A Schottky diode and a method for preparing the same

Abstract

A Schottky diode and a preparation method thereof, the Schottky diode comprising: a semiconductor substrate layer; a drift layer located on the semiconductor substrate layer, the drift layer comprising a first drift region and a second drift region located on the side of the first drift region facing away from the semiconductor substrate layer, the doping concentration of the second drift region being greater than the doping concentration of the first drift region; a secondary doping layer located in part of the second drift region, the conductivity type of the secondary doping layer being opposite to the conductivity type of the drift layer; a plurality of main doping layers located in the drift layer and spaced around the secondary doping layer, the conductivity type of the main doping layer being the same as the conductivity type of the secondary doping layer. The Schottky diode ensures that the conduction channel is completely pinched off at a relatively small reverse bias, and at the same time can ensure that it has a low on-resistance when forward conducting.

Description

Technical Field

[0001] The invention relates to the field of semiconductors, and in particular to a Schottky diode and a preparation method thereof. Background Art

[0002] The power diode is one of the most commonly used electronic components and the most basic component unit of power electronic circuits. Its unidirectional conductivity can be used for rectification, clamping, and freewheeling of the circuit. The diode in the peripheral circuit mainly plays an anti-reverse role to prevent the current from backflowing and causing damage to the device. Traditional power diodes mainly include Schottky power diodes and PN junction power diodes. Compared with PN junction power diodes, Schottky power diodes use metal and semiconductor contact (gold semiconductor contact) to form a metal semiconductor junction, which makes its forward turn-on voltage smaller. Moreover, the Schottky power diode is a unipolar majority carrier conduction mechanism. Its reverse recovery time is ideally zero, and there is no accumulation of excess minority carriers.

[0003] However, for Schottky power diodes, there is a reasonable trade-off between complete pinch-off of the conduction channel at a relatively small reverse bias and low forward on-resistance, which, to a certain extent, limits the application of Schottky power diodes in the high voltage field. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the problem in the prior art that it is impossible to ensure both complete pinch-off of the conduction channel at a relatively small reverse bias voltage and low on-resistance during forward conduction.

[0005] In order to solve the above technical problems, the present invention provides a Schottky diode, comprising: a semiconductor substrate layer; a drift layer located on the semiconductor substrate layer, the drift layer comprising a first drift region and a second drift region located on a side of the first drift region facing away from the semiconductor substrate layer, the doping concentration of the second drift region being greater than the doping concentration of the first drift region; a sub-doped layer located in a portion of the second drift region, the conductivity type of the sub-doped layer being opposite to the conductivity type of the drift layer; and a plurality of main doped layers located in the drift layer and spaced around the sub-doped layers, the conductivity type of the main doped layers being the same as the conductivity type of the sub-doped layers.

[0006] Optionally, the doping concentration of the second drift region is 2 to 100 times the doping concentration of the first drift region.

[0007] Optionally, the ratio of the thickness of the second drift region to the thickness of the first drift region is 1 / 100 to 1 / 10.

[0008] Optionally, the doping concentration of the sub-doping layer is less than the doping concentration of the main doping layer.

[0009] Optionally, the doping concentration of the sub-doping layer is 5% to 80% of the doping concentration of the main doping layer.

[0010] Optionally, the surface area of ​​the sub-doping layer is 5% to 40% of the surface area of ​​the main doping layer.

[0011] Optionally, a longitudinal dimension of the sub-doping layer is 1 / 10 to 2 times the longitudinal dimension of the second drift region.

[0012] Optionally, the distances between the center of the sub-doping layer and the center of the adjacent main doping layer are equal.

[0013] Optionally, a surface shape of the sub-doped layer is the same as a surface shape of the main doped layer.

[0014] Optionally, the surface shape of the sub-doped layer includes a circle, a square, a rectangle or a hexagon; the surface shape of the main doped layer includes a circle, a square, a rectangle or a hexagon.

