Gallium oxide pn diode based on self-center to four-week gradual change p-type doping concentration and preparation method

Abstract

The application discloses a gallium oxide Pn diode based on a self-center-to-fourth-corner gradual P-type doping concentration structure and a preparation method, and mainly solves the problem that the prior art seriously increases the forward conduction resistance and power consumption of a device while improving the reverse breakdown voltage of the device. From bottom to top, the gallium oxide Pn diode comprises a cathode ohmic metal (1), a gallium oxide substrate (2), a gallium oxide drift layer (3), a P-type semiconductor layer (4), a high-doping-concentration P-type semiconductor layer (5) and an anode (6), wherein the P-type semiconductor layer is formed by sequentially depositing a plurality of semiconductor materials with different doping concentrations on the gallium oxide drift layer in the order of gradually increasing doping concentration from the center to the periphery, so as to reduce the peak electric field at the edge of the gallium oxide drift layer and the interior of the P-type semiconductor layer, form a good ohmic contact, and realize the reduction of the conduction resistance of the device while improving the reverse breakdown voltage of the device. The gallium oxide Pn diode improves the figure of merit of the gallium oxide device and can be used in electronic systems.

Description

TECHNICAL FIELD

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

[0002] Gallium oxide is a new type of ultra-wide bandgap semiconductor material. Due to its large bandgap of 4.6-4.9 eV and high critical breakdown field strength of 8 MV / cm, gallium oxide semiconductor material can be used to prepare high-power devices. With the continuous progress of science and technology, the performance of traditional third-generation semiconductor GaN and SiC power devices cannot meet the higher performance requirements in the fields of communication, power electronics, signal processing, aerospace, etc. However, gallium oxide power devices have lower on-resistance and lower power consumption, and have higher Baliga figure of merit under the same breakdown voltage.

[0003] At present, gallium oxide power devices mainly include diodes and triodes, among which diodes mainly include Schottky diodes and heterojunction pn diodes. A pn diode is formed by a p-type semiconductor and an n-type semiconductor, and a space charge layer is formed on both sides of the interface, which is beneficial to the operation of minority carriers and is widely used in various rectifier circuits, detection circuits, voltage stabilizing circuits and modulation circuits.

[0004] Since it is difficult to achieve P-type doping of gallium oxide, other P-type semiconductor materials such as nickel oxide, copper oxide and tin oxide are currently combined with n-type gallium oxide to form heterojunction pn diodes. Two very important device parameters for measuring the performance of diodes are reverse breakdown voltage and on-resistance. The larger the reverse breakdown voltage or the smaller the on-resistance, the better the performance of the device. However, the forward characteristics and breakdown voltage of gallium oxide diodes are still far from the limit of gallium oxide, and the Baliga figure of merit BFOM of gallium oxide devices is much lower than the ideal value, which affects the high-power output performance and limits its application in high-voltage fields.

[0005] Ma Xiaohua et al. in the patent document with the application number 202111069074.7 "A high-breakdown-voltage gallium oxide power diode and a preparation method thereof" proposed that a thin layer of NiO with P-type characteristics and a drift layer of β-Ga2O3 form a heterojunction PN structure to reduce the peak electric field at the edge of the device, improve the interface characteristics of the anode metal and gallium oxide, reduce the reverse leakage current, and improve the breakdown voltage of the gallium oxide diode.

[0006] Lu Xing et al. in the patent document with the application number 201710057175.X "A gallium oxide-based heterojunction PN diode and a preparation method thereof" proposed that an amorphous or polycrystalline p-type oxide semiconductor layer and a single-crystal n-type doped gallium oxide voltage-resistant layer form a heterojunction PN to reduce the reverse leakage current and improve the breakdown voltage of the gallium oxide diode.

[0007] The above two methods can improve the reverse breakdown voltage of the device, but at the same time, the forward conduction resistance of the device is also greatly increased, and the baritt gain of the device cannot be maximized. SUMMARY

[0008] The present application aims at the deficiencies of the prior art, and provides a gallium oxide pn diode based on a self-center to four-corner gradually changing p-type doping concentration and a preparation method, so as to improve the reverse breakdown voltage, reduce the conduction resistance, and improve the baritt gain of the gallium oxide device.

[0009] The technical idea of the present application is that the p-type doping concentration of the p-type semiconductor layer in the pn junction is gradually changed from the center to the four corners, so that after the low-doped gallium oxide drift layer is in contact with the p-type semiconductor layer with a gradually changing doping concentration, the p-type semiconductor with a high-doped concentration at the four corners relieves the peak electric field at the edge of the gallium oxide drift layer and the peak electric field inside the p-type semiconductor layer with a low-doped concentration, so as to improve the breakdown voltage of the device; at the same time, after the anode metal is in contact with the p-type semiconductor layer with a high-doped concentration, it is easier to form an ohmic contact, so as to improve the baritt gain of the gallium oxide device.

