Multi-channel Schottky diode with three-dimensional fishbone-shaped anode and preparation method thereof

Abstract

The present invention provides a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode and a preparation method thereof, belonging to the technical field of semiconductor devices. The Schottky diode comprises a substrate, a buffer layer, a multi-channel structure and a cap layer, as well as an anode and a cathode stacked in sequence; the multi-channel structure comprises a channel layer and a barrier layer stacked alternately in sequence; the cathode is arranged on both sides of the cap layer and the multi-channel structure, and forms an ohmic contact with the multi-channel structure; a structure composed of a cap layer and a multi-channel structure located between two cathodes is provided with a plurality of anode grooves arranged at intervals, and the anode is deposited in the anode groove and on the surface of the cap layer between two adjacent anode grooves, so that the anode as a whole forms a three-dimensional fishbone-shaped structure with an anode field plate; the anode forms a Schottky contact with the multi-channel structure. The Schottky diode has the characteristics of small parasitic effect, small on-resistance, large breakdown voltage and small turn-on voltage.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor devices, and in particular relates to a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode and a preparation method thereof. Background Art

[0002] The structure of GaN Schottky diode mainly includes body-doped vertical structure and heterojunction lateral structure. Among them, the body-doped vertical structure uses body doping to form a channel. Although it can increase the breakdown voltage and withstand greater input power, the channel resistance is still large and the turn-on voltage is large; the heterojunction lateral structure uses gallium nitride heterojunction to form a two-dimensional electron gas (2DEG), which can reduce the barrier height and reduce the turn-on voltage, but because the anode electrode is in direct contact with the two-dimensional electron gas, the breakdown voltage is too small, and there are also problems such as large on-resistance.

[0003] For example, the prior art 1 "A Novel GaN-Based Metal-2DEG-Metal Varactor With Cutoff Frequency of 3.13THz" (DOI: 10.1109 / TED.2022.3155591) discloses a Schottky diode (SBD) made of gallium nitride (GaN), in which both the cathode and the anode adopt a groove electrode structure, the electrodes are Schottky contacts, and the nonlinear characteristics are realized by the Schottky junction capacitance; the two-dimensional electron gas formed between the AlGaN (aluminum gallium nitride) barrier layer and the GaN layer is used as a channel. The concentration of the two-dimensional electron gas formed by AlGaN and GaN in the Schottky diode is not high enough, the electrode is in direct contact with the two-dimensional electron gas, the barrier is small, and the breakdown voltage is small, resulting in limited input power. Therefore, the frequency multiplier prepared by the SBD of this scheme has a small output of high-order harmonic power.

[0004] Prior art 2, "Multi-Channel Tri-Gate GaN Power Schottky Diodes With Low ON-Resistance" (DOI: 10.1109 / LED.2018.2887199), discloses a multi-channel Schottky diode, which has a vertical structure between the anode and cathode, uses a GaN / AlGaN superlattice structure as a transmission layer, and AlGaN as a drift layer. The on-resistance of the Schottky diode using this solution is larger than that of the lateral structure, resulting in a lower cut-off frequency; and there is parasitic capacitance between the electrode and the channel, resulting in large transmission loss. Summary of the invention

[0005] Based on the above problems, the present invention provides a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode. The Schottky diode has a multi-channel structure and adopts a three-dimensional fishbone-shaped anode; the two-dimensional electron gas of the multi-channel heterojunction forms a Schottky contact with the anode and an ohmic contact with the cathode; the purpose of low turn-on voltage, low on-resistance, low parasitic effect, high breakdown voltage and high rectification efficiency is achieved.

[0006] Specifically, in order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A multi-channel Schottky diode with a three-dimensional fishbone-shaped anode comprises a substrate, a buffer layer, a multi-channel structure and a cap layer stacked in sequence, as well as an anode and a cathode; the multi-channel structure comprises a channel layer and a barrier layer stacked alternately in sequence, the bottom channel layer being located on the surface of the buffer layer facing away from the substrate; the cathode is arranged on both sides of the cap layer and the multi-channel structure, and forms an ohmic contact with the multi-channel structure; a plurality of anode grooves arranged at intervals are arranged on the cap layer and the multi-channel structure between the cathodes, the anode is deposited in the anode groove and on the surface of the cap layer between two adjacent anode grooves, so that the anode as a whole forms a three-dimensional fishbone-shaped structure with an anode field plate; the anode forms a Schottky contact with the multi-channel structure.

[0008] In a preferred solution, along the direction from the substrate to the cap layer, the depth of the anode groove is the same as the thickness of the cathode.

[0009] In a preferred embodiment, the material of the channel layer is GaN or / and Ga2O3.

