CN115020500A - Gallium oxide Schottky diode capable of reducing on-resistance and preparation method thereof - Google Patents
Gallium oxide Schottky diode capable of reducing on-resistance and preparation method thereof Download PDFInfo
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/861—Diodes
- H01L29/872—Schottky diodes
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- H01L21/02019—Chemical etching
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Abstract
The invention discloses a gallium oxide Schottky diode capable of reducing on-resistance and a preparation method thereof, and mainly solves the problems that a low-damage gallium oxide substrate material cannot be prepared and the on-resistance of a device cannot be effectively reduced in the prior art. It from bottom to top includes: the gallium oxide epitaxial layer comprises cathode metal (1), a gallium oxide substrate (2), a lightly doped epitaxial layer (3) and anode metal (4), wherein the gallium oxide substrate (2) uses 49% concentration of hydrofluoric acid and 75% -90% concentration of high potassium sulfate, and the ratio of the concentration of hydrofluoric acid to the concentration of potassium sulfate is 1: 1, carrying out wet etching thinning on the etching solution prepared according to the proportion; the cathode metal (1) adopts a zigzag ohmic contact pattern structure. According to the invention, the original 650 mu m gallium oxide substrate material is thinned to 200-400 mu m, and the thinned substrate is used for preparing the zigzag ohmic contact pattern structure, so that the on-resistance is reduced, the device performance is improved, and the substrate can be used for electronic systems of communication, power electronics, signal processing and aerospace.
Description
Technical Field
The invention belongs to the technical field of semiconductor devices, and particularly relates to a gallium oxide Schottky diode which can be used for electronic systems of communication, power electronics, signal processing and aerospace.
Technical Field
Gallium oxide, as a new ultra-wide bandgap semiconductor material, has a large bandgap, and a high theoretical breakdown electric field is becoming an interesting research hotspot. With the research progress of material growth and the growing improvement of epitaxial technology, the scale production of gallium oxide materials is in a first-generation prototype and has great development potential. The larger forbidden band width leads to lower power loss and higher conversion efficiency in the application of power electronic devices. Among them, the gan schottky diode has become one of the focus and hot spot of research on gan power electronic devices in recent years due to its faster switching speed and lower off-state loss.
The on-resistance of the gallium oxide power device is an important parameter for measuring the performance of the device, and the main method for reducing the on-resistance of the device by reducing the resistance of the substrate is to thin the gallium oxide substrate. The mainstream substrate thinning technology at present is a chemical mechanical polishing technology, silicon gel is used as a polishing agent and applied to the surface of a semiconductor crystal, and the gallium oxide substrate thinning is realized through the combined action of chemical reaction and mechanical grinding. However, there are many problems with chemical mechanical polishing techniques: 1) the technology needs to generate a stress action on the surface of the gallium oxide material, and the gallium oxide material has lower hardness and cannot bear excessive stress, so that the thinning thickness of the technology is smaller; 2) the roughness of the surface of the gallium oxide substrate becomes larger after the gallium oxide substrate is thinned by the method, and the surface defects are increased. Therefore, how to carry out deep thinning on 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.
Gao Xiang et al published "chemical mechanical polishing of gallium oxide substrate" in mechanical design and manufacture, which employs chemical mechanical polishing to thin the gallium oxide substrate, to reduce the substrate resistance and the device on-resistance.
Lee, Y et al published "Thermal Atomic Layer Etching of Galium Oxide Using Sequential Expo sures of HF and variaous Metal Precondensers" at CHEMISTRY OF MATERIALS, which used hydrofluoric acid to soak Gallium Oxide to achieve the purpose of Etching Gallium Oxide material.
Although the method 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 overlarge, so that the performance of a device is seriously influenced.
Disclosure of Invention
The invention aims to provide a gallium oxide Schottky diode capable of reducing on-resistance and a preparation method thereof aiming at overcoming the defects of the prior art, so that the damage to the surface of the gallium oxide substrate is reduced by using a mixed solution of hydrofluoric acid and high potassium sulfate for wet etching and thinning, the on-resistance is reduced by preparing graphical ohmic contact, and the performance of a device is improved.
