A high-voltage fast soft recovery diode and its preparation method

Abstract

The invention relates to a high-voltage rapid-soft-recovery diode. The high-voltage rapid-soft-recovery diode comprises an active area and a terminal area. A p buffering layer, a p+ anode layer and an anode aluminum electrode are upwards arranged on the upper surface of an n-substrate layer of the active area in sequence. An active n buffering layer and a cathode aluminum electrode layer are downwards arranged in sequence with the lower surface of the n-substrate layer as the base. The high-voltage rapid-soft-recovery diode further comprises an active p+ adjusting area and two n+ cathode areas, wherein the active p+ adjusting area and the two n+ cathode areas are arranged between the active n buffering layer and the cathode aluminum electrode layer, two n+ cathode areas are equal in width, and the active p+ adjusting area is arranged between the two n+ cathode areas. According to the high-voltage rapid-soft-recovery diode, trenches are adopted by the upper surface of the terminal portion, a high-concentration area on the surface of a p-type field limiting ring is eliminated selectively, bending of a pn junction can be relieved, the surface electrical field can be reduced, the terminal breakdown voltage can be increased easily, and the terminal size is small; current concentration at the junction position of the active area and the terminal area in a breakover period can be easily relieved through the p+ adjusting area located on the lower surface of the terminal portion, and reverse recovery softness factors can be increased easily.

Description

technical field [0001] The invention relates to a structure of a high-voltage fast soft recovery diode and a preparation method thereof. Background technique [0002] A high-voltage fast soft recovery diode (FSRD) is a diode used for freewheeling in a circuit. It is usually a square chip structure and is packaged into a module with a high-voltage insulated gate bipolar transistor (IGBT). In practical applications, FSRD is required to have high withstand voltage, low loss, fast soft recovery characteristics and high reliability. [0003] In the development process of the high-voltage FSRD chip, there are two main technical problems: one is the optimization of the comprehensive characteristics. Due to the constraints of device structure parameters, there is a contradictory relationship between high blocking voltage, low on-state voltage drop and fast soft recovery characteristics, and it is difficult to obtain excellent comprehensive characteristics. Usually high withstand v...

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Problems solved by technology

[0003] In the development process of high-voltage FSRD chips, there are two main technical problems: one is the optimization of comprehensive characteristics

Due to the constraints of device structure parameters, there is a contradictory relationship between high blocking voltage, low on-state voltage drop and fast soft recovery characteristics, and it is difficult to obtain excellent comprehensive characteristics

Usually high withstand voltage and low on-state voltage drop can be achieved, but fast soft recovery cannot be guaranteed

For this reason, a uniform minority carrier lifetime control technology is adopted to improve the reverse recovery characteristics of the high-voltage FSRD, but this will lead to a significant increase in the high-temperature leakage current of the diode and its static power consumption

The second is the terminal problem

The active region uses p + no - nn + structure, at the anode p + district and n - area, cathode n + district and n - A low-concentration, thicker p-buffer layer and n-buffer layer are added between the regions; the terminal region adopts a conventional field-limiting ring structure, and the cathode side on the back is n + In this area, the electron injection efficiency is 1 to meet the requirements of high withstand voltage, low on-state voltage drop and fast recovery characteristics, but the reverse recovery softness and reliability cannot be guaranteed

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