Semiconductor device

Abstract

Provided is a highly reliable semiconductor device. A semiconductor device according to an embodiment comprises: pellets; a first conductor and a second conductor that sandwich the pellets in a first direction; a first joint material that joins the pellets and the first conductor; and a second joint material that joins the pellets and the second conductor, wherein a first surface of the first conductor facing the pellets has a plurality of projections overlapping with the pellets and a groove provided so as to surround the pellets when viewed in the first direction, a design value of the height of the plurality of projections is a first value, and the volume of the groove is based on the volume of a portion that is sandwiched between the pellets and the first conductor when a first height between the pellets and the first conductor is a second value that is greater than the first value.

Description

Semiconductor Devices

[0001] FIELD An embodiment of the present invention relates to a semiconductor device.

[0002] 2. Description of the Related Art A semiconductor device having a structure in which the upper and lower surfaces of a pellet are connected to conductors via a bonding material is known.

[0003] Japanese Patent Publication No. 2013-16603 Japanese Patent Publication No. 2012-104709 Japanese Patent Publication No. 2007-96042

[0004] A highly reliable semiconductor device is provided.

[0005] The semiconductor device of the embodiment comprises a pellet, a first conductor and a second conductor sandwiching the pellet in a first direction, a first bonding material bonding the pellet and the first conductor, and a second bonding material bonding the pellet and the second conductor, wherein a first surface of the first conductor facing the pellet has, when viewed in the first direction, a plurality of protrusions overlapping with the pellet and a groove arranged to surround the pellet, the design value of the height of the plurality of protrusions is a first value, and the volume of the groove is based on the volume of the portion sandwiched between the pellet and the first conductor when a first height between the pellet and the first conductor is a second value greater than the first value.

[0006] FIG. 1 is a perspective view showing an example of the appearance of a semiconductor device according to an embodiment. FIG. 2 is an exploded view showing an example of the internal structure of the semiconductor device according to an embodiment. FIG. 3 is a plan view showing an example of the planar layout of the semiconductor device according to an embodiment. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3, showing an example of the cross-sectional structure of the semiconductor device according to an embodiment. FIG. 5 is a plan view showing an example of the planar layout of a semiconductor device according to a first modified example. FIG. 6 is a plan view showing an example of the planar layout of a semiconductor device according to a second modified example. FIG. 7 is a plan view showing an example of the planar layout of a semiconductor device according to a third modified example. Embodiment

[0007] Hereinafter, embodiments will be described with reference to the drawings. The dimensions and proportions of the drawings are not necessarily the same as those in reality.

[0008] In the following description, components having substantially the same functions and configurations are denoted by the same reference numerals. When elements having similar configurations are to be particularly distinguished from one another, different letters or numbers may be added to the end of the same reference numerals.

[0009] 1. Embodiment A semiconductor device according to an embodiment will be described.

[0010] FIG. 1 is a perspective view showing an example of the appearance of a semiconductor device according to an embodiment. The semiconductor device 1 is an industrial power device. The semiconductor device 1 has, for example, a thin rectangular parallelepiped shape. Hereinafter, the thickness direction of the semiconductor device 1 will be referred to as the vertical direction or Z direction. Furthermore, when a component of the semiconductor device 1 has two surfaces that face each other in the vertical direction, these two surfaces will be referred to as the bottom surface and the top surface, respectively. Furthermore, two directions that are perpendicular to each other in a plane perpendicular to the Z direction will be referred to as the X direction and the Y direction.

[0011] The semiconductor device 1 includes a collector electrode 10, two emitter electrodes 20, two gate electrodes 30, and a sealing material 40. The collector electrode 10, the two emitter electrodes 20, and the two gate electrodes 30 each have a portion exposed to the outside of the sealing material 40 as a terminal for electrical connection with the outside.

[0012] The collector electrode 10 and the two emitter electrodes 20 are provided so as to be exposed on the lower and upper surfaces of the sealing material 40, respectively. For example, the exposed surface of the collector electrode 10 and the exposed surfaces of each of the two emitter electrodes 20 are flush with the lower and upper surfaces of the sealing material 40, respectively. When viewed in the thickness direction, the exposed surface of each of the two emitter electrodes 20 is included within the exposed surface of the collector electrode 10.

