CN115064581A - Gallium oxide pn diode based on longitudinal gradient p-type doping concentration structure and preparation method - Google Patents
Gallium oxide pn diode based on longitudinal gradient p-type doping concentration structure and preparation method Download PDFInfo
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- AJNVQOSZGJRYEI-UHFFFAOYSA-N digallium;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Ga+3].[Ga+3] AJNVQOSZGJRYEI-UHFFFAOYSA-N 0.000 title claims abstract description 120
- 229910001195 gallium oxide Inorganic materials 0.000 title claims abstract description 120
- 238000002360 preparation method Methods 0.000 title abstract description 10
- 239000002184 metal Substances 0.000 claims abstract description 70
- 239000004065 semiconductor Substances 0.000 claims abstract description 70
- 229910052751 metal Inorganic materials 0.000 claims abstract description 69
- 239000000463 material Substances 0.000 claims abstract description 58
- 239000000758 substrate Substances 0.000 claims abstract description 36
- 230000015556 catabolic process Effects 0.000 claims abstract description 25
- 230000008021 deposition Effects 0.000 claims abstract description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 34
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 33
- 238000000034 method Methods 0.000 claims description 26
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 21
- 238000000151 deposition Methods 0.000 claims description 21
- 239000001301 oxygen Substances 0.000 claims description 21
- 229910052760 oxygen Inorganic materials 0.000 claims description 21
- 229910052786 argon Inorganic materials 0.000 claims description 17
- 238000012545 processing Methods 0.000 claims description 16
- 238000001259 photo etching Methods 0.000 claims description 15
- 238000002248 hydride vapour-phase epitaxy Methods 0.000 claims description 14
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 12
- 238000000137 annealing Methods 0.000 claims description 10
- 238000005516 engineering process Methods 0.000 claims description 10
- 150000002500 ions Chemical class 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 10
- 238000005566 electron beam evaporation Methods 0.000 claims description 7
- 238000004140 cleaning Methods 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 5
- 229910021641 deionized water Inorganic materials 0.000 claims description 5
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 4
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 claims description 3
- 239000005751 Copper oxide Substances 0.000 claims description 3
- 229910000431 copper oxide Inorganic materials 0.000 claims description 3
- 229910000480 nickel oxide Inorganic materials 0.000 claims description 3
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 claims description 3
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 3
- 229910001887 tin oxide Inorganic materials 0.000 claims description 3
- 239000000969 carrier Substances 0.000 claims description 2
- 230000001737 promoting effect Effects 0.000 claims 1
- XOYLJNJLGBYDTH-UHFFFAOYSA-M chlorogallium Chemical compound [Ga]Cl XOYLJNJLGBYDTH-UHFFFAOYSA-M 0.000 description 16
- 229920002120 photoresistant polymer Polymers 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- 230000005684 electric field Effects 0.000 description 3
- 239000007769 metal material Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 125000005842 heteroatom Chemical group 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000009210 therapy by ultrasound Methods 0.000 description 2
- 238000002207 thermal evaporation Methods 0.000 description 2
- 229910005191 Ga 2 O 3 Inorganic materials 0.000 description 1
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 1
- 238000000861 blow drying Methods 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002902 organometallic compounds Chemical class 0.000 description 1
- 238000000527 sonication Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
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Abstract
The invention discloses a gallium oxide pn diode based on a longitudinally-graded p-type doping concentration structure and a preparation method thereof, and mainly solves the problems that the reverse breakdown voltage of a device is improved and the forward on-resistance and the power consumption of the device are seriously increased in the prior art. It from bottom to top includes: cathode ohmic metal, gallium oxide substrate, gallium oxide drift layer, p-type semiconductor layer and anode metal, wherein the p-type semiconductor layer is formed by at least three layers of p-type semiconductor materials with different doping concentrations according to the doping concentrations of the p-type semiconductor materials from 1 x 10 16 cm ‑3 Gradation to 1X 10 20 cm ‑3 The gallium oxide drift layer is formed on the gallium oxide drift layer in a deposition mode from low to high in sequence, so that the gallium oxide drift layer is in contact with the p-type material with lower doping concentration, the anode metal is in contact with the p-type material with higher doping concentration, the reverse breakdown voltage of the device is improved, meanwhile, the on-resistance of the device is reduced, the Bay gain value of the gallium oxide device is improved, and the gallium oxide drift layer can be used for an electronic system.
