High breakdown voltage Schottky diode and preparation method thereof

Abstract

The invention belongs to the field of diode devices, and discloses a high-breakdown-voltage Schottky diode and a preparation method thereof. The Schottky diode comprises a substrate, an AlN layer, a GaN layer and an AlGaN layer which are sequentially stacked from bottom to top, a p-AlGaN layer and an Al2O3 layer are arranged on the AlGaN layer; the p-AlGaN layer is in contact with the Al2O3 layer, and the p-AlGaN layer and the Al2O3 layer partially cover the AlGaN layer; the diode further comprises a cathode and an anode. The cathode is arranged on the AlGaN layer and is close to one end of the Al2O3 layer; and the anode is arranged on the AlGaN layer which is not covered by the p-AlGaN layer and the Al2O3 layer and is close to the p-AlGaN layer and the p-AlGaN layer. The invention also discloses a preparation method of the Schottky diode. The p-AlGaN layer can relieve the electric field crowding phenomenon of the Schottky contact area, and therefore the breakdown voltage of the chip is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of diode devices, and specifically relates to a method for preparing a high breakdown voltage Schottky diode. Background Technology

[0002] In the evolution of electronic component technology, high-frequency, high-precision frequency components and discrete semiconductor devices and modules with characteristics such as high temperature and high pressure resistance, low loss, and high reliability are becoming the main technological focus for circuit components. These components have broad application prospects, not only driving breakthroughs in basic electronic component technology but also placing higher demands on the supply chain capabilities of the materials and equipment used. This development trend provides significant opportunities for the development of third-generation semiconductor power and radio frequency devices.

[0003] Gallium nitride (GaN), a typical representative of third-generation wide-bandgap semiconductor materials, has attracted much attention due to its excellent performance. It possesses extremely high critical breakdown field strength, high electron mobility, high-concentration two-dimensional electron gas, and excellent high-temperature operating capability. GaN has a bandgap of 3.4 eV, significantly higher than silicon (1.1 eV) and gallium arsenide (1.4 eV). Since the intrinsic carrier concentration of semiconductor materials changes exponentially with increasing bandgap and temperature, within a specific temperature range, a larger bandgap results in a lower intrinsic carrier concentration, enabling GaN devices to achieve extremely low leakage current. Furthermore, GaN materials are chemically stable, exhibiting high-temperature resistance and corrosion resistance, making them significantly advantageous in high-frequency, high-power, and radiation-resistant applications.

[0004] Schottky diodes hold a crucial position in the semiconductor field. In recent years, with advancements in process and materials technology, GaN heterojunction-based Schottky diodes have achieved significant development. However, traditional GaN Schottky diodes suffer from low breakdown voltage, which limits their application in high-power scenarios. Summary of the Invention

[0005] To address the issue of low breakdown voltage in conventional GaN Schottky diodes, this invention proposes a high breakdown voltage Schottky diode and its fabrication method. The invention involves growing an AlN buffer layer on a silicon substrate, followed by fabricating an AlGaN / GaN heterojunction on the buffer layer. A p-AlGaN layer is then deposited above the AlGaN layer, and finally, an Al2O3 layer, an ohmic contact electrode, and a Schottky contact electrode are formed. The introduction of the p-AlGaN layer effectively alleviates the electric field concentration phenomenon in the Schottky contact region, thereby significantly improving the breakdown voltage performance.

[0006] The technical solution of the present invention is as follows: A high breakdown voltage Schottky diode includes a substrate, an AlN layer, a GaN layer, and an AlGaN layer stacked sequentially from bottom to top. The AlGaN layer is provided with a p-AlGaN layer and an Al2O3 layer; the p-AlGaN layer and the Al2O3 layer are in contact and the p-AlGaN layer and the Al2O3 layer partially cover the AlGaN layer; The diode further includes a cathode and an anode; the cathode is disposed on an AlGaN layer that is not covered by the p-AlGaN layer and the Al2O3 layer and is close to the Al2O3 layer, and the cathode is in contact with the Al2O3 layer; The anode is disposed on an AlGaN layer that is not covered by the p-AlGaN layer and the Al2O3 layer and is close to the p-AlGaN layer, as well as on the p-AlGaN layer. The anode completely covers the p-AlGaN layer.

[0007] The cathode is located at one end of the AlGaN layer that is not covered by the p-AlGaN layer and the Al2O3 layer, and the cathode is in contact with the Al2O3 layer; the anode is located at one end of the AlGaN layer that is not covered by the p-AlGaN layer and the Al2O3 layer, and on the p-AlGaN layer.

[0008] The height of the p-AlGaN layer is less than the height of the Al2O3 layer.

[0009] The height of the anode is the same as the height of the Al2O3 layer. Here, the height of the anode refers to the distance from the upper surface of the AlGaN layer to the upper surface of the anode.

