JP2018046151A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an art to suppress a crack in an AlSi layer.SOLUTION: A semiconductor device has: a semiconductor substrate; a first AlSi layer at least partially covering a surface of the semiconductor substrate; a polyimide film partially covering a surface of the first AlSi layer; a second AlSi layer which at least partially covers a surface of the polyimide film and extends from above the polyimide film to the first AlSi layer within a range not covered with the polyimide film; and a nickel layer covering a range astride a surface of the first AlSi layer in the range not covered with the polyimide film and a surface of the second AlSi layer.SELECTED DRAWING: Figure 2

Description

  The technology disclosed in this specification relates to a semiconductor device.

  The semiconductor device disclosed in Patent Document 1 includes a semiconductor substrate, an AlSi layer, a polyimide film, and a nickel layer. The AlSi layer covers the surface of the semiconductor substrate. The polyimide film covers a part of the surface of the AlSi layer. The polyimide film is an insulating protective film provided on the surface of the semiconductor device. The nickel layer covers the surface of the AlSi layer in a range not covered with the polyimide film. The nickel layer is a layer for solder bonding. By joining the solder to the nickel layer, the solder and the AlSi layer are connected via the nickel layer. When a gap is generated between the nickel layer and the polyimide film due to a manufacturing error or the like, the AlSi layer is exposed in the gap and the reliability of the AlSi layer is lowered. Therefore, a part of the nickel layer runs on the polyimide film so that no gap is generated between the nickel layer and the polyimide film. Therefore, the end portion of the polyimide film is covered with the nickel layer.

Japanese Patent Laid-Open No. 2015-233035

  As the temperature of the semiconductor device rises, each member constituting the semiconductor device thermally expands. In the semiconductor device of Patent Document 1, the end portion of the polyimide film is a triple contact portion where the polyimide film, the AlSi layer, and the nickel layer are in contact with each other. Since the linear expansion coefficients of polyimide, AlSi, and nickel are different from each other, stress concentrates on the triple contact portion (that is, the end portion of the polyimide film) when the temperature of the semiconductor device rises. When high stress is repeatedly applied to the end of the polyimide film, cracks may occur in the AlSi layer around the end of the polyimide film. In this specification, the technique which suppresses the crack of an AlSi layer is provided.

  A semiconductor device disclosed in this specification includes a semiconductor substrate, a first AlSi layer covering at least a part of the surface of the semiconductor substrate, a polyimide film covering a part of the surface of the first AlSi layer, and a surface of the polyimide film A second AlSi layer extending from the polyimide film to the first AlSi layer in a range not covered by the polyimide film, and a first AlSi layer in a range not covered by the polyimide film. A nickel layer covering a surface and a range straddling the surface of the second AlSi layer;

  AlSi means an alloy containing aluminum (Al) and silicon (Si).

  In this semiconductor device, the second AlSi layer extends from the polyimide film to the first AlSi layer in a range not covered by the polyimide film. Therefore, the end portion of the polyimide film is covered with the second AlSi layer. Therefore, at the end of the polyimide film, AlSi constituting the first AlSi layer and the second AlSi layer and the polyimide constituting the polyimide film are in contact with each other. That is, two kinds of materials (AlSi and polyimide) are in contact with each other at the end of the polyimide film. Since the end portion of the polyimide film is not a triple contact portion, the stress generated at the end portion of the polyimide film is suppressed. For this reason, in this semiconductor device, cracks are unlikely to occur in the first AlSi layer and the second AlSi layer around the end of the polyimide film.

1 is a longitudinal sectional view of a semiconductor device according to an embodiment. FIG. 2 is an enlarged sectional view of a range II in FIG. Sectional drawing of the part corresponding to FIG. 2 of the conventional semiconductor device. Explanatory drawing of the manufacturing process of the semiconductor device of embodiment. Explanatory drawing of the manufacturing process of the semiconductor device of embodiment. Explanatory drawing of the manufacturing process of the semiconductor device of embodiment. Explanatory drawing of the manufacturing process of the semiconductor device of embodiment.

