Transverse Schottky diode with gradient AlGaN terminal structure and preparation method of transverse Schottky diode

Abstract

The invention relates to the technical field of power semiconductors, and particularly discloses a transverse Schottky diode of a gradient AlGaN terminal structure and a preparation method of the transverse Schottky diode. On the basis of a traditional field plate transverse Schottky diode, the AlGaN layer is divided into the AlGaN barrier layer and the Alx-y Ga1-x-1-y N terminal layer, and the Al element content in the Alx-y Ga1-x-1-y N terminal layer structure can be adjusted, so that polarization body charges with negative electricity characteristics are generated under the polarization effect, a virtual gate-like structure is formed, and the field plate transverse Schottky diode is formed. The phenomenon that the electric field at the edge of the field plate is excessively concentrated is relieved, so that the electric field distribution is optimized and the voltage resistance of the device is improved; the structure that the Alx-y Ga1-x-1-y N terminal layer partially covers or fully covers the upper surface of the AlGaN barrier layer is adopted, consumption of two-dimensional electron gas at the AlGaN / GaN interface is reduced, it is ensured that the transverse Schottky diode still has the good forward conduction characteristic, the contradictory phenomenon of mutual restriction of breakdown voltage and conduction resistance is improved, and the performance of the transverse Schottky diode is improved. The problems that the field plate edge electric field of a traditional transverse Schottky diode is too concentrated, and the multi-field plate optimization structure process is complex are solved.

Description

Technical Field

[0001] This application relates to the technical field of power semiconductors, and particularly to a lateral Schottky diode with a graded AlGaN terminal structure and a preparation method thereof. Background Art

[0002] In power rectifiers, Schottky barrier diodes (SBDs) with low forward voltage drops are widely used in high-frequency circuits, power electronic devices, mixers, detectors, etc. because they do not have the minority carrier storage effect and have the advantages of short reverse recovery time and fast switching speed. In recent years, with the gradual increase in the demand for high-power applications in industrial production and life, as a key part of the power system, SBDs not only need to meet the increasing requirements for working voltage and working current, but also have increasingly stringent requirements for their breakdown voltage performance.

[0003] In the actual manufacturing process of SBDs, planar processes are often used. However, the junction surface of the Schottky junction is not an ideal plane and has a certain curvature. This curvature effect is often caused by the edge structure and will cause the breakdown voltage to be lower than that of a parallel plane junction under the same conditions. To reduce or eliminate this curvature plane effect, a series of junction termination technologies have been developed, such as Field Plate (FP), Field Limiting Ring (FLR), Junction Termination Extention (JTE), ion implantation termination, etc. Among them, the field plate technology is an effective junction termination technology. It can not only relieve the phenomenon of overly concentrated edge electric fields, but also avoid problems caused by the difficulty of p-type doping in materials such as GaN / Ga2O3 heterojunctions. It has also been widely used in power devices due to its relatively simple process and compatibility with device processes.

[0004] However, field plate terminals usually need to be redesigned with the changes in device size / structure to achieve the targeted effect of alleviating the edge electric field concentration. For example, for traditional field plate structures, in order to reduce the electric field peak at the end of the field plate, the field plate length often needs to be extended. However, when the field plate length reaches a certain critical value, not only the purpose of increasing the breakdown voltage cannot be achieved, but also the device area is wasted due to the overly long terminal area. Therefore, in order to optimize the target edge electric field and the edge electric field of the field plate itself, and ensure that the device can operate stably at the expected voltage without early avalanche breakdown, it is often necessary to adjust multiple details such as the field plate dielectric layer material, thickness, length, and possible segmentation, stepped, composite structures, etc. The above-mentioned field plate terminals have exacerbated the process complexity due to the increasingly complex device structures and stringent performance requirements. Therefore, there is an urgent need for a highly directional, simple process, and adaptable device to effectively alleviate the problems of excessive concentration of the field plate edge electric field and complex process of optimizing the field plate terminal structure. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a lateral Schottky diode with a graded AlGaN terminal structure and its manufacturing method, which are used to solve the problems of overly concentrated edge electric field of the field plate and complex process of optimizing the field plate terminal structure in traditional lateral Schottky diodes.

