Modeling of Schottky junction transistor using Monte Carlo device simulation technique
As the semiconductor feature size reduces and enters into nanometer scale realm, modeling of device characteristics becomes tedious because new physical phenomena such as effects of quantum mechanical tunneling become more relevant at this ultra small scale. As a result limitations of traditional modeling tools like Medici, Silvaco are reached because the models are based on drift diffusion or hydrodynamic models which are based on simplified approximate solution of the Boltzmann transport equation. So to capture physical behavior appropriately of the Schottky Junction Transistor (SJT) having gate length of 0.1μm or below a physics based model Monte Carlo transport Kernel is developed. The motto of this dissertation is to develop the transport model for the SJT and projects the characteristics features of the device when the dimension goes down and to estimate the behavior in terms of figure of merits of the device.
To develop the transport model, based on the solution of the Boltzmann Transport Equation, for modeling n-channel silicon-on-insulator (SOI) MESFETs, the 2D in-house Ensemble Monte Carlo device simulator is being used. All relevant scattering mechanisms for the silicon material system have been included in the transport model. Scattering from the rough Si/SiO 2 interface is included as a real space treatment and utilizing two different but consistent methods. Major modifications in the in-house device simulator to model this particular device structure have been made in the description of the carrier flow from the gate contact to the conduction channel, which takes place mainly by tunneling through the Schottky barrier at the silicon/CoSi2 interface. For proper inclusion of the gate tunneling and thermionic emission currents we have utilized the transfer matrix approach for linearized potentials, that leads to Airy function formulation. Once the model has been developed, the performance of the SJT in terms of figure of merits cutoff frequency, voltage gain has been evaluated and verified with experimental results. Concomitantly, on the basis of performance, the optimized device structure has also been evaluated. Small signal analysis was also performed to estimate the cutoff frequency and voltage gain as well as small signal parameters of the SJT. From the observed results one can predict that due to its salient features SJT is a suitable candidate for micropower r.f. application.