A gallium oxide schottky diode with reduced on-resistance and a method of manufacturing the same

Abstract

The application discloses a gallium oxide Schottky diode with reduced on-resistance and a preparation method thereof, and mainly solves the problems that the prior art cannot prepare low-damage gallium oxide substrate material and cannot effectively reduce the on-resistance of a device. From bottom to top, the gallium oxide Schottky diode comprises a cathode metal (1), a gallium oxide substrate (2), a lightly doped epitaxial layer (3) and an anode metal (4), wherein the gallium oxide substrate (2) is thinned by wet etching using a corrosion solution prepared by mixing 49% concentration hydrofluoric acid and 75%-90% concentration high potassium sulfate in a proportion of 1:1; and the cathode metal (1) adopts a sawtooth-shaped ohmic contact pattern structure. The gallium oxide substrate material with an original thickness of 650 mu m is thinned to 200-400 mu m, and the sawtooth-shaped ohmic contact pattern structure is prepared by using the thinned substrate, so that the on-resistance is reduced, the device performance is improved, and the gallium oxide Schottky diode can be used in electronic systems of communication, power electronics, signal processing and aerospace.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor devices, and particularly relates to a gallium oxide Schottky diode which can be used in electronic systems of communication, power electronics, signal processing and aerospace. TECHNICAL BACKGROUND

[0002] As a new emerging ultra-wide bandgap semiconductor material, gallium oxide is gradually becoming a research hotspot due to its large bandgap and high theoretical breakdown field. With the development of material growth and the improvement of epitaxial technology, the large-scale production of gallium oxide materials is initially taking shape and has great development potential. The large bandgap enables it to have lower power loss and higher conversion efficiency in the application of power electronic devices. Among them, the gallium oxide Schottky diode has become one of the research focuses and hotspots of gallium oxide power electronic devices in recent years due to its fast switching speed and low on-state loss.

[0003] The on-resistance of gallium oxide power devices is an important parameter to measure the performance of the devices. The main method to reduce the on-resistance of the devices by reducing the substrate resistance is to thin the gallium oxide substrate. The mainstream substrate thinning technology at present is chemical mechanical polishing technology, which uses silica gel as a polishing agent applied to the surface of semiconductor crystals, and realizes the thinning of the gallium oxide substrate through the combined action of chemical reaction and mechanical grinding. However, the chemical mechanical polishing technology has many problems: 1) The technology needs to produce stress on the surface of the gallium oxide material, and since the gallium oxide material has low hardness, it cannot withstand excessive stress, resulting in small thinning thickness of the technology; 2) The surface roughness of the gallium oxide substrate will become larger after being thinned by this method, and the surface defects will increase. Therefore, how to deeply thin the gallium oxide substrate under the premise of ensuring the surface quality of the gallium oxide substrate and reduce the on-resistance of the device is still a difficult problem.

[0004] Gao G et al. published "Research on Chemical Mechanical Polishing of Gallium Oxide Substrate" in Mechanical Design and Manufacturing, which adopts chemical mechanical polishing to thin the gallium oxide substrate to reduce the substrate resistance and reduce the on-resistance of the device.

[0005] Lee, Y et al. published "Thermal Atomic Layer Etching of Gallium Oxide Using Sequential Exposures of HF and Various Metal Precursors" in CHEMISTRY OF MATERIALS, which uses hydrofluoric acid to soak gallium oxide to achieve the purpose of etching gallium oxide material.

[0006] Although the above methods can thin the gallium oxide substrate, the thinning thickness is limited, and the damage to the surface of the gallium oxide substrate after thinning is too large, which seriously affects the performance of the device. SUMMARY

[0007] The present application aims at reducing the conduction resistance of a gallium oxide Schottky diode and its preparation method, so as to reduce the damage to the surface of the gallium oxide substrate by using a mixed solution of hydrofluoric acid and high potassium sulfate for wet etching thinning, and reduce the conduction resistance by preparing a patterned ohmic contact, thereby improving the device performance.

[0008] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0009] 1. A gallium oxide Schottky diode with reduced conduction resistance, from bottom to top, comprising: a cathode metal 1, a gallium oxide substrate 2, a gallium oxide lightly doped epitaxial layer 3 and an anode metal 4, characterized in that the cathode metal 1 adopts a zigzag ohmic contact pattern structure to reduce the conduction resistance and improve the device performance.

