GaN-based trench metal oxide Schottky barrier diode and preparation method thereof

Abstract

The invention relates to a GaN-based trench metal oxide Schottky barrier diode and a preparation method thereof. The structure of the device sequentially comprises an ohmic contact metal layer, namely a cathode, which covers a substrate from bottom to top; a GaN self-supporting substrate; an n-type lightly doped epitaxial layer; p-type high-concentration GaN layers which are arranged in parallel; a dielectric layer which is arranged in a trench; and a metal layer covering the upper surface of the device, i.e., an anode. The method comprises the following steps: forming a p-type high-concentration GaN layer through a selection region epitaxy method to obtain the p-type high-concentration GaN layer with high carrier concentration; depositing a dielectric layer, forming a contact hole in the dielectric layer, and connecting anode metal with the p-type high-concentration GaN layer through the contact hole to form ohmic contact. The p-type high-concentration GaN layer and the n-type lightly doped epitaxial layer at the bottom form a pn junction, so the anti-surge capability during forward conduction is greatly enhanced; meanwhile, the p-type high-concentration GaN layer under the dielectric layer can also reduce a high electric field at the corner of the dielectric layer, and the reliability of the dielectric layer and the breakdown voltage of the device are improved.

Description

technical field [0001] The invention belongs to the field of semiconductor power electronic devices, in particular to a GaN-based trench metal oxide Schottky barrier diode and a preparation method thereof. Background technique [0002] Schottky diodes have the advantages of forward voltage drop and high switching frequency, and are widely used in various fields of power electronics, such as switching power supplies and drive circuits. Traditional Schottky diodes are mostly made of Si materials. Silicon-based power devices have reached their theoretical limit, and the power density growth tends to be saturated, which can no longer meet people's needs for high-voltage and high-power density electronic products. GaN material has high critical breakdown field strength and high electron mobility, so it has a large Baliga figure of merit (BFOM), which can fundamentally break through the theoretical limit of Si devices in terms of physical characteristics. Therefore, the developme...

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Problems solved by technology

[0004] High-performance TMBS devices can achieve a good trade-off between forward conduction resistance and breakdown voltage. There have been some reports on GaN-based TMBS, but most of them focus on how to improve the breakdown voltage.

At present, the main problems faced by GaN-based TMBS are the following two points: 1. The electric field in the dielectric layer at the corner of the trench of GaN-based TMBS device is very large

Under long-term reverse bias voltage, this will cause the fatigue of the dielectric layer and cause unreliability; 2. Weak anti-surge ability

When power devices are used in practical electronic circuits, they often encounter current overshoot or oscillation, which can easily lead to device burnout

Since TMBS devices are unipolar devices, the conduction voltage drop will increase significantly when working in a state of high current density, resulting in reduced device surge reliability

In order to improve the stability of the overall circuit, it is often necessary to take anti-surge measures. The common measure is to use a surge protection device to bypass the surge to the ground through the protection device. However, the introduction of the protection device will increase the overall volume, which is not conducive to integration. Therefore, it is very important to improve the anti-surge capability of the TMBS device itself

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