schottky barrier diode

Abstract

The present application aims to prevent peeling at the interface between the anode electrode and the protective film in a Schottky barrier diode using gallium oxide. A Schottky barrier diode (11) includes a semiconductor substrate (20) made of gallium oxide; a drift layer (30) made of gallium oxide provided on the semiconductor substrate (20); an anode electrode (40) in Schottky contact with the drift layer (30); a cathode electrode (50) in ohmic contact with the semiconductor substrate (20); an insulating film (63) covering the inner wall of a trench (61) provided in the drift layer (30); and a protective film (70) covering the anode electrode (40), a portion (72) of the protective film (70) being embedded in the trench (61). Thus, a portion (72) of the protective film (70) is embedded in the trench (61), and therefore the adhesion of the anode electrode (40) to the protective film (70) is improved. As a result, peeling at the interface between the anode electrode (40) and the protective film (70) can be prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to a Schottky barrier diode, and particularly to a Schottky barrier diode using gallium oxide. BACKGROUND

[0002] A Schottky barrier diode is a rectifying element that utilizes a Schottky barrier generated by the junction of a metal and a semiconductor, and has a low forward voltage and a fast switching speed compared to a general diode having a PN junction. Therefore, the Schottky barrier diode is sometimes used as a switching element for a power device.

[0003] In the case where the Schottky barrier diode is used as a switching element for a power device, since it is necessary to ensure a sufficient reverse withstand voltage, there are cases where silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3), or the like having a larger band gap than silicon (Si) is used instead of Si. Among them, the band gap of gallium oxide is very large, at 4.8 to 4.9 eV, and the dielectric breakdown field is also large, at about 8 MV / cm, and therefore, the Schottky barrier diode using gallium oxide is very promising as a switching element for a power device. Examples of the Schottky barrier diode using gallium oxide are described in Patent Documents 1 and 2.

[0004] In the Schottky barrier diodes described in Patent Documents 1 and 2, a plurality of grooves are provided in the gallium oxide layer. If a plurality of grooves are thus provided in the gallium oxide layer, the mesa region located between the grooves becomes a depletion layer at the time of application of a reverse voltage, and therefore, the channel region of the drift layer is pinched off. Thus, the leakage current at the time of application of a reverse voltage can be greatly suppressed.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Publication No. 2017-199869

[0008] Patent Document 2: Japanese Patent Application Publication No. 2019-79984 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In an actual device, a protective film is provided on the anode electrode, thereby ensuring the insulating property from the external circuit. However, the adhesion of the anode electrode composed of a metal to the protective film composed of SiN or the like is low, and there is a problem that peeling easily occurs at the interface between the two.

[0011] Therefore, an object of the present application is to prevent peeling at the interface between the anode electrode and the protective film in a Schottky barrier diode using gallium oxide.

[0012] Means for solving technical problems

[0013] The Schottky barrier diode of the present application is characterized by comprising: a semiconductor substrate composed of gallium oxide; a drift layer composed of gallium oxide provided on the semiconductor substrate; an anode electrode in Schottky contact with the drift layer; a cathode electrode in ohmic contact with the semiconductor substrate; an insulating film covering inner walls of trenches provided in the drift layer; and a protective film covering the anode electrode, a portion of the protective film being embedded in the trenches.

[0014] According to the present application, a portion of the protective film is embedded in the trenches, and thus the adhesion of the anode electrode to the protective film is improved. Thereby, peeling at the interface of the anode electrode and the protective film can be prevented.

[0015] In the present application, the trenches can be formed in a ring shape and embedded with a portion of the protective film and a metal member electrically connected to the anode electrode. Thereby, the electric field applied to the drift layer can be moderated by the ring-shaped trenches.

[0016] In this case, the trenches can have flat side wall portions, and the boundary of the protective film and the metal member can be located at the side wall portions; or the trenches can have flat bottom surface portions, and the boundary of the protective film and the metal member can be located at the bottom surface portions. Thereby, the electric field applied to the drift layer can be moderated near the end portions of the metal member.