[0010] The height of the Al2O3 layer is the same as the height of the cathode.

[0011] The cathode is a first metal that forms an ohmic contact; the anode is a second metal that forms a Schottky contact metal.

[0012] The substrate is made of one of the following materials: silicon, sapphire, silicon carbide, and GaN.

[0013] The thickness of the AlN layer is 1~2μm, the thickness of the AlGaN layer is 20~30nm, the thickness of the GaN layer is 2~4μm, and the thickness of the Al2O3 layer is 30~35nm.

[0014] The p-AlGaN layer has a length of 8~10 μm and a thickness of 15~25 nm.

[0015] The cathode, i.e., the ohmic contact metal electrode, is one or more of Cr, Ti, Al, Ni, Au, Ag, and Pt.

[0016] The anode, i.e., the Schottky contact metal, is one or both of Ni and Au.

[0017] The cathode, i.e., the ohmic contact metal electrode, has a length of 8~10μm and a thickness of 30~35nm.

[0018] The anode portion on the AlGaN layer has a length of 8~10 μm and a thickness of 30~35 nm; the anode portion on the p-AlGaN layer has a length of 8~10 μm and a thickness of 10~15 nm.

[0019] The length of the Al2O3 layer is 10~15 μm.

[0020] The AlGaN layer is in direct contact with GaN, forming a van der Waals heterojunction.

[0021] The method for fabricating the high breakdown voltage Schottky diode includes the following steps: (1) An epitaxial wafer was obtained by epitaxially growing AlN, GaN and AlGaN layers on a substrate using MOCVD method; (2) A p-AlGaN layer is grown on the AlGaN layer by MOCVD, and the p-AlGaN layer partially covers the AlGaN layer; (3) An Al2O3 layer is deposited on the AlGaN layer by electron beam evaporation, wherein the Al2O3 layer is in contact with the p-AlGaN layer and the Al2O3 layer partially covers the AlGaN layer; (4) An ohmic contact is deposited on the AlGaN layer and near the Al2O3 layer by electron beam evaporation as a cathode, and then annealed; (5) A Schottky contact is prepared on the AlGaN layer and near one end of the p-AlGaN layer by photolithography and electron beam evaporation to serve as the anode.

[0022] The annealing conditions are as follows: annealing at 845~855 ℃ for 25~35 s in a N2 atmosphere.

[0023] The beneficial effects of this invention are as follows: This invention proposes a high breakdown voltage Schottky diode. Compared with traditional GaN Schottky diodes, the introduction of a p-AlGaN layer effectively alleviates the electric field congestion phenomenon in the Schottky contact region, thereby significantly improving the breakdown voltage of the chip. The growth of the p-AlGaN layer has good compatibility with the growth of the underlying AlGaN material, is simple to fabricate, and has a significant effect on improving the breakdown voltage of the Schottky diode, showing great application potential. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the high breakdown voltage Schottky diode structure of the present invention; 1-substrate, 2-AlN layer, 3-GaN layer, 4-AlGaN layer, 5-p-AlGaN layer, 6-Al2O3 layer, 7-cathode, 8-anode; Figure 2This is a process flow diagram for fabricating the high breakdown voltage Schottky diode of the present invention; Figure 3 This is a schematic diagram of a conventional GaN Schottky diode structure; 1-substrate, 2-AlN layer, 3-GaN layer, 4-AlGaN layer, 5-Al2O3 layer, 6-cathode, 7-anode. Detailed Implementation

[0025] The specific embodiments of the present invention will be further described below with reference to the examples and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] A schematic diagram of the high breakdown voltage Schottky diode structure of the present invention is shown below. Figure 1 As shown, from bottom to top, it includes a substrate 1, an AlN layer 2, a GaN layer 3, and an AlGaN layer 4 stacked sequentially. The AlGaN layer 4 is provided with a p-AlGaN layer 5 and an Al2O3 layer 6; the p-AlGaN layer 5 and the Al2O3 layer 6 are in contact and the p-AlGaN layer 5 and the Al2O3 layer 6 partially cover the AlGaN layer 4. The diode also includes a cathode 7 and an anode 8; the cathode 7 is disposed on an AlGaN layer 4 that is not covered by the p-AlGaN layer 5 and the Al2O3 layer 6 and is close to the Al2O3 layer 6, and the cathode 7 is in contact with the Al2O3 layer 6; The anode 8 is disposed on the AlGaN layer 4, which is not covered by the p-AlGaN layer 5 and the Al2O3 layer 6, and is close to the p-AlGaN layer 5, as well as on the p-AlGaN layer 5.

[0027] The cathode 7 is located at one end of the AlGaN layer 4 that is not covered by the p-AlGaN layer 5 and the Al2O3 layer 6, and the cathode 7 is in contact with the Al2O3 layer 6; the anode 8 is located at one end of the AlGaN layer 4 that is not covered by the p-AlGaN layer 5 and the Al2O3 layer 6, and on the p-AlGaN layer 5.

