Preparation method of a low-cost nickel oxide / gallium oxide heterojunction power diode with a controllable tilt angle inclined table

Abstract

The present invention discloses a preparation method of a nickel oxide / gallium oxide heterojunction power diode with a low cost and a controllable inclination angle of the inclined tabletop. By magnetron sputtering nickel oxide through the hollowed-out part of a hard mask, a top-down nickel oxide / gallium oxide heterojunction PN structure can be obtained; by adjusting the incident angle between the nickel oxide target for magnetron sputtering and the gallium oxide wafer, an inclined nickel oxide tabletop with an inclined angle can be obtained, and the tabletop inclination angle is positively correlated with the incident angle. Compared with the method of lithographically preparing a nickel oxide pattern, the process of preparing a nickel oxide pattern using a hard mask is simple and low in cost, and the inclination angle of the inclined nickel oxide tabletop can be freely controlled. At the same time, the design of the inclined tabletop increases the breakdown voltage of the device, which is of great significance for the large-scale application of high-voltage withstand and high-current gallium oxide power devices.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor power device manufacturing, and particularly to a method for preparing a low-cost, controllable inclination angle inclined mesa nickel oxide / gallium oxide heterojunction power diode. Background Art

[0002] Ultra-wide bandgap semiconductor gallium oxide (Ga2O3) has a large bandgap (4.5 - 4.9 eV), a high critical breakdown field strength (8 MV / cm), a large substrate size, low production cost, and controllable epitaxial doping. Therefore, it has broad prospects in the field of ultra-high voltage power electronic devices, especially in important applications in civil and military fields such as ultra-high voltage power transmission, industrial control, new energy electric vehicles, weaponry, and aerospace.

[0003] However, gallium oxide also faces many technical challenges. There is a key bottleneck problem of difficult p-type doping in gallium oxide, resulting in the inapplicability of traditional bipolar power device designs. Compared with gallium oxide unipolar devices, bipolar devices have advantages such as low reverse leakage current and conductance modulation effect. To achieve the bipolar design of gallium oxide devices, a heterogenous p-type material can be combined with n-type gallium oxide to construct a heterogenous pn junction. Currently, heterogenous pn junction diodes such as nickel oxide / gallium oxide, cuprous oxide / gallium oxide, and stannous oxide / gallium oxide have all been reported and shown excellent electrical properties. Among them, nickel oxide / gallium oxide has been reported the most and shows more excellent comprehensive performance. To further increase the reverse breakdown voltage of the nickel oxide / gallium oxide heterojunction diode and reduce the reverse leakage current, it is necessary to develop a terminal structure to relieve the edge electric field concentration. The inclined mesa terminal technology is an effective terminal structure design, but the traditional inclined mesa process preparation requires complex lithography and etching processes, with high process costs, and it is difficult to effectively control the inclination angle of the inclined mesa. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for preparing a low-cost, controllable inclination angle inclined mesa nickel oxide / gallium oxide heterojunction power diode, which is used to solve the problems of high process cost and difficult effective control of the inclination angle in traditional inclined mesa technology.

[0005] A method for preparing a low-cost, controllable inclination angle inclined mesa nickel oxide / gallium oxide heterojunction power diode includes the following steps:

[0006] S1. Provide a gallium oxide single crystal wafer with a low-doped drift layer of gallium oxide on the front side, make an ohmic contact electrode on the back side and perform rapid thermal annealing treatment;

[0007] S2. Provide a hard mask with a hollow pattern;

[0008] S3. Keep a certain distance between the hard mask and the low-doped drift layer of gallium oxide, and adjust the incident angle of the magnetron sputtering nickel oxide target with respect to the gallium oxide single crystal wafer.

[0009] S4. Magnetron sputter nickel oxide, which grows on the low-doped drift layer of gallium oxide on the front side of the gallium oxide single crystal wafer through the hollowed-out part of the hard mask, to obtain a nickel oxide / gallium oxide heterojunction PN structure from top to bottom; wherein, the edge of the nickel oxide in the nickel oxide / gallium oxide heterojunction PN structure has a mesa with an inclined angle.

