Schottky barrier diode

Abstract

The technical problem of the present invention is to prevent insulation breakdown caused by charge accumulation in a Schottky barrier diode. This Schottky barrier diode (1) is provided with: a semiconductor substrate (20); a drift layer (30); a field insulating film (80) that covers an outer peripheral region (31B) in the upper surface (31) of the drift layer (30); an anode electrode (40) that is in Schottky contact with a central region (31A) in the upper surface (31) of the drift layer (30) and has an end positioned on the field insulating film (80); and a conductive member (90) in contact with the field insulating film (80) and electrically connected to the semiconductor substrate (20). Consequently, when a reverse voltage is applied, the charge accumulated in the drift layer (30) is relaxed, and thus it is possible to prevent insulation breakdown caused by the accumulation of the charge.

Description

Technical Field

[0001] The present invention relates to a Schottky barrier diode. Background Art

[0002] Schottky barrier diodes are rectifying elements that utilize the Schottky barrier formed by the junction of metal and semiconductor. Compared to conventional diodes with PN junctions, they have lower forward voltages and faster switching speeds. Therefore, Schottky barrier diodes are sometimes used as switching elements in power devices.

[0003] When Schottky barrier diodes are used as switching elements in power devices, sufficient reverse breakdown voltage must be ensured. Therefore, materials with larger band gaps, such as silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga2O3), are sometimes used in place of silicon (Si). Gallium oxide has a very large band gap of 4.8 to 4.9 eV and a high dielectric breakdown field of approximately 8 MV / cm. Therefore, Schottky barrier diodes using gallium oxide hold great promise as switching elements for power devices. Patent Document 1 describes an example of a Schottky barrier diode using gallium oxide.

[0004] Patent Document 1 discloses a structure in which a field insulating film is provided on the upper surface of the drift layer and the end of the anode electrode is arranged on the field insulating film. By configuring the anode electrode in this manner as a field plate structure, the electric field applied to the drift layer when a reverse voltage is applied is relaxed.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-142577 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, in the Schottky barrier diode described in Patent Document 1, when a reverse voltage is applied, charges are accumulated in the drift layer, and dielectric breakdown may occur in a portion located directly below the field insulating film.

[0010] In the present invention, a technique for preventing dielectric breakdown caused by charge accumulation in a Schottky barrier diode will be described.

[0011] Technical solutions to solve problems

[0012] A Schottky barrier diode according to one aspect of the present invention comprises: a semiconductor substrate; a drift layer provided on the semiconductor substrate; a field insulating film covering an annular outer peripheral region on the upper surface of the drift layer; an anode electrode in Schottky contact with a central region of the upper surface of the drift layer surrounded by the outer peripheral region, with an end portion located on the field insulating film; a cathode electrode in ohmic contact with the semiconductor substrate; a first conductive member embedded in a first trench provided in the central region of the drift layer via the insulating film and connected to the anode electrode; and a second conductive member in contact with the field insulating film and electrically connected to the semiconductor substrate.

[0013] Effects of the Invention

[0014] According to the present disclosure, a technology for preventing dielectric breakdown caused by charge accumulation in a Schottky barrier diode is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] [ Figure 1 ] Figure 1 (a) is a schematic plan view showing the structure of the Schottky barrier diode 1 according to the first embodiment of the technology involved in the present disclosure. Figure 1 (b) is along Figure 1 A simplified cross-sectional view taken along line AA shown in (a).

[0016] [ Figure 2 ] Figure 2 This is a schematic cross-sectional view showing the structure of a Schottky barrier diode 2 according to a second embodiment of the technology according to the present disclosure.

[0017] [ Figure 3 ] Figure 3 This is a schematic cross-sectional view showing the structure of a Schottky barrier diode 3 according to a third embodiment of the technology according to the present disclosure.

[0018] [ Figure 4 ] Figure 4 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 4 according to a fourth embodiment of the technology according to the present disclosure.

[0019] [ Figure 5 ] Figure 5 (a) is a schematic plan view showing the structure of a Schottky barrier diode 5 according to a fifth embodiment of the technology of the present disclosure. Figure 5 (b) is along Figure 5 A simplified cross-sectional view taken along line AA shown in (a).

[0020] [ Figure 6 ] Figure 6 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 6 according to a sixth embodiment of the technology according to the present disclosure.

[0021] [ Figure 7 ] Figure 7 This is a schematic cross-sectional view showing the structure of a Schottky barrier diode 7 according to a seventh embodiment of the technology according to the present disclosure.