[0028] The height of the p-AlGaN layer 5 is less than the height of the Al2O3 layer 6.

[0029] The height of the anode 8 is the same as the height of the Al2O3 layer 6. Here, the height of the anode refers to the distance from the upper surface of the AlGaN layer to the upper surface of the anode.

[0030] The height of Al2O3 layer 6 is the same as the height of cathode 7.

[0031] The cathode 7 is a first metal that forms an ohmic contact; the anode 8 is a second metal that forms a Schottky contact metal.

[0032] The substrate is made of one of the following materials: silicon, sapphire, silicon carbide, and GaN.

[0033] The thickness of the AlN layer is 1~2μm, the thickness of the AlGaN layer is 20~30nm, the thickness of the GaN layer is 2~4μm, and the thickness of the Al2O3 layer is 30~35nm.

[0034] The p-AlGaN layer has a length of 8~10 μm and a thickness of 15~25 nm.

[0035] The cathode, i.e., the ohmic contact metal electrode, is one or more of Cr, Ti, Al, Ni, Au, Ag, and Pt.

[0036] The anode, i.e., the Schottky contact metal, is one or both of Ni and Au.

[0037] The cathode, i.e., the ohmic contact metal electrode, has a length of 8~10μm and a thickness of 30~35nm.

[0038] The anode portion on the AlGaN layer has a length of 8~10 μm and a thickness of 30~35 nm; the anode portion on the p-AlGaN layer has a length of 8~10 μm and a thickness of 10~15 nm.

[0039] The length of the Al2O3 layer is 10~15 μm.

[0040] The fabrication process flow diagram of the high breakdown voltage Schottky diode of the present invention is shown below. Figure 2 As shown.

[0041] Example 1 This embodiment describes a method for fabricating a high breakdown voltage Schottky diode: (1) Take an epitaxial high-resistivity silicon substrate with a thickness of 500 μm, and grow an AlN layer, a GaN layer and an AlGaN layer on the epitaxial high-resistivity substrate using an MOCVD device to obtain an epitaxial wafer. The thickness of the AlN layer is 1 μm, the thickness of the GaN layer is 2 μm and the thickness of the AlGaN layer is 25 nm. (2) A layer of p-AlGaN with a length of 8 μm and a thickness of 20 nm was grown on the AlGaN layer by MOCVD.

[0042] (3) An Al2O3 layer is deposited on the AlGaN layer by electron beam evaporation; the Al2O3 layer has a thickness of 35 nm and a length of 15 μm; the Al2O3 layer is in contact with p-AlGaN; (4) An ohmic contact was deposited on one end of the AlGaN layer near the Al2O3 layer by electron beam evaporation. The structure was a 3nm Ti / 6nm Al / 6nm Ni / 20nm Au multi-metal layer. Then, the ohmic contact was prepared by annealing at 850 °C for 30 s in N2 atmosphere. The length of the ohmic contact was 9 μm and the thickness was 35 nm. (5) A Schottky contact was prepared on the AlGaN layer near the p-AlGaN layer by photolithography and electron beam evaporation. The left part (the anode part on the AlGaN layer) is 8 nm Ni / 27 nm Au, with a length of 9 μm and a thickness of 35 nm. The right part (the anode part on the p-AlGaN layer) has a structure of 4 nm Ni / 11 nm Au, with a length of 8 μm and a thickness of 15 nm.

[0043] Example 2 The differences between this embodiment and Embodiment 1 are as follows: (5) A Schottky contact was prepared on the AlGaN layer near the p-AlGaN layer by photolithography and electron beam evaporation. The left part (the anode part on the AlGaN layer) is 9 nm Ni / 26 nm Au, with a length of 9 μm and a thickness of 35 nm. The right part (the anode part on the p-AlGaN layer) has a structure of 3 nm Ni / 12 nm Au, with a length of 8 μm and a thickness of 15 nm.

[0044] Example 3 The differences between this embodiment and Embodiment 1 are as follows: (5) A Schottky contact was prepared on the AlGaN layer near the p-AlGaN layer by photolithography and electron beam evaporation. The left part (the anode part on the AlGaN layer) is 10 nm Ni / 25 nm Au with a length of 9 μm and a thickness of 35 nm. The right part (the anode part on the p-AlGaN layer) has a structure of 6 nm Ni / 9 nm Au with a length of 8 μm and a thickness of 15 nm.

