A gallium oxide Schottky diode with a high breakdown bipolar field-limited ring structure and its fabrication method

Abstract

This invention discloses a gallium oxide Schottky diode with a high breakdown bipolar field-limiting ring structure and its fabrication method, mainly addressing the problem of low breakdown voltage in existing similar devices. From bottom to top, it comprises: a cathode (1), a substrate (2), an epitaxial layer (3), and an anode (6). Both the substrate (2) and the epitaxial layer (3) are made of n-type doped gallium oxide. A p-type field-limiting ring (4) and an n-type field-limiting ring (5) are sequentially arranged outside the anode on the upper surface of the gallium oxide epitaxial layer (3), with the n-type field-limiting ring (5) located above the p-type field-limiting ring (4). The two rings are made of different semiconductor materials to form a heterogeneous bipolar field-limiting ring structure with the gallium oxide epitaxial layer. This invention significantly improves the breakdown voltage performance of the device compared to existing diodes and can be used in high-voltage, high-power power electronic systems.

Description

Technical Field

[0001] This invention belongs to the field of wide bandgap semiconductors, specifically relating to a high-breakdown bipolar field-ring structure gallium oxide Schottky diode, which can be used in high-voltage, high-power power electronic systems. Background Technology

[0002] Ga2O3 material has a wide bandgap of ~4.9 eV, therefore, semiconductor devices based on it exhibit high breakdown electric fields, offering significant advantages in high-voltage power electronic devices. Ga2O3 power semiconductor devices, as highly promising semiconductor components, play a role in rectification, amplification, and switching in circuits. In the future, they can be applied to power supplies, drive loads, and pulse power regulation systems for electronic devices, showing significant potential application value in new energy, rail transportation, and aerospace fields. The fields of space electric propulsion and power management have created enormous demands for high-performance power electronic devices, and gallium oxide devices are an important choice to meet these demands.

[0003] Diodes are a major research area in Ga2O3 electronic power devices, playing a crucial role in high-voltage, high-power applications. With continuous technological advancements, higher demands are being placed on various aspects of diode performance, especially on-resistance and reverse breakdown voltage. The reverse breakdown voltage and on-resistance of a diode directly affect its practical application. Figure 1 Traditional gallium oxide Schottky diodes without termination structures suffer from lower-than-ideal breakdown voltages due to the concentrated electric field at the edges and surfaces, where the electric field strength at the junction edges is higher than inside the junction. Currently, gallium oxide power devices typically require appropriate termination structures to reduce the electric field at the semiconductor edges and surfaces, thereby improving the device's breakdown voltage. Common termination techniques include metal field plates, field limiting rings, combinations of field plates and field limiting rings, floating metal rings, trenches, and bevel structures.

[0004] Hiroshi Kono et al. presented "Improving the specific on-resistance and short-circuit ruggedness tradeoff of 1.2-kV-class SBD-embedded SiC MOSFETs through cell pitch reduction and internal resistance optimization" at the 33rd International Symposium on Power Semiconductor Devices and ICs in 2021. Figure 2 As shown, the bottom layer of this silicon carbide Schottky diode is the cathode, above which is the silicon carbide substrate, above which is an n-type silicon carbide drift layer, above which is a silicon carbide current spreading layer, and above the silicon carbide current spreading layer is the anode. At the edge within the silicon carbide current spreading layer, there are p-type electrodes formed by ion implantation. — Field-limited loop and n + Field-limited loop, where n + Field limit loop in p — Above the field limit ring. + Field limit loop, p — The field-limiting ring and the silicon carbide current-spreading layer form a homogeneous bipolar field-limiting ring structure. While this structure can reduce the edge peak electric field and improve the device's breakdown voltage, the p-type structure is fabricated using ion implantation. — Field-limited loop and n + When a field limiting ring is used, it can damage the device and affect its performance. Furthermore, the breakdown voltage of a device with a homogeneous bipolar field limiting ring structure is lower than that of a device with a heterogeneous bipolar field limiting ring structure. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the existing technology by providing a high-breakdown bipolar field-ring structure gallium oxide Schottky diode and its fabrication method to meet the operating requirements of future power electronic devices.

