A self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high thermal conductivity substrate and a method of making the same

Abstract

The application discloses a diamond high-heat-conductivity substrate self-aligned anode ultra-wide band gap semiconductor diode rectifier device and a preparation method thereof. The device comprises a gallium oxide epitaxial wafer on a diamond substrate, an ion implantation area is arranged at an upper end of the gallium oxide epitaxial wafer, a cathode electrode is prepared on the ion implantation area, an anode electrode is prepared at another upper end of the gallium oxide epitaxial wafer on the diamond substrate, the ion implantation area reduces the ohmic contact resistance between the cathode electrode and the gallium oxide epitaxial wafer on the diamond substrate, and the anode electrode forms a Schottky contact with the gallium oxide epitaxial wafer on the diamond substrate. The preparation method comprises the following steps: pretreating the gallium oxide epitaxial wafer on the diamond substrate; ion implantation; preparing the cathode electrode and the anode electrode; self-aligned anode etching and in-situ annealing; and finally forming the gallium oxide self-aligned anode diode on the diamond. The application simplifies the device preparation process steps and improves the breakdown voltage of the device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microelectronics technology, and particularly relates to a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate and a preparation method thereof. BACKGROUND

[0002] As an ultra-wide bandgap semiconductor material, gallium oxide has a higher bandgap, critical breakdown field strength and Baliga figure of merit than wide bandgap materials (such as silicon carbide and gallium nitride), and thus has high power conversion efficiency and current handling capability. One of the limitations of the application of gallium oxide in the high-power field is that the thermal conductivity of gallium oxide material is very low, and there is a self-heating effect at high voltage, which causes the current density of the device to decrease, and seriously affects the reliability of the device. Another limitation is that it is difficult to form a high breakdown voltage in a large-current diode. At high voltage, the electric field concentration near the anode can cause the device to break down prematurely, greatly reducing the breakdown voltage of the device.

[0003] The patent application file with the publication number CN115579396A discloses a diamond junction field effect transistor and a preparation method thereof. The junction field effect transistor is formed by a p-type diamond epitaxial layer and an n-type gallium oxide epitaxial layer. However, due to the low carrier mobility of the p-type diamond, the etching damage of the gallium oxide epitaxial layer causes a large impact on the gate control ability, and thus the prepared junction field effect transistor has a low forward current and a low transconductance. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application aims to provide a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate and a preparation method thereof. The device improves the breakdown voltage and the forward current, enhances the overall heat dissipation capacity of the device, and reduces the impact of the process on the performance of the device. The ultra-wide bandgap semiconductor diode rectifier device is prepared by using a self-aligned anode and an in-situ annealing process. The anode metal is used as a mask for etching, and the etching is performed at 50-200℃. The in-situ annealing is completed, the lateral electric field and the vertical electric field at the edge of the anode are smoothed, the damage caused by etching is reduced, and when the area of the anode is large, the width of the depletion layer caused by etching damage can be ignored. The reverse withstand voltage capability and the forward conduction current of the diode are improved. By using a high-thermal-conductivity diamond substrate, the heat dissipated through the substrate is increased at the same power, the overall temperature rise of the device is reduced, and the heat dissipation problem is solved.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0006] The application discloses a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate, which comprises a gallium oxide epitaxial wafer 1 arranged on the diamond substrate, an ion implantation area 2 arranged at one end of the gallium oxide epitaxial wafer 1, a cathode electrode 3 arranged above the ion implantation area 2, and an anode electrode 4 arranged at the other end of the gallium oxide epitaxial wafer 1.

[0007] The diamond substrate can be replaced by a silicon or aluminum nitride or silicon carbide substrate.

[0008] The ion implantation area 2 is a silicon ion implanted gallium oxide epitaxial layer.

[0009] The application further discloses a preparation method of the self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on the diamond high-thermal-conductivity substrate.

[0010] Step 1, pretreatment of the gallium oxide epitaxial wafer 1 deposited on the diamond substrate:

[0011] The gallium oxide epitaxial wafer 1 deposited on the diamond substrate is selected, and then is sequentially subjected to ultrasonic cleaning by using acetone and isopropyl alcohol, is immersed in a piranha solution, and is dried by blowing, so as to obtain the pretreated gallium oxide epitaxial wafer 1.

[0012] Step 2, ion implantation:

[0013] The ion implantation area is defined on the pretreated gallium oxide epitaxial wafer 1 by using photolithography, silicon ions are implanted to form donor type doping, and after the silicon ion implantation is completed, annealing treatment is performed, so as to obtain the ion implantation area 2.

[0014] Step 3, preparation of the cathode electrode 3:

[0015] The cathode area is defined by using photolithography, the cathode area is located above the ion implantation area 2 formed after the silicon ion implantation in step 2, metal deposition of the cathode ohmic contact is completed by using electron beam evaporation, the cathode metal is deposited, after the cathode metal is deposited, acetone or NMP water bath heating is used, then ultrasonic cleaning is sequentially performed in acetone and isopropyl alcohol, cathode metal stripping is completed, after the stripping, annealing treatment is performed, and the cathode metal area is formed.

