JP2018170344A - Semiconductor device and manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of securing a sufficient bonding area at the time of ultrasonic bonding in a semiconductor device. A semiconductor device (10) includes an insulating substrate (1), a semiconductor element, and an electrode terminal (2). A conductor pattern 1a is formed on the insulating substrate 1. The semiconductor element is arranged on the conductor pattern 1a. The electrode terminal 2 has a joint portion 2a that is joined so as to face the upper surface of the conductor pattern 1a. The thickness of the end portion of the joint portion 2a of the electrode terminal 2 in the facing surface direction is thicker than the thickness of the central portion. [Selection diagram] Fig. 1

Description

  The present invention relates to a technique for manufacturing a power semiconductor device by ultrasonically bonding electrode terminals to a conductor pattern formed on an insulating substrate.

  In a power semiconductor device represented by a power module using a power semiconductor element, an ultrasonic wave is used instead of solder bonding when bonding a conductor pattern formed on an insulating substrate and an electrode terminal to cope with a high temperature operation. Bonding may be used. Here, the ultrasonic bonding means that the bonded objects are metal-bonded by ultrasonically vibrating in the horizontal direction while pressing the ultrasonic bonding tool against the bonded object.

  For example, in Patent Document 1, as an apparatus for performing ultrasonic bonding, an ultrasonic bonding tool including a pressing surface that presses a bonding material and a material to be bonded at the time of bonding, and a plurality of protrusions formed on the pressing surface. An ultrasonic vibration bonding apparatus provided is disclosed.

JP 2013-226580 A

  However, when performing ultrasonic bonding, the ultrasonic vibration at the end of the ultrasonic bonding tool is weaker at the end than at the center, so the vibration direction of the ultrasonic bonding tool is Strictly not horizontally. Therefore, there is a problem that the end portion in the vibration direction at the joint portion of the electrode terminal, that is, the end portion at the joint portion of the electrode terminal is difficult to be joined.

  In the ultrasonic vibration bonding apparatus described in Patent Document 1, the tip of the protrusion at the center of the pressing surface of the ultrasonic bonding tool is located below the tip of the protrusion at the end of the pressing surface, and a plurality of protrusions The surface connecting the tips of the two has a convex shape. Therefore, it is difficult for ultrasonic vibration to be transmitted to the end portion in the vibration direction by the ultrasonic bonding tool. Furthermore, since the end portion at the joint portion of the electrode terminal is warped upward and the lower surface of the end portion of the joint portion is not in contact with the circuit pattern, the end portion at the joint portion of the electrode terminal is difficult to be joined. Therefore, the ultrasonic vibration bonding apparatus described in Patent Document 1 cannot solve the above problem.

  Accordingly, an object of the present invention is to provide a technique capable of ensuring a sufficient bonding area at the time of ultrasonic bonding in a semiconductor device.

  A semiconductor device according to the present invention includes an insulating substrate on which a conductor pattern is formed, a semiconductor element disposed on the conductor pattern, and an electrode terminal having a bonding portion that is bonded to the upper surface of the conductor pattern. The thickness of the edge part of the surface direction of the said opposing surface in the said junction part of the said electrode terminal is thicker than the thickness of a center part.

  According to the present invention, since the thickness of the end portion in the surface direction of the facing portion at the joint portion of the electrode terminal is thicker than the thickness of the center portion, when the electrode terminal is ultrasonically joined to the conductor pattern, vibration by the ultrasonic joining tool is performed. Ultrasonic vibration is easily transmitted to the end portion in the direction, and the bondability is improved. Thereby, a sufficient bonding area can be ensured at the time of ultrasonic bonding.