[0013] The two gate electrodes 30 are provided so as to be exposed to the side surfaces of the sealing material 40. For example, the two gate electrodes 30 protrude from the side surfaces of the sealing material 40.

[0014] The sealing material 40 is an insulating member that physically and electrically protects the internal structure of the semiconductor device 1 from the outside. The sealing material 40 forms the outer shape of the semiconductor device 1.

[0015] Fig. 2 is an exploded view showing an example of the internal structure of a semiconductor device according to an embodiment. Fig. 2 schematically shows the internal structure of the semiconductor device 1 exploded in the thickness direction. Note that the sealing material 40 is not shown in Fig. 2. The semiconductor device 1 further includes, as its internal structure, two bonding materials 50, two pellets 60, two bonding materials 70, and two wires 80 in addition to the collector electrode 10, two emitter electrodes 20, and two gate electrodes 30.

[0016] Each of the collector electrode 10 and the emitter electrode 20 is, for example, a copper plate having a thickness of about 1.5 mm. The lower surface of the collector electrode 10 corresponds to the surface of the collector electrode 10 exposed from the sealing material 40. The lower surface of the collector electrode 10 is, for example, flat over its entire surface. A more specific configuration of the collector electrode 10 will be described later. The upper surface of the emitter electrode 20 corresponds to the surface of the emitter electrode 20 exposed from the sealing material 40. The upper surface of the emitter electrode 20 is, for example, flat over its entire surface.

[0017] Two bonding materials 50 are provided spaced apart from each other on the upper surface of the collector electrode 10. The bonding materials 50 are, for example, plate-shaped solder. The bonding materials 50 are provided between the collector electrode 10 and the corresponding pellets 60.

[0018] The pellet 60 is a chip of a power semiconductor. Specifically, for example, the pellet 60 is an insulated gate bipolar transistor (IGBT) or a metal-oxide-silicon field-effect transistor (MOSFET) using silicon carbide (SiC). Note that if the pellet 60 is a MOSFET using SiC, the collector electrode 10 and the emitter electrode 20 are to be read as a drain electrode and a source electrode, respectively.

[0019] The lower surface of the pellet 60 is used as an electrode corresponding to the collector. The lower surface of the pellet 60 is electrically connected to the collector electrode 10 via the bonding material 50. The area of ​​the lower surface of the pellet 60 is smaller than that of the collector electrode 10. A pad corresponding to the emitter and a pad corresponding to the gate are provided on the upper surface of the pellet 60. The area of ​​the upper surface of the pellet 60 is larger than that of the emitter electrode 20.

[0020] A bonding material 70 is provided on the upper surface of the pellet 60 in an area including the pads corresponding to the emitters but excluding the pads corresponding to the gates. The bonding material 70 is, for example, a plate-shaped solder. A corresponding emitter electrode 20 is provided on the upper surface of the bonding material 70.

[0021] One end of a wire 80 is provided on a pad on the upper surface of the pellet 60 that corresponds to the gate. The wire 80 is a bonding wire. The other end of the wire 80 is connected to the corresponding gate electrode 30.

[0022] The two pellets 60 are arranged, for example, side by side in the Y direction.

[0023] With the above-described configuration, inside the semiconductor device 1, the three terminals used for input and output of the pellet 60 are electrically connected to the collector electrode 10, the emitter electrode 20, and the gate electrode 30. The bonding materials 50 and 70 are responsible for the electrical connection between the pellet 60 and the terminals, and also have the function of dissipating heat generated in the pellet 60 in the vertical direction.

[0024] 1 and 2, the case where two pellets 60 are provided in the semiconductor device 1 is described, but this is not limiting. The number of pellets 60 provided in the semiconductor device 1 may be one, or three or more.

[0025] Fig. 3 is a plan view showing an example of a planar layout of the semiconductor device according to the embodiment. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3, showing an example of a cross-sectional structure of the semiconductor device according to the embodiment. Note that the sealing material 40 is omitted from Figs. 3 and 4.

