Semiconductor device and manufacturing method thereof

Abstract

To provide semiconductor devices and a method for manufacturing semiconductor devices capable of suppressing warpage.SOLUTION: A semiconductor device according to an embodiment includes a first conductive layer, a semiconductor layer, first and second control electrodes, and first and second electrode pads. The first conductive layer includes a first conductive region and a second conductive region. The second conductive region has a thinner thickness than the first conductive region. The semiconductor layer is provided over the first conductive layer. The semiconductor layer includes first to fifth semiconductor regions. The first control electrode faces the second semiconductor region through the first insulating film. The second control electrode faces the fourth semiconductor region through the second insulating film. The first electrode pad is provided above the semiconductor layer and electrically connected to the third semiconductor region. The second electrode pad is provided above the semiconductor layer and electrically connected to the fifth semiconductor region. At least a portion of the first conductive region is located below the first electrode pad and the second electrode pad.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a semiconductor device and a method for manufacturing the semiconductor device. [Background technology]

[0002] In semiconductor devices such as vertical MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), increasing the thickness of metal layers that serve as current paths and thinning the semiconductor substrate are being considered in order to reduce the on-resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-167281 [Patent Document 2] Patent No. 6065198 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, in semiconductor devices, warping may occur due to heat. For example, if warping occurs in the semiconductor device during a mounting process in which the semiconductor device is soldered onto a mounting board, there is a risk of connection failure.

[0005] An object of the present invention is to provide a semiconductor device capable of suppressing warpage and a method for manufacturing the semiconductor device. [Means for solving the problem]

[0006] The semiconductor device according to the embodiment includes a first conductive layer, a semiconductor layer, a first control electrode, a second control electrode, a first electrode pad, and a second electrode pad. Concave and convex portions are provided on at least one of the upper and lower surfaces of the first conductive layer. The first conductive layer includes a first conductive region and a second conductive region. The second conductive region has a thickness thinner than that of the first conductive region. The semiconductor layer is provided on the first conductive layer. The semiconductor layer includes a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type, a third semiconductor region of the first conductivity type, a fourth semiconductor region of the second conductivity type, and a fifth semiconductor region of the first conductivity type. The second semiconductor region is provided on a portion of the first semiconductor region. The third semiconductor region is provided on the second semiconductor region. The fourth semiconductor region is provided on another portion of the first semiconductor region. The fifth semiconductor region is provided on the fourth semiconductor region. The first control electrode faces the first semiconductor region, the second semiconductor region, and the third semiconductor region via a first insulating film. The second control electrode faces the first semiconductor region, the fourth semiconductor region, and the fifth semiconductor region via a second insulating film. The first electrode pad is provided above the semiconductor layer and electrically connected to the third semiconductor region. The second electrode pad is provided above the semiconductor layer and electrically connected to the fifth semiconductor region. At least a portion of the first conductive region is located below the first electrode pad and the second electrode pad. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic plan view illustrating a semiconductor device according to the embodiment. [Figure 2] FIG. 2 is a schematic perspective view illustrating a part of the semiconductor device according to the embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view illustrating the semiconductor device according to the embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view illustrating the semiconductor device according to the embodiment. [Figure 5] FIG. 5 is a schematic plan view illustrating the lower electrode of the semiconductor device according to the embodiment. [Figure 6] 6A and 6B are schematic cross-sectional views illustrating semiconductor devices according to modified examples of the embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view illustrating a semiconductor device according to a modified example of the embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view illustrating a semiconductor device according to a modified example of the embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view illustrating a semiconductor device according to a modified example of the embodiment. [Figure 10] 10(a) to 10(g) are schematic cross-sectional views illustrating the method for manufacturing the semiconductor device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In the present specification and the drawings, elements similar to those already explained are given the same reference numerals and detailed explanations will be omitted as appropriate. In each of the embodiments described below, the p-type (an example of the second conductivity type) and n-type (an example of the first conductivity type) of each semiconductor region may be reversed to implement each embodiment.

[0009] FIG. 1 is a schematic plan view illustrating a semiconductor device according to the embodiment. 1, the semiconductor device 100 according to the embodiment includes a first element region R1 and a second element region R2 aligned in the X direction. A first element Q1 is provided in the first element region R1, and a second element Q2 is provided in the second element region R2. The first element Q1 and the second element Q2 are transistors.

[0010] A source electrode 61 (conductive layer), a source electrode pad S1 (first electrode pad), and a gate electrode pad G1 are provided on the surface side of the first element region R1. In this example, one gate electrode pad G1 is arranged between two source electrode pads S1 (source electrode pads S1a and S1b) arranged side by side in the Y direction. The source electrode pad S1 is in contact with the top of the source electrode 61 and is electrically connected to the source electrode 61. For example, when viewed from above, the source electrode 61 is provided in an area surrounding the multiple source electrode pads S1 (excluding the gate electrode pad G1 and its surrounding area). The gate electrode pad G1 is electrically insulated from the source electrode pad S1 and the source electrode 61.

[0011] Similarly, a source electrode 62 (conductive layer), a source electrode pad S2 (second electrode pad), and a gate electrode pad G2 are provided on the surface side of the second element region R2. In this example, one gate electrode pad G2 is arranged between two source electrode pads S2 (source electrode pads S2a and S2b) aligned in the Y direction. The source electrode pad S2 is in contact with the top of the source electrode 62 and is electrically connected to the source electrode 62. For example, when viewed from above, the source electrode 62 is provided in an area surrounding the multiple source electrode pads S2 (excluding the gate electrode pad G2 and its surrounding area). The gate electrode pad G2 is electrically insulated from the source electrode pad S2 and the source electrode 62.