FIG. 3 is a schematic cross-sectional view of a bonding portion of an electrode terminal and its peripheral portion in the semiconductor device according to the first embodiment. It is a figure which shows the ideal vibration direction by an ultrasonic joining tool. It is a figure which shows the actual vibration direction by an ultrasonic joining tool. FIG. 10 is a schematic cross-sectional view of the electrode terminal bonding portion and its peripheral portion in the semiconductor device according to Modification 1 of Embodiment 1; FIG. 10 is a schematic cross-sectional view of electrode terminal joints and peripheral portions thereof in a semiconductor device according to Modification 2 of Embodiment 1; FIG. 10 is a perspective view of a joint portion of an electrode terminal and a peripheral portion thereof in a semiconductor device according to Modification 2 of Embodiment 1. FIG. 10 is an explanatory diagram for explaining the method for manufacturing the semiconductor device according to the second embodiment. FIG. 6 is a schematic side view of an ultrasonic bonding tool used in the method for manufacturing a semiconductor device according to the second embodiment and its peripheral part. It is the schematic diagram which looked at the ultrasonic bonding tool used with the manufacturing method of the semiconductor device concerning Embodiment 2 from the lower part. FIG. 11 is a schematic side view of an ultrasonic bonding tool used in the method for manufacturing a semiconductor device according to Modification 1 of Embodiment 2 and its peripheral part. FIG. 10 is a schematic view of an ultrasonic bonding tool used in a method for manufacturing a semiconductor device according to Modification 1 of Embodiment 2 as viewed from below. FIG. 10 is a schematic side view of an ultrasonic bonding tool used in the method for manufacturing a semiconductor device according to Modification 2 of Embodiment 2 and its peripheral part. FIG. 10 is a schematic view of an ultrasonic bonding tool used in a method for manufacturing a semiconductor device according to Modification 2 of Embodiment 2 as viewed from below.

<Embodiment 1>
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the joint 2a of the electrode terminal 2 and its peripheral portion in the semiconductor device according to the first embodiment. FIG. 2 is a diagram showing an ideal vibration direction by the ultrasonic bonding tool 4. FIG. 3 is a diagram illustrating an actual vibration direction by the ultrasonic bonding tool 4. In addition, the arrow in a figure has shown the vibration direction by the ultrasonic joining tool 4. FIG.

  As shown in FIG. 1, the semiconductor device includes an insulating substrate 1, a semiconductor element (not shown), and an electrode terminal 2. The insulating substrate 1 is made of ceramic or the like, and a plurality of conductive conductor patterns 1 a are provided on the upper surface of the insulating substrate 1. The electrode terminal 2 is bonded to the upper surface of the conductor pattern 1a of the insulating substrate 1 by ultrasonic bonding. The insulating substrate 1 is not limited to ceramic, and may be a substrate insulated by a resin, for example.

  Semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors) and FWDIs (Free Wheeling Diodes) are soldered to the upper surface of the conductor pattern 1a of the insulating substrate 1, and an aluminum wire is provided between the conductor pattern 1a and the conductor pattern 1a. Connected with. The insulating substrate 1, the semiconductor element, and the electrode terminal 2 are protected by a case (not shown) and a sealing material (not shown) such as gel.

  In place of the IGBT, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) may be arranged. Further, an SBD (Schottky diode) may be arranged instead of the FWDI.

  The die bonding material is not limited to solder, and may be a bonding material containing sinterable Ag or Cu particles. By using a sinterable bonding material, the conductive pattern 1a and the bonding pattern may be used. It is possible to improve the lifetime of the joint portion with the semiconductor element.

  The electrode terminal 2 includes a joint 2 a provided at one end of the electrode terminal 2. The joint portion 2 a is a portion that is joined facing the upper surface of the conductor pattern 1 a in the electrode terminal 2, and is a portion in which one end portion of the electrode terminal 2 is bent in parallel to the upper surface of the insulating substrate 1. The lower surface of the joint portion 2a is planar and is in contact with the conductor pattern 1a over the entire surface.

  Next, the shape of the upper surface of the joint portion 2a will be described. The thickness of the end portion of the joint portion 2a in the face direction is greater than the thickness of the central portion. More specifically, a curved portion 2b is provided on the upper surface of the joint portion 2a. The curved portion 2b has a curved shape in which the height position becomes higher from the center portion in the longitudinal direction of the joint portion 2a to the end portion in the width direction of the joint portion 2a. In addition, the upper surface of the junction part 2a is an opposite surface of the junction surface with the conductor pattern 1a of the junction part 2a. Further, the longitudinal direction of the joint portion 2a is the left-right direction with respect to the paper surface of FIG. 1, and the width direction of the joint portion 2a is the depth direction with respect to the paper surface of FIG.