Description
Technical Field
The invention belongs to the technical field of semiconductor devices, and particularly relates to a gallium oxide pn diode which can be used in the fields of electronic systems of communication, power electronics, signal processing and aerospace.
Technical Field
Gallium oxide is a novel ultra-wide bandgap semiconductor material, and the gallium oxide semiconductor material can be used for preparing a high-power device due to the characteristics of the wide bandgap of 4.6-4.9eV and the high critical breakdown field strength of 8 MV/cm. With the continuous progress of scientific technology, in the fields of communication, power electronics, signal processing, aerospace and the like, the performance of the traditional third-generation semiconductor GaN and SiC power devices cannot meet the requirement of higher working performance, and the gallium oxide power devices have lower on-resistance, lower power consumption and higher Bari plus merit figure under the same breakdown voltage.
At present, gallium oxide power devices mainly comprise diodes and triodes, wherein the diodes mainly comprise schottky diodes and heterojunction pn diodes. The pn diode is a p-n junction formed by a p-type semiconductor and an n-type semiconductor, forms space charge layers on both sides of the interface, is favorable for minority carrier operation, and is widely used for various rectifying circuits, detecting circuits, voltage stabilizing circuits and modulating circuits.
Since gallium oxide P-type doping is difficult to realize at present, other P-type semiconductor materials, such as nickel oxide, copper oxide, tin oxide, and n-type gallium oxide, are mainly used to form heterojunction pn diodes at present. Two very important device parameters for measuring the performance of a diode are reverse breakdown voltage and on-resistance, and the larger the reverse breakdown voltage is, or the smaller the on-resistance is, the better the performance of the device is. However, the forward characteristic and breakdown voltage of the gallium oxide diode at present are far from the limit of gallium oxide, and the barying plus optimum value BFOM of a gallium oxide device is far lower than an ideal value, so that the high-power output performance of the gallium oxide device is influenced, and the application of the gallium oxide device in the high-voltage field is limited.
Ma Xiao Hua et al, in patent No. 202111069074.7, disclose "a high breakdown voltage gallium oxide power diode and a method for making the same" using a thin NiO layer with P-type characteristics and beta-Ga 2 O 3 The drift layer forms a heterogeneous PN junction structure to reduce the peak electric field at the edge of the device, improve the interface characteristic of anode metal and gallium oxide, reduce reverse leakage current and improve the breakdown voltage of the gallium oxide diode.
Luxing et al, in patent application number 201710057175.X, have proposed "a gallium oxide based hetero PN junction diode and a method for manufacturing the same" by forming a hetero PN junction by using an amorphous or polycrystalline p-type oxide semiconductor layer and a monocrystalline n-type doped gallium oxide voltage-withstanding layer to reduce reverse leakage current and increase the breakdown voltage of the gallium oxide diode.
Although the two methods can improve the reverse breakdown voltage of the device, the forward on-resistance of the device is also seriously increased, the power consumption of the device is increased, and the Bari plus optimum value of the device cannot be maximally improved.
Disclosure of Invention
The invention aims to provide a gallium oxide pn diode with a longitudinally graded p-type doping concentration structure and a preparation method thereof aiming at overcoming the defects of the prior art, so as to improve the reverse breakdown voltage, reduce the on-resistance and improve the barying plus merit value of a gallium oxide device.
The technical idea for realizing the purpose of the invention is as follows: the p-type doping concentration of the p-type semiconductor layer in the pn junction is longitudinally gradually changed, so that ohmic contact is more easily formed after the anode metal is contacted with the p-type semiconductor material with higher doping concentration, and the on-resistance is reduced; after the low-doped gallium oxide drift layer is contacted with the p-type semiconductor material with the lower doping concentration, the peak electric field near the gallium oxide layer is relieved, the breakdown voltage of the device is improved, and the Baligold optimum BFOM of the gallium oxide device is improved.
