Gallium nitride bidirectional device based on channel deep electrode and preparation method thereof

Abstract

According to the novel gallium nitride bidirectional device based on the channel deep electrode and the preparation method of the gallium nitride bidirectional device, the channel deep electrode is added beside the source electrode and the drain electrode in the preparation process, and the channel deep electrode is in contact with the two-dimensional electron gas channel and the buffer layer; the potential of the channel deep electrode is the same as the potential of the source electrode, and the potential of the substrate can be different from the potential of the source electrode, so that the influence of the back gate effect of the double-gate bidirectional device is optimized, the problems of threshold voltage drift, on-resistance rise and the like are avoided, and meanwhile, the problem of the back gate effect of a monolithic integrated half-bridge high-side power tube can be solved. Compared with a GaN-on-SOI process, the method has the advantages that the optimization of the back gate effect problem of a double-gate bidirectional device can be realized, the process of the channel deep electrode is not limited to a substrate with a buried layer medium and can be realized on a silicon-based substrate, and the dependence on the thickness of a box layer of a buried oxide layer in the SOI process is reduced. The method is lower in implementation difficulty, lower in cost and better in effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductors, and particularly relates to a gallium nitride bidirectional device based on a channel deep electrode and a preparation method thereof. BACKGROUND

[0002] Gallium nitride (GaN) HEMT is widely used in power supply, automotive electronics, 5G communication and other fields. GaN material has good physical and electrical properties, such as high temperature resistance, radiation resistance, wide band gap, high breakdown field, large electron saturation drift speed and the like. This makes GaN HEMT have high switching frequency, high power density, high operating temperature, small gate charge and low switching loss. Since the use of discrete GaN HEMT will introduce unnecessary parasitics, in order to release the full potential of GaN HEMT, the driving circuit, peripheral control and protection circuit need to be monolithically integrated with power GaN HEMT to achieve higher energy efficiency and reliability.

[0003] Based on the GaN-on-Si process, due to the existence of the back-gate effect, the threshold voltage of the high-side gallium nitride HEMT device in the monolithic integrated half-bridge will change greatly, which will cause stability problems. At the same time, the double-gate bidirectional device also suffers from the back-gate effect problem, resulting in unstable threshold voltage.

[0004] The traditional HEMT device often uses the method of shorting the substrate to the source to solve the stability problem caused by the back-gate effect, but this is impossible for double-gate devices. The active substrate lead electrode scheme can be used to switch the substrate potential instantaneously, but this inevitably increases the complexity of the circuit and causes additional power consumption.

[0005] The prior art also describes a GaN integrated half-bridge based on the GaN-on-SOI process, which uses a SiO2 filling trench technology to isolate the substrate of each device until the SiO2 buried layer of the SOI substrate, and then connects the source of the device to the top silicon layer of the SOI substrate of the respective active region through a deep electrode. However, this technology cannot solve the back-gate effect problem of the double-gate bidirectional device, because the double-gate device is a bidirectional conduction device, and its two sub-switches share a common substrate, so it is impossible for the two sources to be connected to the substrate at the same time. In addition, the performance of the SOI process-based device also depends on the thickness of the embedded oxide layer. Therefore, using the GaN-on-SOI process cannot solve the back-gate effect problem of the double-gate bidirectional device. SUMMARY

[0006] In order to solve the above problems in the prior art, the application provides a gallium nitride bidirectional device based on a channel deep electrode and a preparation method thereof. The technical problem to be solved by the application is solved by the following technical scheme: A gallium nitride bidirectional device based on a deep channel electrode, comprising, from bottom to top, a substrate, a nucleation layer, a buffer layer, a channel layer and a barrier layer, a source electrode and a gate p-GaN layer being arranged on both sides of the barrier layer with a predetermined interval, a gate metal being arranged on the single-sided gate p-GaN layer, and a deep channel electrode being arranged beside the source electrode and connected with the source electrode.

[0007] A preparation method of a gallium nitride bidirectional device based on a deep channel electrode, comprising: S100, selecting a substrate and depositing, on the substrate, a nucleation layer, a buffer layer, a channel layer, a barrier layer and a p-GaN layer in sequence; S200, etching away other areas on the p-GaN layer except the gate area to obtain a gate p-GaN layer, and etching a source trench downward beside the source electrode area on both sides of the barrier layer; S300, depositing a source metal in the source electrode area and the source trench and annealing; S400, depositing a gate metal on the gate p-GaN layer after annealing in S300 and annealing to obtain a gallium nitride bidirectional device based on a deep channel electrode.