[0017] Effects of the invention

[0018] Thus, according to the present application, peeling at the interface of the anode electrode and the protective film can be prevented in a Schottky barrier diode using gallium oxide. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic plan view showing the structure of a Schottky barrier diode 11 according to a first embodiment of the present application.

[0020] Figure 2 is a schematic cross-sectional view taken along the line A-A shown in Figure 1 .

[0021] Figure 3 is a process diagram for explaining a manufacturing method of the Schottky barrier diode 11.

[0022] Figure 4 is a process diagram for explaining a manufacturing method of the Schottky barrier diode 11.

[0023] Figure 5 is a process diagram for explaining a manufacturing method of the Schottky barrier diode 11.

[0024] Figure 6 is a process diagram for explaining a manufacturing method of the Schottky barrier diode 11.

[0025] Figure 7 is a process diagram for explaining a manufacturing method of the Schottky barrier diode 11.

[0026] Figure 8 is a process diagram for explaining a manufacturing method of the Schottky barrier diode 11.

[0027] Figure 9 is a schematic plan view showing the structure of the Schottky barrier diode 12 of the second embodiment of the present application.

[0028] Figure 10 is a schematic cross-sectional view taken along Figure 9 the B-B line shown in FIG. 6.

[0029] Figure 11 is a schematic cross-sectional view showing the structure of the Schottky barrier diode 13 of the third embodiment of the present application.

[0030] Figure 12 is a schematic cross-sectional view showing the structure of the Schottky barrier diode 14 of the fourth embodiment of the present application.

[0031] Figure 13 is a schematic cross-sectional view showing the structure of the Schottky barrier diode 15 of the fifth embodiment of the present application.

[0032] Figure 14 is a schematic cross-sectional view showing the structure of the Schottky barrier diode 15A of the modification of the fifth embodiment.

[0033] Figure 15 is a schematic cross-sectional view showing the structure of the Schottky barrier diode 16 of the sixth embodiment of the present application.

[0034] Figure 16 is a schematic cross-sectional view showing the structure of the Schottky barrier diode 17 of the seventh embodiment of the present application.

[0035] Figure 17 is a graph showing the simulation results of Example 1.

[0036] Figure 18 is a graph showing the simulation results of Example 2.

[0037] Figure 19 is a graph showing the simulation results of Example 3. DETAILED DESCRIPTION

[0038] Hereinafter, the preferred embodiments of the present application will be explained in detail with reference to the accompanying drawings.

[0039] <First Embodiment>

[0040] Figure 1 is a schematic plan view showing the structure of a Schottky barrier diode 11 according to a first embodiment of the present application. Further, Figure 2 is a schematic cross-sectional view taken along Figure 1 the A-A line shown in Fig. 1.

[0041] As shown in Figs. 1 and 2, Figure 1 and Figure 2 the Schottky barrier diode 11 according to the present embodiment is provided with a semiconductor substrate 20 and a drift layer 30, each of which is composed of gallium oxide (β-Ga2O3). In the semiconductor substrate 20 and the drift layer 30, silicon (Si) or tin (Sn) is introduced as an n-type dopant. The concentration of the dopant is higher in the semiconductor substrate 20 than in the drift layer 30, whereby the semiconductor substrate 20 functions as an n + layer and the drift layer 30 functions as an n - layer.

[0042] The semiconductor substrate 20 is a substrate obtained by cutting a bulk crystal formed by a melt growth method or the like, and has a thickness of about 250 μm. The planar size of the semiconductor substrate 20 is not particularly limited, and is generally selected in accordance with the amount of current flowing in the element, and if the maximum amount of forward current is about 20 A, the planar size can be about 2.4 mm x 2.4 mm in plan view.