[0022] [ Figure 8 ] Figure 8 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 8 according to an eighth embodiment of the technology according to the present disclosure.

[0023] [ Figure 9 ] Figure 9 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 9 according to a ninth embodiment of the technology according to the present disclosure.

[0024] [ Figure 10 ] Figure 10 It is a schematic plan view showing the structure of a Schottky barrier diode 10 according to a tenth embodiment of the technology according to the present disclosure.

[0025] [ Figure 11 ] Figure 11 It is a schematic plan view showing the structure of a Schottky barrier diode 11 according to an eleventh embodiment of the technology according to the present disclosure.

[0026] [ Figure 12 ] Figure 12 It is a schematic plan view showing the structure of a Schottky barrier diode 12 according to a twelfth embodiment of the technology according to the present disclosure.

[0027] [ Figure 13 ] Figure 13 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 13 of a comparative example.

[0028] [ Figure 14 ] Figure 14 (a) is a schematic top view showing the wafer 100 before dicing. Figure 14 (b) is along Figure 14 A simplified cross-sectional view taken along line AA shown in (a).

[0029] [ Figure 15 ] Figure 15 1 is a schematic plan view of a wafer 100 showing a modified example.

[0030] [ Figure 16 ] is a graph showing the results of Example 1.

[0031] [ Figure 17 ] is a graph showing the results of Example 2. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the technology according to the present disclosure will be described in detail with reference to the accompanying drawings.

[0033] <First embodiment>

[0034] Figure 1 (a) is a schematic plan view showing the structure of the Schottky barrier diode 1 according to the first embodiment of the technology involved in the present disclosure. Figure 1 (b) is along Figure 1 A simplified cross-sectional view taken along line AA shown in (a).

[0035] like Figure 1 As shown, the Schottky barrier diode 1 of the first embodiment includes a semiconductor substrate 20 and a drift layer 30, both of which are made of gallium oxide (β-Ga2O3). Silicon (Si) or tin (Sn) is introduced into the semiconductor substrate 20 and the drift layer 30 as an n-type dopant. The concentration of the dopant is higher in the semiconductor substrate 20 than in the drift layer 30, thereby making the semiconductor substrate 20 an n-type dopant. + layer, the drift layer 30 serves as n - Layers play a role.

[0036] The semiconductor substrate 20 is cut from a bulk crystal formed using a melt growth method or other methods, and has a thickness of approximately 250 μm. The planar dimensions of the semiconductor substrate 20 are not particularly limited and are generally selected based on the current flowing through the device. For a maximum forward current of approximately 20 A, a planar dimension of approximately 2.4 mm × 2.4 mm is sufficient.

[0037] The semiconductor substrate 20 has an upper surface 21, located on the upper side during mounting, and a rear surface 22, located opposite the upper surface 21 and located on the lower side during mounting. A drift layer 30 is formed entirely on the upper surface 21. The drift layer 30 is a thin film formed by epitaxially growing gallium oxide on the upper surface 21 of the semiconductor substrate 20 using reactive sputtering, PLD, MBE, MOCVD, HVPE, or other methods. The thickness of the drift layer 30 is not particularly limited and is generally selected based on the reverse withstand voltage of the device. To ensure a withstand voltage of approximately 600V, a thickness of approximately 10 μm is sufficient, for example.

[0038] The upper surface 31 of the drift layer 30 has an annular outer peripheral region 31B and a central region 31A surrounded by the outer peripheral region 31B. The outer peripheral region 31B of the upper surface 31 of the drift layer 30 is covered by a field insulating film 80 made of silicon oxide or the like. Furthermore, an anode electrode 40 is formed in the central region 31A of the upper surface 31 of the drift layer 30, forming a Schottky contact with the drift layer 30. The outer peripheral end of the anode electrode 40 is located on the field insulating film 80. This field plate structure can mitigate the electric field applied to the drift layer 30.

[0039] The anode electrode 40 is composed of a metal such as platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), molybdenum (Mo), or copper (Cu). It can have a multilayer structure consisting of a stack of different metal films, such as Pt / Au, Pt / Al, Pd / Au, Pd / Al, Pt / Ti / Au, or Pd / Ti / Au. Meanwhile, a cathode electrode 50 is provided on the back surface 22 of the semiconductor substrate 20, making ohmic contact with the semiconductor substrate 20. The cathode electrode 50 is composed of a metal such as titanium (Ti). It can have a multilayer structure consisting of a stack of different metal films, such as Ti / Au or Ti / Al.