[0016] Step 4, preparation of the anode electrode 4:

[0017] The anode area is defined on the gallium oxide epitaxial wafer 1 after the cathode metal is deposited in step 3 by using photolithography, metal deposition of the anode Schottky contact is completed by using electron beam evaporation, the anode metal is deposited, a square anode or a circular anode is prepared, acetone or NMP water bath heating is used, then ultrasonic cleaning is sequentially performed in acetone and isopropyl alcohol, anode metal stripping is completed, and the anode metal area is formed.

[0018] Step 5, self-aligned anode etching and in-situ annealing:

[0019] Using the anode metal region formed in step 4 as a mask, self-aligned anode etching is performed by dry etching technology, using boron trichloride or chlorine as working gas and argon or oxygen as carrier gas, etching is performed at a pressure of 5-20 mTorr, in-situ annealing is completed, and a self-aligned anode diode of gallium oxide on diamond is obtained.

[0020] The ultrasonic cleaning power in step 1 is 10-60 W, and the ultrasonic cleaning time is 3-15 min; the piranha solution comprises H2SO4:H2O2=6:1-3:1 by volume ratio; and the soaking time is 5-10 min.

[0021] The silicon ion implantation dose in step 2 is 30-200 cm -2 , and the implantation energy is 5-20 keV; the annealing temperature is 900-1000℃; and the annealing time is 1-2 min.

[0022] The evaporation rate of the electron beam evaporation in step 3 is 0.1-0.3 nm / s; the water bath temperature is 60-80℃, the water bath heating time is 10-30 min; the ultrasonic cleaning power is 10-60 W, and the ultrasonic cleaning time is 5-15 min; the annealing temperature is 400-500℃, the annealing nitrogen flow rate is 2-6 sccm, and the annealing time is 40-70 s.

[0023] The evaporation rate of the electron beam evaporation in step 4 is 0.1-0.3 nm / s; the area of the square anode is (0.5-2) mm x (0.5-2) mm, and the radius of the circular anode is 0.5-2 mm; the water bath temperature is 60-80℃, and the water bath heating time is 10-30 min; the ultrasonic cleaning power is 10-60 W, and the ultrasonic cleaning time is 5-15 min.

[0024] The gas flow rate of boron trichloride or chlorine in step 5 is 10-50 sccm, the gas flow rate of argon or oxygen is 1-10 sccm; the etching depth is 50-100 nm, and the etching temperature is 50-200℃; and the self-aligned anode etching angle can be varied from 0 to 180 degrees.

[0025] The cathode metal or anode metal comprises any one or more of titanium, aluminum, platinum, tungsten, chromium, molybdenum, tantalum, nickel, gold, or any combination thereof.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] 1. The gallium oxide device with high-thermal-conductivity diamond substrate has lower temperature rise and better heat dissipation effect compared with sapphire, silicon carbide and aluminum nitride substrates when the device works under the same power.

[0028] 2. The self-aligned anode etching and in-situ annealing process is used, the square anode with (0.5-2) mm* (0.5-2) mm or the circular anode with a radius of 0.5-2 mm is used, the anode area is large, the width of the depletion layer caused by etching damage can be ignored, the in-situ annealing improves the Schottky barrier height, reduces the interface state density caused by etching damage, reduces the influence of etching on the forward current density, and improves the breakdown voltage and reverse leakage current of the device.

[0029] In conclusion, the process steps of the device are simple, the processes used are relatively mature for gallium oxide device preparation, the gallium oxide device with high-thermal-conductivity diamond substrate has low temperature rise and good heat dissipation effect, the self-aligned anode technology is introduced, the anode metal is used as a mask for etching, which is different from the traditional etching with photoresist or dielectric layer as a mask, simplifies the process steps of device preparation, improves the breakdown voltage of the device, and the introduced self-aligned anode process does not have negative effects on the performance of the device. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a structure schematic diagram of the device of the present application.

[0031] Figure 2 It is a manufacturing flow chart of the device of the present application.

[0032] Figure 3 It is a manufacturing sub-step flow chart of the device of the present application.

[0033] Figure 4 It is a structure schematic diagram of a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device of a high-thermal-conductivity substrate replacement scheme.

[0034] Figure 5 It is a structure schematic diagram of a diode rectifier device with a self-aligned anode etching angle change.

[0035] Figure 6 It is a comparison diagram of reverse characteristics of a self-aligned anode diode device on a diamond substrate and a common gallium oxide diode device of the present application.

[0036] Figure 7 It is a comparison diagram of forward characteristics of a self-aligned anode diode device on a diamond substrate and a common gallium oxide diode device of the present application.

[0037] In the drawings, 1 is a gallium oxide epitaxial wafer, 2 is an ion implantation region, 3 is a cathode electrode, and 4 is an anode electrode. DETAILED DESCRIPTION

[0038] The technical solutions adopted by the present application will be further described below in combination with the drawings and specific embodiments.