[0010] Further, the cathode metal adopts Ti / Au, and the thickness of the first layer of Ti near the gallium oxide substrate is 20-50 nm, and the thickness of the second layer of Au metal is 100-400 nm.

[0011] Further, the thickness of the gallium oxide substrate is 300-650 μm, the effective doping carrier concentration is 10 18 ~ 10 19 cm -3 , and the doping ion type is Si ion or Sn ion.

[0012] Further, the thickness of the gallium oxide lightly doped epitaxial layer is 3-15 μm, and the doping carrier concentration is 10 16 ~ 10 18 cm -3 .

[0013] Further, the anode metal of the Schottky diode adopts Ni / Au metal, and the thickness of the first layer of metal Ni is 45-60 nm, and the thickness of the second layer of metal Au is 200-400 nm.

[0014] Further, the annealing of the ohmic cathode metal is carried out in a nitrogen atmosphere, and the annealing temperature is 400-500℃, and the annealing time is 1-3 minutes.

[0015] 2. A method for manufacturing a gallium oxide Schottky diode with low conduction resistance, characterized in that it comprises the following steps:

[0016] 1) The gallium oxide substrate 2 is sequentially cleaned with acetone-isopropyl alcohol-deionized water;

[0017] 2) The gallium oxide substrate 2 is thinned by wet etching:

[0018] 2a) using a spinner to spin a layer of photoresist on the surface of the gallium oxide substrate 2 as a protective mask;

[0019] 2b) using 49% concentration of hydrofluoric acid and 75% to 90% concentration of high potassium sulfate to prepare a corrosion solution in a ratio of 1:1, immersing the gallium oxide substrate 2 with the protective mask into the corrosion solution, soaking for 8 to 15 hours, and corroding the gallium oxide substrate, reducing the 650 μm substrate to 200 to 400 μm;

[0020] 3) preparing a sawtooth-shaped ohmic contact pattern on the back of the thinned gallium oxide substrate 2:

[0021] 3a) using photolithography technology, using photoresist to form an ohmic lithography pattern on the back of the gallium oxide substrate 2;

[0022] 3b) setting a power of 100 W, an argon atmosphere, a processing time of 80 minutes, a pressure of 10 mtorr, and an ambient temperature of 25°C, and depositing 15 nm thick metal platinum on the ohmic lithography pattern of the gallium oxide substrate 2 under the magnetic control sputtering process conditions;

[0023] 3c) using a spinner to spin a layer of photoresist on the surface of the gallium oxide substrate 2 as a protective mask;

[0024] 3d) using 49% concentration of hydrofluoric acid and 75% concentration of high potassium sulfate to prepare a corrosion solution in a ratio of 1:1, immersing the gallium oxide substrate 2 with the protective mask into the corrosion solution, and forming a sawtooth-shaped ohmic contact pattern on the lower surface of the gallium oxide substrate 2 by catalyzing the reaction of metal platinum under the irradiation of ultraviolet light for 5 hours;

[0025] 3e) sequentially cleaning the gallium oxide substrate 2 with the sawtooth-shaped ohmic contact pattern with acetone, isopropyl alcohol, and deionized water;

[0026] 4) using the hydride vapor phase epitaxy technology HVPE method to epitaxially grow a lightly doped gallium oxide epitaxial layer 3 on the front surface of the cleaned gallium oxide substrate 2, depositing an ohmic cathode metal 1 on the back surface of the gallium oxide substrate using magnetic control sputtering to form a sawtooth-shaped ohmic contact structure, and performing ohmic annealing on the cathode metal 1;

[0027] 5) forming an anode pattern on the front surface of the gallium oxide lightly doped epitaxial layer 3 using photolithography technology, and depositing anode metal 4 according to the anode pattern using electron beam evaporation and peeling off the metal material outside the anode lithography pattern to complete the device fabrication.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] First, the application uses 49% concentration of hydrofluoric acid and 75%-90% concentration of high potassium sulfate to prepare a corrosion solution in a ratio of 1:1, and then immerse the gallium oxide substrate in the solution for corrosion. Compared with the traditional chemical mechanical polishing technology, the solution corrosion does not produce stress effect on the surface of the gallium oxide substrate, so that the depth thinning of the gallium oxide substrate can be realized. Meanwhile, the solution immersion corrosion does not have the mechanical grinding effect, so that the surface quality of the thinned substrate is good and the damage is small.