According to the above thought, the technical scheme of the invention is as follows:
1. a gallium oxide pn diode with a longitudinal gradient p-type doping concentration structure comprises the following components from bottom to top: the GaN-based high-voltage power semiconductor device comprises cathode ohmic metal, a GaN substrate, a GaN drift layer, a p-type semiconductor layer and anode metal, and is characterized in that the p-type semiconductor layer adopts the p-type semiconductor layer with the longitudinal gradient doping concentration, so that the reverse breakdown voltage of the device is improved, the on-resistance of the device is reduced, and the Bari plus optimum value of the GaN-based device is improved.
Preferably, the p-type graded doping concentration ranges from 1 × 10 16 cm-3 is gradually changed to 1 x 10 20 cm-3。
Preferably, the longitudinal gradient doping concentration of the p-type semiconductor layer is formed by depositing at least three layers of p-type semiconductor materials with different p-type doping concentrations on the gallium oxide drift layer in sequence from low doping concentration to high doping concentration, the thickness of the p-type semiconductor material of each layer is 3-15nm, and the optional p-type semiconductor materials comprise nickel oxide, copper oxide and tin oxide.
Preferably, the metal of the cathode ohmic metal is Ti/Au, the thickness of the first layer of Ti close to the gallium oxide substrate layer is 20-50nm, and the thickness of the second layer of Au metal is 100-400 nm.
Preferably, the thickness of the gallium oxide substrate is 300-650 mu m, and the effective doping carrier concentration is 10 18 -10 20 cm-3, and the doping ion species is Si ions or Sn ions.
Preferably, the thickness of the gallium oxide drift layer is 3-15 μm, and the concentration of doping carriers is 10 16 -10 18 cm-3。
Preferably, the anode metal is Ni/Au metal, the thickness of the first layer of metal Ni is 45-60nm, and the thickness of the second layer of metal Au is 200-400 nm.
2. A method for manufacturing a gallium oxide pn diode with a longitudinally graded p-type doping concentration structure is characterized by comprising the following steps:
1) sequentially cleaning the gallium oxide substrate by acetone-isopropanol-deionized water;
2) performing epitaxial light-doped gallium oxide layer on the front side of the cleaned gallium oxide substrate by using a hydride vapor phase epitaxy technology HVPE method, depositing ohmic cathode metal on the back side of the gallium oxide substrate by using magnetron sputtering, and performing ohmic annealing on the ohmic cathode metal;
3) depositing a p-type semiconductor layer with a longitudinally graded doping concentration on a gallium oxide drift layer
3a) Forming a pattern on the front surface of the gallium oxide drift layer by adopting a photoetching process;
3b) setting magnetron sputtering process conditions: the power is 100-150W, the proportion of oxygen to argon is 5-50%, the processing time is 10-90 minutes, the pressure is 4-10mtorr, and the ambient temperature is 25 ℃;
3c) depositing a p-type semiconductor material with longitudinally graded doping concentration by magnetron sputtering according to the pattern, namely gradually increasing the proportion of oxygen to argon in the magnetron sputtering process to ensure that the newly deposited p-type doping concentration of each layer is higher than that of the semiconductor material deposited at the previous time, controlling the growth rate of each layer of p-type semiconductor material by controlling the power of magnetron sputtering, controlling the doping concentration of each layer of p-type semiconductor material by controlling the proportion of oxygen to argon, controlling the thickness of each layer of p-type semiconductor material by controlling the time of magnetron sputtering, and forming a longitudinally graded p-type semiconductor layer with doping concentration from low to high through multiple depositions;
4) and forming an anode pattern on the front surface of the p-type semiconductor layer with the longitudinal gradient doping concentration by adopting a photoetching process, and depositing and stripping anode metal by adopting electron beam evaporation according to the anode pattern to finish the manufacture of the device.