[0026] For example, four collector protrusions P corresponding to each pellet 60 are provided on the upper surface of the collector electrode 10. That is, if the semiconductor device 1 includes two pellets 60, eight collector protrusions P are provided on the upper surface of the collector electrode 10. The collector protrusion P corresponding to each pellet 60 is provided so as to overlap with the pellet 60 when viewed in the Z direction. With the above configuration, each pellet 60 can be in contact with the upper surfaces of the four collector protrusions P. Note that the number of collector protrusions P corresponding to each pellet 60 is not limited to four. The number of collector protrusions P corresponding to each pellet 60 may be three or more.

[0027] The height t1 of the collector protrusion P in the Z direction is, for example, 100 μm or more. The collector protrusions P in the collector electrode 10 vary, and the height t1 deviates from the design value. That is, the heights of the multiple collector protrusions P have values ​​greater than or equal to the minimum value and less than or equal to the maximum value. For example, if the design value of the height of the collector protrusions P is 150 μm and the height of the collector protrusions P varies by ±20 μm from the design value, the heights of the multiple collector protrusions P can be greater than or equal to 130 μm and less than or equal to 170 μm. Also, for example, if the design value is 200 μm and the height of the collector protrusions P varies by ±20 μm from the design value, the heights of the multiple collector protrusions P can be greater than or equal to 180 μm and less than or equal to 220 μm. The maximum and minimum height values ​​can be determined based on, for example, the design value and processing accuracy.

[0028] The bonding material 50 is provided so as to fill the space between each pellet 60 supported by the collector protrusion P and the upper surface of the collector electrode 10. As a result, the thickness of the bonding material 50 becomes, for example, 100 μm or more, similar to the height t1 of the collector protrusion P.

[0029] For example, two grooves G are provided in the upper part of the collector electrode 10. Each groove G is provided corresponding to a pellet 60. As a result, the two grooves G are provided so as to be aligned, for example, in the Y direction. The height of the upper surface of the collector electrode 10 excluding the collector protrusion P and the grooves G is, for example, approximately equal.

[0030] When viewed in the Z direction, each groove G is provided, for example, to surround a rectangular region R. The width in the Y direction of the portion of the groove G extending along the X direction (the portion of the groove G abutting the side of the region R extending in the X direction) and the width in the X direction of the portion of the groove G extending along the Y direction (the portion of the groove G abutting the side of the region R extending in the Y direction) are, for example, approximately equal. In the following description, the width in the Y direction of the portion of the groove G extending along the X direction and the width in the X direction of the portion of the groove G extending along the Y direction will also be simply referred to as the width of the groove G.

[0031] When viewed in the Z direction, the area of ​​each region R is larger than the area of ​​the bottom surface of the pellet 60. When viewed in the Z direction, the bottom surface of each pellet 60 is included in the region R associated with that pellet 60. At each of one end and the other end of the pellet 60 in the X direction, the width w1 between the pellet 60 and the groove G is, for example, about 200 μm. Although not shown, the width between the pellet 60 and the groove G at each of one end and the other end of the pellet 60 in the Y direction is also, for example, about 200 μm. With the above configuration, the collector protrusion P associated with each pellet 60 is provided within the region R associated with that pellet 60.

[0032] The groove G may contain a portion of the bonding material 50. The semiconductor device 1 having the above configuration is formed by filling the gap between the collector electrode 10 and the pellet 60 with the bonding material 50, filling the gap between the pellet 60 and the emitter electrode 20 with the bonding material 70, and then vertically pressing the assembly of components using a weight (not shown). As a result, in this process, a force acts on the bonding material 50, pushing it out from between the pellet 60 and the collector electrode 10. The amount of bonding material 50 used to fill the gap between the collector electrode 10 and the pellet 60 is set, for example, so as to fill the space between the collector electrode 10 and the pellet 60 when the height of all the collector protrusions P is the maximum height of the collector protrusions P. With the above-described forming method, excess bonding material 50 may flow out of the pellet 60 when viewed in the Z direction. The flowed-out portion of the bonding material 50 may then be contained within the groove G.