  The reason why the curved portion 2b is provided on the upper surface of the joint portion 2a of the electrode terminal 2 will be described. As shown in FIG. 2, the ultrasonic bonding tool 4 includes a pressure surface 4 a at the tip portion facing the electrode terminal 2 and a plurality of protrusions 4 b provided on the pressure surface 4 a. In the first embodiment, it is assumed that the ultrasonic bonding tool 4 having a flat surface connecting the tips of the plurality of protrusions 4b is used.

  As shown in FIG. 2, it is ideal that the vibration direction by the ultrasonic welding tool 4 is a horizontal direction. Since the ultrasonic vibration is weaker than the central portion, the actual vibration direction by the ultrasonic bonding tool 4 is the direction shown in FIG. By making the thickness of the end portion in the surface direction of the joint portion 2a thicker than the thickness of the central portion, the ultrasonic vibration is easily transmitted to the end portion in the vibration direction by the ultrasonic bonding tool. The radius of the curved portion 2b of the joint portion 2a is preferably selected according to the magnitude of ultrasonic vibration.

  As described above, in the semiconductor device according to the first embodiment, the thickness of the end portion in the surface direction of the facing surface of the joint portion 2a of the electrode terminal 2 is thicker than the thickness of the central portion. More specifically, the upper surface, which is the opposite surface of the joint portion 2a to the conductor pattern 1a, has a curved shape. Therefore, when the electrode terminal 2 is ultrasonically bonded to the conductor pattern 1a, the ultrasonic vibration is easily transmitted to the end portion in the vibration direction by the ultrasonic bonding tool 4 and the bondability is improved. Thereby, a sufficient bonding area can be ensured at the time of ultrasonic bonding. Therefore, the yield of the semiconductor device can be improved.

  Moreover, it becomes possible to shorten joining time by improving joining property. By shortening the joining time, it is possible to suppress wear and deterioration of the tip portion of the ultrasonic joining tool 4 that contacts the electrode terminal 2, and to suppress damage to the conductor pattern 1a and the insulating substrate 1. As a result, it is possible to prevent insulation failure due to ceramic cracks in the insulating substrate 1 and improve the durability of the semiconductor device.

  Furthermore, ultrasonic bonding of the electrode terminals 2 is an effective technique in high-temperature operating environments. A semiconductor element is formed using a SiC (Silicon Carbide) material, and the area of the electrode terminals 2 is reduced to reduce the area of the package. Miniaturization is also possible.

  Next, a modification of the first embodiment will be described. FIG. 4 is a schematic cross-sectional view of the bonding portion 12a of the electrode terminal 12 and its peripheral portion in the semiconductor device according to the first modification of the first embodiment. FIG. 5 is a schematic cross-sectional view of the bonding portion 22a of the electrode terminal 22 and its peripheral portion in the semiconductor device according to the second modification of the first embodiment. FIG. 6 is a perspective view of the bonding portion 22a of the electrode terminal 22 and its peripheral portion in the semiconductor device according to the second modification of the first embodiment.

  As shown in FIG. 4, a concave portion 22 b formed in a concave shape in which a central portion in the longitudinal direction of the joint portion 22 a is recessed across the width direction of the joint portion 22 a is provided on the upper surface of the joint portion 22 a of the electrode terminal 22. May be. Also in this case, the same effect as in the first embodiment can be obtained.

  As shown in FIGS. 5 and 6, a mortar-shaped portion 32 b may be provided on the upper surface of the joint portion 32 a of the electrode terminal 32. The mortar-shaped part 32b is a curved shape in which the height position increases as it goes from the center part in the face direction of the joint part 32a to the end part. In other words, the thickness of the end portion in the surface direction of the facing surface of the joint portion 32a of the electrode terminal 32 is thicker than the thickness of the central portion.