[0010] In a preferred embodiment, the material of the barrier layer is at least one of AlN, AlGaN, InAlN and AlGaO.

[0011] In a preferred embodiment, the thickness of the channel layer along the direction from the substrate to the cap layer is 2-100 nm.

[0012] In a preferred embodiment, the thickness of the barrier layer in the direction from the substrate to the cap layer is 2-50 nm.

[0013] In a preferred embodiment, the material of the buffer layer is one or more of GaN, AlGaN, and Ga2O3.

[0014] In a preferred solution, the thickness of the buffer layer along the direction from the substrate to the cap layer is 500 nm to 5 μm.

[0015] In a preferred solution, the material of the cap layer is GaN and / or SiN.

[0016] In a preferred embodiment, the thickness of the cap layer in the direction from the substrate to the cap layer is 1-10 nm.

[0017] In a preferred embodiment, the anode is composed of a Ni layer with a thickness of 1 to 50 nm and an Au layer with a thickness of 10 to 500 nm, wherein the thickness of the Ni layer and the Au layer refer to the dimension along the direction from the substrate to the cap layer.

[0018] In a preferred embodiment, the thickness of the cathode in the direction from the substrate to the cap layer is 0.1-1 μm.

[0019] In a further preferred embodiment, along the direction from the substrate to the cap layer, the cathode is sequentially composed of a Ti layer with a thickness of 10 to 50 nm, an Al layer with a thickness of 100 to 200 nm, a Ni layer with a thickness of 30 to 100 nm, and an Au layer with a thickness of 30 to 100 nm.

[0020] In a preferred embodiment, the substrate is any one of a silicon substrate, a sapphire substrate or a silicon carbide substrate.

[0021] The present invention also provides a method for preparing a multi-channel Schottky diode having a three-dimensional fishbone-shaped anode as described in any of the above schemes, comprising the following steps:

[0022] S1. Prepare an epitaxial wafer, wherein the epitaxial wafer comprises a substrate, a buffer layer, a multi-channel structure and a cap layer stacked in sequence; the multi-channel structure comprises a channel layer and a barrier layer stacked alternately in sequence, and the bottom channel layer is located on a surface of the buffer layer away from the substrate;

[0023] S2, etching cathode grooves on both sides of the epitaxial wafer, and stopping the etching in the bottom channel layer; etching a plurality of anode grooves arranged at intervals on the structure composed of the cap layer and the multi-channel; the arrangement direction of the anode grooves is perpendicular to the direction from the substrate to the cap layer and perpendicular to the direction from the cathode groove on one side to the cathode groove on the other side;

[0024] S3, depositing cathode metal in the cathode groove, and annealing in an inert gas atmosphere to obtain a cathode;

[0025] S4, depositing anode metal inside the anode groove and on the surface of the cap layer between two adjacent anode grooves to obtain a three-dimensional fishbone-shaped anode.

[0026] In a preferred embodiment, the thickness of the cathode in a direction from the substrate to the cap layer is 0.1-1 μm.

[0027] In a preferred embodiment, the anode metal is Ni and Au, the thickness of the deposited Ni layer in the direction from the substrate to the cap layer is 1 to 50 nm, and the thickness of the deposited Au layer in the direction from the substrate to the cap layer is 10 to 500 nm.

[0028] In a preferred embodiment, the annealing temperature in step S3 is 830-860° C., and the annealing time is 30-60 seconds.

[0029] In a preferred embodiment, the distance between the anode and the cathode in the direction from the cathode on one side to the cathode on the other side is 100 nm to 10 μm.

[0030] In a preferred embodiment, the width of the three-dimensional fishbone structure of the anode along the second direction is 500nm~40μm, and the length along the direction from the cathode on one side to the cathode on the other side is 500nm~40μm; the second direction is perpendicular to the direction of the substrate pointing to the cap layer and perpendicular to the direction from the cathode on one side to the cathode on the other side.

[0031] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) Small parasitic effect: The electrode is in direct contact with the 2DEG, and the parasitic capacitance and parasitic resistance of the electrode and the channel are both small. (2) Small on-resistance and high current density: Multiple heterostructures are simultaneously used to form a multi-channel structure, and each channel provides a conductive channel, thereby achieving the purpose of increasing the channel carrier concentration and reducing the on-resistance. (3) High breakdown voltage: The anode is designed with a fishbone-shaped field plate structure to optimize the electric field distribution at the contact point between the groove anode and the two-dimensional electrons, reduce the electric field peak, and thus increase the breakdown voltage of the device. (4) Low turn-on voltage: The groove anode adopts a three-dimensional structure, and the three surfaces of the anode can control the two-dimensional electron gas. The two side surfaces are in direct contact with the two-dimensional electron gas, and the contact barrier is smaller, so the turn-on voltage is smaller. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of an epitaxial wafer used in preparing a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode in the present invention;

