Silicon carbide semiconductor device

Abstract

A silicon carbide semiconductor device equipped with a silicon carbide substrate having a first main surface and a second main surface on the side thereof opposite the first main surface, wherein the silicon carbide substrate has a drift region of a first conductive type, a body region provided on the drift region and being of a second conductive type which differs from the first conductive type, a source region provided on the body region so as to be separated from the drift region, and being of the first conductive type, and a contact region provided on the body region and being of the second conductive type, wherein: the first main surface is provided with a plurality of gate trenches which extend in a first direction parallel to the first surface and are demarcated by a lateral surface which extends through the source region and the body region to the drift region, and also by a floor surface which is contiguous with the lateral surface; and the contact region contacts one first gate trench among the plurality of gate trenches from both sides in a second direction perpendicular to the first direction, and is separated from a second gate trench which is adjacent to the first gate trench in the second direction.

Description

[Technical field]

[0001] The present disclosure relates to silicon carbide semiconductor devices.

[0002] This application claims priority to Japanese Application No. 2020-213691, filed on December 23, 2020, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0003] As one silicon carbide semiconductor device, a trench-gate MOSFET (Metal Oxide Semiconductor Field Effect Transistor) has been disclosed in which contact regions connected to a body region are arranged discontinuously along a gate trench inside a contact hole formed in an interlayer insulating film (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2012-23291 Summary of the Invention

[0005] a source region provided on the body region so as to be separated from the drift region and having the first conductivity type; and a contact region provided on the body region and having the second conductivity type, the first main surface having a first gate trench and a second gate trench having a first conductivity type, the source region being provided on the body region so as to be separated from the drift region and having the first conductivity type; and a contact region provided on the body region and having the second conductivity type, the first main surface having a plurality of gate trenches defined by side surfaces penetrating the source region and the body region to reach the drift region and a bottom surface continuous with the side surfaces, the gate trenches extending in a first direction parallel to the first main surface, the contact region contacting a first gate trench of the plurality of gate trenches from both sides in a second direction perpendicular to the first direction, and being separated from a second gate trench adjacent to the first gate trench in the second direction. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing the relationship between an interlayer insulating film, a source region, and a contact region in a silicon carbide semiconductor device according to the embodiment. [Diagram 2] FIG. 2 is a cross-sectional view (part 1) showing the configuration of the silicon carbide semiconductor device according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view (part 2) showing the configuration of the silicon carbide semiconductor device according to the embodiment. [Figure 4] 4A to 4C are cross-sectional views (part 1) illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Diagram 5] FIG. 5 is a cross-sectional view (part 2) illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 6] 6A to 6C are cross-sectional views (part 3) illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 7] 7A to 7C are cross-sectional views (part 4) illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 8]8A to 8C are cross-sectional views (part 5) illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 9] FIG. 9 is a cross-sectional view (part 6) illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 10] FIG. 10 is a cross-sectional view (part 7) illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 11] FIG. 11 is a cross-sectional view (part 8) illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 12] FIG. 12 is a ninth cross-sectional view illustrating the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 13] FIG. 13 is a diagram showing the relationship between a source region and a contact region in a manufacturing method of a silicon carbide semiconductor device according to the embodiment. [Figure 14] FIG. 14 is a diagram showing the relationship between a gate trench, a source region, and a contact region in the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 15] FIG. 15 is a diagram showing the relationship between an interlayer insulating film, a source region, and a contact region in a manufacturing method of a silicon carbide semiconductor device according to the embodiment. [Figure 16] FIG. 16 is a diagram showing the relationship between the source region and the contact region when pattern misalignment occurs in the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 17] FIG. 17 is a diagram showing the relationship between an interlayer insulating film, a source region, and a contact region when pattern misalignment occurs in the method for manufacturing a silicon carbide semiconductor device according to the embodiment. [Figure 18] FIG. 18 is a cross-sectional view showing the configuration of a silicon carbide semiconductor device according to the embodiment in which pattern misalignment occurs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [Problem that this disclosure aims to solve] Conventional MOSFETs with discontinuously arranged contact regions tend to have low uniformity in temperature distribution during operation. This is because the current between the source and drain flows through the source region, but not through the contact region, which tends to cause temperature unevenness. Also, if the contact region is arranged inside the contact hole, if the pattern is misaligned during manufacturing, the area of ​​the contact region becomes insufficient, causing fluctuations in characteristics.