  The ultrasonic bonding tool 4 is operated along the vibration direction of the ultrasonic bonding tool 4, and when there is a barrier such as a case on the operating range, the ultrasonic bonding tool 4 interferes with the barrier. Since the vibration direction by the ultrasonic bonding tool 4 is unidirectional, as in the curved portion 2b of the joint 2a of the electrode terminal 2 shown in FIG. When the thickness of the portion is increased, if the ultrasonic bonding tool 4 can only be vibrated by rotating 90 ° due to the relationship between the operating range of the ultrasonic bonding tool 4 and the barrier, the vibration direction of the ultrasonic bonding tool 4 Ultrasonic vibration is easily transmitted to the end portion, and the effect of improving the bondability cannot be obtained.

  However, as shown in FIGS. 5 and 6, by providing the mortar-shaped portion 22b on the upper surface of the joint portion 22a of the electrode terminal 22, the thickness of the end portions in all directions in the facing surface direction is increased. The same effect as in the first embodiment can be obtained regardless of the vibration direction.

  In addition, since it is necessary to provide a predetermined distance between the ultrasonic bonding tool 4 and the barrier due to the relationship between the operating range of the ultrasonic bonding tool 4 and the barrier, the package design of the semiconductor device is limited. However, as shown in FIGS. 5 and 6, by providing the mortar-shaped portion 22b on the upper surface of the joint portion 22a of the electrode terminal 22, the same effect as in the first embodiment can be obtained regardless of the vibration direction. The degree of freedom in designing the package of the semiconductor device is improved.

<Embodiment 2>
Next, a method for manufacturing the semiconductor device according to the second embodiment will be described. FIG. 7 is an explanatory diagram for explaining the method for manufacturing the semiconductor device according to the second embodiment. FIG. 8 is a schematic side view of the ultrasonic bonding tool 4 used in the method for manufacturing a semiconductor device according to the second embodiment. FIG. 9 is a schematic view of the ultrasonic bonding tool 4 used in the method for manufacturing a semiconductor device according to the second embodiment when viewed from below. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 7, the ultrasonic bonding apparatus ultrasonically bonds the electrode terminal 42 to the conductor pattern 1 a of the insulating substrate 1 by ultrasonically vibrating the electrode terminal 42 while applying a load with the ultrasonic bonding tool 44. . In FIG. 7, the shape of the tip portion of the ultrasonic bonding tool 44 and the shape of the upper surface of the bonding portion 42 a of the electrode terminal 42 are simplified.

  As shown in FIGS. 8 and 9, the ultrasonic bonding tool 44 includes a plurality of protrusions 44 b provided on the pressure surface 44 a at the tip portion facing the electrode terminal 42. The tip of the protrusion 44b at the end in the surface direction of the pressure surface 44a is located closer to the electrode terminal 42 than the tip of the protrusion 44b in the center in the surface direction of the pressure surface 44a. More specifically, the surface connecting the tips of the plurality of protrusions 44b is a portion facing the central portion from the portion facing the longitudinal end portion of the joint portion 42a across the width direction of the joint portion 42a of the electrode terminal 42. It is a curved shape where the height position increases as it goes to. In this way, by increasing the thickness of the portion of the tip of the ultrasonic bonding tool 44 that faces the end in the surface direction of the bonding portion 42a, the end of the ultrasonic bonding tool 44 in the vibration direction is also superfluous. Sound wave vibration is easily transmitted.

  In addition, the shape of the upper surface of the joint portion 42a of the electrode terminal 42 is adjusted in the longitudinal direction of the joint portion 42a across the width direction of the joint portion 42a of the electrode terminal 42 in accordance with the shape of the surface connecting the tips of the plurality of protrusions 44b. It is a curved shape in which the height position increases as it goes from the end to the center.

  As described above, in the method for manufacturing a semiconductor device according to the second embodiment, the ultrasonic bonding tool 44 includes the plurality of protrusions 44b provided on the pressing surface 44a of the tip portion facing the electrode terminal 42, and the pressing surface. The tip of the protrusion 44b at the end in the surface direction of 44a is positioned closer to the electrode terminal 42 than the tip of the protrusion 44b in the center in the surface direction of the pressing surface 44a. More specifically, the surface connecting the tips of the plurality of protrusions 44b has a curved shape. Therefore, the same effect as in the first embodiment can be obtained.