[0039] Gallium oxide has important application prospects in high-voltage power and other fields as a super-wide bandgap semiconductor. The present application aims to develop a large-current gallium oxide power diode applicable to practical industries. Two problems are mainly solved, the first being the heat dissipation problem of the gallium oxide device, and the second being the reverse voltage problem of the large-current gallium oxide diode. The thermal conductivity of gallium oxide material is very low, and there is heat accumulation near the anode under large-current conditions. The present application proposes a diamond substrate gallium oxide diode to alleviate the heat accumulation near the gallium oxide anode and improve the overall heat dissipation capacity of the device. The reverse leakage and breakdown voltage of the current gallium oxide diode are usually much lower than those of small-area devices with the same structure, because the probability of defects such as cavities, dislocations or polycrystalline inclusions in the active region of the device is much higher, so it is usually difficult to achieve a high breakdown voltage for a large-current diode. The present application proposes a self-aligned anode structure to alleviate the electric field accumulation near the anode under high voltage and improve the overall breakdown voltage of the device.

[0040] As shown in Figure 1 The present application provides a self-aligned anode super-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate, which comprises a gallium oxide epitaxial wafer 1 arranged on a diamond substrate, an ion implantation region 2 arranged at one end of the upper side of the gallium oxide epitaxial wafer 1, a cathode electrode 3 prepared on the upper side of the ion implantation region 2, and an anode electrode 4 prepared at the other end of the upper side of the gallium oxide epitaxial wafer 1. The ion implantation region 2 reduces the ohmic contact resistance between the cathode electrode 3 and the gallium oxide epitaxial wafer 1, and the anode electrode 4 forms a Schottky contact with the gallium oxide epitaxial wafer 1.

[0041] The diamond substrate of the gallium oxide epitaxial wafer 1 can effectively improve the heat dissipation capacity of the device. The ion implantation region 2 is a silicon ion implanted gallium oxide epitaxial layer, which can effectively reduce the ohmic contact resistance. The cathode electrode 3 and the anode electrode 4 can be used as a mask to complete self-aligned etching, thereby improving the breakdown voltage of the device.

[0042] The use of gallium oxide devices on a diamond substrate makes up for the low thermal conductivity of gallium oxide material, significantly improves the overall heat dissipation effect of the device, and improves the forward current of the device while improving the breakdown voltage of the device by using a lateral gallium oxide diode device structure and a large anode area. The use of self-aligned anode etching introduces little damage, further improving the breakdown voltage of the device.

[0043] As shown in Figures 2-3As shown, the application also provides a preparation method of a diamond high-thermal-conductivity-substrate self-aligned anode super-wide-bandgap semiconductor diode rectifier device, comprising the following steps:

[0044] Step 1: Preprocessing of the gallium oxide epitaxial wafer (1) deposited on the diamond substrate:

[0045] The gallium oxide epitaxial wafer (1) deposited on the diamond substrate with a smooth surface is selected, and then the wafer is ultrasonically cleaned in acetone and isopropyl alcohol for 3-15 min at an ultrasonic cleaning power of 10-60 W. The wafer is soaked in an arowana solution of H2SO4:H2O2=6:1-3:1 by volume ratio for 5-10 min to improve the surface quality of the gallium oxide epitaxial wafer 1, reduce the surface state and dangling bonds, and then dried with a nitrogen gun to obtain the pretreated gallium oxide epitaxial wafer 1.

[0046] Step 2: Ion implantation:

[0047] The ion implantation region is defined by photolithography on the pretreated gallium oxide epitaxial wafer 1 in step 1, and silicon ions are implanted to form donor-type doping. The silicon ion implantation dose is 30-200 cm -2 , and the implantation energy is 5-20 keV to reduce the ohmic contact resistance. After the silicon ion implantation, annealing treatment is performed at 900-1000℃ in a nitrogen atmosphere for 1-2 min to eliminate the damaged lattice and obtain the ion implantation region 2.

[0048] Step 3: Preparation of the cathode electrode 3:

[0049] The cathode region is defined by photolithography, which is located above the ion implantation region 2 formed after the silicon ion implantation in step 2. The metal deposition of the cathode ohmic contact is completed by electron beam evaporation. The cathode metal is deposited at a deposition rate of 0.1-0.3 nm / s. After the deposition of the cathode metal, the wafer is heated in an acetone or NMP water bath at 60-80℃ for 10-30 min, and then ultrasonically cleaned in acetone and isopropyl alcohol for 5-15 min at an ultrasonic cleaning power of 10-60 W to complete the stripping of the cathode metal. After stripping, the wafer is annealed at 400-500℃ in a nitrogen atmosphere at a flow rate of 2-6 sccm for 40-70 s to form the cathode metal region.