[0012] The source electrode pad S1 and the source electrode pad S2 are aligned in the X direction. The gate electrode pad G1 and the gate electrode pad G2 are aligned in the X direction. Note that the arrangement and shape of the source electrodes and each electrode pad shown in FIG. 1 are merely examples, and embodiments are not limited to those shown in the drawings.

[0013] 2A and 2B are schematic perspective views illustrating a part of the semiconductor device according to the embodiment. 2(a) shows a part of the cross section taken along the line A1-A1' in FIG. 1. FIG. 2(b) shows a part of the cross section taken along the line A2-A2' in FIG. 1. Note that FIG. 2 omits illustration of some elements (such as the lower electrode 11 (see FIG. 3), source electrode pads S1 and S2, and passivation layer). Also, the connection between the gate electrodes 41 and 42 and the gate electrode pads G1 and G2 is shown in a schematic circuit diagram. The semiconductor device 100 according to the embodiment includes a semiconductor layer 10 (semiconductor substrate) and a lower electrode 11 (first conductive layer) shown in FIG.

[0014] In the description of the embodiment, the direction from the lower electrode 11 to the semiconductor layer 10 is referred to as the Z direction (first direction), one direction perpendicular to the Z direction is referred to as the X direction (second direction), and the direction perpendicular to the Z direction and the X direction is referred to as the Y direction (third direction). The X direction and the Y direction are, for example, directions parallel to the surface of the semiconductor layer 10 (semiconductor substrate). For the sake of explanation, the direction from the lower electrode 11 to the semiconductor layer 10 is referred to as "up" and the opposite direction is referred to as "down." These directions are based on the relative positional relationship between the lower electrode 11 and the semiconductor layer 10 and are unrelated to the direction of gravity. The Z direction is, for example, a direction perpendicular to the top surface of the semiconductor substrate.

[0015] The semiconductor layer 10 is provided on the lower electrode 11. As shown in Fig. 2(a), the semiconductor layer 10 includes a semiconductor region 21 (first semiconductor region), a base region 22 (second semiconductor region), and a source region 23 (third semiconductor region). As shown in Fig. 2(b), the semiconductor layer 10 further includes a base region 24 (fourth semiconductor region) and a source region 25 (fifth semiconductor region).

[0016] The lower electrode 11 and the semiconductor region 21 are provided across the first element region R1 and the second element region R2. The semiconductor region 21 is provided on the lower electrode 11 and is of n-type (first conductivity type). For example, the portion of the semiconductor region 21 that contacts the lower electrode 11 may have a higher n-type impurity concentration than the upper portion thereof so as to be in ohmic contact with the lower electrode 11.

[0017] The base region 22 is provided on the semiconductor region 21 in the first element region R1 and is of p-type (second conductivity type). The source region 23 is selectively provided on the base region 22 and is of the first conductivity type. In this example, a plurality of source regions 23 are provided, and the plurality of source regions 23 are aligned in the Y direction.

[0018] Furthermore, the first element region R1 is provided with a gate electrode 41 (first control electrode) and a gate insulating film 51 (first insulating film). The first element Q1 is a field-effect transistor (e.g., a Metal-Oxide-Semiconductor Field-Effect Transistor: MOSFET) formed by a part of the semiconductor region 21, the base region 22, the source region 23, the gate electrode 41, and the gate insulating film 51.

[0019] The gate electrode 41 is provided on the semiconductor region 21 via a gate insulating film 51. The gate electrode 41 faces a part of the semiconductor region 21, the base region 22, and a part of the source region 23 via the gate insulating film 51. In this example, a plurality of gate electrodes 41 and gate insulating films 51 are provided. The plurality of gate electrodes 41 are aligned in the Y direction, and each gate electrode 41 extends in the X direction.

[0020] A plurality of trenches T1 are formed on the semiconductor region 21. The plurality of trenches T1 are aligned in the Y direction, and each trench T1 extends in the X direction. Each trench T1 is provided in the source region 23 and the base region 22, and reaches the semiconductor region 21. A gate insulating film 51 is provided in each trench T1, and a gate electrode 41 is provided on the gate insulating film 51. Furthermore, an insulating portion 55 is provided between the gate electrode 41 and the source electrode 61 in each trench T1.

[0021] 1 (a region below the first pad) including below one of the source electrode pads S1, and a region (a region below the second pad) including below the other of the source electrode pads S1. In each of the first pad region and the second pad region, a plurality of trenches T1, a plurality of gate electrodes 41, a plurality of gate insulating films 51, and a plurality of source regions 23 are arranged in the Y direction. In each of the first pad region and the second pad region, each of the trenches T1, each of the gate electrodes 41, each of the gate insulating films 51, and each of the source regions 23 extends in the X direction.

[0022] 1 via conductive parts such as a gate contact and gate wiring (not shown). For example, the gate wiring is provided on the upper surface of the semiconductor layer 10 and connected to the gate electrode pad G1. For example, the gate contact extends vertically so as to penetrate a part of the insulating part 55, and connects the gate electrode 41 and the gate wiring. However, the method and position of connecting the gate electrode and the gate electrode pad are not particularly limited.