[0030] Second, the application uses the cathode ohmic metal with the sawtooth-shaped ohmic contact pattern structure, so that the on-resistance is reduced and the device performance is improved. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the existing gallium oxide Schottky diode.

[0032] Figure 2 It is a structural schematic diagram of the gallium oxide Schottky diode with low on-resistance according to the application.

[0033] Figure 3 It is an implementation flowchart of the gallium oxide Schottky diode according to the application. Figure 2 DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the technical solutions of the application, the application will be further described below in combination with the drawings and embodiments. However, the application is not limited to these embodiments, and those skilled in the art should understand that the application can also be implemented in other embodiments without these specific details.

[0035] With reference to Figure 2 , the gallium oxide Schottky diode prepared by the application comprises a Schottky diode cathode metal 1, a gallium oxide substrate 2, a gallium oxide lightly doped epitaxial layer 3 and an anode metal 4. Among them:

[0036] The cathode metal 1 is located at the back of the gallium oxide substrate 2, and adopts a sawtooth-shaped ohmic contact pattern, and the metal adopts Ti / Au, the thickness of Ti is 20-50 nm, and the thickness of Au is 100-400 nm;

[0037] The gallium oxide substrate 2 has a thickness of 200-400 μm and a doping concentration of 10 18 -10 19 cm -3 ;

[0038] The gallium oxide lightly doped epitaxial layer 3 is located on the gallium oxide substrate 2, and has a thickness of 3-15 μm and a doping concentration of 10 16 -10 18 cm -3 ;​

[0039] The anode metal 4 is located on the gallium oxide lightly doped epitaxial layer 3, and the metal is Ni / Au, the thickness of Ni is 45-60 nm, and the thickness of Au is 200-400 nm.

[0040] Referring to Figure 3 , the application discloses a gallium oxide Schottky diode with a sawtooth-shaped ohmic contact pattern structure. Figure 2 The following three embodiments of the device structure are given.

[0041] Embodiment one: a gallium oxide Schottky diode with a sawtooth-shaped ohmic contact pattern structure and a substrate thickness of 200 μm is prepared.

[0042] Step one: cleaning of the gallium oxide substrate material.

[0043] A gallium oxide substrate 2 with a thickness of 650 μm, an effective doped carrier concentration of 2×10 18 cm -3 , and Sn ions as the doped ion type is cleaned by using acetone-isopropyl alcohol-deionized water under ultrasonic intensity of 2.0 for 3 minutes, and then dried by using nitrogen.

[0044] Step two: thinning treatment of the cleaned gallium oxide substrate by using a wet etching technology.

[0045] 2.1) a spin coater is used to spin a layer of photoresist on the upper surface of the gallium oxide substrate as a protective mask, and the spin coating conditions are as follows: the spin coater rotates at a speed of 2000 rpm for 22 s, and after the spin coating is completed, a hot plate baking at 110°C is performed for 3 minutes to realize isolation and protection of the gallium oxide substrate.

[0046] 2.2) etching and thinning of the gallium oxide substrate:

[0047] 2.2.1) a 49% concentration of hydrofluoric acid and a 90% concentration of potassium persulfate are used to prepare an etching solution in a proportion of 1:1;

[0048] 2.2.2) the gallium oxide substrate with isolation and protection is placed in the solution for immersion etching, and the immersion time is 15 hours, so that the original gallium oxide substrate with a thickness of 650 μm is thinned to 200 μm;

[0049] 2.2.3) acetone-isopropyl alcohol-deionized water is used for ultrasonic cleaning under ultrasonic intensity of 2.0 for 3 minutes, and then dried by using nitrogen.

[0050] Step three: preparation of a sawtooth-shaped ohmic contact pattern on the back of the thinned gallium oxide substrate.