[0006] The following technical solution achieves the objective of this invention:

[0007] 1. A high-breakdown bipolar field-ring structure gallium oxide Schottky diode, comprising, from bottom to top: a cathode, a substrate, an epitaxial layer, and an anode, characterized in that:

[0008] Both the substrate and the epitaxial layer are made of n-type doped gallium oxide material to improve the breakdown field strength;

[0009] The p-type field limiting ring (4) and the n-type field limiting ring (5) are located at the anode edge of the upper part of the gallium oxide epitaxial layer (3), and the n-type field limiting ring (4) is located above the p-type field limiting ring. The p-type field limiting ring (4) and the n-type field limiting ring (5) are made of different semiconductor materials to form a heterogeneous bipolar structure field limiting ring with the gallium oxide epitaxial layer, thereby further improving the breakdown voltage of the device.

[0010] Furthermore, the material of the p-type field limiting ring is selected from any one of nickel oxide, tin oxide, cuprous oxide, silicon carbide, and gallium oxide.

[0011] Furthermore, the material of the n-type field limiting ring is selected from any one of tin oxide, gallium oxide, cuprous oxide, silicon carbide, and gallium oxide.

[0012] Furthermore, the cathode is a Ti / Au bilayer metal, and the thickness of the first Ti layer near the gallium oxide substrate is 10-30 nm, and the thickness of the second Au metal layer is 150-400 nm.

[0013] Furthermore, the thickness of the gallium oxide substrate is 400–650 μm, and the effective doping carrier concentration is 10. 18 ~10 19 cm-3, the doped ion is Si ion.

[0014] Furthermore, the thickness of the gallium oxide epitaxial layer is 5–15 μm, and the doping carrier concentration is 10. 15 ~10 17 cm-3, the doped ion is Si ion.

[0015] Furthermore, the anode is a Ni / Au bilayer metal, with the first Ni layer having a thickness of 45-55 nm and the second Au layer having a thickness of 300-400 nm.

[0016] 2. A method for fabricating a high-breakdown bipolar field-ring structure gallium oxide Schottky diode, characterized by comprising the following steps:

[0017] 1) Gallium oxide substrate was selected and it was cleaned sequentially with acetone-isopropanol-deionized water;

[0018] 2) A gallium oxide epitaxial layer is grown on the front side of a cleaned gallium oxide substrate using hydride vapor phase epitaxy.

[0019] 3) An ohmic Ti / Au metal cathode was deposited on the back side of a gallium oxide substrate by magnetron sputtering under an argon atmosphere, and then subjected to ohmic annealing.

[0020] 4) Spin-coat photoresist onto the annealed gallium oxide epitaxial layer, and use photolithography to etch a p-type field confinement ring pattern. Then place it in the magnetron sputtering reaction chamber, turn on the target material, set the chamber pressure to 6-10 mTorr, the ambient temperature to 25℃, and the power to 100-200W, introduce the appropriate gas, and perform magnetron sputtering on the gallium oxide epitaxial layer for 200-300 minutes to deposit a p-type semiconductor material with a thickness of 90-110 nm.

[0021] 5) Place the deposited sample in an acetone solution and ultrasonically clean it under an ultrasonic intensity of 2.0; then boil the ultrasonically cleaned sample at 60°C for 10-15 minutes using a stripping solution; then ultrasonically clean the sample after boiling with the stripping solution using acetone-isopropanol-deionized water and dry it with nitrogen gas to remove the p-type semiconductor material outside the photolithographic pattern area to form a p-type field confinement ring.

[0022] 6) Spin-coat photoresist onto the gallium oxide epitaxial layer and the p-type field confinement ring, and use photolithography to etch the pattern of the n-type field confinement ring, placing it above the p-type field confinement ring. Place the sample in the magnetron sputtering reaction chamber, turn on the target material of the corresponding material, set the chamber pressure to 6-10 mTorr, the ambient temperature to 25℃, and the power to 100-200W, introduce the corresponding gas, and perform magnetron sputtering on the gallium oxide epitaxial layer and the p-type field confinement ring for 200-300 minutes to deposit an n-type semiconductor material with a thickness of 90-110 nm.

[0023] 7) Place the sample with deposited n-type semiconductor material in acetone solution and ultrasonically clean it under an ultrasonic intensity of 2.0; then use a stripping solution to boil the sample at 60°C for 10-15 minutes; then use acetone-isopropanol-deionized water to ultrasonically clean the sample after boiling and dry it with nitrogen gas to remove the n-type semiconductor material outside the photolithographic pattern area to form an n-type field limiting ring above the p-type field limiting ring.