[0033] Figure 2 It is a schematic diagram of the structure after etching a cathode groove on an epitaxial wafer when preparing a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode in the present invention;

[0034] Figure 3 It is a schematic diagram of a three-dimensional structure obtained after etching cathode grooves and anode grooves on an epitaxial wafer when preparing a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode in the present invention;

[0035] Figure 4 for Figure 3 A top view of

[0036] Figure 5 for Figure 3 A cross-sectional view along the second direction;

[0037] Figure 6 It is a schematic diagram of a three-dimensional structure obtained after depositing a cathode when preparing a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode in the present invention;

[0038] Figure 7 for Figure 6 a cross-sectional view along a third direction;

[0039] Figure 8 Schematic diagram of the three-dimensional structure of a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode prepared according to an embodiment of the present invention, and also a schematic diagram of the three-dimensional structure of a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode provided in Example 1;

[0040] Fig. 9 for Figure 8 A top view of

[0041] Fig.10 for Figure 8 A cross-sectional view along the second direction;

[0042] Fig.11 for Figure 8 A top view of the three-dimensional fishbone structure of the upper anode;

[0043] Fig.12 A schematic diagram of the three-dimensional structure of a multi-channel Schottky diode with a common anode structure;

[0044] Fig.13 The multi-channel Schottky diode with a three-dimensional fishbone-shaped anode provided in Example 1 of the present invention and the Fig.12 The electric field concentration distribution diagram of the Schottky diode of the structure shown;

[0045] Fig.14 The multi-channel Schottky diode with a three-dimensional fishbone-shaped anode provided in Example 1 of the present invention and the Fig.12 The electric field strength comparison diagram of the Schottky diode with the structure shown.

[0046] In the figure: 1, substrate; 2, buffer layer; 3, multi-channel structure; 31, channel layer; 32, barrier layer; 4, cap layer; 5, anode; 51, anode groove; 52, anode field plate; 6, cathode; 61, cathode groove. DETAILED DESCRIPTION

[0047] The following content is combined with the embodiments to clearly and completely describe the technical solution of the present application so that those skilled in the art can fully understand the present application. Obviously, the described embodiments are only some preferred embodiments of the present application, rather than all embodiments. Any equivalent transformation or substitution made to the following implementation modes by those of ordinary skill in the art without creative work belongs to the protection scope of the present application.

[0048] Directional terms described in this application, such as "upper", "lower", "inner", "outer", "bottom", "upper surface", etc., indicate directions or positional relationships based on directions or positional relationships in the drawings of the specification, or directions or positional relationships in which the products of this application are usually placed when in use, and are only for the convenience of describing and understanding the product structure of this application. Therefore, directional terms cannot be understood as limiting this application. In this application, unless otherwise clearly defined, expressions such as "upper", "above", "above", and "upper surface" of a first feature on a second feature indicate that the first feature and the second feature may be in direct contact or indirect contact through an intermediate medium; the first feature may be directly above or obliquely above the second feature, or simply indicate that the first feature is higher in level than the second feature. Expressions such as "lower", "below", "below", and "lower surface" of a first feature on a second feature indicate that the first feature and the second feature may be in direct contact or indirect contact through an intermediate medium; the first feature may be directly below or obliquely below the second feature, or simply indicate that the first feature is lower in level than the second feature. Ordinal numbers used in this application, such as "first", "second", etc., are only used for descriptive purposes to distinguish similar objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. The methods not described in detail in the following embodiments are all conventional methods well known to those skilled in the art.

[0049] Reference Figures 1 to 11 The specific embodiment of the present application provides a method for preparing a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode, comprising the following steps:

[0050] S1. Prepare an epitaxial wafer, which includes a substrate 1, a buffer layer 2, a multi-channel structure 3, and a cap layer 4 from bottom to top; wherein the multi-channel structure 3 includes channel layers 31 and barrier layers 32 alternately stacked in sequence, the bottom channel layer 31 is located on the upper surface of the buffer layer 2, and the top layer of the multi-channel structure 3 is the barrier layer 32. Each channel layer 31 and the barrier layer 32 directly in contact with it form a heterojunction channel, and a two-dimensional electron gas is formed at the contact interface between the two.

[0051] S2, preparation of cathode groove and anode groove: using a hard mask to define the shape of the cathode groove on both sides of the epitaxial wafer through photolithography technology, and using dry etching to etch out the cathode groove 61. The preparation method of the anode groove is the same as the preparation method of the cathode groove, and the etching depth of the anode groove is consistent with the etching depth of the cathode groove, and the number of anode grooves is at least two. After the cathode groove 61 and the anode groove 51 are etched, the structure obtained is as follows Figures 3 to 5 shown.