[0043] The semiconductor substrate 20 has an upper surface 21 on the upper surface side at the time of mounting and a back surface 22 on the lower surface side at the time of mounting on the opposite side of the upper surface 21. The drift layer 30 is formed on the entire surface of the upper surface 21. The drift layer 30 is a thin film obtained by epitaxial growth of gallium oxide on the upper surface 21 of the semiconductor substrate 20 using reactive sputtering, a PLD method, an MBE method, an MOCVD method, an HVPE method or the like. The film thickness of the drift layer 30 is not particularly limited, and is generally selected in accordance with the reverse withstand voltage of the element, and in order to ensure a withstand voltage of about 600 V, for example, it can be set to about 7 μm.

[0044] On the upper surface 31 of the drift layer 30, an anode electrode 40 is formed in Schottky contact with the drift layer 30. The anode electrode 40 is composed of, for example, a metal such as platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), molybdenum (Mo), copper (Cu) or the like. The anode electrode 40 can also be a multilayer structure in which different metal films are stacked, such as Pt / Au, Pt / Al, Pd / Au, Pd / Al, Pt / Ti / Au or Pd / Ti / Au. On the other hand, on the back surface 22 of the semiconductor substrate 20, a cathode electrode 50 is provided in ohmic contact with the semiconductor substrate 20. The cathode electrode 50 is composed of, for example, a metal such as titanium (Ti) or the like. The cathode electrode 50 can also be a multilayer structure in which different metal films are stacked, such as Ti / Au or Ti / Al.

[0045] In this embodiment, an annular peripheral groove 61 is provided in the drift layer 30. The inner wall of the peripheral groove 61 has an outer sidewall portion S1, an inner sidewall portion S2, and a bottom portion B. In this embodiment, the sidewall portions S1, S2, and the bottom portion B are all flat, and the corner portion C at the boundary between the sidewall portions S1, S2 and the bottom portion B has a curved shape. The inner wall of the peripheral groove 61 is covered by an insulating film 63 made of HfO2 or the like. In addition to HfO2, insulating materials such as Al2O3 can also be used as the material of the insulating film 63. A metal component 41 is embedded in most of the peripheral groove 61. The metal component 41 can be part of the anode electrode 40, that is, it can be made of the same metal material as the anode electrode 40, or it can be made of a different metal material than the anode electrode 40.

[0046] Furthermore, the outer periphery of the anode electrode 40 is covered by a protective film 70. The protective film 70 is made of resin materials such as epoxy resin, acrylic resins such as polymethyl methacrylate, polyurethane, polyimide, polyvinyl alcohol, fluoropolymers, and polyolefins, or inorganic insulating materials such as inorganic oxide films or inorganic nitride films, such as silicon oxide, alumina, and silicon nitride. It has an opening 71 that exposes the center portion of the connecting wires in the anode electrode 40. The protective film 70 serves to protect the anode electrode 40 and ensure insulation from external circuitry.

[0047] like Figure 2 As shown, in the Schottky barrier diode 11 of this embodiment, a portion 72 of the protective film 70 is embedded in the peripheral trench 61. Although the adhesion between the anode electrode 40 made of metal and the protective film 70 made of SiN or the like is low, and peeling is prone to occur at the interface between the two, in this embodiment, since a portion 72 of the protective film 70 is embedded in the peripheral trench 61, the adhesion is improved compared to the case where the anode electrode 40 and the protective film 70 are in contact with a plane. This prevents peeling at the interface between the anode electrode 40 and the protective film 70.

[0048] Furthermore, in this embodiment, the portion 72 of the protective film 70 embedded in the outer peripheral groove 61, where the boundary between the metal component 41 and the insulating film 63 is located at the outer sidewall portion S1. As described above, the sidewall portion S1 is a flat surface; therefore, the boundary between the protective film 70 and the metal component 41, i.e., the end of the metal component 41, terminates on a flat surface. Thus, compared to the case where the metal component 41 terminates on a curved surface such as a corner C, the electric field applied to the drift layer 30 can be mitigated near the end of the metal component 41.

[0049] Next, the manufacturing method of the Schottky barrier diode 11 of this embodiment will be described.