[0050] Step 4: Preparation of the anode electrode 4:

[0051] After the cathode metal is deposited in step 3, the anode region is defined on the gallium oxide epitaxial wafer 1 by lithography, and the metal deposition of the anode Schottky contact is completed by electron beam evaporation. The anode metal is deposited at a rate of 0.1 nm / s to 0.3 nm / s to form a square anode with an area of (0.5-2) mm x (0.5-2) mm or a circular anode with a radius of 0.5-2 mm. The wafer is then heated in an acetone or NMP water bath at 60-80°C for 10-30 min, and then ultrasonically cleaned in acetone and isopropyl alcohol for 5-15 min, respectively. The ultrasonic cleaning power is 10 W to 60 W. The anode metal is stripped to form an anode metal region.

[0052] Step 5, self-aligned anode etching and in-situ annealing:

[0053] The anode metal region formed in step 4 is used as a mask for self-aligned anode etching using dry etching technology. Boron trichloride or chlorine gas with a gas flow rate of 10-50 sccm is used as the etching element, and argon or oxygen gas with a gas flow rate of 1-10 sccm is used to improve the selectivity and directionality of the etching process. The etching is carried out at a pressure of 5-20 mTorr, with an etching depth of 50-100 nm and an etching temperature of 50-200°C. In-situ annealing is completed to obtain a gallium oxide self-aligned anode diode on diamond. The self-aligned anode etching angle can vary from 0 to 180 degrees.

[0054] Example 1

[0055] A method for preparing a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate, comprising the following steps:

[0056] Step 1, pretreatment of the gallium oxide epitaxial wafer (1) deposited on the diamond substrate:

[0057] A gallium oxide epitaxial wafer (1) deposited on a diamond substrate with a smooth and flat surface is selected and ultrasonically cleaned in acetone and isopropyl alcohol for 3 min, respectively, with an ultrasonic cleaning power of 10 W. The gallium oxide epitaxial wafer 1 is immersed in a piranha solution with a volume ratio of H2SO4:H2O2=6:1 for 10 min to improve the surface quality of the gallium oxide epitaxial wafer 1 and reduce the surface state and dangling bonds. Then the wafer is dried with a nitrogen gun to obtain a pretreated gallium oxide epitaxial wafer 1.

[0058] Step 2, ion implantation:

[0059] The ion implantation region is defined on the pretreated gallium oxide epitaxial wafer 1 in step 1 by lithography, and donor-type doping is formed by silicon ion implantation. The silicon ion implantation dose is 200 cm -2, the injection energy is 5 keV, and the ohmic contact resistance is reduced; after the silicon ion implantation is completed, annealing treatment is performed at 900 DEG C in a nitrogen atmosphere, the annealing time is 1 min, the damaged lattice is eliminated, and the ion implantation region 2 is obtained;

[0060] Step 3, preparing a cathode electrode 3:

[0061] The cathode region is defined by photolithography, the cathode region is located above the ion implantation region 2 formed after the silicon ion implantation in step 2, the metal deposition of the cathode ohmic contact is completed by electron beam evaporation, the cathode metal is deposited, the evaporation rate is 0.1 nm / s, after the cathode metal is deposited, NMP is used for heating in a 60 DEG C water bath for 30 min, and then ultrasonic cleaning is sequentially performed in acetone and isopropanol for 15 min, the ultrasonic cleaning power is 20 W, the cathode metal stripping is completed, after stripping, annealing treatment is performed at 400 DEG C in a nitrogen atmosphere with a flow rate of 2 sccm for 70 s, and the cathode metal region is formed;

[0062] Step 4, preparing an anode electrode 4:

[0063] The anode region is defined by photolithography on the gallium oxide epitaxial wafer 1 after the cathode metal is deposited in step 3, the metal deposition of the anode Schottky contact is completed by electron beam evaporation, the anode metal is deposited, the evaporation rate is 0.1 nm / s, a square anode with an area of 0.5 mm * 0.5 mm is prepared, NMP is used for heating in a 80 DEG C water bath for 30 min, and then ultrasonic cleaning is sequentially performed in acetone and isopropanol for 15 min, the ultrasonic cleaning power is 10 W, the anode metal stripping is completed, and the anode metal region is formed;

[0064] Step 5, self-aligned anode etching and in-situ annealing:

[0065] The anode metal region formed in step 4 is used as a mask, self-aligned anode etching is performed by using dry etching technology, chlorine gas with a flow rate of 50 sccm is used as an etching nucleus, oxygen gas with a flow rate of 10 sccm is used to improve the selectivity and directivity of the etching process, etching is performed at a pressure of 5 mTorr, the etching depth is 50 nm, and etching is performed at 50 DEG C, so that in-situ annealing is completed, and a diamond gallium oxide self-aligned anode diode is obtained.

