Silicon carbide junction barrier schottky diodes with enhanced robustness

Abstract

Disclosed is a silicon carbide junction barrier Schottky diode including: a first-conductivity-type substrate; a first-conductivity-type epitaxial layer formed by epitaxial growth of silicon carbide doped with a first-conductivity-type impurity on the first-conductivity-type substrate; a charge injection region formed on the first-conductivity-type epitaxial layer and doped with the first-conductivity-type impurity at a higher concentration than a concentration of the first-conductivity-type impurity of the first-conductivity-type epitaxial layer; a second-conductivity-type junction region formed on the first-conductivity-type epitaxial layer to contact the charge injection region; a Schottky metal layer formed on the charge injection region and the second-conductivity-type junction region; an anode electrode formed on the Schottky metal layer; and a cathode electrode formed under the first-conductivity-type substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to a power semiconductor. BACKGROUND

[0002] A silicon carbide junction barrier Schottky diode (SiC SBD) has characteristics of low on-voltage, junction capacitance, fast recovery time, and high cutoff frequency. Due to these characteristics, the SiC SBD is widely used in radio frequency switch mode power supplies (RF SMPS), power management integrated circuits (PIMC), etc. In order to improve the maximum forward surge current I FSM The width of the P+ region is significant for the characteristics and electrostatic discharge (ESD) characteristics. However, if the P+ region is significantly wide, the width of the SBD region is relatively reduced, thereby reducing the forward current. SUMMARY

[0003] According to an aspect of an embodiment of the present application, there is provided a unit cell constituting an active area of a silicon carbide junction barrier Schottky diode. The unit cell includes a first-conductivity-type substrate, a first-conductivity-type epitaxial layer formed by epitaxial growth of silicon carbide doped with a first-conductivity-type impurity on the first-conductivity-type substrate, a charge injection region defined by a second-conductivity-type junction region formed by implanting a second-conductivity-type impurity ion into a first-conductivity-type charge injection layer formed by epitaxial growth of silicon carbide doped with a higher concentration of the first-conductivity-type impurity than a first-conductivity-type impurity concentration of the first-conductivity-type epitaxial layer on the first-conductivity-type epitaxial layer, a Schottky metal layer formed on the charge injection region and the second-conductivity-type junction region, an anode electrode formed on the Schottky metal layer, and a cathode electrode formed under the first-conductivity-type substrate.

[0004] In one embodiment, the second-conductivity-type junction region occupies an area in the range of 62% to 82% in the unit cell.

[0005] In one embodiment, the first-conductivity-type charge injection layer includes two or more multiple epitaxial layers having different first-conductivity-type impurity concentrations.

[0006] In one embodiment, the first-conductivity-type impurity concentrations of the two or more multiple epitaxial layers according to a reference concentration profile decrease in a direction toward the first-conductivity-type epitaxial layer, wherein the reference concentration profile defines the first-conductivity-type impurity concentrations of the two or more multiple epitaxial layers.

[0007] In one embodiment, the reference concentration profile decreases the impurity concentration by 20% in a direction toward the first conductivity type epitaxial layer.

[0008] In one embodiment, the first conductivity type impurity concentration of each of the two or more multiple epitaxial layers is equally increased by at most 40% or decreased by at most 40% in the reference concentration profile.

[0009] In one embodiment, the depth of the two or more multiple epitaxial layers is decreased in a direction toward the first conductivity type epitaxial layer.

[0010] In one embodiment, the depth of the second conductivity type junction region is in a range between 60% and 100% of the depth of the charge injection region.

[0011] According to another aspect of embodiments of the present application, there is provided a silicon carbide junction barrier Schottky diode having an active region. The silicon carbide junction barrier Schottky diode includes a first conductivity type substrate; a first conductivity type epitaxial layer formed by epitaxial growth of silicon carbide doped with a first conductivity type impurity on the first conductivity type substrate; a charge injection region formed on the first conductivity type epitaxial layer and doped with the first conductivity type impurity at a higher concentration than a first conductivity type impurity concentration of the first conductivity type epitaxial layer; a second conductivity type junction region formed on the first conductivity type epitaxial layer so as to contact the charge injection region; a Schottky metal layer formed on the charge injection region and the second conductivity type junction region; an anode electrode formed on the Schottky metal layer; and a cathode electrode formed under the first conductivity type substrate. BRIEF DESCRIPTION OF DRAWINGS

[0012] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. For a simple understanding of the present application, the same elements are designated by the same reference numerals. The structures shown in the drawings are examples for describing the present application, and do not limit the scope of the present application. In particular, in the drawings, some elements are slightly exaggerated in order to easily understand the present application. Since the drawings are used to easily understand the present application, it should be noted that the width, depth, etc. of the elements shown in the drawings can be changed when actually implemented. Meanwhile, the same components are described with reference to the same reference numerals throughout the detailed description of the present application.

