A wide bandgap semiconductor hybrid pin schottky diode and method of fabrication

Abstract

The application discloses a wide-bandgap semiconductor mixed PiN Schottky diode and a preparation method, and belongs to the technical field of diodes. The diode comprises a cathode metal, a first-conductivity-type heavily doped substrate, a first-conductivity-type heavily doped buffer layer, a first-conductivity-type drift region, a second-conductivity-type body region and an anode metal which are sequentially stacked. The anode metal and a surface contact area of the second-conductivity-type body region form an ohmic contact, and the anode metal and a surface contact area of the first-conductivity-type drift region form a Schottky contact. The first-conductivity-type drift region comprises a third region, a second region and a first region which are sequentially stacked, and the first region is located on a side of the first-conductivity-type drift region close to the anode metal. The average doping concentration of the first region is greater than the minimum doping concentration of the second region, and the average doping concentration of the third region is greater than the minimum doping concentration of the second region.

Description

Technical Field

[0001] This application belongs to the field of diode technology, specifically relating to a wide bandgap semiconductor hybrid PiN Schottky diode and its fabrication method. Background Technology

[0002] Currently, wide-bandgap semiconductors, represented by silicon carbide (SiC) and gallium nitride (GaN), have broad application prospects in the field of power electronics. Among vertical structure diodes, the hybrid PiN Schottky (MPS) diode has attracted widespread attention.

[0003] However, in the design of vertical third-generation semiconductor MPS devices, there is a severe constraint between the forward specific on-resistance and the reverse breakdown voltage. How to significantly reduce the specific on-resistance while maintaining or even improving the reverse blocking capability of the device has become an urgent problem to be solved. Summary of the Invention

[0004] This application provides a wide bandgap semiconductor hybrid PiN Schottky diode and its fabrication method, which can significantly reduce the specific on-resistance while maintaining or even improving the reverse blocking capability of the device.

[0005] The first aspect of this application provides a wide bandgap semiconductor hybrid PiN Schottky diode, the diode comprising, in sequence: a cathode metal, a heavily doped substrate of a first conductivity type, a heavily doped buffer layer of a first conductivity type, a drift region of a first conductivity type, a body region of a second conductivity type, and an anode metal; The second conductivity type body regions are periodically arranged on the side surface of the first conductivity type drift region away from the cathode metal; the anode metal and the surface contact area of ​​the second conductivity type body regions form an ohmic contact, and the anode metal and the surface contact area of ​​the first conductivity type drift region form a Schottky contact; The first conductivity type drift region includes a third region, a second region, and a first region stacked sequentially, wherein the first region is located on the side of the first conductivity type drift region closer to the anode metal; Wherein, the average doping concentration of the first region is greater than the minimum doping concentration of the second region; and the average doping concentration of the third region is greater than the minimum doping concentration of the second region.

[0006] In some embodiments, the minimum doping concentration of the second region is Nmid; The first region is the area in the first conductivity type drift region that extends downwards from the surface of the first conductivity type drift region near the anode metal until the doping concentration first drops to 1.2 Nmid; The thickness of the first region is greater than or equal to the thickness of the second conductive type body region, and the surface of the second conductive type body region facing away from the anode metal is in contact with the first region.

[0007] In some embodiments, the thickness of the first region is 1.5 to 4.0 times the thickness of the second conductive body region, including endpoint values ​​and reasonable deviations due to process variations, wherein the second conductive body region is completely embedded within the first region in the longitudinal direction.

[0008] In some embodiments, the first region is divided into an upper first region layer and a lower first region layer from top to bottom along the longitudinal depth; Wherein, the thickness of the upper layer of the first region is less than the thickness of the second conductivity type body region; the average doping concentration of the upper layer of the first region is greater than or equal to three times the lowest doping concentration of the second region; the average doping concentration of the lower layer of the first region is less than the average doping concentration of the upper layer of the first region, and greater than the lowest doping concentration of the second region.

[0009] In some embodiments, the ratio between the average doping concentration of the first region and the average doping concentration of the second region is greater than or equal to 1.5 and less than or equal to 5.0. The ratio between the average doping concentration of the third region and the average doping concentration of the second region is greater than or equal to 1.5 and less than or equal to 7.0.

[0010] In some embodiments, the depth of the second region accounts for more than or equal to 65% and less than or equal to 85% of the total depth of the first conductivity type drift region.

[0011] In some embodiments, the integral surface charge density of the first conductivity type donor impurity in the first region is calculated using the following formula: ,in, The integral surface charge density of the first region; The thickness of the first region is N(x); N(x) is the doping concentration distribution function at a depth x, starting from the surface position of the first conductivity type drift region near the anode metal side as the starting point 0. Integral surface charge density of donor impurities of the first conductivity type in the first region The range of values ​​for satisfies: .

[0012] In some embodiments, the minimum doping concentration of the second region is Nmid; The third region is the region in the first conductivity type drift region that extends upwards from the surface of the first conductivity type drift region near the cathode metal until the doping concentration first drops to 1.2 Nmid; The integral surface charge density of the first conductivity type donor impurity in the third region The range of values ​​for satisfies: , in, The total thickness of the drift region of the first conductivity type; Let N(x) be the thickness of the third region, and let N(x) be the doping concentration distribution function at a depth x, starting from the surface position of the first conductivity type drift region near the anode metal side as the starting point 0. The integral surface charge density of the first conductivity type donor impurity in the third region The range of values ​​for satisfies: .

[0013] In some embodiments, the materials of the first conductivity type heavily doped substrate and the first conductivity type drift region are selected from silicon carbide, gallium nitride, gallium oxide, aluminum nitride, or diamond.

[0014] In some embodiments, the doping concentration of the second conductivity type body region is greater than or equal to and less than or equal to .

[0015] In some embodiments, the width ratio K between the second conductive body region and the adjacent Schottky contact region is greater than or equal to 0.5 and less than or equal to 2.0.

[0016] In some embodiments, the doping concentration curve of the first conductivity type drift region along the depth direction exhibits a U-shaped distribution characteristic that first decreases and then increases from the anode side downwards.