[0006] To achieve the above technical purpose, this application provides a lateral Schottky diode with a graded AlGaN terminal structure, which includes a substrate, a buffer layer, a GaN channel layer, an AlGaN layer arranged in sequence from bottom to top, and also includes a passivation layer and an electrode layer;

[0007] The AlGaN layer includes an AlGaN barrier layer and an Al x→y Ga 1-x→1-y N terminal layer arranged in sequence from bottom to top; the content of Al element in the Al x→ y Ga 1-x→1-y N terminal layer decreases gradually from bottom to top along the direction perpendicular to the substrate;

[0008] A first notch is provided on the side of the Al x→y Ga 1-x→1-y N terminal layer in the horizontal direction, and the first notch extends from top to bottom along the direction perpendicular to the Al x→ y Ga 1-x→1-y N terminal layer to the upper surface of the AlGaN barrier layer; the first notch is filled with the passivation layer, and the passivation layer is also laid on the upper surface of the Al x→y Ga 1-x→1-y N terminal layer;

[0009] A second notch is provided along the side in the horizontal direction of the passivation layer and extends downward to 1 / 25 to 1 / 2 of the thickness of the GaN channel layer. The second notch is filled with an electrode layer, and the electrode layer partially covers the upper surface of the passivation layer;

[0010] The electrode layer includes an anode layer and a cathode layer. The anode layer partially covering the upper surface of the passivation layer forms a continuous projection area in the vertical direction perpendicular to the Al x→ y Ga 1-x→1-y N termination layer.

[0011] Further, both x and y are the molar fraction values of the Al x→y Ga 1-x→1-y element in the AlGaN termination layer, and 0 < x ≤ 1, 0 ≤ y < x.

[0012] Further, the Al x→y Ga 1-x→1-y N termination layer partially covers the AlGaN barrier layer, and the coverage area accounts for 10 to 100% of the total area of the upper surface of the AlGaN barrier layer.

[0013] Further, the vertical projection area of the anode layer on the upper surface of the Al x→y Ga 1-x→1-y N termination layer accounts for 20 to 80% of the total area of the upper surface of the Al x→ y Ga 1-x→1-y N termination layer.

[0014] Further, the thickness of the Al x→y Ga 1-x→1-y N termination layer is 5 to 40 nm.

[0015] Further, the Al x→y Ga 1-x→1-y N termination layer is formed by the polarization effect to have a polarization body charge density with negative electrical properties of 0.5×10 17 ~0.9×10 19 cm -3 .

[0016] Further, the molar fraction of the Al element in the AlGaN barrier layer is 0.2 to 0.3, and the thickness of the AlGaN barrier layer is 5 to 40 nm.

[0017] Further, the passivation layer includes one or more of HfO2, Al2O3, SiO2, SiN, Ta2O5, and the thickness of the passivation layer is 0.02 to 2 μm; the thickness of the GaN channel layer is 0.2 μm to 5 μm; the buffer layer includes one or more of high-resistance GaN, high-resistance AlN, high-resistance AlGaN, and the thickness of the buffer layer is 1 to 5 μm.

[0018] Further, the electrode layer includes an ohmic cathode and an anode. The material of the ohmic cathode is one of a Ti / Au layer, a Ti / Al / Au layer, a Ti / Al / Ti / Au layer, and a Ti / Al / Ni / Au layer; the material of the anode is one of an Au layer, a Ni layer, a Pt layer, a Cu layer, and a TiN layer.

[0019] This application also provides a preparation method for a lateral Schottky diode with a graded AlGaN termination structure, including the following steps:

[0020] Step S1: Deposit a buffer layer, a GaN channel layer, an AlGaN barrier layer, and an Al x→y Ga 1-x→1-y N termination layer on the substrate in sequence to obtain a first prefabricated lateral Schottky diode.

[0021] Step S2: Preset the coverage area of the Al x→y Ga 1-x→1-y N termination layer on the AlGaN barrier layer. According to the preset coverage area, coat photoresist on the surface of the Al x→y Ga 1-x→1-y N termination layer. After coating is completed, perform exposure and development operations in sequence, and then use dry etching to form a first notch on the side of the horizontal direction of the Al x→y Ga 1-x→1-y N termination layer to obtain a second prefabricated lateral Schottky diode.

[0022] Step S3: Perform coating, exposure, and development operations on the second prefabricated lateral Schottky diode to determine the second notch area. Use dry etching to etch from the AlGaN barrier layer to 1 / 25 to 1 / 2 of the thickness of the GaN channel layer to form a second notch, and then perform an annealing operation to obtain a third prefabricated lateral Schottky diode.

[0023] Step S4: Perform coating, exposure, and development operations on the third prefabricated lateral Schottky diode to determine the growth area of the passivation layer. Deposit the passivation layer on the surface of the Al x→y Ga 1-x→1-y N termination layer and at the first notch to obtain a fourth prefabricated lateral Schottky diode.