[0010] According to the above idea, the technical scheme of the present application is as follows:

[0011] 1. A gallium oxide pn diode based on a self-center to four-corner gradually changing p-type doping concentration, from bottom to top, comprising: a cathode ohmic metal, a gallium oxide substrate, a gallium oxide drift layer, a p-type semiconductor layer, a high-doped concentration p-type semiconductor layer, and an anode metal, characterized in that the p-type semiconductor layer is a gradually changing doped p-type semiconductor layer formed by depositing a plurality of different doping concentration semiconductor materials from the center to the four corners in order of low to high doping concentration, so as to improve the reverse breakdown voltage of the device while reducing the conduction resistance of the device, and improve the baritt gain of the gallium oxide device.

[0012] As a preferred, the gradually changing doped p-type semiconductor layer has a thickness of 5-30 nm, and the gradually changing doping concentration ranges from 1x10 16 cm -3 to 1x10 19 cm -3 .

[0013] As a preferred, the cathode ohmic metal adopts Ti / Au metal, and the thickness of the first layer Ti close to the gallium oxide substrate layer is 20-50 nm, and the thickness of the second layer Au metal is 100-400 nm;

[0014] As a preferred, the gallium oxide substrate has a thickness of 300-650 μm, and an effective doped carrier concentration of 10 18-10 20 cm -3 , the doping ion types are Si ions or Sn ions.

[0015] Preferably, the gallium oxide drift layer has a thickness of 3-15 μm and a doping carrier concentration of 10 16 -10 18 cm -3 .

[0016] Preferably, the optional p-type semiconductor materials in the gradient doped P-type semiconductor layer and the high doping concentration P-type semiconductor layer include nickel oxide, copper oxide and tin oxide. The thickness of the high doping concentration P-type semiconductor layer is 3-20 nm, and the doping carrier concentration is 10 19 -10 20 cm -3 .

[0017] Preferably, the anode metal is 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.

[0018] 2. A method for fabricating a gallium oxide pn diode with a P-type doping concentration gradually varying from the center to the periphery, characterized by comprising the following steps:

[0019] 1) Cleaning the gallium oxide substrate with acetone, isopropyl alcohol, and deionized water in sequence;

[0020] 2) Using hydride vapor phase epitaxy (HVPE) to epitaxially form a gallium oxide drift layer on the front side of the cleaned gallium oxide substrate, depositing an ohmic cathode metal on the back side by magnetron sputtering in an argon atmosphere, and performing ohmic annealing on the ohmic cathode metal;

[0021] 3) Depositing a P-type semiconductor layer with a graded doping concentration on the gallium oxide drift layer:

[0022] 3a) performing a photolithography operation on the front side of the gallium oxide drift layer to form a circular pattern;

[0023] 3b) setting the magnetron sputtering process conditions to 100-150 W power, 5%-50% oxygen to argon ratio, 10-90 minutes processing time, 4-10 mtorr pressure, and 25° C. ambient temperature;

[0024] 3c) forming a circular P-type material with a lower doping concentration by magnetron sputtering according to the circular pattern of the first photolithography, and stripping off the P-type material deposited on the gallium oxide drift layer where there is no photolithography pattern;

[0025] 3d) performing secondary photolithography to form a circular pattern on the front surface of the gallium oxide drift layer, increasing the ratio of oxygen to argon in the magnetron sputtering process, and depositing a circular ring of p-type material that surrounds the previously deposited circular pattern using magnetron sputtering according to the secondary photolithographic pattern, wherein the p-type doping concentration is higher than that of the previously deposited circular pattern, and then stripping and removing the p-type material deposited in the area of ​​the gallium oxide drift layer without the photolithographic pattern;

[0026] 3e) performing n photolithography steps on the front surface of the gallium oxide drift layer to form a circular pattern, increasing the ratio of oxygen to argon in the magnetron sputtering process, and depositing a circular ring of p-type material that surrounds the previously deposited n-1 circular rings using magnetron sputtering according to the circular pattern of the n photolithography steps, wherein the p-type doping concentration of the circular ring is higher than that of the previously deposited n-1 circular rings, and then stripping and removing the P-type material deposited in the area of ​​the gallium oxide drift layer without the photolithography pattern; repeating this step until the total width of the p-type material deposited according to the photolithography pattern is equal to the width of the anode metal, thereby forming a P-type semiconductor layer with a doping concentration that increases from low to high from the center to the periphery, where n is an integer greater than 2;

[0027] 4) Depositing a high-doping-concentration P-type semiconductor layer on the front side of the P-type semiconductor layer with doping concentrations increasing from low to high in the center and around it:

[0028] 4a) forming a pattern on the front surface of the P-type semiconductor layer using a photolithography process;

[0029] 4b) Setting magnetron sputtering process conditions: power of 100-150 W, oxygen to argon ratio of 50%-80%, processing time of 10-90 minutes, pressure of 4-10 mtorr, and ambient temperature of 25° C.;

[0030] 4c) depositing a high-doping concentration P-type semiconductor layer on the P-type semiconductor layer by magnetron sputtering according to the process conditions set in 4b) according to the photolithography pattern;

[0031] 5) An anode pattern is formed on the front surface of the high-doping concentration P-type semiconductor layer using a photolithography process, and an anode metal is deposited using electron beam evaporation according to the anode pattern to complete device fabrication.