[0017] The second aspect of this application also provides a method for fabricating a wide-bandgap semiconductor hybrid PiN Schottky diode, applied to the fabrication of the Schottky diode described in the first aspect of this application, the method comprising: A wide-bandgap semiconductor substrate heavily doped with a first conductivity type is provided to obtain a heavily doped substrate of the first conductivity type. A multilayer continuous epitaxial growth process is employed to grow a first conductivity type heavily doped buffer layer on one side of a first conductivity type heavily doped substrate, followed by the growth of a first conductivity type drift region. During the growth of the first conductivity type drift region, the flow rate of the donor impurity source gas is nonlinearly adjusted, or other doping concentration modulation methods are used to form a stacked first region, a second region, and a third region. The average doping concentration of the first region is greater than the minimum doping concentration of the second region, and the average doping concentration of the third region is greater than the minimum doping concentration of the second region. A second conductivity type volume region is prepared on the surface of the first conductivity type drift region after growth; A cathode metal is prepared on the surface of the first conductivity type heavily doped substrate on the side away from the first conductivity type drift region; An anode metal is prepared on the surface of the second conductivity type body region on the side opposite to the first conductivity type drift region.

[0018] The beneficial effects of this application embodiment are as follows: This application embodiment reconstructs the internal electric field distribution under reverse bias by constructing a U-shaped doping distribution in the drift region (the first conductivity type drift region includes a first region, a second region, and a third region stacked together; wherein the average doping concentration of the first region is greater than the lowest doping concentration of the second region; and the average doping concentration of the third region is greater than the lowest doping concentration of the second region). Although the high doping at the top (first region) makes the surface peak electric field slightly higher than that of the traditional uniformly doped structure, due to the extremely thin layer, the electric field decreases sharply with depth, and the high-risk region of avalanche integration is quickly suppressed, failing to reach the critical integration condition for avalanche breakdown caused by impact ionization; combined with the low-doped second region in the middle for main voltage division, the device's excellent high-voltage blocking capability is ensured.

[0019] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the scale in the drawings is for illustration only and does not represent the actual scale.

[0021] Figure 1This is a schematic diagram of the structure of a wide bandgap semiconductor hybrid PiN Schottky diode proposed in the embodiments of this application; Figure 2 This is a schematic diagram of another Schottky diode structure proposed in the embodiments of this application; Figure 3 This is a schematic diagram of a U-shaped doped device and a uniformly doped device under the same breakdown voltage constraint, as proposed in the embodiments of this application. Figure 4 This is a schematic diagram comparing the forward conduction curve of this application with that of conventional uniform doping, as proposed in the embodiments of this application; Figure 5 This is a reverse blocking characteristic curve proposed in the embodiments of this application, which is different from that of conventional uniform doping; Figure 6 This is a flowchart illustrating the steps of a method for fabricating a wide-bandgap semiconductor hybrid PiN Schottky diode as proposed in an embodiment of this application. Detailed Implementation

[0022] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first" and "second" are generally of the same class, not limited in number; for example, the first object can be one or at least two. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] In the description of this application, it should be noted that the term "layer" refers to a division of material including a region of thickness. A layer may extend over the entirety of a structure below or above. Furthermore, a layer may extend horizontally, vertically, and / or along an inclined surface. A layer may contain multiple sublayers. Additionally, in this application, the use of "connection" or "joint" may indicate direct or indirect contact between corresponding components, unless otherwise expressly defined or inferred from the context.

[0025] Currently, wide-bandgap semiconductors, represented by silicon carbide (SiC) and gallium nitride (GaN), have broad application prospects in the field of power electronics. Although lateral GaN power devices have achieved certain commercial success due to their advantages such as two-dimensional electron gas, as the voltage level (e.g., 1200V and above) and current requirements of applications continue to increase, lateral devices are revealing bottlenecks such as uneven electric field distribution, surface state effects, and weak current carrying capacity per unit area.

[0026] In vertical structure devices, current flows longitudinally, significantly increasing current density and allowing for higher breakdown voltages through increased drift region thickness. Therefore, vertical structure devices are considered more suitable for high-voltage, high-current applications. Among vertical structure diodes, the Merged PiN Schottky diode (MPS) has attracted widespread attention. It combines the advantages of a Schottky barrier diode (SBD)—low forward voltage drop and no reverse recovery charge—with the introduction of periodically arranged P+ injection regions below the Schottky region. This utilizes the electric field shielding effect generated by the depletion layer of the PN junction under reverse bias to effectively reduce the peak electric field at the Schottky interface, thereby significantly improving the device's reverse breakdown voltage.

[0027] However, in the design of vertical third-generation semiconductor MPS devices, there is a severe constraint between forward specific on-resistance and reverse breakdown voltage. Traditional MPS devices typically employ a low-concentration, uniformly doped N-drift region. To achieve high breakdown voltage, an extremely low doping concentration and a relatively thick drift region are necessary, inevitably leading to a significant increase in bulk resistance. Simultaneously, the presence of the P+ injection region squeezes the forward current path, further increasing the specific on-resistance. Under traditional uniform doping theory, device performance is strictly limited by the theoretical limits of one-dimensional materials, making it difficult to further reduce conduction losses without sacrificing breakdown voltage. Therefore, breaking through the theoretical ceiling of traditional uniformly doped drift regions, maintaining or even improving the reverse blocking capability while significantly reducing specific on-resistance, and developing a novel gallium nitride (GaN) MPS diode device that combines high breakdown voltage and low conduction loss has significant technical and engineering value.

[0028] To address the aforementioned issues, this application proposes a wide-bandgap semiconductor hybrid PiN Schottky diode and its fabrication method, which aims to significantly reduce specific on-resistance while maintaining or even enhancing the reverse blocking capability of the device.

[0029] The first aspect of this application provides a wide-bandgap semiconductor hybrid PiN Schottky diode, with reference to... Figure 1 , Figure 1A schematic diagram of a wide-bandgap semiconductor hybrid PiN Schottky diode is shown, as follows: Figure 1 As shown, the Schottky diode includes: The diode comprises, in sequence, a cathode metal, a heavily doped substrate of a first conductivity type, a heavily doped buffer layer of a first conductivity type, a drift region of a first conductivity type, a body region of a second conductivity type, and an anode metal; The second conductivity type body regions are periodically arranged on the side surface of the first conductivity type drift region away from the cathode metal; the anode metal and the surface contact area of ​​the second conductivity type body regions form an ohmic contact, and the anode metal and the surface contact area of ​​the first conductivity type drift region form a Schottky contact; The first conductivity type drift region includes a third region, a second region, and a first region stacked sequentially, wherein the first region is located on the side of the first conductivity type drift region closer to the anode metal; Wherein, the average doping concentration of the first region is greater than the minimum doping concentration of the second region; and the average doping concentration of the third region is greater than the minimum doping concentration of the second region.