[0008] An object of the present disclosure is to provide a silicon carbide semiconductor device capable of improving the uniformity of temperature distribution during operation.

[0009] [Effects of this disclosure] According to the present disclosure, the uniformity of temperature distribution during operation can be improved.

[0010] The embodiments for carrying out the invention are described below.

[0011] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements are given the same symbols, and the same description will not be repeated. In the crystallographic description in this specification, individual orientations are represented by [], collective orientations by <>, individual planes by (), and collective planes by {}. In addition, when a crystallographic index is negative, it is usually represented by placing a "-" (bar) above the number, but in this specification, a negative sign is placed before the number.

[0012] [1] A silicon carbide semiconductor device according to an aspect of the present disclosure includes a silicon carbide substrate having a first main surface and a second main surface opposite to the first main surface, the silicon carbide substrate having a drift region having a first conductivity type, a body region provided on the drift region and having a second conductivity type different from the first conductivity type, a source region provided on the body region to be separated from the drift region and having the first conductivity type, and a contact region provided on the body region and having the second conductivity type, the first main surface having a plurality of gate trenches defined by side surfaces penetrating the source region and the body region to reach the drift region and a bottom surface continuous with the side surfaces, the gate trenches extending in a first direction parallel to the first main surface, the contact region contacting one of the plurality of gate trenches from both sides in a second direction perpendicular to the first direction and being separated from a second gate trench adjacent to the first gate trench in the second direction.

[0013] The contact region is in contact with the first gate trench and is separated from the second gate trench. When the contact region is in contact with the first gate trench and the second gate trench, the source region is divided by the contact region in the first direction. When the source region is turned on, the contact region is a conductive region and the contact region is a non-conductive region, so that in this case, the conductive region is divided by the non-conductive region in the first direction. In contrast, in the silicon carbide semiconductor device according to the present embodiment, the source region exists between the second gate trench and the contact region, and the source region is continuous in the first direction. Therefore, the silicon carbide semiconductor device according to the present embodiment can ensure a conductive region that is continuous in the first direction. In addition, heat is generated by the flow of current, but since the conductive region is continuous in the first direction, the uniformity of the heat generation can be improved, and the uniformity of the temperature distribution can be improved. Furthermore, since the contact region is in contact with the first gate trench from both sides in the second direction, the total area of ​​the contact region can be kept constant even if a pattern misalignment occurs when the contact region is formed. Therefore, stable characteristics can be obtained even if the contact region is misaligned.

[0014] [2] In [1], the gate trenches may be arranged at a first pitch in the second direction, and the dimension of the contact region in the second direction may be 0.90 to 1.10 times the first pitch. In this case, it is easy to apply a potential to the body region through the contact region, and it is easy to pass a sufficient current through the source region.

[0015] [3] In the configuration of [1] or [2], a plurality of the contact regions may be arranged along the first gate trench in the first direction. In this case, it is easy to improve the uniformity of the temperature distribution.

[0016] [4] In any one of [1] to [3], the source region may be continuous in the first direction between the first gate trench and the second gate trench, making it easier to pass a large current.

[0017] [5] In any of [1] to [4], the contact regions may be arranged in the second direction, every other one of the gate trenches, making it easy to pass a large current and apply a potential to the body region through the contact regions.

[0018] [6] In any of [1] to [5], the contact regions may be arranged in a diagonal lattice pattern with respect to the first direction and the second direction, making it easy to pass a large current and apply a potential to the body region through the contact regions.

[0019] [7] In any one of [1] to [6], the side surface of the gate trench may include a {0-33-8} plane or a {11-20} plane, whereby good mobility can be obtained on the side surface of the gate trench and channel resistance can be reduced.