In order to achieve the purpose, the technical scheme of the invention is as follows:
1. a gallium oxide Schottky diode for reducing on-resistance comprises, 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-shaped ohmic contact pattern structure to reduce the on-resistance and improve the performance of the device.
Furthermore, the cathode metal is Ti/Au, the thickness of the first layer of Ti close to the gallium oxide substrate is 20-50 nm, and the thickness of the second layer of Au metal is 100-400 nm.
Further, the thickness of the gallium oxide substrate is 300-650 mu m, and the concentration of effective doping carriers is 10 18 ～10 19 cm -3 The doping ion species is Si ions or Sn ions.
Furthermore, the thickness of the gallium oxide lightly doped epitaxial layer is 3 to15 μm, a doping carrier concentration of 10 16 ～10 18 cm -3 。
Further, the anode metal of the Schottky diode is Ni/Au metal, 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.
Further, the annealing of the ohmic cathode metal is carried out in a nitrogen atmosphere, the annealing temperature is 400-500 ℃, and the annealing time is 1-3 minutes.
2. A manufacturing method of a low-on-resistance gallium oxide Schottky diode is characterized by comprising the following steps:
1) sequentially cleaning the gallium oxide substrate 2 by acetone-isopropanol-deionized water;
2) thinning the gallium oxide substrate 2 by wet etching:
2a) spin-coating a layer of photoresist on the upper surface of the gallium oxide substrate 2 by using a spin coater to serve as a protective mask;
2b) hydrofluoric acid with a concentration of 49% and high potassium sulfate with a concentration of 75% -90% are used, and the reaction is carried out in a ratio of 1: 1, soaking the gallium oxide substrate 2 with a protective mask in the corrosive solution for 8-15 hours to corrode the gallium oxide substrate, and thinning the substrate with the thickness of 650 microns to 200-400 microns;
3) preparing a zigzag ohmic contact pattern on the back of the thinned gallium oxide substrate 2:
3a) forming an ohmic photoetching pattern on the back surface of the gallium oxide substrate 2 by using a photoresist by adopting a photoetching technology;
3b) setting the power to be 100W, under the argon atmosphere, processing time to be 80 minutes, pressure intensity to be 10mtorr and environment temperature to be 25 ℃ magnetron sputtering process conditions, and depositing metal platinum with the thickness of 15nm on a gallium oxide substrate 2 ohm photoetching pattern;
3c) spin-coating a layer of photoresist on the upper surface of the gallium oxide substrate 2 by using a spin coater to serve as a protective mask;
3d) hydrofluoric acid at a concentration of 49% and potassium permanganate at a concentration of 75% were used, in a ratio of 1: 1, soaking the gallium oxide substrate 2 with a protective mask in the corrosive solution, and forming a zigzag ohmic contact pattern on the lower surface of the gallium oxide substrate 2 through a metal platinum catalytic reaction for 5 hours under the irradiation of ultraviolet light;
3e) sequentially cleaning the gallium oxide substrate 2 with the serrated ohmic contact pattern by acetone-isopropanol-deionized water;
4) performing epitaxial light-doped gallium oxide epitaxial layer 3 on the front surface of the cleaned gallium oxide substrate 2 by using a hydride vapor phase epitaxy technology HVPE method, depositing ohmic cathode metal 1 on the back surface of the gallium oxide substrate by using magnetron sputtering to form a zigzag ohmic contact structure, and performing ohmic annealing on the cathode metal 1;
5) and forming an anode pattern on the front surface of the gallium oxide lightly doped epitaxial layer 3 by adopting a photoetching process, depositing anode metal 4 by adopting electron beam evaporation according to the anode pattern, and stripping metal materials outside the anode photoetching pattern to finish the manufacture of the device.
Compared with the prior art, the invention has the following advantages:
firstly, the invention adopts 49% hydrofluoric acid and 75% -90% high potassium sulfate, and the ratio of 1: 1, compared with the traditional chemical mechanical polishing technology, the deep thinning of the gallium oxide substrate can be realized because the solution corrosion does not produce stress action on the surface of the gallium oxide substrate, and meanwhile, because the solution soaking corrosion does not have the mechanical grinding action, the substrate surface cannot be damaged, and the thinned substrate surface has good quality and small damage.