[0008] Beneficial effects: The application provides a novel gallium nitride bidirectional device based on a deep channel electrode and a preparation method thereof. In the preparation process, a deep channel electrode is added beside the source electrode and the drain electrode. The deep channel electrode contacts the two-dimensional electron gas channel and the buffer layer. The potential of the deep channel electrode is the same as the potential of the source electrode, and the potential of the substrate can be different from the potential of the source electrode. The application not only optimizes the back gate effect of the double-gate bidirectional device, avoids threshold voltage drift and the increase of on-resistance, but also solves the back gate effect problem of the single-chip integrated half-bridge high-side power tube. Compared with the GaN-on-SOI process, the application can optimize the back gate effect of the double-gate bidirectional device, and the process of the deep channel electrode is not limited to the substrate with a buried dielectric layer. The process can be realized on a silicon-based substrate, reducing the dependence on the thickness of the buried oxide layer box in the SOI process. The application has lower realization difficulty, lower cost and better effect.

[0009] The application will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a schematic diagram of a gallium nitride bidirectional device based on a deep channel electrode provided by the application; Figure 2 is a schematic diagram of a gallium nitride HEMT device based on a deep channel electrode provided by the application; Figure 3This is a schematic diagram of a half-bridge structure based on source-drain channel deep electrode gallium nitride integration provided by the present invention; Figure 4 This is a schematic diagram of the process flow of a gallium nitride bidirectional device based on a deep trench electrode provided by the present invention; Figure 5 It is a schematic diagram of a device formed after completing S100 provided by the present invention. DETAILED DESCRIPTION

[0011] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0012] refer to Figure 1 As shown, the present invention provides a gallium nitride bidirectional device based on a deep trench electrode, comprising, from bottom to top, a substrate, a nucleation layer, a buffer layer, a channel layer, and a barrier layer, wherein a source and a gate p-GaN layer with a predetermined interval are respectively provided on both sides of the barrier layer, and a gate metal is provided on the gate p-GaN layer on one side, characterized in that a deep trench electrode is provided next to the source, and the deep trench electrode is connected to the source.

[0013] The length and depth of the deep trench electrode can be adjusted according to the size of the device. Of course, an insertion layer can be provided between the barrier layer and the channel layer of the present invention to improve carrier mobility. The insertion layer material can be any one of AlN, InAlN, and AlGaN.

[0014] The present invention provides a novel bidirectional gallium nitride device based on a deep trench electrode. A deep trench electrode is added next to the source electrode, allowing the substrate potential to be different from the source potential. This not only optimizes the back-gate effect problem of dual-gate bidirectional devices, but can also be used to solve the back-gate effect problem of monolithic integrated half-bridge high-side power transistors. Compared with the GaN-on-SOI process, the present invention can optimize the back-gate effect problem of dual-gate bidirectional devices. Furthermore, the process of the deep trench electrode is not limited to substrates with buried dielectrics and can be implemented on silicon-based substrates, reducing the reliance on the thickness of the buried oxide box layer in the SOI process. The present invention is less difficult to implement, has lower costs, and has better results.

[0015] Combine Figure 2 and Figure 3 The present invention also proposes to apply deep trench electrodes to GaN HEMT devices, that is, GaN HEMT devices based on source-drain deep electrode. GaN HEMT devices are designed with deep trench electrodes at both the source and drain to connect to the corresponding source or drain. A single HEMT device such as Figure 2 As shown, the half-bridge structure based on the source-drain channel deep electrode gallium nitride HEMT integration is as follows Figure 3 As shown. Figure 3The middle piece is isolated from the pieces, and the gate of the left piece is low-side driven, the gate of the right piece is high-side driven, the source and the drain of the right part are both designed with grooves, and the grooves are filled with metal to form deep channel electrodes.