Because the p-type semiconductor layer with gradually changed longitudinal doping concentration is adopted, the doping concentration is gradually increased from bottom to top, and compared with the traditional gallium oxide pn diode, the p-type semiconductor diode has the following advantages:
first, a p-type semiconductor material with a higher doping concentration in the p-type semiconductor layer can form excellent ohmic contact after contacting with the anode metal on the p-type semiconductor layer, thereby reducing the on-resistance of the device.
Secondly, after the p-type semiconductor material with lower doping concentration in the p-type semiconductor layer is contacted with the gallium oxide drift layer at the lower part of the p-type semiconductor layer, the peak electric field of the drift layer can be inhibited, and the reverse breakdown voltage of the device is improved.
The actual test result shows that the reverse breakdown voltage of the device can be improved and the on-resistance of the device can be reduced, compared with the traditional gallium oxide pn diode, the reverse breakdown voltage of the pn diode is improved by 670V, and the characteristic on-resistance is reduced by 0.2m omega cm 2 。
Drawings
FIG. 1 is a schematic diagram of a gallium oxide pn diode according to a prior art arrangement;
FIG. 2 is a schematic structural diagram of a gallium oxide pn diode with a longitudinally graded p-type doping concentration structure according to the present invention;
FIG. 3 is a flow chart of an implementation of the present invention to fabricate a gallium oxide pn diode with the structure of FIG. 2 having a longitudinally graded p-type doping concentration;
FIG. 4 is a comparison of reverse breakdown voltage curves of a gallium oxide pn diode with a longitudinally graded p-type doping concentration structure of the present invention and a conventional pn diode.
Detailed Description
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the present invention will be further described with reference to the embodiments and the accompanying drawings used in the technical description of the present invention. 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 pn diode with a longitudinally graded p-type doping concentration structure of the invention comprises: cathode ohmic metal 1, gallium oxide substrate 2, gallium oxide drift layer 3, p-type semiconductor layer 4 with longitudinal gradient doping concentration and anode metal 5. Wherein:
the cathode ohmic metal 1 is positioned on the back of the gallium oxide substrate 2, the metal is Ti/Au, the thickness of Ti is 20nm, and the thickness of Au is 400 nm;
the thickness of the gallium oxide substrate 2 is 650 μm, and the doping concentration thereof is 2 × 10 19 cm-3；
The gallium oxide drift layer 3 is located on the gallium oxide substrate 2 and has a thickness10 μm with a doping concentration of 10 16 cm-3；
The p-type semiconductor layer 4 with the longitudinally gradually-changed doping concentration is positioned above the gallium oxide drift layer 3, a plurality of layers of NiO materials with different doping concentrations are adopted, for example, a three-layer structure NiO material can be adopted, the thickness of the lower layer is 11nm, and the doping concentration is 1 multiplied by 10 18 cm-3, the thickness of the middle layer is 7nm, and the doping concentration is 5 multiplied by 10 18 cm-3, an upper layer with a thickness of 4nm and a doping concentration of 1 × 10 19 cm- 3 ；
The anode metal 5 is positioned on the p-type semiconductor layer 4 with the longitudinal gradient doping concentration, the metal is Ni/Au, the thickness of Ni is 45nm, and the thickness of Au is 400 nm.
Referring to fig. 3, the method of making the device structure of fig. 2 of the present invention provides the following three embodiments:
the first embodiment is as follows: and manufacturing the gallium oxide pn diode containing the p-type semiconductor layer with the longitudinally graded doping concentration, which is composed of three layers of NiO materials with different doping concentrations.
The method comprises the following steps: and cleaning the gallium oxide substrate.
The thickness is 650 mu m, and the effective doping carrier concentration is 10 18 cm-3, a gallium oxide substrate 2 doped with Sn ions;
the mixture was sonicated for 5 minutes in sequence with acetone-isopropanol-deionized water, respectively, and then blown dry with nitrogen.
Step two: and growing a gallium oxide drift layer on the front surface of the cleaned gallium oxide substrate by adopting a Hydride Vapor Phase Epitaxy (HVPE) method.