[0030] Specifically, such as Figure 1 As shown in the embodiment of this application, a wide bandgap semiconductor hybrid PiN Schottky (MPS) diode with low on-resistance is proposed. The device structure, from bottom to top, includes: a cathode metal 1; a first conductivity type heavily doped substrate 2; a first conductivity type heavily doped buffer layer 3; a first conductivity type drift region 4; and a second conductivity type body region 5 (Schottky contact region) periodically alternating on the surface of the first conductivity type drift region 4 (the side surface facing away from the cathode metal 1). Here, the Schottky contact region is the area on the side surface of the first conductivity type drift region 4 facing away from the cathode metal 1 that is not covered by the second conductivity type body region 5. An anode metal 6 covers the second conductivity type body region 5 and the first conductivity type drift region 4.

[0031] The surface of the second conductive type body region 5 near the anode metal 6 is located in the same plane as the surface of the first region 401 near the anode metal 6, together forming a smooth and flat surface. The surface contact area between the anode metal 6 and the second conductive type body region 5 forms an ohmic contact (as an ohmic contact area), and the surface contact area between the anode metal 6 and the first conductive type drift region 4 forms a Schottky contact (as a Schottky contact area).

[0032] The first conductivity type drift region 4 has a non-monotonic U-shaped doping distribution along the longitudinal depth direction (from the anode metal 6 to the cathode metal 1), comprising a first region 401 at the top, a third region 403 at the bottom, and a second region 402 in between. In this embodiment, the U-shaped doping distribution means that the doping concentration at the top and bottom is generally greater than the doping concentration in the middle region along the longitudinal depth, thus forming an approximately U-shaped doping distribution. Let the average doping concentration of the first region 401 be N1, the lowest doping concentration of the second region 402 be Nmid, and the average doping concentration of the third region 403 be N3; the U-shaped doping distribution satisfies N1>Nmid and N3>Nmid.

[0033] In some embodiments, the average doping concentration N1 of the first region 401 is greater than the average doping concentration of the second region 402; and the average doping concentration N3 of the third region 403 is greater than the average doping concentration of the second region 402.

[0034] In some embodiments, the U-shaped doping distribution can be a strictly monotonically decreasing U-shaped doping distribution, i.e., the doping concentration first monotonically decreases from the surface to the interior of the drift region, and then monotonically increases; or, the U-shaped doping distribution can be a non-strictly monotonically increasing U-shaped doping distribution, i.e., local non-monotonic fluctuations in doping concentration are allowed within the second region due to epitaxial process tolerances, i.e., the doping concentration of some sub-regions within the second region can be higher than or equal to the doping concentration of adjacent sub-regions within the second region, or higher than the doping concentration of the first region near the boundary of the second region, or the doping concentration of the third region near the boundary of the second region; however, in the global distribution, the highest doping concentration at the top of the first region and the highest doping concentration at the bottom of the third region are both significantly greater than the lowest doping concentration within the second region.

[0035] In some embodiments, the doping concentration curve of the first conductivity type drift region along the depth direction exhibits a U-shaped distribution characteristic that first decreases and then increases from the anode side downwards.

[0036] In some embodiments, the average doping concentration of the first region and the average doping concentration of the third region may be the same or different. There is no strict limitation on the doping concentration of the first region and the third region. If the thickness of one of the layers is designed to be thin, the corresponding doping concentration increases; if the thickness of one of the layers is designed to be thick, the corresponding doping concentration decreases.

[0037] In some embodiments, the first conductivity type drift region 4 may be further divided into a greater number of stacked regions, or the second region may be divided into multiple stacked sub-regions, wherein at least one sub-region has the lowest doping concentration Nmid in the entire first conductivity type drift region 4, that is, the minimum doping concentration in the first conductivity type drift region 4 is located in the second region.

[0038] Reference Figure 2 , Figure 2 A schematic diagram of another Schottky diode structure is shown, such as... Figure 2 As shown, the second region 402 is divided into a middle low-doped layer 402-1 and a transition layer 402-2; the N-drift region (first conductivity type drift region 4) is composed of multiple N-type epitaxial layers with different doping concentrations stacked from bottom to top, including: a bottom N3 layer (third region 403), a transition N2 layer (as shown in the figure), and a transition N2 layer (as shown in the figure). Figure 2 The 402-2 shown), the middle low-doped Nmid layer ( Figure 2 As shown in Figure 402-1, it has a minimum doping concentration (Nmid) and a top N1 layer (first region 401). The top N1 layer (first region 401) is located at the top and laterally surrounds the P+ type body region (second conductivity type body region 5).

[0039] like Figure 2 As shown, a P+ type body region (second conductivity type body region 5) is embedded locally in the top of the first conductivity type drift region 4, and the anode metal 6 covers the N- drift region (first conductivity type drift region 4) and the P+ type body region (second conductivity type body region 5). The anode metal 6 forms an ohmic contact with the P+ type body region (second conductivity type body region 5) and a Schottky contact with the top surface of the N- drift region (first conductivity type drift region 4).

[0040] The first conductivity type drift region 4 exhibits a U-shaped envelope distribution in the vertical direction, characterized by a low concentration in the middle and high concentrations at both ends. Specifically, the doping concentration of the first region 401 is greater than that of the middle low-doped layer 402-1, and the doping concentration of the third region 403 is also greater than that of the middle low-doped layer 402-1. The average doping concentration of the first region 401 is N1, the lowest doping concentration of the middle low-doped layer 402-1 is Nmid, and the average doping concentration of the third region 403 is N3; the U-shaped doping distribution satisfies N1>Nmid and N3>Nmid.

[0041] Further, the average doping concentration of the middle low-doped layer 402-1 is less than the average doping concentration of the transition layer 402-2, the average doping concentration of the transition layer 402-2 is less than the average doping concentration of the first region 401, and the average doping concentration of the transition layer 402-2 is less than the average doping concentration of the third region 403.

[0042] Specifically, in the longitudinal doping distribution, the doping concentrations of the above-mentioned epitaxial layers also strictly satisfy the non-monotonic distribution law: Nmid (the lowest doping concentration) < N2 (the average doping concentration of the transition layer 402) < N3 (the average doping concentration of the third region) and Nmid (the lowest doping concentration) < N1 (the average doping concentration of the first region). By introducing the transition layer 402-2, a smoother "quasi-U-shaped envelope feature with low doping in the middle and increasing doping concentrations towards both ends" is constructed in the vertical direction of the first-conductivity-type drift region 4.

