Enhanced gallium nitride vertical device with bidirectional conduction function and preparation method thereof

Abstract

The application discloses an enhanced gallium nitride vertical device with bidirectional conduction function and a manufacturing method, and mainly solves the problems of low withstand voltage and poor heat dissipation of the existing GaN device in bidirectional application. The device comprises a substrate, a buffer layer, a channel layer, a barrier layer, a gate p-GaN layer, a passivation layer, a gate electrode, a source electrode and a source trench. The source electrodes are symmetrically arranged on both sides of the substrate, and high-concentration and low-concentration n-type polarization gradient AlGaN layers are arranged in the active trenches above the source electrodes from bottom to top, and the two layers form a vertical current channel; the high-concentration layer forms a low-resistance ohmic contact with the source electrode through a steep Al component gradient; the low-concentration layer has a gentle Al component gradient, the top Al component of which is matched with the barrier layer, and is used for bearing a reverse voltage and optimizing a longitudinal electric field. The application forms a bidirectional conduction path of'vertical-horizontal-vertical' and a double-side vertical heat dissipation path, can realize high withstand voltage, high efficiency and high reliability in the same area, and can be used for AC switches, bridge circuits and bidirectional DC-DC converters.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, specifically an enhanced gallium nitride vertical device with bidirectional conduction function and its fabrication method, which can be used in modules such as AC switches, bridge circuits and bidirectional DC-DC converters. Background Technology

[0002] With the rapid development of electric vehicles, data center energy systems, and renewable energy conversion, the demand for efficient and compact bidirectional power switches is increasing dramatically. These switches are widely used in key topologies such as AC switches, bridge circuits, and bidirectional DC-DC converters. Currently, traditional silicon-based devices face performance bottlenecks in high-frequency bidirectional applications. Although GaN high electron mobility transistors have shown certain advantages, the mainstream lateral structure still suffers from inherent limitations such as voltage withstand capability and area, concentrated electric field, and poor heat dissipation. In recent years, while some research has shifted towards vertical structures to address these needs, this often brings new challenges such as increased process complexity, difficulty in achieving enhanced operation, or excessively high costs. Therefore, the industry urgently needs a new bidirectional GaN device solution that can balance high voltage, high efficiency, normally-off characteristics, low cost, and good heat dissipation performance.

[0003] Patent application number 202510844606.1 discloses a gallium nitride bidirectional device based on a deep-channel electrode and its fabrication method. Based on the traditional lateral device structure, it introduces deep-channel electrodes next to the source electrodes on both sides. These electrodes are connected to the source electrodes and extend downwards to the channel layer and even the buffer layer. Their main function is to optimize the back-gate effect by fixing the channel potential, thereby improving the stability of the threshold voltage. However, its fundamentally lateral conductive structure determines that it cannot meet the core requirements of the industry for next-generation solutions, mainly in the following aspects:

[0004] Firstly, achieving high voltage still relies on increasing chip size, which restricts the improvement of power density and cannot meet the needs of efficient and compact systems.

[0005] Secondly, the problem of electric field concentration at the gate edge still exists, thus threatening long-term reliability.

[0006] Third, the heat source being located on the surface of the device limits the device's heat dissipation efficiency. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of the prior art by proposing an enhanced gallium nitride vertical device with bidirectional conduction function and its fabrication method, so as to improve breakdown voltage, heat dissipation efficiency and reliability, and achieve high voltage withstand, high efficiency and high reliability bidirectional power switching performance.

[0008] The technical approach to achieving the objective of this invention is as follows: By placing the source electrode on both sides of the substrate, and setting a vertical conductive channel above the source electrode, consisting of a high-concentration n-type polarization gradient AlGaN layer and a low-concentration n-type polarization gradient AlGaN layer, this channel is connected to the AlGaN barrier layer above and the two-dimensional electron gas channel, forming a vertical-lateral-vertical bidirectional conduction path. This path allows the device's withstand voltage to be shared by the lateral gate-source distance and the vertical gradient AlGaN layer, thereby achieving high-voltage bidirectional blocking within a small chip area and improving power density. Simultaneously, the core region bearing the high voltage is transferred from the gate edge to the vertical junction region within the bulk, and the vertical electric field distribution is optimized through the gradient change of Al composition, suppressing electric field concentration and charge trapping, and improving device reliability. Furthermore, the vertical conductive channels on both sides constitute a dual-sided heat dissipation path from the active region to the substrate, significantly reducing thermal resistance and improving heat dissipation performance, ultimately achieving high withstand voltage, high efficiency, and high reliability bidirectional power switching performance.

[0009] Based on the above approach, the implementation scheme of the present invention includes:

[0010] 1. An enhancement-mode gallium nitride vertical device with bidirectional conduction function, comprising: a substrate, a buffer layer, a channel layer, a barrier layer, a gate p-GaN layer, a passivation layer, a gate electrode, a source electrode, and a source trench, characterized in that:

[0011] The source electrode is located on the left and right sides of the substrate, so that the current flows along vertical, lateral and vertical paths when it is turned on, and forms a double vertical heat dissipation path from the active area to the substrate.