[0024] Step S5: Perform coating, exposure, and development operations on the fourth prefabricated lateral Schottky diode to determine the growth area of the cathode layer. Deposit the cathode layer on the surface of the passivation layer and at the second notch, and perform an annealing operation after deposition to obtain a fifth prefabricated lateral Schottky diode.

[0025] Step S6: Glue application, exposure, and development operations are performed on the fifth prefabricated lateral Schottky diode to determine the growth region of the anode layer. The anode layer is deposited on the surface of the passivation layer and at the second notch to obtain a lateral Schottky diode with a graded AlGaN termination structure.

[0026] In summary, the present application provides a lateral Schottky diode with a graded AlGaN termination structure, including a substrate, a buffer layer, a GaN channel layer, and an AlGaN layer sequentially arranged from bottom to top, and further provided with a passivation layer and an electrode layer; the AlGaN layer includes an AlGaN barrier layer and an Al x→y Ga 1-x→1-y N termination layer sequentially arranged from bottom to top; the content of Al element in the Al x→y Ga 1-x→1-y N termination layer decreases gradually from bottom to top along the direction perpendicular to the substrate; a first notch is provided on the side of the Al x→y Ga 1-x→1-y N termination layer in the horizontal direction, and the first incision extends from top to bottom along the direction perpendicular to the Al x→y Ga 1-x→1-y N termination layer to the upper surface of the AlGaN barrier layer; the first notch is filled with the passivation layer, and the passivation layer is also laid on the upper surface of the Al x→y Ga 1-x→1-y N termination layer; a second notch is provided on the side of the passivation layer in the horizontal direction and extends downward to 1 / 25 to 1 / 2 of the thickness of the GaN channel layer. The second notch is filled with the electrode layer, and the electrode layer partially covers the upper surface of the passivation layer; the electrode layer includes an anode layer and a cathode layer, and the anode layer partially covering the upper surface of the passivation layer forms a continuous projection area in the vertical direction perpendicular to the Al x→y Ga 1-x→1-y N termination layer. By setting the Al x→y Ga 1-x→1-y N termination layer structure that can adjust the Al element, the polarization charges with negative electrical properties formed by the polarization effect form a "virtual gate" - like structure below the edge of the field plate, which can effectively alleviate the phenomenon of excessive electric field concentration at the edge of the field plate, thereby optimizing the overall electric field distribution and significantly improving the breakdown voltage of the device; the structure in which the Al x→ y Ga 1-x→1-y N termination layer partially covers or completely covers the upper surface of the AlGaN barrier layer is also adopted, reducing the consumption of two - dimensional electron gas at the AlGaN / GaN interface, ensuring that the device still has good forward conduction characteristics, and greatly improving the contradictory phenomenon between the breakdown voltage and the on - resistance in the device.

[0027] Compared with the prior art, the Al x→y Ga 1-x→1-yThe N-terminal layer structure forms a polarized body charge with a negatively charged characteristic by utilizing the polarization effect, and a p-type Al can be formed without any p-type doping. x→y Ga 1-x→1-y N layer, effectively solving a series of problems such as dopant activation, crystal growth defects, and process complexity in traditional p-type wide-bandgap semiconductor materials; in addition, for the lateral Schottky diode with a graded AlGaN terminal structure provided by the present invention, the coverage area of the Al x→y Ga 1-x→1-y N terminal layer on the upper surface of the AlGaN barrier layer, and the decreasing trend of Al element in the Al x→y Ga 1-x→1-y N terminal layer can also be adaptively adjusted according to the requirements of the target lateral Schottky diode to fabricate the target lateral Schottky diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is a schematic structural diagram of a lateral Schottky diode with a graded AlGaN terminal structure provided by an embodiment of the present invention;

[0030] Figures 2 to 5 It is a schematic diagram of the structural change of the manufacturing process of a lateral Schottky diode with a graded AlGaN terminal structure provided by an embodiment of the present invention;

[0031] Figure 6 It is a schematic structural diagram of a traditional field plate lateral Schottky diode;

[0032] Figure 7 It is a distribution diagram of the electric field in the horizontal direction near the bottom of the metal-semiconductor contact of the lateral Schottky diodes provided by the embodiments and comparative examples of the present invention;

[0033] Figure 8 It is for the reverse of the lateral Schottky diodes provided by the embodiments and comparative examples of the present invention characteristic curve graph;

[0034] Reference numerals: 101, substrate; 102, buffer layer; 103, GaN channel layer; 104-1, AlGaN barrier layer; 104-2, Al x→y Ga 1-x→1-y N terminal layer; 105, passivation layer; 106, anode; 107, ohmic cathode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this specification of the present application without creative efforts belong to the scope claimed by the present application.