[0066] Example 2

[0067] A preparation method of a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate, comprising the following steps:

[0068] Step 1, pretreating a gallium oxide epitaxial wafer (1) deposited on a diamond substrate:

[0069] Select the surface smooth and smooth deposited on the diamond substrate of gallium oxide epitaxial wafer (1), and sequentially use acetone, isopropyl alcohol ultrasonic cleaning 15 min, ultrasonic cleaning power is 60W, according to the volume ratio, using H2SO4: H2O2 = 3:1 piranha solution immersion gallium oxide epitaxial wafer 1, soaking time is 5 min, improve the surface quality of gallium oxide epitaxial wafer 1, reduce the surface state and dangling bond, then dry with nitrogen gun, get the pretreated gallium oxide epitaxial wafer 1;

[0070] Step 2, ion implantation:

[0071] On the gallium oxide epitaxial wafer 1 pretreated in step 1, lithography defines the ion implantation area, silicon ion implantation is used to form donor type doping, silicon ion implantation dose is 30cm -2 , implantation energy is 20keV, and ohmic contact resistance is reduced; after completing silicon ion implantation, annealing treatment is carried out at 1000℃ in nitrogen atmosphere, and the annealing time is 2min, so as to eliminate the damaged lattice, and obtain ion implantation area 2;

[0072] Step 3, preparation of cathode electrode 3:

[0073] The cathode region is defined by lithography, which is located above the ion implantation area 2 formed after step 2 silicon ion implantation, and the metal deposition of cathode ohmic contact is completed by electron beam evaporation, the cathode metal is deposited, the evaporation rate is 0.3nm / s, after the deposition of cathode metal, acetone is used in 80℃ water bath heating for 10min, and then ultrasonic cleaning in acetone, isopropyl alcohol is sequentially carried out for 5min, and the ultrasonic cleaning power is 10W, the cathode metal stripping is completed, after stripping, 500℃, nitrogen flow is 6sccm, annealing treatment is carried out for 40s, and the cathode metal area is formed;

[0074] Step 4, preparation of anode electrode 4:

[0075] After the deposition of cathode metal on the gallium oxide epitaxial wafer 1 in step 3, the anode region is defined by lithography, the metal deposition of anode Schottky contact is completed by electron beam evaporation, the anode metal is deposited, the evaporation rate is 0.3nm / s, the circular anode with a radius of 0.5mm is made, acetone is used in 60℃ water bath heating for 10min, and then ultrasonic cleaning in acetone, isopropyl alcohol is sequentially carried out for 5min, and the ultrasonic cleaning power is 60W, the anode metal stripping is completed, and the anode metal area is formed;

[0076] Step 5, self-aligned anode etching and in-situ annealing:

[0077] Using the anode metal region formed in step 4 as a mask, self-aligned anode etching is performed by using dry etching technology, boron trichloride with a gas flow of 10 sccm is used as an etching element, argon gas with a gas flow of 1 sccm is used to improve the selectivity and directivity of the etching process, the etching is performed at a pressure of 20 mTorr, the etching depth is 100 nm, and the etching is performed at 200℃, so as to complete in-situ annealing, and a self-aligned anode diode of gallium oxide on diamond is obtained.

[0078] Embodiment 3

[0079] A preparation method of a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate, comprising the following steps:

[0080] Step 1, pretreatment is performed on a gallium oxide epitaxial wafer (1) deposited on a diamond substrate:

[0081] The gallium oxide epitaxial wafer (1) deposited on the diamond substrate and having a smooth and flat surface is selected, and then the gallium oxide epitaxial wafer 1 is sequentially immersed in acetone and isopropanol for ultrasonic cleaning for 5 min, the ultrasonic cleaning power is 30 W, a piranha solution of H2SO4:H2O2=4:1 is used according to the volume ratio, the gallium oxide epitaxial wafer 1 is soaked for 10 min, the surface quality of the gallium oxide epitaxial wafer 1 is improved, the surface state and dangling bonds are reduced, and then the gallium oxide epitaxial wafer 1 is dried by a nitrogen gun, to obtain a pretreated gallium oxide epitaxial wafer 1;

[0082] Step 2, ion implantation:

[0083] The ion implantation region is defined on the pretreated gallium oxide epitaxial wafer 1 in step 1 by photolithography, and silicon ion implantation is performed to form donor-type doping, the silicon ion implantation dose is 120 cm -2 , the implantation energy is 15 keV, and the ohmic contact resistance is reduced; after the silicon ion implantation is completed, annealing treatment is performed at 950℃ in a nitrogen atmosphere for 1.5 min, the damaged lattice is eliminated, and an ion implantation region 2 is obtained;

[0084] Step 3, preparation of a cathode electrode 3:

[0085] The cathode region is defined by photolithography, the cathode region is located above the ion implantation region 2 formed after the silicon ion implantation in step 2, and metal deposition of the cathode ohmic contact is completed by using electron beam evaporation, the cathode metal is deposited, the evaporation rate is 0.1 nm / s, after the cathode metal is deposited, acetone is used for heating in a 60℃ water bath for 25 min, and then the cathode metal is sequentially cleaned in acetone and isopropanol for 5 min by ultrasonic cleaning, the ultrasonic cleaning power is 60 W, the cathode metal is stripped, and after stripping, annealing treatment is performed at 400℃ for 45 s in a nitrogen atmosphere with a nitrogen flow of 2 sccm, to form a cathode metal region;

[0086] Step 4, preparation of an anode electrode 4:

[0087] After the cathode metal is deposited in step 3, the anode region is defined on the gallium oxide epitaxial wafer 1 by lithography, and the metal deposition of the anode Schottky contact is completed by electron beam evaporation. The anode metal is deposited at a rate of 0.15 nm / s, and a square anode with an area of 2 mm x 2 mm is prepared. After being heated in an acetone water bath at 60°C for 30 min, the anode metal is then cleaned in acetone and isopropyl alcohol successively for 15 min by ultrasonic cleaning, and the ultrasonic cleaning power is 40 W. The anode metal is stripped to form an anode metal region.