[0043] It should be noted that the device structure shown in the embodiments and drawings of the present application is only a cross-sectional schematic diagram of the core active region basic unit (i.e., the cell) of the wide-bandgap semiconductor hybrid PiN Schottky diode. In the actual manufacturing and application of power semiconductor devices, in order to suppress the electric field concentration effect at the cutting edge of the device, prevent premature avalanche breakdown at the edge, and fully utilize the blocking potential of the present application, an edge junction termination protection structure is usually surrounded outside the active region. The edge junction termination protection structure can adopt conventional designs in the art including but not limited to floating guard rings (FGR), junction termination extension (JTE), or field plates. The core innovation of the present application lies in the joint optimization of the longitudinal doping distribution inside the active region and the surface body region, and the specific form of the above-mentioned edge junction termination protection structure does not constitute a limitation to the protection scope of the present application.

[0044] In this embodiment, the thickness and concentration of the transition layer 402-2 can be adjusted, omitted, or equivalently replaced with multiple ultra-thin epitaxial layers with gradually changing concentrations, or a U-shaped non-linear approximation can be performed to fit the curve of the doping concentration decreasing first and then increasing according to the actual electric field smoothing requirements.

[0045] The embodiments of the present application provide a wide-bandgap semiconductor hybrid PiN Schottky (MPS) diode device that breaks through the traditional one-dimensional unipolar theory limit and has a low on-resistance. Under the same breakdown voltage level, the specific on-resistance can be reduced by about 10% compared with traditional uniformly doped devices. Specifically, the Schottky diode proposed in the embodiments of the present application has the following beneficial effects: 1. Precise control of avalanche integral for excellent reverse breakdown voltage: This embodiment reconstructs the internal electric field distribution under reverse bias by constructing a U-shaped doping distribution in the drift region (the first conductivity type drift region includes a first region, a second region, and a third region stacked together; wherein the average doping concentration of the first region is greater than the lowest doping concentration of the second region; and the average doping concentration of the third region is greater than the lowest doping concentration of the second region). Although the high doping at the top (first region) makes the surface peak electric field slightly higher than that of a conventional uniformly doped structure, the electric field decreases sharply with depth due to the extremely thin layer, and the high-risk area of ​​avalanche integral is quickly suppressed, failing to reach the critical integral condition for avalanche breakdown caused by impact ionization; combined with the low-doped second region in the middle for main voltage division, the device's excellent high-voltage blocking capability (1200V level) is ensured.

[0046] 2. Breaking the theoretical limits of one-dimensional unipolar transistors and significantly reducing specific on-resistance: This application's embodiments specifically optimize the local resistance of the drift region. First, the top N1 highly doped layer (first region) effectively reduces the junction field-effect transistor (JFET) effect and localized resistance spread caused by the depletion layer of the P+ type body region. Second, the region where the bottom N3 layer (third region) is located contributes almost nothing to the reverse avalanche integral. This application's embodiments significantly increase the doping concentration in this region, greatly reducing the deep body resistance without sacrificing the device's breakdown voltage. Under the same breakdown voltage design constraints, the U-shaped stepped doped structure proposed in this application only changes the reverse breakdown voltage from 1175V to 1162V, a decrease of approximately 1.1%, resulting in a significant reduction of the device's specific on-resistance of 12.38%, and an improvement of the device's absolute on-current capability at a 2.0V forward bias of 14.7%.

[0047] 3. Suppressing Schottky interface leakage current and possessing high process compatibility: The embodiments of this application utilize the depletion layer pinch-off effect of the periodic P+ type body region (second conductivity type body region 4) under reverse bias to effectively shield the electric field of the surface Schottky contact and suppress reverse leakage current; at the same time, for different wide bandgap material characteristics, a dual-track fabrication scheme supporting high-energy ion implantation of silicon carbide (SiC) and secondary epitaxy by gallium nitride (GaN) etching is provided, overcoming process bottlenecks and possessing extremely high industrial transformation feasibility.

[0048] In some embodiments, the minimum doping concentration of the second region is Nmid; The first region is the area in the first conductivity type drift region that extends downwards from the surface of the first conductivity type drift region near the anode metal until the doping concentration first drops to 1.2 Nmid; The thickness of the first region is greater than or equal to the thickness of the second conductive type body region, and the surface of the second conductive type body region facing away from the anode metal is in contact with the first region.

[0049] In this embodiment, the physical depth definition and thickness relationship of the first region 401 are as follows: Let the junction depth of the second conductivity type body region 5 downward from the surface of the first conductivity type drift region 4 be DP+, that is, the film thickness of the second conductivity type body region 5. The depth range from the surface of the first conductivity type drift region 4 downward (from the direction of the anode metal 6 to the cathode metal 1) until the doping concentration first drops to 1.2 Nmid is the first region 401, and its longitudinal thickness is T1; that is, the minimum doping concentration in the first conductivity type drift region 3 is Nmid, while the doping concentration in the first region is greater than or equal to 1.2 Nmid.

[0050] The thickness T1 of the first region 401 satisfies the relationship: T1>DP+, meaning the first region 401 extends downwards below the bottom of the second conductivity type body region 4. That is, as... Figure 1 As shown, the thickness of the first region 401 is greater than or equal to the thickness of the second conductive type body region 5, and the surface of the second conductive type body region 5 facing away from the anode metal 6 is in contact with the first region 401.

[0051] In some embodiments, the thickness of the first region is 1.5 to 4.0 times the thickness of the second conductive body region, including endpoint values ​​and reasonable deviations due to process variations, wherein the second conductive body region is completely embedded within the first region in the longitudinal direction.

[0052] Specifically, the thickness T1 of the first region 401 is 1.5 to 4 times the thickness DP+ of the second conductive type body region 5.

[0053] In some embodiments, the first region is divided into an upper first region layer and a lower first region layer from top to bottom along the longitudinal depth; Wherein, the thickness of the upper layer of the first region is less than the thickness of the second conductivity type body region; the average doping concentration of the upper layer of the first region is greater than or equal to three times the lowest doping concentration of the second region; the average doping concentration of the lower layer of the first region is less than the average doping concentration of the upper layer of the first region, and greater than the lowest doping concentration of the second region.

[0054] Specifically, to obtain a better current spreading layer, the first region 401 can be divided into two layers again, that is, the first region is divided into an upper layer and a lower layer along the vertical depth from top to bottom (i.e., two layers are stacked). Among them, the thickness of the upper layer of the first region 401 (the layer closer to the anode metal) is less than the thickness DP+ of the second conductivity type body region 5, and the doping concentration is at least 3 times Nmid (the minimum doping concentration); the doping concentration of the lower layer of the first region 401 (the layer further away from the anode metal) is between that of the upper layer and Nmid.