[0036] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present application 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 thus cannot be construed as a limitation to the present application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0037] Unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0038] Among them, there are no special restrictions on the sources of all raw materials of the present invention, and they can be purchased on the market or prepared according to the conventional methods well-known to those skilled in the art.

[0039] The embodiments of the present invention provide a lateral Schottky diode with a graded AlGaN termination structure, which includes a substrate, a buffer layer, a GaN channel layer, and an AlGaN layer arranged in sequence from bottom to top, and further includes a passivation layer and an electrode layer;

[0040] The AlGaN layer includes an AlGaN barrier layer and an Al x→y Ga 1-x→1-y N termination layer arranged in sequence from bottom to top; Al x→ y Ga 1-x→1-y The content of Al element in the N termination layer decreases gradually from bottom to top along the direction perpendicular to the substrate;

[0041] Along the horizontal side of the Al x→y Ga 1-x→1-y N termination layer, a first notch is provided, and the first notch is along the direction perpendicular to Al x→ y Ga1-x→1-y The direction of the N-terminal layer extends downward from top to bottom to the upper surface of the AlGaN barrier layer; the first notch is filled with a passivation layer, and the passivation layer is also laid on the x→y Ga 1-x→1-y upper surface of the N-terminal layer;

[0042] A second notch is provided extending downward from the side portion in the horizontal direction of the passivation layer to 1 / 25 to 1 / 2 of the thickness of the GaN channel layer. The second notch is filled with an electrode layer, and the electrode layer partially covers the upper surface of the passivation layer;

[0043] The electrode layer includes an anode layer and a cathode layer. The anode layer partially covering the upper surface of the passivation layer forms a continuous projection region in the vertical direction perpendicular to the x→ y Ga 1-x→1-y N-terminal layer.

[0044] It should be noted that x→y means that the Al component content continuously decreases from x to y along the direction from the GaN channel layer to the passivation layer. In the x→y Ga 1-x→1-y N-terminal layer, the content of the Al element and the field plate length are both flexibly adjustable parameters. The present invention realizes the optimization of the device performance through these two key technical paths. On the one hand, by precisely regulating the content of the Al element, a "virtual gate" structure is constructed under the edge of the field plate by the polarization body charges with negative electrical properties generated by the polarization effect, effectively regulating the charge density, and then realizing the uniformization of the electric field distribution, significantly improving the breakdown voltage performance of the power device. For example, when a reverse bias is applied, the x→y Ga 1-x→1-y polarization body charges with negative electrical properties formed by the N layer can effectively expand the depletion region boundary and weaken the electric field crowding effect at the edge of the metal field plate. On the other hand, by adjusting the x→y Ga 1-x→1-y coverage area of the N-terminal layer on the AlGaN barrier layer, the consumption phenomenon of the two-dimensional electron gas (2DEG) at the AlGaN / GaN interface can be effectively suppressed. This measure ensures that the device can reduce the on-resistance to maintain good on-state performance under forward bias conditions. In summary, the present invention realizes the optimization of the contradictory performances of "breakdown voltage and on-resistance" synchronously in the same device system by combining the above two technical means.

[0045] In some embodiments, both x and y are the x→y Ga 1-x→1-y mole fraction values of the Al element in the N-terminal layer, and 0 < x ≤ 1, 0 ≤ y < x.

[0046] In some embodiments, x→y Ga 1-x→1-yThe N-terminal layer partially covers the AlGaN barrier layer, and the coverage area accounts for 10-100% of the total upper surface area of the AlGaN barrier layer.

[0047] In some embodiments, the vertical projection of the anode layer on the x→y Ga 1-x→1-y upper surface of the N-terminal layer has a projection area that accounts for 20-80% of the total upper surface area of the x→y Ga 1-x→1-y N-terminal layer.

[0048] Specifically, when the length of the x→y Ga 1-x→1-y N-terminal layer is 2.5-125 μm, the length of the vertical projection of the electrode layer on the x→ y Ga 1-x→1-y upper surface of the N-terminal layer is 0.5-100 μm.

[0049] In some embodiments, the thickness of the x→y Ga 1-x→1-y N-terminal layer is 5-40 nm.

[0050] In some embodiments, the x→y Ga 1-x→1-y N-terminal layer forms a polarization body charge density with negative electrical properties due to the polarization effect, which is 0.5×10 17 ~0.9×10 19 cm -3 .

[0051] In some embodiments, the molar fraction of Al element in the AlGaN barrier layer is 0.2-0.3, and the thickness of the AlGaN barrier layer is 5-40 nm.