[0020] [Embodiments of the present disclosure] An embodiment of the present disclosure relates to a so-called vertical MOSFET (silicon carbide semiconductor device). FIG. 1 is a diagram showing the relationship between an interlayer insulating film, a source region, and a contact region in a silicon carbide semiconductor device according to an embodiment. FIGS. 2 and 3 are cross-sectional views showing a configuration of a silicon carbide semiconductor device according to an embodiment. FIG. 1 corresponds to a plan view showing an arrangement of a gate trench, a source region, and a contact region in a first main surface of a silicon carbide substrate. FIG. 2 corresponds to a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 corresponds to a cross-sectional view taken along line III-III in FIG. 1.

[0021] As shown in FIGS. 1 to 3, the MOSFET 100 according to this embodiment mainly includes a silicon carbide substrate 10, a gate insulating film 81, a gate electrode 82, an interlayer insulating film 83, a source electrode 60, and a drain electrode 70. The silicon carbide substrate 10 includes a silicon carbide single crystal substrate 50 and a silicon carbide epitaxial layer 40 on the silicon carbide single crystal substrate 50. The silicon carbide substrate 10 has a first main surface 1 and a second main surface 2 opposite to the first main surface 1. The silicon carbide epitaxial layer 40 constitutes the first main surface 1, and the silicon carbide single crystal substrate 50 constitutes the second main surface 2. The silicon carbide single crystal substrate 50 and the silicon carbide epitaxial layer 40 are made of, for example, hexagonal silicon carbide of polytype 4H. Silicon carbide single crystal substrate 50 contains donors (n-type impurities) such as nitrogen (N) and has n-type (first conductivity type).

[0022] The first main surface 1 is a {0001} plane or a plane inclined at an off angle of 8° or less in the off direction. Preferably, the first main surface 1 is a (000-1) plane or a plane inclined at an off angle of 8° or less in the off direction. The off direction may be, for example, the <11-20> direction or the <1-100> direction. The off angle may be, for example, 1° or more, or 2° or more. The off angle may be 6° or less, or 4° or less.

[0023] The silicon carbide epitaxial layer 40 mainly includes a drift region 11, a body region 12, a source region 13, and a contact region .

[0024] The drift region 11 has n-type conductivity by being doped with a donor such as nitrogen or phosphorus (P). The donor is preferably doped to the drift region 11 by doping with an impurity during the epitaxial growth of the drift region 11, rather than by ion implantation. The donor concentration of the drift region 11 is preferably lower than the donor concentration of the silicon carbide single crystal substrate 50. The donor concentration of the drift region 11 is preferably 1×10 15 cm -3 5×10 or more 16 cm -3 For example, 8×10 15 cm -3 That's about it.

[0025] The body region 12 is provided on the drift region 11. The body region 12 has a p-type (second conductivity type) by being doped with an acceptor (p-type impurity) such as aluminum (Al). The acceptor concentration of the body region 12 is, for example, 1×10 18 cm -3 That's about it.

[0026] The source region 13 is provided on the body region 12 so as to be separated from the drift region 11 by the body region 12. The source region 13 has n-type conductivity by being doped with a donor such as nitrogen or phosphorus. The source region 13 constitutes the first main surface 1. The donor concentration of the source region 13 is, for example, 1×10 19 cm -3 That's about it.

[0027] The contact region 18 is doped with an acceptor such as aluminum and has a p-type conductivity. The contact region 18 constitutes the first main surface 1. The contact region 18 penetrates the source region 13 and contacts the body region 12. The acceptor concentration of the contact region 18 is, for example, 1×10 18 cm -3 More than 1×10 20 cm -3 The following is the result.

[0028] A plurality of gate trenches 5 are provided on the first main surface 1. The gate trenches 5 extend, for example, in a first direction parallel to the first main surface 1, and the plurality of gate trenches 5 are arranged in a second direction parallel to the first main surface 1 and perpendicular to the first direction. The gate trenches 5 have a bottom surface 4 made of the drift region 11. The gate trenches 5 have a side surface 3 that penetrates the contact region 18, the source region 13, and the body region 12 and continues to the bottom surface 4. The bottom surface 4 is, for example, a plane parallel to the second main surface 2. The angle θ1 of the side surface 3 with respect to a plane including the bottom surface 4 is, for example, 45° or more and 65° or less. The angle θ1 may be, for example, 50° or more. The angle θ1 may be, for example, 60° or less. The side surface 3 preferably has a {0-33-8} plane or a {11-20} plane. The {0-33-8} plane and the {11-20} plane are crystal planes that provide excellent mobility.

