A gallium oxide power diode with high breakdown voltage and its manufacturing method

Abstract

The present invention relates to a gallium oxide power diode with a high breakdown voltage and a preparation method thereof. The preparation method includes: selecting a substrate layer, preparing a drift layer on the upper surface of the substrate layer; preparing a cathode on the lower surface of the substrate layer; preparing an anode on the upper surface of the drift layer; performing a low-temperature annealing process on the device to obtain the gallium oxide power diode; wherein, both the substrate layer and the drift layer are Si- or Sn-doped β-Ga2O3 materials, and the doping concentration of the drift layer is lower than that of the substrate layer, the anode is a Ni / Au metal stack, and a NiO layer with P-type characteristics is formed at the interface between the metal Ni and the drift layer, and the NiO layer and the drift layer form a heterojunction PN junction structure. The preparation method of the present invention can form a heterojunction PN junction structure with a P-type characteristic thin layer NiO layer through low-temperature annealing, can modulate the electric field distribution, improve the interface characteristics between the anode metal and gallium oxide, reduce the reverse leakage current, and increase the breakdown voltage of the device.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor devices, and particularly relates to a gallium oxide power diode with a high breakdown voltage and a preparation method thereof. Background Art

[0002] Due to the ultra-wide bandgap width and relatively high breakdown field strength of the β-Ga2O3 crystal material, β-Ga2O3 has the potential to fabricate high-voltage-resistant, high-power, and low-loss power devices and can be applied in the high-voltage and high-power fields. In recent years, many scholars have started to study the β-Ga2O3 crystal material and power devices. However, there is still a large gap between the breakdown field strength of its devices and the theoretical limit. At the same time, the thermionic field emission current (TFE leakage current) is still very large. Summary of the Invention

[0003] In order to solve the above problems existing in the prior art, the present invention provides a gallium oxide power diode with a high breakdown voltage and a preparation method thereof. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0004] The present invention provides a preparation method of a gallium oxide power diode with a high breakdown voltage, including:

[0005] S1: Select a substrate layer, and prepare a drift layer on the upper surface of the substrate layer;

[0006] S2: Prepare a cathode on the lower surface of the substrate layer;

[0007] S3: Prepare an anode on the upper surface of the drift layer;

[0008] S4: Perform a low-temperature annealing process on the device to obtain a gallium oxide power diode;

[0009] Wherein, both the substrate layer and the drift layer are Si- or Sn-doped β-Ga2O3 materials, and the doping concentration of the drift layer is lower than that of the substrate layer. The anode is a Ni / Au metal stack, and a NiO layer with P-type characteristics is formed at the interface between the metal Ni and the drift layer. The NiO layer and the drift layer form a heterojunction PN junction structure.

[0010] In an embodiment of the present invention, the thickness of the drift layer is 2 - 14 μm, and the doping concentration is 1×10 15 cm -3 -1×10 17 cm -3 .

[0011] In an embodiment of the present invention, S2 includes:

[0012] S21: Deposit a Ti / Au metal stack on the lower surface of the substrate layer;

[0013] S22: Rapidly anneal the device in an N2 atmosphere to form a cathode, where the annealing temperature is 400 - 600 °C.

[0014] In an embodiment of the present invention, in the S4, the annealing temperature of the low-temperature annealing process is 100 - 500 °C.

[0015] The present invention provides a gallium oxide power diode with a high breakdown voltage, comprising:

[0016] A cathode, a substrate layer, a drift layer, and an anode stacked in sequence from bottom to top, where

[0017] Both the substrate layer and the drift layer are Si- or Sn-doped β-Ga2O3 materials, and the doping concentration of the drift layer is lower than that of the substrate layer;

[0018] The anode is a Ni / Au metal stack, and a NiO layer with P-type characteristics is formed at the interface between the metal Ni and the drift layer. The NiO layer and the drift layer form a heterojunction PN junction structure.

[0019] In an embodiment of the present invention, the doping concentration of the drift layer is 1×10 15 cm -3 -1×10 17 cm -3 .

[0020] In an embodiment of the present invention, the thickness of the drift layer is 2 - 14 μm.