[0052] S3, preparing the cathode: depositing cathode metal in the cathode groove by electron beam evaporation; after the deposition is completed, annealing is performed in an inert gas (such as nitrogen) atmosphere to obtain a cathode 6 (such as Figure 6 shown).

[0053] S4, preparing the anode: depositing the anode metal on the upper surface of the cap layer 4 inside the anode groove and between two adjacent anode grooves by electron beam evaporation method, to obtain Figure 8 The three-dimensional fishbone-shaped anode 5 including an anode field plate 52 is shown.

[0054] Continue to refer to Figures 1 to 11In the embodiment of the present application, the substrate 1 in step S1 is a commonly used substrate in the art, without limitation, and the substrate generally selected is a silicon substrate, a sapphire substrate, or a silicon carbide substrate. The number of channels of the material multi-channel structure 3 of the buffer layer 2 is at least 2. The material of the channel layer 31 is GaN or / and Ga2O3, and the thickness along the direction from the substrate 1 to the cap layer 4 is 2 to 100 nm, for example, 2nm, 3nm, 4nm, 5nm...100nm. The material of the barrier layer 32 is at least one of AlN, AlGaN, InAlN, and AlGaO. The thickness of the barrier layer 32 along the direction from the substrate 1 to the cap layer 4 is 2 to 50 nm, for example, 2nm, 3nm, 4nm...45nm, 47nm, 49nm, 50nm. The hard mask in step S2 is a commonly used hard mask in the art, for example, any one of a SiO2 mask, a SiN mask, and a Ni mask. The cross-sectional shape of the anode groove 51 etched in step S2 on a plane parallel to the substrate 1 is a rectangle. In step S3, the cathode metal is Ti / Al / Ni / Au, and the total thickness (the dimension of the cathode 6 in the direction from the substrate 1 to the cap layer 4) is 0.1 to 1 μm; for example, the total thickness of the cathode 6 is 0.1 μm, 0.2 μm, 0.3 μm, 0.35 μm, ... 1 μm; further, the thickness of the Ti layer of the cathode 6 is 10 to 50 nm (for example, 10 nm, 11 nm, 12 nm, 13 nm ... 45 nm, 47 nm, 50 nm), and the thickness of the Al layer is 100 The thickness of the Ni layer is 30 to 100 nm (for example, 30 nm, 31 nm, 32 nm, 33 nm ... 95 nm, 98 nm, 100 nm), and the thickness of the Au layer is 30 to 100 nm (for example, 30 nm, 31 nm, 32 nm, 33 nm ... 85 nm, 90 nm, 100 nm). The annealing temperature is 830 to 860 ° C, and the annealing time is 30 to 60 s. In step S4, the anode metal is Ni / Au, wherein the thickness of the Ni layer is 1 to 50 nm, and the thickness of the Au layer is 10 to 500 nm; for example, the thickness of the Ni layer is 1 nm, 2 nm, 3 nm, ... 20 nm, 21 nm, 25 nm, ... 50 nm, and the thickness of the Au layer is 10 nm, 11 nm, 12 nm, ... 300 nm, 301 nm, 305 nm, ... 480 nm, 490 nm, ... 500 nm. In step S4, the anode field plate 52 ( Figure 8The cross-sectional shape of the anode 5 in the plane parallel to the substrate 1 is not limited, and is generally a common regular graphic structure such as a rectangle, a semicircle, a triangle, etc. The direction from the substrate 1 to the cap layer 4 is defined as the first direction, the direction from the cathode on one side to the cathode on the other side (or the direction from the cathode groove on one side to the cathode groove on the other side) is defined as the third direction, and the second direction is the direction perpendicular to both the first direction and the third direction. In step S4, the width W of the three-dimensional fishbone structure of the anode 5 along the second direction is 500nm~40μm, and the length L along the third direction is 500nm~40μm; for example, the width W of the three-dimensional fishbone structure of the anode 5 is 500nm, 501nm, 502nm, 503nm...1000nm, 1001nm, 1100nm, 1200nm...5μm, 5.1μm, 5.2μm...10μm, 10.1μm , 10.2μm, 11μm, 12μm, 13μm...40μm; the length L of the three-dimensional fishbone structure of the anode 5 is 500nm, 502nm, 508nm, 511nm...1100nm, 1105nm, 1200nm, 1300nm...6μm, 6.5μm, 6.8μm...10μm, 10.5μm, 11.2μm, 12.5μm, 12.6μm, 15μm...40μm. In the Schottky diode structure finally obtained in step S4, along the third direction, the distance between the anode 5 and the cathode 6 is 100nm~10μm, for example, the distance between the anode 5 and the cathode 6 is 100nm, 101nm, 102nm...200nm, 210nm, 215nm...1000nm, 1100nm...2μm, 3μm, 3.5μm...10μm.

