A trench gate charge storage type igbt and its manufacturing method

Abstract

A trench gate charge storage type IGBT belongs to the technical field of semiconductor power devices. By widening the traditional trench gate structure and adopting the sidewall gate electrode structure to form a mesa structure under the base region, and introducing a shielding trench structure that shields the electric field of the charge storage layer, the carrier injection enhancement effect is increased, Improves the forward conduction voltage drop V ceon and turn-off loss E off The compromise between; alleviate the electric field concentration effect at the sharp corner of the bottom of the trench, effectively improve the breakdown voltage of the device; reduce the gate capacitance of the device, especially the Miller capacitance C GC and the gate charge Q G , improve the switching speed of the device, reduce the switching loss of the device and the requirements for the gate drive circuit capability; avoid the limitation of the doping concentration and thickness of the N-type charge storage layer on the device withstand voltage; reduce the saturation current density and improve the The short-circuit safe operating area (SCSOA) of the device; and effectively suppress the EMI effect when the device is turned on. In addition, the manufacturing method provided by the invention is compatible with the traditional trench gate charge storage type IGBT manufacturing method.

Description

technical field [0001] The invention belongs to the technical field of power semiconductor devices, in particular to a trench gate charge storage type insulated gate bipolar transistor (CSTBT). Background technique [0002] Insulated Gate Bipolar Transistor (IGBT) was proposed on the basis of research on power MOSFET, BJT and SCR / GTO, etc. In the late 1970s and early 1980s, it was invented by introducing a PN junction into the back substrate of the power MOSFET structure and achieve mass production. The conductance modulation effect introduced by the PN junction on the back of the device when the device is turned on makes the IGBT a new type of power electronic device that is composed of a MOS field effect transistor and a bipolar junction transistor (BJT), and can also be equivalent to a bipolar junction transistor (BJT). ) driven MOSFET structure. IGBT combines the characteristics of both MOSFET and BJT: not only has the advantages of high input impedance, low control po...

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Problems solved by technology

[0006] The implementation of method (1) will increase the gate-emitter capacitance and gate-collector capacitance at the same time, and the switching process of the IGBT is essentially the process of charging / discharging the gate capacitance, so the increase in the gate capacitance will Makes the charging / discharging time longer, which in turn causes the switching speed to decrease

Therefore, the deep trench gate depth will reduce the switching speed of the device, increase the switching loss of the device, and affect the compromise characteristics of the device's conduction voltage drop and switching loss; and the implementation of method (2) will increase the device's switching loss The gate capacitance will reduce the switching speed of the device and increase the switching loss, which will affect the compromise between the conduction voltage drop and switching loss of the device. On the other hand, the large channel density will also increase the saturation current density of the device, making the device short-circuit safe. Work Area (SCSOA) Deterioration

In addition, the gate oxide layer in the trench gate structure is formed in the trench by one thermal oxidation. In order to ensure a certain threshold voltage, the thickness of the entire gate oxide layer is required to be small. However, the MOS capacitance and the thickness of the oxide layer Inversely proportional to this, this makes the gate capacitance in the traditional CSTBT device significantly increased, and the electric field concentration effect at the bottom of the trench will reduce the breakdown voltage of the device, resulting in poor reliability of the device

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