[0029] A plurality of contact regions 18 are arranged along the gate trench 5 in the first direction. Each contact region 18 contacts one of the plurality of gate trenches 5 from both sides in the second direction. If the gate trench 5 to which the contact region 18 contacts is the first gate trench, and the gate trench 5 adjacent to the first gate trench in the second direction is the second gate trench, the contact region 18 is separated from the second gate trench. A source region 13 may be present between the contact region 18 and the second gate trench. The source region 13 may be continuous in the first direction between the first gate trench and the second gate trench. A plurality of contact regions 18 may be arranged every other gate trench 5 in the second direction. A plurality of contact regions 18 may be arranged in a diagonal lattice pattern with respect to the first direction and the second direction.

[0030] The gate insulating film 81 is, for example, an oxide film. The gate insulating film 81 is made of, for example, a material containing silicon dioxide. The gate insulating film 81 contacts the side surface 3 and the bottom surface 4. The gate insulating film 81 contacts the drift region 11 at the bottom surface 4. The gate insulating film 81 contacts each of the contact region 18, the source region 13, the body region 12, and the drift region 11 at the side surface 3. The gate insulating film 81 may be in contact with the source region 13 at the first main surface 1.

[0031] The gate electrode 82 is provided on the gate insulating film 81. The gate electrode 82 is made of, for example, polysilicon (poly-Si) containing conductive impurities. The gate electrode 82 is disposed inside the gate trench 5.

[0032] The interlayer insulating film 83 is provided in contact with the gate electrode 82 and the gate insulating film 81. The interlayer insulating film 83 is made of a material containing, for example, silicon dioxide. The interlayer insulating film 83 electrically insulates the gate electrode 82 and the source electrode 60 from each other.

[0033] Contact holes 90 are formed in the interlayer insulating film 83 and the gate insulating film 81 at regular intervals in the second direction. The contact holes 90 are provided such that the gate trench 5 is located between the contact holes 90 adjacent to each other in the second direction. The contact holes 90 extend in the first direction. Through the contact holes 90, the source region 13 and the contact region 18 are exposed from the interlayer insulating film 83 and the gate insulating film 81.

[0034] The source electrode 60 is in contact with the first main surface 1. The source electrode 60 has a contact electrode 61 provided in the contact hole 90 and a source wiring 62. The contact electrode 61 is in contact with the source region 13 and the contact region 18 on the first main surface 1. The contact electrode 61 is made of a material containing, for example, nickel silicide (NiSi). The contact electrode 61 may be made of a material containing titanium (Ti), Al, and Si. The contact electrode 61 is in ohmic junction with the source region 13 and the contact region 18. The source wiring 62 covers the upper surface and side surfaces of the interlayer insulating film 83 and the upper surface of the contact electrode 61. The source wiring 62 is in contact with the contact electrode 61. The source wiring 62 is made of a material containing, for example, Al.

[0035] The drain electrode 70 is in contact with the second main surface 2. The drain electrode 70 is in contact with the silicon carbide single crystal substrate 50 at the second main surface 2. The drain electrode 70 is electrically connected to the drift region 11. The drain electrode 70 is made of a material containing NiSi, for example. The drain electrode 70 may be made of a material containing Ti, Al, and Si. The drain electrode 70 is in ohmic junction with the silicon carbide single crystal substrate 50.

[0036] The acceptor concentration and donor concentration in each of the impurity regions can be measured, for example, by using a scanning capacitance microscope (SCM) or secondary ion mass spectrometry (SIMS).

[0037] Next, a method for manufacturing the MOSFET 100 according to the embodiment will be described. FIGS. 4 to 12 are cross-sectional views showing the method for manufacturing the MOSFET 100 according to the embodiment. FIGS. 4 to 12 show changes in the cross section shown in FIG. 2. FIG. 13 is a view showing the relationship between the source region 13 and the contact region 18 in the method for manufacturing the MOSFET 100 according to the embodiment. FIG. 14 is a view showing the relationship between the gate trench 5, the source region 13, and the contact region 18 in the method for manufacturing the MOSFET 100 according to the embodiment. FIG. 15 is a view showing the relationship between the interlayer insulating film 83, the source region 13, and the contact region 18 in the method for manufacturing the MOSFET 100 according to the embodiment.

