Electrostatic protection structure

Abstract

The invention discloses an electrostatic protection structure comprising a first NPN (non-protein nitrogen) heterojunction transistor and a second NPN heterojunction transistor, wherein a base and a collector of the second NPN heterojunction transistor are connected with the collector with the first NPN heterojunction transistor, an emitter of the second NPN heterojunction transistor is taken as a static electricity entrance end, and the base and the emitter of the first NPN heterojunction transistor are short-connected and are used as a static electricity discharge end. According to the electrostatic protection structure disclosed by the invention, the second NPN heterojunction transistor is utilized for realizing a high-gain amplification factor, the first NPN heterojunction transistor is utilized for realizing high reverse voltage endurance capability, higher static electricity discharge capability can be ensured under the situation of not obviously increasing parasitic capacitance and the breakdown voltage is enhanced.

Description

technical field [0001] The invention relates to semiconductor electrostatic protection technology, in particular to an electrostatic protection structure. Background technique [0002] The structure used for electrostatic protection mainly uses heterojunction transistors as a silicon germanium process. [0003] NPN heterojunction transistors such as figure 1 As shown, an N-type buried layer, an N-type epitaxy, an N-type well, an N+ diffusion region, and two isolation walls are formed on the P-type substrate, wherein the N-type well and the N+ diffusion region are located in the same N-type epitaxial layer , the N+ diffusion region in the N-type epitaxy forms the collector, the N-type epitaxy is covered with P-type SiGe to form the base, and the SiGe material covered on the N-type epitaxy is covered with an emitter window, on which N-type polysilicon is deposited and Lead out from the pad to form the emitter. [0004] When common NPN heterojunction transistors are used for...

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Problems solved by technology

[0004] When common NPN heterojunction transistors are used for electrostatic protection, such as figure 2 As shown, the base is short-circuited with the emitter as one end, and the collector is used as the other end, which is connected between the input and output pins and the power supply or ground. The common NPN heterojunction transistor electrostatic protection structure is performing electrostatic discharge The short circuit between the base and the emitter is used as the end of the static electricity discharge, and the collector is used as the end of the static electricity entry. The disadvantage of this structure is that the opening of the triode during the electrostatic discharge is not through the emitter to the collector / The base is short-circuited to release, but the collector to the base / emitter is short-circuited to release, so that the magnification of the turned-on triode is much lower, resulting in a lower flow capacity per unit area, but once the area is increased, it will lead to parasitic increase in capacitance

[0005] NPN heterojunction transistors if used image 3 The electrostatic protection circuit shown, although the emitter-to-collector / base short-circuit discharge form is adopted, the parasitic capacitance is small, but the breakdown voltage of the emitter-to-base junction is low (only 1~2V), and it cannot Satisfy normal working application (3.3V)

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