Semiconductor device and method for producing semiconductor device

Abstract

This semiconductor device comprises: a semiconductor element having a first electrode on one surface and a second electrode with an area larger than that of the first electrode on another surface; a first conductor electrically connected with the first electrode; a second conductor electrically connected with the second electrode; a sintered member for sinter bonding the first electrode and the first conductor, and the second electrode and the second conductor; and a pressure transmission member abutting a margin area of the one surface of the semiconductor element closer to the outer periphery than the connection surface with the first conductor. The pressure transmission member comprises a soft member abutting the margin area of the semiconductor element, and a hard member harder than the soft member.

Description

Semiconductor device and method for manufacturing the same

[0001] The present invention relates to a semiconductor device and a method for manufacturing a semiconductor device.

[0002]

[0003] Patent Literature 1 discloses a semiconductor device comprising: a substrate; a semiconductor chip mounted on the substrate and having a surface electrode and a back electrode opposite the surface electrode; a lead frame disposed opposite the surface electrode of the semiconductor chip; a first joint formed between the substrate and the back electrode of the semiconductor chip; and a second joint formed between the surface electrode of the semiconductor chip and the lead frame, wherein the lead frame has electrode portions connected to the surface electrodes via the second joint, bridge portions connecting the electrode portions, and a resin layer formed on upper surfaces of the electrode portions, the resin layer being formed on lower surfaces of the bridge portion and on portions of the lower surfaces of the electrode portions that are not joined to the surface electrodes.

[0003] Japanese Patent Application Laid-Open No. 2018-006492

[0004] The invention described in Patent Document 1 leaves room for improvement in terms of reliability of the semiconductor device.

[0005] A semiconductor device according to a first aspect of the present invention comprises a semiconductor element having a first electrode on one side and a second electrode on the other side having a larger area than the first electrode, a first conductor electrically connected to the first electrode, a second conductor electrically connected to the second electrode, a sintered member that sinter-bonds the first electrode to the first conductor, and the second electrode to the second conductor, and a pressure force transmission member that abuts a marginal area of ​​the one side of the semiconductor element that is outer than the connection surface with the first conductor, and the pressure force transmission member comprises a soft portion that abuts the marginal area of ​​the semiconductor element, and a hard portion that is harder than the soft member. A second aspect of the present invention provides a method for manufacturing a semiconductor device including a semiconductor element having, on one side thereof, a first electrode electrically connected to a first conductor, and on the other side opposite to the first side thereof, a second electrode having an area larger than that of the first electrode and electrically connected to a second conductor, the method comprising: an arrangement step of arranging sintered material between the first electrode and the first conductor, and between the second electrode and the second conductor; a fixing step of fixing a pressure transmission member to the first conductor, the pressure transmission member having a soft portion abutting a margin area on the one side of the semiconductor element that is outer than the connection surface with the first conductor, and a hard portion harder than the soft portion; and a joining step of joining the semiconductor element to the first conductor and the semiconductor element to the second conductor by sintering the sintered material while the semiconductor element is pressed toward the second conductor by the first conductor and the pressure transmission member; the order of the arrangement step and the fixing step can be reversed, and the joining step is performed after the arrangement step and the fixing step.

[0006] According to the present invention, the reliability of the semiconductor device can be improved.

[0007] Cross-sectional view of the semiconductor device Plan view of the semiconductor device Diagram showing the bonding process of the semiconductor device Diagram showing the bonding process of the semiconductor device Cross-sectional view of the semiconductor device in Modification 1 Cross-sectional view of the semiconductor device in Modification 2

[0008] -Embodiments- Hereinafter, embodiments of a semiconductor device and a method for manufacturing the semiconductor device will be described with reference to FIGS.

