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A new model to semiconductor device electronic noise is presented in the framework of semiclassical transport theory. The salient feature of this model is that it connects the current noise characteristics directly to the physics of scattering of the semiclassical transport theory and makes no additional assumption regarding the nature of noise. Employing this approach, this work investigates the spatial origin of the current noise across two semiconductor structures. In this approach the terminal current noise is directly related to carrier scattering inside the device, which is accounted for in the Boltzmann transport equation (BTE), without the need to add Langevin noise terms to the calculations. Accordingly, it utilizes the well-established spherical harmonics expansion (SHE) technique to solve the BTE, and it combines analytical and numerical methods, in contrast with the Monte Carlo (MC) approach that employs ensemble averages of randomly generated events. The model leads to the solution of a time-dependent transient solution of the BTE with special initial and Ohmic boundary conditions that is solved in the frequency domain to directly compute the terminal current noise spectral density. It is also shown that with this approach the Nyquist theorem under thermal equilibrium conditions is recovered.

Microelectromechanical systems (MEMS) are devices that have static or movable components with dimensions on the scale of a micrometer. One particular device that is widely used commercially is the MEMS accelerometer. Such accelerometers typically contain some movable micro beams that measure acceleration in one or two orthogonal directions. Major markets for MEMS accelerometers are automobile airbag triggers, earthquake detection circuits and health care. MEMS accelerometers have advantages over conventional accelerometers because they are smaller, lighter and cheaper. Since MEMS accelerometers are used in many systems, the noise characteristics of these devices are very important. The noise characteristics will influence the performance of the accelerometers especially when operating at lower g conditions. In this work, we report on the noise characteristics and special measurement techniques for Analog Devices ADXL202, ADXL 105 and ADXL 190 accelerometers.

Our implementation of a fixed-point iteration technique for the three-dimensional (3D) steady-state simulation of MOSFET devices is presented. The simulation program is employed to investigate narrow channel effects on the device current-voltage characteristics. Particularly, the effects of impact ionization and the effects of variations in channel width and the field oxide bird's beak angle are evaluated. The degree to which various field oxide configurations isolate the device from the gate contact over the oxide transition region is determined by comparing the current-voltage characteristics with those of an idealized device with perfect isolation. Perfect isolation is simulated by setting the normal component of the electric field to zero at the semiconductor-field oxide interface. Simulation results show that the 3D computations are essential to account for rapidly varying charge densities and generation rates near the channel edge. Moreover, it is observed that the isolation effects of field oxides increase for larger bird's beak angles.

We present a numerical technique which employs a local-in-time initial guess for the transient simulation of SOI MOSFETs. Specifically, the goal of this work is to compute the transient drain current which exhibits overshoot. A critical factor in such computations is the choice of the initial guess at each time point after the gate ramp. Our numerical simulations have shown that the use of the previous time point solution as an initial guess in the Gummel iterations fails to predict the decay in the drain current from its maximum overshoot value. This difficulty is circumvented when the steady-state solution is used as a local-in-time initial guess. We use the diagonally implicit Runge-Kutta method for the time domain discretization. A fixed-point iteration technique is employed for the space domain iterations. To demonstrate the usefulness of the local-in-time method, numerical results of the transient drain current for various device parameters, such as the silicon film doping, silicon film thickness and back-gate bias are presented.

The switching characteristics of ultra-thin SOI CMOS inverters with hot-carrier-induced degradations are examined by using device simulations. The simulator employs a robust fixed-point iteration method to avoid conventional matrix solutions. Potential-dependent interface traps and oxide trapped charges are used to model the degradations. The effects of front and back channel degradations in an nMOS device of a CMOS inverter are investigated in steady-state and transient regimes. The nonlinear variation of interface charges cannot be simulated by using a single nMOS device alone since the transition of the inverter is also determined by the pMOS transistor. It is found that the stagnant holes generated by impact ionization have a much greater effect on the rate of the pull-down transient than that of interface charges.