[0024] 8) An anode pattern is formed on the front side of the gallium oxide epitaxial layer and the n-type field confinement ring using photolithography. Ni / Au metal is deposited by electron beam evaporation according to the anode pattern and then stripped to form the anode, thus completing the device fabrication.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] First, both the substrate and the epitaxial layer of the present invention are made of n-type doped gallium oxide material with a band gap of 4.9 eV, which is higher than the band gap of silicon carbide used in existing devices, which is only 3.4 eV, thus improving the breakdown voltage of the device.

[0027] Secondly, this invention uses a deposition method to fabricate n-type and p-type field limiting rings on the surface of the gallium oxide epitaxial layer, compared to the prior art which uses ion implantation to fabricate n-type and p-type field limiting rings inside the epitaxial layer. This avoids damage to the epitaxial layer caused by ion implantation and improves the breakdown voltage of the device.

[0028] Third, the present invention uses different materials to fabricate n-type and p-type field limiting rings to form a heterogeneous bipolar field limiting ring structure, which further improves the breakdown voltage of the device compared with the prior art which uses the same material to fabricate a homogeneous bipolar field limiting ring structure. Attached Figure Description

[0029] Figure 1 A schematic diagram of a traditional Schottky diode without a termination structure;

[0030] Figure 2 This is a schematic diagram of a silicon carbide Schottky diode with an internal bipolar field ring structure.

[0031] Figure 3 This is a schematic diagram of the gallium oxide Schottky diode with a high breakdown bipolar field ring structure according to the present invention;

[0032] Figure 4 For the purpose of this invention Figure 3 Flowchart of gallium oxide Schottky diode;

[0033] Figure 5 This is a comparison diagram of the forward conduction current of the diode of the present invention and that of a conventional diode;

[0034] Figure 6 This is a comparison diagram of the reverse breakdown voltage of the diode of the present invention and a conventional diode. Detailed Implementation

[0035] To more clearly illustrate the technical solution of the present invention, the embodiments and effects of the present invention will be further described in detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments, and those skilled in the art should understand that the present invention can also be implemented in other embodiments without these specific details.

[0036] Reference Figure 3 The present invention relates to a high-breakdown bipolar field-ring structure gallium oxide Schottky diode, comprising: a cathode 1, a gallium oxide substrate 2, an n-type gallium oxide epitaxial layer 3, a p-type field-limiting ring 4, an n-type field-limiting ring 5, and an anode 6, wherein:

[0037] The gallium oxide substrate 2 has a thickness of 400–650 μm and a doping concentration of 10. 18 ~10 19 cm -3 The doping ion is Si ion.

[0038] The cathode 1 is located below the gallium oxide substrate 2 and adopts a Ti / Au double-layer metal. The thickness of the first Ti layer close to the gallium oxide substrate 2 is 10-30 nm, and the thickness of the second Au metal layer is 150-400 nm.

[0039] The n-type gallium oxide epitaxial layer 3 is located above the gallium oxide substrate 2, and has a thickness of 5–15 μm and a doping concentration of 10. 15 ~10 17 cm -3 The doping ion is Si ion.

[0040] The p-type field confinement ring 4 and the n-type field confinement ring 5 are located on the upper surface of the n-type gallium oxide epitaxial layer 3 and form a bipolar field confinement ring structure.

[0041] The material of the p-field limiting ring 4 can be any one of nickel oxide, tin oxide, cuprous oxide, silicon carbide, and gallium oxide.

[0042] The n-type field limiting ring 5 is located above the p-type field limiting ring 4, and its material can be any one of tin oxide, cuprous oxide, silicon carbide and gallium oxide;

[0043] The anode 6 is located above the n-type field confinement ring 5 and the n-type gallium oxide epitaxial layer 3. It adopts a Ni / Au bilayer metal, and the thickness of the first metal Ni is 45-55nm, and the thickness of the second metal Au is 300-400nm.

[0044] Reference Figure 4 This invention provides a method for manufacturing... Figure 3 The following are three examples of device structures:

[0045] Example 1: A gallium oxide Schottky diode with a bipolar field-limiting ring structure is fabricated using cuprous oxide as the n-type field-limiting ring layer with a thickness of 100 nm and nickel oxide as the p-type field-limiting ring.

[0046] Step 1: Clean the gallium oxide substrate 2.

[0047] The effective doping carrier concentration was selected as 10. 18 cm -3 A gallium oxide substrate 2 with Si ions and a thickness of 400 μm was placed in acetone-isopropanol-deionized water and ultrasonically cleaned for 3 minutes under ultrasonic intensity 2.0, and then dried with nitrogen gas.