[0055] Example 1

[0056] Reference Figure 6 , 8 10, a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode, comprising, from bottom to top, a substrate 1, a buffer layer 2, a multi-channel structure 3 and a cap layer 4, as well as an anode 5 and a cathode 6 stacked in sequence. A plurality of alternately stacked channel layers 31 and barrier layers 32 form a multi-channel structure 3 (the number of channels in the multi-channel structure 3 is at least two); wherein the bottommost channel layer 31 is located on the surface of the buffer layer 2 facing away from the substrate 1. Figure 8As shown, two channel layers 31 and two barrier layers 32 are alternately stacked to form two heterojunction channel structures. The bottom channel layer 31 is located on the upper surface of the buffer layer 2, and the upper surface of the top barrier layer 32 is the cap layer 4. The cathode 6 is arranged on both sides of the cap layer 4 and the multi-channel structure 3, and directly forms an ohmic contact with the two-dimensional electron gas in the multi-channel structure 3. The direction from the substrate 1 to the cap layer 4 is defined as the first direction, the direction from the cathode on one side to the cathode on the other side is defined as the third direction, and the second direction is a direction perpendicular to both the first direction and the third direction. Between the two cathodes 6 on both sides of the cap layer 4, a structure composed of the cap layer 4 and the multi-channel structure 3 is etched with multiple (at least two, for example) electrodes along the second direction. Figure 6 The anode 5 is deposited in these anode grooves and on the upper surface of the cap layer 4 between two adjacent anode grooves; and the anode 5 located on the surface of the cap layer 4 has a certain height (i.e., Fig.10 As shown above, in the direction from the substrate 1 to the cap layer 4, the anode 5 located on the upper surface of the cap layer 4 forms an upward convex structure), so that the anode 5 as a whole forms a three-dimensional fishbone structure including an anode field plate 52. The anode 5 forms a Schottky contact with the two-dimensional electron gas in the multi-channel structure 3.

[0057] Further, the depth of the anode groove 51 in the first direction is the same as the thickness of the cathode 6 in the first direction.

[0058] Furthermore, the material of the channel layer 31 is GaN or / and Ga2O3.

[0059] Furthermore, the material of the barrier layer 32 is at least one of AlN, AlGaN and InAlN.

[0060] Further, the thickness of the channel layer 31 along the first direction is 2-100 nm, for example, 2 nm, 3 nm, 4 nm, 5 nm, . . . 100 nm.

[0061] Further, the thickness of the barrier layer 32 along the first direction is 2-50 nm, for example, 2 nm, 3 nm, 4 nm, 5 nm, . . . 50 nm.

[0062] Furthermore, the material of the buffer layer 2 is one or more of GaN, AlGaN, and Ga2O3.

[0063] Further, the thickness of the buffer layer 2 along the first direction is 500 nm to 5 μm, for example, 500 nm, 501 nm, 505 nm, 510 nm, 512 nm, 515 nm, 520 nm, ..., 1 μm, 1.1 μm, 1.2 μm, 1.25 μm, ..., 5 μm.

[0064] Furthermore, the material of the cap layer 4 is GaN and / or SiN.

[0065] Further, the thickness of the cap layer 4 along the first direction is 1-10 nm, for example, 1 nm, 2 nm, 3 nm, . . . 10 nm.

[0066] Furthermore, the anode 5 is composed of a Ni layer and an Au layer; the thickness of the Ni layer along the first direction is 1 to 50 nm, for example, 1 nm, 2 nm, 3 nm, ... 50 nm; the thickness of the Au layer along the first direction is 10 to 500 nm, for example, 10 nm, 11 nm, 12 nm, 15 nm, 18 nm, ... 500 nm.

[0067] Further, the cathode 6 is composed of a Ti layer, an Al layer, a Ni layer and an Au layer; wherein the thickness of the Ti layer along the first direction is 10 to 50 nm, for example, 10 nm, 15 nm, 18 nm, 20 nm...40 nm, 48 nm, 50 nm; the thickness of the Al layer along the first direction is 100 nm to 200 nm, for example, 100 nm, 105 nm, 110 nm, 115 nm...185 nm, 195 nm, 200 nm; the thickness of the Ni layer along the first direction is 30 to 100 nm, for example, 30 nm, 35 nm, 40 nm...85 nm, 90 nm, 100 nm; the thickness of the Au layer along the first direction is 30 to 100 nm, for example, 30 nm, 35 nm, 38 nm, 40 nm...91 nm, 95 nm, 100 nm.

