CN215988778U

CN215988778U - Schottky diode

Info

Publication number: CN215988778U
Application number: CN202120417435.1U
Authority: CN
Inventors: 张园览; 张清纯
Original assignee: Guanghua Lingang Engineering Application Technology Research and Development Shanghai Co Ltd
Current assignee: Guanghua Lingang Engineering Application Technology Research and Development Shanghai Co Ltd
Priority date: 2021-02-24
Filing date: 2021-02-24
Publication date: 2022-03-08
Anticipated expiration: 2031-02-24

Abstract

A schottky diode, comprising: a semiconductor substrate layer; the drift layer is positioned on the semiconductor substrate layer and comprises a first drift region and a second drift region positioned on one side, opposite to the semiconductor substrate layer, of the first drift region, and the doping concentration of the second drift region is greater than that of the first drift region; a sub-doping layer located in a portion of the second drift region, a conductivity type of the sub-doping layer being opposite to a conductivity type of the drift layer; the drift layer is provided with a plurality of primary doping layers which are arranged in the drift layer and distributed at intervals around the secondary doping layers, and the conductivity type of the primary doping layers is the same as that of the secondary doping layers. The Schottky diode ensures that a conduction channel is completely pinched off under a smaller reverse bias voltage, and meanwhile, the Schottky diode can ensure that the Schottky diode has low conduction resistance when conducting in the forward direction.

Description

Schottky diode

Technical Field

The utility model relates to the field of semiconductors, in particular to a Schottky diode.

Background

The power diode is one of the most commonly used electronic components, is the most basic constituent unit of power electronic circuits, and the unidirectional conductivity of the power diode can be used for rectification, clamping and free-wheeling of the circuits. The diode in the peripheral circuit mainly plays a role in preventing reverse connection, and prevents the device from being damaged due to reverse current flowing. Conventional power diodes mainly include schottky power diodes and PN junction power diodes. Compared with a PN junction power diode, the schottky power diode forms a metal semiconductor junction by using metal-to-semiconductor contact (gold half contact), so that the forward turn-on voltage is smaller. Furthermore, schottky power diodes are unipolar majority carrier conduction mechanisms, with reverse recovery times ideally zero, without accumulation of excess minority carriers.

However, for schottky power diodes, there is a reasonable tradeoff between complete pinch-off of the conduction channel at lower reverse bias and low forward on-resistance, which limits the application of schottky power diodes in high voltage applications to some extent.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that the prior art can not ensure that the complete pinch-off of a conduction channel under the condition of smaller reverse bias and the low on-resistance under the condition of forward conduction can not be considered at the same time.

In order to solve the above technical problem, the present invention provides a schottky diode, including: a semiconductor substrate layer; the drift layer is positioned on the semiconductor substrate layer and comprises a first drift region and a second drift region positioned on one side, opposite to the semiconductor substrate layer, of the first drift region, and the doping concentration of the second drift region is greater than that of the first drift region; a sub-doping layer located in a portion of the second drift region, the sub-doping layer having a conductivity type opposite to that of the drift layer; the plurality of main doping layers are positioned in the drift layer and distributed at intervals around the auxiliary doping layer, and the conductivity type of the main doping layers is the same as that of the auxiliary doping layers; the doping concentration of the secondary doping layer is smaller than that of the main doping layer.

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

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

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

Optionally, the doping concentration of the secondary doping layer is 5% to 80% of the doping concentration of the primary doping layer.

Optionally, the surface area of the secondary doping layer is 5% to 40% of the surface area of the primary doping layer.

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

Optionally, the distances between the centers of the sub-doped layers and the centers of the adjacent main doped layers are equal.

Optionally, the surface shape of the sub-doping layer is the same as the surface shape of the main doping layer.

Optionally, the surface shape of the secondary doping layer includes a circle, a square, a rectangle or a hexagon; the surface shape of the main doping layer comprises a circle, a square, a rectangle or a hexagon.

The technical scheme of the utility model has the following beneficial effects:

according to the Schottky diode provided by the technical scheme of the utility model, for the adjacent main doping layers distributed along the circumferential direction of the auxiliary doping layer, under a certain reverse bias voltage, the space depletion regions of PN junctions formed by the adjacent main doping layers can be overlapped or contacted. Due to the arrangement of the secondary doping layer, a space depletion region of a PN junction is formed between the secondary doping layer and the drift region under a certain reverse bias voltage. When the space depletion regions of the PN junctions formed along the main doping layers adjacent in the circumferential direction of the secondary doping layers just contact under reverse bias, the space depletion region formed by the secondary doping layers and the drift region and the space depletion region formed by the main doping layers and the drift region at least partially overlap with each other. Therefore, the schottky contact region is protected by the space depletion region formed by the auxiliary doping layer and the drift region and the space depletion region formed by the main doping layer and the drift region, so that the schottky contact region is in a wider field protection range. Secondly, because the doping concentration of the second drift layer is greater than that of the first drift layer, even if the area of the sub-doping layer is slightly larger, the second drift layer with higher doping concentration can compensate the influence of the increase of the area of the sub-doping layer on the channel resistance, so that the on-channel resistance is lower. Due to the fact that the area of the secondary doping layer can be increased, when space depletion regions of PN junctions formed along the main doping layers adjacent to each other in the circumferential direction of the secondary doping layers just contact each other under reverse bias, the space depletion regions formed by the secondary doping layers and the drift region are completely overlapped with the space depletion regions formed by the main doping layers and the drift region, the space depletion regions transversely occupy the whole active region, the space depletion regions fully protect the Schottky contact regions, the Schottky contact regions are completely in a field protection range, the Schottky diode can be completely turned off under the condition of small reverse bias, and the leakage current of the Schottky diode is small. In conclusion, the schottky diode can be completely turned off under a smaller reverse bias voltage, and the low on-resistance in the forward conduction can also be ensured.

Secondly, with depletion of the PN junction to the conduction channel in reverse bias, a continuous space charge region without intervals can be formed, so that the Schottky diode has the reverse voltage-resisting capability of the PN diode. And secondly, because the concentration of the secondary doping layer is less than that of the primary doping layer, the breakdown of the Schottky diode in the region where the secondary doping layer is positioned can be accurately controlled during reverse bias, and the breakdown is distributed in the whole active region rather than the field cut-off region, so that the avalanche tolerance of the Schottky diode is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts;

fig. 1 is a schematic structural diagram of a schottky diode;

fig. 2 is a schematic structural diagram of a schottky diode according to an embodiment of the present invention;

FIG. 3 is a top view of FIG. 2;

FIG. 4 is a top view of a primary doped layer and a secondary doped layer in another embodiment of the present invention;

fig. 5 is a top view of a main doped layer and a sub-doped layer in a further embodiment of the present invention.

Detailed Description

A schottky diode, with reference to the figure, comprising: 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, the sub-doped layer 12 having a conductivity type opposite to that of the drift region 11; and a plurality of main doping layers 13 located in the drift layer 11 and distributed at intervals around the sub-doping layer 12, wherein the conductivity type of the main doping layer 13 is the same as that of the sub-doping layer 12.

In the Schottky diode, the purpose of arranging the auxiliary doping layer 12 is to enable a space depletion region formed by the auxiliary doping layer and the drift region to be partially overlapped with a space depletion region formed by the main doping layer and the drift region, and the space depletion region formed by the auxiliary 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 a wider field protection range. In general, the sub-doped layer 12 has a small surface area, and is provided to increase the area of the schottky contact region, reduce the on-resistance, increase the current density, and improve the device performance.

However, since the surface area of the sub-doped layer 12 is small, when the space depletion regions of the PN junctions formed along the main doped layers adjacent in the circumferential direction of the sub-doped layer just contact each other under reverse bias, the space depletion regions formed by the sub-doped layer and the drift region do not completely overlap with the space depletion regions formed by the main doped layer and the drift region, and a part of the drift region between the sub-doped layer 12 and the main doped layer is not formed with the space depletion layer, so that the schottky diode cannot be completely turned off under a small reverse bias.

On this basis, an embodiment of the present invention provides a schottky diode, including: a semiconductor substrate layer; the drift layer is positioned on the semiconductor substrate layer and comprises a first drift region and a second drift region positioned on one side, opposite to the semiconductor substrate layer, of the first drift region, and the doping concentration of the second drift region is greater than that of the first drift region; a sub-doping layer located in a portion of the second drift region, the sub-doping layer having a conductivity type opposite to that of the drift layer; the drift layer is provided with a plurality of primary doping layers which are arranged in the drift layer and distributed at intervals around the secondary doping layers, and the conductivity type of the primary doping layers is the same as that of the secondary doping layers. The Schottky diode ensures that a conduction channel is completely pinched off under a smaller reverse bias voltage, and meanwhile, the Schottky diode can ensure that the Schottky diode has low conduction resistance when conducting in the forward direction.

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

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

An embodiment of the present invention provides a schottky diode, which is combined with fig. 2 and fig. 3, and includes:

a semiconductor substrate layer 100;

a drift layer 110 located 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, and a doping concentration of the second drift region 110B is greater than a doping concentration of the first drift region 110A;

a sub-doped layer 130 located in a portion of the second drift region 110B, a conductivity type of the sub-doped layer 130 being opposite to a conductivity type of the drift layer 110;

a plurality of main doped layers 120 located in the drift layer 110 and distributed at intervals around the sub-doped layer 130, wherein the conductivity type of the main doped layer 120 is the same as that of the sub-doped layer 130.