[0009] FIG. 1 is a cross-sectional view of a semiconductor device 1. In this embodiment, orthogonal X, Y, and Z axes are indicated in each figure to clearly indicate the correlation between the drawings. The semiconductor device 1 includes a semiconductor element 2 shown in the center of the figure, a first conductor 11, a second conductor 12, a control conductor 13, a pressure force transmission member 20, a first joint 31, a second joint 32, and a third joint 33. The pressure force transmission member 20 includes a hard portion 21 and a soft portion 22. The semiconductor device 1 is roughly shaped as follows: The semiconductor element 2 is sandwiched between the first conductor 11 and the second conductor 12 on both sides in the Z-axis direction, and the pressure force transmission member 20 is further disposed in the gap between the first conductor 11 and the semiconductor element 2. The pressure force transmission member 20 can also be called a "spacer" disposed between the first conductor 11 and the semiconductor element 2.

[0010] The first bonding portion 31, the second bonding portion 32, and the third bonding portion 33 are all sintered. Note that sintered bonding is also called "sintering bonding" or "sinter bonding." Hereinafter, the first bonding portion 31, the second bonding portion 32, and the third bonding portion 33 will also be collectively called "sintered members."

[0011] The semiconductor element 2 is substantially flat. The semiconductor element 2 has a first surface 2P on the positive side of the Z axis and a second surface 2N on the negative side of the Z axis. A first electrode 81 and a control electrode 83 are formed on the first surface 2P. A second electrode 82 is formed on the second surface 2N. The area of ​​the second electrode 82 is larger than the area of ​​the first electrode 81.

[0012] The first conductor 11 has a protrusion 11P that protrudes toward the semiconductor element 2. The surface of the protrusion 11P on the negative Z-axis side substantially matches the shape and area of ​​the first electrode 81 formed on the first surface 2P of the semiconductor element 2. The protrusion 11P of the first conductor 11 contacts the semiconductor element 2 via a first bonding portion 31. The first bonding portion 31 has the same shape as the protrusion 11P or a shape smaller than the protrusion 11P. The second conductor 12 contacts the second electrode 82 of the semiconductor element 2 via a second bonding portion 32. The shape of the second bonding portion 32 is the same as the shape of the semiconductor element 2 in the XY plane or a shape larger than the shape of the semiconductor element 2 in the XY plane. The first bonding portion 31 and the second bonding portion 32 are members that require pressure to be applied during bonding.

[0013] The pressure force transmission member 20 includes a hard portion 21 and a soft portion 22. Hereinafter, the hard portion 21 will also be referred to as the "hard member," and the soft portion 22 will also be referred to as the "soft member." A control conductor 13 electrically connected to a control electrode of the semiconductor element 2 is embedded inside the pressure force transmission member 20. The control conductor 13 contacts the semiconductor element 2 via a third joint 33. The pressure force transmission member 20 has a shape that covers the area of ​​the semiconductor element 2 that is not in contact with the first conductor 11 in the XY plane. The end face of the pressure force transmission member 20 on the positive side of the Z axis contacts the surface of the first conductor 11 on the negative side of the Z axis, not the protrusion 11P. Except for the third joint 33, the soft portion 22 is disposed closer to the semiconductor element 2 than the hard portion 21. In other words, the hard portion 21 does not contact the semiconductor element 2. The soft portion 22 is compressed during bonding. The thickness of the soft portion 22 when compressed is approximately the same as the thickness when a force equivalent to the bonding pressure of the first bonding portion 31 and the third bonding portion 33 is applied. By setting the thickness of the soft portion 22 in this way, it is possible to apply a uniform pressure to the entire surface of the semiconductor element 2.

[0014] The first conductor 11 and the second conductor 12 are made of a metal with high electrical conductivity and thermal conductivity, such as copper or aluminum. However, the first conductor 11 and the second conductor 12 may be an insulating substrate containing a metal such as copper or aluminum. A circuit may be formed on the first conductor 11, but this is not shown in the present embodiment. The control conductor 13 is made of a metal with high electrical conductivity and thermal conductivity, such as copper or aluminum.