  The semiconductor device 10 of the embodiment shown in FIG. 1 has an upper electrode plate 12, a copper block 16, a semiconductor substrate 20, a lower electrode plate 24, and a resin layer 26. The semiconductor substrate 20 is mainly composed of silicon. Although not shown in FIG. 1, an electrode layer, an insulating protective film, and the like are provided on the upper surface of the semiconductor substrate 20. Although not shown in FIG. 1, an electrode layer is provided on the lower surface of the semiconductor substrate 20. The electrode layer provided on the lower surface of the semiconductor substrate 20 is connected to the upper surface of the lower electrode plate 24 via the solder layer 22. The electrode layer provided on the upper surface of the semiconductor substrate 20 is connected to the lower surface of the copper block 16 via the solder layer 18. The upper surface of the copper block 16 is connected to the upper electrode plate 12 via the solder layer 14. The upper electrode plate 12 and the lower electrode plate 24 function as electrode plates for energizing the semiconductor substrate 20 and also function as heat dissipation plates for radiating heat from the semiconductor substrate 20. The side surface of the laminate composed of the upper electrode plate 12, the copper block 16, the semiconductor substrate 20, and the lower electrode plate 24 is covered with a resin layer 26.

  FIG. 2 is an enlarged sectional view of a range II in FIG. In FIG. 2, the left side is the side close to the center of the semiconductor substrate 20, and the right side is the side close to the outer peripheral edge of the semiconductor substrate. Hereinafter, the side close to the center of the semiconductor substrate 20 (that is, the left side in FIG. 2) is referred to as the inner peripheral side, and the side close to the outer peripheral end of the semiconductor substrate (that is, the right side in FIG. 2) is referred to as the outer peripheral side.

  The upper surface of the semiconductor substrate 20 is covered with the first AlSi layer 30. The first AlSi layer 30 is made of AlSi (an alloy containing aluminum and silicon). The first AlSi layer 30 is electrically connected to the semiconductor substrate 20.

  A portion on the outer peripheral side of the upper surface of the first AlSi layer 30 is covered with a polyimide film 34. The inner peripheral portion of the upper surface of the first AlSi layer 30 is not covered with the polyimide film 34. On the first AlSi layer 30, an end 34a on the inner peripheral side of the polyimide film 34 exists. The polyimide film 34 is made of polyimide that is an insulator.

  A second AlSi layer 32 is disposed on the upper surface of the polyimide film 34. The second AlSi layer 32 is made of AlSi. The second AlSi layer 32 covers the inner peripheral portion of the upper surface of the polyimide film 34. The outer peripheral portion of the upper surface of the polyimide film 34 is not covered with the second AlSi layer 32. The second AlSi layer 32 extends from the polyimide film 34 to the first AlSi layer 30 in a range not covered by the polyimide film 34. The second AlSi layer 32 is connected to the first AlSi layer 30 in a range not covered with the polyimide film 34. The second AlSi layer 32 covers the end portion 34 a on the inner peripheral side of the polyimide film 34.

  A range straddling the upper surface of the second AlSi layer 32 and the upper surface of the first AlSi layer 30 in a range not covered by the polyimide film 34 is covered by the nickel layer 36. The upper surface of the nickel layer 36 is joined to the solder layer 18. The solder layer 18 is connected to the semiconductor substrate 20 via the nickel layer 36 and the first AlSi layer 30.

  The upper surface of the polyimide film 34 that is not covered by the second AlSi layer 32 (that is, the outer peripheral side portion of the upper surface of the polyimide film 34) is covered by the resin layer 26. The side surfaces of the solder layer 18, the nickel layer 36, and the second AlSi layer 32 are covered with the resin layer 26.

  FIG. 3 shows a cross section of a conventional semiconductor device. In FIG. 3, portions corresponding to the respective portions of the semiconductor device 10 of the embodiment are denoted by the same reference numerals as in FIG. 2. The conventional semiconductor device shown in FIG. 3 does not have the second AlSi layer 32. For this reason, the nickel layer 36 covers a range extending over the upper surface of the first AlSi layer 30 and the upper surface of the polyimide film 34 that is not covered by the polyimide film 34. Accordingly, the polyimide film 34, the nickel layer 36, and the first AlSi layer 30 are in contact with each other at the inner end 34 a of the polyimide film 34.