[0068] Further, along the third direction, the distance between the anode 5 and the cathode 6 is 10nm to 10μm; for example, the distance between the anode 5 and the cathode 6 is 10nm, 11nm, 12nm, 15nm, 20nm, 22nm, 24nm...5μm, 5.1μm, 5.2μm...10μm.

[0069] Furthermore, the width of the three-dimensional fishbone structure of the anode 5 along the second direction is 500nm~40μm, for example, 500nm, 501nm, 502nm, 503nm...10μm, 10.1μm, 10.2μm...40μm; the length of the three-dimensional fishbone structure of the anode 5 along the third direction is 500nm~40μm, for example, 500nm, 501nm, 502nm, 505nm...15μm, 15.1μm, 15.2μm...40μm.

[0070] Furthermore, the substrate 1 is any one of a silicon substrate, a sapphire substrate, and a silicon carbide substrate.

[0071] Example 2

[0072] Reference Figures 1 to 11, a method for preparing a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode, comprising the following steps:

[0073] S1. Prepare an epitaxial wafer, which includes a substrate 1, a buffer layer 2, a multi-channel structure 3, and a cap layer 4 from bottom to top; wherein the multi-channel structure 3 includes channel layers 31 and barrier layers 32 alternately stacked in sequence, the bottom channel layer 31 is located on the upper surface of the buffer layer 2, and the top layer of the multi-channel structure 3 is the barrier layer 32. For example, Figure 1 Two superimposed channel structures are shown in FIG. 1 , each of which includes a channel layer and a barrier layer located on the upper surface of the channel layer. Therefore, the bottom channel layer 31 is located on the upper surface of the buffer layer 2, and the upper surface of the top barrier layer 32 is the cap layer 4. The material of the substrate 1 is silicon; the material of the buffer layer 2 is GaN, and the thickness in the direction from the substrate 1 to the cap layer 4 is 1000nm; the material of the channel layer 31 is GaN, and the thickness in the direction from the substrate 1 to the cap layer 4 is 50nm; the material of the barrier layer 32 is AlN, and the thickness in the direction from the substrate 1 to the cap layer 4 is 20nm; the material of the cap layer 4 is GaN, and the thickness in the direction from the substrate 1 to the cap layer 4 is 5nm.

[0074] S2. Prepare cathode grooves and anode grooves: Use a hard mask to define the shape of the cathode groove on both sides of the epitaxial wafer through photolithography technology, and use dry etching to etch the cathode groove 61. For example, use PECVD (plasma enhanced chemical vapor deposition) to grow a 300nm thick SiO2 film as a hard mask, first use CF4 / O2 to perform RIE etching (reactive ion etching) to open the hard mask, and then use BCl3 / Cl2 to perform ICP (inductively coupled plasma etching) dry etching on the cap layer 4 and the multi-channel structure 3. The etching stops at the bottom channel layer 31 of the multi-channel structure 3 to obtain the cathode groove 61; finally, wet etching is used to remove the SiO2 mask. The preparation method of the anode groove is the same as the preparation method of the cathode groove, and in the direction from the cap layer 4 to the substrate 1, the etching depth of the anode groove 51 is consistent with the etching depth of the cathode groove 61; the number of anode grooves is at least two (for example Figure 3 The cross-sectional shape of the anode groove 51 obtained by etching on a plane parallel to the substrate 1 is a rectangle. The direction from the substrate 1 to the cap layer 4 is defined as the first direction, the direction from the cathode on one side to the cathode on the other side (or the direction from the cathode groove on one side to the cathode groove on the other side) is defined as the third direction, and the second direction is a direction perpendicular to both the first direction and the third direction; the anode grooves 51 are arranged at intervals along the second direction. The structure obtained after the cathode groove 61 and the anode groove 51 are etched is as follows Figures 3 to 5 shown. Figure 3 This is the three-dimensional structure diagram after etching is completed. Figure 4 for Figure 3A top view of Figure 5 for Figure 3 A cross-sectional view along the second direction.

[0075] S3, preparing the cathode: depositing a Ti layer with a thickness of 10 nm, an Al layer with a thickness of 160 nm, a Ni layer with a thickness of 55 nm, and an Au layer with a thickness of 45 nm in the cathode groove in sequence by electron beam evaporation; after the deposition is completed, annealing is performed at 850° C. for 40 seconds in an inert gas (such as nitrogen) atmosphere to obtain a cathode 6 (such as Figure 6 The thickness of the cathode 6 in the direction from the substrate 1 to the cap layer 4 is 0.27 μm.