Secondly, the invention adopts cathode ohmic metal with a sawtooth-shaped ohmic contact pattern structure, thereby reducing the on-resistance and improving the performance of the device.
Drawings
Fig. 1 is a schematic structural diagram of a conventional gan schottky diode.
Fig. 2 is a schematic structural diagram of a low on-resistance gan schottky diode according to the present invention.
Fig. 3 is a flow chart of an implementation of the present invention to fabricate the gan schottky diode of fig. 2.
Detailed Description
In order to more clearly illustrate the technical solution of the present invention, the present invention is further described below with reference to the accompanying drawings and examples. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details.
Referring to fig. 2, the gallium oxide schottky diode prepared by the present invention includes: the Schottky diode comprises a cathode metal 1, a gallium oxide substrate 2, a gallium oxide lightly-doped epitaxial layer 3 and an anode metal 4. Wherein:
the cathode metal 1 is positioned on the back of the gallium oxide substrate 2 and adopts a zigzag ohmic contact pattern, the metal adopts Ti/Au, the thickness of Ti is 20-50 nm, and the thickness of Au is 100-400 nm;
the gallium oxide substrate 2 has a thickness of 200-400 μm and a doping concentration of 10 18 ～10 19 cm -3 ；
The gallium oxide lightly doped epitaxial layer 3 is positioned on the gallium oxide substrate 2, the thickness of the gallium oxide lightly doped epitaxial layer is 3-15 mu m, and the doping concentration is 10 16 ～10 18 cm -3 ；
The anode metal 4 is positioned on the gallium oxide lightly doped epitaxial layer 3, the metal is Ni/Au, the thickness of Ni is 45-60 nm, and the thickness of Au is 200-400 nm.
Referring to fig. 3, the present invention provides the following three embodiments for fabricating the device structure of fig. 2:
the first embodiment is as follows: and manufacturing the gallium oxide Schottky diode with the substrate thickness of 200 mu m and the sawtooth-shaped ohmic contact pattern structure.
The method comprises the following steps: and cleaning the gallium oxide substrate material.
The thickness is 650 mu m, and the effective doping carrier concentration is 2 multiplied by 10 18 cm -3 The gallium oxide substrate 2 doped with Sn ions was ultrasonically cleaned with acetone-isopropyl alcohol-deionized water at an ultrasonic intensity of 2.0 for 3 minutes, and then dried with nitrogen.
Step two: and thinning the cleaned gallium oxide substrate by adopting a wet etching technology.
2.1) spin-coating a layer of photoresist on the upper surface of the gallium oxide substrate by using a spin coater as a protective mask, wherein the spin-coating conditions are as follows: the rotating speed of a spin coater is 2000rpm, spin coating is carried out for 22s, and after spin coating is finished, hot plate baking at 110 ℃ is carried out for 3 minutes to realize isolation protection of the gallium oxide substrate.
2.2) etching and thinning of the gallium oxide substrate:
2.2.1) using 49% strength hydrofluoric acid and 90% strength potassium permanganate, in a ratio of 1: 1 to prepare a corrosive solution;
2.2.2) putting the gallium oxide substrate with isolation protection into the solution for soaking and corroding, and thinning the original gallium oxide substrate with the thickness of 650 mu m to 200 mu m when the soaking time is 15 hours;
2.2.3) are respectively ultrasonically cleaned for 3 minutes by using acetone-isopropanol-deionized water under the condition of ultrasonic intensity of 2.0, and then are dried by using nitrogen.
Step three: and preparing a zigzag ohmic contact pattern on the back of the thinned gallium oxide substrate.
3.1) ohmic patterning lithography:
3.1.1) preparing an ohmic photoetching pattern on the surface of the gallium oxide substrate by adopting a photoetching technology and using a photoresist;
3.1.2) depositing metal platinum with the thickness of 15nm on the ohmic photoetching pattern of the gallium oxide substrate by adopting a magnetron sputtering method;
3.1.3) carrying out ultrasonic cleaning for 3 minutes by using an acetone solution under the condition of ultrasonic intensity of 2.0; boiling the deposition medium stripping solution at 60 ℃ for 15 minutes; sequentially using acetone-isopropanol-deionized water to perform ultrasonic cleaning for 3 minutes under the condition of ultrasonic intensity of 2.0, and then using nitrogen to blow dry to remove the metal platinum outside the photoetching pattern area;
3.2) isolation protection of the gallium oxide substrate.