[0045] Figure 3 This is a schematic diagram of a conventional AlGaN / GaN SBD Schottky diode structure. From bottom to top, it includes a substrate 1, an AlN layer 2, a GaN layer 3, and an AlGaN layer 4 stacked sequentially. An Al2O3 layer 5 is disposed on the AlGaN layer 4, located in the middle of the upper surface of the AlGaN layer 4. An anode 7 is located at one end of the AlGaN layer 4 not covered by the Al2O3 layer, and a cathode 6 is located at the other end of the AlGaN layer 4 not covered by the Al2O3 layer. The anode 7 is in contact with the Al2O3 layer 5, and the cathode 6 is in contact with the Al2O3 layer 5; the anode 7 and the cathode 6 are not in contact.

[0046] This invention proposes a high breakdown voltage Schottky diode. Compared to traditional SBD Schottky diodes, this invention's high breakdown voltage Schottky diode, through the introduction of a p-AlGaN layer, effectively alleviates the electric field congestion phenomenon in the Schottky contact region, thereby significantly improving the chip's breakdown voltage. The growth of the p-AlGaN layer has good compatibility with the growth of the underlying AlGaN material, is simple to fabricate, and significantly improves the breakdown voltage of the Schottky diode, showing great application potential.

[0047] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A high breakdown voltage Schottky diode, characterized in that: It includes a substrate, an AlN layer, a GaN layer, and an AlGaN layer stacked sequentially from bottom to top; The AlGaN layer is provided with a p-AlGaN layer and an Al2O3 layer; the p-AlGaN layer and the Al2O3 layer are in contact and the p-AlGaN layer and the Al2O3 layer partially cover the AlGaN layer; The diode further includes a cathode and an anode; the cathode is disposed on an AlGaN layer that is not covered by the p-AlGaN layer and the Al2O3 layer and is close to the Al2O3 layer, and the cathode is in contact with the Al2O3 layer; The anode is disposed on an AlGaN layer and on the p-AlGaN layer that are not covered by the p-AlGaN layer and the Al2O3 layer and are close to the p-AlGaN layer.

2. The high breakdown voltage Schottky diode according to claim 1, characterized in that: The cathode is located at one end of the AlGaN layer that is not covered by the p-AlGaN layer and the Al2O3 layer, and the cathode is in contact with the Al2O3 layer; the anode is located at one end of the AlGaN layer that is not covered by the p-AlGaN layer and the Al2O3 layer, and on the p-AlGaN layer.

3. The high breakdown voltage Schottky diode according to claim 1, characterized in that: The height of the p-AlGaN layer is less than the height of the Al2O3 layer; The height of the anode is the same as the height of the Al2O3 layer; here, the height of the anode refers to the distance from the upper surface of the AlGaN layer to the upper surface of the anode. The height of the Al2O3 layer is the same as the height of the cathode.

4. The high breakdown voltage Schottky diode according to claim 1, characterized in that: The cathode is a first metal that forms an ohmic contact; the anode is a second metal that forms a Schottky contact metal. The substrate is made of one of silicon, sapphire, silicon carbide and GaN. The cathode, i.e., the ohmic contact metal electrode, is one or more of Cr, Ti, Al, Ni, Au, Ag, and Pt; The anode, i.e., the Schottky contact metal, is one or both of Ni and Au.

5. The high breakdown voltage Schottky diode according to claim 1, characterized in that: The thickness of the AlN layer is 1~2μm, the thickness of the AlGaN layer is 20~30nm, the thickness of the GaN layer is 2~4μm, and the thickness of the Al2O3 layer is 30~35nm; The p-AlGaN layer has a length of 8~10 μm and a thickness of 15~25 nm; The cathode, i.e., the ohmic contact metal electrode, has a length of 8~10μm and a thickness of 30~35nm; The anode portion on the AlGaN layer has a length of 8~10 μm and a thickness of 30~35 nm; the anode portion on the p-AlGaN layer has a length of 8~10 μm and a thickness of 10~15 nm. The length of the Al2O3 layer is 10~15 μm.

6. The method for fabricating a high breakdown voltage Schottky diode according to claim 1, characterized in that: Includes the following steps: (1) An epitaxial wafer was obtained by epitaxially growing AlN, GaN and AlGaN layers on a substrate using MOCVD method; (2) A p-AlGaN layer is grown on the AlGaN layer by MOCVD, and the p-AlGaN layer partially covers the AlGaN layer; (3) An Al2O3 layer is deposited on the AlGaN layer by electron beam evaporation, wherein the Al2O3 layer is in contact with the p-AlGaN layer and the Al2O3 layer partially covers the AlGaN layer; (4) An ohmic contact is deposited on the AlGaN layer and near the Al2O3 layer by electron beam evaporation as a cathode, and then annealed. (5) A Schottky contact is prepared on the AlGaN layer and near one end of the p-AlGaN layer by photolithography and electron beam evaporation to serve as the anode.

7. The method for fabricating a high breakdown voltage Schottky diode according to claim 6, characterized in that: The annealing conditions are as follows: annealing at 845~855 ℃ for 25~35 s in a N2 atmosphere.

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