[0076] S4. Prepare the anode: Deposit a Ni layer with a thickness of 30 nm (the dimension along the direction from the substrate 1 to the cap layer 4) and an Au layer with a thickness of 250 nm (the dimension along the direction from the substrate 1 to the cap layer 4) in sequence on the upper surface of the cap layer 4 inside the anode groove and between two adjacent anode grooves by electron beam evaporation to obtain the following: Figure 8 The three-dimensional fishbone-shaped anode 5 having an anode field plate 52 is shown. Figure 8 The cross-sectional shape of the anode field plate 52 on the cross section parallel to the substrate 1 is a semicircle, and the radius of the semicircle is smaller than the distance between the anode and the cathode in the third direction. Along the third direction, the distance between the anode 5 and the cathode 6 is 3 μm. Figure 8 and Fig.11 The width W of the three-dimensional fishbone structure of the anode 5 along the second direction is 5 μm, and the length L along the third direction is 10 μm.

[0077] Example 3

[0078] Reference Figures 1 to 11 The method for preparing a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode in this embodiment is basically the same as that in Embodiment 2, except that:

[0079] In step S1, the substrate is a sapphire substrate; the material of the buffer layer 2 is AlGaN, and the thickness in the direction from the substrate 1 to the cap layer 4 is 500nm; the material of the channel layer 31 is Ga2O3, and the thickness is 2nm; the material of the barrier layer 32 is AlGaN, and the thickness of the barrier layer is 2nm; the material of the cap layer 4 is SiN, and the thickness in the direction from the substrate 1 to the cap layer 4 is 1nm.

[0080] In step S3, the annealing temperature is 830°C and the annealing time is 60s. The thickness of the cathode 6 in the direction from the substrate 1 to the cap layer 4 is 0.18 μm, and the cathode 6 is composed of a Ti layer with a thickness of 20 nm, an Al layer with a thickness of 100 nm, a Ni layer with a thickness of 30 nm, and an Au layer with a thickness of 30 nm.

[0081] In step S4, the thickness of the Ni layer is 1 nm, and the thickness of the Au layer is 10 nm; along the third direction, the distance between the anode 5 and the cathode 6 is 100 nm; the width W of the three-dimensional fishbone structure of the anode 5 along the second direction is 500 nm, and the length L along the third direction is 500 nm.

[0082] Example 4

[0083] Reference Figures 1 to 11 The method for preparing a multi-channel Schottky diode with a three-dimensional fishbone-shaped anode in this embodiment is basically the same as that in Embodiment 2, except that:

[0084] In step S1, the substrate is a silicon carbide substrate; the material of the buffer layer 2 is Ga2O3, and the thickness in the direction from the substrate 1 to the cap layer 4 is 5μm; the material of the channel layer 31 is GaN and Ga2O3, and the thickness of the channel layer 31 in the direction from the substrate 1 to the cap layer 4 is 100nm; the material of the barrier layer 32 is InAlN, and the thickness of the barrier layer 32 in the direction from the substrate 1 to the cap layer 4 is 50nm; the material of the cap layer 4 is GaN and SiN, and the thickness in the direction from the substrate 1 to the cap layer 4 is 5nm.

[0085] In step S3, the annealing temperature is 860°C and the annealing time is 30s. The thickness of the cathode 6 in the direction from the substrate 1 to the cap layer 4 is 0.45 μm, and the cathode 6 is composed of a Ti layer with a thickness of 50 nm, an Al layer with a thickness of 200 nm, a Ni layer with a thickness of 100 nm, and an Au layer with a thickness of 100 nm.

[0086] In step S4, the thickness of the Ni layer is 50 nm, and the thickness of the Au layer is 500 nm; along the third direction, the distance between the anode 5 and the cathode 6 is 10 μm; the width W of the three-dimensional fishbone structure of the anode 5 along the second direction is 40 μm, and the length L along the third direction is 40 μm.

[0087] Schottky diode performance test

[0088] The Schottky diode in Example 1 and the multi-channel Schottky diode without a three-dimensional fishbone anode (structure as shown in FIG. Fig.12 As shown in the figure, simulation (simulation software: TCAD) experiments were carried out to compare the electric field concentration distribution and electric field strength. The results are shown in Figures 13-14 shown. Fig.13 Figure (a) shows a multi-channel Schottky diode without a three-dimensional fishbone anode (i.e. Fig.12 (a) is the electric field distribution diagram of the Schottky diode of the embodiment 1, and (b) is the electric field distribution diagram of the Schottky diode of the embodiment 1. The Schottky diode structures used in (a) and (b) are the same in material and size except for the anode structure. Fig.13It can be seen from the figure that after using the three-dimensional fishbone anode, the peak electric field concentration at the edge of the anode is significantly reduced, and the electric field distribution is more uniform. Fig.14 It can be seen that the Schottky diode in Example 1 adopts a three-dimensional fishbone-shaped anode, and the peak concentration of the electric field is Fig.12 The breakdown voltage of the Schottky diode with a three-dimensional fishbone anode decreased by 46%.