[0032] Compared with the traditional gallium oxide pn diode, the present invention has the following advantages due to the use of a P-type semiconductor layer with a gradually changing doping concentration from the center to the periphery:

[0033] First, the high-doping concentration semiconductors on the four sides of the P-type semiconductor layer with a gradient doping concentration from the center to the four sides contact the edge of the gallium oxide drift layer, which can alleviate the peak electric field at the edge of the gallium oxide drift layer and improve the reverse breakdown voltage of the device.

[0034] Second, the low-doping concentration semiconductor in the center of the P-type semiconductor layer with a gradient doping concentration from the center to the surrounding areas can alleviate the peak electric field inside the P-type semiconductor and improve the reverse breakdown voltage of the device.

[0035] Third, after the high-doping concentration p-type semiconductor layer contacts the anode metal above it, an excellent ohmic contact can be formed, thereby reducing the on-resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic structural diagram of a gallium oxide pn diode in the prior art;

[0037] Figure 2 Schematic diagram of the structure of the gallium oxide pn diode based on the present invention with a gradually changing P-type doping concentration from the center to the periphery;

[0038] Figure 3 Made for this invention Figure 2 Implementation flow chart of gallium oxide pn diode. DETAILED DESCRIPTION

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention, the present invention is further described below with reference to the embodiments and accompanying drawings required for the technical description of the present invention. However, the present invention is not limited to these embodiments, and those skilled in the art will appreciate that the present invention can also be implemented in other embodiments without these specific details.

[0040] Reference Figure 2 The present invention is based on a gallium oxide pn diode with a gradient P-type doping concentration from the center to the periphery, comprising: a cathode ohmic metal 1, a gallium oxide substrate 2, a gallium oxide drift layer 3, a gradient doping concentration P-type semiconductor layer 4, a high doping concentration P-type semiconductor layer 5, and an anode metal 6. Among them:

[0041] The cathode ohmic metal 1 is located on the back of the gallium oxide substrate 2, and the metal is Ti / Au, with a thickness of Ti of 20nm and a thickness of Au of 400nm;

[0042] The thickness of the gallium oxide substrate 2 is 650 μm, and its doping concentration is 2×10 19 cm -3 ;

[0043] The gallium oxide drift layer 3 is located on the gallium oxide substrate 2, and its thickness is 10 μm and its doping concentration is 1×10 16 cm -3 ;

[0044] The graded doping concentration P-type semiconductor 4 is located on the gallium oxide drift layer 3. It uses a variety of NiO materials with different doping concentrations to achieve a gradual increase in doping concentration from the center to the periphery, so as to increase the reverse breakdown voltage of the device while reducing the on-resistance of the device and improve the Baliga figure of merit of the gallium oxide device. For example, three NiO materials with a thickness of 27nm can be used, and the doping concentration of the central circular NiO material is 1×1018 cm -3 The doping concentration of NiO material in the first inner ring is 5×10 18 cm -3 The doping concentration of the NiO material in the second outer ring is 1×10 19 cm -3 ;

[0045] The high doping concentration p-type semiconductor layer 5 is located on the gradient doping concentration P-type semiconductor 4, and its thickness is 5nm and the doping concentration is 1×10 19 cm -3 ;

[0046] The anode metal 6 is located on the high-doping concentration p-type semiconductor layer 5, and the metal is Ni / Au, with a Ni thickness of 45 nm and an Au thickness of 400 nm.

[0047] Reference Figure 3 The present invention provides a method for producing Figure 2 The following three embodiments of the device structure are as follows:

[0048] Example 1: A gallium oxide pn diode is fabricated, comprising a p-type semiconductor layer composed of three NiO materials with different doping concentrations, with the doping concentration gradually increasing from the center to the periphery.

[0049] Step 1: Cleaning the gallium oxide substrate.

[0050] The thickness is selected as 650μm and the effective doping carrier concentration is 10 18 cm -3 , a gallium oxide substrate 2 in which the doped ion species is Sn ion.

[0051] The sample was ultrasonicated in acetone, isopropanol, and deionized water for 5 minutes, and then dried with nitrogen gas.

[0052] Step 2: Using the hydride vapor phase epitaxy (HVPE) method, a gallium oxide drift layer is grown on the front side of the cleaned gallium oxide substrate.

[0053] First, in the high-temperature reaction zone of the HVPE vertical reactor, HCl reacts with high-purity metallic Ga at 850°C to produce GaCl and GaCl3;

[0054] Then, 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. GaCl and GaCl3 react with oxygen at 600°C on the gallium oxide substrate 2 to generate a 10 μm thick and 1×10 16 cm -3 Gallium oxide drift layer 3.