[0015] The present invention also provides a method for preparing a Schottky diode, comprising: providing a semiconductor substrate layer; forming a drift layer on the semiconductor substrate layer, the drift layer comprising a first drift region and a second drift region located on a side of the first drift region facing away from the semiconductor substrate layer, the doping concentration of the second drift region being greater than the doping concentration of the first drift region; forming a sub-doping layer in part of the second drift region, the conductivity type of the sub-doping layer being opposite to the conductivity type of the drift layer; forming a plurality of main doping layers in the drift layer, the plurality of main doping layers being spaced around the sub-doping layers, the conductivity type of the main doping layers being the same as the conductivity type of the sub-doping layers.

[0016] Optionally, the process of forming the sub-doping layer includes an ion implantation process.

[0017] Optionally, the method for forming the drift layer includes: forming an initial drift layer on the semiconductor substrate layer; and performing ion implantation on a partial thickness of the initial drift layer so that the initial drift layer forms the drift layer.

[0018] The technical method of the present invention has the following beneficial effects:

[0019] 1. The Schottky diode provided by the technical solution of the present invention has the following characteristics: for the adjacent main doping layers distributed along the circumferential direction of the secondary doping layer, under a certain reverse bias, the spatial depletion regions of the PN junctions formed by the adjacent main doping layers can overlap or contact. Due to the provision of the secondary doping layer, under a certain reverse bias, a spatial depletion region of the PN junction will also be formed between the secondary doping layer and the drift region. When the spatial depletion regions of the PN junctions formed by the adjacent main doping layers along the circumferential direction of the secondary doping layer just contact under the reverse bias, the spatial depletion region formed by the secondary doping layer and the drift region at least partially overlaps with the spatial depletion region formed by the main doping layer and the drift region. Therefore, the spatial depletion region formed by the secondary doping layer and the drift region and the spatial depletion region formed by the main doping layer and the drift region protect the Schottky contact region, so that the Schottky contact region is in more field protection ranges. Secondly, since the doping concentration of the second drift layer is greater than the doping concentration of the first drift layer, even if the area of ​​the secondary doping layer is slightly larger, the second drift layer with a higher doping concentration can compensate for the effect of the increase in the area of ​​the secondary doping layer on the channel resistance, so that the conduction channel resistance is lower. Since the area of ​​the secondary doping layer can be increased, when the spatial depletion regions of the PN junctions formed by the adjacent main doping layers in the circumferential direction of the secondary doping layer just touch under reverse bias, the spatial depletion region formed by the secondary doping layer and the drift region and the spatial depletion region formed by the main doping layer and the drift region also completely overlap with each other, and the spatial depletion region occupies the entire active area laterally, so that the spatial depletion region fully protects the Schottky contact region, so that the Schottky contact region is completely within the field protection range, ensuring that the Schottky diode can be completely turned off under a smaller reverse bias, and the leakage current of the Schottky diode is small. In summary, it is ensured that the Schottky diode can be completely turned off under a smaller reverse bias, and low on-resistance during forward conduction can also be ensured.

[0020] Secondly, as the PN junction depletes the conduction channel under reverse bias, a continuous space charge region without gaps can be formed, so that the Schottky diode has a reverse withstand voltage capability close to that of the PN diode. Since the doping concentration of the second drift layer is greater than that of the first drift layer, the Schottky diode can be precisely controlled to break down in the area where the secondary doping layer is located when reverse biased, and the breakdown is distributed in the entire active area rather than the field stop area, thereby improving the avalanche withstand of the Schottky diode.