[0013] Figure 1 is a schematic cross-sectional view of a SiC SBD with enhanced robustness of the junction termination;

[0014] Figure 2 manufacturing Figure 1 the SIC SBD shown;

[0015] Figure 3 is a cross-sectional view schematically illustrating a unit cell constituting an active region of the SiC SBD shown in FIG. 1; Figure 1 is a cross-sectional view schematically illustrating a unit cell constituting an active region of the SiC SBD shown in FIG. 1;

[0016] Figure 4 is a cross-sectional view schematically illustrating a unit cell constituting an active region of the SiC SBD shown in FIG. 1; Figure 1 is a cross-sectional view schematically illustrating a unit cell constituting an active region of the SiC SBD shown in FIG. 1;

[0017] Figure 5 is a cross-sectional view schematically illustrating a unit cell constituting an active region of the SiC SBD shown in FIG. 1; Figure 1 is a cross-sectional view schematically illustrating a unit cell constituting an active region of the SiC SBD shown in FIG. 1;

[0018] Figure 6 , Figure 7 , Figure 8 and Figure 9 are graphs schematically illustrating electrical characteristics of the SiC SBD shown in FIG. 1; Figures 3 to 5 are graphs schematically illustrating electrical characteristics of the SiC SBD shown in FIG. 1;

[0019] Figure 10 , Figure 11 , Figure 12 and Figure 13 are graphs schematically illustrating electrical characteristics based on a change in a doping concentration of the SiC SBD shown in FIG. 1; Figure 5

[0020] Figure 14 and Figure 15 are graphs schematically illustrating a function of a charge injection region;

[0021] Figure 16 and Figure 17 are graphs schematically illustrating electrical characteristics based on a change in a depth of a second-conductivity-type junction region. DETAILED DESCRIPTION

[0022] The embodiments described below can be implemented individually or in combination with other embodiments. However, this is not intended to limit the present application to a certain embodiment, but it should be understood that all changes, modifications, equivalents or replacements included in the spirit and scope of the present application are included. In particular, any function, feature and / or embodiment can be implemented independently or in combination with other embodiments. Therefore, it should be noted that the scope of the present application is not limited to the embodiments shown in the drawings.

[0023] Terms such as first, second, and the like can be used to refer to various elements, but the elements should not be limited by the terms. The terms will be used to distinguish one element from another element.

[0024] ​The terms used in the following description are intended to describe particular embodiments only and are not intended to limit the present application. Singular expressions include plural expressions unless it is clearly dictated otherwise. Terms such as "include," and "has," are intended to indicate a possibility of existence of the features, numbers, steps, operations, elements, components, or combinations thereof described in the following description, and it should be understood that the possibility of existence or addition of one or more other different features, numbers, steps, operations, elements, components, or combinations thereof is not excluded.

[0025] When an element such as a layer "is on" or "is connected to" another element or layer, it can be directly on the other element or layer, or it can be indirectly connected to the other element or layer through an intermediate element or layer. However, when an element or layer "is directly on" another element or layer, there is no intermediate element or layer between them. Also, when an element or layer is referred to as being "connected" or "coupled" to another element or layer, it can be directly connected or coupled to the other element or layer, or it can be indirectly connected or coupled to the other element or layer through an intermediate element or layer. It will be understood that many variations can be made in the embodiments described herein, which are constructed and arranged in various ways.

[0026] In this document, spatially relative terms such as "beneath", "below", "lower", "above", "upper", and the like can be used for descriptive purposes, thereby describing one element or feature in relation to another element or feature, as illustrated in the drawings. The spatially relative terms are intended to encompass different orientations of the device in use, operation, and / or manufacture in addition to the orientations depicted in the drawings.

[0027] Figure 1 is a schematic cross-sectional view of a silicon carbide junction barrier Schottky diode (SiC SBD) with enhanced robustness.

[0028] The SiC SBD 100 includes an active region and an edge termination region surrounding at least a portion of the active region. The active region includes a Schottky junction and a PN junction. The edge termination region can have various structures such as guard rings, bevels, and junction termination extensions.

[0029] The SiC SBD 100 includes a first-conductivity-type substrate 110, a first-conductivity-type epitaxial layer 120, a charge injection region 130, a second-conductivity-type junction region 140, a second-conductivity-type buffer region 150, an insulating layer 160, a Schottky metal layer 170, an anode electrode 180, and a cathode electrode 190. Here, the first conductivity type refers to a region or layer doped with an n-type impurity, and the second conductivity type refers to a region or layer doped with a p-type impurity, but it can be understood that the opposite case is also possible.

[0030] The first-conductivity-type substrate 110 can be formed by doping a first-conductivity-type impurity on a 4H-SiC or 6H-SiC substrate. For example, the concentration of the first-conductivity-type impurity in the first-conductivity-type substrate 110 can be about 1E18 cm-3. The first-conductivity-type substrate 110 can be formed by doping a first-conductivity-type impurity on a 4H-SiC or 6H-SiC substrate. For example, the concentration of the first-conductivity-type impurity in the first-conductivity-type substrate 110 can be about 1E18 cm-2 The depth of the first-conductivity-type substrate 110 can be about 5 pm.

[0031] The first-conductivity-type epitaxial layer 120 can be formed by epitaxial growth of silicon carbide doped with a first-conductivity-type impurity on the first-conductivity-type substrate 110. For example, the concentration of the first-conductivity-type impurity in the first-conductivity-type epitaxial layer 120 can be about 1E16 cm -2 and the depth of the first-conductivity-type epitaxial layer 120 can be about 11 pm.