[0055] In some embodiments, the ratio (N1 / Nmid) between the average doping concentration of the first region and the average doping concentration of the second region is greater than or equal to 1.5 and less than or equal to 5.0. The ratio (N3 / Nmid) between the average doping concentration of the third region and the average doping concentration of the second region is greater than or equal to 1.5 and less than or equal to 7.0.

[0056] In some embodiments, the depth of the second region accounts for more than or equal to 65% and less than or equal to 85% of the total depth of the first conductivity type drift region.

[0057] In this embodiment, for MPS device designs with the same reverse breakdown voltage constraint, the average doping concentration of the second region 402 is lower than the drift region doping concentration of a uniformly doped MPS device. In other words, under the premise of equal reverse breakdown voltage, the average doping concentration of the U-shaped doped second region 402 proposed in this embodiment is 70% to 90% of the uniform doping concentration of conventional devices, and the concentration gradient of the second region 402 is approximately 0, and the second region 402 accounts for 65%-85% of the total thickness of the drift region. For example, a conventional silicon carbide MPS device rated for 1200V breakdown voltage has a drift region doping concentration of 1... Therefore, the diode proposed in the corresponding embodiment of this application, under a voltage rating of 1200V, has a doping concentration in the drift region (i.e., the average doping concentration of the second region 402) of 0.70. Up to 0.90 .

[0058] Furthermore, when the second region is divided into multiple stacked sub-regions, the average doping concentration of the sub-region 402-1 with the lowest doping concentration is 70% to 90% of the uniform doping concentration of conventional devices, and the concentration gradient of the sub-region 402-1 is approximately 0, and the thickness of the sub-region 402-1 accounts for 65% to 85% of the total thickness of the drift region.

[0059] In this embodiment, the surface charge can be used to measure the doping design: Where Q is the integral surface charge density of the region, T is the longitudinal thickness of the region, and N(x) is the doping concentration distribution function (from position 0 to position T) varying with depth x. The relationship between the change in electric field intensity and the surface charge is also given. ,in, Let q be the change in electric field intensity within this region, and q be the elementary charge. The dielectric constant of the wide bandgap semiconductor material is given. This method can be applied to third-generation wide bandgap semiconductors such as gallium nitride and silicon carbide, and all fall within the scope of this application.

[0060] In some embodiments, the integral surface charge density of the first conductivity type donor impurity in the first region is calculated using the following formula: ,in, The integral surface charge density of the first region; The thickness of the first region is N(x); N(x) is the doping concentration distribution function at a depth x, starting from the surface position of the first conductivity type drift region near the anode metal side as the starting point 0. Integral surface charge density of donor impurities of the first conductivity type in the first region The range of values ​​for satisfies: .

[0061] Specifically, this range ( The range of resistance is the physical range for suppressing the JFET squeeze effect, reducing the specific on-resistance (lower constraint limit), and preventing surface electric field breakdown (upper constraint limit). It is relatively independent of the device's macroscopic breakdown voltage constraint, as the main breakdown voltage is achieved in the second region 402.

[0062] In some embodiments, the minimum doping concentration of the second region is Nmid; The third region is the region in the first conductivity type drift region that extends upwards from the surface of the first conductivity type drift region near the cathode metal until the doping concentration first drops to 1.2 Nmid; The integral surface charge density of the first conductivity type donor impurity in the third region The range of values ​​for satisfies: , in, The total thickness of the drift region of the first conductivity type; Let N(x) be the thickness of the third region, and let N(x) be the doping concentration distribution function at depth x, starting from the surface position of the first conductivity type drift region near the anode metal side as the starting point 0. The integral surface charge density of the first conductivity type donor impurity in the third region The range of values ​​for satisfies: .

[0063] Specifically, this range ( The avalanche integral of the depletion layer has been largely exhausted, allowing for a rapid increase in doping concentration. Therefore, it is necessary to rapidly decay the electric field of the depletion layer and to constrain the concentration increase by the upper limit of the n+ layer.

[0064] In some embodiments, when the second region 402 comprises multiple stacked sub-regions, the surface charge of the sub-region 402-1 with the lowest doping concentration in the second region 402 is related to the breakdown voltage level and cannot be directly measured by surface charge. Therefore, the doping concentration Nmid of the sub-region 402-1 is made to satisfy: Nmid ≤ 0.6 × the highest doping concentration in the first region; and Nmid ≤ 0.6 × the highest doping concentration in the third region; The absolute thickness and surface charge of sub-region 402-1 are determined by the specific voltage rating of the target device (e.g., 1200V or 3300V).

[0065] In some embodiments, the materials of the first conductivity type heavily doped substrate and the first conductivity type drift region are selected from silicon carbide, gallium nitride, gallium oxide, aluminum nitride, or diamond.

[0066] In this embodiment, the first conductivity type heavily doped substrate and the first conductivity type drift region are made of the same material.

[0067] In some embodiments, the doping concentration of the second conductivity type body region is greater than or equal to and less than or equal to .

[0068] In some embodiments, the width ratio K between the second conductive body region and the adjacent Schottky contact region is greater than or equal to 0.5 and less than or equal to 2.0.

[0069] In this embodiment, the Schottky contact area refers to the contact area between the first conductivity type drift region and the anode metal; adjacent Schottky contact areas refer to the Schottky contact areas between two adjacent second conductivity type body regions. The width ratio refers to the ratio of the width of the second conductivity type body region to the width of the adjacent Schottky contact area along the same direction.

[0070] The device consists of multiple repeating basic units (cells) connected in parallel, each basic unit containing a volume region of a second conductivity type, such as... Figure 1 As shown, Figure 1A schematic diagram of a basic unit is shown, in which the volume regions of all basic units are arranged according to a fixed repeating pattern. The first direction is perpendicular to the length direction of the second conductivity type volume region. The width ratio refers to the ratio of the width of the second conductivity type volume region to the width of the adjacent Schottky contact region along the first direction. The width ratio can also be understood as the ratio of the projected area of ​​the second conductivity type volume region on the cathode metal layer in a single cell to the projected area of ​​the Schottky contact region in the original cell on the cathode metal layer.