[0021] 2. The method for preparing a Schottky diode provided by the technical solution of the present invention comprises forming a drift layer on the semiconductor substrate layer, the drift layer comprising a first drift region and a second drift region located on the side of the first drift region facing away from the semiconductor substrate layer, the doping concentration of the second drift region being greater than the doping concentration of the first drift region; forming a sub-doping layer in part of the second drift region; forming a plurality of main doping layers in the drift layer, the plurality of main doping layers being spaced around the sub-doping layer; the doping concentration of the sub-doping layer being less than the doping concentration of the main doping layer. Since the doping concentration of the second drift layer is greater than the doping concentration of the first drift layer, even if the area of ​​the sub-doping layer is slightly larger, the second drift layer with a higher doping concentration can compensate for the effect of the increase in the area of ​​the sub-doping layer on the channel resistance, so that the on-channel resistance is lower. Since the area of ​​the secondary doping layer can be increased, when the spatial depletion regions of the PN junctions formed by the adjacent main doping layers in the circumferential direction of the secondary doping layer just touch under reverse bias, the spatial depletion region formed by the secondary doping layer and the drift region and the spatial depletion region formed by the main doping layer and the drift region also completely overlap with each other, and the spatial depletion region occupies the entire active area laterally, so that the spatial depletion region fully protects the Schottky contact region, so that the Schottky contact region is completely within the field protection range, ensuring that the Schottky diode can be completely turned off under a smaller reverse bias, and the leakage current of the Schottky diode is small. In summary, it is ensured that the Schottky diode can be completely turned off under a smaller reverse bias, and low on-resistance during forward conduction can also be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are some implementations of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 A schematic diagram of the structure of a Schottky diode;

[0024] Figure 2 is a schematic structural diagram of a Schottky diode in one embodiment of the present invention;

[0025] Figure 3 yes Figure 2 A top view of the

[0026] Figure 4 is a top view of a main doping layer and a sub-doping layer in another embodiment of the present invention;

[0027] Figure 5 A top view of a main doping layer and a sub-doping layer in another embodiment of the present invention;

[0028] Figure 6 is a flow chart of a Schottky diode forming process in another embodiment of the present invention;

[0029] Figures 7 to 10 It is a structural schematic diagram of the process of forming a Schottky diode in one embodiment of the present invention. DETAILED DESCRIPTION

[0030] A Schottky diode, referring to the figure, comprises: a semiconductor substrate layer 10; a drift layer 11 located on the semiconductor substrate layer 10; a sub-doped layer 12 located in a portion of the drift region 11, wherein the conductivity type of the sub-doped layer 12 is opposite to that of the drift layer 11; and a plurality of main doped layers 13 located in the drift layer 11 and spaced around the sub-doped layer 12, wherein the conductivity type of the main doped layer 13 is the same as that of the sub-doped layer 12.

[0031] In the above-mentioned Schottky diode, the purpose of setting the secondary doping layer 12 is to make the space depletion region formed by the secondary doping layer and the drift region partially overlap with the space depletion region formed by the main doping layer and the drift region, and the space depletion region formed by the secondary doping layer and the drift region and the space depletion region formed by the main doping layer and the drift region protect the Schottky contact region, so that the Schottky contact region is in more field protection range. Usually, the secondary doping layer 12 has a smaller surface area, and the purpose of such setting is to increase the area of ​​the Schottky contact region, which can reduce the on-resistance, increase the current density, and improve the performance of the device.

[0032] However, since the surface area of ​​the secondary doping layer 12 is relatively small, when the spatial depletion regions of the PN junctions formed by the adjacent main doping layers in the circumferential direction of the secondary doping layer just touch each other under reverse bias, the spatial depletion region formed by the secondary doping layer and the drift region has not completely overlapped with the spatial depletion region formed by the main doping layer and the drift region, and there is a partial area in the drift region between the secondary doping layer 12 and the main doping layer where no spatial depletion layer is formed, which results in the Schottky diode being unable to be completely turned off under a smaller reverse bias.

[0033] On this basis, an embodiment of the present invention provides a Schottky diode, comprising: a semiconductor substrate layer; a drift layer located on the semiconductor substrate layer, the drift layer comprising a first drift region and a second drift region located on the side of the first drift region facing away from the semiconductor substrate layer, the doping concentration of the second drift region being greater than the doping concentration of the first drift region; a secondary doping layer located in part of the second drift region, the conductivity type of the secondary doping layer being opposite to the conductivity type of the drift layer; a plurality of main doping layers located in the drift layer and spaced around the secondary doping layer, the conductivity type of the main doping layer being the same as the conductivity type of the secondary doping layer. The Schottky diode ensures that the conduction channel is completely pinched off at a relatively small reverse bias, and at the same time can ensure that it has a low on-resistance when forward conducting.