[0032] The charge injection region 130 can be formed in the active region on the upper surface of the first-conductivity-type epitaxial layer 120. The charge injection region 130 can have a higher impurity concentration than the first-conductivity-type epitaxial layer 120. For example, the concentration of the first-conductivity-type impurity in the charge injection region 130 can be at least 1.2E16 cm -2 to 1.4E17 cm -2 , which can be at least 1.2 to 1.4 times the impurity concentration of the first-conductivity-type epitaxial layer 120. The depth of the charge injection region 130 can be about 0.6 pm to about 1.0 pm. Meanwhile, the impurity concentration of the charge injection region 130 can be different according to the depth from the upper surface. For example, as the distance from the upper surface increases, the impurity concentration of the charge injection region 130 can decrease.

[0033] As the concentration of the first-conductivity-type impurity increases, the resistivity of the charge injection region 130 decreases. When the resistivity of the charge injection region 130 in contact with the Schottky metal layer decreases, the amount of charge passing through the Schottky junction increases, and the current accordingly increases.

[0034] A plurality of second-conductivity-type junction regions 140 can be formed in the active region on the upper surface of the first-conductivity-type epitaxial layer 120. The plurality of second-conductivity-type junction regions 140 can be formed by ion implanting a second-conductivity-type impurity at a relatively high concentration into the first-conductivity-type charge injection layer 130' (see Figure 2 For example, the concentration of the second-conductivity-type impurity implanted into the second-conductivity-type junction regions 140 can be about 1E18 cm -2 and the depth of the second-conductivity-type junction regions 140 can be about 0.6 pm. Through ion implantation, the plurality of second-conductivity-type junction regions 140 can be formed to extend from the upper surface of the first-conductivity-type charge injection layer 130' into the first-conductivity-type charge injection layer 130'. The ratio of the area occupied by the second-conductivity-type junction regions 140 in the active region can be at least 62% and at most 82%.

[0035] The second-conductivity-type buffer region 150 can be formed on the entire active region on the upper surface of the first-conductivity-type epitaxial layer 120 and the edge termination region, and enclose the active region. Specifically, in the horizontal direction, one end of the second-conductivity-type buffer region 150 extends beyond the insulating layer 160 and contacts the Schottky metal layer 170, and the other end of the second-conductivity-type buffer region 150 extends toward the edge termination region. The second-conductivity-type buffer region 150 that extends to the edge termination region contacts the insulating layer 160, but does not extend beyond the insulating layer 160. The second-conductivity-type buffer region 150 can be formed by implanting second-conductivity-type impurity ions into the first-conductivity-type charge injection layer 130' (see Figure 2 ). The width of the second-conductivity-type buffer region 150 can be wider than the width of the second-conductivity-type junction region 140. The second-conductivity-type buffer region 150 has a function of dispersing an electric field and maintaining the breakdown voltage of the device.

[0036] The insulating layer 160 can be formed on a portion of the buffer layer 150 and the first-conductivity-type epitaxial layer 120 in the edge termination region. The insulating layer 160 can be formed so as to enclose the plurality of second-conductivity-type junction regions 140 to define the active region. The insulating layer 160 can be formed so as to overlap at least a portion of the second-conductivity-type buffer region 150. The insulating layer 160 can be formed of silicon oxide, phosphorus silicate glass (PSG), boron silicate glass (BSG), boron phosphorus silicate glass (BPSG), or the like.

[0037] The Schottky metal layer 170 can be formed on the first-conductivity-type epitaxial layer 120, contact the upper surfaces of the plurality of second-conductivity-type junction regions 140, and form a Schottky junction with a portion of the first-conductivity-type epitaxial layer 120. The Schottky metal layer 170 can extend in the horizontal direction so as to cover a portion of the insulating layer 160.

[0038] The anode electrode 180 can be formed above the Schottky metal layer 170, and the cathode electrode 190 can be formed below the first-conductivity-type substrate 110. The anode electrode 180 and the cathode electrode 190 can be formed of a metal or a metal alloy. A silicide layer (not shown) for ohmic contact can be formed between the first-conductivity-type substrate 110 and the cathode electrode 190.

[0039] The operation of the above-described SiC SBD 100 will be described.

[0040] The plurality of second-conductivity-type junction regions 140 form PN junctions with the first-conductivity-type charge injection region 130. Therefore, the plurality of second-conductivity-type junction regions 140 and the first-conductivity-type charge injection region 130 perform the same function as a PiN diode. That is, the SiC SBD 100 has a structure in which a junction barrier Schottky diode (hereinafter referred to as an SBD) and a PiN diode are connected in parallel.

[0041] In the off-state of the SiC SBD 100, both the SBD and the PiN diode maintain an off-state voltage. Since the depth from the lower portion of the PiN diode to the first-conductivity-type substrate 110 is smaller than the depth from the lower portion of the SBD to the first-conductivity-type substrate 110, a relatively strong off-state electric field is applied to the PiN diode, and thus a relatively weak off-state electric field is applied to the SBD. In other words, due to the PiN diode, the electric field applied to the interface of the Schottky junction is reduced, thereby reducing the leakage current.