[0052] In some embodiments, the passivation layer includes one or more of HfO2, Al2O3, SiO2, SiN, Ta2O5, and the thickness of the passivation layer is 0.02-2 μm; the thickness of the GaN channel layer is 0.2 μm-5 μm; the buffer layer includes one or more of high-resistance GaN, high-resistance AlN, high-resistance AlGaN, and the thickness of the buffer layer is 1-5 μm.

[0053] In some embodiments, the electrode layer includes an ohmic cathode and an anode. The material of the ohmic cathode is one of Ti / Au layer, Ti / Al / Au layer, Ti / Al / Ti / Au layer, Ti / Al / Ni / Au layer; the material of the anode is one of Au layer, Ni layer, Pt layer, Cu layer, TiN layer.

[0054] This application also provides a preparation method for a lateral Schottky diode with a graded AlGaN terminal structure, including the following steps:

[0055] Step S1: Deposit a buffer layer, a GaN channel layer, an AlGaN barrier layer, and an Al x→y Ga 1-x→1-y N termination layer on the substrate in sequence to obtain a first prefabricated lateral Schottky diode;

[0056] Step S2: Preset the coverage area of the Al x→y Ga 1-x→1-y N termination layer on the AlGaN barrier layer. According to the preset coverage area, coat photoresist on the surface of the Al x→y Ga 1-x→1-y N termination layer. After the coating is completed, perform exposure and development operations in sequence. Then, use dry etching to form a first notch on the lateral side in the horizontal direction of the Al x→y Ga 1-x→1-y N termination layer to obtain a second prefabricated lateral Schottky diode;

[0057] Step S3: Perform coating, exposure, and development operations on the second prefabricated lateral Schottky diode to determine the second notch area. Use dry etching to etch from the AlGaN barrier layer to 1 / 25 to 1 / 2 of the thickness of the GaN channel layer to form a second notch. Then, perform an annealing operation to obtain a third prefabricated lateral Schottky diode;

[0058] Step S4: Perform coating, exposure, and development operations on the third prefabricated lateral Schottky diode to determine the growth area of the passivation layer. Deposit the passivation layer on the surface of the Al x→y Ga 1-x→1-y N termination layer and at the first notch to obtain a fourth prefabricated lateral Schottky diode;

[0059] Step S5: Perform coating, exposure, and development operations on the fourth prefabricated lateral Schottky diode to determine the growth area of the cathode layer. Deposit the cathode layer on the surface of the passivation layer and at the second notch. After the deposition is completed, perform an annealing operation to obtain a fifth prefabricated lateral Schottky diode;

[0060] Step S6: Perform coating, exposure, and development operations on the fifth prefabricated lateral Schottky diode to determine the growth area of the anode layer. Deposit the anode layer on the surface of the passivation layer and at the second notch to obtain a lateral Schottky diode with a graded AlGaN termination structure.

[0061] The applicant further provides the following specific reference examples to describe the present invention. It should be noted that these examples are merely descriptive and do not limit the present invention in any way.

[0062] Example 1

[0063] See Figure 1 In this embodiment, a lateral Schottky diode with a graded AlGaN termination structure is provided, which includes a substrate 101, a buffer layer 102, a GaN channel layer 103, and an AlGaN layer 104 arranged in sequence from bottom to top. It also includes a passivation layer 105, an anode layer 106, and a cathode layer 107;

[0064] The AlGaN layer 104 includes an AlGaN barrier layer 104-1 and an Al x→y Ga 1-x→1-y N termination layer 104-2 arranged in sequence from bottom to top; Al x→y Ga 1-x→1-y In the Al x→y Ga 1-x→1-y N termination layer 104-2, the content of Al element decreases gradually from bottom to top along the direction perpendicular to the substrate 101; a first notch is provided on the side of the Al x→y Ga 1-x→1-y N termination layer 104-2 in the horizontal direction. The first notch extends from top to bottom along the direction perpendicular to the Al x→y Ga 1-x→1-y N termination layer 104-2 to the upper surface of the AlGaN barrier layer 104-1; the first notch is filled with the passivation layer 105, and the passivation layer 105 is also laid on the upper surface of the Al x→y Ga 1-x→1-y N termination layer 104-2; a second notch is provided on the side of the passivation layer 105 in the horizontal direction and extends downward to a depth of 0.02 μm of the GaN channel layer 103. The second notch is filled with the cathode layer 107 and the anode layer 106, and the cathode layer 107 and the anode layer 106 cover the upper surface of the passivation layer; The Al x→ y Ga 1-x→1-y N termination layer 104-2 partially covers the AlGaN barrier layer 104-1, and the coverage area ratio is 50%; the vertical projection of the anode layer 106 on the Al x→y Ga 1-x→1-y N termination layer 104-2 accounts for 50% of the total area of the Al

[0065] Among them, the parameters of each functional layer in the lateral Schottky diode with a graded AlGaN termination structure are shown in Table 1.