[0051] 3.1) ohmic patterning photoetching:

[0052] 3.1.1) Using photoetching technology, an ohmic photoetching pattern is prepared on the surface of the gallium oxide substrate using photoresist;

[0053] 3.1.2) Using a magnetron sputtering method, 15 nm thick metal platinum is deposited on the ohmic photoetching pattern of the gallium oxide substrate;

[0054] 3.1.3) Using an acetone solution, ultrasonic cleaning is performed for 3 minutes at an ultrasonic intensity of 2.0; using a deposition medium stripping solution, boiling is performed for 15 minutes at 60°C; using acetone-isopropyl alcohol-deionized water, ultrasonic cleaning is performed for 3 minutes at an ultrasonic intensity of 2.0, and then using nitrogen blowing, the metal platinum outside the photoetching pattern area is removed;

[0055] 3.2) Isolation and protection of the gallium oxide substrate.

[0056] Using a spinner, a layer of photoresist is spin-coated on the upper surface of the gallium oxide substrate (2) as a protective mask, and the spin-coating conditions are: spinner speed 2000 rpm, spin-coating for 22 s, and after spin-coating is completed, hot plate baking at 110°C for 3 minutes.

[0057] 3.3) Using 49% concentrated hydrofluoric acid and 75% concentrated potassium persulfate, a solution with a solution ratio of 1:1 is prepared;

[0058] 3.4) The gallium oxide material that has been subjected to substrate isolation and protection is placed in the solution prepared in 3.3) for etching, and ultraviolet light is used to irradiate the etching solution during the soaking process, and through a metal platinum catalytic reaction for 5 hours, a jagged ohmic contact pattern is formed on the lower surface of the gallium oxide substrate;

[0059] 3.5) After the solution etching of the substrate is completed, acetone-isopropyl alcohol-deionized water is used for ultrasonic cleaning for 3 minutes at an ultrasonic intensity of 2.0, and then nitrogen blowing is used for drying.

[0060] Step four: using the hydride vapor phase epitaxy (HVPE) method, a gallium oxide lightly doped epitaxial layer is prepared on the front surface of the cleaned gallium oxide substrate.

[0061] 4.1) In the high-temperature reaction zone of the HVPE vertical reactor, HCl and high-purity metal Ga are reacted at a temperature of 800°C to generate GaCl and GaCl3;

[0062] 4.2) 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 in the low-temperature reaction zone of the HVPE vertical reactor with the front surface facing upwards, and GaCl and GaCl3 are reacted with oxygen at a temperature of 600°C on the gallium oxide substrate to generate a gallium oxide lightly doped epitaxial layer 3 with a thickness of 10 μm and a doping concentration of 2×10 16 cm -3 .

[0063] Step five: Preparation of cathode ohmic metal.

[0064] The metal Ti / Au was deposited on the back of the gallium oxide substrate 2 by magnetron sputtering method, the thickness of the first layer of Ti was 20 nm, and the thickness of the second layer of Au metal was 400 nm, forming a cathode metal 1 with a sawtooth patterned ohmic.

[0065] The annealing furnace was used to anneal the cathode metal in a nitrogen atmosphere, the annealing temperature was 470°C, and the annealing time was 1 minute.

[0066] Step six: Preparation of anode Schottky metal 4.

[0067] 6.1) Using photolithography technology, a photoresist was used to prepare an anode pattern on the surface of the gallium oxide lightly doped epitaxial layer 3;

[0068] 6.2) The metal Ni / Au was deposited on the anode pattern by electron beam evaporation method, and the thickness of the first layer of metal Ni was 45 nm, and the thickness of the second layer of metal Au was 400 nm;

[0069] 6.3) The photoresist was washed off with N-methyl pyrrolidone solution, i.e. the metal material deposited on the gallium oxide lightly doped epitaxial layer 3 without photoresist pattern was removed, and the device was completed.

[0070] Example two: Preparation of a gallium oxide Schottky diode with a sawtooth ohmic contact pattern structure and a gallium oxide substrate thickness of 300 μm.

[0071] Step 1: Cleaning of gallium oxide material.

[0072] The thickness of the gallium oxide substrate 2 was selected to be 650 μm, the effective doping carrier concentration was 2×10 19 cm -3 , the doping ion type was Sn ion, and the gallium oxide substrate was cleaned by ultrasonic cleaning for 3 minutes under the condition of ultrasonic intensity 2.0 using acetone-isopropyl alcohol-deionized water, and then dried with nitrogen.