[0023] The source electrode 61 is provided on the plurality of source regions 23 and is electrically connected to the source regions 23. That is, the source electrode pad S1 is electrically connected to the source regions 23 via the source electrode 61. The source electrode pad S1 overlaps with a part of the source electrode 61, a part of the source regions 23, a part of the base region 22, and a part of the gate electrode 41 in the Z direction. The gate electrode 41 and the source electrode 61 are electrically insulated from each other by an insulating portion 55.

[0024] The second element region R2 may have the same configuration as the first element region R1. That is, in the second element region R2, the base region 24 is provided on the semiconductor region 21 and is of p-type (second conductivity type). The source region 25 is selectively provided on the base region 24 and is of the first conductivity type. The multiple source regions 25 are aligned in the Y direction. Furthermore, the second element region R2 is provided with a gate electrode 42 (second control electrode) and a gate insulating film 52 (second insulating film). The second element Q2 is a field-effect transistor formed by a part of the semiconductor region 21, the base region 24, the source region 25, the gate electrode 42, and the gate insulating film 52. The gate electrode 42 is provided on the semiconductor region 21 via a gate insulating film 52. The gate electrode 42 faces a part of the semiconductor region 21, the base region 24, and a part of the source region 25 via the gate insulating film 52. The multiple gate electrodes 42 are aligned in the Y direction, and each gate electrode 42 extends in the X direction. A plurality of trenches T2 are formed on the semiconductor region 21. The plurality of trenches T2 are aligned in the Y direction, and each trench T2 extends in the X direction. Each trench T2 is provided in the source region 25 and the base region 24, and reaches the semiconductor region 21. A gate insulating film 52 is provided in each trench T2, and a gate electrode 42 is provided on the gate insulating film 52. Furthermore, an insulating portion 56 is provided between the gate electrode 42 and the source electrode 62 in each trench T2. For example, the base region 24 is provided in each of a region (third pad under region) including below one of the source electrode pads S2 and a region (fourth pad under region) including below the other of the source electrode pads S2 shown in Fig. 1. In each of the third pad under region and the fourth pad under region, a plurality of trenches T2, a plurality of gate electrodes 42, a plurality of gate insulating films 52, and a plurality of source regions 25 are arranged in the Y direction. In each of the third pad under region and the fourth pad under region, each of the trenches T2, each of the gate electrodes 42, each of the gate insulating films 52, and each of the source regions 25 extends in the X direction. The source electrode 62 is provided on the plurality of source regions 25 and is electrically connected to the source regions 25. That is, the source electrode pad S2 is electrically connected to the source regions 25 via the source electrode 62. The source electrode pad S2 overlaps with a part of the source electrode 62, a part of the source regions 25, a part of the base region 24, and a part of the gate electrode 42 in the Z direction. The gate electrode 42 and the source electrode 62 are electrically insulated from each other by an insulating portion 56.

[0025] An insulating layer 70 is provided on the semiconductor layer 10 between the source electrode 61 and the source electrode 62. Although only five gate electrodes and five trenches are shown in Figures 2(a) and 2(b) for convenience, in the embodiment, the number of gate electrodes and trenches is arbitrary, and the gate electrodes and trenches may be arranged as shown in Figure 3, etc., which will be described later.

[0026] 3 and 4 are schematic cross-sectional views illustrating the semiconductor device according to the embodiment. Fig. 3 shows a cross section taken along line A3-A4 in Fig. 1. Fig. 4 shows a cross section taken along line A5-A6 in Fig. 1.

[0027] 3 and 4, a passivation layer 71 (insulating layer) is provided so as to cover the source electrode 61, the source electrode 62, and the insulating layer 70. A source electrode pad S1 contacts the source electrode 61 through an opening that penetrates the passivation layer 71. A source electrode pad S2 contacts the source electrode 62 through another opening that penetrates the passivation layer 71. For example, the semiconductor region 21 is provided with a drain layer 21a and a drift layer 21b on the drain layer 21a. The concentration of n-type impurities in the drain layer 21a is higher than the concentration of n-type impurities in the drift layer 21b.

[0028] At least one of the upper surface 11u and the lower surface 11d of the lower electrode 11 has an uneven surface. In this example, the upper surface 11u has an uneven surface (a recess 11r and a protrusion 11p protruding above the recess 11r). The lower surface 11d is flatter (for example, planar) than the upper surface 11u.

[0029] The lower electrode 11 has a first conductive region 11a including a protrusion 11p and a second conductive region 11b including a recess 11r. The thickness T11b of the second conductive region 11b is thinner than the thickness T11a of the first conductive region 11a. The thickness is the length along the Z direction. The thickness T11a is, for example, not less than 0.2 μm and not more than 50 μm. The thickness T11b is, for example, not less than 0.2 μm and not more than 50 μm.

[0030] 4, at least a portion of the first conductive region 11a is located below the source electrode pad S1 and below the source electrode pad S2. In other words, the first conductive region 11a overlaps with each of the source electrode pad S1 and the source electrode pad S2 in the Z direction.

[0031] For example, the first conductive region 11a is continuous at least from below the source electrode pad S1 to below the source electrode pad S2. That is, the first conductive region 11a is continuous from below the first element Q1 (below the gate electrode 41 and the source region 23) to below the second element Q2 (below the gate electrode 42 and the source region 25).