[0040] In this embodiment, a central trench 61 and a peripheral trench 62 are provided in the drift layer 30. Both the central trench 61 and the peripheral trench 62 are provided in the central region 31A, i.e., at a position overlapping the anode electrode 40 in a plan view. A conductive member 41 is embedded within the central region 31A via an insulating film 70. The conductive member 41 may be made of the same material as the anode electrode 40 or a different conductive material. In other words, the conductive member 41 and the anode electrode 40 may be electrically connected.

[0041] The central groove 61 is clamped by a portion of the drift layer 30, namely the mesa region M. The peripheral groove 62 is annularly surrounding the mesa region M and the central groove 61. The central groove 61 and the peripheral groove 62 do not need to be completely separated, and the central groove 61 and the peripheral groove 62 can also be connected. The depths of the central groove 61 and the peripheral groove 62 can be the same or different. The mesa region M is a portion of the drift layer 30 divided by the central groove 61 and the peripheral groove 62, and becomes a depletion layer when a reverse voltage is applied between the anode electrode 40 and the cathode electrode 50. As a result, the channel region of the drift layer 30 is pinched off, and the leakage current when a reverse voltage is applied is greatly suppressed.

[0042] Furthermore, the drift layer 30 is provided with a groove 63 which is provided in a ring shape so as to surround the anode electrode 40 when viewed from above in the stacking direction. The groove 63 reaches the semiconductor substrate 20, and thus the semiconductor substrate 20 is exposed at the bottom surface of the groove 63. Figure 1 In the example shown, the upper surface 21 of the semiconductor substrate 20 is exposed at the bottom of the trench 63. The inner and outer peripheral walls of the trench 63 have a substantially rectangular shape with curved corners when viewed from above in the stacking direction. Figure 1 In the example shown, a portion of the outer peripheral wall of the groove 63 is exposed to the outside.

[0043] A conductive member 90 is embedded in the trench 63. The material of the conductive member 90 is not particularly limited and may be composed of a metal material such as Al, Au, Ni, Cu, Pt, or Ti, or a semiconductor material such as polysilicon. At least a portion of the conductive member 90 may also be composed of the same metal material as the anode electrode 40 or the conductive member 41. If at least a portion of the conductive member 90 is composed of the same metal material as the anode electrode 40 or the conductive member 41, at least a portion of the conductive member 90 can be formed simultaneously with the anode electrode 40 or the conductive member 41.

[0044] The conductive member 90 embedded in the trench 63 is exposed from the field insulating film 80, with a portion thereof located on the field insulating film 80. Thus, the conductive member 90 is in contact with the field insulating film 80 and with the outer peripheral region 31B of the upper surface 31 of the drift layer 30 covered by the field insulating film 80. The distance T between the conductive member 90 and the anode electrode 40 on the field insulating film 80 is not particularly limited, but by setting it to 100 μm or greater, the lateral expansion of the depletion layer is suppressed, thereby achieving a higher withstand voltage. Furthermore, because the trench 63 reaches the semiconductor substrate 20, the conductive member 90 is electrically connected to the semiconductor substrate 20. Consequently, when a reverse voltage is applied, charge accumulated in the field insulating film 80 flows to the semiconductor substrate 20 via the conductive member 90. Specifically, when a reverse voltage is applied, positive charge accumulates near the upper surface 31 of the drift layer 30, inducing negative charge in the field insulating film 80, which is composed of a dielectric material. The negative charges induced in the field insulating film 80 are drawn to the semiconductor substrate 20 via the conductive member 90 in contact with the field insulating film 80 , and as a result, the electric field applied to the drift layer 30 is relaxed.

[0045] Thus, in the Schottky barrier diode 1 of this embodiment, the trench 63 reaching the semiconductor substrate 20 is provided in the drift layer 30, and the conductive member 90 embedded in the trench 63 is in contact with the field insulating film 80. Therefore, when a reverse voltage is applied, the induced charge is drawn to the semiconductor substrate 20. Figure 13 Compared to the case where the trench 63 and the conductive member 90 are not provided, as in the comparative example shown in the figure, the withstand voltage under reverse voltage can be improved. Furthermore, in this embodiment, since the trench 63 is provided in a ring shape, charge can be efficiently pumped to the semiconductor substrate 20. Furthermore, since the conductive member 90 embedded in the trench 63 is exposed from the side of the drift layer 30, heat dissipation characteristics are also improved.