[0088] Step 5, self-aligned anode etching and in-situ annealing:

[0089] The anode metal region formed in step 4 is used as a mask, and self-aligned anode etching is performed by using dry etching technology. Chlorine gas with a flow rate of 20 sccm is used as the etching nucleus, and argon gas with a flow rate of 9 sccm is used to improve the selectivity and directionality of the etching process. The etching is performed at a pressure of 6 mTorr, and the etching depth is 70 nm. The etching is performed at 150°C, and in-situ annealing is completed. A gallium oxide self-aligned anode diode on diamond is obtained.

[0090] Example 4

[0091] A method for preparing a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate, comprising the following steps:

[0092] Step 1, pretreatment of the gallium oxide epitaxial wafer 1 deposited on the diamond substrate:

[0093] A gallium oxide epitaxial wafer 1 deposited on a diamond substrate with a smooth and flat surface is selected, and is then cleaned successively in acetone and isopropyl alcohol for 12 min by ultrasonic cleaning, and the ultrasonic cleaning power is 50 W. The gallium oxide epitaxial wafer 1 is soaked in a piranha solution with a volume ratio of H2SO4:H2O2=3:1 for 10 min, so as to improve the surface quality of the gallium oxide epitaxial wafer 1, reduce the surface state and dangling bonds, and then is dried by a nitrogen gun. A pretreated gallium oxide epitaxial wafer 1 is obtained.

[0094] Step 2, ion implantation:

[0095] The ion implantation region is defined on the pretreated gallium oxide epitaxial wafer 1 in step 1 by lithography, and donor-type doping is formed by silicon ion implantation. The silicon ion implantation dose is 60 cm -2 , and the implantation energy is 15 keV, so as to reduce the ohmic contact resistance. After the silicon ion implantation is completed, the ion implantation region 2 is obtained by annealing treatment at 900°C in a nitrogen atmosphere for 1 min, so as to eliminate the damaged lattice.

[0096] Step 3, preparation of a cathode electrode 3:

[0097] The cathode region is defined by photolithography on the ion implantation region 2 formed after the silicon ion implantation in step 2, and the metal deposition of the cathode ohmic contact is completed by electron beam evaporation, the cathode metal is deposited at a deposition rate of 0.2 nm / s, after the deposition of the cathode metal, the wafer is heated in an acetone water bath at 60°C for 10 min, and then ultrasonic cleaning is sequentially performed in acetone and isopropyl alcohol for 12 min, the ultrasonic cleaning power is 35 W, the cathode metal is stripped, and after stripping, the wafer is annealed at 420°C for 60 s in a nitrogen flow of 5 sccm, and the cathode metal region is formed;

[0098] Step 4, preparation of anode electrode 4:

[0099] The anode region is defined by photolithography on the gallium oxide epitaxial wafer 1 after the deposition of the cathode metal in step 3, the metal deposition of the anode Schottky contact is completed by electron beam evaporation, the anode metal is deposited at a deposition rate of 0.2 nm / s, a circular anode with a radius of 2 mm is made, and then ultrasonic cleaning is sequentially performed in acetone and isopropyl alcohol for 10 min, the ultrasonic cleaning power is 45 W, the anode metal is stripped, and the anode metal region is formed;

[0100] Step 5, self-aligned anode etching and in-situ annealing:

[0101] The anode metal region formed in step 4 is used as a mask, and self-aligned anode etching is performed by using dry etching technology, boron trichloride with a gas flow of 25 sccm is used as an etching nucleus, oxygen with a gas flow of 6 sccm is used to improve the selectivity and directionality of the etching process, the etching is performed at a pressure of 10 mTorr, the etching depth is 60 nm, and the etching is performed at 100°C, thereby completing in-situ annealing, and a diamond self-aligned anode gallium oxide diode is obtained.