[0034] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified 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 a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] An embodiment of the present invention provides a Schottky diode, Figure 2 and Figure 3 ,include:

[0039] Semiconductor substrate layer 100;

[0040] a drift layer 110 located on the semiconductor substrate layer 100, the drift layer 110 comprising a first drift region 110A and a second drift region 110B located on a side of the first drift region 110A facing away from the semiconductor substrate layer 100, wherein a doping concentration of the second drift region 110B is greater than a doping concentration of the first drift region 110A;

[0041] a sub-doping layer 130 located in a portion of the second drift region 110B, wherein the conductivity type of the sub-doping layer 130 is opposite to the conductivity type of the drift layer 110;

[0042] A plurality of main doping layers 120 are located in the drift layer 110 and are spaced apart around the sub-doping layer 130 . The conductivity type of the main doping layer 120 is the same as that of the sub-doping layer 130 .

[0043] The Schottky diode further includes: a Schottky contact electrode layer 140 located on a side of the drift layer 110 facing away from the semiconductor substrate layer 100 ; and an ohmic contact electrode layer 150 located on a side of the semiconductor substrate layer 100 facing away from the drift layer.

[0044] It should be noted that Figure 3 In order to conveniently illustrate the sub-doping layer 130 and the main doping layer 120 , the Schottky contact electrode layer 140 is omitted.

[0045] In this embodiment, the Schottky diode is a SiC-based Schottky diode as an example for explanation, and accordingly, the semiconductor substrate layer 100 is silicon carbide (SiC) doped with conductive ions. The new generation of semiconductor devices represented by SiC have higher reverse withstand voltage, lower forward conduction loss, faster switching frequency and stronger environmental tolerance, and are therefore considered to be a new hope in the field of power conversion. Among them, SiC Schottky diodes (SBDs) are gradually replacing Si-based devices and becoming the mainstream of the market in the medium and high voltage fields due to their many advantages such as high frequency and low loss.

[0046] In other embodiments, the Schottky diode may also be a gallium nitride-based Schottky diode. In other embodiments, the Schottky diode may also be a silicon-based Schottky diode. It should be noted that in this embodiment, there is no limitation on the material of the semiconductor substrate layer 100 .

[0047] In this embodiment, the drift layer 110 is doped with drift ions. The material of the drift layer 110 is silicon carbide doped with drift ions. In this embodiment, the conductivity type of the drift layer 110 is N-type. It should be noted that in other embodiments, the material of the drift layer 110 can also be other materials. In other embodiments, the conductivity type of the drift layer 110 can also be P-type. The drift ions can be silicon ions or phosphorus ions.

[0048] In one embodiment, the drift layer 110 has a thickness of 10 micrometers to 20 micrometers, for example, 10 micrometers, 12 micrometers, 15 micrometers, 18 micrometers or 20 micrometers.

[0049] The drift layer 110 includes a first drift region 110A and a second drift region 110B. In one embodiment, the ratio of the thickness of the second drift region 110B to the thickness of the first drift region 110A is 1 / 100 to 1 / 10, such as 1 / 16, 1 / 25, 1 / 50, 1 / 75, or 1 / 100. If the ratio of the thickness of the second drift region 110B to the thickness of the first drift region 110A is less than 1 / 100, the forward conduction resistance of the Schottky diode increases; if the ratio of the thickness of the second drift region 110B to the thickness of the first drift region 110A is greater than 1 / 10, the reverse leakage current of the Schottky diode increases.

[0050] In one embodiment, the doping concentration of the second drift region 110B is 2 to 100 times, such as 10 times, 2 times, 10 times, 20 times, 50 times, 80 times, or 100 times, of the doping concentration of the first drift region 110A. If the doping concentration of the second drift region 110B is 100 times greater than the doping concentration of the first drift region 110A, the reverse leakage current of the Schottky diode increases; if the doping concentration of the second drift region 110B is less than 2 times the doping concentration of the first drift region 110A, the on-resistance of the Schottky diode increases.

