes it possible to analyze the RF property of Fin FET.And some small-signal parameters that vary differently from traditional planar MOSFETs are also explained,which would be helpful to both process optimization and circuit simulation.