[0010] S5. Fabricate an ohmic contact between the anode and the nickel oxide.

[0011] Further, the gallium oxide single crystal wafer described in step S1 includes a low-doped drift layer of gallium oxide and a thinned high-conductivity gallium oxide substrate from top to bottom. The carrier concentration of the thinned high-conductivity gallium oxide substrate is greater than 1×10 18 / cm 3 .

[0012] Further, the hollowed-out pattern of the hard mask described in step S2 includes a circle or a square. The material of the hard mask includes metal, or plastic, or glass, or ceramic, and the thickness of the hard mask is 0.05 mm to 5 mm.

[0013] Further, the distance between the hard mask and the low-doped drift layer of gallium oxide in step S3 is kept between 0 and 0.5 mm.

[0014] Further, the incident angle of the nickel oxide target with respect to the gallium oxide single crystal wafer in step S3 is the angle between the vertical direction of the nickel oxide target and the horizontal direction of the gallium oxide single crystal wafer.

[0015] Further, the incident angle is between 0° and 90°.

[0016] Further, the nickel oxide target in step S3 includes an undoped nickel oxide target with a purity of more than 99.9%, or a lithium-doped nickel oxide target, or a copper-doped nickel oxide target, or a silver-doped nickel oxide target.

[0017] Further, the thickness of the nickel oxide in the nickel oxide / gallium oxide heterojunction PN structure described in step S4 is 20 nm to 2000 nm.

[0018] Further, the inclined angle of the mesa in step S4 is 0° to 90°; the inclined angle of the mesa is positively correlated with the incident angle described in step S3; wherein, the larger the incident angle, the larger the inclined angle of the mesa.

[0019] Further, the magnetron sputtered nickel oxide in step S4 includes the following specific growth conditions: the growth temperature is maintained at 0°C to 250°C, the substrate rotation speed is maintained at 3 to 15 revolutions per minute during the growth process, and the growth atmosphere is a mixed gas of argon and oxygen.

[0020] Further, the anode selected for the preparation in step S5 is made of a metal including nickel, or platinum, or gold.

[0021] Beneficial effects

[0022] By adjusting the incident angle between the magnetron sputtered nickel oxide target and the gallium oxide wafer, a nickel oxide mesa with an inclined angle can be obtained in the present invention, and the mesa inclination angle is positively correlated with the incident angle. Compared with the method of lithographically preparing nickel oxide patterns, the process of preparing nickel oxide patterns using a hard mask is simple and low-cost, and the inclination angle of the nickel oxide inclined mesa can be freely controlled. At the same time, the design of the inclined mesa increases the breakdown voltage of the device, which is of great significance for the large-scale application of high-voltage withstand and high-current gallium oxide power devices, and is used to solve the problems of high process cost and difficult effective control of the inclination angle in the traditional inclined mesa technology. Description of the drawings

[0023] Figure 1 This is an example of the preparation steps of an inclined mesa nickel oxide / gallium oxide heterojunction power diode in an embodiment of the present invention.

[0024] Figure 2 This is an optical top view of the inclined mesa nickel oxide / gallium oxide heterojunction power diode prepared in an embodiment of the present invention.

[0025] Figure 3 This is a cross-sectional SEM image of the inclined mesa at the edge of the inclined mesa nickel oxide / gallium oxide heterojunction power diode prepared in an embodiment of the present invention. Detailed implementation manners

[0026] Hereinafter, the embodiments of the present invention will be further described in detail with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The described embodiments are only for illustration, rather than limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0027] Specifically, Figure 1 It shows a schematic diagram of the preparation process of a low-cost and controllable inclination angle inclined mesa nickel oxide / gallium oxide heterojunction power diode.