[0032] 3, at least a portion of the second conductive region 11b does not overlap with the source electrode pad S1 in the Z direction. The second conductive region 11b is located below a region between one source electrode pad S1 (source electrode pad S1a) and another source electrode pad S1 (source electrode pad S1b) in the Z direction. In this example, a portion of the second conductive region 11b is located below the gate electrode pad G1.

[0033] Although not shown, the cross section on the second element region R2 side (cross section passing through the source electrode pad S2 and the gate electrode pad G2) may be similar to the cross section on the first element region R1 side shown in Figure 3. That is, at least a part of the second conductive region 11b does not overlap with the source electrode pad S2 in the Z direction. The second conductive region 11b is located below a region between one source electrode pad S2 (source electrode pad S2a) and another source electrode pad S2 (source electrode pad S2b) in the Z direction. In this example, a part of the second conductive region 11b is located below the gate electrode pad G2.

[0034] 3 and 4, in this example, the lower surface 10d of the semiconductor layer 10 is provided with unevenness (a recess 10q and a protrusion 10p protruding downward from the recess 10q) along the upper surface of the lower electrode 11. The recess 10q contacts the protrusion 11p of the lower electrode 11, and the protrusion 10p contacts the recess 11r of the lower electrode 11. The semiconductor layer 10 includes a first semiconductor portion 10a provided on the first conductive region 11a and a second semiconductor portion 10b provided on the second conductive region 11b. The first semiconductor portion 10a includes the recess 10q, and the second semiconductor portion 10b includes the protrusion 10p. A thickness T10a of the first semiconductor portion 10a is thinner than a thickness T10b of the second semiconductor portion 10b. The thickness T10a is, for example, not less than 10 μm and not more than 100 μm. The thickness T10b is, for example, not less than 10 μm and not more than 150 μm. The upper surface of the semiconductor layer 10 may be flatter (for example, planar) than the lower surface 10d.

[0035] For example, the thickness T10a of the first semiconductor portion 10a is thinner than the thickness T11a of the first conductive region 11a. For example, the thickness T11b of the second conductive region 11b is thinner than the thickness of the second semiconductor portion 10b.

[0036] FIG. 5 is a schematic plan view illustrating the lower electrode of the semiconductor device according to the embodiment. In FIG. 5, the positions of the source electrode pads S1 and S2 and the gate electrode pads G1 and G2 are indicated by dashed lines.

[0037] 5, in the XY plane, the range in which the first conductive region 11a is provided surrounds the source electrode pad S1 and the source electrode pad S2. More specifically, in this example, the planar shape of one first conductive region 11a is a rectangle surrounding the source electrode pad S1a and the source electrode pad S2a when viewed from above. The planar shape of another first conductive region 11a is a rectangle surrounding the source electrode pad S1b and the source electrode pad S2b when viewed from above. The second conductive region 11b is a region other than the two first conductive regions 11a, and is arranged to surround the peripheries of the two first conductive regions 11a when viewed from above.

[0038] The source electrode pad S2a is, for example, the source electrode pad S2 that is closest to the source electrode pad S1a among the multiple source electrode pads S2. Similarly, the source electrode pad S2b is, for example, the source electrode pad S2 that is closest to the source electrode pad S1b among the multiple source electrode pads S2.

[0039] An example of the material of each component of the semiconductor device 100 will be described. The semiconductor region 21, the base regions 22 and 24, and the source regions 23 and 25 contain silicon, silicon carbide, gallium nitride, or gallium arsenide as the semiconductor material. When silicon is used as the semiconductor material, arsenic, phosphorus, or antimony can be used as the n-type impurity. Boron can be used as the p-type impurity. For example, the base regions 22 and 24 and the source regions 23 and 25 can be formed by ion-implanting impurities into a silicon semiconductor substrate. A semiconductor substrate can be used for at least a portion of the semiconductor region 21. A portion of the semiconductor region 21 may be ion-implanted with impurities. The gate electrode 41 and the gate electrode 42 include a conductive material such as polysilicon doped with impurities. The gate insulating film 51, the gate insulating film 52, the insulating portion 55, and the insulating portion 56 contain an insulating material such as silicon oxide. The lower electrode 11, the source electrodes 61 and 62, the source electrode pads S1 and S2, and the gate electrode pads G1 and G2 contain a metal such as aluminum, copper, silver, titanium, tungsten, etc. The electrical resistivity (Ω·cm) of the lower electrode 11 is lower than the electrical resistivity of the semiconductor layer 10.

[0040] The operation of the semiconductor device 100 will now be described. As described above, the semiconductor device 100 includes the first element Q1 and the second element Q2 that operate as transistors. The lower electrode 11 serves as, for example, the drain electrodes of the first element Q1 and the second element Q2. In other words, the first element Q1 and the second element Q2 share a drain electrode.

[0041] The semiconductor device 100 operates by applying a gate bias to the gate electrodes 41 and 42 while a voltage is applied between the source electrodes 61 and 62. For example, when a gate bias is applied to the gate electrodes 41 and 42 to turn on the MOSFET, a current flows from the source electrode 61 to the source electrode 62 along the path cp1 shown in FIG. 4, or from the source electrode 62 to the source electrode 61 along the path cp2 shown in FIG. 4.

[0042] The path cp1 is a path that runs from the source electrode pad S1 to the source electrode pad S2 via the source electrode 61, the semiconductor layer 10 (first semiconductor portion 10a) below the source electrode pad S1, the lower electrode 11 (first conductive region 11a), the semiconductor layer 10 (first semiconductor portion 10a) below the source electrode pad S2, and the source electrode 62. The path cp2 is a path that runs in the opposite direction to the path cp1.