[0015] The first bonding portion 31, the second bonding portion 32, and the third bonding portion 33 are bonding members that require sintering or pressure application. The first bonding portion 31, the second bonding portion 32, and the third bonding portion 33 are given different names because they are intended to be bonded to different objects, but two or more of them may have the same composition. The bonding members may be in a sheet or paste form before bonding. The hard portion 21 and the soft portion 22 of the pressure force transmission member 20 are made of insulating materials. For example, the hard portion 21 can be made of epoxy resin or fluororesin, and the soft portion 22 can be made of silicone or rubber. The Young's moduli of the hard portion 21 and the soft portion 22 are significantly different.

[0016] FIG. 2 is a plan view of the semiconductor device 1. However, in FIG. 2, the first conductor 11 is not shown, and only the innermost and outermost peripheries of the pressure force transmission member 20 are shown. The hatched area in the center of the figure is the first joint 31, and the outer periphery of the first joint 31 coincides with the innermost periphery 20-1 of the pressure force transmission member. The outer periphery in FIG. 2 is the outermost periphery 20-2 of the pressure force transmission member. The second joint 32 is shown as a narrow edge on the outer periphery of the semiconductor element 2. The third joint 33 is located at the end of the control conductor 13 in the negative X-axis direction. Although the third joint 33 would normally be hidden by the control conductor 13, in FIG. 2 it is depicted larger than it actually is in the X-axis and Y-axis directions to clearly show its position.

[0017] 3 and 4 are diagrams illustrating the bonding process of the semiconductor device 1. For ease of explanation, the process will be divided into steps 1 to 7 and explained in order below, but some steps may be performed together or the order in which they are performed may be changed.

[0018] In the first step, a pressure force transmission member 20 with a control conductor 13 embedded therein is prepared. In the second step, as shown in FIG. 3A, the pressure force transmission member 20 is attached to the first conductor 11. This attachment may be achieved, for example, by fitting, or by using an adhesive. The second step is also referred to as the "fixing step." In the third step, a sintered material that will become the second joint 32 is applied to the second conductor 12. The sintered material is a metal, such as silver, that can utilize the sintering phenomenon. The thickness of the applied material is the thickness of the paste relative to the predetermined joint thickness. Depending on the sintered material used, the sintered material is dried. In the fourth step, the semiconductor element 2 is placed on the sintered material that will become the second joint 32. Hereinafter, the third and fourth steps will be collectively referred to as the "placement step."

[0019] In the fifth step, as shown in FIG. 3(b), a sintered material that will become the first and third bonding portions 31 and 33 is applied to the semiconductor element 2. The application thickness is the thickness of the paste relative to the desired bonding thickness. Depending on the bonding material used, the sintered material is dried. The relationship between the thickness of the sintered material and the characteristics and thickness of the soft portion 22 is as follows. For example, assume that the thickness of the sintered material that will become the first bonding portion 31 is 100 μm when applied, 30 μm when bonded, and the bonding pressure is 20 MPa. In this case, the material and thickness of the soft portion 22 are selected so that a pressure of 20 MPa is applied when the sintered material is displaced by 70 μm. As mentioned above, because the Young's moduli of the soft portion 22 and the hard portion 21 are significantly different, the hard portion 21 is described here as having zero deformation. The order of steps 2 to 5 may be reversed. The sixth step, described below, is performed after steps 1 to 5.

[0020] In the sixth step, as shown in FIG. 4( a), the protrusion 11P is placed in contact with the first joint 31, and the control conductor 13 is placed in contact with the third joint 33. In the seventh step, which is performed after the sixth step, the semiconductor element 2 is sandwiched between the first conductor 11 and the second conductor 12 and pressurized and heated. This heating is necessary to sinter, i.e., sinter and bond, each joint. The seventh step is also referred to as the "bonding step." Through these steps, the first conductor 11, the second conductor 12, the semiconductor element 2, and the control conductor 13 are bonded via the first joint 31, the second joint 32, and the third joint 33, as shown in FIG. 4( b).