[0012] The source trench is located on the upper surface of the source electrode, and its top is connected to the lower surface of the barrier layer. Inside it are a high-concentration n-type polarized graded AlGaN layer and a low-concentration n-type polarized graded AlGaN layer, which together form a vertical current channel. The high-concentration n-type polarized graded AlGaN layer is used to form a low-resistance ohmic contact, and the low-concentration n-type polarized graded AlGaN layer is used to withstand reverse voltage and optimize the longitudinal electric field distribution.

[0013] Furthermore, the high-concentration n-type polarized gradient AlGaN layer is located in the lower half of the source trench, with its lower surface in contact with the upper surface of the source electrode. The Al composition increases rapidly from 0% to 10%~15%. This steep composition gradient induces a high concentration of two-dimensional electron gas through the polarization effect, achieving low-resistance ohmic contact with the source electrode and providing a low-resistance inlet for the vertical current channel.

[0014] Furthermore, the low-concentration n-type polarized gradient AlGaN layer is located on the upper surface of the high-concentration n-type polarized gradient AlGaN layers on both sides. Its Al composition increases slowly from 10%~15% to 20%~30%, and the Al composition at the top matches the Al composition in the barrier layer. This gentle composition gradient induces the generation of a low-concentration two-dimensional electron gas through the polarization effect, thereby improving the longitudinal breakdown voltage of the device.

[0015] 2. A method for fabricating an enhanced gallium nitride vertical device with bidirectional conduction function, characterized in that it includes:

[0016] S1) Clean the selected substrate to obtain a clean epitaxial growth surface;

[0017] S2) On the cleaned substrate, a buffer layer, a channel layer, a barrier layer and a p-GaN layer are epitaxially grown sequentially by metal-organic chemical vapor deposition (MOCVD).

[0018] S3) Using inductively coupled plasma etching (ICP) technology, deep trench etching is performed on the left and right sides of the substrate until the surface of the barrier layer is etched, forming two source trenches.

[0019] S4) A low-concentration n-type polarization gradient AlGaN layer is epitaxially grown on the surface of the barrier layer etched in S3) by metal-organic chemical vapor deposition (MOCVD).

[0020] S5) A high-concentration n-type polarization gradient AlGaN layer is epitaxially grown on the surface of a low-concentration n-type polarization gradient AlGaN layer using a metal-organic chemical vapor deposition (MOCVD) process.

[0021] S6) A Ti / Al / Ni / Au metal stack is deposited on the surface of a high-concentration n-type polarized gradient AlGaN layer using an electron beam evaporation deposition apparatus, and then the source electrode is formed by rapid thermal annealing in a nitrogen atmosphere.

[0022] S7) Using inductively coupled plasma etching (ICP) technology, the p-GaN layer is selectively removed, leaving two centrally symmetrical strip regions on the left and right sides of the device to form two gate p-GaN layers.

[0023] S8) Two gate electrodes are formed by depositing a Ni / Au or Pt / Au metal stack on the upper surface of the gate p-GaN layer using an electron beam evaporation deposition device.

[0024] S9) Using plasma-enhanced chemical vapor deposition (PECVD) technology, passivation layers are deposited on both sides of each gate electrode and the gate p-GaN layer to complete the device fabrication.

[0025] Compared with existing methods, the present invention has the following advantages:

[0026] Firstly, by constructing a unique vertical-lateral-vertical composite conductive and voltage-resistant structure, this invention transforms the voltage withstand capability of the device from solely relying on the lateral gate-source distance to being jointly supported by the lateral distance and the vertically gradient AlGaN channel. The gradient-changing Al component can modulate the electric field, achieving higher voltage withstand and lower specific on-resistance than a pure lateral structure within the same chip area, thereby improving the power density of the device.

[0027] Secondly, this invention shifts the high-voltage-bearing body from the gate edge, where electric field concentration is prone to occur, to the gradient AlGaN vertical junction region within the bulk. Through its gradient Al composition design, polarization charges are induced, optimizing the longitudinal electric field distribution and making the electric field distribution more flat and uniform. This effectively suppresses local peak electric fields, reduces the risk of premature device breakdown, and mitigates charge trapping and dynamic resistance degradation caused by strong electric fields, ensuring the long-term stability of the device in bidirectional switching applications.

[0028] Thirdly, this invention utilizes n-type gradient AlGaN vertical channels on both sides to construct a heat conduction path between the surface heating channel and the bottom substrate. This path, constructed from a single-crystal semiconductor material, avoids the additional thermal resistance caused by lateral heat diffusion and crossing multiple heterojunctions in traditional structures. It provides a more efficient way to remove heat, effectively reducing the operating junction temperature and improving its thermal reliability and long-term operational stability in high-power-density applications. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0030] Figure 2 This is a schematic diagram illustrating the manufacturing process of the device of the present invention. Detailed Implementation

[0031] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] Reference Figure 1 This invention relates to an enhanced gallium nitride vertical device with bidirectional conduction function, comprising a substrate 1, a buffer layer 2, a channel layer 3, a barrier layer 4, a gate p-GaN layer 5, a passivation layer 6, a gate electrode 7, a source electrode 8, a source trench 9, a high-concentration n-type polarized gradient AlGaN layer 10, and a low-concentration n-type polarized gradient AlGaN layer 11, wherein:

[0033] The substrate 1 is made of any one of silicon, silicon carbide or sapphire substrate, and its thickness is 200μm~1000μm;

[0034] The buffer layer 2, located on the substrate 1, is made of AlGaN or GaN material and has a thickness of 1μm~5μm. It is used to alleviate the lattice mismatch and thermal mismatch between the substrate and the nitride epitaxial layer.

