4. Device Simulation and Parameter Modeling

This chapter explains the concept of device simulation, especially in the context of the drift-diffusion transport model. Additionally to the semiconductor equations, a summary on modeling of the important parameters mobility and generation/recombination is given. Particularly with regard to the hot-carrier modeling in high-voltage devices, concepts for the estimation of the energy distribution function in the drift-diffusion model are presented.

Most of the simulations in this chapter are calculated using sample devices which are based on high-voltage devices made by ams [9]. They are n-channel lateral DMOSFETs with a gate oxide thickness of 7nm, fabricated in a 0.35µm CMOS-based technology. The gate length is 0.5µm, the width is 40µm, and the specified application voltage is 50V. The doping profile and the geometry are depicted in Fig. 4.1. The simulation domain extends in a depth of 15µm, while the figures depict only the upper half of the device. The drift-diffusion and hydrodynamic simulations in this work were performed using the device simulation tool MINIMOS-NT [120] and the GTS FRAMEWORK from Global TCAD Solutions [121].

Figure 4.1: Structure of the sample n-channel LDMOSFET used for simulation examples. The transitions between n- and p-doped regions are marked with bold black lines and the value of the net doping concentration is shown. The simulated structure of the device continues to 15µm, while only the upper part is presented.