[0028] A method for preparing a low-cost and controllable inclination angle inclined mesa nickel oxide / gallium oxide heterojunction power diode includes the following steps:

[0029] S1. Provide a gallium oxide single crystal wafer with a low-doped drift layer 110 of gallium oxide on the front side, make an ohmic contact electrode 200 on the back side and perform rapid thermal annealing treatment to improve the ohmic contact performance;

[0030] The gallium oxide single crystal wafer includes a low-doped drift layer 110 of gallium oxide and a thinned high-conductivity gallium oxide substrate 101 from top to bottom.

[0031] The thinned high-conductivity gallium oxide substrate 101 includes an α-phase gallium oxide, β-phase gallium oxide or κ-phase gallium oxide substrate, and the carrier concentration of the thinned high-conductivity gallium oxide substrate 101 is higher than 1×10 18 / cm 3 . The thickness of the thinned high-conductivity gallium oxide single crystal substrate is 50 μm to 600 μm.

[0032] S2. Provide a hard mask 300 with a hollow pattern; the hollow pattern of the hard mask 300 includes a circle or a square, the material of the hard mask 300 includes metal, or plastic, or glass, or ceramic, and the thickness of the hard mask is 0.05 mm to 5 mm.

[0033] S3. Keep a certain distance between the hard mask 300 and the low-doped drift layer 110 of gallium oxide, and adjust the incident angle of the magnetron sputtering nickel oxide target 500 with respect to the gallium oxide single crystal wafer; the distance between the hard mask 300 and the low-doped drift layer 110 of gallium oxide is between 0 and 0.5 mm.

[0034] The incident angle of the nickel oxide target 500 with respect to the gallium oxide single crystal wafer is between 0° and 90°. The incident angle is the angle between the vertical direction of the nickel oxide target 500 and the horizontal direction of the gallium oxide single crystal wafer.

[0035] The nickel oxide target 500 includes an undoped nickel oxide target with a purity of more than 99.9%, or a lithium-doped nickel oxide target, or a copper-doped nickel oxide target, or a silver-doped nickel oxide target.

[0036] S4. Magnetron sputter nickel oxide 400, which grows on the low-doped drift layer 110 of gallium oxide on the front side of the gallium oxide single crystal wafer through the hollow part of the hard mask 300, to obtain a nickel oxide / gallium oxide heterojunction PN structure including from top to bottom; the thickness of the nickel oxide in the nickel oxide / gallium oxide heterojunction PN structure described in step S4 is 20 nm to 2000 nm.

[0037] Among them, the edge of the nickel oxide 400 in the nickel oxide / gallium oxide heterojunction PN structure has a mesa with an inclined angle; the inclined angle of the mesa is 0° to 90°; the inclined angle of the mesa is positively correlated with the incident angle described in step S3; among them, the larger the incident angle, the larger the inclined angle of the mesa will be.

[0038] The magnetron sputtered nickel oxide 400 includes the following specific growth conditions: the growth temperature is maintained at 0°C to 250°C, the substrate rotation speed is maintained at 3 to 15 revolutions per minute during the growth process, and the growth atmosphere is a mixed gas of argon and oxygen.

[0039] S5. Prepare an anode 600 to form an ohmic contact with the nickel oxide 400, and complete the preparation of the inclined mesa nickel oxide / gallium oxide heterojunction power diode. The metals selected for the prepared anode 600 include nickel, or platinum, or gold.

[0040] Figure 2 This is an optical top view of the inclined mesa nickel oxide / gallium oxide heterojunction power diode prepared in the embodiment of the present invention. It can be clearly seen that due to the inclined mesa of the nickel oxide at the edge of the anode, there are obvious equal-thickness interference fringes under an optical microscope.

[0041] Figure 3 This is a cross-sectional SEM image of the inclined mesa at the edge of the inclined mesa nickel oxide / gallium oxide heterojunction power diode with a 2° tilt angle prepared in the embodiment of the present invention. It can be clearly seen that the nickel oxide has a 2° tilt angle. The size of the tilt angle can be changed by adjusting the incident angle between the nickel oxide target and the gallium oxide wafer.