[0038] First, as shown in FIG. 4 and FIG. 13, the drift region 11 is formed on the silicon carbide single crystal substrate 50 by epitaxial growth. This epitaxial growth can be performed by a chemical vapor deposition (CVD) method using, for example, a mixed gas of silane (SiH4) and propane (C3H8) as a raw material gas and, for example, hydrogen gas (H2) as a carrier gas. In addition, at this time, it is preferable to introduce, for example, nitrogen (N) or phosphorus (P) as a donor. Next, a body region 12 on the drift region 11 and a source region 13 on the body region 12 are formed. Specifically, ion implantation is performed on the upper surface of the drift region 11. In the ion implantation for forming the body region 12, an acceptor such as aluminum (Al) is ion-implanted. In the ion implantation for forming the source region 13, a donor such as phosphorus (P) is ion-implanted. As a result, a silicon carbide substrate 10 having the drift region 11, the body region 12, and the source region 13 is formed. Instead of ion implantation, epitaxial growth may be used with the addition of impurities. Next, contact region 18 is formed by ion implantation. As shown in FIG. 13, contact region 18 is formed in an island shape so as to intersect with the region where gate trench 5 is formed. Next, activation heat treatment is performed to activate the impurities added by ion implantation. The temperature of this heat treatment is preferably 1500° C. or higher and 1900° C. or lower, for example, about 1700° C. The heat treatment time is, for example, about 30 minutes. The heat treatment atmosphere is preferably an inert gas atmosphere, for example, an Ar atmosphere. In this manner, silicon carbide substrate 10 is prepared.

[0039] 5, a mask 9 having openings that partially expose the source region 13 and the contact region 18 is formed on the silicon carbide substrate 10. The openings are formed to correspond to the positions of the gate trenches 5. As the mask 9, for example, a silicon oxide film formed by thermal oxidation can be used.

[0040] 6, in the opening of the mask 9, the source region 13, the contact region 18, the body region 12, and a part of the drift region 11 are removed by etching. As the etching method, for example, reactive ion etching (RIE), particularly inductively coupled plasma (ICP) RIE, can be used. Specifically, for example, ICP-RIE using SF6 or a mixed gas of SF6 and O2 as a reactive gas can be used. By such etching, a recess 5A having an inner surface 3A whose side surface is substantially perpendicular to the main surface of the silicon carbide single crystal substrate 50 can be formed in the region where the gate trench 5 is to be formed.

[0041] Next, the silicon carbide substrate 10 is etched using the mask 9. Specifically, the silicon carbide substrate 10 is thermally etched on the inner surface 3A of the recess 5A. The thermal etching can be performed, for example, by heating the silicon carbide substrate 10 in an atmosphere containing a reactive gas having at least one or more types of halogen atoms. The at least one or more types of halogen atoms include at least one of chlorine (Cl) atoms and fluorine (F) atoms. This atmosphere is, for example, Cl2, BCl3, SF6, or CF4. For example, a mixed gas of chlorine gas and oxygen gas is used as the reactive gas, and the thermal etching is performed at a heat treatment temperature of, for example, 700°C or more and 1000°C or less. The reactive gas may contain a carrier gas in addition to chlorine gas and oxygen gas. For example, nitrogen (N2) gas, argon gas, helium gas, or the like can be used as the carrier gas. When the heat treatment temperature is set to 700°C or more and 1000°C or less as described above, the etching rate of SiC is, for example, about 70 μm / hour. Also in this case, the mask 9 made of silicon oxide has a very high selectivity to SiC and is therefore not substantially etched during etching of SiC.

[0042] 7 and 14, a gate trench 5 having a side surface 3 and a bottom surface 4 is formed in a silicon carbide substrate 10 by the above-mentioned thermal etching. When forming the gate trench 5, the silicon carbide substrate 10 is etched so as to be side-etched from the opening of the mask 9 as shown by an arrow SE. Furthermore, during the thermal etching, a {0-33-8} plane is automatically formed on the side surface 3.