[0046] In addition, since the groove 63 is provided in an annular shape, Figure 14 As in the wafer 100 shown in FIG. 1 ( a ), in the state before dicing, the anode electrode 40 included in each Schottky barrier diode 1 and the drift layer 30 located directly thereunder are respectively surrounded by the conductive member 90 . Figure 14(b) is along Figure 14 Therefore, it is possible to accurately perform the characteristic test of each Schottky barrier diode without being affected by other Schottky barrier diodes on the same wafer. It is not necessary to set the trench 63 and the conductive member 90 buried therein for each Schottky barrier diode 1. Figure 15 As shown, the grooves 63 and the conductive members 90 embedded therein are formed in a grid shape.

[0047] <Second embodiment>

[0048] Figure 2 This is a schematic cross-sectional view showing the structure of a Schottky barrier diode 2 according to a second embodiment of the technology according to the present disclosure.

[0049] like Figure 2 As shown, the Schottky barrier diode 2 of the second embodiment differs from the Schottky barrier diode 1 of the first embodiment in that the outer periphery of the anode electrode 40 and the exposed portions of the field insulating film 80 and the conductive member 90 are covered with a protective film 81 made of an insulating material. The rest of the basic structure is the same as that of the Schottky barrier diode 1 of the first embodiment, so identical elements are denoted by the same reference numerals, and repeated descriptions are omitted. The provision of such a protective film 81 can further improve product reliability.

[0050] <Third embodiment>

[0051] Figure 3 This is a schematic cross-sectional view showing the structure of a Schottky barrier diode 3 according to a third embodiment of the technology according to the present disclosure.

[0052] like Figure 3 As shown, in the Schottky barrier diode 3 of the third embodiment, the conductive member 90 includes a portion 91 located at the bottom of the trench 63 and a portion 92 located above the trench 63, each made of different metal materials. The rest of the basic structure is the same as that of the Schottky barrier diode 1 of the first embodiment, so identical elements are denoted by the same reference numerals, and duplicate descriptions are omitted. Using multiple metal materials to construct the conductive member 90 in this manner can sometimes reduce manufacturing costs. For example, the portion 91 located at the bottom of the trench 63 can be formed by electroplating, while the portion 92 located above the trench 63 can be formed simultaneously with the anode electrode 40 or the conductive member 41 by vapor deposition.

[0053] <Fourth embodiment>

[0054] Figure 4 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 4 according to a fourth embodiment of the technology according to the present disclosure.

[0055] like Figure 4 As shown, the Schottky barrier diode 4 of the fourth embodiment differs from the Schottky barrier diode 1 of the first embodiment in that the trench 63 is formed deeper. The rest of the basic structure is the same as that of the Schottky barrier diode 1 of the first embodiment, so identical elements are denoted by identical reference numerals, and duplicate descriptions are omitted. Thus, by forming the trench 63 deeper beyond the interface between the semiconductor substrate 20 and the drift layer 30, even if the trench 63 becomes shallower than designed due to manufacturing variations, the conductive member 90 can reliably contact the semiconductor substrate 20.

[0056] <Fifth embodiment>

[0057] Figure 5 (a) is a schematic plan view showing the structure of a Schottky barrier diode 5 according to a fifth embodiment of the technology of the present disclosure. Figure 5 (b) is along Figure 5 A simplified cross-sectional view taken along line AA shown in (a).

[0058] like Figure 5 As shown, in the Schottky barrier diode 5 of the fifth embodiment, the outer peripheral wall of the trench 63 is not exposed to the outside, and the drift layer 30 is also present outside the outer peripheral wall of the trench 63. In addition, the upper surface 31 of the drift layer 30 has an outermost peripheral region 31C located outside the outer peripheral region 31B, and the outermost peripheral region 31C is covered by a field insulating film 80. The rest of the basic structure is the same as that of the Schottky barrier diode 1 of the first embodiment. Therefore, the same reference numerals are used to designate the same elements, and repeated descriptions are omitted. In this way, a structure in which the drift layer 30 is also present outside the outer peripheral wall of the trench 63 is also possible.

[0059] <Sixth embodiment>

[0060] Figure 6 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 6 according to a sixth embodiment of the technology according to the present disclosure.