[0016] For the bidirectional device, the deep channel electrode is added between the device isolation and the source electrode. For the GaN HEMT device, the deep channel electrode is added between the device isolation and the source (drain) electrode, the deep channel electrode contacts the two-dimensional electron gas channel and the buffer layer, the potential of the deep channel electrode is the same as that of the source electrode, and when the substrate potential and the source potential are different, the voltage difference between the substrate and the source is dropped to the buffer layer, without affecting the two-dimensional electron gas charge density, which can optimize the influence of the back gate effect, avoid threshold voltage drift, and increase the on-resistance, etc. The application can not only solve the back gate effect problem of the bidirectional blocking device, but also solve the back gate effect problem of the GaN HEMT device in single-chip integrated application.

[0017] Reference Figure 1 In Figure 1 , isolation is needed between multiple devices produced, so the isolation area is used to illustrate the positional relationship between the devices.

[0018] As Figure 4 indicated, the application provides a preparation method of a gallium nitride bidirectional device based on a deep channel electrode, which comprises the following steps: S100, selecting a substrate, and depositing a nucleation layer, a buffer layer, a channel layer, a barrier layer and a p-GaN layer on the substrate; The substrate is one of sapphire, SiC, Si, SOI and GaN, the material of the nucleation layer is one of GaN, AlN and AlGaN, the material of the buffer layer is one or more of GaN, AlN and AlGaN, and the material of the channel layer is one of GaN, AlN and AlGaN. x Ga (1- x) N, wherein the Al component is 0.1-0.5, and the deposition thickness of the barrier layer is 10-50 nm.

[0019] S200, etching other areas except the gate area on the p-GaN layer to obtain a gate p-GaN layer, and etching a source groove downward on both sides of the source area on the barrier layer; S300, depositing a source metal in the source area and the source groove, and annealing; S400, depositing a gate metal on the gate p-GaN layer after annealing in S300, and annealing to obtain a gallium nitride bidirectional device based on a deep channel electrode.

[0020] The gate metal is a metal combination of any one of Ni / Au, Ti / Al / Ti, TiN, and Pt / Au.

[0021] In one specific embodiment of the present application, referring to Figure 2 S100 includes: S110a, selecting a substrate, and depositing a nucleation layer of 10-500 nm on the substrate by MOCVD process; S120a, depositing a buffer layer of 2-8 μm and a channel layer of 10-500 nm on the nucleation layer by MOCVD process; S130a, depositing a barrier layer and a p-GaN layer of 10-300 nm on the channel layer by MOCVD process.

[0022] In one specific embodiment of the present application, S100 includes: S110b, selecting a substrate, and depositing a nucleation layer of 10-500 nm on the substrate by MOCVD process; S120b, depositing a buffer layer of 2-8 μm and a channel layer of 10-500 nm on the nucleation layer by MOCVD process; S130b, depositing a barrier layer of 10-50 nm on the channel layer by MOCVD process; S140b, depositing an insertion layer on the barrier layer, the material of the insertion layer being one of AlN, InAlN, and AlGaN; S150b, depositing a p-GaN layer of 10-300 nm on the insertion layer.

[0023] In one specific embodiment of the present application, S300 includes: S310, depositing a source metal in the source region and the source trench by E-Beam electron beam evaporation equipment; The source metal is a metal combination of Ti / Al / Ni / Au or Ti / Al / Pt / Au, and the gate metal is a metal combination of any one of Ni / Au, Ti / Al / Ti, TiN, and Pt / Au. S320, annealing the device after depositing the source metal or the drain metal at 850°C for 30 s to form a high-temperature ohmic contact, as shown in Figure 5 .

[0024] In one specific embodiment of the present application, after S400, the preparation method further includes: The sample obtained in S400 is put into a PECVD reaction chamber, and a PECVD process is used to deposit a 0-200 nm passivation layer of SiN, Al2O3 or SiO2 on the upper part of the barrier layer, the source electrode and the gate electrode.

[0025] The above description is further detailed in combination with specific preferred embodiments of the present application, and the specific implementation of the present application should not be limited to these descriptions. For those of ordinary skill in the art to which the present application belongs, several simple deductions or substitutions can be made without departing from the concept of the present application, and all of them should be considered as falling within the protection scope of the present application.