[0035] The channel layer 3 is located above the buffer layer 2 and is made of GaN material with a thickness of 50nm~500nm.

[0036] The barrier layer 4 is located above the channel layer 3. It is made of AlGaN material with a thickness of 10nm~30nm and an aluminum composition of 20%~30%.

[0037] The gate p-GaN layer 5 is located on both sides above the barrier layer 4, with a thickness of 50nm~300nm and a Mg doping concentration of 1×10⁻⁶. 19 cm -3 ~1×10 20 cm -3 ;

[0038] The passivation layer 6 is located on the left and right sides of the two gate p-GaN layers 5 and the gate electrode 7, and it is made of SiO2 or Si3N4 material.

[0039] The gate electrode 7 is located on the upper surface region of the two gate p-GaN layers 5, and it adopts a Ni / Au or Pt / Au metal stack.

[0040] The source electrode 8 is located on the left and right sides of the substrate 1. It adopts a Ti / Al / Ni / Au metal stack. This design allows the current to flow along vertical, lateral and vertical paths when it is turned on, and forms a double vertical heat dissipation path from the active area to the substrate.

[0041] The source trench 9 is located on the upper surface of the source electrode 8, and its top is connected to the lower surface of the barrier layer 4. It contains a high-concentration n-type polarized gradient AlGaN layer 10 and a low-concentration n-type polarized gradient AlGaN layer 11, which together form a vertical current channel.

[0042] The high-concentration n-type polarized gradient AlGaN layer 10 is located in the lower half of the source trench 9, with its lower surface in contact with the upper surface of the source electrode 8. Its thickness is 10nm~100nm, and the Al composition increases rapidly from 0% to 10%~15%. This steep composition gradient induces a high concentration of two-dimensional electron gas through the polarization effect, achieving low-resistance ohmic contact with the source electrode 8 and providing a low-resistance inlet for the vertical current channel.

[0043] The low-concentration n-type polarized gradient AlGaN layer 11 is located on the upper surface of the high-concentration n-type polarized gradient AlGaN layers 10 on both sides. Its thickness is 1μm~5μm, and the Al composition gradually increases from 10%~15% to 20%~30%. The Al composition at its top matches the Al composition in the barrier layer 4. The sum of the thickness of this layer and the high-concentration n-type polarized gradient AlGaN layer 10 is equal to the sum of the thickness of the buffer layer 2 and the channel layer 3, ensuring the high flatness of the epitaxial layer. In addition, this gentle Al composition gradient induces a low-concentration two-dimensional electron gas through the polarization effect, which is used to optimize the longitudinal electric field distribution and improve the longitudinal breakdown voltage of the device.

[0044] refer to Figure 2 This invention provides the following three embodiments for fabricating enhanced gallium nitride vertical devices with bidirectional conduction:

[0045] Example 1: A GaN buffer layer 2 with a thickness of 1 μm is grown on a silicon substrate 1 with a thickness of 200 μm; a GaN channel layer 3 with a thickness of 50 nm; an AlGaN barrier layer 4 with a thickness of 10 nm and an Al composition of 20%; a high-concentration n-type polarization gradient AlGaN layer 10 with a thickness of 10 nm and an Al composition increasing from 0% to 10%; a low-concentration n-type polarization gradient AlGaN layer 11 with a thickness of 1.04 μm and an Al composition increasing from 10% to 20%; and a gate p-GaN layer 5 with a thickness of 50 nm and an Mg doping concentration of 1 × 10⁻⁶. 19 cm -3 An enhanced gallium nitride vertical device with bidirectional conduction capability.

[0046] Step 1, substrate cleaning.

[0047] A silicon substrate 1 with a thickness of 200 μm was selected and ultrasonically cleaned for 10 minutes each with acetone, anhydrous ethanol and deionized water to remove organic and particulate contaminants. It was then rinsed with a large amount of deionized water and dried with nitrogen to obtain a clean and contamination-free epitaxial growth surface.

[0048] Step 2: Epitaxially grow a buffer layer, a channel layer, a barrier layer, and a p-GaN layer.

[0049] 2.1) Under the conditions of a temperature of 1080℃, a reaction chamber pressure of 400 Torr, a trimethylgallium flow rate of 50 sccm, an ammonia flow rate of 6000 sccm, and a hydrogen flow rate of 8000 sccm, a GaN buffer layer 2 with a thickness of 1 μm was epitaxially grown on a cleaned silicon substrate 1 by MOCVD process.