[0042] The on-voltage of the PiN diode is relatively high compared to the on-voltage of the SBD. In the on-state, when the forward voltage V F applied to the parallelly connected PiN diode and SBD, the current starts to flow through the SBD having a relatively low on-voltage. Then, when the forward voltage V F increases above the on-voltage of the PiN diode, the current flows through both the PiN diode and the SBD. Therefore, in the known JBS diode, the current density characteristic in the on-state is reduced compared to the conventional SBD in which the current flows through the entire active region. On the other hand, in the SiC SBD 100 of one embodiment of the present application, the charge injection region 130 increases the current density, and thus even if the area of the second-conductivity-type junction region 140 is increased, the current density substantially the same as that of the known JBS diode can be achieved.

[0043] Figure 2 A process of manufacturing the SIC SBD shown exemplarily. The charge injection region 130 can be formed by ion implantation or a multi-epitaxy process. Hereinafter, a process of manufacturing the SiC SBD by using the multi-epitaxy process will be described. Figure 1 The SIC SBD shown exemplarily. The charge injection region 130 can be formed by ion implantation or a multi-epitaxy process. Hereinafter, a process of manufacturing the SiC SBD by using the multi-epitaxy process will be described.

[0044] In step (a), a first-conductivity-type charge injection layer 130' can be formed on an upper surface of the first-conductivity-type epitaxial layer 120. The first-conductivity-type epitaxial layer 120 is epitaxially grown on an upper surface of the first-conductivity-type substrate 110. The first-conductivity-type substrate 110 has a depth of about 5 pm, and can be doped with first-conductivity-type impurities at a concentration of about 1E18 cm -2 -3. The first-conductivity-type epitaxial layer 120 has a depth of about 11 pm, and can be doped with first-conductivity-type impurities at a concentration of about 1E16 cm -2 -3.

[0045] The doping concentration of the first-conductivity-type charge injection layer 130' can be uniform regardless of the depth, or the doping concentration of the first-conductivity-type charge injection layer 130' can vary with the depth. The first-conductivity-type charge injection layer 130' can be a plurality of epitaxial layers 130a' and 130b'. The doping concentration of the first epitaxial layer 130a' and the second epitaxial layer 130b' can be different. For example, the doping concentration of the first epitaxial layer 130a' can be lower than the doping concentration of the second epitaxial layer 130b'.

[0046] The depth of the first-conductivity-type charge injection layer 130' can vary depending on the number of the epitaxial layers 130a' and 130b'. For example, the number of the epitaxial layers 130a' and 130b' can be 2 to 5. Accordingly, the depth of the first-conductivity-type charge injection layer 130' can be about 0.6 μm to about 1.0 μm.

[0047] In step (b), a plurality of second-conductivity-type junction regions 140 can be formed in the first-conductivity-type charge injection layer 130'. At the same time, the second-conductivity-type buffer region 150 can be formed simultaneously with the plurality of second-conductivity-type junction regions 140. A photoresist is applied to the upper surface of the first-conductivity-type epitaxial layer 120, and the photoresist located in the region to be ion implanted is removed. Thereafter, second-conductivity-type impurities can be implanted. At the same time, a plurality of guard rings can be formed in the second-conductivity-type buffer region 150.

[0048] In step (c), an insulating layer 160 can be formed on the upper surface of the first-conductivity-type epitaxial layer 120, and a Schottky metal layer 170 can be formed in the active region. The insulating layer 160 can be formed by forming an insulating film of silicon oxide, PSG, BSG, BPSG, etc. on the entire upper surface of the first-conductivity-type epitaxial layer 120, and then removing the insulating film corresponding to the active region. The Schottky metal layer 170 can be formed of a material having a low energy barrier, or can be formed of an alloy of two or more metals, for example, the Schottky metal layer 170 can be formed of any one or a combination of titanium, chromium, polysilicon, aluminum, and tantalum.

[0049] In step (d), an anode electrode 180 can be formed on the Schottky metal layer 170, respectively, and a cathode electrode 190 can be formed under the first-conductivity-type substrate 110. The electrodes can be formed of, for example, aluminum.

[0050] Figure 3 is an exemplary view illustrating a unit cell of an active region of the SIC SBD. Figure 1 is a cross-sectional view of one embodiment of a unit cell of an active region of the SIC SBD.

[0051] Reference will now be made to Figure 3, SiC SBD 100 can include a charge injection region 130 doped at a uniform concentration. The charge injection region 130 can be formed by doping, for example, a first conductivity type impurity at a concentration of about 1E16 cm -2 -3. The unit cell pitch of the SiC SBD 100 is about 3.5 μm, and the ratio between the width W n-epi of the charge injection region 130 within the unit cell pitch and the width 2 x W p+ of the second conductivity type junction region 140 is 1.0:2.5. Hereinafter, it is assumed that the unit cell pitch of the SiC SBD 100 is 3.5 μm, and the width of the second conductivity type junction region 140 is referred to as RJBS. The width W n-epi of the charge injection region 130 can be about 1.0 μm, and the depth D P+ may be about 0.6 μm. The RJBS can be about 2.5 μm, and the depth of the second conductivity type junction region 140 can be about 0.6 μm. The second conductivity type junction region 140 can be formed by doping, for example, a second conductivity type impurity at a concentration of about 1E18 cm -2 -3. Meanwhile, the depth D epi from the upper surface of the first conductivity type substrate 110 to the upper surface of the second conductivity type junction region 140 can be about 12 μm.