[0043] Next, as shown in FIG. 8, the mask 9 is removed from the first main surface 1, and a gate insulating film 81 is formed. For example, the silicon carbide substrate 10 is thermally oxidized to form the gate insulating film 81 in contact with the source region 13, the body region 12, the drift region 11, and the contact region 18. Specifically, the silicon carbide substrate 10 is heated in an oxygen-containing atmosphere at a temperature of, for example, 1300° C. or higher and 1400° C. or lower. As a result, the gate insulating film 81 in contact with the first main surface 1, the side surface 3, and the bottom surface 4 is formed. When the gate insulating film 81 is formed by thermal oxidation, strictly speaking, a part of the silicon carbide substrate 10 is taken into the gate insulating film 81. For this reason, in the subsequent processing, it is assumed that the first main surface 1, the side surface 3, and the bottom surface 4 have moved slightly to the interface between the gate insulating film 81 and the silicon carbide substrate 10 after thermal oxidation.

[0044] Next, the silicon carbide substrate 10 may be subjected to a heat treatment (NO annealing) in a nitric oxide (NO) gas atmosphere. In the NO annealing, the silicon carbide substrate 10 is held, for example, for about one hour under conditions of 1100° C. or higher and 1400° C. or lower. This introduces nitrogen atoms into the interface region between the gate insulating film 81 and the body region 12. As a result, the formation of an interface state in the interface region is suppressed, and channel mobility can be improved.

[0045] 9, a gate electrode 82 is formed. The gate electrode 82 is formed on the gate insulating film 81. The gate electrode 82 is formed by, for example, a low pressure chemical vapor deposition (LP-CVD) method. The gate electrode 82 is formed so as to face each of the source region 13, the body region 12, and the drift region 11.

[0046] 10, an interlayer insulating film 83 is formed. Specifically, the interlayer insulating film 83 is formed so as to cover the gate electrode 82 and to be in contact with the gate insulating film 81. The interlayer insulating film 83 is formed by, for example, a CVD method. The interlayer insulating film 83 is made of, for example, a material containing silicon dioxide. A part of the interlayer insulating film 83 may be formed inside the gate trench 5.

[0047] 11 and 15, the interlayer insulating film 83 and the gate insulating film 81 are etched to form contact holes 90 in the interlayer insulating film 83 and the gate insulating film 81. As a result, the source region 13 and the contact region 18 are exposed from the interlayer insulating film 83 and the gate insulating film 81.

[0048] Next, a metal film (not shown) for the contact electrode 61 is formed on the first main surface 1 in contact with the source region 13 and the contact region 18. The metal film for the contact electrode 61 is formed by, for example, a sputtering method. The metal film for the contact electrode 61 is made of, for example, a material containing Ni. Next, a metal film (not shown) for the drain electrode 70 is formed on the second main surface 2 in contact with the silicon carbide single crystal substrate 50. The metal film for the drain electrode 70 is formed by, for example, a sputtering method. The metal film for the drain electrode 70 is made of, for example, a material containing Ni.

[0049] Next, alloying annealing is performed. The metal film for the contact electrode 61 and the metal film for the drain electrode 70 are held at a temperature of, for example, 900° C. or higher and 1100° C. or lower for about 5 minutes. As a result, at least a part of the metal film for the contact electrode 61 and at least a part of the metal film for the drain electrode 70 reacts with silicon contained in the silicon carbide substrate 10 and is silicided. As a result, the contact electrode 61 that makes ohmic contact with the source region 13 and the contact region 18, and the drain electrode 70 that makes ohmic contact with the silicon carbide single crystal substrate 50 are formed. The contact electrode 61 may be made of a material containing Ti, Al, and Si. The drain electrode 70 may be made of a material containing Ti, Al, and Si.

[0050] Next, as shown in FIG. 12, the source wiring 62 is formed. Specifically, the source wiring 62 is formed to cover the contact electrode 61 and the interlayer insulating film 83. The source wiring 62 is formed, for example, by film formation using a sputtering method and RIE. The source wiring 62 is made of a material containing aluminum, for example. In this manner, the source electrode 60 having the contact electrode 61 and the source wiring 62 is formed.