[0033] Taking into consideration the formation of the portion of the bonding material 50 that has flowed out as described above, the groove G is configured based on the volume of the portion sandwiched between the collector electrode 10 and the pellet 60 when the height of the collector protrusion P (and the height of the portion sandwiched between the collector electrode 10 and the pellet 60) is at its maximum. More specifically, the groove G is configured to have a volume equal to or greater than the volume obtained by subtracting the volume of the portion when the height of the collector protrusion P is at its design value from the volume of the portion when the height of the collector protrusion P is at its maximum value. In this configuration of the groove G, the volume of the groove G may be based on, for example, the average value or median value of the heights of a plurality of collector protrusions P, instead of the design value of the height of the collector protrusion P.

[0034] According to the embodiment, the upper portion of the collector electrode 10 includes a groove G provided outside the pellets 60 to surround the pellets 60 when viewed from above, and collector projections P provided to overlap the pellets 60. The volume of the groove G is based on the volume of the portion sandwiched between the collector electrode 10 and each pellet 60 when the height of the collector projections P is at its maximum. More specifically, the groove G is configured to have a volume equal to or greater than the volume of the sandwiched portion when the height of the collector projections P is at its maximum minus the volume of the sandwiched portion when the height of the collector projections P is at its reference value. With this configuration, even if solder flows out from between the collector electrode 10 and the pellets 60 when pressed vertically during the manufacturing process, it can be prevented from flowing out of the groove G. This prevents the solder from spreading excessively on the upper surface of the collector electrode 10. This prevents the solder that does not adhere to the sealing material 40 from spreading on the upper surface of the collector electrode, which would otherwise cause the sealing material 40 to peel off. Therefore, the deterioration of the reliability of the semiconductor device 1 can be suppressed.

[0035] 2 Modifications Next, a semiconductor device according to a modification will be described. In the following, differences between the configuration of the semiconductor device according to the modification and the configuration of the semiconductor device according to the embodiment will be mainly described. Explanations of configurations equivalent to those of the embodiment will be omitted as appropriate.

[0036] 2.1 First Modification The first modification differs from the embodiment in that the groove includes a portion that is wider than other portions when viewed in the Z direction.

[0037] Fig. 5 is a plan view showing an example of a planar layout of a semiconductor device according to a first modified example. Fig. 5 corresponds to Fig. 3. Note that the emitter electrode 20, the gate electrode 30, and the wire 80 are omitted from Fig. 5. Also, in Fig. 5, the region where the pellet 60 is provided is indicated by a dotted line.

[0038] In the semiconductor device 1a according to the first modification, a first portion of the collector electrode 10 provided on one side of the pellet 60 in the X direction has a width w2. The first portion is a portion between one end of the pellet 60 and the edge of one end of the collector electrode 10 in the X direction. A second portion of the collector electrode 10 provided on the other side of the pellet 60 in the X direction has a width w3. The second portion is a portion between the other end of the pellet 60 and the edge of the other end of the collector electrode 10 in the X direction. A third portion of the collector electrode 10 provided on one side of the one end pellet 60 of the two pellets 60 in the Y direction has a width w4. The third portion is a portion between one end of the one end pellet 60 and the edge of the one end of the collector electrode 10 in the Y direction. A fourth portion of the collector electrode 10 provided on the other side of the other end pellet 60 of the two pellets 60 in the Y direction has a width w5. The fourth portion is a portion in the Y direction between the other end of the pellet 60 on the other end side and the side on the other end side of the collector electrode 10. The widths w2 and w3 are, for example, wider than the widths w4 and w5.

[0039] The portion of the groove Ga extending along the Y direction includes, for example, a portion WPa that is wider than the other portions of the groove Ga. That is, the groove Ga includes the wide portion WPa in the first and second portions that are wider than the third and fourth portions. The width of the groove Ga in the other portions excluding the portion WPa is, for example, the same. Note that the example shown in FIG. 5 shows a case where each groove Ga has two portions WPa. However, this is not limited to this. The number of portions WPa that each groove Ga has can be one, or three or more.