[0089] The above-described embodiments are only preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. For any person skilled in the art, the present application may have various changes and modifications. Any simple equivalent changes and modifications made based on the scope of protection of the present application and the contents of the specification should be included in the scope of protection of the present application.

Claims

1. A multi-channel Schottky diode with a three-dimensional fishbone-shaped anode, characterized in that: It comprises a substrate, a buffer layer, a multi-channel structure and a cap layer, as well as an anode and a cathode which are stacked in sequence; the multi-channel structure comprises a channel layer and a barrier layer which are alternately stacked in sequence, and the bottom channel layer is located on the surface of the buffer layer away from the substrate; the cathode is arranged on both sides of the cap layer and the multi-channel structure, and forms an ohmic contact with the multi-channel structure; a plurality of anode grooves arranged at intervals are arranged on the cap layer and the multi-channel structure between the cathodes, and the anode is deposited in the anode groove and on the surface of the cap layer between two adjacent anode grooves, so that the anode as a whole forms a three-dimensional fishbone structure with an anode field plate; the anode forms a Schottky contact with the multi-channel structure.

2. The multi-channel Schottky diode with a three-dimensional fishbone-shaped anode according to claim 1, characterized in that: The material of the channel layer is GaN and / or Ga2O3; or / and the material of the barrier layer is at least one of AlN, AlGaN, InAlN and AlGaO.

3. The multi-channel Schottky diode with a three-dimensional fishbone-shaped anode according to claim 1, characterized in that: The thickness of the channel layer along the direction from the substrate to the cap layer is 2 to 100 nm; or / and the thickness of the barrier layer along the direction from the substrate to the cap layer is 2 to 50 nm.

4. The multi-channel Schottky diode with a three-dimensional fishbone-shaped anode according to claim 1, characterized in that: The material of the buffer layer is one or more of GaN, AlGaN, and Ga2O3; or / and the material of the cap layer is GaN or / and SiN.

5. The multi-channel Schottky diode with a three-dimensional fishbone-shaped anode according to claim 1, characterized in that: The substrate is any one of a silicon substrate, a sapphire substrate or a silicon carbide substrate.

6. The method for preparing a multi-channel Schottky diode having a three-dimensional fishbone-shaped anode according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Prepare an epitaxial wafer, wherein the epitaxial wafer comprises a substrate, a buffer layer, a multi-channel structure and a cap layer stacked in sequence; the multi-channel structure comprises a channel layer and a barrier layer stacked alternately in sequence, and the bottom channel layer is located on a surface of the buffer layer away from the substrate; S2, etching cathode grooves on both sides of the epitaxial wafer, and stopping the etching in the bottom channel layer; etching a plurality of anode grooves arranged at intervals on the structure composed of the cap layer and the multi-channel; the arrangement direction of the anode grooves is perpendicular to the direction from the substrate to the cap layer and perpendicular to the direction from the cathode groove on one side to the cathode groove on the other side; S3, depositing cathode metal in the cathode groove, and annealing in an inert gas atmosphere to obtain a cathode; S4, depositing anode metal inside the anode groove and on the surface of the cap layer between two adjacent anode grooves to obtain a three-dimensional fishbone-shaped anode.

7. The preparation method according to claim 6, characterized in that: The thickness of the cathode in the direction from the substrate to the cap layer is 0.1 to 1 μm; or / and, the anode metal is Ni and Au, the thickness of the deposited Ni layer in the direction from the substrate to the cap layer is 1 to 50 nm, and the thickness of the deposited Au layer in the direction from the substrate to the cap layer is 10 to 500 nm.

8. The preparation method according to claim 6, characterized in that: In step S3, the annealing temperature is 830-860° C., and the annealing time is 30-60 seconds.

9. The preparation method according to claim 6, characterized in that: Along the direction from the cathode on one side to the cathode on the other side, the distance between the anode and the cathode is 100 nm to 10 μm.

10. The preparation method according to claim 6, characterized in that: The three-dimensional fishbone structure of the anode has a width of 500nm to 40μm along the second direction, and a length of 500nm to 40μm along the direction from the cathode on one side to the cathode on the other side; the second direction is perpendicular to the direction from the substrate to the cap layer and perpendicular to the direction from the cathode on one side to the cathode on the other side.

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