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 the ohmic contact electrode layer 150 is positioned on the side, facing away from the drift layer, of the semiconductor substrate layer 100.

Note that, in fig. 3, the schottky contact electrode layer 140 is omitted for convenience of illustration of the sub-doped layer 130 and the main doped layer 120.

In this embodiment, the schottky diode is an SiC-based schottky diode as an example, and accordingly, the semiconductor substrate layer 100 is silicon carbide (SiC) doped with conductive ions. A new generation of semiconductor devices represented by SiC has higher reverse withstand voltage capability, lower forward conduction loss, faster switching frequency, and stronger environmental tolerance, and is therefore considered as a new hope in the field of electric energy conversion. Among them, SiC schottky diodes (SBDs) are becoming the mainstream of the market in the middle and high voltage fields because they have many advantages such as high frequency and low loss.

In other embodiments, the schottky diode may also be a gan schottky diode. In other embodiments, the schottky diode may also be a silicon-based schottky diode. In this embodiment, the material of the semiconductor substrate layer 100 is not limited.

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 may also be other materials. In other embodiments, the conductivity type of the drift layer 110 may also be P-type. The drift ions may be silicon ions or phosphorus ions.

In one embodiment, the drift layer 110 has a thickness of 10 to 20 microns, such as 10, 12, 15, 18, or 20 microns.

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 1/100-1/10, 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, an increase in the forward on-resistance of the schottky diode results; 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, an increase in schottky diode reverse leakage current results.

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

In this embodiment, in order to make the schottky diode have a better reverse withstand voltage performance, a P-i-N structure is introduced into the schottky diode, that is, the schottky diode of this embodiment is a Junction Barrier Schottky (JBS) diode. The field control of the junction barrier Schottky diode can keep smaller electric field intensity of the contact surface of the Schottky metal and the drift layer 110, and reduce leakage current.

The most important design principle of junction barrier schottky is the ability to balance the forward and reverse characteristics. When the Schottky diode is forward biased, the on resistance is as small as possible, and the Schottky contact region is 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.

In this embodiment, the main doping layer 120 is located in the drift layer 110, the sidewall and the bottom of the main doping layer 120 are both in contact with the drift layer 110, and 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, and the voltage resistance of the schottky diode is improved.

In one embodiment, the main doped layer 120 is only located in a portion of the second drift region 110B; in another embodiment, the main doped layer is located in the first drift region and the second drift region, i.e. the main doped layer extends from the second drift region into the first drift region. In the present embodiment, the main doped layer 120 is located in the second drift region 110B, and the bottom surface and the side surface of the main doped layer 120 are both surrounded by the second drift region 110B as an example.

The longitudinal dimension of the sub-doped layer 130 is 1/10-2 times the longitudinal dimension of the second drift region 110B.

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

If the concentration of the dopant ions in the main doped layer 120 is too high, the reverse leakage current is increased; if the concentration of the dopant ions in the main doped layer 120 is too low, the reverse space charge regions may not overlap sufficiently. Therefore, in this embodiment, the doping concentration range of the doping ions in the main doping layer 120 is selected to be 2e¹⁸atom/cm³-8e¹⁸atom/cm³. In one embodiment, the concentration of the dopant ions in the main doping layer 120 is 500 times to 1000 times the doping concentration in the first drift region 110A.

In this embodiment, for adjacent main doped layers distributed along the circumferential direction of the sub-doped layer 130, the space depletion regions of the PN junctions formed by the adjacent main doped layers 120 can overlap or contact with each other under a certain reverse bias. Due to the arrangement of the sub-doped layer 130, a space depletion region of a PN junction is also formed between the sub-doped layer 130 and the drift region under a certain reverse bias. When the space depletion regions of the PN junctions formed along the main doped layers 120 adjacent in the circumferential direction of the sub-doped layer 130 just contact under a reverse bias, the space depletion regions formed by the sub-doped layer 130 and the drift region and the space depletion regions formed by the main doped layer 120 and the drift region at least partially overlap each other. The space depletion region formed by the sub-doped layer 130 and the drift region and the space depletion region formed by the main doped layer 120 and the drift region protect the schottky contact region so that the schottky contact region is completely in the field protection range.

Since the doping concentration of the second drift layer 110B is greater than that 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 made slightly larger, the second drift layer with a higher doping concentration can compensate the influence of the increase in the area of the sub-doping layer on the on-channel resistance, so that the on-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, the carrier concentration of the surface layer can be increased, the conductivity of the conduction channel can be increased, the on-resistance can be further reduced, and the forward conduction voltage drop can be further reduced.