[0043] The effects of the embodiment will be described. In semiconductor devices, for example, to reduce on-resistance, efforts have been made to reduce the thickness of the semiconductor layer and / or the thickness of the lower electrode. However, when heat is applied to the semiconductor device, for example, during a mounting process (e.g., solder reflow) in which the semiconductor device is soldered onto a mounting substrate, stress may be generated in the semiconductor device due to the difference in thermal expansion between the lower electrode and the semiconductor layer, potentially causing the semiconductor device to warp. For example, if the lower electrode is thick, the stress generated in the semiconductor device due to heat may make the semiconductor device more susceptible to warping. Furthermore, if the semiconductor layer is thinned, the semiconductor device may be more susceptible to warping.

[0044] In contrast, in the embodiment, the lower electrode 11 includes a first conductive region 11a and a second conductive region 11b that is thinner than the first conductive region 11a. By providing the relatively thin second conductive region 11b, the thickness of the lower electrode 11 can be reduced, thereby suppressing warpage stress on the semiconductor device due to the lower electrode 11. Meanwhile, at least a portion of the relatively thick first conductive region 11a is located below the source electrode pad S1 and the source electrode pad S2. In other words, the lower electrode 11, which has low resistivity, is provided thick in current paths such as the above-mentioned paths cp1 and cp2. This reduces the electrical resistance in the current paths and the on-resistance of the semiconductor device. Therefore, according to the embodiment, warpage of the semiconductor device can be suppressed while reducing the on-resistance.

[0045] The semiconductor layer 10 includes a first semiconductor portion 10a and a second semiconductor portion 10b. The first semiconductor portion 10a is provided on the first conductive region 11a and is thinner than the second semiconductor portion 10b. For example, the first semiconductor portion 10a may be thinner than the first conductive region 11a. The relatively thin first semiconductor portion 10a can shorten the length of the semiconductor layer 10 in the current path. This can further reduce the electrical resistance of the semiconductor layer 10 in the current path. Therefore, the on-resistance of the semiconductor device can be further reduced. For example, the second conductive region 11b may be thinner than the second semiconductor portion 10b. The relatively thin second conductive region 11b can reduce the thickness of the lower electrode 11 and further reduce the warpage stress on the semiconductor device caused by the lower electrode 11.

[0046] As described above, the first conductive region 11a extends continuously from below the source electrode pad S1 to below the source electrode pad S2. In the XY plane, the area in which the first conductive region 11a is provided surrounds the source electrode pad S1 and the source electrode pad S2. That is, the lower electrode 11 is thickened in areas where the current density is relatively high in accordance with the element pattern. This further reduces the on-resistance. In this example, the upper surface 11u of the lower electrode 11 that contacts the semiconductor layer 10 is provided with irregularities in accordance with the element pattern. Meanwhile, the second conductive region 11b does not overlap with the source electrode pad S1 and the source electrode pad S2 in the Z direction, for example. That is, the lower electrode 11 is thinned in areas where the current density is relatively low in accordance with the element pattern. This further reduces warpage of the semiconductor device. In this way, by arranging the thicker portions of the lower electrode 11 (thinner portions of the semiconductor layer 10) in accordance with the element pattern, warpage of the semiconductor device can be suppressed while further reducing the on-resistance.

[0047] 6A and 6B are schematic cross-sectional views illustrating semiconductor devices according to modified examples of the embodiment. In the semiconductor device 101 shown in FIG. 6(a) and the semiconductor device 102 shown in FIG. 6(b), a conductive region 11c is further provided in the lower electrode 11. The conductive region 11c is thicker than the second conductive region 11b. In the example of FIG. 6(a), the thickness of the conductive region 11c is the same as the thickness of the first conductive region 11a. As shown in FIG. 6(b), the thickness of the conductive region 11c may be thinner than the thickness of the first conductive region 11a.

[0048] The conductive region 11c is located below the region between the two source electrode pads S1. For example, the conductive region 11c is located below the gate electrode pad G1. The conductive region 11c may also be provided below the region between the two source electrode pads S2. For example, by providing a relatively thick conductive region 11c, the region where the lower electrode 11 is thick and the semiconductor layer 10 is thin increases, making it easier to reduce the on-resistance.

[0049] FIG. 7 is a schematic cross-sectional view illustrating a semiconductor device according to a modified example of the embodiment. 7, the entire semiconductor layer 10 is thinned. That is, in this example, a relatively thick second semiconductor portion 10b is not provided, and the entire semiconductor layer 10 serves as the first semiconductor portion 10a. Also, in this example, unevenness (a recess 11r and a protrusion 11p protruding downward from the recess 11r) is provided on the lower surface 11d of the lower electrode 11. The upper surface of the lower electrode 11 is flatter (for example, flat) than the lower surface 11d.

[0050] By thinning the entire semiconductor layer 10, the length of the semiconductor layer 10 in the current path can be shortened, and the electrical resistance can be further reduced. Therefore, the on-resistance of the semiconductor device 100 can be more easily reduced.

[0051] 8 and 9 are schematic cross-sectional views illustrating a semiconductor device according to a modified example of the embodiment. In this example, the lower electrode 11 also includes a first conductive region 11a and a second conductive region 11b. The first conductive region 11a includes a portion located directly below the source electrode pad S1 and / or the source electrode pad S2. The second conductive region 11b includes a portion located directly below the space between two source electrode pads S1 (for example, directly below the gate electrode pad G1).