[0073] Step 2: Thinning of the cleaned gallium oxide substrate by wet etching technology.

[0074] 2a1) A spin coater was used to spin a layer of photoresist on the surface of the gallium oxide substrate as a protective mask at a speed of 2000 rpm and a spin coating time of 22 s, and after the spin coating was completed, a 110°C hot plate baking was performed for 3 minutes to realize the isolation and protection of the gallium oxide substrate.

[0075] 2a2) Gallium oxide substrate etching and thinning:

[0076] 2a2.1) Using 49% concentration of hydrofluoric acid and 90% concentration of high potassium sulfate, the etching solution is prepared in a ratio of 1:1;

[0077] 2a2.2) The isolated and protected gallium oxide substrate is immersed in the solution for etching, and the immersion time is 12 hours. The original gallium oxide substrate with a thickness of 650 μm is thinned to 300 μm;

[0078] 2a2.3) The gallium oxide substrate is cleaned with acetone-isopropyl alcohol-deionized water under ultrasonic intensity of 2.0 for 3 minutes, and then dried with nitrogen.

[0079] Step 3: Prepare a sawtooth-shaped ohmic contact pattern on the back of the thinned gallium oxide substrate.

[0080] 3a1) Ohmic pattern photoetching:

[0081] 3a1.1) Use photoetching technology to prepare an ohmic photoetching pattern on the back of the gallium oxide substrate using photoresist;

[0082] 3a1.2) Use a magnetron sputtering method to deposit metal platinum on the surface of the gallium oxide substrate to form a corrosion-resistant mask;

[0083] 3a1.3) Clean the gallium oxide substrate with acetone solution under ultrasonic intensity of 2.0 for 3 minutes, and then use deposition medium stripping liquid to cook at 60°C for 15 minutes. Then clean the gallium oxide substrate with acetone-isopropyl alcohol-deionized water under ultrasonic intensity of 2.0 for 3 minutes, and then dry it with nitrogen to remove the metal platinum outside the photoetching pattern area.

[0084] 3a2) Use a spinner to spin a layer of photoresist on the upper surface of the gallium oxide substrate as a protective mask at a speed of 2000 rpm and set the spin time to 22 seconds. After the spinning is completed, perform 110°C hot plate baking for 3 minutes to achieve isolation protection of the gallium oxide substrate;

[0085] 3a3) Use 49% concentration of hydrofluoric acid and 75% concentration of high potassium sulfate to prepare an etching solution in a ratio of 1:1;

[0086] 3a4) Put the gallium oxide material with substrate isolation protection into the solution for immersion etching. Use ultraviolet light to irradiate the etching solution during the immersion process. Through the metal platinum catalytic reaction for 5 hours, a sawtooth-shaped ohmic contact pattern is formed on the lower surface of the gallium oxide substrate;

[0087] 3a5) Clean the substrate after solution etching with acetone-isopropyl alcohol-deionized water under ultrasonic intensity of 2.0 for 3 minutes, and then dry it with nitrogen.

[0088] Step 4: A gallium oxide lightly doped epitaxial layer is prepared on the front surface of the cleaned gallium oxide substrate by using the hydride vapor phase epitaxy (HVPE) method.

[0089] 4a) In the high temperature reaction zone of the HVPE vertical reactor, HCl reacts with high purity metal Ga at 850°C to produce GaCl and GaCl3;

[0090] 4b) The GaCl and GaCl3 produced in the high temperature reaction zone are pushed into the low temperature reaction zone, and the gallium oxide substrate 2 is placed in the low temperature reaction zone of the HVPE vertical reactor with the front surface facing upwards, so that the GaCl and GaCl3 react with oxygen at 650°C to produce a gallium oxide epitaxial layer 3 on the gallium oxide substrate, with a thickness of 8 μm and a doping concentration of 2×10 17 cm -3 .

[0091] Step 5: Preparation of cathode ohmic metal.

[0092] The metal Ti / Au is deposited on the back surface of the gallium oxide substrate 2 by using the magnetron sputtering method, with the thickness of the first layer of Ti being 45 nm and the thickness of the second layer of Au being 400 nm, forming a cathode metal 1 with a sawtooth patterned ohmic.