[0055] Step 3: Prepare cathode ohmic metal.

[0056] In an inert gas argon atmosphere, a magnetron sputtering method is used with the process conditions set to 100 W power, 40 minutes sputtering time, 8 mtorr pressure, and 25°C ambient temperature to deposit metal Ti / Au on the back side of the gallium oxide substrate 2. The thickness of the first metal Ti layer close to the gallium oxide substrate layer is 20 nm, and the thickness of the second metal Au layer is 400 nm, forming a cathode ohm 1.

[0057] Step 4: Use an annealing furnace to anneal the cathode ohmic metal in a nitrogen atmosphere at an annealing temperature of 470° C. for 1 minute.

[0058] Step 5: magnetron sputtering is used to deposit a P-type semiconductor layer with a gradient doping concentration.

[0059] First, a photoresist was used to perform the first photolithography on the gallium oxide drift layer 3 to prepare a circular pattern. The circular pattern was magnetron sputtered for 90 minutes under the process conditions of 150W power, 33% oxygen to argon ratio, 10mtorr pressure, and 25°C ambient temperature to form a doping concentration of 1×10 18 cm -3 Then, an N-methylpyrrolidone solution is used to strip off the NiO material deposited on the gallium oxide drift layer 3 without the photolithographic pattern;

[0060] Then, a second photolithography was performed on the gallium oxide drift layer 3 using photoresist to prepare a circular ring pattern. The circular ring pattern was magnetron sputtered for 90 minutes under the process conditions of 150W power, 40% oxygen to argon ratio, 10mtorr pressure, and 25°C ambient temperature to form a doping concentration of 5×10 18 cm -3 The first circle wraps the NiO ring of the central circular material; then the NiO material deposited on the gallium oxide drift layer 3 without the photolithographic pattern is stripped off using N-methylpyrrolidone solution;

[0061] Finally, a third photolithography was performed on the gallium oxide drift layer 3 using photoresist to prepare a new circular pattern. The circular pattern was magnetron sputtered for 90 minutes under the process conditions of 150W power, 50% oxygen to argon ratio, 10mtorr pressure, and 25℃ ambient temperature to form a doping concentration of 1×10 19 cm -3The second circle of NiO ring is wrapped around the first circle of NiO ring; the N-methyl pyrrolidone solution is used to peel off the NiO material deposited on the non-photolithographic patterned area of the gallium oxide drift layer 3, thereby forming the P-type semiconductor layer 4 with gradually increasing doping concentration from the center to the periphery by using three different doping concentrations of NiO material.

[0062] Step six: magnetron sputtering deposition of high-doped p-type semiconductor layer 5.

[0063] First, the photoresist is used to prepare a pattern on the P-type semiconductor layer 4 with gradually increasing doping concentration by using the photoetching technology;

[0064] Then, the NiO material with a doping concentration of 10 19 cm -3 is formed on the P-type semiconductor layer 4 with gradually increasing doping concentration by using the magnetron sputtering according to the photoetching pattern under the conditions of a power of 100 W, an oxygen-to-argon ratio of 50%, a pressure of 10 mtorr, an ambient temperature of 25°C, and a processing time of 30 minutes.

[0065] Finally, the N-methyl pyrrolidone solution is used to peel off the NiO material deposited on the P-type semiconductor layer 4 without photoetching pattern, thereby forming the high-doped p-type semiconductor layer 5.

[0066] Step seven: preparation of anode metal 6.

[0067] First, the photoresist is used to prepare an anode pattern on the high-doped p-type semiconductor layer 5 by using the photoetching technology;

[0068] Then, the metal Ni / Au is deposited on the anode pattern by using the electron beam evaporation method in an inert gas argon atmosphere under the process conditions of a power of 150 W, an evaporation time of 40 minutes, a vacuum degree of 10 - 6 TORR, and an ambient temperature of 25°C, wherein the thickness of the first layer of metal Ni is 45 nm, and the thickness of the second layer of metal Au is 400 nm.

[0069] Finally, the photoresist is washed off and peeled off by using the N-methyl pyrrolidone solution, thereby completing the device fabrication.

[0070] Example two: fabrication of a gallium oxide pn diode containing a P-type semiconductor layer with gradually increasing doping concentration from the center to the periphery, which is composed of four different doping concentrations of copper oxide material.

[0071] Step 1: cleaning of the gallium oxide substrate.

[0072] The gallium oxide substrate with a thickness of 450 μm and an effective doped carrier concentration of 10 18 cm -3, a gallium oxide substrate doped with Sn ions was sonicated in acetone-isopropanol-deionized water for 5 minutes, and then blown dry with nitrogen.

[0073] Step 2: Using the hydride vapor phase epitaxy (HVPE) method, a gallium oxide drift layer is grown on the front side of the cleaned gallium oxide substrate.

