Bi-directional insulated gate bipolar transistor (IGBT) device and fabrication method thereof

Abstract

The invention relates to a bi-directional insulated gate bipolar transistor (IGBT) device and a fabrication method thereof, belonging to the technical field of a power semiconductor device. A double-split electrode and a dielectric layer between the double-split electrode and gate electrodes are introduced to be arranged at the bottom and on the side surface of gate electrodes in trenches in the front surface and the back surface of the device, thus, the symmetric positive and negative characteristics are achieved on the condition that the threshold voltage of the IGBT device is not affected and the IGBT device is switched on, the positive and negative switching speeds of the bi-directional IGBT device are increased, and the switching loss of the device is reduced; the carrier concentration distribution of the whole N-type drift region is improved, and the positive conduction voltage drop and the average switching loss are improved; and the saturated current density of the device is reduced, the short-circuit safety working region of the device is improved, the concentration of an electric field at the bottom of the trench is improved, the breakdown voltage of the device is increased, and the reliability of the device is further improved. According to the fabrication method of the bi-directional IGBT, provided by the invention, no extra process step is needed, and the fabrication method is compatible with the fabrication method of a traditional bi-directional IGBT.

Description

technical field [0001] The invention belongs to the technical field of power semiconductor devices, and relates to an insulated gate bipolar transistor (IGBT), in particular to a bidirectional trench gate insulated gate bipolar transistor (Bi-directional trench IGBT). Background technique [0002] Insulated Gate Bipolar Transistor (IGBT) is a new type of power electronic device combining MOS field effect and bipolar transistor. It not only has the advantages of easy driving and simple control of MOSFET, but also has the advantages of low conduction voltage of power transistor, large on-state current and small loss. It has become one of the core electronic components in modern power electronic circuits and is widely used in Various fields of the national economy such as communications, energy, transportation, industry, medicine, household appliances and aerospace. The application of IGBT plays an extremely important role in improving the performance of power electronic syste...

AI Technical Summary

Problems solved by technology

However, for this bidirectional IGBT structure, when the forward or reverse IGBT works, the breakdown voltage of the device is significantly higher due to the higher doping concentration of the carrier storage layer and the existence of a certain thickness of the N-type layer 8 or 28. Reduce, in order to effectively shield the adverse effects of the N-type layer as the carrier storage layer and obtain a certain device withstand voltage, it is necessary to adopt: 1) deep trench gate depth, so that the depth of the trench gate is greater than the N-type layer 8 or 28 junction depth, but the deep trench gate depth not only increases the gate-emitter capacitance but also increases the gate-collector capacitance when working in either direction, thus reducing the switching speed of the device and increasing The switching loss of the device affects the compromise characteristics of the conduction voltage drop and switching loss of the device; 2) The small cell width makes the distance between the trench gates as small as possible, however, when working in any direction, the high The dense trench MOS structure not only increases the gate capacitance of the device, reduces the switching speed of the device, increases the switching loss of the device, and affects the compromise characteristics of the conduction voltage drop and switching loss of the device, but also, high The dense trench MOS structure increases the saturation current density of the device, making the short-circuit safe working area of ​​the device worse

Additionally, for figure 1 and 2 In the bidirectional IGBT structure shown, the gate oxide layer is formed in the trench by one-time thermal oxidation. In order to ensure a certain threshold voltage, the thickness of the entire gate oxide layer is small. Since the MOS capacitance is inversely proportional to the thickness of the oxide layer, traditional The small gate oxide thickness in the bidirectional IGBT structure greatly increases the gate capacitance of the device

In addition, the small gate oxide thickness concentrates the electric field at the bottom of the trench, making the device less reliable

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