[0052] However, the semiconductor device 104 shown in Figures 8 and 9 has a different thickness of the first conductive region 11a compared to the semiconductor device 100 shown in Figures 3 and 4. Other than this, the semiconductor device 104 may be similar to the semiconductor device 100.

[0053] In the semiconductor device 104, the upper surface 11u and the lower surface 11d of the lower electrode 11 each have unevenness that conforms to the lower surface of the semiconductor layer 10. For example, the thickness T10a of the first semiconductor portion 10a may be thicker than the thickness T11a of the first conductive region 11a. Also, the thickness T10b of the second semiconductor portion 10b may be thicker than the thickness T11a of the first conductive region 11a.

[0054] The thickness T11a of the first conductive region 11a may be the same as the thickness T11b of the second conductive region, or the thickness T11a may be greater or less than the thickness T11b.

[0055] 8 and 9, the first semiconductor portion 10a is thinner than the second semiconductor portion 10b. The relatively thin first semiconductor portion 10a can suppress the on-resistance, as with the semiconductor device 100 described above. Furthermore, by thinning the semiconductor layer 10 in some areas and thickening the second semiconductor portion 10b in other areas, warping of the semiconductor layer 10 can be suppressed. Furthermore, for example, when the first conductive region 11a is thinner than the first semiconductor portion 10a or the second semiconductor portion 10b, the thickness of the lower electrode 11 can be suppressed, and warping of the semiconductor device can be suppressed.

[0056] 10(a) to 10(g) are schematic cross-sectional views illustrating the method for manufacturing the semiconductor device according to the embodiment. In the method for manufacturing the semiconductor device 100, a semiconductor wafer Wf is prepared as shown in Fig. 10(a). The semiconductor wafer Wf includes a semiconductor layer 10, a gate electrode pad G1, and a source electrode pad S1, similar to the examples in Figs. 1 to 5. Although not shown, the semiconductor wafer Wf also includes gate electrodes 41 and 42, gate insulating films 51 and 52, a gate electrode pad G2, and a source electrode pad S2, similar to the examples in Figs. 1 to 5. The semiconductor layer 10 includes a semiconductor region 21, base regions 22 and 24, and source regions 23 and 25.

[0057] 10(b), a tape TP is attached to the front surface F1 (upper surface) of the semiconductor wafer Wf. Then, as shown in FIG. 10(c), the back surface F2 of the semiconductor wafer Wf is ground to thin the semiconductor layer 10, and the tape TP is peeled off.

[0058] 10(d), a resist layer M is laminated on the back surface F2 side of the semiconductor wafer Wf. For example, the resist layer M is patterned by photolithography according to the pattern for forming the first semiconductor portion 10a.

[0059] Using the patterned resist layer M as a mask, the lower surface (rear surface F2) of the semiconductor layer 10 is etched (etching step). As a result, as shown in FIG. 10(e), a first semiconductor portion 10a and a second semiconductor portion 10b that is thicker than the first semiconductor portion 10a are formed in the semiconductor layer 10. At least a portion of the first semiconductor portion 10a is located below the source electrode pad S1 and the source electrode pad S2. Thereafter, the resist layer M is removed.

[0060] Thereafter, as shown in FIG. 10(f), a seed layer 11s is formed on the lower surface of the semiconductor layer 10 by sputtering. Thereafter, as shown in FIG. 10(g), a metal film 11t is formed on the lower surface of the seed layer 11s by, for example, plating (conductive layer formation process). This forms a lower electrode 11 on the lower surface side of the semiconductor layer 10. The lower electrode 11 includes a first conductive region 11a located below the first semiconductor portion 10a and a second conductive region 11b located below the second semiconductor portion 10b. The second conductive region 11b is thinner than the first conductive region 11a. Thereafter, if necessary, the semiconductor wafer Wf is diced into individual chips.

[0061] As described above, the semiconductor device 100 can be manufactured. In this example, the method of protecting the front surface of the semiconductor layer 10 with the tape TP and grinding the back surface is shown, but a method of using a hard material such as glass as a support substrate and peeling off the support substrate after forming the lower electrode can also be used. According to the embodiment, a semiconductor device and a method of manufacturing a semiconductor device that can suppress warpage while suppressing on-resistance can be provided.