[0048] Step 2: An n-type gallium oxide epitaxial layer 3 is fabricated on the front side of the cleaned gallium oxide substrate 2 using hydride vapor phase epitaxy.

[0049] 2.1) In the high-temperature reaction zone of the hydride gas-phase epitaxial vertical reactor, HCl is reacted with high-purity metal Ga at 800℃ to generate GaCl and GaCl3.

[0050] 2.2) The GaCl and GaCl3 generated in the high-temperature reaction zone are pushed into the low-temperature reaction zone. Then, the gallium oxide substrate is placed face up in the low-temperature reaction zone of the hydride vapor phase epitaxial vertical reactor, allowing GaCl and GaCl3 to react with oxygen at 500°C, forming a 5μm thick substrate with a doping concentration of 10 on the gallium oxide substrate 2. 16 cm -3 3. n-type gallium oxide epitaxial layer.

[0051] Step 3: Prepare cathode ohmic metal 1.

[0052] Using magnetron sputtering technology, under the conditions of 300W power, 90 minutes sputtering time, 12mtorr pressure and ambient temperature of 30℃, Ti / Au bilayer metal was sequentially deposited on the back side of gallium oxide substrate 2. The thickness of the first Ti layer close to the gallium oxide substrate layer is 30nm, and the thickness of the second Au metal layer is 400nm, forming cathode 1.

[0053] The cathode metal was annealed in an annealing furnace under a nitrogen atmosphere at a temperature of 500°C for 2 minutes.

[0054] Step 4: Deposit p-type field confinement ring 4.

[0055] 4.1) Photoresist was spin-coated onto the annealed gallium oxide epitaxial layer 3, and a p-type field confinement ring pattern was etched using photolithography. The pattern was then placed in a magnetron sputtering reaction chamber, the nickel target was turned on, and the chamber pressure was set to 10 mTorr, the ambient temperature to 25°C, the flow rate of O2 gas to 20 sccm, the flow rate of Ar gas to 9 sccm, and the power to 200 W. Magnetron sputtering was performed on the gallium oxide epitaxial layer 3 for 250 minutes to deposit a p-type semiconductor material with a thickness of 100 nm.

[0056] 4.2) Place the deposited sample in acetone solution and ultrasonically clean it under an ultrasonic intensity of 2.0; then boil the ultrasonically cleaned sample at 60°C for 15 minutes using a stripping solution; then ultrasonically clean the sample after boiling with the stripping solution using acetone-isopropanol-deionized water in sequence and dry it with nitrogen gas to remove the p-type semiconductor material outside the photolithographic pattern area to form a p-type field confinement ring 4.

[0057] Step 5: Deposit n-type field confinement ring 5.

[0058] 5.1) Photoresist was spin-coated onto gallium oxide epitaxial layer 3 and p-type field confinement ring 4. The pattern of n-type field confinement ring was etched using photolithography and positioned above p-type field confinement ring 4. The sample was placed in a magnetron sputtering reaction chamber, and a copper target was sputtered. The chamber pressure was set to 10 mTorr, the ambient temperature to 25℃, the flow rate of O2 gas to 20 sccm, the flow rate of Ar gas to 3 sccm, and the power to 200W. Magnetron sputtering was performed on gallium oxide epitaxial layer 3 and p-type field confinement ring 4 for 250 minutes to deposit an n-type semiconductor material with a thickness of 100 nm.

[0059] 5.2) The sample with deposited n-type semiconductor material was placed in acetone solution and ultrasonically cleaned under an ultrasonic intensity of 2.0; the ultrasonically cleaned sample was then boiled in stripping solution at 60°C for 15 minutes; the sample after boiling in stripping solution was then ultrasonically cleaned in sequence with acetone-isopropanol-deionized water and dried with nitrogen gas to remove the n-type semiconductor material outside the photolithographic pattern area to form an n-type field limiting ring 5 located above the p-type field limiting ring 4;

[0060] Step 6: Prepare anode 6.

[0061] 6.1) An anode pattern is formed on the front side of the gallium oxide epitaxial layer 3 and the n-type field confinement ring 5 using bulk photolithography;

[0062] 6.2) Electron beam evaporation is used to deposit metallic Ni / Au onto the anode pattern, with the first layer of metallic Ni having a thickness of 45 nm and the second layer of metallic Au having a thickness of 300 nm.

[0063] 6.3) Use N-methylpyrrolidone solution to wash away the photoresist, that is, remove the metal material deposited in the areas without photolithographic patterns, and complete the device fabrication.