  Next, a modification of the second embodiment will be described. FIG. 10 is a schematic side view of an ultrasonic bonding tool 54 used in the method for manufacturing a semiconductor device according to the first modification of the second embodiment. FIG. 11 is a schematic view of the ultrasonic bonding tool 54 used in the method for manufacturing a semiconductor device according to the first modification of the second embodiment when viewed from below. FIG. 12 is a schematic side view of an ultrasonic bonding tool 64 used in the method for manufacturing a semiconductor device according to the second modification of the second embodiment. FIG. 13 is a schematic view of an ultrasonic bonding tool 64 used in the method for manufacturing a semiconductor device according to the second modification of the second embodiment when viewed from below.

  As shown in FIGS. 10 and 11, the surface connecting the tips of the plurality of protrusions 54 b is a recess in which the portion facing the central portion in the longitudinal direction of the joint portion 52 a extends in the width direction of the joint portion 52 a of the electrode terminal 52. It may be a shape. In this case, the shape of the upper surface of the joint portion 52a of the electrode terminal 52 is such that the central portion in the longitudinal direction of the joint portion 52a extends in the width direction of the joint portion 52a in accordance with the shape of the surface connecting the tips of the plurality of protrusions 54b. Protruding shape. Thereby, the same effect as in the second embodiment can be obtained.

  Also, as shown in FIGS. 12 and 13, the surface connecting the tips of the plurality of protrusions 64b is so high that it goes from the portion facing the end portion in the surface direction of the joint portion 62a to the portion facing the center portion. It may be in the shape of a mortar that increases in position. In this case, the shape of the upper surface of the joint portion 62a of the electrode terminal 62 is adjusted to the shape of the surface connecting the tips of the plurality of protrusions 64b, and the height increases from the end in the surface direction of the joint portion 62a toward the center portion. The shape is higher in position. Thereby, the same effect as in the second modification of the first embodiment can be obtained.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 Insulation board | substrate, 1a Conductor pattern, 2 Electrode terminal, 2a Joining part, 22 Electrode terminal, 22a Joining part, 32 Electrode terminal, 32a Joining part, 44 Ultrasonic joining tool, 44a Pressure surface, 44b Protrusion, 54 Ultrasonic joining tool , 54a pressure surface, 54b protrusion, 64 ultrasonic bonding tool, 64a pressure surface, 64b protrusion.

Claims (6)

An insulating substrate on which a conductor pattern is formed;
A semiconductor element disposed on the conductor pattern;
An electrode terminal having a joint portion that is joined facing the upper surface of the conductor pattern;
With
The thickness of the edge part of the surface direction of the said opposing surface in the said junction part of the said electrode terminal is a semiconductor device thicker than the thickness of a center part.   The semiconductor device according to claim 1, wherein an upper surface, which is a surface opposite to a bonding surface of the bonding portion with the conductor pattern, has a curved shape or a concave shape.   The semiconductor device according to claim 1, wherein an upper surface, which is a surface opposite to a bonding surface of the bonding portion with the conductor pattern, has a mortar shape. A method of manufacturing a semiconductor device by ultrasonically bonding an electrode terminal to a conductor pattern formed on an insulating substrate while applying a load with an ultrasonic bonding tool,
The ultrasonic bonding tool includes a plurality of protrusions provided on a pressure surface of a tip portion facing the electrode terminal,
The method of manufacturing a semiconductor device, wherein the tip of the protrusion at the end portion in the surface direction of the pressure surface is positioned closer to the electrode terminal than the tip of the protrusion in the center portion in the surface direction of the pressure surface.   The method of manufacturing a semiconductor device according to claim 4, wherein a surface connecting the tips of the plurality of protrusions has a curved shape or a concave shape.   The method for manufacturing a semiconductor device according to claim 4, wherein a surface connecting tips of the plurality of protrusions has a mortar shape.

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