Firstly, HCl reacts with high-purity metal Ga at the temperature of 850 ℃ to generate GaCl and GaCl 3 ；
Then, GaCl and GaCl are added 3 Reacting with oxygen at 500 deg.C to form a doped carrier with a thickness of 10 μm and a doping carrier concentration of 2 × 10 on the front surface of the gallium oxide substrate 2 16 cm-3 gallium oxide drift layer 3.
And step three, 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 20nm, and the thickness of a second layer of Au metal is 400nm, so as to form cathode ohmic metal 1.
Step four: and annealing the cathode ohmic metal in a nitrogen atmosphere by using an annealing furnace at 470 ℃ for 1 minute.
Step five: and depositing a p-type semiconductor layer 4 with the longitudinal gradient doping concentration on the gallium oxide drift layer 3 by magnetron sputtering.
Firstly, a pattern is prepared on a gallium oxide drift layer 3 by utilizing photoetching technology and using photoresist;
then, a first layer having a doping concentration of 1X 10 was formed on the gallium oxide drift layer 3 by magnetron sputtering according to the photolithographic pattern under the conditions of a power of 150W, a ratio of oxygen to argon of 33%, a pressure of 10mtorr, an ambient temperature of 25 ℃ and a processing time of 60 minutes 18 cm-3 of NiO material;
and forming a second layer with doping concentration of 5 multiplied by 10 on the first layer of NiO material by magnetron sputtering under the conditions that the power is 100W, the ratio of oxygen to argon is 40%, the pressure is 10mtorr, the ambient temperature is 25 ℃ and the processing time is 30 minutes 18 cm-3 of NiO material;
then, by magnetron sputtering, under the conditions of 100W of power, 50 percent of oxygen to argon, 10mtorr of pressure, 25 ℃ of ambient temperature and 30 minutes of processing time, a third layer with the doping concentration of 1 × 10 is formed on the second layer of NiO material 19 cm-3 of NiO material;
and finally, removing NiO material deposited on the non-photoetching-pattern position on the gallium oxide drift layer 3 by adopting an N-methyl pyrrolidone solution or an acetone organic solution.
Step six: the anode metal 5 is prepared.
Firstly, preparing an anode pattern on a p-type semiconductor layer 4 with longitudinally gradually-changed doping concentration by using photoresist by utilizing a photoetching technology;
then, 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 finally, washing off the photoresist by using an N-methyl pyrrolidone solution and stripping, namely removing the metal material deposited on the p-type semiconductor layer 4 without the photoetching pattern to finish the manufacture of the device.
Example two: and manufacturing the gallium oxide pn diode containing the p-type semiconductor layer with the longitudinally graded doping concentration, which is composed of four layers of NiO materials with different doping concentrations.
Step 1: and cleaning the gallium oxide substrate.
The thickness is 450 μm, and the effective doping carrier concentration is 10 18 cm-3, and the gallium oxide substrate 2 doped with Sn ions as the ion species is subjected to ultrasonic treatment for 5 minutes by using acetone-isopropanol-deionized water respectively, and then is subjected to blow-drying by using nitrogen.
Step 2: and growing a gallium oxide drift layer on the front surface of the cleaned gallium oxide substrate by adopting a Hydride Vapor Phase Epitaxy (HVPE) method.
2.1) reacting HCl with highly pure metallic Ga at 850 ℃ in a high-temperature reaction zone of an HVPE vertical reactor to form GaCl and GaCl 3 ；
2.2) reacting the GaCl and GaCl produced 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 placing GaCl and GaCl on gallium oxide substrate 2 3 Reacting with oxygen at 600 deg.C to obtain a product with thickness of 4 μm and doping concentration of 1 × 10 16 A cm-3 gallium oxide drift layer 3.
And step 3: and preparing cathode ohmic metal.
And depositing metal Ti/Au on the back surface of the gallium oxide substrate 2 by adopting magnetron sputtering, wherein the thickness of the first layer of metal Ti close to the gallium oxide substrate is 20nm, and the thickness of the second layer of metal Au is 400nm, so as to form cathode ohmic metal 1.
And 4, step 4: the cathode ohmic metal was annealed at 470 deg.c for 1 minute under a nitrogen atmosphere using an annealing furnace.