[0064] Example 2: A bipolar field-limiting ring structure gallium oxide Schottky diode was fabricated using tin oxide as the p-type field-limiting ring layer with a thickness of 100 nm and gallium nitride as the n-type field-limiting ring.

[0065] Step 1: Clean the gallium oxide substrate 2.

[0066] The effective doping carrier concentration was selected as 10. 19 cm -3 A gallium oxide substrate 2 with Si ions and a thickness of 650 μm was placed in acetone-isopropanol-deionized water and ultrasonically cleaned for 3 minutes under ultrasonic intensity 2.0, and then dried with nitrogen gas.

[0067] Step 2: An n-type gallium oxide epitaxial layer 3 is fabricated on the front side of the cleaned gallium oxide substrate 2 using hydride vapor phase epitaxy.

[0068] First, in the high-temperature reaction zone of the hydride gas-phase epitaxial vertical reactor, HCl and high-purity metal Ga are reacted at 900℃ to generate GaCl and GaCl3, and then the GaCl and GaCl3 are pushed into the low-temperature reaction zone.

[0069] The gallium oxide substrate is then placed face up in the low-temperature reaction zone of a vertical hydride vapor phase epitaxy reactor, where GaCl and GaCl3 react with oxygen at 650°C, forming a 15 μm thick substrate with a doping concentration of 10 on the gallium oxide substrate 2. 17 cm -33. n-type gallium oxide epitaxial layer.

[0070] Step 3: Prepare cathode ohmic metal 1.

[0071] Using magnetron sputtering technology, under the conditions of 100W power, sputtering time of 30 minutes, pressure of 6mtorr and ambient temperature of 25℃, a 10nm thick Ti and a 250nm thick Au were sequentially deposited on the back side of a gallium oxide substrate 2 to form a cathode 1 composed of a Ti / Au bilayer metal.

[0072] Anneal for 3 minutes in a nitrogen atmosphere at 500℃.

[0073] Step 4: Deposit p-type field confinement ring 4.

[0074] First, photoresist is spin-coated onto the annealed gallium oxide epitaxial layer 3. The p-type field confinement ring pattern is then etched using photolithography and placed in the magnetron sputtering reaction chamber. The tin target is opened, and under the process conditions of 10 mTorr pressure, 25°C temperature, 8 sccm flow rate of O2 gas, 16 sccm flow rate of Ar gas, and 200W power, magnetron sputtering is performed on the gallium oxide epitaxial layer 3 for 300 minutes to deposit a p-type semiconductor material with a thickness of 110 nm.

[0075] The deposited sample was then placed in an acetone solution and ultrasonically cleaned at an ultrasonic intensity of 2.0.

[0076] The ultrasonically cleaned sample is then boiled in a stripping solution at 60°C for 10–15 minutes.

[0077] The sample after boiling the stripping solution was then ultrasonically cleaned with acetone-isopropanol-deionized water and dried with nitrogen to remove the p-type semiconductor material outside the photolithographic pattern area to form a p-type field confinement ring 4.

[0078] Step 5: Deposit n-type field confinement ring 5.

[0079] First, photoresist is spin-coated onto gallium oxide epitaxial layer 3 and p-type field confinement ring 4. The pattern of n-type field confinement ring is then etched using photolithography and positioned above p-type field confinement ring 4. The sample is placed in a magnetron sputtering reaction chamber, and the gallium target is turned on. Under the process conditions of a chamber pressure of 6 mTorr, an ambient temperature of 25°C, a flow rate of N2 gas of 15 sccm, a flow rate of Ar gas of 15 sccm, and a power of 200W, magnetron sputtering is performed on gallium oxide epitaxial layer 3 and p-type field confinement ring 4 for 300 minutes to deposit an n-type semiconductor material with a thickness of 110 nm.

[0080] The sample with deposited n-type semiconductor material was then placed in an acetone solution and ultrasonically cleaned under an ultrasonic intensity of 2.0.

[0081] The ultrasonically cleaned sample is then boiled in a stripping solution at 60°C for 10–15 minutes.

[0082] The sample after boiling the stripping solution is then ultrasonically cleaned with acetone-isopropanol-deionized water and dried with nitrogen to remove the n-type semiconductor material outside the photolithographic pattern area to form an n-type field confinement ring 5 above the p-type field confinement ring 4.

[0083] Step 6: Prepare anode 6.