[0021] In an embodiment of the present invention, the cathode is a Ti / Au metal stack.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. In the preparation method of the gallium oxide power diode with a high breakdown voltage of the present invention, through low-temperature annealing, the oxygen in the β-Ga2O3 drift layer and the anode metal Ni form a NiO layer with P-type characteristics, with a thickness of about 1 - 5 nm. The NiO layer can form a heterojunction PN junction structure with the β-Ga2O3 drift layer, modulate the electric field distribution, reduce the concentration of carbon oxides on the surface of gallium oxide, improve the interface characteristics between the anode metal and gallium oxide, and thus reduce the reverse leakage current and increase the breakdown voltage of the device;

[0024] 2. In the preparation method of the gallium oxide power diode with a high breakdown voltage of the present invention, there is no need to deposit P-type materials, and a heterojunction PN junction structure is achieved only through annealing. The technical method is simple and easy to implement;

[0025] 3. The preparation method of the high breakdown voltage gallium oxide power diode of the present invention forms a NiO layer with P-type characteristics through low-temperature annealing. The NiO layer is relatively thin, overcoming the defect that other devices cannot deposit and grow a relatively thin NiO layer, and avoiding the problem of increased on-resistance of the device caused by introducing a relatively thick NiO layer.

[0026] The above description is only an overview of the technical solution of the present invention. In order to be able to more clearly understand the technical means of the present invention, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the drawings, details are as follows. Brief Description of the Drawings

[0027] Figure 1 It is a flowchart of a preparation method of a high breakdown voltage gallium oxide power diode provided by an embodiment of the present invention;

[0028] Figures 2a - 2d It is a process flowchart of a preparation technology of a high breakdown voltage gallium oxide power diode provided by an embodiment of the present invention;

[0029] Figure 3 It is a structural schematic diagram of a high breakdown voltage gallium oxide power diode provided by an embodiment of the present invention. Detailed Embodiments

[0030] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in conjunction with the drawings and specific embodiments, details a high breakdown voltage gallium oxide power diode and its preparation method proposed according to the present invention.

[0031] The foregoing and other technical contents, features and effects of the present invention can be clearly presented in the following detailed description in conjunction with the drawings. Through the description of the specific embodiments, a more in-depth and specific understanding of the technical means and effects adopted by the present invention to achieve the predetermined purpose can be obtained. However, the attached drawings are only for reference and explanation, and are not used to limit the technical solution of the present invention.

[0032] Embodiment 1

[0033] Please refer to Figure 1 , Figure 1 which is a flowchart of a preparation method of a high breakdown voltage gallium oxide power diode provided by an embodiment of the present invention. As shown in the figure, the preparation method of the high breakdown voltage gallium oxide power diode in this embodiment includes:

[0034] S1: Select a substrate layer and prepare a drift layer on the upper surface of the substrate layer;

[0035] In this embodiment, optionally, β-Ga2O3 heavily doped with Si or Sn is selected as the substrate layer, and a layer of β-Ga2O3 lightly doped with Si or Sn is grown above the β-Ga2O3 substrate heavily doped with Si or Sn by using the HVPE (Hydride Vapor Phase Epitaxy) process as the drift layer.

[0036] In this embodiment, the doping concentration of the drift layer is lower than that of the substrate layer.

[0037] Optionally, the thickness of the drift layer is 2 - 14 μm, and the doping concentration is 1×10 15 cm -3 -1×10 17 cm -3 。

[0038] Optionally, the doping concentration of the substrate layer is 5×10 18 cm -3 -5×10 19 cm -3 。

[0039] S2: Prepare a cathode on the lower surface of the substrate layer;

[0040] Specifically, it includes:

[0041] S21: Deposit a Ti / Au metal stack on the lower surface of the substrate layer;

[0042] S22: Perform a rapid annealing process on the device in an N2 atmosphere to form a cathode, where the annealing temperature is 400 - 600 °C.

[0043] In this embodiment, optionally, the thicknesses of the Ti / Au metal stack are 20 / 200 nm respectively.

[0044] S3: Prepare an anode on the upper surface of the drift layer;

[0045] Specifically, deposit a Ni / Au metal stack on the upper surface of the drift layer as the anode.

[0046] In this embodiment, optionally, the thicknesses of the Ni / Au metal stack are 45 / 400 nm respectively.

[0047] S4: Perform a low-temperature annealing process on the device to obtain a gallium oxide power diode;

[0048] Specifically, put the device into an annealing furnace for a low-temperature annealing process, where the annealing temperature is 100 - 500 °C.