[0093] The cathode metal is annealed in an annealing furnace under a nitrogen atmosphere, with the annealing temperature being 470°C and the annealing time being 2 minutes.

[0094] Step 6: Preparation of anode Schottky metal.

[0095] 6a1) An anode pattern is prepared on the surface of the gallium oxide lightly doped epitaxial layer 3 by using photoetching technology and photoresist.

[0096] 6a2) The metal Ni / Au is deposited on the anode pattern by using the electron beam evaporation method, with the thickness of the first layer of metal Ni being 45 nm and the thickness of the second layer of metal Au being 400 nm.

[0097] 6a3) The photoresist is washed away with N-methyl pyrrolidone solution, i.e. the metal material deposited on the gallium oxide lightly doped epitaxial layer 3 without the photoetching pattern is removed, completing the device fabrication.

[0098] Example Three: Gallium oxide Schottky diode with a sawtooth ohmic contact pattern structure and a gallium oxide substrate thickness of 400 μm.

[0099] Step A: Cleaning of gallium oxide material.

[0100] The gallium oxide substrate 2 with a thickness of 650 μm and an effective doping carrier concentration of 1×10 19 cm -3, the doping ion species is Sn ion, and the cleaned gallium oxide substrate is ultrasonically cleaned in acetone-isopropyl alcohol-deionized water under an ultrasonic intensity of 2.0 for 3 minutes, and then dried by blowing nitrogen.

[0101] Step B: The cleaned gallium oxide substrate is thinned by using a wet etching technique.

[0102] B1) The spin coater speed is set to 2000 rpm, and the spin coating time is set to 22 s. A photoresist is spin-coated on the upper surface of the gallium oxide substrate as a protective mask, and after the spin coating is completed, 110°C hot plate baking is performed for 3 minutes to achieve isolation and protection of the gallium oxide substrate.

[0103] B2) Gallium oxide substrate etching and thinning:

[0104] B2.1) A 49% concentration of hydrofluoric acid and a 75% concentration of potassium persulfate are used to prepare an etching solution in a ratio of 1:1;

[0105] B2.2) The gallium oxide substrate with isolation protection is immersed in the solution for 8 hours for etching, and the original 650μm thick gallium oxide substrate is thinned to 400μm;

[0106] B2.3) The thinned gallium oxide substrate is ultrasonically cleaned in acetone-isopropyl alcohol-deionized water under an ultrasonic intensity of 2.0 for 3 minutes, and then dried by blowing nitrogen.

[0107] Step C: Sawtooth-shaped ohmic contact patterns are prepared on the back of the thinned gallium oxide substrate.

[0108] C1) Ohmic patterning photoetching.

[0109] C1.1) An ohmic photoetching pattern is prepared on the back of the gallium oxide substrate using a photoresist by using a photoetching technique;

[0110] C1.2) A magnetron sputtering method is used to deposit metal platinum on the surface of the gallium oxide substrate to form a corrosion-resistant mask;

[0111] C1.3) The photoetching pattern area is cleaned by using acetone solution under an ultrasonic intensity of 2.0 for 3 minutes, using deposition medium stripping solution at 60°C for 15 minutes, and then using acetone-isopropyl alcohol-deionized water under an ultrasonic intensity of 2.0 for 3 minutes, and then dried by blowing nitrogen.

[0112] C2) A spin coater with a speed of 2000 rpm is used to spin-coat a layer of photoresist on the upper surface of the gallium oxide substrate (2) for 22 s to form a protective mask, and after the spin coating is completed, 110°C hot plate baking is performed for 3 minutes.

[0113] C3) using 49% concentration of hydrofluoric acid and 75% concentration of high potassium sulfate to prepare a solution with a ratio of 1:1, and then prepare a corrosion solution;

[0114] C4) Put the gallium oxide material for substrate isolation protection into the solution for corrosion. During the soaking process, use ultraviolet light to irradiate the corrosion solution. Form a jagged ohmic contact pattern under the bottom surface of the gallium oxide substrate through a platinum metal catalytic reaction for 5 hours. Then, use acetone-isopropyl alcohol-deionized water to ultrasonically clean the gallium oxide substrate for 3 minutes under the condition of an ultrasonic intensity of 2.0. Finally, use nitrogen to dry the gallium oxide substrate.