Spin-coating a layer of photoresist on the upper surface of the gallium oxide substrate (2) by using a spin coater as a protective mask, wherein the spin-coating conditions are as follows: spin coating at 2000rpm for 22s, and baking at 110 deg.C for 3 min.
3.3) Using 49% strength hydrofluoric acid and 75% strength potassium permanganate in a 1: 1, preparing an etching solution;
3.4) putting the gallium oxide material which is subjected to substrate isolation protection into the solution prepared in 3.3) for corrosion, irradiating the corrosion solution by using ultraviolet light in the soaking process, and forming a zigzag ohmic contact pattern on the lower surface of the gallium oxide substrate through a metal platinum catalytic reaction for 5 hours;
3.5) carrying out ultrasonic cleaning on the substrate subjected to the solution corrosion respectively by using acetone-isopropanol-deionized water under the condition of ultrasonic intensity of 2.0 for 3 minutes, and then carrying out blow drying by using nitrogen.
Step four: and preparing a gallium oxide lightly doped epitaxial layer on the front side of the cleaned gallium oxide substrate by adopting a Hydride Vapor Phase Epitaxy (HVPE) method.
4.1) reacting HCl with highly pure metallic Ga at a temperature of 800 ℃ in a high-temperature reaction zone of an HVPE vertical reactor to form GaCl and GaCl 3 ；
4.2) reacting GaCl and GaCl formed in the high-temperature reaction zone 3 Pushing into low temperature reaction zone, placing gallium oxide substrate 2 with its front side facing upwards in low temperature reaction zone of HVPE vertical reactor, and making GaCl and GaCl on the gallium oxide substrate 3 Reacting with oxygen at 600 deg.C to obtain a film with a thickness of 10 μm and a doping concentration of 2 × 10 16 cm -3 Lightly doping the epitaxial layer 3 with gallium oxide.
Step five: and preparing cathode ohmic metal.
And depositing metal Ti/Au on the back of the gallium oxide substrate 2 by adopting a magnetron sputtering method, wherein the thickness of the first layer of Ti close to the gallium oxide substrate layer is 20nm, and the thickness of the second layer of Au metal is 400nm, so as to form the cathode metal 1 with zigzag patterned ohm.
And annealing the cathode metal in a nitrogen atmosphere by using an annealing furnace, wherein the annealing temperature is 470 ℃, and the annealing time is 1 minute.
Step six: an anode schottky metal 4 is prepared.
6.1) preparing an anode pattern on the surface of the gallium oxide lightly doped epitaxial layer 3 by utilizing a photoetching technology and using photoresist;
6.2) depositing metal Ni/Au on the anode pattern by adopting an electron beam evaporation method, wherein the thickness of the first layer of metal Ni is 45nm, and the thickness of the second layer of metal Au is 400 nm;
and 6.3) washing off the photoresist by adopting an N-methyl pyrrolidone solution, namely removing the metal material deposited on the gallium oxide lightly doped epitaxial layer 3 without the photoetching pattern, and finishing the manufacture of the device.
Example two: and manufacturing the gallium oxide Schottky diode with the thickness of the gallium oxide substrate being 300 mu m and a sawtooth-shaped ohmic contact pattern structure.
Step 1: and cleaning the gallium oxide material.
The thickness of the gallium oxide substrate 2 is 650 μm, and the effective doping carrier concentration is 2 × 10 19 cm -3 And the doping ion species is Sn ions, acetone-isopropanol-deionized water is respectively used for ultrasonic cleaning for 3 minutes under the condition of ultrasonic intensity of 2.0, and then nitrogen is used for blow drying.
Step 2: and thinning the cleaned gallium oxide substrate by adopting a wet etching technology.