[0050] Figures 3-8These are process diagrams illustrating the manufacturing method of the Schottky barrier diode 11 in this embodiment, and they are all related to... Figure 2 The cross-section shown corresponds to this.

[0051] First, such as Figure 3 As shown, a semiconductor substrate 20 made of gallium oxide is prepared, and a drift layer 30 made of gallium oxide is formed on its upper surface 21. As described above, the drift layer 30 can be formed by epitaxial growth of gallium oxide on the upper surface 21 of the semiconductor substrate 20 using reactive sputtering, PLD, MBE, MOCVD, HVPE, or the like.

[0052] Next, as Figure 4 As shown, an annular peripheral trench 61 is formed in the drift layer 30 by dry etching using BCl3 or the like. At this time, the etching conditions are set such that at least the sidewall portions S1 and S2 are substantially vertical flat surfaces. Preferably, the etching conditions are also set such that the bottom portion B is substantially horizontal flat surface.

[0053] Next, as Figure 5 As shown, an insulating film 63 is formed on the surface of the drift layer 30. The insulating film 63 is formed using conventional film deposition methods such as ALD. Then, the insulating film 63 formed on the upper surface 31 of the drift layer 30 is removed using conventional processing methods such as wet etching, dry etching, and CMP. This results in the upper surface 31 of the drift layer 30 being exposed, and the inner walls of the peripheral trenches 61 being covered by the insulating film 63. At this point, a portion of the upper surface 31 of the drift layer 30 may also be removed.

[0054] Next, as Figure 6 As shown, the anode electrode 40 is formed over the entire surface. Alternatively, the metal component 41 filling the interior of the peripheral trench 61 can be made of a different material than the anode electrode 40. In this case, the anode electrode 40 can be formed first, and then other metal components 41 can be filled into the interior of the peripheral trench 61, provided that no metal component 41 different from the anode electrode 40 remains on the upper surface 31 of the drift layer 30. Alternatively, the interior of the peripheral trench 61 can be filled first with a metal component 41 different from the anode electrode 40. Thus, the metal component 41 embedded in the interior of the peripheral trench 61 is electrically connected to the anode electrode 40, achieving the same potential.

[0055] Then, as Figure 7As shown, a resist R is formed so as to cover the central portion of the anode electrode 40 and expose the outer peripheral portion. The patterning of the resist R can be performed using photolithography. Here, the outer edge E0 of the resist R is designed so as to be positioned between the outer edge E1 of the outer peripheral groove 61 and the inner edge E2 of the outer peripheral groove 61. That is, the outer diameter of the resist R is designed so as to be smaller than the outer diameter of the outer peripheral groove 61 and larger than the inner diameter of the outer peripheral groove 61.

[0056] Next, as shown in FIG. 6, the anode electrode 40 is etched using the resist R as a mask. In etching the anode electrode 40, a portion of the metal member 41 embedded in the outer peripheral groove 61 is removed by further performing over-etching after the upper surface 31 of the drift layer 30 is exposed, thereby forming a hollow 42. Thereafter, the resist R is removed. Figure 8

[0057] Then, as long as the cathode electrode 50 is formed on the back surface 22 of the semiconductor substrate 20, and a protective film 70 is formed so as to cover the anode electrode 40, a portion 72 of the protective film 70 is embedded in the hollow 42. In the case where a resin material is used as the protective film 70, a method of forming a resin film by applying a resin solution and then drying it, a method of performing polymerization after applying or vapor-depositing a resin monomer, or a method of performing cross-linking treatment after film formation can be used. Further, in the case where an inorganic insulating material is used as the protective film 70, a formation method using a vacuum process such as sputtering or vapor deposition, or a formation method using a solution process such as sol-gel method can be used. Thus, the Schottky barrier diode 11 of the present embodiment is completed.