[0115] Step D: Use the hydride vapor phase epitaxy (HVPE) method to prepare a lightly doped gallium oxide epitaxial layer on the front surface of the cleaned gallium oxide substrate.

[0116] D1) In the high-temperature reaction zone of the HVPE vertical reactor, react HCl with high-purity metal Ga at a temperature of 900°C to generate GaCl and GaCl3.

[0117] D2) Push the generated GaCl and GaCl3 in the high-temperature reaction zone into the low-temperature reaction zone. Place the gallium oxide substrate 2 with the front surface facing up in the low-temperature reaction zone of the HVPE vertical reactor. Make GaCl and GaCl3 react with oxygen at a temperature of 500°C to generate a gallium oxide epitaxial layer 3 with a thickness of 9 μm and a doping concentration of 1×10 16 cm -3 on the gallium oxide substrate.

[0118] Step E: Prepare a cathode ohmic metal.

[0119] Use the magnetron sputtering method to deposit a total thickness of 390 nm of metal Ti / Au on the back surface of the gallium oxide substrate 2, where the thickness of the first layer of Ti close to the gallium oxide substrate layer is 40 nm, and the thickness of the second layer of Au metal is 350 nm, forming a cathode metal 1 with a jagged patterned ohmic.

[0120] Step F: Use an annealing furnace to anneal the cathode metal under a nitrogen atmosphere, with an annealing temperature of 500°C and an annealing time of 1 minute.

[0121] Step G: Prepare an anode Schottky metal.

[0122] Use photolithography technology to first prepare an anode pattern on the surface of the gallium oxide epitaxial layer 3 using photoresist. Then, use the electron beam evaporation method to sequentially deposit a thickness of 45 nm of Ni metal and a thickness of 400 nm of Au on the anode pattern, forming an anode metal. Finally, use N-methyl pyrrolidone solution to wash off the photoresist, i.e., remove the metal material deposited on the gallium oxide epitaxial layer 3 without a photoresist pattern, to complete the device fabrication.

[0123] The above description is only three specific examples of the present application, and does not constitute any limitation on the present application, and it is obvious that after understanding the content and principles of the present application, those skilled in the art can make various modifications and changes in form and details without departing from the principles and structures of the present application, for example, the thickness of the gallium oxide substrate can be accurately controlled according to the ratio of hydrofluoric acid to high potassium sulfate solution and the soaking time; the preparation method of the anode and cathode metals is not limited to electron beam evaporation, but also can use any one of the methods such as magnetron sputtering or thermal evaporation; but these modifications and changes based on the idea of the present application are still within the protection scope of the claims of the present application.

Claims

1. A method for fabricating a gallium oxide Schottky diode with reduced on-resistance, characterized in that, The method comprises the following steps: 1) sequentially performing acetone-isopropyl alcohol-deionized water cleaning on the gallium oxide substrate (2); 2) thinning the gallium oxide substrate (2) by wet etching: 2a) using a glue spinner to spin a layer of photoresist on the upper surface of the gallium oxide substrate (2) as a protective mask; 2b) using 49% concentration hydrofluoric acid and 75%-90% concentration potassium persulfate to prepare an etching solution in a 1:1 ratio, immersing the gallium oxide substrate (2) with the protective mask in the etching solution, and soaking for 8-15 hours to etch the gallium oxide substrate, thereby reducing the 650 μm substrate to 200-400 μm; 3) preparing a sawtooth-shaped ohmic contact pattern on the back of the thinned gallium oxide substrate (2): 3a) using a photoetching technique to form an ohmic photoetching pattern on the back of the gallium oxide substrate (2) using photoresist; 3b) setting a power of 100 W, processing for 80 minutes in an argon atmosphere, a pressure of 10 mtorr, and an ambient temperature of 25 °C, and depositing a 15 nm thick metal platinum on the ohmic photoetching pattern of the gallium oxide substrate (2) under the magnetic control sputtering process conditions; 3c) using a glue spinner to spin a layer of photoresist on the upper surface of the gallium oxide substrate (2) as a protective mask; 3d) using 49% concentration hydrofluoric acid and 75% concentration potassium persulfate to prepare an etching solution in a 1:1 ratio, immersing the gallium oxide substrate (2) with the protective mask in the etching solution, and forming a sawtooth-shaped ohmic contact pattern on the lower surface of the gallium oxide substrate (2) by catalyzing the reaction of the metal platinum under the irradiation of ultraviolet light for 5 hours; 3e) sequentially performing acetone-isopropyl alcohol-deionized water cleaning on the gallium oxide substrate (2) with the sawtooth-shaped ohmic contact pattern; 4) using the hydride vapor phase epitaxy (HVPE) method to epitaxially grow a lightly doped gallium oxide epitaxial layer (3) on the front surface of the cleaned gallium oxide substrate (2), depositing an ohmic cathode metal (1) on the back surface of the gallium oxide substrate using magnetic control sputtering, forming a sawtooth-shaped ohmic contact structure, and performing ohmic annealing on the cathode metal (1); 5) forming an anode pattern on the front surface of the gallium oxide lightly doped epitaxial layer (3) using a photoetching process, depositing an anode metal (4) according to the anode photoetching pattern using electron beam evaporation, and stripping the metal material outside the anode photoetching pattern to complete the device fabrication.