[0021] The above-described embodiment provides the following advantageous effects. (1) The semiconductor device 1 includes a semiconductor element 2 having a first electrode 81 on its first surface 2P and a second electrode 82 on its second surface 2N, the first electrode 81 being electrically connected to the first conductor 11, a second conductor 12 being electrically connected to the second electrode 82, a first joint 31, a second joint 32, and a third joint 33 that sinter-bond the first electrode 81 to the first conductor 11 and the second electrode 82 to the second conductor 12, and a pressure force transmission member 20 that abuts a marginal region of the first surface 2P of the semiconductor element 2 that is located on the outer periphery of the connection surface with the first conductor 11. The pressure force transmission member 20 includes a soft portion 22 that abuts the marginal region of the semiconductor element 2 and a hard portion 21 that is harder than the soft portion. This reduces damage to the semiconductor element 2 and poor bonding, improving the reliability of the semiconductor device 1. Specifically, the advantages are as follows.

[0022] Because the first electrode 81 has a smaller area than the second electrode 82, if only the electrode portions were pressed with a conductor, a greater pressure would be generated on the first electrode 81 than on the second electrode 82. However, in this embodiment, the pressure force transmission member 20 contacts a marginal area of ​​the first surface 2P that is closer to the outer periphery than the connection surface with the first conductor 11, allowing for a larger area of ​​pressure to be applied than the first electrode 81. Furthermore, the pressure force transmission member 20 has a hard portion 21 and a soft portion 22. When the thickness of the first joint portion 31 changes during joining, the soft portion 22 also displaces to apply pressure to the semiconductor element 2, thereby applying a uniform pressure to the second joint portion 32. Note that if the hard portion 21 is configured to contact the semiconductor element 2, the hard portion 21 is less likely to deform, and therefore may contact the semiconductor element 2 in a narrow area, such as a point. This is undesirable because a strong force would be generated locally on the semiconductor element 2 where the hard portion 21 contacts. Therefore, a configuration in which the soft portion 22 contacts the semiconductor element 2, as shown in this embodiment, is desirable.

[0023] (2) The semiconductor element 2 has a first electrode 81 and a control electrode 83 on the first surface 2P. The pressure force transmission member 20 holds the control conductor 13 that is electrically connected to the control electrode 83 of the semiconductor element 2. This eliminates the need for individual connection processes such as wire bonding.

[0024] (3) The control conductor 13 is embedded in the hard portion 21 and the soft portion 22 of the pressure force transmission member 20 .

[0025] (4) When the first bonding portion 31, which sinter-bonds the first electrode 81 and the first conductor 11, is compressed and deformed by a first displacement amount under a desired bonding pressure, the soft portion 22 is formed so that the displacement pressure when compressed and deformed by the first displacement amount is equal to the desired bonding pressure. Therefore, a uniform pressure can be applied to the entire surface of the second bonding portion 32.

[0026] (5) The semiconductor element 2 has a first electrode 81 electrically connected to the first conductor 11 on the first surface 2P, and a second electrode 82 on the second surface 2N, which has an area larger than that of the first electrode 81 and is electrically connected to the second conductor 12. A manufacturing method of a semiconductor device 1 including this semiconductor element 2 includes the following arrangement step, fixing step, and joining step. In the arrangement step, sintered materials that become the first joint portion 31 and the second joint portion 32 are arranged between the first electrode 81 and the first conductor 11, and between the second electrode 82 and the second conductor 12. In the fixing step, a pressure force transmission member 20 having a soft portion 22 abutting a marginal region of the first surface 2P of the semiconductor element 2 that is outer circumferentially closer to the connection surface with the first conductor 11, and a hard portion 21 harder than the soft portion 22, is fixed to the first conductor 11. In the joining process, the semiconductor element 2 is pressed toward the second conductor 12 by the first conductor 11 and the pressure transmission member 20, and the sintering material is sintered to join the semiconductor element 2 to the first conductor 11 and the semiconductor element 2 to the second conductor 12.