[0084] An anode pattern is formed on the front side of the gallium oxide epitaxial layer 3 and the n-type field confinement ring 5 using photolithography. Then, metal Ni / Au is deposited on the anode pattern using electron beam evaporation. The thickness of the first metal Ni layer is 55 nm, and the thickness of the second metal Au layer is 400 nm. The photoresist is then washed away using N-methylpyrrolidone solution, that is, the metal material deposited in the area without photolithography pattern is removed, thus completing the device fabrication.

[0085] Example 3: A bipolar field-limiting ring structure gallium oxide Schottky diode is fabricated using gallium nitride material for the n-type field-limiting ring layer with a thickness of 100 nm and nickel oxide material for the p-type field-limiting ring with a thickness of 100 nm.

[0086] Step A: Clean the gallium oxide substrate 2.

[0087] A1) Select an effective doping carrier concentration of 2×10⁻⁶. 18 cm -3 2. Gallium oxide substrate with Si ions as dopants and a thickness of 500 μm;

[0088] A2) The gallium oxide substrate 2 was placed in acetone-isopropanol-deionized water and ultrasonically cleaned for 3 minutes under ultrasonic intensity 2.0, and then dried with nitrogen gas.

[0089] Step B: An n-type gallium oxide epitaxial layer 3 is fabricated on the front side of the cleaned gallium oxide substrate 2 using hydride vapor phase epitaxy.

[0090] B1) In the high-temperature reaction zone of the hydride gas-phase epitaxial vertical reactor, HCl is reacted with high-purity metal Ga at 900℃ to generate GaCl and GaCl3.

[0091] B2) The GaCl and GaCl3 generated in the high-temperature reaction zone are pushed into the low-temperature reaction zone. Then, the gallium oxide substrate is placed face up in the low-temperature reaction zone of the hydride vapor phase epitaxial vertical reactor, allowing GaCl and GaCl3 to react with oxygen at 650°C, forming a 15μm thick substrate with a doping concentration of 10 on the gallium oxide substrate 2. 15 cm -3 3. n-type gallium oxide epitaxial layer.

[0092] Step C: Prepare cathode ohmic metal 1.

[0093] Using magnetron sputtering technology, under the process conditions of 200W power, 60 minutes sputtering time, 9mtorr pressure and ambient temperature of 25℃, Ti / Au bilayer metal was sequentially deposited on the back side of gallium oxide substrate 2. The thickness of the first Ti layer close to the gallium oxide substrate layer is 20nm, and the thickness of the second Au metal layer is 300nm, forming cathode 1.

[0094] Annealing conditions were set at 450℃ and 2 minutes, and the cathode metal was annealed in a nitrogen atmosphere.

[0095] Step D: Deposit p-type field confinement ring 4.

[0096] D1) Photoresist was spin-coated onto the annealed gallium oxide epitaxial layer 3, and a p-type field confinement ring pattern was etched using photolithography. The pattern was then placed in a magnetron sputtering reaction chamber, and a nickel target was turned on. Under the process conditions of a chamber pressure of 10 mTorr, an ambient temperature of 25°C, an O2 gas flow rate of 20 sccm, an Ar gas flow rate of 9 sccm, and a power of 00W, magnetron sputtering was performed on the gallium oxide epitaxial layer 3 for 200 minutes to deposit a p-type semiconductor material with a thickness of 90 mm.

[0097] D2) The deposited sample was placed in an acetone solution and ultrasonically cleaned at an ultrasonic intensity of 2.0. The ultrasonically cleaned sample was then boiled in a stripping solution at 60°C for 15 minutes. The sample after boiling in the stripping solution was then ultrasonically cleaned in sequence with acetone-isopropanol-deionized water and dried with nitrogen gas to remove the p-type semiconductor material outside the photolithographic pattern area to form a p-type field confinement ring 4.

[0098] Step E: Deposit n-type field confinement ring 5.

[0099] E1) Photoresist was spin-coated onto gallium oxide epitaxial layer 3 and p-type field confinement ring 4. The pattern of n-type field confinement ring was etched using photolithography and positioned above p-type field confinement ring 4. The sample was then placed in a magnetron sputtering reaction chamber. The target material of gallium material was turned on. Under the process conditions of chamber pressure of 10 mTorr, ambient temperature of 25℃, N2 gas flow rate of 15 sccm, Ar gas flow rate of 15 sccm, and power of 200W, magnetron sputtering was performed on gallium oxide epitaxial layer 3 and p-type field confinement ring 4 for 250 minutes to deposit an n-type semiconductor material with a thickness of 90 nm.