And 5: and depositing a p-type semiconductor layer with the longitudinal gradient doping concentration by magnetron sputtering.
5.1) preparing a pattern on the gallium oxide drift layer 3 by using a photoetching technology and using a photoresist;
5.2) forming a first layer on the gallium oxide drift layer 3 by magnetron sputtering according to the photolithographic pattern, under the conditions of 150W of power, 33% of oxygen to argon, 10mtorr of pressure, 25 ℃ of ambient temperature and 60 minutes of processing time, the doping concentration of the first layer is 1 x 10 18 cm-3 of NiO material;
5.3) forming a second layer with the doping concentration of 5 multiplied by 10 on the first layer of NiO material by magnetron sputtering under the conditions that the power is 100W, the ratio of oxygen to argon is 40%, the pressure is 10mtorr, the ambient temperature is 25 ℃, and the processing time is 40 minutes 18 cm-3 of NiO material;
5.4) forming a third layer with the doping concentration of 8 multiplied by 10 on the second layer of NiO material by magnetron sputtering under the conditions that the power is 100W, the oxygen to argon ratio is 45 percent, the pressure is 10mtorr, the ambient temperature is 25 ℃ and the processing time is 30 minutes 18 cm-3 of NiO material;
5.5) forming a fourth layer with the doping concentration of 1 multiplied by 10 on the third layer of NiO material by magnetron sputtering under the conditions that the power is 100W, the ratio of oxygen to argon is 50 percent, the pressure is 10mtorr, the ambient temperature is 25 ℃, and the processing time is 30 minutes 19 cm-3 of NiO material;
5.6) placing the gallium oxide drift layer 3 deposited with four layers of NiO materials with different doping concentrations in a beaker containing N-methyl pyrrolidone solution for standing for four hours, and then placing the beaker in an ultrasonic machine for three minutes to remove the NiO material deposited on the position without photoetching patterns on the gallium oxide drift layer 3.
Step 6: and preparing anode metal.
6.1) preparing an anode pattern on the p-type semiconductor layer 4 with the longitudinal gradient doping concentration by using a photoresist by utilizing a photoetching technology; 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 200 nm;
6.2) washing away the photoresist by acetone and stripping off the metal material deposited on the non-photoetching pattern position to finish the preparation of the device.
Example three: and manufacturing the gallium oxide pn diode containing the p-type semiconductor layer with the longitudinally graded doping concentration, which is composed of five layers of NiO materials with different doping concentrations.
Step A, cleaning the gallium oxide substrate.
A1) The thickness is 300 μm, and the effective doping carrier concentration is 10 19 cm-3, a gallium oxide substrate doped with Sn ions;
A2) the mixture was sonicated using acetone-isopropanol-deionized water for 5 minutes in each sonication, and then blown dry using nitrogen.
And B, growing a gallium oxide drift layer on the front side of the cleaned gallium oxide substrate by adopting a Hydride Vapor Phase Epitaxy (HVPE) technology.
B1) 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 ；
B2) Reacting GaCl and GaCl produced in the high temperature reaction zone 3 Pushing into a low-temperature reaction zone;
B3) placing gallium oxide substrate 2 in HVPE vertical reactor low-temperature reaction zone with its front side facing upwards, and placing GaCl and GaCl on gallium oxide substrate 2 3 Reacting with oxygen at 650 deg.C to form a gallium oxide drift layer 3 with a thickness of 4 μm and a doping concentration of 1 × 10 16 cm- 3 。
And step C, preparing cathode ohmic metal.
And depositing metal Ti/Au on the back surface of the gallium oxide substrate 2 by adopting a magnetron sputtering method, wherein the thickness of the first layer of metal Ti close to the gallium oxide substrate 2 is 20nm, and the thickness of the second layer of metal Au is 400nm, so as to form cathode ohmic metal 1.
And D, using an annealing furnace, setting the annealing temperature to be 500 ℃ under the nitrogen atmosphere, and annealing the cathode ohmic metal for 1 minute.
And E, depositing the p-type semiconductor layer 4 with the longitudinal gradient doping concentration by magnetron sputtering.