[0052] The above design parameters are selected in order to compare with a known JBS diode. Except for the charge injection region 130, the depth of the first conductivity type epitaxial layer 120, and the RJBS, the design parameters are the same in both the known JBS diode and the SiC SBD 100. In the known JBS diode, when the depth of the first conductivity type epitaxial layer is about 12 μm, the RJBS is about 1.24 μm, and the forward voltage V F is about 0.76 V, a current of about 10 A can flow. In order to flow a substantially same forward current by applying a substantially same forward voltage V F , the RJBS of the SiC SBD 100 is selected to be about 2.5 μm.

[0053] Figure 4 is an example of a cross-sectional view of another embodiment of a unit cell constituting an active region of the SiC SBD shown in Figure 1 .

[0054] Referring to Figure 4 , the SiC SBD 101 can include a charge injection region 130 composed of two multi-epitaxial layers 130a and 130b doped at different concentrations. The first multi-epitaxial layer 130a can be formed by doping, for example, a first conductivity type impurity at a concentration of about 3E16 cm -2of the first conductivity type is formed, and can have a depth of about 0.6 μm. The unit cell pitch of the SiC SBD 101 can be about 3.5 μm, and the RJBS can be about 2.6 μm. The second conductivity type junction region 140 can be formed by doping, for example, about 1E18 cm -2 of the first conductivity type is formed, and can have a depth of about 0.4 μm. The unit cell pitch of the SiC SBD 101 can be about 3.5 μm, and the RJBS can be about 2.6 μm. The second conductivity type junction region 140 can be formed by doping, for example, about 1E18 cm -2 of the second conductivity type is formed. The depth D P+ of the second conductivity type junction region 140 can be about 0.6 μm. Meanwhile, the depth D epi from the upper surface of the first conductivity type substrate 110 to the upper surface of the second conductivity type junction region 140 can be about 12 μm.

[0055] The above design parameters are selected in order to compare with a known JBS diode. The design parameters other than the charge injection region 130 and the RJBS are the same in both the known JBS diode and the SiC SBD 101. In the known JBS diode, when the depth of the first conductivity type epitaxial layer is about 12 μm, the RJBS is about 0.9 μm, and the forward voltage V F is about 0.66 V, a current of about 10 A can flow. In order to flow a forward current of 10 A by applying a forward voltage V F of 0.68 V, the RJBS of the SiC SBD 100 is selected to be about 2.6 μm.

[0056] Figure 5 is an example of a cross-sectional view of a unit cell constituting Figure 1 a further embodiment of a unit cell of the active region of the SiC SBD shown in FIG. 1.

[0057] Referring to Figure 5 , the SiC SBD 102 can have a charge injection region 130 composed of five multi-epitaxial layers 130a, 130b, 130c, 130d, and 130e doped at different concentrations. The first multi-epitaxial layer 130a can be formed by doping about 2E16 cm -2 of the first conductivity type, and can have a depth of about 0.1 μm. The second multi-epitaxial layer 130b can be formed by doping about 4E16 cm -2 of the first conductivity type, and can have a depth of about 0.15 μm. The third multi-epitaxial layer 130c can be formed by doping about 6E16 cm -2 of the first conductivity type, and can have a depth of about 0.2 μm. The fourth multi-epitaxial layer 130d can be formed by doping about 8E16 cm -2The fifth multi-epitaxy layer 130 can be formed by doping with a concentration of first conductivity type impurities and can have a depth of about 0.2 μm. -2 The first conductivity type impurity is formed at a concentration of approximately 0.3 μm, and the unit cell spacing of SiC SBD 102 can be approximately 3.5 μm, and the RJBS can be approximately 2.6 μm. The second conductivity type junction region 140 can be formed by doping, for example, at a concentration of approximately 1E18 cm⁻¹. -2 It is formed by the second conductivity type impurity. The depth D of the second conductivity type junction region 140 is... P+ The depth can be approximately 0.6 μm. Simultaneously, the depth from the lower surface of the charge injection region 130 to the upper surface of the first conductivity substrate 110, i.e., the depth of the first conductivity epitaxial layer 120, can be approximately 11 μm. The depth of the first conductivity epitaxial layer 120 can vary depending on the required breakdown voltage. Typically, in 650V diodes, the depth of the first conductivity epitaxial layer 120 is designed to be approximately 5 μm to approximately 7 μm; in 1200V diodes, the depth is designed to be approximately 10 μm to approximately 12 μm; and in 1700V diodes, the depth is designed to be approximately 15 μm or greater.