[0066] Table 1. Parameter values of each functional layer in the lateral Schottky diode with a graded AlGaN termination structure

[0067]

[0068] This embodiment also provides a preparation method for a lateral Schottky diode with a graded AlGaN termination structure. Combining the parameters in Table 1, it is prepared according to the following steps:

[0069] Step S1, using MOCVD (Metal Organic Chemical Vapor Deposition) technology, buffer layer 102, GaN channel layer 103, AlGaN barrier layer 104-1, and Al x→y Ga 1-x→1-y N terminal layer 104-2 are sequentially deposited on the substrate 101 to obtain the first prefabricated lateral Schottky diode as shown in Figure 2 Figure;

[0070] Step S2, preset the vertical projection area of the electrode layer on the Al x→y Ga 1-x→1-y N terminal layer 104-2 to be 50%, and the coverage area of the Al x→y Ga 1-x→1-y N terminal layer 104-2 on the AlGaN barrier layer 104-1 to be 50%. According to the preset coverage area, photoresist is coated on the surface of the Al x→y Ga 1-x→1-y N terminal layer 104-2. After the coating is completed, the photoresist is successively exposed and developed to obtain a photoresist pattern. The photoresist pattern is used as a mask layer, and then Cl2 and BCl3 are used as etching gases for ICP etching to etch from the Al x→y Ga 1-x→1-y N terminal layer 104-2 to the AlGaN barrier layer 104-1 to form a first notch with a depth of 15 nm, and obtain the second prefabricated lateral Schottky diode as shown in Figure 3 Figure;

[0071] Step S3, perform coating, exposure, and development operations on the second prefabricated lateral Schottky diode to form a second notch by etching from the AlGaN barrier layer 104-1 to 0.02 μm of the GaN channel layer 103. At a depth of 0.28 μm of the GaN channel layer 103, after the etching is completed, annealing is performed in an N2 environment at 450 °C for 5 min to repair the etching damage, and a third prefabricated lateral Schottky diode with a cathode layer 107 and an anode layer 106 notch region is obtained, as shown in Figure 4 Figure;

[0072] Step S4, perform coating, exposure, and development operations on the third prefabricated lateral Schottky diode to determine the passivation layer growth region. Use magnetron sputtering technology to deposit HfO2 on the first notch and the surface of the Al x→y Ga 1-x→1-y N terminal layer 104-2 to form a passivation layer 105, and obtain the fourth prefabricated lateral Schottky diode as shown in Figure 5 Figure;

[0073] Step S5: Glue coating, exposure, and development operations are performed on the fourth prefabricated lateral Schottky diode to determine the cathode layer growth region. A Ti / Al / Ti / Au metal stack is deposited on the surface of the passivation layer 105 and at the second notch through thermal evaporation to form the cathode layer. The thickness of the metal stack is 10 / 30 / 60 / 100 nm. After the deposition is completed, the photoresist is stripped, and then annealing is performed in an N2 environment at 850 °C for 30 s to obtain the fifth prefabricated lateral Schottky diode;

[0074] Step S6: Glue coating, exposure, and development operations are performed on the fifth prefabricated lateral Schottky diode to determine the anode growth region. A Ni / Au metal stack is deposited on the second notch in the anode region and the surface of the passivation layer 105 through thermal evaporation to form the anode layer. The thickness of the metal stack is 30 / 300 nm. After the deposition is completed, the photoresist is stripped, and finally, the lateral Schottky diode with a graded AlGaN termination structure is obtained. See Figure 1 .

[0075] Example 2

[0076] The difference from Example 1 is that the material of the substrate 101 is GaN.

[0077] Example 3

[0078] The difference from Example 1 is that the molar fraction of Al x→y Ga 1-x→1-y in the AlGaN terminal layer 104-2 decreases from 0.5 to 0.25, i.e., x→y = 0.5→0.25.

[0079] Example 4

[0080] The difference from Example 1 is that the molar fraction of Al x→y Ga 1-x→1-y in the AlGaN terminal layer 104-2 decreases from 0.6 to 0.4, i.e., x→y = 0.6→0.4.