2a1) And (3) setting the spin-coating time to be 22s at 2000rpm by using a spin coater, spin-coating a layer of photoresist on the upper surface of the gallium oxide substrate to be used as a protective mask, and baking the gallium oxide substrate for 3 minutes by using a hot plate at 110 ℃ after the spin coating is finished to realize the isolation protection of the gallium oxide substrate.
2a2) Etching and thinning the gallium oxide substrate:
2a2.1) using 49% strength hydrofluoric acid and 90% strength potassium permanganate in a ratio of 1: 1 to prepare a corrosive solution;
2a2.2) putting the gallium oxide substrate with isolation protection into a solution for soaking and corrosion, and thinning the original gallium oxide substrate with the thickness of 650 mu m to 300 mu m when the soaking time is 12 hours;
2a2.3) are respectively ultrasonically cleaned for 3 minutes by using acetone-isopropanol-deionized water under the condition of ultrasonic intensity of 2.0, and then are dried by using nitrogen.
And 3, step 3: and preparing a zigzag ohmic contact pattern on the back of the thinned gallium oxide substrate.
3a1) Ohmic patterning photoetching:
3a1.1) preparing an ohmic photoetching pattern on the back of the gallium oxide substrate by using a photoresist by adopting a photoetching technology;
3a1.2) depositing metal platinum on the surface of the gallium oxide substrate by adopting a magnetron sputtering method to form an anti-corrosion mask;
3a1.3) ultrasonically cleaning for 3 minutes by using an acetone solution under the condition of ultrasonic intensity of 2.0; boiling the deposition medium stripping solution at 60 ℃ for 15 minutes; and sequentially carrying out ultrasonic cleaning for 3 minutes by using acetone-isopropanol-deionized water under the condition of ultrasonic intensity of 2.0, and then carrying out blow-drying by using nitrogen to remove the metal platinum outside the photoetching pattern area.
3a2) Setting the spin coating time to be 22s at 2000rpm by using a spin coater, spin-coating a layer of photoresist on the upper surface of the gallium oxide substrate to be used as a protective mask, and baking the gallium oxide substrate for 3 minutes by using a hot plate at 110 ℃ after spin coating is finished to realize the isolation protection of the gallium oxide substrate;
3a3) hydrofluoric acid at a concentration of 49% and potassium permanganate at a concentration of 75% were used in a 1: 1, preparing an etching solution;
3a4) putting the gallium oxide material with substrate isolation protection into a solution for soaking corrosion, irradiating the corrosion solution by using ultraviolet light in the soaking process, and forming a zigzag ohmic contact pattern on the lower surface of the gallium oxide substrate through a platinum catalytic reaction for 5 hours;
3a5) and ultrasonically cleaning the substrate corroded by the solution for 3 minutes by using acetone, isopropanol and deionized water respectively under the condition of ultrasonic intensity of 2.0, and then drying by using nitrogen.
And 4, step 4: and preparing a gallium oxide lightly doped epitaxial layer on the front side of the cleaned gallium oxide substrate by adopting a Hydride Vapor Phase Epitaxy (HVPE) method.
4a) Reacting HCl with high purity metal Ga at 850 ℃ in a high temperature reaction zone of an HVPE vertical reactor to produce GaCl and GaCl 3 ；
4b) Reacting GaCl and GaCl generated in the high-temperature reaction zone 3 Pushing into low temperature reaction zone, placing gallium oxide substrate 2 with right side up in HVPE vertical reactor low temperature reaction zone to make GaCl and GaCl 3 Reacting with oxygen at 650 deg.C to form a gallium oxide substrate with a thickness of 8 μm and a doping concentration of 2 × 10 17 cm -3 Of gallium oxide epitaxial layer 3.
And 5: and preparing cathode ohmic metal.
And depositing metal Ti/Au on the back of the gallium oxide substrate 2 by adopting a magnetron sputtering method, wherein the thickness of a first layer of Ti close to the gallium oxide substrate layer is 45nm, and the thickness of a second layer of Au metal is 400nm, so as to form the cathode metal 1 with zigzag patterned ohm.
And annealing the cathode metal in a nitrogen atmosphere by using an annealing furnace, wherein the annealing temperature is 470 ℃, and the annealing time is 2 minutes.