[0058] As described above, in the Schottky barrier diode 11 of the present embodiment, because the portion 72 of the protective film 70 is embedded in the outer peripheral groove 61, the adhesion of the anode electrode 40 to the protective film 70 is improved. Thus, peeling at the interface between the anode electrode 40 and the protective film 70 can be prevented.

[0059] <Second Embodiment>

[0060] Figure 9 is a schematic plan view showing the structure of a Schottky barrier diode 12 of a second embodiment of the present application. Further, Figure 10 is a schematic cross-sectional view along the B-B line shown in Figure 9

[0061] As shown in Figure 9 and Figure 10 ​​As shown, the Schottky barrier diode 12 of the second embodiment differs from the Schottky barrier diode 11 of the first embodiment in that it has a plurality of central trenches 62 provided in the drift layer 30. Other basic structures are the same as those of the Schottky barrier diode 11 of the first embodiment; therefore, the same symbols are used for the same elements, and repeated descriptions are omitted.

[0062] The central groove 62 is formed in the area surrounded by the outer peripheral groove 61, and both are positioned where they overlap with the anode electrode 40 when viewed from above. The outer peripheral groove 61 and the central groove 62 do not need to be completely separated; they can be arranged as follows: Figure 9 As shown, the outer peripheral groove 61 is connected to the central groove 62.

[0063] The portion of the drift layer 30 divided by trenches 61 and 62 constitutes a mesa region M. When a reverse voltage is applied between the anode electrode 40 and the cathode electrode 50, the mesa region M becomes a depletion layer, thus pinching off the channel region of the drift layer 30. This significantly suppresses leakage current under reverse voltage conditions.

[0064] Although not specifically limited, in this embodiment, when the width of the outer peripheral groove 61 is set to W1 and the width of the central groove 62 is set to W2, W1 is set to > W2. This is to prevent insulation failure at the bottom of the outer peripheral groove 61 where the electric field is particularly concentrated. That is, this is because when the width W1 of the outer peripheral groove 61 is increased, the distance between the two corners C of the outer peripheral groove 61 increases when viewed in cross-section. As a result, insulation failure near the bottom of the outer peripheral groove 61 is less likely to occur. On the other hand, the depth of the outer peripheral groove 61 and the depth of the central groove 62 are different from each other.

[0065] In this embodiment, a portion 72 of the protective film 70 is also embedded inside the peripheral groove 61, thereby improving the adhesion between the anode electrode 40 and the protective film 70. As illustrated in this embodiment, when the drift layer 30 has a peripheral groove 61 and a central groove 62, peeling of the protective film 70 can be prevented by embedding a portion 72 of the protective film 70 inside the peripheral groove 61.

[0066] <Third Implementation Method>

[0067] Figure 11 This is a schematic cross-sectional view showing the structure of the Schottky barrier diode 13 according to the third embodiment of the present invention.

[0068] like Figure 11As shown, the Schottky barrier diode 13 of the third embodiment differs from the Schottky barrier diode 12 of the second embodiment in that the boundary between a portion 72 of the protective film 70 embedded in the peripheral trench 61 and the metal component 41 is located at the bottom part B. Other basic structures are the same as those of the Schottky barrier diode 12 of the second embodiment; therefore, the same symbols are used for the same elements, and repeated descriptions are omitted.

[0069] In this embodiment, a portion 72 of the protective film 70 is more deeply embedded in the peripheral groove 61, and the bottom of the portion 72 of the protective film 70 is in contact with the insulating film 63 covering the bottom surface B. Therefore, peeling of the protective film 70 can be prevented more effectively. Furthermore, as described above, the bottom surface B is a flat surface, so the boundary between the protective film 70 and the metal component 41, i.e., the end of the metal component 41, terminates on a flat surface. Thus, compared to the case where the metal component 41 terminates on a curved surface such as a corner C, the electric field applied to the drift layer 30 can be mitigated near the end of the metal component 41.

[0070] <Fourth Implementation>

[0071] Figure 12 This is a schematic cross-sectional view showing the structure of the Schottky barrier diode 14 according to the fourth embodiment of the present invention.

