Abstract

The evolution of smart power technology offers a variety of advantages in terms of reliability, reduction of interfaces, and reduced weight and size of the component. It has created a market for monolithic power integrated circuits that can incorporate sensors and protection functions. The basis for smart power technology is the integration of interface circuits, sensors, and protection circuitry with power devices. The interface function is made with CMOS circuits specially designed to operate in noisy and high temperature environments.

The purpose of the thesis is to describe and analyze new power semiconductor devices which are suitable for smart power applications. New device structures with recently developed novel device concepts are studied and suggested. A survey of related power semiconductors and their operations is studied. The main requirements and trade-off between device characteristics for the smart power technology are also listed in this study.

Clear understanding of the transport physics and physical models used for the analysis of power semiconductors is essential to obtain accurate simulation results and to study new device structures. Transport physics and physical models for the simulation of power semiconductors are therefore described.

Lateral power semiconductor structures are widely used as smart power devices in automotive and consumer applications. The main performance parameters for these devices are the on-resistance $R_\mathrm{on}$, the breakdown voltage (BV), and the switching characteristics. $R_\mathrm{on}$ and BV are inversely related to each other. Reducing $R_\mathrm{on}$ while maintaining a BV rating has been the main issue of smart power devices.

New concepts such as super-junction and lateral trench gate are studied and extended in this study to improve the on-state characteristics of lateral power semiconductors. Assuming complete charge balance between the $n$- and $p$-column of the drift region of the super-junction structure, the drift doping can be increased drastically.

A trench gate can be formed laterally on the side wall of a trench and the channel current flows thus in lateral direction through the trench side walls. This allows increasing the channel area, and it decreases the on-state resistance of the devices. Furthermore, an unbalanced super-junction structure is proposed, which has a larger $n$-column width to increase the on-state conduction area in the drift region. In our study two- and three-dimensional numerical simulations are performed to understand device behavior and to optimize new device structures.