E1) Preparing a pattern on the gallium oxide drift layer by using a photoresist by utilizing a photoetching technology;
E2) magnetron sputtering on the gallium oxide drift layer 3 according to the photolithographic pattern at a power of 150W and with oxygen to argonThe percentage is 10%, the pressure is 10mtorr, the ambient temperature is 25 ℃, and the processing time is 60 minutes, so that the doping concentration of the first layer is 1 multiplied by 10 17 cm-3 of NiO material;
E3) forming a second layer with doping concentration of 1 × 10 on the first layer of NiO material by magnetron sputtering under the conditions of 150W of power, 33 percent of oxygen to argon, 10mtorr of pressure, 25 ℃ of ambient temperature and 60 minutes of processing time 18 cm-3 of NiO material;
E4) forming a third layer with the doping concentration of 5 multiplied by 10 on the second layer of NiO material by utilizing magnetron sputtering under the conditions of 100W of power, 40 percent of oxygen to argon, 10mtorr of pressure, 25 ℃ of ambient temperature and 40 minutes of processing time 18 cm-3 of NiO material;
E5) forming a fourth layer with the doping concentration of 8 multiplied by 10 on the third layer of NiO material by utilizing magnetron sputtering under the conditions of 100W of power, 45 percent of oxygen to argon, 10mtorr of pressure, 25 ℃ of ambient temperature and 30 minutes of processing time 18 cm-3 of NiO material;
E6) forming a fifth layer with the doping concentration of 1 multiplied by 10 on the fourth layer of NiO material by utilizing magnetron sputtering under the conditions that the power is 100W, the ratio of oxygen to argon is 50 percent, the pressure is 10mtorr, the ambient temperature is 25 ℃, and the processing time is 30 minutes 19 cm-3 of NiO material;
E7) and placing the gallium oxide drift layer 3 deposited with five layers of NiO materials with different doping concentrations in a beaker containing N-methylpyrrolidone solution for standing for six hours, and placing the beaker in an ultrasonic machine for ultrasonic treatment for five minutes to remove the NiO material deposited on the position without the photoetching pattern on the gallium oxide drift layer 3.
And F, preparing anode metal.
Preparing an anode pattern on the p-type semiconductor layer 4 with the longitudinal gradient p-type doping concentration by using photoresist by using a photoetching technology, and depositing anode metal Ni/Au on the anode pattern by adopting electron beam evaporation, 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 finally, washing off the photoresist by adopting an N-methyl pyrrolidone solution and stripping the metal material deposited on the position without the photoetching pattern to finish the preparation of the device.
The effect of the present invention can be further illustrated by the following experimental results:
at room temperature, the conventional pn diode and the pn diode prepared based on example 1 of the present invention were tested by an Agilent B1505 testing instrument to obtain the reverse breakdown curve of the diode, and the result is shown in fig. 4, and the reverse voltage corresponding to a current density of 4mA was taken as the breakdown voltage of the diode.
As can be seen from FIG. 4, the breakdown voltage of the conventional gallium oxide pn diode is-1220V, and the breakdown voltage of the device prepared by the invention is-1890V, which is improved by 55% compared with the breakdown voltage of the conventional pn diode. Meanwhile, the characteristic on-resistance of the conventional gallium oxide pn diode is 3.5m Ω · cm 2 The characteristic on-resistance of the device prepared by the invention is 3.3m omega cm 2 Compared with the conventional pn diode, the characteristic on-resistance is reduced by 5%. The preparation method can effectively improve the reverse breakdown voltage of the gallium oxide pn diode, reduce the characteristic on-resistance and further improve the Baligold optimum value BFOM of the gallium oxide device.
The foregoing description is only three specific examples of the present invention and should not be construed as limiting the 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 structures of the present invention, for example, the number of layers of a p-type semiconductor layer with a longitudinally graded p-type doping concentration is not limited to the number of layers in the three examples of the present invention, and further layers can be deposited; the preparation method of the p-type semiconductor is not limited to magnetron sputtering, and any method such as a metal organic compound chemical vapor deposition process and the like can be used; the preparation method of the anode 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; the cathode ohmic metal preparation method is not limited to magnetron sputtering, and any one of electron beam evaporation or thermal evaporation can be used, but such modifications and changes based on the idea of the present invention are still within the protection scope of the claims of the present invention.