[0027] 5 is a cross-sectional view of a semiconductor device 1A according to Modification 1. In the above-described embodiment, the control conductors 13 connected to the control electrodes are embedded in the pressure force transmission member 20, but the control conductors 13 do not have to be embedded in the pressure force transmission member 20. In this case, the third joint portion 33 is also unnecessary.

[0028] 6 is a cross-sectional view of a semiconductor device 1B in Modification 2. In the embodiment described above, the soft portion 22 of the pressure force transmission member 20 contacts the semiconductor element 2 on the positive surface of the semiconductor element 2 on the Z axis. However, the soft portion 22 may be formed to extend outward beyond the outer periphery of the semiconductor element 2, and follow the shape of the outer edge of the semiconductor element 2. In this case, the soft portion 22 extends beyond the positive surface of the Z axis of the semiconductor element 2 on the negative side, i.e., downward in the figure, and contacts the semiconductor element 2 also in the X axis direction.

[0029] According to this modification 2, the following advantageous effects can be obtained: (6) The soft portion 22 is formed so as to extend outward from the outer periphery of the semiconductor element 2 and conforms to the outer edge shape of the semiconductor element 2. This increases the contact area with the semiconductor element 2, making it possible to prevent damage due to point contact.

[0030] REFERENCE SIGNS LIST 1: Semiconductor device 2: Semiconductor element 2P: First surface 2N: Second surface 11: First conductor 12: Second conductor 13: Control conductor 20: Pressure force transmission member 21: Hard portion 22: Soft portion 31: First joint portion 32: Second joint portion 33: Third joint portion

Claims

1. A semiconductor device comprising: a semiconductor element having a first electrode on one side and a second electrode on the other side having a larger area than the first electrode; a first conductor electrically connected to the first electrode; a second conductor electrically connected to the second electrode; a sintered member that sinters the first electrode to the first conductor, and the second electrode to the second conductor; and a pressure force transmission member that abuts against a marginal area on one side of the semiconductor element that is outer than the connection surface with the first conductor, wherein the pressure force transmission member comprises a soft member that abuts against the marginal area of ​​the semiconductor element, and a hard member that is harder than the soft member.

2. A semiconductor device according to claim 1, wherein the semiconductor element has the first electrode and a control electrode on the one surface, and the pressure transmission member holds a control conductor electrically connected to the control electrode of the semiconductor element.

3. A semiconductor device according to claim 2, wherein the control conductor is embedded in the hard member and the soft member of the pressure force transmission member.

4. A semiconductor device according to claim 1, wherein when the sintered member that sinter-bonds the first electrode and the first conductor is compressed and deformed by a first displacement amount with a desired bonding pressure, the soft member is formed so that the displacement pressure when compressed and deformed by the first displacement amount is equal to the desired bonding pressure.

5. A semiconductor device according to claim 1, wherein the soft member is formed so as to extend outward beyond the outer periphery of the semiconductor element, and follows the outer edge shape of the semiconductor element.

6. A method for manufacturing a semiconductor device including a semiconductor element having, on one surface thereof, a first electrode electrically connected to a first conductor, and, on the other surface opposite to the one surface, a second electrode larger in area than the first electrode and electrically connected to a second conductor, the method comprising: a positioning step of positioning a sintered material between the first electrode and the first conductor, and between the second electrode and the second conductor; a fixing step of fixing a pressure transmission member to the first conductor, the pressure transmission member having a soft portion abutting a marginal area on the one surface of the semiconductor element that is outer circumferentially closer to the connection surface with the first conductor, and a hard portion harder than the soft portion; and a joining step of joining the semiconductor element to the first conductor and the semiconductor element to the second conductor by sintering the sintered material while the semiconductor element is pressed toward the second conductor by the first conductor and the pressure transmission member, wherein the order of the positioning step and the fixing step can be reversed, and the joining step is carried out after the positioning step and the fixing step.

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