[0074] 2.1) In the high temperature reaction zone of the HVPE vertical reactor, HCl is reacted with high purity metallic Ga at 850°C to produce GaCl and GaCl3;

[0075] 2.2) The GaCl and GaCl3 generated in the high-temperature reaction zone are pushed into the low-temperature reaction zone. The gallium oxide substrate 2 is then placed face up in the low-temperature reaction zone of the HVPE vertical reactor. GaCl and GaCl3 react with oxygen at 600°C on the gallium oxide substrate 2 to generate a 4 μm thick and 2×10 16 cm -3 Gallium oxide drift layer 3.

[0076] Step 3: Prepare cathode ohmic metal.

[0077] In an inert gas argon atmosphere, a magnetron sputtering method is used with the process conditions of sputtering power of 100 W, time of 30 minutes, pressure of 6 mtorr, and ambient temperature of 25°C to deposit metal Ti / Au on the back side of the gallium oxide substrate 2, with the thickness of the first metal Ti layer close to the gallium oxide substrate layer being 20 nm, and the thickness of the second metal Au layer being 300 nm, to form a cathode ohm 1.

[0078] Step 4: Anneal the cathode ohmic metal at 470° C. for 1 minute in a nitrogen atmosphere using an annealing furnace.

[0079] Step 5: depositing a P-type semiconductor layer 4 with a gradient doping concentration by magnetron sputtering.

[0080] 5.1) A first photolithography was performed on the gallium oxide drift layer 3 using a photoresist to prepare a circular pattern. The circular pattern was subjected to magnetron sputtering for 80 minutes under the process conditions of 150 W power, 33% oxygen to argon ratio, 10 mtorr pressure, and 25°C ambient temperature to form a doping concentration of 1×10 18 cm -3 Then, an acetone organic solution is used to strip off the copper oxide material deposited on the gallium oxide drift layer 3 without the photolithographic pattern;

[0081] 5.2) A second photolithography was performed on the gallium oxide drift layer 3 using photoresist to prepare a first circular pattern. The process conditions were set to 150 W, 40% oxygen to argon ratio, 10 mtorr pressure, and 25°C ambient temperature. The circular pattern was magnetron sputtered for 80 minutes to form a doping concentration of 5×10 18 cm -3 The first circle wraps the copper oxide ring of the central circular material; then, an acetone organic solution is used to peel off the copper oxide material deposited on the gallium oxide drift layer 3 without the photolithographic pattern;

[0082] 5.3) A third photolithography was performed on the gallium oxide drift layer 3 using photoresist to prepare a second circular ring pattern. The process conditions were set to 150 W, 45% oxygen to argon ratio, 10 mtorr pressure, and 25°C ambient temperature. The second circular ring pattern was subjected to magnetron sputtering for 80 minutes to form a doping concentration of 8×10 18 cm -3 The second circle of copper oxide rings wraps the first circle of ring material; and then an acetone organic solution is used to peel off the copper oxide material deposited on the gallium oxide drift layer 3 without the photolithographic pattern;

[0083] 5.4) A fourth photolithography was performed on the gallium oxide drift layer 3 using photoresist to form a third circular ring pattern. The process conditions were set to 150 W, 50% oxygen to argon ratio, 10 mtorr pressure, and 25°C ambient temperature. The third circular ring was subjected to magnetron sputtering for 80 minutes to form a doping concentration of 1×10 19 cm -3 The third circle of copper oxide wraps the second circle of ring material; then, an acetone organic solution is used to strip off the copper oxide material deposited on the gallium oxide drift layer 3 without a photolithographic pattern, obtaining a P-type semiconductor layer 4 formed by copper oxide materials with four different doping concentrations, with the doping concentration gradually increasing from the center to the periphery.

[0084] Step 6: depositing a high-doping concentration p-type semiconductor layer 5 by magnetron sputtering.

[0085] 6.1) Using photolithography technology, a photoresist is used to form a pattern on the P-type semiconductor layer 4 with a gradient doping concentration;

[0086] 6.2) Magnetron sputtering was performed on the P-type semiconductor 4 with a doping concentration of 5×10 19 cm -3 and then using N-methylpyrrolidone solution to strip off the copper oxide material deposited on the P-type semiconductor 4 without the photolithographic pattern.

[0087] Step 7: Prepare anode metal 6.

[0088] 7.1) Using photolithography technology, prepare an anode pattern on the high-doping concentration p-type semiconductor layer 5 using photoresist;

[0089] 7.2) In an inert gas argon atmosphere, set the power to 150W, the evaporation time to 20 minutes, and the vacuum degree to 3×10 -6 TORR, with an ambient temperature of 25°C, a 45 nm thick Ni and a 200 nm thick Au were sequentially deposited on the anode pattern using electron beam evaporation.

[0090] 7.3) Use N-methylpyrrolidone solution to wash away the photoresist and strip off the metal on the surface where the anode pattern is not formed, completing the device fabrication.

[0091] Example 3: A gallium oxide pn diode is fabricated, comprising a p-type semiconductor layer composed of NiO materials with five different doping concentrations and having a doping concentration gradually varying from the center to the periphery.