[0102] Example 5

[0103] A preparation method of a diamond high-thermal-conductivity-substrate self-aligned anode ultra-wide-bandgap semiconductor diode rectifier device, comprising the following steps:

[0104] Step 1, pretreatment of a gallium oxide epitaxial wafer (1) deposited on a diamond substrate:

[0105] A gallium oxide epitaxial wafer (1) deposited on a diamond substrate with a smooth and flat surface is selected, and ultrasonic cleaning is sequentially performed in acetone and isopropyl alcohol for 12 min, the ultrasonic cleaning power is 25 W, the gallium oxide epitaxial wafer 1 is soaked in a piranha solution with a volume ratio of H2SO4:H2O2=5:1, the soaking time is 7 min, the surface quality of the gallium oxide epitaxial wafer 1 is improved, the surface state and dangling bonds are reduced, and then the wafer is dried by a nitrogen gun, thereby obtaining a pretreated gallium oxide epitaxial wafer 1;

[0106] Step 2, ion implantation:

[0107] In step 1, the gallium oxide epitaxial wafer 1 after pretreatment is photoetched to define the ion implantation area, silicon ions are implanted to form donor type doping, the silicon ion implantation dose is 100cm -2 , the implantation energy is 15keV, and the ohmic contact resistance is reduced; after completing the silicon ion implantation, annealing treatment is carried out at 900 DEG C in a nitrogen atmosphere, the annealing time is 2min, the damaged lattice is eliminated, and the ion implantation area 2 is obtained;

[0108] Step 3, preparation of cathode electrode 3:

[0109] The cathode area is defined by photoetching, the cathode area is located above the ion implantation area 2 formed after the silicon ion implantation in step 2, the metal deposition of the cathode ohmic contact is completed by electron beam evaporation, the cathode metal is deposited, the evaporation rate is 0.2nm / s, after the deposition of the cathode metal, acetone is used in a 70 DEG C water bath heating for 15min, and then ultrasonic cleaning is sequentially carried out in acetone and isopropyl alcohol for 10min, the ultrasonic cleaning power is 30W, the cathode metal stripping is completed, and the cathode metal area is formed after stripping at 470 DEG C, the nitrogen flow is 3sccm, and the annealing treatment is carried out for 55s;

[0110] Step 4, preparation of anode electrode 4:

[0111] The anode area is defined by photoetching on the gallium oxide epitaxial wafer 1 after the deposition of the cathode metal in step 3, the metal deposition of the anode Schottky contact is completed by electron beam evaporation, the anode metal is deposited, the evaporation rate is 0.15nm / s, a circular anode with a radius of 0.9mm is prepared, NMP is used in a 75 DEG C water bath heating for 25min, and then ultrasonic cleaning is sequentially carried out in acetone and isopropyl alcohol for 8min, the ultrasonic cleaning power is 35W, the anode metal stripping is completed, and the anode metal area is formed;

[0112] Step 5, self-aligned anode etching and in-situ annealing:

[0113] The anode metal area formed in step 4 is used as a mask, self-aligned anode etching is carried out by using dry etching technology, chlorine gas with a gas flow of 30sccm is used as an etching nucleus, argon gas with a gas flow of 7sccm is used to improve the selectivity and directivity of the etching process, the etching is carried out at a pressure of 9mTorr, the etching depth is 75nm, and the in-situ annealing is completed at 150 DEG C, and a gallium oxide self-aligned anode diode on diamond is obtained.

[0114] The key point and protection point of the application are:

[0115] 1. The high-thermal-conductivity diamond substrate is used to improve the bottom heat dissipation capacity of the gallium oxide diode.

[0116] 2. The self-aligned anode process using anode metal as a mask for etching improves the breakdown voltage of the device, in-situ annealing is used in the etching process to reduce etching damage, the width of the depletion layer introduced by etching damage can be ignored when the anode area is large, and the forward current of the device is improved.

[0117] As shown in Figure 4 , it is a high thermal conductivity substrate replacement scheme self-aligned anode ultra-wide bandgap semiconductor diode rectifier device structure schematic diagram, the rest of the high thermal conductivity substrate such as silicon, aluminum nitride, silicon carbide substrate can replace diamond substrate, the key points and protection points of this scheme are consistent with the present application, and are considered as the same structure.

[0118] As shown in Figure 5 , the anode self-aligned etching angle can be changed from 0 to 180 degrees, and the device structure for other etching angles, the key points and protection points of this scheme are consistent with the present application, and are considered as the same structure.

[0119] As shown in Figure 6 , the present application replaces the substrate of the diode on the gallium oxide substrate with a diamond substrate and introduces a self-aligned anode process, Figure 6 It can be seen that the device of the present application has lower leakage current and higher breakdown voltage at higher voltage, and the reverse breakdown voltage is above 1200V, while the reverse breakdown voltage of the conventional gallium oxide Schottky diode is about 200V, so the reverse voltage of the device of the present application is significantly improved.

[0120] As shown in Figure 7 , the present application replaces the substrate of the diode on the gallium oxide substrate with a diamond substrate and introduces a self-aligned anode process, since the process introduces less damage, and the heat dissipation effect of the diamond substrate is better, Figure 7 It can be seen that the device of the present application has larger forward current than the conventional gallium oxide diode at the same forward voltage, and the current is close to 800A / cm 2 when the forward voltage is 3V, while the current of the conventional gallium oxide Schottky diode is only 400A / cm 2 Therefore, the forward current of the device of the present application is significantly improved.