Due to the fact that the area of the secondary doping layer can be increased, when space depletion regions of PN junctions formed along the main doping layers adjacent to each other in the circumferential direction of the secondary doping layers just contact each other under reverse bias, the space depletion regions formed by the secondary doping layers and the drift region are completely overlapped with the space depletion regions formed by the main doping layers and the drift region, the space depletion regions transversely occupy the whole active region, the space depletion regions fully protect the Schottky contact regions, the Schottky contact regions are completely in a field protection range, the Schottky diode can be completely turned off under the condition of small reverse bias, and the leakage current of the Schottky diode is small. In conclusion, the schottky diode can be completely turned off under a smaller reverse bias voltage, and the low on-resistance in the forward conduction can also be ensured.

Secondly, with depletion of the PN junction to the conduction channel in reverse bias, a continuous space charge region without intervals can be formed, so that the Schottky diode has the reverse voltage-resisting capability of the PN diode.

The Schottky contact region refers to: and a region where the Schottky contact electrode layer is in contact with the drift layer located at the side of the sub-doping layer and the main doping layer.

In this embodiment, the doping concentration of the sub-doping layer 130 is less than the doping concentration of the main doping layer 120. Because the concentration of the sub-doping layer 130 is less than that of the main doping layer 120, the breakdown of the schottky diode in the region where the sub-doping layer 130 is located during reverse bias can be accurately controlled, and the breakdown is distributed in the whole active region rather than the field stop region, so that the avalanche resistance of the schottky diode is improved. Next, since the concentration of the sub-doped layer 130 is less than that of the main doped layer 120, the width of the depletion layer of the PN junction formed by the sub-doped layer 130 and the drift layer on the drift layer side is reduced, which further reduces the channel resistance when the schottky diode is turned on in the forward direction.

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 regions are not sufficiently overlapped; 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 precisely controlled.

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

The surface area of the sub-doped layer 130 refers to the top surface of the sub-doped layer 130 exposed by the drift layer. The surface area of the main doped layer 120 refers to the top surface of the main doped layer 120 exposed by the drift layer.

In one embodiment, the surface area of the sub-doped layer is 0.2 μm²-2μm²。

The distances from the centers of the sub-doping layers 130 to the centers of the adjacent main doping layers 120 are equal, so that the distribution of the sub-doping layers 130 is more uniform, and the reverse breakdown withstand voltage of the schottky diode can be improved.

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

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

In this embodiment, referring to fig. 3, the surface shape of the sub-doping layer 130 is a hexagon, and the surface shape of the main doping layer 120 is a hexagon. Through theoretical calculation, the combination of the hexagonal secondary doping layer and the hexagonal main doping layer 120 can maintain the largest conduction path, have the largest schottky contact surface, and have the smallest series resistance and capacitance on the premise that the depletion layer completely shields the active region.

In other embodiments, referring to fig. 4, the surface shapes of the main doping layer 120a and the sub doping layer 130a are circular. Referring to fig. 5, the surface shapes of the main doping layer 120b and the sub-doping layer 130b are square.

In this embodiment, the surface area of the sub-doped layer 130 is increased appropriately, so that the sub-doped layer 130 is easier to manufacture.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the utility model.

Claims

1. A schottky diode, comprising:

a semiconductor substrate layer;

the drift layer is positioned on the semiconductor substrate layer and comprises a first drift region and a second drift region positioned on one side, opposite to the semiconductor substrate layer, of the first drift region, and the doping concentration of the second drift region is greater than that of the first drift region;

a sub-doping layer located in a portion of the second drift region, the sub-doping layer having a conductivity type opposite to that of the drift layer;

the plurality of main doping layers are positioned in the drift layer and distributed at intervals around the auxiliary doping layer, and the conductivity type of the main doping layers is the same as that of the auxiliary doping layers;

the surface area of the secondary doping layer is 5% -40% of the surface area of the main doping layer.

2. The Schottky diode of claim 1, wherein a ratio of a thickness of the second drift region to a thickness of the first drift region is 1/100-1/10.

3. The schottky diode of claim 1, wherein the longitudinal dimension of the sub-doped layer is 1/10-2 times the longitudinal dimension of the second drift region.

4. The schottky diode of claim 1 wherein the centers of the sub-doped layers are equally spaced from the centers of adjacent main doped layers, respectively.

5. The schottky diode of claim 1 wherein the surface shape of the secondary doped layer is the same as the surface shape of the primary doped layer.

6. The schottky diode of any of claims 1 to 5 wherein the surface shape of the sub-doped layer comprises a circle, square, rectangle or hexagon; the surface shape of the main doping layer comprises a circle, a square, a rectangle or a hexagon.