Step 6: an anode schottky metal is prepared.
6a1) Preparing an anode pattern on the surface of the gallium oxide lightly doped epitaxial layer 3 by using a photoresist by utilizing a photoetching technology;
6a2) depositing metal Ni/Au on the anode pattern by adopting an electron beam evaporation method, wherein the thickness of the first layer of metal Ni is 45nm, and the thickness of the second layer of metal Au is 400 nm;
6a3) and (3) washing off the photoresist by adopting an N-methyl pyrrolidone solution, namely removing the metal material deposited on the gallium oxide lightly doped epitaxial layer 3 without the photoetching pattern, and finishing the manufacture of the device.
Example three: and manufacturing the gallium oxide Schottky diode with the thickness of the gallium oxide substrate being 400 mu m and the sawtooth-shaped ohmic contact pattern structure.
Step A: and cleaning the gallium oxide material.
The thickness of the gallium oxide substrate 2 is 650 μm, and the effective doping carrier concentration is 1 × 10 19 cm -3 And the doping ion species is Sn ions, acetone-isopropanol-deionized water is respectively used for ultrasonic cleaning for 3 minutes under the condition of ultrasonic intensity of 2.0, and then nitrogen is used for blow drying.
And B: and thinning the cleaned gallium oxide substrate by adopting a wet etching technology.
B1) Setting the process conditions of 2000rpm of the spin coater speed and 22s of spin coating time, spin coating a layer of photoresist on the upper surface of the gallium oxide substrate by using the spin coater as a protective mask, and baking the gallium oxide substrate for 3 minutes by a hot plate at 110 ℃ after spin coating is finished to realize the isolation protection of the gallium oxide substrate;
B2) etching and thinning the gallium oxide substrate:
b2.1) using 49% strength hydrofluoric acid and 75% strength potassium permanganate, mixed in a ratio of 1: 1 to prepare a corrosive solution;
b2.2) putting the gallium oxide substrate with isolation protection into the solution for soaking and corroding for 8 hours, and thinning the original gallium oxide substrate with the thickness of 650 microns to 400 microns;
b2.3) carrying out ultrasonic cleaning on the thinned gallium oxide substrate for 3 minutes by using acetone-isopropanol-deionized water respectively under the condition of ultrasonic intensity of 2.0, and then carrying out blow-drying by using nitrogen.
And C: and preparing a zigzag ohmic contact pattern on the back of the thinned gallium oxide substrate.
C1) And (5) ohmic patterned photoetching.
C1.1) preparing an ohmic photoetching pattern on the back of the gallium oxide substrate by using a photoresist by adopting a photoetching technology;
c1.2) depositing metal platinum on the surface of the gallium oxide substrate by adopting a magnetron sputtering method to form an anti-corrosion mask;
c1.3) carrying out ultrasonic cleaning for 3 minutes by using an acetone solution under the condition of ultrasonic intensity of 2.0; boiling the deposition medium stripping solution at 60 ℃ for 15 minutes; and sequentially carrying out ultrasonic cleaning for 3 minutes by using acetone-isopropanol-deionized water under the condition of ultrasonic intensity of 2.0, and then carrying out blow-drying by using nitrogen to remove the metal platinum outside the photoetching pattern area.
C2) Spin-coating 22s on the upper surface of the gallium oxide substrate (2) by using a spin coater with the rotating speed of 2000rpm to form a photoresist protective mask, and baking for 3 minutes at a hot plate temperature of 110 ℃ after spin coating is finished.
C3) Hydrofluoric acid at a concentration of 49% and potassium permanganate at a concentration of 75% were used in a 1: 1, preparing an etching solution;
C4) putting a gallium oxide material for substrate isolation protection into a solution for corrosion, irradiating the corrosion solution by using ultraviolet light in the soaking process, carrying out catalytic reaction for 5 hours by using metal platinum to form a zigzag ohmic contact pattern on the lower surface of the gallium oxide substrate, carrying out ultrasonic cleaning for 3 minutes by using acetone-isopropanol-deionized water under the condition of ultrasonic intensity of 2.0, and then carrying out blow-drying by using nitrogen.