Claims

1. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device, characterized in that, The application relates to a gallium oxide epitaxial wafer (1) arranged on a diamond substrate, an ion implantation region (2) arranged at an upper end of the gallium oxide epitaxial wafer (1), a cathode electrode (3) arranged above the ion implantation region (2), and an anode electrode (4) arranged at another upper end of the gallium oxide epitaxial wafer (1); the ion implantation region (2) reduces the ohmic contact resistance between the cathode electrode (3) and the gallium oxide epitaxial wafer (1), and the anode electrode (4) forms a Schottky contact with the gallium oxide epitaxial wafer (1). The application relates to a preparation method of a self-aligned anode ultra-wide bandgap semiconductor diode rectifier device on a diamond high-thermal-conductivity substrate. Step 1: pretreatment of a gallium oxide epitaxial wafer (1) deposited on a diamond substrate; The gallium oxide epitaxial wafer (1) deposited on the diamond substrate is selected, and is sequentially subjected to ultrasonic cleaning by using acetone and isopropyl alcohol, is immersed in an arowana solution, and is then dried to obtain the pretreated gallium oxide epitaxial wafer (1). Step 2: ion implantation The gallium oxide epitaxial wafer (1) after the pretreatment in step 1 is subjected to photoetching definition of an ion implantation region, silicon ion implantation is adopted to form donor-type doping, and after the silicon ion implantation is completed, annealing treatment is carried out to obtain the ion implantation region (2). Step 3: preparation of a cathode electrode (3) A cathode region is defined by photoetching, the cathode region is arranged above the ion implantation region (2) formed after the silicon ion implantation in step 2, metal deposition of a cathode ohmic contact is completed by adopting electron beam evaporation, the cathode metal is deposited, after the cathode metal is deposited, acetone or NMP water bath heating is used, then ultrasonic cleaning in acetone and isopropyl alcohol is sequentially carried out, cathode metal stripping is completed, and after the stripping, annealing treatment is carried out to form a cathode metal region. Step 4: preparation of an anode electrode (4) After the cathode metal is deposited in step 3, an anode region is defined on the gallium oxide epitaxial wafer (1) by photoetching, metal deposition of an anode Schottky contact is completed by adopting electron beam evaporation, the anode metal is deposited, a square anode or a circular anode is prepared, acetone or NMP water bath heating is used, then ultrasonic cleaning in acetone and isopropyl alcohol is sequentially carried out, anode metal stripping is completed, and an anode metal region is formed. Step 5: self-aligned anode etching and in-situ annealing The anode metal region formed in step 4 is used as a mask, self-aligned anode etching is carried out by adopting dry etching technology, boron trichloride or chlorine gas is used as working gas, argon gas or oxygen gas is used as carrier gas, etching is carried out under a pressure of 5-20 mTorr, in-situ annealing is completed, and a gallium oxide self-aligned anode diode on a diamond is obtained.

2. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device according to claim 1, characterized in that, The diamond substrate can be replaced by a silicon substrate or an aluminum nitride substrate or a silicon carbide substrate.

3. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device according to claim 1, characterized in that, The ion implantation region (2) is a gallium oxide epitaxial layer with silicon ion implantation.

4. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device according to claim 1, characterized in that, In step 1, the ultrasonic cleaning power is 10-60 W, and the ultrasonic cleaning time is 3-15 min; the arowana solution comprises H2SO4:H2O2=6:1-3:1 in terms of volume ratio, and the immersion time is 5-10 min.

5. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device according to claim 1, wherein, The silicon ion implantation dose in step 2 is 30-200 cm -2 The implantation energy is 5-20 keV; the annealing temperature is 900-1000 °C; and the annealing time is 1-2 min.

6. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device according to claim 1, wherein, The evaporation rate of the electron beam evaporation in the step 3 is 0.1-0.3 nm / s; the temperature of the water bath is 60-80℃, and the water bath heating time is 10-30 min; the power of the ultrasonic cleaning is 10-60 W, and the ultrasonic cleaning time is 5-15 min; the annealing temperature is 400-500℃, the annealing nitrogen flow rate is 2-6 sccm, and the annealing time is 40-70 s.

7. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device according to claim 1, wherein, The evaporation rate of the electron beam evaporation in the step 4 is 0.1-0.3 nm / s; the area of the square anode is (0.5-2) mm×(0.5-2) mm, and the radius of the circular anode is 0.5-2 mm; the temperature of the water bath is 60-80℃, and the water bath heating time is 10-30 min; the power of the ultrasonic cleaning is 10-60 W, and the ultrasonic cleaning time is 5-15 min.

8. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device according to claim 1, wherein, The gas flow rate of the boron trichloride or chlorine gas in the step 5 is 10-50 sccm, and the gas flow rate of the argon or oxygen gas is 1-10 sccm; the etching depth is 50-100 nm, and the etching temperature is 50-200℃; the etching angle of the self-aligned anode can be varied from 0 to 180 degrees.

9. A diamond high thermal conductivity on-substrate self-aligned anode ultra-wide bandgap semiconductor diode rectifier device according to claim 1, characterized by, The cathode metal or anode metal comprises any one or more of titanium, aluminum, platinum, tungsten, chromium, molybdenum, tantalum, nickel, gold, or any combination thereof.

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