[0092] Step A: Gallium oxide substrate cleaning:

[0093] A1) The thickness of the gallium oxide substrate is 300 μm, and the effective doping carrier concentration is 10 19 cm -3 , the doping ion type is Sn ion;

[0094] A2) The sample was sonicated in an ultrasonic bath using acetone, isopropanol, and deionized water in sequence for 5 minutes, and then blown dry using nitrogen gas.

[0095] Step B: Using the hydride vapor phase epitaxy (HVPE) method to grow a gallium oxide drift layer on the front side of the cleaned gallium oxide substrate:

[0096] B1) in a high temperature reaction zone of an HVPE vertical reactor, HCl is reacted with high purity metallic Ga at 850°C to produce GaCl and GaCl3;

[0097] B2) 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. GaCl and GaCl3 react with oxygen at 650°C on the gallium oxide substrate 2 to generate a 6 μm thick doped carrier concentration of 10 17 m -3 Gallium oxide drift layer 3.

[0098] Step C: Preparation of cathode ohmic metal.

[0099] In an inert gas argon atmosphere, the process conditions are set to 100 W, the sputtering time is 35 minutes, the pressure is 10 mtorr, and the ambient temperature is 25°C. A magnetron sputtering method is used to deposit Ti with a thickness of 20 nm and Au with a thickness of 350 nm on the back side of the gallium oxide substrate 2 to form a cathode ohm 1.

[0100] Step D: Annealing the cathode ohmic metal in a nitrogen atmosphere at 500° C. for 1 minute using an annealing furnace.

[0101] Step E: magnetron sputtering to deposit a P-type semiconductor layer 4 with a gradient doping concentration:

[0102] E1) A first photolithography is performed on the gallium oxide drift layer 3 using a photoresist to prepare a circular pattern. The circular pattern is subjected to magnetron sputtering for 60 minutes under the process conditions of a power of 150 W, an oxygen to argon ratio of 10%, a pressure of 10 mtorr, and an ambient temperature of 25°C to form a doping concentration of 1×10 17 cm -3 Then, an N-methylpyrrolidone solution is used to strip off the NiO material deposited on the gallium oxide drift layer 3 without the photolithographic pattern;

[0103] E2) A second photolithography process was performed on the gallium oxide drift layer 3 using photoresist to prepare a first circular ring pattern. The process conditions were set to 150 W, a ratio of oxygen to argon of 33%, a pressure of 10 mtorr, and an ambient temperature of 25°C. The first circular ring pattern was subjected to magnetron sputtering for 60 minutes to form a doping concentration of 1×10 18 cm -3 The first circle wraps the NiO ring of the central circular material; then the NiO material deposited on the gallium oxide drift layer 3 without the photolithographic pattern is stripped off using N-methylpyrrolidone solution;

[0104] E3) A third photolithography process was performed on the gallium oxide drift layer 3 using photoresist to form a second circular ring pattern. The process conditions were set to 150 W, 40% oxygen to argon ratio, 10 mtorr pressure, and 25° C. The second circular ring pattern was subjected to magnetron sputtering for 60 minutes to form a doping concentration of 5×10 18 cm -3 The second circle of NiO rings wraps around the first circle of ring material; then, an N-methylpyrrolidone solution is used to peel off the NiO material deposited on the gallium oxide drift layer 3 without the photolithographic pattern;

[0105] E4) A fourth photolithography process was performed on the gallium oxide drift layer 3 using photoresist to form a third circular ring pattern. The process conditions were set to 150 W, a ratio of oxygen to argon of 45%, a pressure of 10 mtorr, and an ambient temperature of 25°C. The third circular ring pattern was subjected to magnetron sputtering for 80 minutes to form a doping concentration of 8×10 18 cm -3 The third circle of NiO material wraps around the second circle of ring material; then the NiO material deposited on the gallium oxide drift layer 3 without the photolithographic pattern is removed by stripping with N-methylpyrrolidone solution;

[0106] E5) A fifth photolithography process was performed on the gallium oxide drift layer 3 using photoresist to form a fourth circular ring pattern. The process conditions were set to 150 W, 50% oxygen to argon ratio, 10 mtorr pressure, and 25° C. The fourth circular ring pattern was subjected to magnetron sputtering for 60 minutes to form a doping concentration of 1×10 19 cm -3 The fourth circle of NiO rings wraps around the third circle of ring material; then, an N-methylpyrrolidone solution is used to strip off the NiO material deposited on the gallium oxide drift layer 3 without a photolithographic pattern, thereby obtaining a P-type semiconductor layer 4 formed by NiO materials with five different doping concentrations, with the doping concentration gradually increasing from the center to the periphery.