2. The method of claim 1, wherein, In step 4), the hydride vapor phase epitaxy (HVPE) method is used to epitaxially grow a lightly doped gallium oxide epitaxial layer (3) on the front surface of the cleaned gallium oxide substrate (2), which is implemented as follows: 4a) setting the hydride vapor phase epitaxy (HVPE) process conditions: in an ammonia atmosphere, hydrogen chloride gas and high-purity metal Ga are reacted to generate GaCl and GaCl3 in the high-temperature reaction zone of the hydride vapor phase epitaxy (HVPE) vertical reactor at a temperature of 800-900 °C; 4b) placing the cleaned gallium oxide substrate (2) into the HVPE vertical reactor; 4c) Pushing the GaCl and GaCl3 generated in the high-temperature reaction zone into the low-temperature reaction zone, and placing the gallium oxide substrate (2) with the front face upward in the low-temperature reaction zone of the HVPE vertical reactor, and making the products GaCl and GaCl3 in the high-temperature reaction zone react with oxygen at a temperature of 500-650 ℃ to generate a gallium oxide lightly doped epitaxial layer (3) on the gallium oxide substrate (2).

3. The method of claim 2, wherein, The step 4) adopts magnetron sputtering to deposit an ohmic cathode metal on the back surface of the gallium oxide substrate, and the process conditions are as follows: the power is 100-300 W, the sputtering time is 30-90 minutes, the pressure is 6-12 mtorr, and the ambient temperature is 25 ℃.

4. The method of claim 2, wherein, The step 4) adopts magnetron sputtering to deposit an ohmic cathode metal on the back surface of the gallium oxide substrate, and the process conditions are as follows: the power is 100-300 W, the sputtering time is 30-90 minutes, the pressure is 6-12 mtorr, and the ambient temperature is 25 ℃.

5. A gallium oxide Schottky diode prepared according to the method of claim 1, comprising, from bottom to top: The cathode metal (1), the gallium oxide substrate (2), the gallium oxide lightly doped epitaxial layer (3), and the anode metal (4) are characterized in that the cathode metal (1) adopts a sawtooth ohmic contact pattern structure to reduce the on-resistance and improve the device performance.

6. The diode of claim 5, wherein The cathode metal (1) adopts Ti / Au, and the thickness of the first layer of Ti close to the gallium oxide substrate (2) is 20-50 nm, and the thickness of the second layer of Au metal is 100-400 nm.

7. The diode of claim 5, wherein The gallium oxide substrate (2) has a thickness of 200 to 400 μm, an effective doped carrier concentration of 10 18 ~10 19 cm -3 , and a doped ion species of Si ions or Sn ions.

8. The diode of claim 5, wherein The thickness of the lightly doped epitaxial layer (3) is 3-15 μm, and the doping carrier concentration is 10 16 ~10 18 cm -3 .

9. The diode of claim 5, wherein The anode metal (4) adopts Ni / Au metal, and the thickness of the first layer of metal Ni is 45-60 nm, and the thickness of the second layer of metal Au is 200-400 nm.

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