Step D: and preparing a gallium oxide lightly doped epitaxial layer on the front side of the cleaned gallium oxide substrate by adopting a Hydride Vapor Phase Epitaxy (HVPE) technology.
D1) In a high-temperature reaction zone of an HVPE vertical reactor, HCl reacts with high-purity metal Ga at the temperature of 900 ℃ to generate GaCl and GaCl 3 ；
D2) Reacting GaCl and GaCl generated in the high-temperature reaction zone 3 Pushing into low temperature reaction zone, placing gallium oxide substrate 2 with right side up in HVPE vertical reactor low temperature reaction zone to make GaCl and GaCl 3 Reacting with oxygen at 500 deg.C to form a gallium oxide substrate with a thickness of 9 μm and a doping concentration of 1 × 10 16 cm -3 Of gallium oxide epitaxial layer 3.
Step E: and preparing cathode ohmic metal.
And depositing metal Ti/Au with the total thickness of 390nm on the back surface of the gallium oxide substrate 2 by adopting a magnetron sputtering method, wherein the thickness of a first layer of Ti close to the gallium oxide substrate layer is 40nm, and the thickness of a second layer of Au metal is 350nm, and forming the cathode metal 1 with zigzag patterned ohm.
Step F: and (3) annealing the cathode metal by using an annealing furnace under the nitrogen atmosphere and under the process conditions that the annealing temperature is 500 ℃ and the annealing time is 1 minute.
Step G: an anode schottky metal is prepared.
By utilizing a photoetching technology, an anode pattern is firstly prepared on the surface of the gallium oxide epitaxial layer 3 by using photoresist; sequentially depositing Ni metal with the thickness of 45nm and Au with the thickness of 400nm on the anode pattern by adopting an electron beam evaporation method to form anode metal; and finally, washing off the photoresist by adopting an N-methyl pyrrolidone solution, namely removing the metal material deposited on the gallium oxide epitaxial layer 3 at the position without the photoetching pattern, and finishing the manufacture of the device.
The foregoing description is only three specific examples of the present invention and is not intended to limit the present invention in any way, and it will be apparent to those skilled in the art that various modifications and variations in form and detail can be made without departing from the principles and structure of the present invention, for example, the gallium oxide substrate thinned thickness can be precisely controlled according to the ratio of hydrofluoric acid to high potassium sulfate solution and the soaking time; the preparation method of the anode metal and the cathode metal is not limited to electron beam evaporation, and any one of methods such as magnetron sputtering, thermal evaporation and the like can be used; such modifications and variations that are based on the inventive idea are intended to be within the scope of the appended claims.
Claims (9)
1. A gallium oxide Schottky diode for reducing on-resistance comprises, from bottom to top: the device comprises cathode metal (1), a gallium oxide substrate (2), a gallium oxide lightly-doped epitaxial layer (3) and anode metal (4), and is characterized in that the cathode metal (1) adopts a sawtooth-shaped ohmic contact pattern structure to reduce the on-resistance and improve the performance of the device.
2. The diode of claim 1, wherein the cathode metal (1) is Ti/Au, and the first layer of Ti near the gallium oxide substrate (2) has a thickness of 20 to 50nm and the second layer of Au metal has a thickness of 100 to 400 nm.
3. The diode of claim 1, wherein the gallium oxide substrate (2) has a thickness of 200 to 400 μm and an effective doping carrier concentration of 10 18 ～10 19 cm -3 The doping ion species is Si ions or Sn ions.
4. The diode according to claim 1, wherein the lightly doped epitaxial layer (3) has a thickness of 3-15 μm and a doping carrier concentration of 10 16 ～10 18 cm -3 。
5. The diode of claim 1, wherein the anode metal (4) is Ni/Au metal, and the first layer of Ni metal has a thickness of 45 to 60nm and the second layer of Au metal has a thickness of 200 to 400 nm.