[0062] Embodiments may include the following features. (Configuration 1) a first conductive layer including a first conductive region and a second conductive region having a thickness smaller than that of the first conductive region; a semiconductor layer disposed on the first conductive layer, a first semiconductor region of a first conductivity type; a second semiconductor region of a second conductivity type provided on a portion of the first semiconductor region; a third semiconductor region of the first conductivity type provided on the second semiconductor region; a fourth semiconductor region of the second conductivity type provided on another part of the first semiconductor region; a fifth semiconductor region of the first conductivity type provided on the fourth semiconductor region; a semiconductor layer comprising: a first control electrode facing the first semiconductor region, the second semiconductor region, and the third semiconductor region via a first insulating film; a second control electrode facing the first semiconductor region, the fourth semiconductor region, and the fifth semiconductor region via a second insulating film; a first electrode pad provided above the semiconductor layer and electrically connected to the third semiconductor region; a second electrode pad provided above the semiconductor layer and electrically connected to the fifth semiconductor region, a second electrode pad, at least a portion of the first conductive region being located below the first electrode pad and the second electrode pad; A semiconductor device comprising: (Configuration 2) 2. The semiconductor device according to claim 1, wherein the first conductive region is provided continuously from below the first electrode pad to below the second electrode pad. (Configuration 3) 3. The semiconductor device according to claim 1, wherein, in a plane perpendicular to a first direction extending from the first conductive layer to the semiconductor layer, the range in which the first conductive region is provided surrounds the first electrode pad and the second electrode pad. (Configuration 4) the semiconductor layer includes a first semiconductor portion provided on the first conductive region and a second semiconductor portion provided on the second conductive region; 4. The semiconductor device according to any one of configurations 1 to 3, wherein the first semiconductor portion has a thickness thinner than that of the second semiconductor portion. (Configuration 5) 5. The semiconductor device of claim 4, wherein the second conductive region has a thickness thinner than the second semiconductor portion. (Configuration 6) 6. The semiconductor device of claim 5, wherein the first semiconductor portion has a thickness thinner than the first conductive region. (Configuration 7) 7. The semiconductor device according to any one of configurations 1 to 6, wherein the second conductive region does not overlap with the first electrode pad and the second electrode pad in a first direction from the first conductive layer toward the semiconductor layer. (Configuration 8) a plurality of the first electrode pads are provided; a plurality of second electrode pads are provided; The semiconductor device according to any one of configurations 1 to 7, wherein the second conductive region is located below a region between one of the first electrode pads and another of the first electrode pads, and below a region between one of the second electrode pads and another of the second electrode pads. (Configuration 9) (Manufacturing method) a semiconductor layer including a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type provided on a portion of the first semiconductor region, a third semiconductor region of the first conductivity type provided on the second semiconductor region, a fourth semiconductor region of the second conductivity type provided on another portion of the first semiconductor region, and a fifth semiconductor region of the first conductivity type provided on the fourth semiconductor region; a first control electrode facing the first semiconductor region, the second semiconductor region, and the third semiconductor region via a first insulating film; a second control electrode facing the first semiconductor region, the fourth semiconductor region, and the fifth semiconductor region via a second insulating film; a first electrode pad provided above the semiconductor layer and electrically connected to the third semiconductor region; preparing a semiconductor wafer including a second electrode pad provided above the semiconductor layer and electrically connected to the fifth semiconductor region; an etching step of etching a lower surface side of the semiconductor layer to form a first semiconductor portion and a second semiconductor portion thicker than the first semiconductor portion in the semiconductor layer, wherein at least a portion of the first semiconductor portion is located below the first electrode pad and the second electrode pad; a conductive layer forming step of forming a first conductive layer on the lower surface side of the semiconductor layer, the first conductive layer including a first conductive region located below the first semiconductor portion and a second conductive region located below the second semiconductor portion and having a thickness thinner than that of the first conductive region; A method for manufacturing a semiconductor device comprising:

[0063] In each of the embodiments described above, the relative level of the impurity concentration between each semiconductor region can be confirmed using, for example, a scanning capacitance microscope (SCM). The carrier concentration in each semiconductor region can be considered to be equal to the concentration of activated impurities in each semiconductor region. Therefore, the relative level of the carrier concentration between each semiconductor region can also be confirmed using an SCM. The relative level of the impurity concentration between each semiconductor region can be considered to correspond to the relative level of the carrier concentration between each semiconductor region. The impurity concentration in each semiconductor region can also be measured using, for example, SIMS (secondary ion mass spectrometry).

[0064] When each region contains both an impurity that acts as a donor and an impurity that acts as an acceptor, the "impurity concentration" may refer to the net impurity concentration after these impurities cancel each other out.

[0065] In this specification, "electrically connected" includes not only connection through direct contact but also connection via other conductive members.

[0066] In this specification, "vertical" and "parallel" do not only mean strictly vertical and strictly parallel, but also include variations in the manufacturing process, and may mean substantially vertical and substantially parallel.

[0067] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. [Explanation of symbols]

[0068] 10 Semiconductor layer 10a First semiconductor part 10b Second semiconductor part 10d bottom surface 10p convex part 10q recess 11 Lower electrode 11a 1st conductive area 11b Second conductive region 11c conductive area 11d Bottom surface 11p convex part 11r recess 11s seed layer 11t metal membrane 11u top 21 Semiconductor area 22 Base Area 23 Source Region 24 Base Area 25 Source Region 41 gate electrode 42 gate electrode 51 Gate insulating film 52 Gate insulating film 55 Insulation section 56 Insulation section 61 Source electrode 62 Source electrode 70 Insulating layer 71 Passivation Layer 100~104 Semiconductor devices cp1, cp2 pathway F1 surface F2 back G1 gate electrode pad G2 gate electrode pad Q1 First element Q2 Second element R1 First element region R2 Second element region S1, S1a, S1b source electrode pads S2, S2a, S2b source electrode pads T1 Trench T10a Thickness T10b Thickness T11a Thickness T11b Thickness T2 Trench TP Tape Wf Semiconductor wafer