[0072] like Figure 12 As shown, the fourth embodiment of the Schottky barrier diode 14 differs from the second embodiment in that a portion 72 of the protective film 70 embedded in the peripheral trench 61 and the boundary of the metal component 41 are located on the inner sidewall portion S2. Other basic structures are the same as those of the second embodiment of the Schottky barrier diode 12; therefore, the same symbols are used for the same elements, and repeated descriptions are omitted.

[0073] In this embodiment, a portion 72 of the protective film 70 is more deeply embedded in the peripheral groove 61, and the bottom of the portion 72 of the protective film 70 is in contact with the insulating film 63 covering the sidewall portion S2. Therefore, peeling of the protective film 70 can be prevented more effectively. Furthermore, the portion 72 of the protective film 70 has a shape with a large diameter at the bottom of the peripheral groove 61 and a small diameter at the entrance portion, so a so-called anchoring effect can also be expected. In addition, as described above, the sidewall portion S2 is a flat surface, so the boundary between the protective film 70 and the metal member 41, i.e., the end of the metal member 41, terminates on a flat surface. Thus, compared with the case where the metal member 41 terminates on a surface with a curved shape such as a corner C, the electric field applied to the drift layer 30 can be mitigated near the end of the metal member 41.

[0074] <Fifth Implementation>

[0075] Figure 13is a schematic cross-sectional view showing the structure of a Schottky barrier diode 15 of a fifth embodiment of the present application.

[0076] As shown in Figure 13 , the Schottky barrier diode 15 of the fifth embodiment differs from the Schottky barrier diode 12 of the second embodiment in that a portion 72 of the protective film 70 embedded in the outer peripheral trench 61 does not contact the insulating film 63. The other basic structure is the same as that of the Schottky barrier diode 12 of the second embodiment, and therefore the same reference numerals are assigned to the same elements, and the repeated explanation is omitted.

[0077] As exemplified in the present embodiment, in the present application, the portion 72 of the protective film 70 embedded in the outer peripheral trench 61 does not necessarily need to contact the insulating film 63.

[0078] Figure 14 is a schematic cross-sectional view showing the structure of a Schottky barrier diode 15A of a modification of the fifth embodiment.

[0079] As shown in Figure 14 , the Schottky barrier diode 15A of the modification of the fifth embodiment differs from the Schottky barrier diode 15 of the fifth embodiment in that the outer peripheral portion of the anode electrode 40 is located on the drift layer 30, and the field insulating film 80 is interposed therebetween. The other basic structure is the same as that of the Schottky barrier diode 15 of the fifth embodiment, and therefore the same reference numerals are assigned to the same elements, and the repeated explanation is omitted.

[0080] As exemplified in the present modification, in the case where the outer peripheral portion of the anode electrode 40 overlaps the drift layer 30, the concentration of the electric field can be moderated by interposing the field insulating film 80 therebetween. As the material of the field insulating film 80, SiO2or the like can be used.

[0081] < Sixth Embodiment >

[0082] Figure 15 is a schematic cross-sectional view showing the structure of a Schottky barrier diode 16 of a sixth embodiment of the present application.

[0083] As shown in Figure 15 , the Schottky barrier diode 16 of the sixth embodiment differs from the Schottky barrier diode 11 of the first embodiment in that the bottom surface portion B of the outer peripheral trench 61 is not flat, but is curved as a whole. The other basic structure is the same as that of the Schottky barrier diode 11 of the first embodiment, and therefore the same reference numerals are assigned to the same elements, and the repeated explanation is omitted.

[0084] Even when the bottom part B of the outer peripheral groove 61 is curved, as long as a portion 72 of the protective film 70 embedded in the outer peripheral groove 61 and the boundary of the metal part 41 are located in the flat sidewall portion S1, the electric field applied to the drift layer 30 can be mitigated near the end of the metal part 41, just like the Schottky barrier diode 11 of the first embodiment.