[0107] Step F: Magnetron sputtering deposition of a high-doping concentration p-type semiconductor layer 5:

[0108] F1) using photolithography technology to prepare a pattern on the P-type semiconductor 4 with a gradient doping concentration using photoresist;

[0109] F2) Magnetron sputtering is used on the P-type semiconductor 4 with a gradient doping concentration according to the photolithographic pattern. The sputtering is carried out at a power of 100 W, an oxygen to argon ratio of 70%, a pressure of 10 mtorr, an ambient temperature of 25° C., and a processing time of 30 minutes to form a doping concentration of 1×10 20 cm -3 NiO materials;

[0110] F3) Using an acetone organic solution, the NiO material deposited on the areas without photolithographic patterns on the graded doping concentration P-type semiconductor layer 4 is stripped off to form a high doping concentration P-type semiconductor layer 5.

[0111] Step G: Preparation of anode metal:

[0112] G1) using photolithography technology to prepare an anode pattern on the high-doping concentration p-type semiconductor layer 5 using photoresist;

[0113] G2) In an inert gas argon atmosphere, set the power to 200 W, the time to 30 minutes, and the vacuum degree to 5×10 -6 TORR, process conditions at ambient temperature of 25°C, deposition of anode metal Ni / Au on the anode pattern by electron beam evaporation, and the thickness of the first layer of metal Ni is 45 nm and the thickness of the second layer of metal Au is 300 nm;

[0114] G3) device preparation is completed by washing off the photoresist with N-methyl pyrrolidone solution and peeling.

[0115] The above description is only three specific examples of the present application and does not constitute any limitation on the present application. Obviously, for those skilled in the art, after understanding the content and principles of the present application, various modifications and changes in form and details can be made without departing from the principles and structures of the present application. For example, the number of rings of the gradually-doped P-type semiconductor is not limited to the number of rings in the three examples of the present application, and more rings can be deposited; the gradually-doped P-type semiconductor is not only in the form of a circular ring, but also in the form of a square ring; the preparation method of the p-type semiconductor is not limited to magnetron sputtering, but any one of the metal organic compound chemical vapor deposition processes; the preparation method of the anode metal is not limited to electron beam evaporation, but any one of magnetron sputtering or thermal evaporation; the preparation method of the cathode ohmic metal is not limited to magnetron sputtering, but any one of electron beam evaporation or thermal evaporation. However, these modifications and changes based on the idea of the present application are still within the scope of protection of the claims of the present application.

Claims

1. A gallium oxide pn diode with a P-type doping concentration gradually changing from the center to the periphery, comprising: A cathode ohmic metal (1), a gallium oxide substrate (2), a gallium oxide drift layer (3), a P-type semiconductor layer (4), a high-doping concentration P-type semiconductor layer (5) and an anode metal (6); characterized in that the P-type semiconductor layer (4) is a gradient doped P-type semiconductor layer formed by gradually depositing multiple circles of semiconductor materials with different doping concentrations from the center to the periphery in the order of their doping concentration from low to high, so as to increase the reverse breakdown voltage of the device while reducing the on-resistance of the device, thereby improving the Baliga figure of merit of the gallium oxide device.

2. The diode according to claim 1, characterized in that The thickness of the graded doped P-type semiconductor layer is 5-30 nm, and the graded doping concentration ranges from 1×10 16 cm -3 Gradient to 1×10 19 cm -3 .

3. The diode according to claim 1, wherein: The cathode ohmic metal (1) is made of Ti / Au metal, and the thickness of the first layer of Ti close to the gallium oxide substrate layer is 20-50 nm, and the thickness of the second layer of Au metal is 100-400 nm; The gallium oxide substrate (2) has a thickness of 300-650 μm and an effective doping carrier concentration of 10 18 -10 20 cm -3 , the doping ion species is Si ion or Sn ion; The gallium oxide drift layer (3) has a thickness of 3-15 μm and a doping carrier concentration of 10 16 -10 18 cm -3 .

4. The diode according to claim 1, characterized in that The optional p-type semiconductor materials in the gradient doped P-type semiconductor layer (4) and the high doping concentration P-type semiconductor layer (5) both include nickel oxide, copper oxide, and tin oxide. The high doping concentration P-type semiconductor layer (5) has a thickness of 3-20 nm and a doping carrier concentration of 10 19 -10 20 cm -3 .

5. The diode according to claim 1, characterized in that The anode metal (6) is Ni / Au metal, and the thickness of the first layer of metal Ni is 45-60nm, and the thickness of the second layer of metal Au is 200-400nm.