[0050] 2.2) Under the conditions of a temperature of 1050℃, a reaction chamber pressure of 300 Torr, a trimethylgallium flow rate of 100 sccm, an ammonia flow rate of 8000 sccm, and a hydrogen flow rate of 8000 sccm, a GaN channel layer 3 with a thickness of 50 nm was epitaxially grown on the GaN buffer layer 2 by MOCVD process.

[0051] 2.3) Under the conditions of a temperature of 1050℃, a reaction chamber pressure of 150 Torr, a trimethylgallium flow rate of 90 sccm, a trimethylaluminum flow rate of 10 sccm, an ammonia flow rate of 10000 sccm, and a hydrogen flow rate of 6000 sccm, an AlGaN barrier layer 4 with a thickness of 10 nm and an Al composition of 20% was epitaxially grown on the GaN channel layer 3 by MOCVD process.

[0052] 2.4) Under the conditions of a temperature of 1000℃, a reaction chamber pressure of 100 Torr, a trimethylgallium flow rate of 150 sccm, a dicyclopentadienylmagnesium flow rate of 200 sccm, a nitrogen flow rate of 8000 sccm, and an ammonia flow rate of 4000 sccm, a 50 nm thick Mg doping concentration of 1×10⁻⁶ was epitaxially grown on AlGaN barrier layer 4 using MOCVD process. 19 cm -3 The p-GaN layer.

[0053] Step 3, source trench etching.

[0054] Under the conditions of cavity pressure of 0.8 Pa, ICP source power of 800 W, bias power of 100 W, chlorine flow rate of 15 sccm, boron trichloride flow rate of 10 sccm, and argon flow rate of 10 sccm, deep trench etching is performed on the left and right sides of substrate 1 using inductively coupled plasma etching technology until the surface of barrier layer 4 is etched, forming two source trenches 9.

[0055] Step 4: Grow a low-concentration n-type polarized gradient AlGaN layer.

[0056] Under the conditions of a temperature of 1020℃, a reaction chamber pressure of 150 Torr, a trimethylgallium flow rate linearly increasing from 90 sccm to 95 sccm, a trimethylaluminum flow rate linearly decreasing from 10 sccm to 5 sccm, an ammonia flow rate of 10000 sccm, and a hydrogen flow rate of 6000 sccm, a low-concentration n-type polarized gradient AlGaN layer 11 with an Al composition increasing from 10% to 20% from bottom to top was epitaxially grown on the surface of the barrier layer after etching in step 3 by MOCVD process.

[0057] Step 5: Grow a high-concentration n-type polarized gradient AlGaN layer.

[0058] Under the conditions of a temperature of 1020℃, a reaction chamber pressure of 150 Torr, a trimethylgallium flow rate linearly increasing from 95 sccm to 100 sccm, a trimethylaluminum flow rate linearly decreasing from 5 sccm to 0 sccm, an ammonia flow rate of 10000 sccm, and a hydrogen flow rate of 6000 sccm, a high-concentration n-type polarized gradient AlGaN layer 10 with a thickness of 10 nm and an Al composition increasing from 0% to 10% from bottom to top was epitaxially grown on a low-concentration n-type polarized gradient AlGaN layer 11 using MOCVD process.

[0059] Step 6, depositing the source electrode.

[0060] 6.1) Under the conditions of an electron beam current of 280 mA and a deposition rate of 1.5 Å / s, an electron beam evaporation apparatus was used to deposit a Ti / Al / Ni / Au metal stack as a source electrode on two high-concentration n-type polarization gradient AlGaN layers 10.

[0061] 6.2) After deposition, rapid thermal annealing is performed in a nitrogen atmosphere at a temperature of 875°C for 30 seconds to form good ohmic contact.

[0062] Step 7: Etch the p-GaN layer.

[0063] Under the conditions of reaction chamber pressure of 1.2 Pa, ICP power of 600 W, and bias power of 80 W, the p-GaN layer was selectively removed using inductively coupled plasma etching technology. Two centrally symmetrical strip regions were retained on the left and right sides of the device to form two gate p-GaN layers 5.

[0064] Step 8: Deposit the gate electrode.

[0065] Under the conditions of an electron beam current of 300 mA and a deposition rate of 2.0 Å / s, an electron beam evaporation apparatus was used to deposit a Ni / Au metal stack on two gate p-GaN layers 5 to form gate electrodes 7.

[0066] Step 9: Deposit a passivation layer.

[0067] Under conditions of 300℃, 160Pa reaction chamber pressure, 15sccm silane flow rate, and 950sccm nitrous oxide flow rate, plasma-enhanced chemical vapor deposition (PECVD) was used to deposit SiO2 passivation layers 6 on both sides of each gate electrode 7 and the gate p-GaN layer 5, thus completing the device fabrication.