[0051] In this embodiment, in order to make the Schottky diode have better reverse withstand voltage performance, the PiN structure is introduced into the Schottky diode, that is, the Schottky diode in this embodiment is a junction barrier Schottky (JBS) diode. The field control of the junction barrier Schottky diode can maintain a small electric field strength on the contact surface of the Schottky metal and the drift layer 110, thereby reducing leakage current.

[0052] The most important design principle of the junction barrier Schottky is the ability to balance the forward and reverse characteristics. When forward biased, the on-resistance should be as small as possible and the Schottky contact area should be as large as possible; when reverse biased, the reverse breakdown voltage should be as large as possible and the leakage current should be as small as possible.

[0053] In the present embodiment, the main doping layer 120 is located in the drift layer 110, and the sidewall and the bottom of the main doping layer 120 are in contact with the drift layer 110. Under the reverse bias of the Schottky diode, a space charge region is formed between the main doping layer 120 and the drift layer 110 at the bottom of the main doping layer 120, and a space charge region is formed between the main doping layer 120 and the drift layer 110 at the side of the main doping layer 120, so that a space charge region with a larger area can be formed between the main doping layer 120 and the adjacent drift layer 110, thereby improving the voltage resistance of the Schottky diode.

[0054] In one embodiment, the main doping layer 120 is only located in a portion of the second drift region 110B; in another embodiment, the main doping layer is located in the first drift region and the second drift region, that is, the main doping layer extends from the second drift region to the first drift region. In this embodiment, the main doping layer 120 is located in the second drift region 110B and the bottom and side surfaces of the main doping layer 120 are surrounded by the second drift region 110B as an example.

[0055] The longitudinal dimension of the sub-doping layer 130 is 1 / 10 to 2 times of the longitudinal dimension of the second drift region 110B.

[0056] In this embodiment, the sub-doping layer 130 is only located in the second drift region 110B. The longitudinal dimension of the sub-doping layer 130 is 20% to 100% of the longitudinal dimension of the second drift region.

[0057] If the concentration of doping ions in the main doping layer 120 is too high, the reverse leakage current will increase; if the concentration of doping ions in the main doping layer 120 is too low, the reverse space charge region will not overlap sufficiently. Therefore, in this embodiment, the doping concentration of doping ions in the main doping layer 120 is selected to be in the range of 2e 18 atom / cm 3 -8e 18 atom / cm 3 In one embodiment, the concentration of doping ions in the main doping layer 120 is 500 to 1000 times the doping concentration in the first drift region 110A.

[0058] In this embodiment, for the adjacent main doping layers distributed along the circumferential direction of the secondary doping layer 130, under a certain reverse bias, the spatial depletion regions of the PN junctions formed by the adjacent main doping layers 120 can overlap or contact. Since the secondary doping layer 130 is provided, under a certain reverse bias, a spatial depletion region of the PN junction will also be formed between the secondary doping layer 130 and the drift region. When the spatial depletion regions of the PN junctions formed by the adjacent main doping layers 120 along the circumferential direction of the secondary doping layer 130 just contact under the reverse bias, the spatial depletion region formed by the secondary doping layer 130 and the drift region at least partially overlaps with the spatial depletion region formed by the main doping layer 120 and the drift region. Therefore, the spatial depletion region formed by the secondary doping layer 130 and the drift region and the spatial depletion region formed by the main doping layer 120 and the drift region protect the Schottky contact region, so that the Schottky contact region is completely in the field protection range.

[0059] Since the doping concentration of the second drift layer 110B is greater than the doping concentration of the first drift layer 110A, and the sub-doping layer 130 is located in the second drift layer 110B, even if the area of ​​the sub-doping layer 130 is slightly larger, the second drift layer with a higher doping concentration can compensate for the effect of the increase in the area of ​​the sub-doping layer on the conduction channel resistance, so that the conduction channel resistance is lower. Specifically, since the doping concentration of the second drift layer 110B is relatively high, the space depletion layer caused by the sub-doping layer 130 can be reduced, the area of ​​the conduction channel can be increased, and the carrier concentration of the surface layer is increased, the conductivity of the conduction channel is increased, and the conduction resistance is further reduced, which can reduce the forward conduction voltage drop.