[0049] In this embodiment, the device is placed in an annealing furnace for low-temperature annealing process treatment. At this time, the metal Ni in the Ni / Au metal stack and oxygen in the β-Ga2O3 drift layer form a thin NiO layer with P-type characteristics at high temperature, and the thickness is 1-5 nm. This NiO layer can form a heterojunction PN junction structure with the β-Ga2O3 drift layer, modulate the electric field distribution, reduce the concentration of carbon oxides on the surface of gallium oxide, improve the interface characteristics between the anode metal and gallium oxide, and thus reduce the reverse leakage current and increase the breakdown voltage of the device.

[0050] The preparation method of the high-breakdown-voltage gallium oxide power diode in this embodiment does not require depositing P-type materials. Only through annealing, a heterojunction PN junction structure is realized. The technical method is simple and easy to implement. Moreover, the NiO layer with P-type characteristics formed by low-temperature annealing is relatively thin, overcoming the defect that other devices cannot deposit and grow a relatively thin NiO layer, and avoiding the problem of increasing the on-resistance of the device caused by introducing a relatively thick NiO layer.

[0051] Embodiment 2

[0052] Please refer to Figures 2a - 2d , Figures 2a - 2d is the process flow chart of the preparation of a high-breakdown-voltage gallium oxide power diode provided by the embodiment of the present invention. This embodiment specifically describes the preparation method of the high-breakdown-voltage gallium oxide power diode in Embodiment 1.

[0053] 1. Prepare a gallium oxide power diode with a drift layer thickness of 2 μm

[0054] Step 1. Select a substrate layer and prepare a drift layer on the upper surface of the substrate layer.

[0055] Select Si-heavily-doped β-Ga2O3 as the substrate layer, and the doping concentration is 5×10 18 cm -3 , above the Si-heavily-doped β-Ga2O3, use the HVPE process to epitaxially grow a layer of Si-lightly-doped β-Ga2O3 layer as the drift layer, where the drift layer thickness is 2 μm, and the doping concentration of the drift layer is 1×10 15 cm -3 , as shown in Figure 2a shown.

[0056] Step 2. Fabricate the cathode electrode.

[0057] 2.1) Below the substrate layer, sputter the cathode metal through a Sputter device, and the metals are Ti / Au in sequence, with thicknesses of 20 / 200 nm respectively;

[0058] 2.2) Then use an annealing furnace to perform rapid thermal annealing for 30 s in an N2 atmosphere at 400 °C to alloy the cathode metal and complete the fabrication of the cathode electrode, as shown inFigure 2b as shown

[0059] Step 3. Anode metal deposition and NiO formation

[0060] 3.1) Above the lightly doped β-Ga2O3 drift layer, an anode electrode is fabricated using an electron beam evaporation platform. The metals are sequentially selected as Ni / Au, with thicknesses of 45 / 400 nm respectively. After the metal evaporation is completed, lift-off is performed to form the anode electrode, as Figure 2c shown

[0061] 3.2) Place the device in an annealing furnace and perform a 10-minute thermal annealing in an N2 atmosphere at 100 °C. At this time, the metal Ni in the Ni / Au metal stack and the oxygen in the β-Ga2O3 drift layer form a thin NiO layer with P-type characteristics at high temperature, obtaining a gallium oxide power diode with a high breakdown voltage, as Figure 2d shown

[0062] 2. Fabricate a gallium oxide power diode with a drift layer thickness of 8 μm

[0063] Step 1. Select a substrate layer and fabricate a drift layer on the upper surface of the substrate layer

[0064] Select Si-heavily doped β-Ga2O3 as the substrate layer. Above the Si-heavily doped β-Ga2O3, a Si-lightly doped β-Ga2O3 layer is epitaxially grown as the drift layer using the HVPE process. The thickness of the drift layer is 8 μm, and the doping concentration of the drift layer is 1×10 16 cm -3 as Figure 2a shown

[0065] Step 2. Cathode electrode fabrication

[0066] 2.1) Below the substrate layer, sputter the cathode metal using a Sputter device. The metals are sequentially Ti / Au, with thicknesses of 20 / 200 nm respectively

[0067] 2.2) Then use an annealing furnace to perform a 30-second rapid thermal annealing in an N2 atmosphere at 500 °C to alloy the cathode metal and complete the fabrication of the cathode electrode, as Figure 2b shown