[0071] For example, the film thickness of the heavily doped substrate 2 of the first conductivity type is 50-500 μm, and the doping concentration is 1e. 18 cm -3 -1e 19 cm -3 The thickness of the first conductivity type heavily doped buffer layer 3 is 0.5-1 μm, and the doping concentration is 1e. 18 cm -3 -1e 19 cm -3 The total thickness of the drift region 4, of the first conductivity type, is 5-10 μm; the junction depth (thickness) of the body region 5, of the second conductivity type, is 0.2-0.5 μm, and the doping concentration is 1e. 17 cm -3 -1e 19 cm -3 The thickness of the first region 401 is 0.2-0.5 μm.

[0072] Specifically, the overall doping concentration of the first conductivity type drift region 4 in the vertical direction exhibits a U-shaped envelope distribution characteristic, with a low concentration in the middle and high concentrations at both ends. The physical mechanism of this design is as follows: the first region 401, with its higher carrier concentration, can effectively weaken the JFET squeezing effect caused by the expansion of the depletion layer below the second conductivity type body region 5 into the N-channel during forward conduction. This allows the current in the device to expand more rapidly into the interior through the Schottky contact surface during the initial turn-on phase, thereby significantly reducing the spread resistance. Simultaneously, the presence of the third region 403 makes the electric field distribution more gradual in the region near the substrate, preventing premature electric field penetration during high-voltage interruption. In this embodiment, the cathode metal 1 can be made of a Ti / Al / Ni / Au system, and the anode metal 6 can be made of a Ni / Au system.

[0073] Reference Figure 3 , Figure 3 A schematic diagram of doping is shown for a U-shaped doped device and a uniformly doped device under the same breakdown voltage constraint, as follows. Figure 3As shown, the horizontal axis represents depth from the surface, and the vertical axis represents doping concentration. It demonstrates the accurate fit between the multilayer epitaxial stepped doping (solid line) and the ideal U-shaped envelope (dashed line). Compared with the traditional uniform doping structure (dotted line), this invention has a higher doping concentration at both ends of the drift region.

[0074] Figure 4 This diagram illustrates a comparison of the forward conduction curves of this application with those of a conventionally uniformly doped diode, specifically a simulation result of the diode's forward output characteristics using Technology Computer-Aided Design (TCAD). Figure 4 As shown, the horizontal axis represents anode voltage, and the vertical axis represents anode current. The solid line represents a multilayer epitaxial stepped doping design, and the dashed line represents the ideal U-shaped envelope. Under the same cell design constraints, the conventional uniformly doped structure has a device specific on-resistance of approximately 3.66 mΩ·cm in the linear region from 1.5V to 2.0V. 2 By adopting the U-shaped step-doped structure proposed in this application, the high-concentration N1 layer (first region 401) significantly suppresses the JFET effect, resulting in a reduction of the specific on-resistance to approximately 3.20 mΩ·cm over the same voltage range. 2 The conductivity was significantly improved by approximately 12.4%.

[0075] Figure 5 This diagram illustrates a comparison of the reverse blocking characteristic curves of the diode device of this application and a conventional uniformly doped device. Specifically, it compares the TCAD simulation results of the leakage current density-voltage (JV) characteristic curves of the diode device of this application and the conventional uniformly doped device under reverse bias. Figure 5 As shown, the horizontal axis represents reverse voltage, and the vertical axis represents reverse current density. The solid line represents a multilayer epitaxial stepped doping design, and the dashed line represents the ideal U-shaped envelope. For high-voltage power devices, improving conduction performance often severely sacrifices blocking voltage performance. Simulation results show that the avalanche breakdown voltage of the traditional uniformly doped structure is approximately 1175 V, while the avalanche breakdown voltage of the device structure proposed in this application remains at approximately 1162 V. This indicates that while achieving a significant improvement in forward conduction capability, this application only causes a minor loss of approximately 1.1% in the reverse breakdown voltage, still firmly meeting the design threshold of 1200V-level power devices, successfully breaking the inherent trade-off bottleneck between specific on-resistance and breakdown voltage in traditional uniformly doped MPS devices.

[0076] This application proposes a U-shaped doping distribution design for a Schottky diode. Specifically, the first conductivity type drift region comprises at least three epitaxial layers of the first conductivity type with different doping densities. The discrete envelopes of the concentrations of each layer constitute the U-shaped doping distribution, which can be summarized into a first region with higher doping, a third region, and a second region with lower doping. Specifically, the Schottky diode proposed in this application has the following beneficial effects: Precise control of avalanche integration achieves excellent reverse breakdown voltage: This embodiment reconstructs the internal electric field distribution under reverse bias by constructing a U-shaped doping distribution in the drift region (the first conductivity type drift region includes a first region, a second region, and a third region stacked together; wherein the average doping concentration of the first region is greater than the lowest doping concentration of the second region; and the average doping concentration of the third region is greater than the lowest doping concentration of the second region). Although the high doping at the top (first region) results in a slightly higher peak surface electric field than traditional uniformly doped structures, the electric field decreases sharply with depth due to the extremely thin layer. The high-risk region for avalanche integration is rapidly suppressed, failing to reach the critical integration condition for avalanche breakdown caused by impact ionization. Combined with the low-doped second region in the middle for primary voltage division, this ensures the device's excellent high-voltage blocking capability (1200V level).

[0077] Breaking the theoretical limits of one-dimensional unipolar transistors and significantly reducing specific on-resistance: This application's embodiments specifically optimize the local resistance of the drift region. First, the top N1 highly doped layer (first region) effectively reduces the junction field-effect transistor (JFET) effect and localized resistance spread caused by the depletion layer of the P+ type body region. Second, the region where the bottom N3 layer (third region) is located contributes almost nothing to the reverse avalanche integral. This application's embodiments significantly increase the doping concentration in this region, greatly reducing the deep body resistance without sacrificing the device's breakdown voltage. Under the same breakdown voltage design constraints, the U-shaped stepped doped structure proposed in this application only changes the reverse breakdown voltage from 1175V to 1162V, a decrease of approximately 1.1%, resulting in a significant reduction of the device's specific on-resistance of 12.38% and an improvement of the device's absolute on-current capability at a 2.0V forward bias of 14.7%.

[0078] Suppressing Schottky interface leakage current and possessing high process compatibility: This application embodiment utilizes the depletion layer pinch-off effect of the periodic P+ type body region (second conductivity type body region 4) under reverse bias to effectively shield the surface Schottky contact with electric field, suppressing reverse leakage current; at the same time, for different wide bandgap material characteristics, it provides a dual-track fabrication scheme that supports high-energy ion implantation of silicon carbide (SiC) and secondary epitaxy by gallium nitride (GaN) etching, overcoming process bottlenecks and possessing extremely high industrial transformation feasibility.