[0040] In the above description, the first portion, the second portion, the third portion, and the fourth portion may be respectively a portion of the collector electrode 10 provided on one side of the region Ra inside the groove Ga in the X direction, a portion of the collector electrode 10 provided on the other side of the region Ra in the X direction, a portion of the collector electrode 10 provided on one side of the region Ra on one side of the two regions Ra in the Y direction, and a portion of the collector electrode 10 provided on the other side of the region Ra on the other side of the two regions Ra in the Y direction. In this case, the first part, the second part, the third part, and the fourth part are respectively the part in the X direction between the side of one end of the region Ra and the side of one end of the collector electrode 10, the part in the X direction between the side of the other end of the region Ra and the side of the other end of the collector electrode 10, the part in the Y direction between one end of the region Ra on the one end side and the side of one end of the collector electrode 10, and the part in the Y direction between the other end of the region Ra on the other end side and the side of the other end of the collector electrode 10.

[0041] The first modification also provides the same effects as the embodiment.

[0042] Furthermore, the groove Ga includes a wide portion WPa in the first and second portions, which are wider than the third and fourth portions. This makes it possible to ensure a portion of the collector electrode 10a that is bonded to the sealing material 40 in the region outside the groove Ga while suppressing an increase in the size of the semiconductor device 1a. Additionally, if the groove includes a wider portion than the other portions in the third and fourth portions, which are narrower than the first and second portions, it may be difficult to ensure a sufficient portion of the collector electrode that is bonded to the sealing material outside the groove. According to the first modification, the above-described configuration ensures a portion of the collector electrode that is bonded to the sealing material without increasing the size of the collector electrode and the semiconductor device.

[0043] 2.2 Second Modification The second modification differs from the embodiment in that the collector electrode has a non-wetted region.

[0044] Fig. 6 is a plan view showing an example of a planar layout of a semiconductor device according to a second modification. Fig. 6 corresponds to Fig. 3 and Fig. 5. Note that, similar to Fig. 5, the emitter electrode 20, the gate electrode 30, and the wire 80 are not shown in Fig. 6. Also, similar to Fig. 5, the region where the pellet 60 is provided is indicated by a dotted line in Fig. 6.

[0045] In the semiconductor device 1b according to the second modification, a non-wetting region NWb is provided in a region Rb inside the groove Gb in the collector electrode 10b. The non-wetting region NWb is a region where solder is difficult to flow and is difficult to apply. The non-wetting region NWb is formed by applying a resist or by performing an oxidation process using a laser, for example. The non-wetting region NWb is partially provided on the outer periphery of the region Rb inside the groove Gb. In the following description, the region in the region Rb where the non-wetting region NWb is not provided will be referred to as a wetting region Wb.

[0046] The wetting region Wb is provided so as to contact the groove Gb. In the example shown in Fig. 6, the wetting region Wb is provided so as to contact the portions of the groove Gb extending along the two X directions and the portions of the groove Gb extending along the two Y directions. Note that it is sufficient that a non-wetting region NWb and a wetting region Wb contacting the groove Gb are provided in the outer periphery of the region Rb inside the groove Gb, and the number of locations where the wetting region Wb contacts the groove Gb is not limited to four. The number of locations where the wetting region Wb contacts the groove Gb may be one to three, or five or more.

[0047] The second modification also provides the same effects as the embodiment.

[0048] Furthermore, according to the second modification, the non-wetted region NWb and the wetting region Wb contacting the groove Gb are provided on the outer periphery of the region Rb inside the groove Gb. This makes it possible to limit the location from which solder flows out when it flows out from between the collector electrode 10 and the pellet 60 during the manufacturing process. This makes it possible to prevent excessive solder from flowing out from between the collector electrode 10 and the pellet 60. This makes it possible to prevent the occurrence of solder shrinkage cavities (cracks, etc.).

[0049] 2.3 Third Modification The third modification differs from the first modification in that the collector electrode has a non-wetted region.

[0050] Fig. 7 is a plan view showing an example of a planar layout of a semiconductor device according to a third modification. Fig. 7 corresponds to Fig. 3, Fig. 5, and Fig. 6. Note that Fig. 7 omits the emitter electrode 20, the gate electrode 30, and the wire 80, as in Fig. 5 and Fig. 6. Also, in Fig. 7, the region where the pellet 60 is provided is indicated by a dotted line, as in Fig. 5 and Fig. 6.