[0051] In this manner, the MOSFET 100 according to the embodiment is completed.

[0052] In the MOSFET 100 according to this embodiment, a current flows between the source electrode 60 and the drain electrode 70 when the MOSFET 100 is turned on. This current flows through the source region 13, but does not flow through the contact region 18. That is, the source region 13 becomes a conductive region, and the contact region 18 becomes a non-conductive region. The contact region 18 contacts one gate trench 5, but is separated from the adjacent gate trench 5. Therefore, the source region 13 exists between the adjacent gate trench 5 and the contact region 18, and the source region 13 is continuous in the first direction. When the contact region 18 contacts two gate trenches 5, the source region 13 is divided by the contact region 18 in the first direction. Therefore, according to this embodiment, a conductive region that is continuous in the first direction can be secured. In addition, heat is generated by the flow of a current, but since the conductive region is continuous in the first direction, the uniformity of the heat generation can be improved, and the uniformity of the temperature distribution can be improved.

[0053] Furthermore, since the contact regions 18 contact one gate trench 5 from both sides in the second direction, the total area of ​​the contact regions 18 exposed in the contact holes 90 can be kept constant even if the pattern is misaligned during the formation of the contact regions 18, as described below. FIGS. 16 to 18 are diagrams showing the MOSFET 100 when the pattern is misaligned. FIG. 16 is a diagram showing the relationship between the source region 13 and the contact region 18 when the pattern is misaligned in the manufacturing method of the MOSFET 100 according to the embodiment. FIG. 17 is a diagram showing the relationship between the interlayer insulating film 83, the source region 13, and the contact region 18 when the pattern is misaligned in the manufacturing method of the MOSFET 100 according to the embodiment. FIG. 18 is a cross-sectional view showing the configuration of the MOSFET 100 according to the embodiment when the pattern is misaligned.

[0054] Here, it is assumed that the contact regions 18 are formed shifted in the second direction due to a misalignment of the pattern as shown in Fig. 16. In such a case, in the MOSFET 100 manufactured by carrying out the process of the above embodiment, the misalignment of the contact regions 18 remains as shown in Figs. 17 and 18. However, the total area of ​​the contact regions 18 exposed in the contact holes 90 is the same as the total area in the case where no misalignment occurs (see Fig. 15). Therefore, even if the contact regions 18 are misaligned, the characteristics are unlikely to fluctuate, and stable characteristics can be obtained.

[0055] Furthermore, in this embodiment, the multiple contact regions 18 are arranged along the gate trench 5 in the first direction, which makes it easier to improve the uniformity of the temperature distribution.

[0056] Since the source region 13 is continuous in the first direction, a wide conductive region is ensured, and it is easy to pass a current over a wider range, that is, it is easy to pass a large current.

[0057] Since the contact regions 18 are arranged in the second direction so as to alternate with the gate trenches 5, a large current can be easily passed and a potential can be easily applied to the body region 12 from the source electrode 60.

[0058] Since the contact regions 18 are arranged in a diagonal lattice pattern in the first and second directions, a large current can be easily passed and a potential can be easily applied from the source electrode 60 to the body region 12.

[0059] As shown in FIG. 1, a plurality of gate trenches 5 are arranged in the second direction at a first pitch P, and the dimension L of the contact region 18 in the second direction is preferably 0.90 times to 1.10 times the first pitch P, and more preferably 0.92 times to 1.08 times. If the dimension L is less than 0.90 times the first pitch P, the contact region 18 may be too small, making it difficult to apply a sufficient electric potential to the body region 12. If the dimension L is more than 1.10 times the first pitch P, the contact region 18 may be too large, and the contact region 18 may contact two adjacent gate trenches 5 when a pattern shift occurs. If the contact region 18 contacts two adjacent gate trenches 5, the conductive region is divided by the non-conductive region in the first direction, which may reduce the uniformity of heat generation and the uniformity of the temperature distribution.

