Silicon carbide separation gate MOSFET cell of integrated gate-controlled diode and preparation method thereof

Abstract

The invention relates to a silicon carbide separation gate MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) cell integrated with a gate-controlled diode and a preparation method thereof, belonging to the technical field of power semiconductor devices. The MOSFET adopts a separation gate design to reduce the switching loss of the device; in order to solve the problem that the reliability of gate oxide is reduced due to a separation gate structure, a P-type buried layer is added to reduce the electric field intensity of a gate oxide layer at the edge of polycrystalline silicon; an N-type diversion layer is added, and current is introduced into a drift region of the device from a channel; in order to reduce the conduction voltage drop of a parasitic body diode of the silicon carbide MOSFET so as to reduce the reverse recovery current of the body diode, a grid control diode based on an accumulation type channel MOS structure is introduced to the other side of a cell of the MOSFET. According to the invention, the accumulation type channel is adopted to fully reduce the conduction loss of the diode, and the source electrode metal is in contact with the polycrystalline silicon of the grid control diode on the side wall by etching and filling the metal, so that the cell size is reduced.

Description

technical field [0001] The invention belongs to the technical field of power semiconductor devices, and in particular relates to a silicon carbide separated gate MOSFET cell with integrated gate-controlled diode and a preparation method thereof. Background technique [0002] The wide-bandgap semiconductor material SiC is an ideal material for the preparation of high-voltage power electronic devices. Compared with Si material, SiC material has a high breakdown electric field strength (4×10 6 V / cm), high carrier saturation drift velocity (2×10 7 cm / s), high thermal conductivity, good thermal stability, etc., so it is especially suitable for high-power, high-voltage, high-temperature and radiation-resistant electronic devices. [0003] SiC VDMOS is a commonly used device in SiC power devices. Compared with bipolar devices, since SiCVDMOS has no charge storage effect, it has better frequency characteristics and lower switching losses. At the same time, the wide band gap of SiC...

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Problems solved by technology

[0004] However, there are two problems in the planar SiC VDMOS. One is that the density of the JFET area is relatively high, which introduces a large Miller capacitance, which increases the dynamic loss of the device; the other is that the parasitic SiC body diode conduction voltage drop is too high. , and it is a bipolar device, which has a large reverse recovery current. In addition, the bipolar degradation phenomenon caused by the silicon carbide BPD defect makes the conduction voltage drop of the body diode continue to increase with the growth of service time. Therefore, The body diode of SiC VDMOS cannot be directly used as a freewheeling diode

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