[0079] The second aspect of this application also provides a method for fabricating a wide-bandgap semiconductor hybrid PiN Schottky diode, applied to the fabrication of the Schottky diode described in the first aspect of this application, with reference to... Figure 6 , Figure 6 A flowchart illustrating the steps involved in fabricating a wide-bandgap semiconductor hybrid PiN Schottky diode is shown, as follows: Figure 6 As shown, the method includes: Step S101: Provide a wide bandgap semiconductor substrate heavily doped with a first conductivity type to obtain a heavily doped substrate with the first conductivity type; Step S102: Using a multilayer continuous epitaxial growth process, a first conductivity type heavily doped buffer layer is grown on one side of the first conductivity type heavily doped substrate, and then a first conductivity type drift region is grown. During the growth of the first conductivity type drift region, the flow rate of the donor impurity source gas is nonlinearly adjusted to form a stacked first region, a second region, and a third region. The average doping concentration of the first region is greater than the minimum doping concentration of the second region, and the average doping concentration of the third region is greater than the minimum doping concentration of the second region (i.e., a vertical non-monotonic U-shaped doping distribution is formed). Step S103: Prepare a second conductivity type volume region on the surface of the first conductivity type drift region after growth; Step S104: Prepare cathode metal on the side surface of the first conductivity type heavily doped substrate away from the first conductivity type drift region; specifically, the cathode metal can be deposited and annealed on the back side of the substrate.

[0080] Step S105: Prepare anode metal on the surface of the second conductivity type body region facing away from the first conductivity type drift region. Specifically, metal can be deposited and patterned on the front side of the drift region to form anode metal covering the second conductivity type body region and the adjacent first conductivity type Schottky contact region.

[0081] In some embodiments, step S103, which involves preparing a second conductivity type volume region on the surface of the grown first conductivity type drift region, includes: Step S103-1: Deposit a mask layer on the surface of the drift region of the first conductivity type (the surface facing away from the heavily doped substrate of the first conductivity type) after growth and perform photolithographic patterning. Step S103-2: Using a multi-energy ion implantation process, a second conductivity type impurity is implanted. After high-temperature annealing and activation, a periodically arranged second conductivity type body region is formed on the surface of the first conductivity type drift region.

[0082] Implementation Method 1: Applicable to material systems such as silicon carbide (SiC) that support efficient ion implantation, including the following steps. Step 1: Provide an N+ type substrate (heavily doped substrate 2 of the first conductivity type), and sequentially perform multilayer epitaxial growth on it, forming a heavily doped buffer layer (3), a bottom N3 layer (third region 403), and a transition N2 layer (e.g., from bottom to top) from bottom to top. Figure 2 The transition layer 402-2), the middle low-doped Nmid layer (such as Figure 2 Step 1: The middle low-doped layer 402-1 and the top N1 layer (first region 401) together constitute the N- drift region (first conductivity type drift region 4); Step 2: Deposit a mask layer (such as SiO2) on the surface of the epitaxial wafer, and use photolithography to define the P+ implantation region window; Step 3: Use the mask layer as a barrier layer to perform multiple high-energy ion implantations of P-type impurities (such as aluminum ions), and the implantation depth penetrates to the designated position to form a P+ type body region (second conductivity type body region 4); Step 4: Remove the mask layer and perform a high-temperature annealing process to activate the implanted P-type impurities and repair lattice damage; Step 5: Use electron beam evaporation to form cathode metal 1 on the back side and perform annealing; Step 6: Use photolithography and electron beam evaporation processes to deposit anode metal 6 on the front side, so that it forms an ohmic contact with the P+ type body region (second conductivity type body region 5), and at the same time forms a Schottky contact with the top N1 layer (first region 401).

[0083] In some embodiments, step S103, which involves preparing a second conductivity type volume region on the surface of the grown first conductivity type drift region, includes: Step S103-3: Deposit a mask layer on the surface of the epitaxial wafer, and use photolithography and dry etching processes to etch downwards through part or all of the first region to form a periodic trench structure. Step S103-4: Using a selective area secondary epitaxial growth process, a second conductivity type epitaxial layer is epitaxially grown inside the trench to form a second conductivity type body region; Step S103-5: Remove excess epitaxial material from the mask layer and overflow trenches to make the upper surface of the second conductive type body region flush with the surface of the drift region.

[0084] Implementation Method 2: For material systems where gallium nitride (GaN) plasmonic implantation activation is difficult, the following steps are included. Step 1: Provide an N+ type substrate (heavily doped substrate 2 of the first conductivity type), and sequentially perform multilayer epitaxial growth on it, forming a heavily doped buffer layer (3), a bottom N3 layer (third region 403), and a transition N2 layer (e.g., ...) from bottom to top. Figure 2 The transition layer 402-2), the middle low-doped Nmid layer (such as...) Figure 2 Step 1: The middle low-doped layer 402-1 and the top N1 layer (first region 401) together constitute the N-drift region (first conductivity type drift region 4); Step 2: Deposit a mask layer (such as SiO2) on the surface of the epitaxial wafer, and use photolithography and ICP etching to etch downwards through part or all of the top N1 layer (401) to form a periodic trench structure; Step 3: Use MOCVD selected area secondary epitaxial process to epitaxially grow a highly doped P-GaN layer inside the trench to form a P+ type body region (second conductivity type body region 5); Step 4: Use chemical mechanical polishing (CMP) or dry etching retreat process to remove the mask layer and excess P-GaN overflowing the trench, so that the upper surface of the P+ type body region (second conductivity type body region 5) is flush with the top N1 layer (first region 401); Step 5: Use electron beam evaporation process to form cathode metal 1 on the back side and anneal it; Step 6: Using photolithography and electron beam evaporation processes, deposit anode metal 6 on the flat surface of the front side, so that it forms an ohmic contact with the epitaxially grown P+ type body region (second conductivity type body region 5), and at the same time forms a Schottky contact with the top N1 layer (first region 401).

