CN-114830354-B - Schottky barrier diode

CN114830354BCN 114830354 BCN114830354 BCN 114830354BCN-114830354-B

Abstract

The invention aims to prevent dielectric breakdown caused by misalignment between a trench and a field insulating layer in a Schottky barrier diode of gallium oxide. The Schottky barrier diode is provided with an anode electrode (40) which is in Schottky contact with a drift layer (30), a cathode electrode (50) which is in ohmic contact with a semiconductor substrate (20), an insulating film (63) which covers the inner wall of a trench (61) provided in the drift layer (30), a metal film (64) which covers the inner wall of the trench (61) through the insulating film (63) and is electrically connected to the anode electrode (40), and a field insulating layer (70). The field insulating layer (70) includes a first portion (71) located between the upper surface (31) of the drift layer (30) and the anode electrode (40), and a second portion (72) covering the inner wall of the trench (61) with the metal film (64) and the insulating film (63) therebetween. Thus, even if the alignment of the trench (61) and the field insulating layer (70) is deviated, dielectric breakdown does not occur.

Inventors

FUJITA AKIRA
Yuzuru
KAWASAKI KATSUMI
Ping Linrun

Assignees

TDK株式会社

Dates

Publication Date: 20260505
Application Date: 20201005
Priority Date: 20191218

Claims (3)

1. A Schottky barrier diode is characterized in that, The device is provided with: A semiconductor substrate composed of gallium oxide; A drift layer composed of gallium oxide and provided on the semiconductor substrate; an anode electrode in schottky contact with the drift layer; A cathode electrode in ohmic contact with the semiconductor substrate; an insulating film covering an inner wall of the annular outer circumferential trench provided in the drift layer; a metal film covering the inner wall of the outer peripheral groove via the insulating film and electrically connected to the anode electrode, and The field-insulating layer is provided with a layer of silicon, The field insulating layer includes a first portion located between an upper surface of the drift layer and the anode electrode, and a second portion covering at least a portion located at an outer periphery and a bottom portion of the inner wall of the outer peripheral trench via the metal film and the insulating film electrically connected to the anode electrode.
2. The schottky barrier diode of claim 1 wherein, A center trench formed in a region surrounded by the outer peripheral trench is further provided in the drift layer, The first portion of the field insulating layer is annularly disposed so as to surround the outer peripheral trench.
3. The schottky barrier diode of claim 1 or 2, The first portion and the second portion are composed of mutually different insulating materials.

Description

Schottky barrier diode Technical Field The present invention relates to a schottky barrier diode, and more particularly, to a schottky barrier diode using gallium oxide. Background The schottky barrier diode is a rectifier element using a schottky barrier generated by bonding a metal and a semiconductor, and has a feature of low forward voltage and high switching speed compared to a normal diode having a PN junction. Therefore, schottky barrier diodes are sometimes used as switching elements for power devices. When a schottky barrier diode is used as a switching element for a power device, a sufficient reverse withstand voltage needs to be ensured, and therefore silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga 2O3), or the like having a larger band gap may be used instead of silicon (Si). Among them, gallium oxide has a very large band gap of 4.8 to 4.9ev and a dielectric breakdown field of about 8MV/cm, and therefore, a schottky barrier diode using gallium oxide is very promising as a switching element for a power device. Examples of schottky barrier diodes using gallium oxide are described in patent documents 1 and 2. The schottky barrier diode described in patent documents 1 and 2 has a field plate structure in which a plurality of trenches are provided in a gallium oxide layer, and a field insulating layer is provided between the gallium oxide layer and an outer peripheral portion of an anode electrode. If a plurality of trenches are provided in the gallium oxide layer in this way, the mesa region between the trenches becomes a depletion layer when a reverse voltage is applied, and thus the channel region of the drift layer is pinched off. Thus, leakage current when a reverse voltage is applied can be greatly suppressed. Further, since the field plate structure is provided, electric field concentration at the end portion of the anode electrode is relaxed. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2017-199869 Patent document 2 Japanese patent application laid-open No. 2019-79984 Disclosure of Invention Technical problem to be solved by the invention However, since the formation of the trench and the patterning of the field insulating layer are performed in separate steps, misalignment occurs between the formation positions of the two. Therefore, it is difficult to accurately align the end of the field insulating layer with the end of the trench. Further, if the end of the field insulating layer is offset outward from the end of the trench, the anode electrode and the semiconductor layer may directly contact each other in the region outside the trench, and dielectric breakdown may occur in this portion. On the other hand, in the case where the end portion of the field insulating layer is offset inward from the end portion of the trench, a part of the field insulating layer is formed inside the trench. In this case, in the field insulating layer formed inside the trench, an electric field concentrates on a corner portion which becomes a boundary between a portion covering the sidewall of the trench and a portion covering the bottom of the trench, and dielectric breakdown may occur. Accordingly, an object of the present invention is to prevent dielectric breakdown due to misalignment between a trench and a field insulating layer in a schottky barrier diode using gallium oxide. Means for solving the technical problems The Schottky barrier diode is characterized by comprising a semiconductor substrate composed of gallium oxide, a drift layer composed of gallium oxide and arranged on the semiconductor substrate, an anode electrode in Schottky contact with the drift layer, a cathode electrode in ohmic contact with the semiconductor substrate, an insulating film covering the inner wall of a trench arranged on the drift layer, a metal film covering the inner wall of the trench through the insulating film and electrically connected with the anode electrode, and a field insulating layer, wherein the field insulating layer comprises a first part positioned between the upper surface of the drift layer and the anode electrode and a second part covering the inner wall of the trench through the metal film and the insulating film. According to the present invention, the field insulating layer enters the inside of the trench, and therefore, the anode electrode and the drift layer are not directly connected to each other in the outer region of the trench. Further, since the metal film is present between the second portion of the field insulating layer and the insulating layer and has the same potential as the anode electrode, the electric field applied to the second portion of the field insulating layer can be greatly relaxed. Thereby, dielectric breakdown due to misalignment of the trench and the field insulating layer can be prevented. In the present invention, the trench may include an outer circumferential trench formed in an annular shape and a ce