[0060] Since the area of ​​the secondary doping layer can be increased, when the spatial depletion regions of the PN junctions formed by the adjacent main doping layers in the circumferential direction of the secondary doping layer just touch under reverse bias, the spatial depletion region formed by the secondary doping layer and the drift region and the spatial depletion region formed by the main doping layer and the drift region also completely overlap with each other, and the spatial depletion region occupies the entire active area laterally, so that the spatial depletion region fully protects the Schottky contact region, so that the Schottky contact region is completely within the field protection range, ensuring that the Schottky diode can be completely turned off under a smaller reverse bias, and the leakage current of the Schottky diode is small. In summary, it is ensured that the Schottky diode can be completely turned off under a smaller reverse bias, and low on-resistance during forward conduction can also be ensured.

[0061] Secondly, as the PN junction depletes the conduction channel when reverse biased, a continuous and uninterrupted space charge region can be formed, so that the Schottky diode has the reverse voltage withstand capability of the PN diode.

[0062] The Schottky contact region refers to a region where the Schottky contact electrode layer contacts the drift layer located at the side of the sub-doped layer and the main doped layer.

[0063] In this embodiment, the doping concentration of the sub-doping layer 130 is less than the doping concentration of the main doping layer 120. Since the concentration of the sub-doping layer 130 is less than the concentration of the main doping layer 120, it is possible to accurately control the breakdown of the Schottky diode in the area where the sub-doping layer 130 is located when reverse biased, and the breakdown is distributed in the entire active area rather than the field stop area, thereby improving the avalanche resistance of the Schottky diode. Secondly, since the concentration of the sub-doping layer 130 is less than the concentration of the main doping layer 120, the width of the depletion layer on the drift layer side formed by the PN junction formed by the sub-doping layer 130 and the drift layer is reduced, so that the channel resistance of the Schottky diode when it is forward-conducted is further reduced.

[0064] In a specific embodiment, the doping concentration of the sub-doping layer 130 is 5% to 80%, such as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80% of the doping concentration of the main doping layer 120. If the doping concentration of the sub-doping layer 130 is too low, the reverse empty point charge region will not overlap sufficiently; if the doping concentration of the sub-doping layer 130 is greater than 80% of the doping concentration of the main doping layer 120, the reverse breakdown region cannot be accurately controlled.

[0065] The surface area of ​​the sub-doping layer 130 is 5% to 40% of the surface area of ​​the main doping layer 120 , such as 5%, 10%, 20%, 30% or 40%.

[0066] The surface area of ​​the sub-doping layer 130 refers to the top surface of the sub-doping layer 130 exposed by the drift layer. The surface area of ​​the main doping layer 120 refers to the top surface of the main doping layer 120 exposed by the drift layer.

[0067] In one embodiment, the surface area of ​​the sub-doped layer is 0.2 μm 2 -2μm 2 .

[0068] The distances between the center of the sub-doping layer 130 and the center of the adjacent main doping layer 120 are equal, so that the distribution of the sub-doping layer 130 is more uniform, which can improve the reverse breakdown withstand voltage of the Schottky diode.

[0069] The surface shape of the sub-doping layer 130 is the same as the surface shape of the main doping layer 120 .

[0070] The surface shape of the sub-doping layer 130 includes a circle, a square, a rectangle or a hexagon; the surface shape of the main doping layer 120 includes a circle, a square, a rectangle or a hexagon.

[0071] In this embodiment, reference Figure 3The surface shape of the auxiliary doping layer 130 is hexagonal, and the surface shape of the main doping layer 120 is hexagonal. According to theoretical calculations, the combination of the hexagonal auxiliary doping layer and the hexagonal main doping layer 120 can maintain the largest conduction path, have the largest Schottky contact surface, and minimize series resistance and capacitance under the premise that the depletion layer completely shields the active area.

[0072] In other embodiments, reference Figure 4 , the surface shapes of the main doping layer 120a and the sub-doping layer 130a are circular. Figure 5 The surface shapes of the main doping layer 120b and the sub-doping layer 130b are square.