[0068] Example 2: On a 650 μm thick sapphire substrate 1, a 2.5 μm thick AlGaN buffer layer 2; a 200 nm thick GaN channel layer 3; a 20 nm thick AlGaN barrier layer 4 with an Al composition of 25%; a 50 nm thick high-concentration n-type polarization gradient AlGaN layer 10 with an Al composition increasing from 0% to 12%; a 2.65 μm thick low-concentration n-type polarization gradient AlGaN layer 11 with an Al composition increasing from 12% to 25%; and a 150 nm thick gate p-GaN layer 5 with a Mg doping concentration of 5 × 10⁻⁶. 19 cm -3 An enhanced gallium nitride vertical device with bidirectional conduction capability.

[0069] Step 1: Substrate cleaning.

[0070] The selected sapphire substrate 1 with a thickness of 650 μm was cleaned by ultrasonic cleaning with acetone, anhydrous ethanol and deionized water for 10 minutes each to remove organic and particulate contaminants. It was then rinsed with a large amount of deionized water and dried with nitrogen to obtain a clean and contamination-free epitaxial growth surface.

[0071] Step 2: Epitaxial growth of buffer layer, channel layer, barrier layer and p-GaN layer.

[0072] 2-1) An AlGaN buffer layer 2 with a thickness of 2.5 μm was epitaxially grown on a cleaned sapphire substrate 1 using MOCVD process. The process conditions were: temperature 1070℃, reaction chamber pressure 350 Torr, trimethylgallium flow rate 80 sccm, trimethylaluminum flow rate 20 sccm, ammonia flow rate 7000 sccm, and hydrogen flow rate 9000 sccm.

[0073] 2-2) A GaN channel layer 3 with a thickness of 200 nm was epitaxially grown on the AlGaN buffer layer 2 by MOCVD process. The process conditions were: temperature 1040℃, reaction chamber pressure 250 Torr, trimethylgallium flow rate 110 sccm, ammonia flow rate 9000 sccm, and hydrogen flow rate 9000 sccm.

[0074] 2-3) An AlGaN barrier layer 4 with a thickness of 20 nm and an Al composition of 25% was epitaxially grown on the GaN channel layer 3 by MOCVD process. The process conditions were: temperature 1040℃, reaction chamber pressure 120 Torr, trimethylgallium flow rate 85 sccm, trimethylaluminum flow rate 15 sccm, ammonia flow rate 12000 sccm, and hydrogen flow rate 7000 sccm.

[0075] 2-4) A p-GaN layer with a thickness of 150 nm and a Mg doping concentration of 5 × 10⁻⁶ was epitaxially grown on the AlGaN barrier layer 4 using MOCVD. 19 cm -3 The process conditions are as follows: temperature 990℃, reaction chamber pressure 80 Torr, trimethylgallium flow rate 160 sccm, dicyclopentadienylmagnesium flow rate 300 sccm, nitrogen flow rate 9000 sccm, ammonia flow rate 3500 sccm.

[0076] Step 3: Source trench etching.

[0077] Using inductively coupled plasma etching technology, deep trench etching is performed on the left and right sides of the substrate 1 until the surface of the barrier layer 4 is etched, forming two source trenches 9. The process conditions are: cavity pressure 0.7 Pa, ICP source power 850 W, bias power 120 W, chlorine flow rate 18 sccm, boron trichloride flow rate 12 sccm, and argon flow rate 12 sccm.

[0078] Step 4: Grow a low-concentration n-type polarized gradient AlGaN layer.

[0079] A low-concentration n-type polarized gradient AlGaN layer 11 with a thickness of 2.65 μm was epitaxially grown on the barrier layer surface after etching in step three using MOCVD. The Al composition increased from 12% to 25% from bottom to top. The process conditions were: temperature 1010℃, reaction chamber pressure 120 Torr, trimethylgallium flow rate linearly increased from 85 sccm to 90 sccm, trimethylaluminum flow rate linearly decreased from 15 sccm to 10 sccm, ammonia flow rate 12000 sccm, and hydrogen flow rate 7000 sccm.

[0080] Step 5: Grow a high-concentration n-type polarized gradient AlGaN layer.

[0081] A high-concentration n-type polarization gradient AlGaN layer 10 with a thickness of 50 nm was epitaxially grown on a low-concentration n-type polarization gradient AlGaN layer 11 using MOCVD. The Al composition increased from 0% to 12% from bottom to top. The process conditions were: temperature 1010℃, reaction chamber pressure 120 Torr, trimethylgallium flow rate linearly increased from 90 sccm to 95 sccm, trimethylaluminum flow rate linearly decreased from 10 sccm to 0 sccm, ammonia flow rate 12000 sccm, and hydrogen flow rate 7000 sccm.

[0082] Step six, depositing the source electrode.

[0083] 6-1) Using an electron beam evaporation apparatus, a Ti / Al / Ni / Au metal stack was deposited as a source electrode 8 on two high-concentration n-type polarization gradient AlGaN layers 10. The process conditions were: electron beam current 285mA, deposition rate 1.6Å / s.

[0084] 6-2) After deposition, rapid thermal annealing is performed in a nitrogen atmosphere under the following conditions: temperature 880℃, time 35 seconds, to form good ohmic contact.

[0085] Step 7: Etch the p-GaN layer.