Claims

1. a first conductive layer having an uneven surface on at least one of its upper surface and lower surface, the first conductive layer including a first conductive region and a second conductive region having a thickness thinner than that of the first conductive region; a semiconductor layer provided on the first conductive layer, a first semiconductor region of a first conductivity type; a second semiconductor region of a second conductivity type provided on a portion of the first semiconductor region; a third semiconductor region of the first conductivity type provided on the second semiconductor region; a fourth semiconductor region of the second conductivity type provided on another part of the first semiconductor region; a fifth semiconductor region of the first conductivity type provided on the fourth semiconductor region; a semiconductor layer comprising: a first control electrode facing the first semiconductor region, the second semiconductor region, and the third semiconductor region via a first insulating film; a second control electrode facing the first semiconductor region, the fourth semiconductor region, and the fifth semiconductor region via a second insulating film; a first electrode pad provided above the semiconductor layer and electrically connected to the third semiconductor region; a second electrode pad provided above the semiconductor layer and electrically connected to the fifth semiconductor region, wherein at least a portion of the first conductive region is located below the first electrode pad and the second electrode pad; Equipped with the semiconductor layer includes a first semiconductor portion provided on the first conductive region and a second semiconductor portion provided on the second conductive region; The first semiconductor portion has a thickness thinner than the second semiconductor portion and thinner than the first conductive region.

2. 2. The semiconductor device according to claim 1, wherein said first conductive region is provided continuously from below said first electrode pad to below said second electrode pad.

3. A first conductive layer having an uneven surface on at least one of its upper and lower surfaces, the first conductive layer including a first conductive region and a second conductive region having a thickness thinner than that of the first conductive region; a semiconductor layer provided on the first conductive layer, a first semiconductor region of a first conductivity type; a second semiconductor region of a second conductivity type provided on a portion of the first semiconductor region; a third semiconductor region of the first conductivity type provided on the second semiconductor region; a fourth semiconductor region of the second conductivity type provided on another part of the first semiconductor region; a fifth semiconductor region of the first conductivity type provided on the fourth semiconductor region; a semiconductor layer comprising: a first control electrode facing the first semiconductor region, the second semiconductor region, and the third semiconductor region via a first insulating film; a second control electrode facing the first semiconductor region, the fourth semiconductor region, and the fifth semiconductor region via a second insulating film; a first electrode pad provided above the semiconductor layer and electrically connected to the third semiconductor region; a second electrode pad provided above the semiconductor layer and electrically connected to the fifth semiconductor region, wherein at least a portion of the first conductive region is located below the first electrode pad and the second electrode pad; Equipped with a first conductive region provided in a plane perpendicular to a first direction extending from the first conductive layer to the semiconductor layer, the first conductive region surrounding the first electrode pad and the second electrode pad;

4. The semiconductor device according to claim 1 , wherein said second conductive region has a thickness thinner than that of said second semiconductor portion.

5. A first conductive layer having an uneven surface on at least one of its upper and lower surfaces, the first conductive layer including a first conductive region and a second conductive region having a thickness thinner than that of the first conductive region; a semiconductor layer provided on the first conductive layer, a first semiconductor region of a first conductivity type; a second semiconductor region of a second conductivity type provided on a portion of the first semiconductor region; a third semiconductor region of the first conductivity type provided on the second semiconductor region; a fourth semiconductor region of the second conductivity type provided on another part of the first semiconductor region; a fifth semiconductor region of the first conductivity type provided on the fourth semiconductor region; a semiconductor layer comprising: a first control electrode facing the first semiconductor region, the second semiconductor region, and the third semiconductor region via a first insulating film; a second control electrode facing the first semiconductor region, the fourth semiconductor region, and the fifth semiconductor region via a second insulating film; a first electrode pad provided above the semiconductor layer and electrically connected to the third semiconductor region; a second electrode pad provided above the semiconductor layer and electrically connected to the fifth semiconductor region, wherein at least a portion of the first conductive region is located below the first electrode pad and the second electrode pad; Equipped with the second conductive region does not overlap the first electrode pad and the second electrode pad in a first direction from the first conductive layer toward the semiconductor layer.

6. a plurality of the first electrode pads are provided; a plurality of second electrode pads are provided; 2. The semiconductor device according to claim 1, wherein the second conductive region is located below a region between one of the first electrode pads and another of the first electrode pads, and below a region between one of the second electrode pads and another of the second electrode pads.

7. a semiconductor layer including: a first semiconductor region of a first conductivity type; a second semiconductor region of a second conductivity type provided on a portion of the first semiconductor region; a third semiconductor region of the first conductivity type provided on the second semiconductor region; a fourth semiconductor region of the second conductivity type provided on another portion of the first semiconductor region; and a fifth semiconductor region of the first conductivity type provided on the fourth semiconductor region; a first control electrode facing the first semiconductor region, the second semiconductor region, and the third semiconductor region via a first insulating film; a second control electrode facing the first semiconductor region, the fourth semiconductor region, and the fifth semiconductor region via a second insulating film; a first electrode pad provided above the semiconductor layer and electrically connected to the third semiconductor region; preparing a semiconductor wafer including a second electrode pad provided above the semiconductor layer and electrically connected to the fifth semiconductor region; an etching step of etching a lower surface side of the semiconductor layer to form a first semiconductor portion and a second semiconductor portion thicker than the first semiconductor portion in the semiconductor layer, wherein at least a portion of the first semiconductor portion is located below the first electrode pad and the second electrode pad; a conductive layer forming step of forming a first conductive layer on a lower surface side of the semiconductor layer, the first conductive layer including a first conductive region located below the first semiconductor portion and a second conductive region located below the second semiconductor portion and having a thickness thinner than the first conductive region, the first semiconductor portion having a thickness thinner than the first conductive region; A method for manufacturing a semiconductor device comprising:

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