[0061] like Figure 6 As shown, the Schottky barrier diode 6 of the sixth embodiment differs from the Schottky barrier diode 5 of the fifth embodiment in that the outer periphery of the anode electrode 40 and the exposed portions of the field insulating film 80 and the conductive member 90 are covered with a protective film 81 made of an insulating material. The rest of the basic structure is the same as that of the Schottky barrier diode 5 of the fifth embodiment, so like elements are denoted by like reference numerals, and duplicate descriptions are omitted. The provision of such a protective film 81 can further improve product reliability.

[0062] <Seventh embodiment>

[0063] Figure 7 This is a schematic cross-sectional view showing the structure of a Schottky barrier diode 7 according to a seventh embodiment of the technology according to the present disclosure.

[0064] like Figure 7 As shown in FIG. 1 , the Schottky barrier diode 7 of the seventh embodiment differs from the Schottky barrier diode 5 of the fifth embodiment in that the outermost region 31C is not covered by the field insulating film 80. The rest of the basic structure is the same as that of the Schottky barrier diode 5 of the fifth embodiment, so the same reference numerals are used to designate the same elements, and duplicate descriptions are omitted. Thus, the outermost region 31C does not need to be covered by the field insulating film 80.

[0065] <Eighth Embodiment>

[0066] Figure 8 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 8 according to an eighth embodiment of the technology according to the present disclosure.

[0067] like Figure 8 As shown, the Schottky barrier diode 8 of the eighth embodiment differs from the Schottky barrier diode 7 of the seventh embodiment in that the outer periphery of the anode electrode 40, the exposed portions of the field insulating film 80 and the conductive member 90, and the outermost peripheral region 31C are covered with a protective film 81 made of an insulating material. The rest of the basic structure is the same as that of the Schottky barrier diode 7 of the seventh embodiment, so the same reference numerals are used to identify the same elements, and repeated descriptions are omitted. The provision of such a protective film 81 can further improve product reliability.

[0068] <Ninth embodiment>

[0069] Figure 9 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 9 according to a ninth embodiment of the technology according to the present disclosure.

[0070] like Figure 9 As shown, the Schottky barrier diode 9 of the ninth embodiment differs from the Schottky barrier diode 8 of the eighth embodiment in that a portion of the protective film 81 is embedded in the trench 63. The rest of the basic structure is the same as that of the Schottky barrier diode 8 of the eighth embodiment, so like elements are denoted by like reference numerals, and duplicate descriptions are omitted. Thus, a member other than the conductive member 90, such as the protective film 81, may be embedded in a portion of the trench 63.

[0071] <Tenth embodiment>

[0072] Figure 10 It is a schematic plan view showing the structure of a Schottky barrier diode 10 according to a tenth embodiment of the technology according to the present disclosure.

[0073] like Figure 10 As shown, the Schottky barrier diode 10 of the tenth embodiment differs from the Schottky barrier diode 1 of the first embodiment in that, when viewed from above in the stacking direction, the outer peripheral wall of the trench 63 is rectangular, while the corners of the inner peripheral wall of the trench 63 are curved. The rest of the basic structure is the same as that of the Schottky barrier diode 1 of the first embodiment, so the same reference numerals are used to identify the same elements, and repeated descriptions are omitted. Thus, the outer and inner peripheral walls of the trench 63 may have different planar shapes when viewed from above in the stacking direction.

[0074] <Eleventh Embodiment>

[0075] Figure 11 It is a schematic plan view showing the structure of a Schottky barrier diode 11 according to an eleventh embodiment of the technology according to the present disclosure.

[0076] like Figure 11 As shown, the Schottky barrier diode 11 of the eleventh embodiment differs from the Schottky barrier diode 1 of the first embodiment in that, when viewed from above in the stacking direction, the outer and inner walls of the trench 63 are both rectangular, with no corners curved. The rest of the basic structure is the same as that of the Schottky barrier diode 1 of the first embodiment, so like elements are denoted by like reference numerals, and duplicate descriptions are omitted. Thus, the corners of the trench 63, viewed from the stacking direction, do not need to be curved.

[0077] <Twelfth embodiment>

[0078] Figure 12 It is a schematic plan view showing the structure of a Schottky barrier diode 12 according to a twelfth embodiment of the technology according to the present disclosure.