[0058] The above design parameters were chosen for comparison with known JBS diodes. Except for the charge injection region 130 and the RJBS, the design parameters are identical in both known JBS diodes and the SiC SBD 102. In known JBS diodes, when the depth of the first conductivity epitaxial layer is approximately 12 μm, and that of the RJBS is approximately 0.9 μm, the forward voltage V... F At a voltage of approximately 1.16V, a current of approximately 10A can flow. To achieve this, a forward voltage V... F To enable a forward current of 10A to flow at approximately 1.18V, the RJBS of SiC SBD102 was selected to be approximately 2.6μm.

[0059] Figure 6 , Figure 7 , Figure 8 and Figure 9 It is shown as an example Figures 3 to 5 The graph shows the electrical characteristics of SiC SBD.

[0060] Figure 6 The application is shown. Figures 3 to 5 The vertical electric fields of SiC SBD 100, 101 and 102 are shown. Figure 7 The horizontal electric field is shown. The vertical electric field is the electric field distributed between the Schottky junction and the lower surface of the first conductivity type substrate 110 (by...). Figures 3 to 5The Y-Cut in the diagram represents the horizontal electric field, which is the electric field distributed between the lower surfaces of the two second conductivity type junction regions 140 (as indicated by...). Figures 3 to 5 (X-Cut in the text). The known JBS diodes to be compared have... Figures 3 to 5 The design parameters described in the document.

[0061] Observation shows the electric field in the vertical direction. Figure 6 When plotting the curves, the electric field strength tends to decrease-increase-decrease vertically from the Schottky junction. The electric field strength decreases substantially linearly in the first conductivity type epitaxial layer beyond the region where the electric field is concentrated through the second conductivity type junction region, and essentially disappears in the first conductivity type substrate. This trend has been observed in known JBS and SiC SBDs 100, 101, and 102. However, there are significant differences in the electric field strength at (or near) the Schottky junction. The electric field strength at the Schottky junction in known JBS diodes is approximately 2e+06 V / cm or more, while in SiC SBD 100 with a charge-injected region doped at a single concentration, the electric field strength at the Schottky junction is approximately 1.9e+05 V / cm, and in SiC SBD 101 with a charge-injected region consisting of two multi-epilayers, the electric field strength at the Schottky junction is approximately 1.5e+05 V / cm. Even in SiC SBD102 with a charge-injection region consisting of five multi-epitaxial layers, the electric field strength at the Schottky junction drops to approximately 1.3e+0.5 V / cm. The electric field strength at the Schottky junction is the primary factor contributing to the leakage current of the Schottky diode, and the leakage current decreases as the electric field strength decreases.

[0062] The electric field in the horizontal direction is shown. Figure 7 The same phenomenon was observed. In known JBS diodes with relatively large distances between the second conductivity type junction regions, the electric field strength between the opposing junction regions remains essentially constant due to the distance between them. On the other hand, as the width of the second conductivity type junction region increases, the distance between the junction regions with the maximum electric field strength decreases. As a result, the electric field formed between the junction regions continues to decrease, and the electric field strength at the center of the unit cell becomes relatively weaker than that of the known JBS diode. Therefore, the strength of the electric field applied to the Schottky junction is relatively smaller compared to the electric field in the known JBS diode.

[0063] Figure 8 The leakage current is shown. Figure 9 It shows Figures 3 to 5 The breakdown voltages in SiC SBDs 100, 101, and 102 are shown. (As shown from...) Figure 6 and Figure 7The rate of increase of the leakage current of the SiC SBDs 100, 101, and 102, which can form the charge injection region 130, is significantly lower than that of the known JBS diode, as can be seen from the graph of the electric field intensity predicted by the simulation. In addition, in observing the breakdown voltage, the breakdown voltage of the known JBS diode is about -1430 V, while the breakdown voltage of the SiC SBDs 100, 101, and 102, which can form the charge injection region 130, is about -1700 V.

[0064] Figures 10 to 13 is an exemplary graph showing the electric characteristics of the SiC SBD based on the doping concentration shown in Figure 5

[0065] Based on the doping concentration shown in Figure 5 , the doping concentration of the SiC SBD is changed to 60%, 80%, 120%, and 140% of the reference concentration profile. The depths of the first to fifth poly-epitaxial layers 130a to 130e and the RJBS are not changed. The concentration profiles that are increased and decreased by 20% increments are shown in Table 1. The design parameters other than the doping concentration profile are the same as those of the embodiment shown in Figure 5

[0066] Table 1

[0067]

[0068] Figure 10 shows the characteristics of the forward voltage V F and the forward current I F of the SiC SBDs formed according to the five concentration profiles shown in Table 1. As shown in the graph, it can be seen that the change in the doping concentration does not significantly affect the forward voltage-current characteristics.

[0069] Figure 11 shows the vertical electric field of the SiC SBDs formed according to the five concentration profiles shown in Table 1, Figure 12 shows the horizontal electric field. Referring to Figure 11 , it can be seen that the electric field intensity at the Schottky junction decreases as the doping concentration increases. It can be seen that the electric field intensity at the Schottky junction is weaker than the case where the charge injection region can be formed with a single concentration for all the vertical electric fields of the SiC SBDs based on the five concentration profiles. On the other hand, it can be seen that the electric field intensity at the Schottky junction in the vertical electric field at a relatively low concentration profile (60% and 80%) is relatively high or almost similar to the case where the charge injection region is formed by two poly-epitaxial layers. As previously Figure 6 ​​As shown, the electric field intensity in the vertical direction of the SiC SBD having the charge injection region is minimum near the lower edge of the second conductivity type junction region, then rapidly increases to a maximum, and decreases almost linearly across the first conductivity type epitaxial layer.