6. A manufacturing method of a gallium oxide Schottky diode capable of reducing on-resistance is characterized by comprising the following steps:
1) sequentially cleaning the gallium oxide substrate (2) by acetone-isopropanol-deionized water;
2) thinning the gallium oxide substrate (2) by wet etching:
2a) spin-coating a layer of photoresist on the upper surface of the gallium oxide substrate (2) by using a spin coater to serve as a protective mask;
2b) hydrofluoric acid with a concentration of 49% and high potassium sulfate with a concentration of 75% -90% are used, and the reaction is carried out in a ratio of 1: 1, soaking the gallium oxide substrate (2) with the protective mask in the corrosive solution for 8-15 hours to corrode the gallium oxide substrate, and thinning the 650 mu m substrate to 200-400 mu m;
3) preparing a zigzag ohmic contact pattern on the back of the thinned gallium oxide substrate (2):
3a) forming an ohmic photoetching pattern on the back surface of the gallium oxide substrate (2) by using photoresist by adopting a photoetching technology;
3b) setting the power to be 100W, under the argon atmosphere, processing time to be 80 minutes, pressure intensity to be 10mtorr and environment temperature to be 25 ℃ under the magnetron sputtering process condition, and depositing metal platinum with the thickness of 15nm on the ohm photoetching graph of the gallium oxide substrate (2);
3c) spin-coating a layer of photoresist on the upper surface of the gallium oxide substrate (2) by using a photoresist spinner to serve as a protective mask;
3d) hydrofluoric acid at a concentration of 49% and potassium permanganate at a concentration of 75% were used, in a ratio of 1: 1, soaking the gallium oxide substrate (2) with a protective mask in the corrosive solution, and forming a zigzag ohmic contact pattern on the lower surface of the gallium oxide substrate (2) through a metal platinum catalytic reaction for 5 hours under the irradiation of ultraviolet light;
3e) sequentially cleaning the gallium oxide substrate (2) with the serrated ohmic contact pattern by acetone-isopropanol-deionized water;
4) performing epitaxy light-doped gallium oxide epitaxial layer (3) on the front side of the cleaned gallium oxide substrate (2) by adopting hydride vapor phase epitaxy technology HVPE method, depositing ohmic cathode metal (1) on the back side of the gallium oxide substrate by adopting magnetron sputtering to form a zigzag ohmic contact structure, and performing ohmic annealing on the cathode metal (1);
5) and forming an anode pattern on the front surface of the gallium oxide lightly doped epitaxial layer (3) by adopting a photoetching process, depositing anode metal (4) by adopting electron beam evaporation according to the anode photoetching pattern, and stripping metal materials outside the anode photoetching pattern to finish the manufacture of the device.
7. The method according to claim 8, characterized in that, in the step 4), the hydride vapor phase epitaxy HVPE technique is adopted to carry out the epitaxial light doping gallium oxide epitaxial layer (3) on the front surface of the cleaned gallium oxide substrate (2), and the following is realized:
4a) setting hydride vapor phase epitaxy HVPE process conditions: in the atmosphere of ammonia gas, in a high-temperature reaction zone of a hydride vapor phase epitaxy HVPE vertical reactor, reacting hydrogen chloride gas with high-purity metal Ga at the temperature of 800-900 ℃ to generate GaCl and GaCl 3 ；
4b) Putting the cleaned gallium oxide substrate (2) into an HVPE vertical reactor;
4c) reacting GaCl and GaCl generated in the high-temperature reaction zone 3 Pushing the substrate into a low-temperature reaction zone, placing the gallium oxide substrate (2) in the HVPE vertical reactor with the front side facing upwards into the low-temperature reaction zone, and enabling products GaCl and GaCl in the high-temperature reaction zone to be at the temperature of 500-650 DEG C 3 Reacts with oxygen to generate a gallium oxide lightly doped epitaxial layer (3) on the gallium oxide substrate (2).
8. The method as claimed in claim 6, wherein in the step 4), magnetron sputtering is adopted to deposit ohmic cathode metal on the back of the gallium oxide substrate, and the process conditions are as follows: the power is 100-300W, the sputtering time is 30-90 minutes, the pressure is 6-12 mtorr, and the ambient temperature is 25 ℃.
9. The method of claim 6, wherein the annealing of the ohmic cathode metal in step 4) is performed in a nitrogen atmosphere at an annealing temperature of 400 to 500 ℃ for 1 to 3 minutes.
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