[0060] Although the embodiments have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the claims. [Explanation of symbols]

[0061] 1 First main surface 2 Second main surface 3. Aspects 3A Inner surface 4 Bottom 5. Gate trench 5A Recess 9. Mask 10 Silicon carbide substrate 11 Drift Region 12 Body Region 13 Source Area 18 Contact Area 40 Silicon carbide epitaxial layer 50 Silicon carbide single crystal substrate 60 Source electrode 61 Contact electrode 62 Source wiring 70 Drain electrode 81 Gate insulating film 82 Gate electrode 83 Interlayer insulating film 90 Contact Hole 100 MOSFET

Claims

1. A silicon carbide substrate having a first main surface and a second main surface opposite the first main surface, The silicon carbide substrate is a drift region having a first conductivity type; a body region provided on the drift region and having a second conductivity type different from the first conductivity type; a source region having the first conductivity type and provided on the body region to be separated from the drift region; a contact region provided on the body region and having the second conductivity type; having a plurality of gate trenches are provided in the first main surface, the gate trenches being defined by side surfaces that penetrate the source region and the body region to reach the drift region and bottom surfaces that are continuous with the side surfaces, and the gate trenches extend in a first direction parallel to the first main surface; the contact region contacts a first gate trench, which is one of the plurality of gate trenches, from both sides in a second direction perpendicular to the first direction, and is spaced apart from a second gate trench adjacent to the first gate trench in the second direction; The gate trenches are arranged at a first pitch in the second direction, a dimension of the contact region in the second direction that is not less than 0.90 times and not more than 1.10 times the first pitch;

2. A silicon carbide semiconductor device as described in claim 1, wherein a plurality of the contact regions are arranged in the second direction, alternately between a plurality of the gate trenches.

3. A silicon carbide substrate having a first main surface and a second main surface opposite the first main surface, The silicon carbide substrate is a drift region having a first conductivity type; a body region provided on the drift region and having a second conductivity type different from the first conductivity type; a source region having the first conductivity type and provided on the body region to be separated from the drift region; a contact region provided on the body region and having the second conductivity type; having a plurality of gate trenches are provided in the first main surface, the gate trenches being defined by side surfaces that penetrate the source region and the body region to reach the drift region and bottom surfaces that are continuous with the side surfaces, and the gate trenches extend in a first direction parallel to the first main surface; the contact region contacts a first gate trench, which is one of the plurality of gate trenches, from both sides in a second direction perpendicular to the first direction, and is spaced apart from a second gate trench adjacent to the first gate trench in the second direction; a plurality of the contact regions are arranged in the second direction, every other one of the plurality of the gate trenches;

4. The silicon carbide semiconductor device according to claim 1 , wherein a plurality of the contact regions are arranged in the first direction along the first gate trench.

5. A silicon carbide substrate having a first main surface and a second main surface opposite the first main surface, The silicon carbide substrate is a drift region having a first conductivity type; a body region provided on the drift region and having a second conductivity type different from the first conductivity type; a source region having the first conductivity type and provided on the body region to be separated from the drift region; a plurality of first contact regions and a plurality of second contact regions provided on the body region and having the second conductivity type; having a plurality of gate trenches are provided in the first main surface, the gate trenches being defined by side surfaces that penetrate the source region and the body region to reach the drift region and bottom surfaces that are continuous with the side surfaces, and the gate trenches extend in a first direction parallel to the first main surface; the first contact region contacts one first gate trench of the plurality of gate trenches from both sides in a second direction perpendicular to the first direction, and is spaced apart from a second gate trench adjacent to the first gate trench in the second direction; the second contact region contacts the second gate trench from both sides in the second direction and is spaced apart from the first gate trench in the second direction; A plurality of the first contact regions are arranged in the first direction, A plurality of the second contact regions are arranged in the first direction, In the second direction, only the source region is between the first contact region and the second gate trench; a source region provided between the second contact region and the first gate trench;

6. The plurality of gate trenches are arranged at a first pitch in the second direction, 6 . The silicon carbide semiconductor device according to claim 5 , wherein a dimension of said first contact region in said second direction and a dimension of said second contact region in said second direction are not less than 0.90 times and not more than 1.10 times the first pitch.

7. The silicon carbide semiconductor device according to claim 1 , wherein the source region is continuous in the first direction between the first gate trench and the second gate trench.

8. 8. The silicon carbide semiconductor device according to claim 1, wherein the side surface of the gate trench includes a {0-33-8} plane or a {11-20} plane.

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