[0081] Example 5

[0082] The difference from Example 1 is that the AlGaN terminal layer 104-2 partially covers the AlGaN barrier layer 104-1, and the coverage area ratio is 70%; the vertical projections of the ohmic cathode 107 and the anode 106 on the Al x→y Ga 1-x→1-y GaN terminal layer 104-2 together account for 30% of the total area of the Al x→y Ga 1-x→1-y GaN terminal layer 104-2. x→y Ga 1-x→1-y The ratio is 30%.

[0083] Example 6

[0084] The difference from Example 1 is that Al x→y Ga 1-x→1-y The N-terminal layer 104-2 partially covers the AlGaN barrier layer 104-1, and the covered area accounts for 50%; the vertical projections of the ohmic cathode 107 and the anode 106 on the Al x→y Ga 1-x→1-y The sum of the projected areas of the N-terminal layer 104-2 accounts for 70% of the total area of the Al x→y Ga 1-x→1-y N-terminal layer 104-2.

[0085] Comparative Example 1

[0086] See Figure 6 , this comparative example provides a lateral Schottky diode with a traditional field plate structure. The difference from the embodiment is that the AlGaN barrier layer 104-1 is used to replace the Al x→y Ga 1-x→1-y N-terminal layer 104-2, and no first notch is opened at both ends of the AlGaN layer 104.

[0087] The electric field distribution and breakdown voltage of the lateral Schottky diodes prepared in the above embodiments and comparative examples are tested, and the results are shown in Figures 7 to 8 .

[0088] As Figure 7 shown, the gray and black lines in the figure respectively show the electric field distribution in the horizontal direction near the bottom of the Au-Semiconductor contact of the lateral Schottky diodes provided in Example 1 and Comparative Example 1 of the present invention under a reverse bias voltage of 1600V. Through the analysis of this figure, it can be seen that under the same reverse bias voltage condition, the lateral Schottky diode provided in Example 1 shows a smaller electric field distribution; compared with Comparative Example 1, the electric field at the edge of the field plate is significantly reduced from 2.3 MV / cm to 1.5 MV / cm. In addition, the effects of Examples 2-6 are similar to those of Example 1, so they will not be elaborated one by one here.

[0089] As Figure 8 shown, the gray and black lines in the figure respectively show the reverse I-V characteristic diagrams of the lateral Schottky diodes provided in Example 1 and Comparative Example 1 of the present invention. It can be seen from the figure that the lateral Schottky diode provided in Example 1 has a higher breakdown voltage. Taking the reverse leakage current of 1 mA / cm² as an example, the breakdown voltage value of the lateral Schottky diode provided in Example 1 is as high as 4250V; while for the traditional field plate lateral Schottky diode under the same leakage current level, the breakdown voltage value is only about 1500V. Therefore, compared with the traditional lateral Schottky diode, the breakdown voltage of the structure provided in Example 1 of the present invention is increased from 1500V to 4250V, and the improvement amplitude is nearly 3 times. In addition, the experimental effects of Examples 2-6 are similar to those of Example 1, so they will not be elaborated one by one here.

[0090] The foregoing are the preferred embodiments of the present application and are not intended to limit the present invention. Although the present application has been described in detail with reference to the examples, those skilled in the art can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A lateral Schottky diode with a graded AlGaN termination structure, comprising a substrate, a buffer layer, a GaN channel layer, and an AlGaN layer sequentially arranged from bottom to top, characterized in that, It also includes a passivation layer and an electrode layer; The AlGaN layer includes an AlGaN barrier layer and an Al x→y Ga 1-x→1-y N termination layer, which are sequentially arranged from bottom to top; the Al x→ y Ga 1-x→1-y element content in the N termination layer decreases gradually from bottom to top along the direction perpendicular to the substrate; Along the Al x→y Ga 1-x→1-y A first notch is provided on the side of the AlGaN termination layer in the horizontal direction. The first notch extends downward from top to bottom in a direction perpendicular to the AlGaN termination layer to the upper surface of the AlGaN barrier layer; the first notch is filled with the passivation layer, and the passivation layer is also laid on the upper surface of the AlGaN termination layer x→y Ga 1-x→1-y N termination layer; x→y Ga 1-x→1-y N termination layer; A second notch is provided extending downward from the side portion in the horizontal direction of the passivation layer to 1 / 25 to 1 / 2 of the thickness of the GaN channel layer. The second notch is filled with the electrode layer, and the electrode layer partially covers the upper surface of the passivation layer; The electrode layer includes an anode layer and a cathode layer, and the anode layer partially covering the upper surface of the passivation layer forms a continuous projection area in the vertical direction perpendicular to the Al x→y Ga 1-x→1-y N terminal layer.