[0086] Using inductively coupled plasma etching (ICP-C) technology, the p-GaN layer is selectively removed, leaving two centrally symmetrical elongated regions on the left and right sides of the device to form two gate p-GaN layers 5. The process conditions are: reaction chamber pressure 1.0 Pa, ICP power 650 W, and bias power 90 W.

[0087] Step 8: Deposit the gate electrode.

[0088] Using an electron beam evaporation apparatus, Pt / Au metal stacks were deposited on two gate p-GaN layers 5 to form gate electrodes 7. The process conditions were: electron beam current 310 mA and deposition rate 2.1 Å / s.

[0089] Step nine: Deposit a passivation layer.

[0090] Using plasma-enhanced chemical vapor deposition (PECVD), Si3N4 passivation layers 6 were deposited on both sides of each gate electrode 7 and the gate p-GaN layer 5. The process conditions were: temperature 350℃, reaction chamber pressure 180Pa, silane flow rate 20sccm, and ammonia flow rate 800ccm, to complete the device fabrication.

[0091] Example 3: On a 1000 μm thick silicon carbide substrate 1, a 5 μm thick AlGaN buffer layer 2; a 500 nm thick GaN channel layer 3; a 30 nm thick AlGaN barrier layer 4 with an Al composition of 30%; a 100 nm thick high-concentration n-type polarization gradient AlGaN layer 10 with an Al composition increasing from 0% to 15%; a 5.4 μm thick high-concentration n-type polarization gradient AlGaN layer 10 with an Al composition increasing from 15% to 30%; and a 300 nm thick gate p-GaN layer 5 with a Mg doping concentration of 1 × 10⁻⁶. 20 cm -3 An enhanced gallium nitride vertical device with bidirectional conduction capability.

[0092] Step A: Substrate cleaning.

[0093] A silicon carbide substrate 1 with a thickness of 1000 μm was selected and ultrasonically cleaned for 10 minutes each with acetone, anhydrous ethanol and deionized water to remove organic and particulate contaminants. Then it was rinsed with a large amount of deionized water and dried with nitrogen to obtain a clean and contamination-free epitaxial growth surface.

[0094] Step B involves epitaxially growing a buffer layer, a channel layer, a barrier layer, and a p-GaN layer.

[0095] B1) Under the conditions of setting the temperature to 1060℃, the reaction chamber pressure to 300 Torr, the trimethylgallium flow rate to 100 sccm, the trimethylaluminum flow rate to 30 sccm, the ammonia flow rate to 8000 sccm, and the hydrogen flow rate to 10000 sccm, an AlGaN buffer layer 2 with a thickness of 5 μm is epitaxially grown on the cleaned silicon carbide substrate 1 using the MOCVD process.

[0096] B2) Under the conditions of setting the temperature to 1030℃, the reaction chamber pressure to 200Torr, the trimethylgallium flow rate to 120sccm, the ammonia flow rate to 10000sccm, and the hydrogen flow rate to 10000sccm, a GaN channel layer 3 with a thickness of 500nm is epitaxially grown on the AlGaN buffer layer 2 using the MOCVD process.

[0097] B3) Under the conditions of setting the temperature to 1030℃, the reaction chamber pressure to 100Torr, the trimethylgallium flow rate to 80sccm, the trimethylaluminum flow rate to 20sccm, the ammonia flow rate to 15000sccm, and the hydrogen flow rate to 8000sccm, an AlGaN barrier layer 4 with a thickness of 30nm and an Al composition of 30% is epitaxially grown on the GaN channel layer 3 using MOCVD process.

[0098] B4) Under the following conditions: temperature 980℃, reaction chamber pressure 60 Torr, trimethylgallium flow rate 180 sccm, dicyclopentadienylmagnesium flow rate 400 sccm, nitrogen flow rate 10000 sccm, and ammonia flow rate 3000 sccm, a 300 nm thick AlGaN barrier layer 4 is epitaxially grown using MOCVD process, with a Mg doping concentration of 1×10⁻⁶. 20 cm -3 The p-GaN layer.

[0099] Step C, source trench etching.

[0100] Under the conditions of 0.6 Pa cavity pressure, 900 W ICP source power, 150 W bias power, 20 sccm chlorine flow rate, 15 sccm boron trichloride flow rate, and 15 sccm argon flow rate, deep trench etching is performed on the left and right sides of substrate 1 using inductively coupled plasma etching technology until the surface of barrier layer 4 is etched, forming two source trenches 9.

[0101] Step D: Grow a low-concentration n-type polarized gradient AlGaN layer.

[0102] Under the conditions of a set temperature of 1000℃, a reaction chamber pressure of 100 Torr, a trimethylgallium flow rate linearly increasing from 80 sccm to 85 sccm, a trimethylaluminum flow rate linearly decreasing from 20 sccm to 15 sccm, an ammonia flow rate of 15000 sccm, and a hydrogen flow rate of 8000 sccm, a low-concentration n-type polarized gradient AlGaN layer with a thickness of 5.4 μm and an Al composition increasing from 15% to 30% from bottom to top was epitaxially grown on the surface of the barrier layer after step C etching using MOCVD process.