[0100] E2) Place the sample with deposited n-type semiconductor material in acetone solution and ultrasonically clean it under an ultrasonic intensity of 2.0. Then, use a stripping solution to boil the sample at 60°C for 10-15 minutes. After boiling the sample with the stripping solution, use acetone-isopropanol-deionized water for ultrasonic cleaning in sequence and blow it dry with nitrogen to remove the n-type semiconductor material outside the photolithographic pattern area to form an n-type field confinement ring 5 above the p-type field confinement ring 4.

[0101] Step F: Prepare anode 6.

[0102] F1) An anode pattern is formed on the front side of the gallium oxide epitaxial layer 3 and the n-type field confinement ring 5 using a photolithography process;

[0103] F2) Two metal Ni / Au layers with a thickness of 45 nm and a thickness of 400 nm are sequentially deposited on the anode pattern using electron beam evaporation; then, the metal material deposited in the areas without photolithography patterns is removed using N-methylpyrrolidone solution to complete the device fabrication.

[0104] The effectiveness of this invention can be further illustrated by test results:

[0105] Test 1: The reverse voltage was gradually increased from 0V to 1700V. This reverse voltage was applied across the diode of this invention and the gallium oxide Schottky diode without a termination structure. The reverse breakdown voltage was determined by measuring the magnitude of the reverse current. The results are as follows: Figure 5 As shown. From Figure 5 It is evident that the breakdown voltage of a traditional gallium oxide Schottky diode without a termination structure is only 900V, while the breakdown voltage of the diode of this invention is 1655V, which is significantly better than that of a traditional gallium oxide Schottky diode without a termination structure.

[0106] Test 2: Set a forward voltage from -2V to 4V, apply the forward voltage to the diode of this invention and a conventional gallium oxide Schottky diode without a termination structure, and test the magnitude of their forward current. The results are as follows. Figure 6 As shown. From Figure 6As can be seen, under a 4V voltage condition, the diode of this invention has a current of 470A / cm. 2 Slightly lower than the 580 A / cm of traditional gallium oxide Schottky diodes without termination structures. 2 The current is higher, but its breakdown voltage is increased by 83% compared to traditional gallium oxide Schottky diodes without termination structures.

[0107] The above descriptions are merely three 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, can make various modifications and changes in form and details without departing from the principles and structure of the present invention. For example, in addition to nickel oxide and tin oxide materials in the above embodiments, the p-type semiconductor material used in the field limiting ring can also be copper oxide, cuprous oxide, or gallium oxide; in addition to cuprous oxide and gallium nitride materials in the above embodiments, the n-type semiconductor material can also be copper oxide or gallium oxide; semiconductor deposition is not limited to magnetron sputtering deposition, but can also use laser pulse deposition; the anode and cathode metal preparation methods are not limited to electron beam evaporation, but can also use either magnetron sputtering or thermal evaporation. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A high-breakdown bipolar field-ring structure gallium oxide Schottky diode, comprising, from bottom to top: The cathode (1), substrate (2), epitaxial layer (3), and anode (6) are characterized in that: The substrate (2) and the epitaxial layer (3) are both made of n-type doped gallium oxide material to improve the breakdown field strength; A p-type field limiting ring (4) and an n-type field limiting ring (5) are deposited at the anode edge on the upper surface of the gallium oxide epitaxial layer (3), and the n-type field limiting ring (4) is located above the p-type field limiting ring. The p-type field limiting ring (4) and the n-type field limiting ring (5) are made of different semiconductor materials to form a heterogeneous bipolar structure field limiting ring with the gallium oxide epitaxial layer, thereby further improving the breakdown voltage of the device.

2. The diode according to claim 1, characterized in that: The material of the p-type field confinement ring (4) is any one of nickel oxide, tin oxide, cuprous oxide, silicon carbide and gallium oxide, and its thickness is 90~110nm.

3. The diode according to claim 1, characterized in that: The material of the n-type field confinement ring (5) is selected from any one of tin oxide, gallium oxide, cuprous oxide, silicon carbide and gallium oxide, and its thickness is 90~110nm.

4. The diode according to claim 1, characterized in that: The cathode (1) adopts a Ti / Au double-layer metal, and the thickness of the first Ti layer close to the gallium oxide substrate is 10~30nm, and the thickness of the second Au metal layer is 150~400nm.

5. The diode according to claim 1, characterized in that: The substrate (2) has a thickness of 400~650μm and an effective doping carrier concentration of 10. 18 ~10 19 cm-3, the doped ion is Si ion.