[0085] <Seventh Implementation>

[0086] Figure 16 This is a schematic cross-sectional view showing the structure of the Schottky barrier diode 17 according to the seventh embodiment of the present invention.

[0087] like Figure 16 As shown, the Schottky barrier diode 17 of the seventh embodiment differs from the Schottky barrier diode 16 of the sixth embodiment in that a portion 72 of the protective film 70 embedded in the peripheral trench 61 and the boundary of the metal component 41 are located on the inner sidewall portion S2. Other basic structures are the same as those of the Schottky barrier diode 16 of the sixth embodiment; therefore, the same symbols are used for the same elements, and repeated descriptions are omitted.

[0088] Even when the bottom part B of the outer peripheral groove 61 is curved, as long as a portion 72 of the protective film 70 embedded in the outer peripheral groove 61 and the boundary of the metal part 41 are located in the flat sidewall portion S2, the electric field applied to the drift layer 30 can be mitigated near the end of the metal part 41, just like the Schottky barrier diode 11 of the first embodiment.

[0089] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. These modifications are of course also included within the scope of the present invention.

[0090] Example

[0091] <Example 1>

[0092] Imagine having with Figure 10 The simulation model of Embodiment 1, which has the same structure as the Schottky barrier diode 12 shown, simulates the electric field strength when a reverse voltage of 800V is applied between the anode electrode 40 and the cathode electrode 50. The doping concentration of the semiconductor substrate 20 is 1×10⁻⁶. 18 cm -3 The dopant concentration of the drift layer 30 is 2 × 10⁻⁶. 16 cm -3The drift layer 30 has a thickness of 7 μm. Furthermore, the peripheral trench 61 has a width W1 of 10 μm, the central trench 62 has a width of 2 μm, and both have a depth of 3 μm. Additionally, the width of the drift layer 30 in contact with the anode electrode 40, i.e., the width of the mesa region M, is 2 μm. The insulating film 63 is a 50 nm thick HfO2 film. Furthermore, the protective film 70 is made of SiN.

[0093] Then, the electric field intensity applied to corner C was simulated while the depth position x of the boundary between a portion 72 of the protective film 70 and the metal part 41 varied from 0 to 3 μm. For example... Figure 10 As shown, depth position x represents the boundary position between a portion 72 of the protective film 70 and the metal component 41, with the bottom of the peripheral groove 61 as a reference. The simulation results are shown in... Figure 17 middle.

[0094] like Figure 17 As shown, if the depth position x is 0.9 μm or more, the electric field strength applied to the corner C is significantly lower than the 8 MV / cm electric field strength that breaks the insulation of gallium oxide. However, when the depth position x is 3.0 μm, that is, when the protective film 70 is not fully embedded in the peripheral trench 61, the effect of improved adhesion is not obtained, and peeling is prone to occur. On the other hand, when the depth position x is 0.6 μm or less, the electric field strength applied to the corner C becomes 8 MV / cm or more. This is believed to be because, when the depth position x is too small, the boundary between a portion 72 of the protective film 70 and the metal part 41 is located on the curved surface constituting the corner C.

[0095] <Example 2>

[0096] Imagine having with Figure 11 The simulation model of Embodiment 2, which has the same structure as the Schottky barrier diode 13 shown, simulates the electric field strength when an 800V reverse voltage is applied between the anode electrode 40 and the cathode electrode 50. The simulation model of Embodiment 2 has the same parameters as Embodiment 1, except that the boundary between a portion 72 of the protective film 70 and the metal part 41 is located at the bottom part B.

[0097] Then, the electric field intensity applied to corner C was simulated while the planar position x of the boundary between a portion 72 of the protective film 70 and the metal component 41 varied from 0 to 10 μm. For example... Figure 11 As shown, the planar position x represents the boundary position between a portion 72 of the protective film 70 and the metal component 41, with the sidewall portion S2 of the outer peripheral groove 61 as a reference. The simulation results are shown in... Figure 18 middle.