[0068] Step 3. Anode metal deposition and NiO formation

[0069] 3.1) Above the lightly doped β-Ga2O3 drift layer, an anode electrode is fabricated using an electron beam evaporation platform. The metals are sequentially selected as Ni / Au, with thicknesses of 45 / 400 nm respectively. After the metal evaporation is completed, lift-off is performed to form the anode electrode, as Figure 2c shown

[0070] 3.2) Place the device in an annealing furnace and perform a 10 - minute thermal annealing in an N₂ atmosphere at 300 °C. At this time, the metal Ni in the Ni / Au metal stack and the oxygen in the β - Ga₂O₃ drift layer form a thin NiO layer with P - type characteristics at high temperature, obtaining a gallium oxide power diode with a high breakdown voltage, as Figure 2d shown.

[0071] 3. Fabricate a gallium oxide power diode with a drift layer thickness of 14 μm

[0072] Step 1. Select a substrate layer and fabricate a drift layer on the upper surface of the substrate layer.

[0073] Select Si - heavily - doped β - Ga₂O₃ as the substrate layer. Above the Si - heavily - doped β - Ga₂O₃, use the HVPE process to epitaxially grow a layer of Si - lightly - doped β - Ga₂O₃ layer as the drift layer, where the drift layer thickness is 14 μm and the doping concentration of the drift layer is 1×10 17 cm -3 , as Figure 2a shown.

[0074] Step 2. Fabricate the cathode electrode.

[0075] 2.1) Below the substrate layer, sputter the cathode metal through a Sputter device. The metals are Ti / Au in sequence, with thicknesses of 20 / 200 nm respectively;

[0076] 2.2) Then use an annealing furnace to perform a 30 - s rapid thermal annealing in an N₂ atmosphere at 600 °C to alloy the cathode metal and complete the fabrication of the cathode electrode, as Figure 2b shown.

[0077] Step 3. Deposit the anode metal and form NiO.

[0078] 3.1) Above the lightly - doped β - Ga₂O₃ drift layer, use an electron beam evaporation platform to fabricate the anode electrode. The metals are Ni / Au in sequence, with thicknesses of 45 / 400 nm respectively. After the metal evaporation is completed, perform metal lift - off to form the anode electrode, as Figure 2c shown;

[0079] 3.2) Place the device in an annealing furnace and perform a 10 - minute thermal annealing in an N₂ atmosphere at 500 °C. At this time, the metal Ni in the Ni / Au metal stack and the oxygen in the β - Ga₂O₃ drift layer form a thin NiO layer with P - type characteristics at high temperature, obtaining a gallium oxide power diode with a high breakdown voltage, as Figure 2d shown.

[0080] Example 3

[0081] This embodiment provides a gallium oxide power diode with a high breakdown voltage. Please refer to Figure 3 , Figure 3 which is a schematic structural diagram of a gallium oxide power diode with a high breakdown voltage provided by an embodiment of the present invention. As shown in the figure, the gallium oxide power diode with a high breakdown voltage in this embodiment includes: a cathode 1, a substrate layer 2, a drift layer 3, and an anode 4 stacked in sequence from bottom to top. Among them, both the substrate layer 2 and the drift layer 3 are Si- or Sn-doped β-Ga2O3 materials, and the doping concentration of the drift layer 3 is lower than that of the substrate layer 2; the anode 4 is a Ni / Au metal stack, and a NiO layer 5 with P-type characteristics is formed at the interface between the metal Ni and the drift layer 3. The NiO layer 5 and the drift layer 3 form a heterojunction PN junction structure.

[0082] In this embodiment, the doping concentration of the drift layer 3 is 1×10 15 cm -3 -1×10 17 cm -3 , and the thickness is 2 - 14 μm.

[0083] In this embodiment, the cathode 1 is a Ti / Au metal stack. Optionally, the thickness of the Ti / Au metal stack is 20 / 200 nm.

[0084] In this embodiment, optionally, the thickness of the Ni / Au metal stack is 45 / 400 nm.