[0051] In the semiconductor device 1c according to the third modification, the wide portion WPc of the groove Gc is provided in the first and second portions that are wider than the third and fourth portions, similar to the portion WPa of the groove Ga of the first modification. That is, the wide portion WPc is included in the portion of the groove Gc that extends along the Y direction.

[0052] Furthermore, in the semiconductor device 1c according to the third modification, similar to the non-wetting region NWb of the second modification, the non-wetting region NWc is partially provided on the outer periphery of the region Rc, inside the groove Gc. The wetting region Wc is provided so as to contact the groove Gc. In the third modification, the wetting region Wc is provided corresponding to the wide portion WPc. More specifically, each of the wetting regions Wc contacts the corresponding portion WPc. The length of each of the wetting regions Wc along the Y direction is, for example, shorter than the length of the corresponding wide portion WPc along the Y direction. When viewed in the X direction, each of the wetting regions Wc is provided so as to overlap the corresponding wide portion WPc. In the above configuration, the non-wetting region NWc is provided over the entire outer periphery of the region Rc, excluding the wetting region Wc contacting the portion WPc.

[0053] According to the third modification, the same effects as those of the embodiment, the first modification, and the second modification can be achieved.

[0054] Furthermore, according to the third modification, the wetting area Wc is provided so as to contact the corresponding wide portion WPc. As a result, when solder flows out from between the collector electrode 10 and the pellet 60 during the manufacturing process, the solder is likely to flow into the wide portion WPc through the area of ​​the wetting area Wc that contacts the groove Gc. This configuration also makes it possible to prevent the solder from flowing out of the groove Gc when the solder flows out from between the collector electrode 10 and the pellet 60 during the manufacturing process.

[0055] 3. Other Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

Claims

1. A semiconductor device comprising: a pellet; a first conductor and a second conductor sandwiching the pellet in a first direction; a first bonding material bonding the pellet and the first conductor; and a second bonding material bonding the pellet and the second conductor, wherein a first surface of the first conductor facing the pellet has a plurality of protrusions overlapping the pellet when viewed in the first direction, and a groove surrounding the pellet, wherein a design value of the height of the plurality of protrusions is a first value, and a volume of the groove is based on the volume of a portion sandwiched between the pellet and the first conductor when a first height between the pellet and the first conductor is a second value greater than the first value.

2. The semiconductor device according to claim 1, wherein the volume of the groove is equal to or greater than the volume of the sandwiched portion when the first height is the second value minus the volume of the sandwiched portion when the first height is the first value.

3. The semiconductor device according to claim 1, wherein the second value is a maximum value among the variations in height of the plurality of protrusions.

4. The semiconductor device according to claim 1, wherein the number of said projections is three or more.

5. A semiconductor device as claimed in any one of claims 1 to 4, wherein in the first conductor, a first portion outside the pellet has a first width, a second portion outside the pellet and different from the first portion has a second width narrower than the first width, and the groove includes a first groove portion in the first portion having a width wider than the width of the groove in the second portion.

6. A semiconductor device according to any one of claims 1 to 4, wherein, when viewed in the first direction, a non-wetted region is provided partially on the outer periphery of the first conductor in an area inside the groove, and a wetting region is provided in contact with the groove.

7. The semiconductor device according to claim 6, wherein the non-wetted region is a region where a resist is applied or where an oxidation process is performed.

8. The semiconductor device according to claim 5, wherein, when viewed in the first direction, a region inside the groove in the first conductor includes a non-wettable region partially provided on the outer periphery, and a wetting region in contact with the first groove portion.

9. The semiconductor device according to claim 8, wherein the non-wetting region is provided over the entire outer periphery except for the wetting region.

10. The semiconductor device according to claim 1, wherein the first bonding material and the second bonding material include solder.

11. The semiconductor device according to claim 1, wherein the pellet, the first bonding material, and the second bonding material are sealed with a sealing material, and the first conductor and the second conductor each have at least a portion exposed from the sealing material.

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