[0073] In this embodiment, since the surface area of ​​the sub-doping layer 130 is appropriately increased, the sub-doping layer 130 is easier to manufacture.

[0074] Correspondingly, another embodiment of the present invention further provides a method for preparing a Schottky diode, referring to Figure 6 , including the following steps:

[0075] S01: providing a semiconductor substrate layer;

[0076] S02: forming a drift layer on the semiconductor substrate layer, wherein the drift layer comprises a first drift region and a second drift region located on a side of the first drift region facing away from the semiconductor substrate layer, wherein a doping concentration of the second drift region is greater than a doping concentration of the first drift region;

[0077] S03: forming a sub-doping layer in a portion of the second drift region, wherein the conductivity type of the sub-doping layer is opposite to the conductivity type of the drift layer;

[0078] S04: forming a plurality of main doping layers in the drift layer, wherein the plurality of main doping layers are spaced around the sub-doping layer, and the conductivity type of the main doping layer is the same as the conductivity type of the sub-doping layer.

[0079] Reference below Figures 7 to 10 The structural schematic diagram of the Schottky diode formation process in this embodiment is specifically introduced.

[0080] refer to Figure 7 , providing a semiconductor substrate layer 100.

[0081] refer to Figure 8 A drift layer 110 is formed on the semiconductor substrate layer 100, wherein the drift layer 110 includes a first drift region 110A and a second drift region 110B located on a side of the first drift region 110A facing away from the semiconductor substrate layer 100, wherein the doping concentration of the second drift region 110B is greater than the doping concentration of the first drift region 110A.

[0082] The method for forming the drift layer 110 includes: forming an initial drift layer on the semiconductor substrate layer 100 ; and performing ion implantation on a portion of the initial drift layer so that the initial drift layer forms the drift layer 110 .

[0083] refer to Fig. 9 , a sub-doping layer 130 is formed in part of the second drift region 110B, and the conductivity type of the sub-doping layer 130 is opposite to the conductivity type of the drift layer 110; a plurality of main doping layers 120 are formed in the drift layer 110, and the plurality of main doping layers 120 are spaced around the sub-doping layer 130, and the conductivity type of the main doping layer 120 is the same as the conductivity type of the sub-doping layer 130; the doping concentration of the sub-doping layer 130 is less than the doping concentration of the main doping layer 120.

[0084] The process of forming the sub-doping layer 130 includes an ion implantation process, and the process of forming the main doping layer 120 includes an ion implantation process. Both the ion implantation process of forming the sub-doping layer 130 and the ion implantation process of forming the main doping layer 120 are ion implantation processes using a mask.

[0085] In one embodiment, the main doping layer 120 is formed after the sub-doping layer 130 is formed; in another embodiment, the sub-doping layer 130 is formed after the main doping layer 120 is formed.

[0086] refer to Fig.10 After forming the sub-doping layer 130 and the main doping layer 120 , a Schottky contact electrode layer 140 is formed on the side of the drift layer 110 facing away from the semiconductor substrate layer 100 ; and an ohmic contact electrode layer 150 is formed on the side of the semiconductor substrate layer 100 facing away from the drift layer.

[0087] In the present application, since the concentration of the secondary doping layer 130 is less than that of the main doping layer 120, the Schottky diode can be precisely controlled to break down in the area where the secondary doping layer 130 is located when reverse biased, and the breakdown is distributed in the entire active area rather than the field stop area, thereby improving the avalanche resistance of the Schottky diode. Since the doping concentration of the second drift layer is greater than the doping concentration of the first drift layer, even if the area of ​​the secondary doping layer 130 is made slightly larger, the second drift layer 110B with a higher doping concentration can compensate for the effect of the increase in the area of ​​the secondary doping layer 130 on the channel resistance, so that the on-channel resistance is lower. Since the area of ​​the secondary doping layer 130 can be increased, when the space depletion region of the PN junction formed by the adjacent main doping layer in the circumferential direction of the secondary doping layer 130 just touches under reverse bias, the space depletion region formed by the secondary doping layer and the drift region and the space depletion region formed by the main doping layer 120 and the drift region 110 also completely overlap with each other, and the space depletion region occupies the entire active area laterally, so that the space depletion region fully protects the Schottky contact region, so that the Schottky contact region is completely in the field protection range, ensuring that the Schottky diode can be completely turned off under a smaller reverse bias, and the leakage current of the Schottky diode is small. In summary, it is ensured that the Schottky diode can be completely turned off under a smaller reverse bias, and the low on-resistance during forward conduction can also be ensured.