[0070] Referring to Figure 12 , the horizontal electric field of the SiC SBD based on the five concentration configurations tends to have a maximum electric field intensity, and the width therebetween is narrow and extends vertically downward. According to the electric field intensity based on the reference concentration configuration, the horizontal electric field based on the relatively low concentration configuration has a relatively wide width between the maximum electric field intensities, while the horizontal electric field based on the relatively high concentration configuration has a relatively narrow width between the maximum electric field intensities. It can be seen that the electric field intensity applied between the junction regions increases as the doping concentration increases.

[0071] Referring to Figure 13 , as predicted from Figure 11 and Figure 12 , it can be seen that the leakage current decreases as the doping concentration increases. According to the leakage current curve based on the reference concentration configuration as a reference, the rate of increase of the leakage current is greater than that of the reference concentration configuration for the relatively low concentration configuration, and increases almost linearly over a certain range. On the other hand, in the relatively high concentration configuration, although the size of the overall leakage current is smaller than that of the reference concentration configuration, it tends to increase non-linearly.

[0072] Figure 14 and Figure 15 are graphs exemplarily showing the function of the charge injection region.

[0073] The charge injection region increases the current density. When the charge injection region can be formed over the entire upper portion of the first conductivity type epitaxial layer, the amount of current passing through the first conductivity type epitaxial layer increases, and a thermal runaway phenomenon can occur. The thermal runaway can increase the temperature of the package and cause damage to the surrounding region, and in particular, it is a major factor in increasing the leakage current. Therefore, it is necessary to form the second conductivity type junction region in the charge injection region to prevent excessive current flow.

[0074] The degree to which the charge injection region increases the current density can vary depending on the concentration configuration of the multi-epitaxial layer. Figure 14 The results of adjusting the RJBS are shown such that the forward voltage V F is about 1.18 V, and the forward current I F is about 10 A. For the five concentration configurations in which the depth of the second conductivity type junction region is equal to about 0.6 μm, the forward voltage V F of about 1.18 V and the forward current I FRJBS. As shown, for a relatively low concentration configuration than the reference concentration configuration, the RJBS should decrease, and conversely, for a relatively high concentration configuration, the RJBS should increase, so that VF= 1.18 V and IF= 10 can be satisfied. From these measurement results, it can be confirmed that the charge injection region increases the current density.

[0075] Meanwhile, Figure 15 shows the forward voltage V F when the forward current I F becomes about 10 A, while the RJBS is fixed at 2.1 μm. For five concentration configurations in which the depth of the second conductivity junction region is equal to about 0.6 μm, the forward voltage V F when the forward current I F is about 10 A is measured. As shown, it can be seen that the forward voltage V F decreases as the concentration configuration increases. As Figure 14 shown, from these measurement results, it can be confirmed that the charge injection region increases the current density.

[0076] Figure 16 and Figure 17 is a graph exemplarily showing the electrical characteristics according to the depth of the second conductivity junction region.

[0077] Figure 16 shows the measurement results of the leakage current for each of the five concentration configurations in which the depth of the charge injection region is fixed at about 0.95 μm, while the RJBS becomes 2.2, 2.4, 2.6, 2.8, 2.9 μm and the depth of the second conductivity junction region becomes about 0.4, 0.6 and 0.8 μm. The leakage current is measured when the reverse voltage V B is about -1200 V. The curve 200 represents the RJBS, the curve 201 represents the measured value of the leakage current when the depth of the second conductivity junction region is about 0.4 μm, the curve 202 represents the measured value of the leakage current when the depth of the second conductivity junction region is about 0.6 μm, and the curve 203 represents the measured value of the leakage current when the depth of the second conductivity junction region is about 0.8 μm. For example, when the RJBS is 2.2 μm, the measured leakage current tends to decrease as the second conductivity junction region becomes deeper.

[0078] On the other hand, the leakage current tends to decrease as the doping concentration increases or the RJBS increases.

[0079] Figure 17 shows the forward voltage V FThe measured values ​​were obtained, where the depth of the charge injection region was fixed at approximately 0.95 μm, while the RJBS depths were changed to 2.2, 2.4, 2.6, 2.8, and 2.9 μm, and the depths of the second conductive junction region were changed to approximately 0.4, 0.6, and 0.8 μm. Under a forward current I... F The forward voltage V is measured at approximately 10A. F Curve 210 represents the RJBS, and curve 211 represents the forward voltage V when the depth of the second conductivity junction region is approximately 0.4 μm. F The measured values, curve 212, represent the forward voltage V when the depth of the second conductivity junction region is approximately 0.6 μm. F The measured values, curve 213, represent the forward voltage V when the depth of the second conductivity junction region is approximately 0.8 μm. F The measured values. For example, when the RJBS is approximately 2.2 μm, the measured forward voltage V increases as the second conductivity junction region becomes deeper. F The forward voltage V tends to increase. On the other hand, with the increase of doping concentration or RJBS, the forward voltage V... F The trend is increasing.