[0085] This application discloses a wide-bandgap semiconductor hybrid PiN Schottky (MPS) diode and its fabrication method. The device structure, from bottom to top, includes a cathode metal, a heavily doped substrate of a first conductivity type, a drift region of the first conductivity type, and a second conductivity type body region arranged periodically and alternately on the surface of the drift region, with an anode metal covering the top. The drift region exhibits a continuous or stepped non-monotonic U-shaped doping distribution along its longitudinal depth; that is, the doping concentration at the top (first region) and bottom (third region) of the drift region is significantly higher than the lowest doping concentration in the middle main breakdown voltage region (i.e., the second region). This U-shaped drift region can be dynamically controlled by adjusting the impurity flow rate through a multilayer continuous epitaxial growth process, while the surface body region is formed by ion implantation. This application utilizes the highly nonlinear impact ionization rate characteristics of wide-bandgap semiconductors. During reverse blocking, the high doping at the top induces a steep surface electric field gradient, greatly compressing the avalanche generation region spatially. Combined with the field termination effect at the bottom, this reshapes the global electric field distribution of the device. During forward conduction, the high doping at the top effectively suppresses the expansion of the depletion layer in the body region into the conductive channel, greatly enhancing the two-dimensional current expansion capability. It breaks through the theoretical limit of classical monotonic doping distribution and significantly reduces the specific on-resistance of the device while maintaining the target breakdown voltage.

[0086] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0087] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0088] The foregoing has provided a detailed description of a wide-bandgap semiconductor hybrid PiN Schottky diode and its fabrication method. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0089] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0090] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0091] The terms "an embodiment," "embodiment," or "one or more embodiments" as used herein mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of this application. Furthermore, please note that the examples of the phrase "in one embodiment" do not necessarily all refer to the same embodiment.

[0092] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0093] In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A wide-bandgap semiconductor hybrid PiN Schottky diode, characterized in that, The diode comprises, in sequence, a cathode metal, a heavily doped substrate of a first conductivity type, a heavily doped buffer layer of a first conductivity type, a drift region of a first conductivity type, a body region of a second conductivity type, and an anode metal; The second conductivity type body regions are periodically arranged on the side surface of the first conductivity type drift region away from the cathode metal; the anode metal and the surface contact area of ​​the second conductivity type body regions form an ohmic contact, and the anode metal and the surface contact area of ​​the first conductivity type drift region form a Schottky contact; The first conductivity type drift region includes a third region, a second region, and a first region stacked sequentially, wherein the first region is located on the side of the first conductivity type drift region closer to the anode metal; Wherein, the average doping concentration of the first region is greater than the minimum doping concentration of the second region; and the average doping concentration of the third region is greater than the minimum doping concentration of the second region.

2. The Schottky diode according to claim 1, characterized in that, The minimum doping concentration in the second region is Nmid; The first region is the area in the first conductivity type drift region that extends downwards from the surface of the first conductivity type drift region near the anode metal until the doping concentration first drops to 1.2 Nmid; The thickness of the first region is greater than or equal to the thickness of the second conductive type body region, and the surface of the second conductive type body region facing away from the anode metal is in contact with the first region.

3. The Schottky diode according to claim 2, characterized in that, The thickness of the first region is 1.5 to 4.0 times the thickness of the second conductive type body region, and the second conductive type body region is completely embedded in the first region in the longitudinal direction.

4. The Schottky diode according to claim 1, characterized in that, The first region is divided into an upper layer and a lower layer along the longitudinal depth from top to bottom; Wherein, the thickness of the upper layer of the first region is less than the thickness of the second conductivity type body region; the average doping concentration of the upper layer of the first region is greater than or equal to three times the lowest doping concentration of the second region; the average doping concentration of the lower layer of the first region is less than the average doping concentration of the upper layer of the first region, and greater than the lowest doping concentration of the second region.

5. The Schottky diode according to claim 1, characterized in that, The ratio between the average doping concentration of the first region and the average doping concentration of the second region is greater than or equal to 1.5 and less than or equal to 5.0; The ratio between the average doping concentration of the third region and the average doping concentration of the second region is greater than or equal to 1.5 and less than or equal to 7.

0.

6. The Schottky diode according to claim 1, characterized in that, The depth of the second region accounts for more than or equal to 65% and less than or equal to 85% of the total depth of the first conductivity type drift region.

7. The Schottky diode according to claim 1, characterized in that, The formula for calculating the integral surface charge density of donor impurities of the first conductivity type in the first region is as follows: ,in, The integral surface charge density of the first region; The thickness of the first region is N(x); N(x) is the doping concentration distribution function at a depth x, starting from the surface position of the first conductivity type drift region near the anode metal side as the starting point 0. Integral surface charge density of donor impurities of the first conductivity type in the first region The range of values ​​for satisfies: .

8. The Schottky diode according to claim 1, characterized in that, The minimum doping concentration in the second region is Nmid; The third region is the region in the first conductivity type drift region that extends upwards from the surface of the first conductivity type drift region near the cathode metal until the doping concentration first drops to 1.2 Nmid; The integral surface charge density of the first conductivity type donor impurity in the third region The range of values ​​for satisfies: ， in, The total thickness of the drift region of the first conductivity type; Let N(x) be the thickness of the third region, and let N(x) be the doping concentration distribution function at depth x, starting from the surface position of the first conductivity type drift region near the anode metal side as the starting point 0. The integral surface charge density of the first conductivity type donor impurity in the third region The range of values ​​for satisfies: 。 9. The Schottky diode according to claim 1, characterized in that, The first conductivity type drift region exhibits a U-shaped distribution characteristic along the depth direction, with the doping concentration curve first decreasing and then increasing from the anode side downwards.

10. A method for fabricating a wide-bandgap semiconductor hybrid PiN Schottky diode, characterized in that, The method is applied to the fabrication of a Schottky diode according to any one of claims 1-9, the method comprising: A wide-bandgap semiconductor substrate heavily doped with a first conductivity type is provided to obtain a heavily doped substrate of the first conductivity type. A multilayer continuous epitaxial growth process is employed to grow a first conductivity type heavily doped buffer layer on one side of a first conductivity type heavily doped substrate, followed by the growth of a first conductivity type drift region. During the growth of the first conductivity type drift region, the flow rate of the donor impurity source gas is nonlinearly adjusted to form a stacked first region, a second region, and a third region. The average doping concentration of the first region is greater than the minimum doping concentration of the second region, and the average doping concentration of the third region is greater than the minimum doping concentration of the second region. A second conductivity type volume region is prepared on the surface of the first conductivity type drift region after growth; A cathode metal is prepared on the surface of the first conductivity type heavily doped substrate on the side away from the first conductivity type drift region. An anode metal is prepared on the surface of the second conductivity type body region on the side opposite to the first conductivity type drift region.

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