1.2 kV Stepped Oxide Trench Insulated Gate Bipolar Transistor with Low Loss for Fast Switching Application

Abstract

In this article, a gate engineering technique is used in Insulated gate bipolar transistor (IGBT) for fast switching applications. The modification consists of stepped oxide pattern at gate terminal with n-poly layer sandwiched between two p-poly layers. The oxide thickness increases from top to bottom so as to create a stepped structure. The oxide thickness is lesser on channel side and higher on collector side. The less thickness beside the channel increases gate to emitter charges (QGE) by extracting extra charges along the channel. The presence of these extra charges also increases the collector current density resulting reduction in the area specific on-resistance (Ron.A). On the other hand, the higher thickness at the bottom side of gate offers reduction in gate to collector charges (QGC). Furthermore, to elongate the impact of QGC reduction, the low doped p-col region has been facilitated which also play an important role to increase the breakdown voltage by reducing corner electric field. This p-col region creates charge extraction path to swept out charges from the drift region while turn-off event and makes the device to turn-off quickly. The collective improvement in QGE and QGC provides fast switching to the proposed device by improving turn-off time by 63% and also reduces turn-off loss (Eoff) by 55% as compared to the conventional device. Furthermore, the change in the workfunction also provides the reduction of channel peak electric field and offers 10% increment in the BV as compared to the conventional IGBT.