[0080] The above description of the present invention is exemplary, and those skilled in the art will understand that the present invention can be modified in other forms without changing the technical concept or basic characteristics of the present invention. Therefore, it should be understood that the above embodiments are exemplary in all respects, but not limiting.

[0081] The scope of this invention is defined by the appended claims, rather than by the detailed description above, and should be interpreted as including all variations and modifications derived from the meaning and scope of the claims and their equivalents.

Claims

1. A unit cell constituting an active region of a silicon carbide junction barrier Schottky diode, comprising: a first conductivity type substrate; a first conductivity type epitaxial layer formed by epitaxial growth of silicon carbide doped with a first conductivity type impurity on the first conductivity type substrate; a charge injection region defined by a second conductivity type junction region formed by implanting a second conductivity type impurity ion into a first conductivity type charge injection layer formed by epitaxial growth of silicon carbide doped with a higher concentration of the first conductivity type impurity than a concentration of the first conductivity type impurity of the first conductivity type epitaxial layer on the first conductivity type epitaxial layer; a Schottky metal layer formed on the charge injection region and the second conductivity type junction region; an anode electrode formed on the Schottky metal layer; and a cathode electrode formed below the first conductivity type substrate, wherein the first conductivity type charge injection layer comprises two or more multiple epitaxial layers having different first conductivity type impurity concentrations, wherein the first conductivity type impurity concentrations of the two or more multiple epitaxial layers decrease according to a reference concentration profile in a direction toward the first conductivity type epitaxial layer.

2. The unit element of claim 1, wherein, The second conductivity type junction region occupies an area in the unit cell in a range between 62% and 82%.

3. The unit element of claim 1, wherein, The reference concentration profile defines the first conductivity type impurity concentrations of the two or more multiple epitaxial layers.

4. The unit element of claim 3, wherein, The reference concentration profile causes impurity concentrations to decrease by 20% in a direction toward the first conductivity type epitaxial layer.

5. The unit element of claim 3, wherein, In the reference concentration profile, the first conductivity type impurity concentration of each of the two or more multiple epitaxial layers increases by at most 40% or decreases by at most 40% equally.

6. The unit element of claim 3, wherein, The depths of the two or more multiple epitaxial layers decrease in a direction toward the first conductivity type epitaxial layer.

7. The unit element of claim 1, wherein, The depth of the second conductivity type junction region is in a range between 60% and 100% of the depth of the charge injection region.

8. A silicon carbide junction barrier Schottky diode having an active region, comprising: a first conductivity type substrate; a first conductivity type epitaxial layer formed by epitaxial growth of silicon carbide doped with a first conductivity type impurity on the first conductivity type substrate; a charge injection region formed on the first conductivity type epitaxial layer and doped with a higher concentration of the first conductivity type impurity than a concentration of the first conductivity type impurity of the first conductivity type epitaxial layer; a second conductivity type junction region formed on the first conductivity type epitaxial layer to contact the charge injection region; a Schottky metal layer formed on the charge injection region and the second conductivity type junction region; an anode electrode formed on the Schottky metal layer; and a cathode electrode formed below the first conductivity type substrate, wherein the first conductivity type charge injection layer comprises two or more multiple epitaxial layers having different first conductivity type impurity concentrations, wherein the first conductivity type impurity concentrations of the two or more multiple epitaxial layers decrease according to a reference concentration profile in a direction toward the first conductivity type epitaxial layer. wherein the first-conductivity-type charge injection layer is formed by epitaxial growth on the first-conductivity-type epitaxial layer of silicon carbide doped with a higher concentration of first-conductivity-type impurities than the concentration of first-conductivity-type impurities of the first-conductivity-type epitaxial layer, wherein the first-conductivity-type charge injection layer comprises two or more multiple epitaxial layers having different concentrations of first-conductivity-type impurities, wherein the concentration of first-conductivity-type impurities of the two or more multiple epitaxial layers decreases according to a reference concentration profile in a direction toward the first-conductivity-type epitaxial layer.

9. The silicon carbide junction barrier Schottky diode of Claim 8 wherein, The second-conductivity-type junction region occupies an area in the active region in a range between 62% and 82%.

10. The silicon carbide junction barrier Schottky diode of Claim 8 wherein, The reference concentration profile defines the concentration of first-conductivity-type impurities of the two or more multiple epitaxial layers.

11. The silicon carbide junction barrier Schottky diode of Claim 8 wherein, The depth of the two or more multiple epitaxial layers decreases in a direction toward the first-conductivity-type epitaxial layer.

12. The silicon carbide junction barrier Schottky diode of Claim 8 wherein, The depth of the second-conductivity-type junction region is in a range between 60% and 100% of the depth of the charge injection region. The reference concentration profile defines the concentration of first-conductivity-type impurities of the two or more multiple epitaxial layers. The depth of the two or more multiple epitaxial layers decreases in a direction toward the first-conductivity-type epitaxial layer. The depth of the second-conductivity-type junction region is in a range between 60% and 100% of the depth of the charge injection region.

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