[0079] like Figure 12 As shown, the Schottky barrier diode 12 of the twelfth embodiment differs from the Schottky barrier diode 1 of the first embodiment in that, when viewed from above in the stacking direction, the trench 63 is not annular but is instead provided in two localized locations. The rest of the basic structure is the same as that of the Schottky barrier diode 1 of the first embodiment, so identical elements are denoted by the same reference numerals, and repeated descriptions are omitted. Thus, the trench 63 need not be annular in plan view and can be provided at any location within the peripheral region 31B.

[0080] While embodiments of the technology of the present disclosure have been described above, the technology of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the invention, which are naturally also included in the scope of the technology of the present disclosure.

[0081] For example, in the aforementioned embodiments, gallium oxide is used as the material for the semiconductor substrate 20 and the drift layer 30. However, the materials for the semiconductor substrate 20 and the drift layer 30 are not limited to gallium oxide. Materials such as silicon carbide (SiC), gallium nitride (GaN), aluminum nitride (AlN), diamond (C), silicon (Si), germanium (Ge), silicon germanium (SiGe), and gallium arsenide (GaAs) may also be used. When these materials are used as the materials for the semiconductor substrate 20 and the drift layer 30, the same effects as when gallium oxide is used can be achieved based on the same principles.

[0082] Furthermore, in each of the above-described embodiments, the drift layer 30 is provided with the central trench 61 and the peripheral trench 62 . However, one of the central trench 61 and the peripheral trench 62 may be omitted.

[0083] The technology according to the present disclosure includes, but is not limited to, the following structural examples.

[0084] A Schottky barrier diode according to one aspect of the present disclosure includes: a semiconductor substrate; a drift layer disposed on the semiconductor substrate; a field insulating film covering an annular outer peripheral region on the upper surface of the drift layer; an anode electrode in Schottky contact with a central region of the upper surface of the drift layer surrounded by the outer peripheral region, with its end located on the field insulating film; a cathode electrode in ohmic contact with the semiconductor substrate; a first conductive member embedded in a first trench disposed in the central region of the drift layer via the insulating film and connected to the anode electrode; and a second conductive member in contact with the field insulating film and electrically connected to the semiconductor substrate. This arrangement reduces charge accumulated in the drift layer when a reverse voltage is applied, thereby preventing dielectric breakdown caused by charge accumulation.

[0085] In the Schottky barrier diode, a portion of the second conductive member may be located on the field insulating film. This allows for more efficient charge extraction.

[0086] In the above-mentioned Schottky barrier diode, the drift layer may further include a second trench reaching the semiconductor substrate, and the second conductive member may be embedded in the second trench.

[0087] In the above-described Schottky barrier diode, the second trench may be provided in a ring shape so as to surround the anode electrode in a plan view as seen from the stacking direction.

[0088] In the above-described Schottky barrier diode, the second conductive member may have a portion located at the bottom of the second trench and a portion located above the second trench made of different metal materials. This facilitates formation of the second conductive member.

[0089] In the above-described Schottky barrier diode, at least a portion of the second conductive member may be formed of the same metal material as the anode electrode or the first conductive member. This facilitates formation of the second conductive member.

[0090] Example

[0091] <Example 1>

[0092] Imagine having Figure 1 and Figure 13 The two simulation models of Schottky barrier diodes 1 and 13 with the same structure are shown. The simulation is about the amount of space charge accumulated in the drift layer 30 directly below the field insulating film 80 when a reverse voltage of 1200 V is applied between the anode electrode 40 and the cathode electrode 50. The dopant concentration of the semiconductor substrate 20 is set to 1×10 18 cm -3 , the dopant concentration of the drift layer 30 is set to 1×10 16 cm -3 The thickness of the drift layer 30 was set to 10 μm. In addition, the depths of the central trench 61 and the peripheral trench 62 were both set to 2 μm. Figure 1 The widths of the central trench 61 and the peripheral trench 62 in the cross section shown in (b), as well as the width of the upper surface 31 of the drift layer 30 (the width of the mesa region M), are all set to 1.0 μm. The material of the anode electrode 40 is Ni, and the material of the cathode electrode 50 is a stacked film of Ti and Au. The insulating film 70 is HfO2 with a thickness of 50 nm, and the field insulating film 80 is SiO2 with a thickness of 300 nm. The trench 63 is provided at a position 14 μm from the outer peripheral wall of the peripheral trench 62, and its width is 50 μm and its depth is 10 μm. The material of the conductive member 90 embedded in the trench 63 is the same as that of the anode electrode 40. The distance T between the conductive member 90 and the anode electrode 40 is 8 μm.