[0098] like Figure 18As shown, if the planar position x is in the range of 0.5 to 9.5 μm, the electric field strength applied to the corner C is significantly lower than the 8 MV / cm, which is the dielectric breaking electric field strength of gallium oxide. On the other hand, when the planar position x is close to 0 μm or 10 μm, the electric field strength applied to the corner C becomes 8 MV / cm or more. This is believed to be because, when the planar position x is too small or too large, the boundary between a portion 72 of the protective film 70 and the metal component 41 is located on the curved surface constituting the corner C.

[0099] <Example 3>

[0100] Imagine having with Figure 12 The simulation model of Embodiment 3, which has the same structure as the Schottky barrier diode 14 shown, simulates the electric field strength when an 800V reverse voltage is applied between the anode electrode 40 and the cathode electrode 50. The simulation model of Embodiment 3 has the same parameters as Embodiment 1, except that a portion 72 of the protective film 70 and the sidewall portion S2 where the boundary between the metal part 41 and the protective film 70 is located on the inner side.

[0101] Then, the electric field intensity applied to corner C was simulated while the depth position x of the boundary between a portion 72 of the protective film 70 and the metal part 41 varied from 0 to 3 μm. For example... Figure 12 As shown, depth position x represents the boundary position between a portion 72 of the protective film 70 and the metal component 41, with the bottom of the outer peripheral groove 61 as a reference. The simulation results are shown in... Figure 19 middle.

[0102] like Figure 19 As shown, if the depth position x is 0.2 μm or more, the electric field strength applied to the corner C is significantly lower than the 8 MV / cm electric field strength that constitutes the insulation breakdown field of gallium oxide. On the other hand, when the depth position x is close to 0 μm, the electric field strength applied to the corner C becomes 8 MV / cm or more. This is believed to be because, when the depth position x is too small, a portion 72 of the protective film 70 and the boundary between it and the metal component 41 are located on the curved surface constituting the corner C.

[0103] Explanation of symbols

[0104] 11-17, 15A Schottky barrier diodes

[0105] 20 Semiconductor substrates

[0106] 21. Top surface of semiconductor substrate

[0107] 22. Back side of semiconductor substrate

[0108] 30 Drift Layers

[0109] 31. Upper surface of the drift layer

[0110] 40 anode electrode

[0111] 41 metal part

[0112] 42 void

[0113] 50 cathode electrode

[0114] 61 outer peripheral groove

[0115] 62 center groove

[0116] 63 insulating film

[0117] 70 protective film

[0118] 71 opening portion

[0119] 72 portion of the protective film

[0120] 80 field insulating film

[0121] B bottom surface portion

[0122] C corner portion

[0123] E0 to E2 edge

[0124] M table region

[0125] R resist

[0126] S1, S2 side wall portion

Claims

1. A Schottky barrier diode characterized by comprising: a semiconductor substrate composed of gallium oxide; a drift layer composed of gallium oxide provided on the semiconductor substrate; an anode electrode in Schottky contact with the drift layer; a cathode electrode in ohmic contact with the semiconductor substrate; an insulating film covering the entirety of inner walls of a trench provided in the drift layer; and a protective film covering the anode electrode, the trench being located at the outer periphery of a Schottky contact region of the anode electrode, only the insulating film, a portion of the protective film, and a metal member electrically connected to the anode electrode being embedded in the trench, the metal member and the protective film having a boundary shape along the inner walls of the trench, the boundary of the protective film and the metal member being in contact with the insulating film, and the metal member being formed on the drift layer via only the insulating film.

2. The Schottky barrier diode according to claim 1, characterized in that the trench is formed in a ring shape.

3. The Schottky barrier diode according to claim 2, characterized in that the trench has a flat sidewall portion, and the boundary of the protective film and the metal member is located at the sidewall portion.

4. The Schottky barrier diode according to claim 2, characterized in that the trench has a flat bottom surface portion, and the boundary of the protective film and the metal member is located at the bottom surface portion. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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