[0088] In the present application, the surface area of ​​the sub-doping layer 130 can be appropriately increased, thereby reducing the difficulty of the process of forming the sub-doping layer 130 .

[0089] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A Schottky diode, characterized in that: include: Semiconductor substrate layer; a drift layer located on the semiconductor substrate layer, the drift layer comprising a first drift region and a second drift region located on a side of the first drift region facing away from the semiconductor substrate layer, wherein a doping concentration of the second drift region is greater than a doping concentration of the first drift region; a sub-doped layer located in a portion of the second drift region, wherein the conductivity type of the sub-doped layer is opposite to the conductivity type of the drift layer; A plurality of main doping layers are located in the drift layer and are spaced around the sub-doping layer, the conductivity type of the main doping layer is the same as the conductivity type of the sub-doping layer, when the spatial depletion regions of the PN junctions formed by the adjacent main doping layers in the circumferential direction of the sub-doping layer just touch under reverse bias, the spatial depletion region formed by the sub-doping layer and the drift region and the spatial depletion region formed by the main doping layer and the drift region also completely overlap with each other, and the spatial depletion region laterally occupies the entire active area; the doping concentration of the sub-doping layer is less than the doping concentration of the main doping layer, and the surface area of ​​the sub-doping layer is 5% to 40% of the surface area of ​​the main doping layer.

2. The Schottky diode according to claim 1, characterized in that: The doping concentration of the second drift region is 2 to 100 times the doping concentration of the first drift region.

3. The Schottky diode according to claim 1, characterized in that: The ratio of the thickness of the second drift region to the thickness of the first drift region is 1 / 100 to 1 / 10.

4. The Schottky diode according to claim 1, characterized in that: The doping concentration of the sub-doping layer is 5% to 80% of the doping concentration of the main doping layer.

5. The Schottky diode according to claim 1, characterized in that: The longitudinal dimension of the sub-doping layer is 1 / 10 to 2 times the longitudinal dimension of the second drift region.

6. The Schottky diode according to claim 1, characterized in that: The distances between the center of the sub-doping layer and the center of the adjacent main doping layer are equal.

7. The Schottky diode according to claim 1, characterized in that: The surface shape of the sub-doping layer is the same as the surface shape of the main doping layer.

8. The Schottky diode according to any one of claims 1 to 7, characterized in that: The surface shape of the sub-doping layer includes a circle, a square, a rectangle or a hexagon; the surface shape of the main doping layer includes a circle, a square, a rectangle or a hexagon.

9. A method for preparing a Schottky diode according to any one of claims 1 to 8, characterized in that: include: providing a semiconductor substrate layer; forming a drift layer on the semiconductor substrate layer, the drift layer comprising a first drift region and a second drift region located on a side of the first drift region facing away from the semiconductor substrate layer, wherein the doping concentration of the second drift region is greater than the doping concentration of the first drift region; forming a sub-doping layer in a portion of the second drift region, wherein the conductivity type of the sub-doping layer is opposite to the conductivity type of the drift layer; A plurality of main doping layers are formed in the drift layer. The plurality of main doping layers are spaced around the sub-doping layer. The conductivity type of the main doping layer is the same as that of the sub-doping layer.

10. The method for preparing a Schottky diode according to claim 9, characterized in that: The process of forming the sub-doping layer includes an ion implantation process.

11. The method for preparing a Schottky diode according to claim 9, characterized in that: The method for forming the drift layer comprises: forming an initial drift layer on the semiconductor substrate layer; and performing ion implantation on a partial thickness of the initial drift layer so that the initial drift layer forms the drift layer.

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