6. A method for manufacturing a gallium oxide pn diode with a gradually changing P-type doping concentration from the center to the periphery, characterized in that: The following steps are involved: 1) cleaning the gallium oxide substrate (2) in sequence with acetone, isopropanol, and deionized water; 2) using hydride vapor phase epitaxy (HVPE) to epitaxially form a gallium oxide drift layer (3) on the front side of the cleaned gallium oxide substrate (2), depositing an ohmic cathode metal (1) on the back side by magnetron sputtering in an argon atmosphere, and performing ohmic annealing on the ohmic cathode metal (1); 3) depositing a P-type semiconductor layer (4) with a gradient doping concentration on the gallium oxide drift layer (3): 3a) performing a photolithography operation on the front surface of the gallium oxide drift layer (3) to form a circular pattern; 3b) setting the magnetron sputtering process conditions to 100-150 W power, 5%-50% oxygen to argon ratio, 10-90 minutes processing time, 4-10 mtorr pressure, and 25° C. ambient temperature; 3c) forming a circular P-type material with a lower doping concentration by magnetron sputtering according to the circular pattern of the first photolithography, and stripping off the P-type material deposited on the part of the gallium oxide drift layer (3) without the photolithography pattern; 3d) performing secondary photolithography on the front surface of the gallium oxide drift layer (3) to form a circular ring pattern, increasing the ratio of oxygen to argon in the magnetron sputtering process, and depositing a circular ring of p-type material that wraps around the circular p-type material deposited previously using magnetron sputtering according to the circular ring pattern of the secondary photolithography, wherein the p-type doping concentration is higher than that of the previously deposited circular p-type material, and then stripping off the p-type material deposited on the gallium oxide drift layer (3) where there is no photolithography pattern; 3e) performing n photolithography steps on the front of the gallium oxide drift layer (3) to form a circular pattern, increasing the ratio of oxygen to argon in the magnetron sputtering process, and depositing a circular ring of p-type material that wraps around the circular ring of the previous n-1 deposits using magnetron sputtering according to the circular pattern of the n photolithography steps, wherein the p-type doping concentration is higher than that of the previous n-1 deposits, and then stripping off the p-type material deposited on the gallium oxide drift layer (3) without the photolithography pattern; repeating this step until the total width of the p-type material deposited according to the photolithography pattern is equal to the width of the anode metal (6), thereby forming a p-type semiconductor layer (4) with a doping concentration from low to high from the center to the periphery, wherein n is an integer greater than 2; 4) depositing a high-doping-concentration P-type semiconductor layer (5) on the front surface of the P-type semiconductor layer (4) with doping concentrations increasing from low to high from the center to the periphery: 4a) forming a pattern on the front surface of the P-type semiconductor layer (4) using a photolithography process; 4b) Setting magnetron sputtering process conditions: power of 100-150 W, oxygen to argon ratio of 50%-80%, processing time of 10-90 minutes, pressure of 4-10 mtorr, and ambient temperature of 25° C.; 4c) depositing a high-doping concentration P-type semiconductor layer (5) on the P-type semiconductor layer (4) by magnetron sputtering according to the process conditions set in 4b) according to the photolithography pattern; 5) An anode pattern is formed on the front surface of the high-doping concentration P-type semiconductor layer (5) using a photolithography process, and an anode metal (6) is deposited using electron beam evaporation according to the anode pattern to complete device manufacturing.

7. The method according to claim 6, characterized in that In the step 2), a lightly doped gallium oxide is grown on the front of the cleaned gallium oxide substrate (2) using a hydride vapor phase epitaxy (HVPE) method to form a gallium oxide drift layer (3), which is achieved as follows: Under an ammonia atmosphere, in the high-temperature reaction zone of the HVPE vertical reactor, HCl reacts with high-purity metallic Ga at 800-900°C to produce GaCl and GaCl3; The GaCl and GaCl3 generated in the high temperature reaction zone are pushed into the low temperature reaction zone, and the cleaned gallium oxide substrate (2) is placed face up in the low temperature reaction zone of the HVPE vertical reactor, and GaCl and GaCl3 react with oxygen at a temperature of 500-650°C on the gallium oxide substrate 2. The carrier concentration of the generated gallium oxide is controlled to be 10 by changing the volume ratio of GaCl and GaCl3 to oxygen. 16 -10 18 cm -3 , epitaxially forming a lightly doped gallium oxide drift layer (3).

8. The method according to claim 6, characterized in that In the step 2), the ohmic cathode metal (1) is deposited on the back side of the gallium oxide substrate (2) by magnetron sputtering. The gallium oxide substrate (2) is placed with its back side facing upward in a magnetron sputtering instrument. Under the process conditions of an inert gas argon atmosphere, a power of 100-300 W, a sputtering time of 30-90 minutes, a pressure of 6-12 mtorr, and an ambient temperature of 25° C., the ohmic cathode metal (1) is deposited on the back side of the gallium oxide substrate (2).

9. The method according to claim 6, characterized in that: The annealing of the ohmic cathode metal (1) in step 2) is carried out in a nitrogen atmosphere, with an annealing temperature of 400-500° C. and an annealing time of 1-3 minutes.

10. The method according to claim 6, characterized in that: The electron beam evaporation deposition of the anode metal (6) in step 5) is achieved as follows: The high-doping concentration P-type semiconductor layer (5) is placed face up in an electron beam evaporation instrument in an inert gas argon atmosphere with a power of 150-350W, an evaporation time of 40-100 minutes, and a vacuum degree of 10 -6 -10 -7 In a TORR process, under the process condition of an ambient temperature of 25° C., an anode metal (6) is deposited on the front surface of a high-doping concentration P-type semiconductor layer (5) by electron beam evaporation.

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