[0103] Step E: Grow a high-concentration n-type polarized gradient AlGaN layer.

[0104] Under the conditions of a set temperature of 1000℃, a reaction chamber pressure of 100 Torr, a trimethylgallium flow rate linearly increasing from 85 sccm to 90 sccm, a trimethylaluminum flow rate linearly decreasing from 15 sccm to 0 sccm, an ammonia flow rate of 15000 sccm, and a hydrogen flow rate of 8000 sccm, a high-concentration n-type polarized gradient AlGaN layer 10 with a thickness of 100 nm and an Al composition increasing from 0% to 15% from bottom to top is epitaxially grown on a low-concentration n-type polarized gradient AlGaN layer 11 using MOCVD process.

[0105] Step F, depositing the source electrode.

[0106] F1) Under the conditions of setting the electron beam current to 290mA and the deposition rate to 1.7Å / s, a Ti / Al / Ni / Au metal stack was deposited on two high-concentration n-type polarization gradient AlGaN layers 10 as the source electrode using an electron beam evaporation device;

[0107] After F2 deposition, rapid thermal annealing was performed in a nitrogen atmosphere at a temperature of 890°C for 40 seconds to form good ohmic contact.

[0108] Step G: Etch the p-GaN layer.

[0109] With the reaction chamber pressure set at 0.9 Pa, ICP power at 700 W, and bias power at 100 W, inductively coupled plasma etching technology was used to selectively remove the p-GaN layer. Two centrally symmetrical elongated regions were retained on the left and right sides of the device to form two gate p-GaN layers 5.

[0110] Step H: Deposit the gate electrode.

[0111] Under the conditions of an electron beam current of 320 mA and a deposition rate of 2.2 Å / s, an electron beam evaporation apparatus was used to deposit a Ni / Au metal stack on two gate p-GaN layers 5 to form gate electrodes 7.

[0112] Step I: Deposit a passivation layer.

[0113] Under the conditions of a temperature of 360℃, a reaction chamber pressure of 170Pa, a silane flow rate of 22sccm, and an ammonia flow rate of 850sccm, plasma-enhanced chemical vapor deposition (PECVD) was used to deposit Si3N4 passivation layers 6 on both sides of each gate electrode 7 and the gate p-GaN layer 5 to complete the device fabrication.

[0114] The above descriptions are merely a few specific examples of the present invention and do not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and details without departing from the principles and structure of the present invention. For example, for the use of a gate p-GaN layer to realize an enhancement-mode device, techniques such as grooved gate or fluorine ion implantation can also be used; for n-type graded AlGaN materials, n-type doped GaN materials can also be used to achieve a doping concentration gradient from heavily n-type to lightly n-type doped from bottom to top; in addition to Ti / Al / Ni / Au, the source electrode can also be Ti / Al / Mo / Au, Ti / Al / Ti / Au, or Ti / Al / Ti / TiN; in addition to Pt / Au and Ni / Au, the gate electrode can also be Mo / Au or W / Au. However, these modifications and changes based on this idea are still within the scope of the claims and protection of the present invention.

Claims

1. An enhancement-mode gallium nitride vertical device with bidirectional conduction function, comprising: The substrate (1), buffer layer (2), channel layer (3), barrier layer (4), gate p-GaN layer (5), passivation layer (6), gate electrode (7), source electrode (8), and source trench (9) are characterized in that: The source electrode (8) is located on the left and right sides of the substrate (1), so that the current flows along vertical, lateral and vertical paths when it is turned on, and forms a double vertical heat dissipation path from the active area to the substrate. The source trench (9) is located on the upper surface of the source electrode (8), and its top is connected to the lower surface of the barrier layer (4). It is provided with a high-concentration n-type polarized gradient AlGaN layer (10) and a low-concentration n-type polarized gradient AlGaN layer (11) inside, which together form a vertical current channel. The high-concentration n-type polarized gradient AlGaN layer (10) is used to form a low-resistance ohmic contact, and the low-concentration n-type polarized gradient AlGaN layer (11) is used to withstand reverse voltage and optimize the longitudinal electric field distribution.

2. The device according to claim 1, characterized in that, The high-concentration n-type polarized gradient AlGaN layer (10) is located in the lower half of the source trench (9), with its lower surface in contact with the upper surface of the source electrode (8). The Al composition increases rapidly from 0% to 10%~15%. This steep composition gradient induces a high concentration of two-dimensional electron gas through the polarization effect, achieving low-resistance ohmic contact with the source electrode (8) and providing a low-resistance inlet for the vertical current channel.

3. The device according to claim 1, characterized in that, The low-concentration n-type polarized gradient AlGaN layer (11) is located on the upper surface of the high-concentration n-type polarized gradient AlGaN layers (10) on both sides. Its Al composition increases slowly from 10% to 15% to 20% to 30%, and the Al composition at its top matches the Al composition in the barrier layer (4). This gentle composition gradient induces the generation of a low-concentration two-dimensional electron gas through the polarization effect, thereby improving the longitudinal withstand voltage of the device.