2. The lateral Schottky diode with a graded AlGaN termination structure according to claim 1, wherein: Both x and y are Al x→y Ga 1-x→1-y The molar fraction value of the Al element in the N-terminal layer, and 0 < x ≤ 1, 0 ≤ y < x.

3. The lateral Schottky diode with a graded AlGaN termination structure according to claim 1, wherein: The Al x→y Ga 1-x→1-y The N-terminal layer covers the AlGaN barrier layer, and the coverage area accounts for 10-100% of the total upper surface area of the AlGaN barrier layer.

4. The lateral Schottky diode with a graded AlGaN termination structure according to claim 1, wherein: The vertical projection of the anode layer on the upper surface of the Al x→y Ga 1-x→1-y N termination layer accounts for 20% to 80% of the total area of the upper surface of the Al x→ y Ga 1-x→1-y N termination layer.

5. The lateral Schottky diode with a graded AlGaN termination structure according to claim 1, wherein: The Al x→y Ga 1-x→1-y The thickness of the N-terminal layer is 5 to 40 nm.

6. The lateral Schottky diode with a graded AlGaN termination structure according to claim 1, wherein: The Al x→y Ga 1-x→1-y The N-terminal layer forms a polarized body with negative electrical properties due to the polarization effect, and the polarized body charge density is 0.5×10 17 ~0.9×10 19 cm -3 .

7. The lateral Schottky diode with a graded AlGaN termination structure according to claim 1, wherein: The molar fraction of Al element in the AlGaN barrier layer is 0.2 to 0.3, and the thickness of the AlGaN barrier layer is 5 to 40 nm.

8. The lateral Schottky diode with a graded AlGaN termination structure according to claim 1, wherein: The passivation layer includes one or more of HfO2, Al2O3, SiO2, SiN, Ta2O5, and the thickness of the passivation layer is 0.02 to 2 μm; The thickness of the GaN channel layer is 0.2 μm to 5 μm; The buffer layer includes one or more of high-resistance GaN, high-resistance AlN, high-resistance AlGaN, and the thickness of the buffer layer is 1 to 5 μm.

9. The lateral Schottky diode with a graded AlGaN termination structure according to claim 1, wherein: The electrode layer includes an ohmic cathode and an anode. The material of the ohmic cathode is one of Ti / Au layer, Ti / Al / Au layer, Ti / Al / Ti / Au layer, Ti / Al / Ni / Au layer; the material of the anode is one of Au layer, Ni layer, Pt layer, Cu layer, TiN layer.

10. A method for manufacturing a lateral Schottky diode with a graded AlGaN termination structure as described in any one of claims 1 to 9, characterized in that, It includes the following steps: Step S1, deposit a buffer layer, a GaN channel layer, an AlGaN barrier layer, and an Al x→y Ga 1-x→1-y N termination layer on a substrate in sequence to obtain a first prefabricated lateral Schottky diode; Step S2, preset the Al x→y Ga 1-x→1-y coverage area of the N-terminal layer on the AlGaN barrier layer, and coat photoresist on the surface of the Al x→y Ga 1-x→1-y N-terminal layer according to the preset coverage area. After the coating is completed, perform exposure and development operations in sequence, and then use dry etching to form a first notch on the side of the Al x→y Ga 1-x→1-y N-terminal layer in the horizontal direction to obtain a second prefabricated lateral Schottky diode; Step S3: Perform glue coating, exposure, and development operations on the second prefabricated lateral Schottky diode to determine the second notch area. Use dry etching to etch from the AlGaN barrier layer to 1 / 25 to 1 / 2 of the thickness of the GaN channel layer to form a second notch, and then perform an annealing operation to obtain a third prefabricated lateral Schottky diode; Step S4, perform glue coating, exposure, and development operations on the third prefabricated lateral Schottky diode to determine the passivation layer growth region, and deposit the passivation layer on the surface of the Al x→y Ga 1-x→1-y N terminal layer and at the first notch to obtain a fourth prefabricated lateral Schottky diode; Step S5: Perform glue coating, exposure, and development operations on the fourth prefabricated lateral Schottky diode to determine the growth area of the cathode layer. Deposit the cathode layer on the surface of the passivation layer and at the second notch. After the deposition is completed, perform an annealing operation to obtain a fifth prefabricated lateral Schottky diode; Step S6: Perform glue coating, exposure, and development operations on the fifth prefabricated lateral Schottky diode to determine the growth area of the anode layer. Deposit the anode layer on the surface of the passivation layer and at the second notch to obtain a lateral Schottky diode with a graded AlGaN termination structure.

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