[0085] It should be noted that in this embodiment, when preparing the gallium oxide power diode with a high breakdown voltage, a NiO layer with P-type characteristics is formed by a low-temperature annealing process, in which the anode metal Ni reacts with oxygen in the β-Ga2O3 drift layer. This NiO layer can form a heterojunction PN junction structure with the β-Ga2O3 drift layer, modulate the electric field distribution, reduce the concentration of carbon compounds on the surface of gallium oxide, improve the interface characteristics between the anode metal and gallium oxide, thereby reducing the reverse leakage current and increasing the breakdown voltage of the device.

[0086] In addition, since the NiO layer with P-type characteristics formed by low-temperature annealing is relatively thin, the problem of increased on-resistance of the device caused by introducing a thicker NiO layer is avoided.

[0087] It should be noted that in this text, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that an article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed. Without more limitations, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the article or device including the said element. The orientation or positional relationship indicated by "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention.

[0088] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of a gallium oxide power diode with a high breakdown voltage, characterized in that, Including: S1: Select a substrate layer and fabricate a drift layer on the upper surface of the substrate layer; S2: Fabricate a cathode on the lower surface of the substrate layer; S3: Fabricate an anode on the upper surface of the drift layer; S4: Perform a low-temperature annealing process on the device to obtain a gallium oxide power diode; Wherein, both the substrate layer and the drift layer are Si- or Sn-doped β-Ga2O3 materials, and the doping concentration of the drift layer is lower than that of the substrate layer. The anode is a Ni / Au metal stack, and a NiO layer with P-type characteristics is formed at the interface between the metal Ni and the drift layer. The NiO layer and the drift layer form a heterojunction PN junction structure; When performing the low-temperature annealing process on the device in the annealing furnace in S4, the annealing temperature is 100~500 °C, so that the metal Ni in the Ni / Au metal stack reacts with oxygen in the β-Ga2O3 drift layer to form a NiO layer with P-type characteristics, and this NiO layer and the β-Ga2O3 drift layer form a heterojunction PN junction structure.

2. The preparation method of the gallium oxide power diode with high breakdown voltage according to claim 1, characterized in that, The thickness of the drift layer is 2 - 14 μm, and the doping concentration is 1×10 15 cm -3 -1×10 17 cm -3 .

3. The preparation method of the gallium oxide power diode with high breakdown voltage according to claim 1, characterized in that, S2 includes: S21: Deposit a Ti / Au metal stack on the lower surface of the substrate layer; S22: Perform a rapid annealing process on the device in an N2 atmosphere to form a cathode, where the annealing temperature is 400~600 °C.

4. The manufacturing method of the gallium oxide power diode with high breakdown voltage according to claim 1, characterized in that, In S4, the annealing temperature of the low-temperature annealing process is 100~500 °C.

5. A gallium oxide power diode with a high breakdown voltage, characterized in that, Including: A cathode (1), a substrate layer (2), a drift layer (3), and an anode (4) stacked in sequence from bottom to top. Among them, Both the substrate layer (2) and the drift layer (3) are Si- or Sn-doped β-Ga2O3 materials, and the doping concentration of the drift layer (3) is lower than that of the substrate layer (2); The anode (4) is a Ni / Au metal stack, and a NiO layer (5) with P-type characteristics is formed at the interface between the metal Ni and the drift layer (3). The NiO layer (5) and the drift layer (3) form a heterojunction PN junction structure; The high breakdown voltage gallium oxide power diode is obtained by the following method: S1: Select a substrate layer and fabricate a drift layer on the upper surface of the substrate layer; S2: Fabricate a cathode on the lower surface of the substrate layer; S3: Fabricate an anode on the upper surface of the drift layer; S4: Perform a low-temperature annealing process on the device to obtain a gallium oxide power diode; When performing the low-temperature annealing process on the device in the annealing furnace in S4, the annealing temperature is 100~500 °C, so that the metal Ni in the Ni / Au metal stack reacts with oxygen in the β-Ga2O3 drift layer to form a NiO layer with P-type characteristics, and this NiO layer and the β-Ga2O3 drift layer form a heterojunction PN junction structure.

6. The high breakdown voltage gallium oxide power diode according to claim 5, characterized in that, The doping concentration of the drift layer (3) is 1×10 15 cm -3 -1×10 17 cm -3 .

7. The high breakdown voltage gallium oxide power diode according to claim 5, characterized in that, The thickness of the drift layer (3) is 2 - 14 μm.

8. The gallium oxide power diode with a high breakdown voltage according to claim 5, characterized in that, The cathode (1) is a Ti / Au metal stack.

Images