4. The device according to claim 1, characterized in that: The substrate (1) is any one of silicon, silicon carbide or sapphire substrate, and its thickness is 200μm~1000μm; The buffer layer (2) is located on the substrate (1) and is made of AlGaN or GaN material with a thickness of 1μm~5μm. It is used to alleviate the lattice mismatch and thermal mismatch between the substrate and the nitride epitaxial layer. The channel layer (3) is located above the buffer layer (2) and is made of GaN material with a thickness of 50nm~500nm. The barrier layer (4) is located above the channel layer (3). It is made of AlGaN material with a thickness of 10nm~30nm and an aluminum composition of 20%~30%.

5. The device according to claim 1, characterized in that: The gate p-GaN layer (5) is located on both sides above the barrier layer (4), with a thickness of 50nm~300nm and a Mg doping concentration of 1×10⁻⁶. 19 cm -3 ~1×10 20 cm -3 ; The gate electrode (7) is located on the upper surface region of the two gate p-GaN layers (5), and it adopts a Ni / Au or Pt / Au metal stack; The source electrode (8) adopts a Ti / Al / Ni / Au metal stack.

6. The device according to claim 1, characterized in that: The high-concentration n-type polarized gradient AlGaN layer (10) has a thickness of 10 nm to 100 nm. The low-concentration n-type polarized gradient AlGaN layer (11) has a thickness of 1 μm to 5 μm. The sum of the thicknesses of this layer and the high-concentration n-type polarized gradient AlGaN layer is equal to the sum of the thicknesses of the buffer layer (2) and the channel layer (3), to ensure the high flatness of the epitaxial layer. The passivation layer (6) is located on the left and right sides of the two gate p-GaN layers (5) and the gate electrode (7), and it is made of SiO2 or Si3N4 material.

7. A method for fabricating an enhanced gallium nitride vertical device with bidirectional conduction function, characterized in that, include: S1) Clean the selected substrate (1) to obtain a clean epitaxial growth surface; S2) On the cleaned substrate, a buffer layer (2), a channel layer (3), a barrier layer (4) and a p-GaN layer are epitaxially grown sequentially by metal-organic chemical vapor deposition (MOCVD). S3) Using inductively coupled plasma etching (ICP) technology, deep trench etching is performed on the left and right sides of the substrate until the surface of the barrier layer (4) is etched to form two source trenches (9). S4) A low-concentration n-type polarized gradient AlGaN layer (11) is epitaxially grown on the surface of the barrier layer (4) after etching in S3) by metal-organic chemical vapor deposition (MOCVD). S5) A high-concentration n-type polarization gradient AlGaN layer (10) was epitaxially grown on the surface of a low-concentration n-type polarization gradient AlGaN layer (11) by metal-organic chemical vapor deposition (MOCVD). S6) A Ti / Al / Ni / Au metal stack is deposited on the surface of a high-concentration n-type polarized gradient AlGaN layer (10) using an electron beam evaporation deposition device, and then the source electrode (8) is formed by rapid thermal annealing in a nitrogen atmosphere. S7) Using inductively coupled plasma etching (ICP) technology, the p-GaN layer is selectively removed, and two centrally symmetrical strip regions are retained on the left and right sides of the device to form two gate p-GaN layers (5). S8) Ni / Au or Pt / Au metal stack is deposited on the upper surface of the gate p-GaN layer (5) using an electron beam evaporation deposition device to form two gate electrodes (7). S9) Using plasma-enhanced chemical vapor deposition (PECVD) process, passivation layers (6) are deposited on the left and right sides of each gate electrode (7) and the gate p-GaN layer (5) to complete the device fabrication.

8. The method according to claim 7, characterized in that: The metal-organic chemical vapor deposition (MOCVD) process used in S2), S4), and S5) has the following process conditions: The temperature is 1000℃~1100℃. The reaction chamber pressure is 40 Torr~400 Torr. The flow rates of trimethylgallium, trimethylaluminum, and dicyclopentadienylmagnesium are all 0 sccm to 400 sccm. The flow rates of ammonia, hydrogen, and nitrogen are all between 3000 sccm and 20000 sccm.

9. The method according to claim 7, characterized in that, The inductively coupled plasma etching (ICP) process used in S3) and S7) has the following process conditions: The pressure in the reaction chamber is 0.3 Pa to 1.3 Pa. The ICP source power is 500W~1500W. Bias power is 20W~300W. The flow rates of chlorine, boron trichloride, and argon were all 5 sccm to 30 sccm.

10. The method according to claim 7, characterized in that: The electron beam evaporation deposition equipment used in S6) and S8) has the following process conditions: evaporation beam current: 100mA~500mA, deposition rate: 0.5~5Å / s; The plasma-enhanced chemical vapor deposition (PECVD) process used in S9) has the following process conditions: Temperature range: 250℃~400℃ The reaction chamber pressure is 50 Pa to 500 Pa. The flow rates of silane, nitrous oxide, and ammonia were all between 10 sccm and 1000 sccm.

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