Claims

1. A preparation method of a nickel oxide / gallium oxide heterojunction power diode with a low cost and a controllable inclination angle inclined tabletop, characterized in that, It includes the following steps: S1. Provide a gallium oxide single crystal wafer with a low-doped drift layer of gallium oxide (110) on the front side, make an ohmic contact electrode (200) on the back side and perform rapid thermal annealing treatment; S2. Provide a hard mask (300) with a hollow pattern; S3. Keep a certain distance between the hard mask (300) and the low-doped drift layer of gallium oxide (110), and adjust the incident angle of the magnetron sputtering nickel oxide target (500) with respect to the gallium oxide single crystal wafer; S4. Magnetron sputter nickel oxide (400), which grows on the low-doped drift layer of gallium oxide (110) on the front side of the gallium oxide single crystal wafer through the hollow part of the hard mask (300) to obtain a nickel oxide / gallium oxide heterojunction PN structure from top to bottom; wherein, the edge of the nickel oxide (400) in the nickel oxide / gallium oxide heterojunction PN structure has a mesa with an inclined angle; S5. Prepare an anode (600) to form an ohmic contact with the nickel oxide (400).

2. The preparation method of the low-cost, controllable tilt angle inclined tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, characterized in that: The gallium oxide single crystal wafer described in step S1 includes a gallium oxide low-doped drift layer (110) and a thinned gallium oxide highly conductive substrate (101) from top to bottom; the carrier concentration of the thinned gallium oxide highly conductive substrate (101) is greater than 1×10 18 / cm 3 .

3. The preparation method of the low-cost, controllable tilt angle inclined tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, characterized in that: The hollow pattern of the hard mask (300) described in step S2 includes a circle or a square, the material of the hard mask (300) includes metal, plastic, glass or ceramic, and the thickness of the hard mask (300) is 0.05 mm to 5 mm.

4. The preparation method of the low-cost, controllable inclination angle inclined tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, characterized in that: The distance between the hard mask (300) and the low-doped drift layer of gallium oxide (110) described in step S3 is between 0 and 0.5 mm.

5. The preparation method of the low-cost and controllable inclination angle inclined tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, characterized in that, The incident angle of the nickel oxide target (500) and the gallium oxide single crystal wafer described in step S3 is the angle between the vertical direction of the nickel oxide target (500) and the horizontal direction of the gallium oxide single crystal wafer, and the incident angle is between 0° and 90°.

6. The preparation method of the low-cost and controllable inclination angle inclined tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, characterized in that, The nickel oxide target (500) described in step S3 includes an undoped nickel oxide target with a purity of more than 99.9%, a lithium-doped nickel oxide target, a copper-doped nickel oxide target or a silver-doped nickel oxide target.

7. The preparation method of the low-cost, controllable-inclination-angle inclined-tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, characterized in that: The thickness of the nickel oxide in the nickel oxide / gallium oxide heterojunction PN structure described in step S4 is 20 nm to 2000 nm.

8. The preparation method of the low-cost, controllable inclination angle inclined tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, characterized in that, The inclined angle of the mesa described in step S4 is 0° to 90°; the inclined angle of the mesa is positively correlated with the incident angle described in step S3; wherein, the larger the incident angle, the larger the inclined angle of the mesa.

9. The preparation method of the low-cost and controllable inclination angle inclined tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, wherein The magnetron sputtering nickel oxide (400) described in step S4 includes the following specific growth conditions: the growth temperature is kept at 0°C to 250°C, the substrate rotation speed is kept at 3 to 15 revolutions per minute during the growth process, and the growth atmosphere is a mixed gas of argon and oxygen.

10. The preparation method of the low-cost and controllable inclination angle inclined tabletop nickel oxide / gallium oxide heterojunction power diode according to claim 1, characterized in that, The anode (600) prepared in step S5 is selected from metals including nickel, or platinum, or gold.

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