Claims (10)
1. A gallium oxide pn diode with a longitudinal gradient p-type doping concentration structure comprises the following components from bottom to top: cathode ohmic metal (1), gallium oxide substrate (2), gallium oxide drift layer (3), p type semiconductor layer (4) and anode metal (5), characterized in that, p type semiconductor layer (4) adopt the p type semiconductor layer of vertical gradual change doping concentration to reduce device on-resistance when promoting device reverse breakdown voltage, improve the barying of gallium oxide device and add the optimal value.
2. The diode of claim 1, wherein the p-type graded doping concentration ranges from 1 x 10 16 cm -3 Gradation to 1X 10 20 cm -3 。
3. The diode according to claim 1, characterized in that the p-type semiconductor layer (4) has a longitudinal graded doping concentration, and is formed by depositing at least three layers of p-type semiconductor materials with different p-type doping concentrations on the gallium oxide drift layer (3) in sequence from low to high, and the thickness of the p-type semiconductor material of each layer is 3-15 nm.
4. The diode of claim 1, wherein the metal of the cathode ohmic metal (1) is Ti/Au, and the thickness of the first layer of Ti near the gallium oxide substrate layer is 20-50nm, and the thickness of the second layer of Au metal is 100-400 nm.
5. The diode according to claim 1, wherein 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 ions or Sn ions.
6. Diode according to claim 1, characterized in that the gallium oxide drift layer (3) has a thickness of 3-15 μm and a concentration of 10 doping carriers 16 -10 18 cm -3 。
7. Diode according to claim 3, characterized in that the optional p-type semiconductor material in the p-type semiconductor layer (4) comprises nickel oxide, copper oxide and tin oxide.
8. The diode according to claim 1, wherein the anode metal (5) 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 200-400 nm.
9. A method for manufacturing a gallium oxide pn diode with a longitudinally graded p-type doping concentration structure is characterized by comprising the following steps:
1) sequentially cleaning the gallium oxide substrate (2) by acetone-isopropanol-deionized water;
2) performing epitaxial light-doped gallium oxide layer (3) on the front surface of the cleaned gallium oxide substrate (2) by using 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, and performing ohmic annealing on the ohmic cathode metal (1);
3) depositing a p-type semiconductor layer (4) of a longitudinally graded doping concentration on the gallium oxide drift layer (3)
3a) Forming a pattern on the front surface of the gallium oxide drift layer (3) by adopting a photoetching process;
3b) setting magnetron sputtering process conditions: the power is 100-150W, the proportion of oxygen to argon is 5-50%, the processing time is 10-90 minutes, the pressure is 4-10mtorr, and the ambient temperature is 25 ℃;
3c) depositing a p-type semiconductor material with longitudinal gradient doping concentration by magnetron sputtering according to the pattern, namely gradually increasing the proportion of oxygen to argon in the magnetron sputtering process to ensure that the newly deposited p-type doping concentration of each layer is higher than that of the semiconductor material deposited at the previous time, controlling the growth rate of each layer of p-type semiconductor material by controlling the magnetron sputtering power, controlling the doping concentration of each layer of p-type semiconductor material by controlling the proportion of oxygen to argon, controlling the thickness of each layer of p-type semiconductor material by controlling the magnetron sputtering time, and forming a longitudinal gradient p-type semiconductor layer (4) with doping concentration from low to high through multiple depositions;
4) and forming an anode pattern on the front surface of the p-type semiconductor layer (4) with the longitudinal gradient doping concentration by adopting a photoetching process, and depositing and stripping anode metal (5) by adopting electron beam evaporation according to the anode pattern to finish the manufacture of the device.
10. The method as claimed in claim 9, wherein the annealing of the ohmic cathode metal in step 2) is performed in a nitrogen atmosphere at an annealing temperature of 400-500 ℃ for 1-3 minutes.
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