[0093] The simulation results are shown in Figure 16 .exist Figure 16 In the figure, the horizontal axis is the distance X based on the outer peripheral wall of the peripheral groove 62 (refer to Figure 1 ). In addition, the solid line represents the characteristics of the Schottky barrier diode 1, and the dotted line represents the characteristics of the Schottky barrier diode 13.

[0094] like Figure 16 As shown, in the Schottky barrier diode 1 having the conductive member 90, the space charge amount in the region about 8 μm away from the outer peripheral wall of the outer peripheral trench 62 is 1×10 16 cm -2Although the space charge decreases as the area moves outward, the space charge increases again as the area approaches the conductive member 90. Near the conductive member 90, the space charge is 4.5×10 15 cm -2 It can be seen from this that the electric charge is extracted by the conductive member 90 .

[0095] On the other hand, in the Schottky barrier diode 13 without the conductive member 90, in the region about 8 μm away from the outer peripheral wall of the outer peripheral trench 62, although the space charge amount is 1×10 16 cm -2 However, the amount of space charge decreases significantly as it moves from this area toward the outside. In the area about 12 μm away from the outer wall of the peripheral groove 62, the amount of space charge decreases to 1×10 8 cm -2 As described above, it can be seen that in the Schottky barrier diode 13 that does not have the conductive member 90 , the charges have no space for discharge and are accumulated.

[0096] The electric field intensity applied to the field insulating film 80 was 11.9 MV / cm in the Schottky barrier diode 1 and 12.1 MV / cm in the Schottky barrier diode 13 .

[0097] <Example 2>

[0098] Imagine having Figure 1 A simulation model having the same structure as the Schottky barrier diode 1 shown was used to simulate the amount of space charge accumulated in the drift layer 30 directly below the field insulating film 80 when the distance T between the conductive member 90 and the anode electrode 40 was set to 8 μm, 50 μm, 100 μm, 150 μm, or 200 μm. Other conditions were the same as those in Example 1.

[0099] The simulation results are shown in Figure 17 .like Figure 17 As shown, it can be seen that the charge distribution does not change with the distance T, and a high amount of space charge is maintained except near the edge of the conductive member 90 .

[0100] Description of Reference Signs

[0101] 1~13 Schottky barrier diodes

[0102] 20 semiconductor substrate

[0103] 21 Upper surface of semiconductor substrate

[0104] 22 Back side of semiconductor substrate

[0105] 30 Drift Layer

[0106] 31 Upper surface of the drift layer

[0107] 31A Central Area

[0108] 31B Peripheral Area

[0109] 31C outermost area

[0110] 40 Anode electrode

[0111] 41 Conductive components

[0112] 50 cathode electrode

[0113] 61 center groove

[0114] 62 peripheral groove

[0115] 63 Grooves

[0116] 70 Insulation film

[0117] 80 Field insulating film

[0118] 81 protective film

[0119] 90 conductive components

[0120] 91 bottom of the trench

[0121] 92 Upper part of the groove

[0122] 100 wafers

[0123] M countertop area.

Claims

1. A Schottky barrier diode, wherein: have: semiconductor substrates; a drift layer disposed on the semiconductor substrate; a field insulating film covering a ring-shaped outer peripheral region of the upper surface of the drift layer; an anode electrode in Schottky contact with a central region of the upper surface of the drift layer surrounded by the peripheral region, and having an end portion located on the field insulating film; a cathode electrode in ohmic contact with the semiconductor substrate; a first conductive member embedded in a first trench provided in the central region of the drift layer via an insulating film and connected to the anode electrode; as well as A second conductive member is in contact with the field insulating film and is electrically connected to the semiconductor substrate.

2. The Schottky barrier diode according to claim 1, wherein A portion of the second conductive member is located on the field insulating film.

3. The Schottky barrier diode according to claim 1, wherein The drift layer further has a second trench reaching the semiconductor substrate. The second conductive member is buried in the second trench.

4. The Schottky barrier diode according to claim 3, wherein: The second groove is provided in a ring shape so as to surround the anode electrode in a plan view seen from the stacking direction.

5. The Schottky barrier diode according to claim 3, wherein: In the second conductive member, a portion located at the bottom of the second trench and a portion located above the second trench are made of different metal materials.

6. The Schottky barrier diode according to any one of claims 1 to 5, wherein: At least a portion of the second conductive member is made of the same metal material as that of the anode electrode or the first conductive member.

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