Claims

1. A bidirectional GaN device based on a deep trench electrode, comprising, from bottom to top, a substrate, a nucleation layer, a buffer layer, a channel layer, and a barrier layer, wherein a source and a gate p-GaN layer are provided on both sides of the barrier layer at predetermined intervals, and a gate metal is provided on one side of the gate p-GaN layer, characterized in that: A deep trench electrode is provided beside the source electrode, and the deep trench electrode is connected to the source electrode.

2. The gallium nitride bidirectional device based on deep trench electrode according to claim 1, characterized in that: The channel deep electrode has a variable depth, and its depth reaches at least to the channel layer.

3. The gallium nitride bidirectional device based on deep trench electrode according to claim 1, characterized in that: An insertion layer for improving carrier mobility is further inserted between the barrier layer and the channel layer, and the insertion layer is made of any one of AlN, InAlN and AlGaN.

4. A method for preparing a gallium nitride bidirectional device based on a deep trench electrode, characterized in that: include: S100, selecting a substrate, and sequentially depositing a nucleation layer, a buffer layer, a channel layer, a barrier layer, and a p-GaN layer on the substrate; S200, etching away the other regions of the p-GaN layer except the gate region to obtain a gate p-GaN layer, and etching source trenches downwards beside the source regions on both sides of the barrier layer; S300, depositing source metal in the source region and the source trench, and annealing; S400, after the annealing in S300, a gate metal is deposited on the gate p-GaN layer, and annealed to obtain a gallium nitride bidirectional device based on a deep trench electrode.

5. The method for preparing a gallium nitride bidirectional device based on a deep trench electrode according to claim 4, characterized in that: S100 includes: S110a, selecting a substrate and depositing a nucleation layer with a thickness of 10 to 500 nm on the substrate using an MOCVD process; S120a, sequentially depositing a buffer layer of 2 to 8 μm and a channel layer of 10 to 500 nm on the nucleation layer using an MOCVD process; S130a, depositing a barrier layer of 10-50 nm and a p-GaN layer of 10-300 nm on the channel layer using an MOCVD process.

6. The method for preparing a gallium nitride bidirectional device based on a deep trench electrode according to claim 5, characterized in that: The substrate is one of sapphire, SiC, Si, SOI and GaN; the material of the nucleation layer is one of GaN, AlN, AlGaN; the material of the buffer layer is one or more of GaN, AlN, AlGaN; the material of the channel layer is one of GaN, AlN, AlGaN.

7. The method for preparing a gallium nitride bidirectional device based on a deep trench electrode according to claim 4, characterized in that: S100 includes: S110b, selecting a substrate and depositing a nucleation layer with a thickness of 10 to 500 nm on the substrate using an MOCVD process; S120b, sequentially depositing a buffer layer of 2 to 8 μm and a channel layer of 10 to 500 nm on the nucleation layer using an MOCVD process; S130b, depositing a barrier layer with a thickness of 10 to 50 nm on the channel layer using an MOCVD process; S140b, depositing an insertion layer on the barrier layer, wherein the material of the insertion layer is one of AlN, InAlN, and AlGaN; S150b, depositing a p-GaN layer with a thickness of 10-300 nm on the insertion layer.

8. The method for preparing a gallium nitride bidirectional device based on a deep trench electrode according to claim 5 or 7, characterized in that: The composition of the barrier layer is Al x Ga (1- x) N, wherein the Al composition is 0.1~0.5 and the deposition thickness of the barrier layer is 10~50nm.

9. The method for preparing a gallium nitride bidirectional device based on a deep trench electrode according to claim 4, characterized in that: S300 includes: S310, depositing source metal in the source region and the source trench using an E-Beam electron beam evaporation device; The source metal is a metal combination of Ti / Al / Ni / Au or a metal combination of Ti / Al / Pt / Au; the gate metal is a metal combination of Ni / Au, Ti / Al / Ti, TiN, and Pt / Au; S320 , annealing the device after depositing the source metal or drain metal at 850° C. for 30 seconds to form a high-temperature ohmic contact.

10. The method for preparing a gallium nitride bidirectional device based on a deep trench electrode according to claim 4, characterized in that: After S400, the preparation method further includes: The sample obtained in S400 is placed in a plasma chemical vapor deposition (PECVD) reaction chamber, and a 0-200 nm SiN, Al2O3 or SiO2 passivation layer is deposited on the barrier layer, source electrode and gate electrode using the PECVD process.

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