6. The diode according to claim 1, characterized in that: The gallium oxide epitaxial layer (3) has a thickness of 5~15 μm and a doping carrier concentration of 10. 15 ~10 17 cm-3, the doped ion is Si ion.

7. The diode according to claim 1, characterized in that: The anode (6) is made of Ni / Au bilayer metal, and the thickness of the first layer Ni is 45~55nm, and the thickness of the second layer Au is 300~400nm.

8. A method for fabricating a high-breakdown bipolar field-ring structure gallium oxide Schottky diode, characterized in that, Includes the following steps: 1) Select a gallium oxide substrate (2) and clean it sequentially with acetone-isopropanol-deionized water; 2) A gallium oxide epitaxial layer (3) is grown on the front side of the cleaned gallium oxide substrate (2) using hydride vapor phase epitaxy technology; 3) An ohmic Ti / Au metal cathode (1) was deposited on the back side of a gallium oxide substrate (2) by magnetron sputtering under an argon atmosphere, and then subjected to ohmic annealing. 4) Spin-coat photoresist onto the annealed gallium oxide epitaxial layer (3), use photolithography to lithographically pattern a p-type field confinement ring, place it in the magnetron sputtering reaction chamber, open the target material of the corresponding material, set the chamber pressure to 6~10mTorr, the environment to 25℃, and the power to 100~200W, introduce the corresponding gas, and perform magnetron sputtering on the gallium oxide epitaxial layer (3) for 200~300 minutes to deposit a p-type semiconductor material with a thickness of 90~110nm; 5) Place the deposited sample in acetone solution and ultrasonically clean it under an ultrasonic intensity of 2.0; then use stripping solution to boil the ultrasonically cleaned sample at 60°C for 10-15 minutes; then use acetone-isopropanol-deionized water to ultrasonically clean the sample after boiling and blow it dry with nitrogen to remove the p-type semiconductor material outside the photolithographic pattern area to form a p-type field confinement ring (4). 6) Spin-coat photoresist on gallium oxide epitaxial layer (3) and p-type field confinement ring (4), and use photolithography to lithographically pattern n-type field confinement ring, so that it is located above p-type field confinement ring (4). Place the sample in the magnetron sputtering reaction chamber, turn on the target material of the corresponding material, set the chamber pressure to 6~10 mTorr, the ambient temperature to 25 ℃, and the power to 100~200 W, and introduce the corresponding gas. Perform magnetron sputtering on gallium oxide epitaxial layer (3) and p-type field confinement ring (4) for 200~300 minutes to deposit n-type semiconductor material with a thickness of 90~110nm. 7) Place the sample with deposited n-type semiconductor material in acetone solution and ultrasonically clean it under an ultrasonic intensity of 2.0; then use stripping solution to boil the sample at 60°C for 10-15 minutes; then use acetone-isopropanol-deionized water to ultrasonically clean the sample after boiling and blow it dry with nitrogen to remove the n-type semiconductor material outside the photolithographic pattern area to form an n-type field limiting ring (5) above the p-type field limiting ring (4); 8) An anode pattern is formed on the front side of the gallium oxide epitaxial layer (3) and the n-type field confinement ring (5) using photolithography. Ni / Au metal is deposited by electron beam evaporation according to the anode pattern and then stripped to form the anode (6), thus completing the device fabrication.

9. The method according to claim 8, characterized in that: In step 3), magnetron sputtering is used to deposit ohmic Ti / Au metal on the back side of the gallium oxide substrate to form a cathode (1). The process conditions are: power of 150~300 W, sputtering time of 60~90 minutes, pressure of 6~12 mtorr, and ambient temperature of 25℃.

10. The method according to claim 8, characterized in that, In step 2), a gallium oxide epitaxial layer (3) is grown on the front side of the cleaned gallium oxide substrate (2) using hydride vapor phase epitaxy technology, as follows: 2a) Ammonia gas is introduced into the high-temperature reaction zone of the hydride gas-phase epitaxial vertical reactor, and hydrogen chloride gas is reacted with high-purity metal Ga at a temperature of 800~900℃ to generate GaCl and GaCl3. 2b) The GaCl and GaCl3 generated in the high temperature reaction zone are pushed into the low temperature reaction zone, and the gallium oxide substrate (2) is placed face up in the low temperature reaction zone of the HVPE vertical reactor. The products GaCl and GaCl3 in the high temperature reaction zone are reacted with oxygen at a temperature of 500~650℃ to generate an n-type gallium oxide epitaxial layer (3) on the gallium oxide substrate (2).

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