  The temperature of the semiconductor device rises when the semiconductor device is energized. In addition, the temperature of the semiconductor device may rise due to an external temperature rise. Below, the stress at the time of the temperature rise of a semiconductor device is demonstrated. First, the conventional semiconductor device shown in FIG. 3 will be described. In the conventional semiconductor device shown in FIG. 3, the polyimide film 34, the nickel layer 36, and the first AlSi layer 30 are in contact with each other at the end 34 a of the polyimide film 34. That is, at the end portion 34a, three kinds of materials of polyimide, nickel, and AlSi are in contact with each other. The linear expansion coefficients of polyimide, nickel and AlSi are different from each other. Therefore, a high thermal stress is generated at the end 34a where they are in contact with each other when the temperature of the semiconductor device rises. When high thermal stress is repeatedly applied to the end portion 34a, a crack occurs in the first AlSi layer 30 around the end portion 34a.

  On the other hand, in the semiconductor device 10 of the embodiment shown in FIG. 2, the end portion 34a of the polyimide film 34 is covered with the second AlSi layer 32, and the nickel layer 36 is not in contact with the end portion 34a. Since both the first AlSi layer 30 and the second AlSi layer 32 are made of AlSi, two kinds of materials of AlSi and polyimide are in contact with each other at the end 34a. Since the number of materials in contact with the end portion 34a is smaller than that of the conventional semiconductor device shown in FIG. Therefore, in the semiconductor device 10 of the embodiment, cracks are unlikely to occur in the first AlSi layer 30 and the second AlSi layer 32 around the end portion 34a.

  As described above, in the semiconductor device 10 of the embodiment, cracks in the AlSi layer around the end portion 34a of the polyimide film 34 can be suppressed.

  Next, a method for manufacturing the semiconductor device 10 according to the embodiment will be described. First, as shown in FIG. 4, a lower AlSi layer 31a is formed on the semiconductor substrate 20 by sputtering. Note that the stress applied to the AlSi layer can be reduced by making the lower AlSi layer 31a as thick as possible. For example, the thickness of the lower AlSi layer 31a can be 10 μm or more. Next, as shown in FIG. 5, a polyimide film 34 is formed on the outer peripheral portion of the lower AlSi layer 31a. A portion on the inner peripheral side of the lower AlSi layer 31 a is exposed without being covered with the polyimide film 34. Next, as shown in FIG. 6, the upper AlSi layer 31 b is formed by sputtering in a range straddling the upper surface of the lower AlSi layer 31 a and the upper surface of the polyimide film 34 in a range not covered with the polyimide film 34. The upper AlSi layer 31b is formed thinner than the lower AlSi layer 31a. As long as the polyimide film 34 does not exist, the upper AlSi layer 31b and the lower AlSi layer 31a are integrated. Thereby, the first AlSi layer 30 is formed. Further, the upper AlSi layer 31 b on the polyimide film 34 becomes the second AlSi layer 32. The portion on the outer peripheral side of the polyimide film 34 is exposed without being covered with the second AlSi layer 32. Next, as shown in FIG. 7, a nickel layer 36 is formed by sputtering in a range straddling the upper surface of the second AlSi layer 32 and the upper surface of the first AlSi layer 30 that is not covered by the polyimide film 34. The portion on the outer peripheral side of the polyimide film 34 is exposed without being covered with the nickel layer 36. Next, as shown in FIG. 1, the upper electrode plate 12, the copper block 16, the semiconductor substrate 20 and the lower electrode plate 24 are laminated via the solder layers 14, 18, and 22, and the laminated body is heated in a reflow furnace. . Then, the solder layers 14, 18, and 22 are once melted and then solidified. As a result, the upper electrode plate 12, the copper block 16, the semiconductor substrate 20, and the lower electrode plate 24 are joined together. The solder layer 18 is bonded to the nickel layer 36 as shown in FIG. After that, the semiconductor device 10 shown in FIG. 1 is completed by covering the periphery of the stacked body with the resin layer 26.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

10: Semiconductor device 12: Upper electrode plate 14: Solder layer 16: Copper block 18: Solder layer 20: Semiconductor substrate 22: Solder layer 24: Lower electrode plate 26: Resin layer 30: First AlSi layer 32: Second AlSi layer 34: Polyimide film 34a: end 36: nickel layer

Claims (1)

A semiconductor substrate;
A first AlSi layer covering at least part of the surface of the semiconductor substrate;
A polyimide film covering a part of the surface of the first AlSi layer;
A second AlSi layer covering at least a part of the surface of the polyimide film and extending from the polyimide film to the first AlSi layer in a range not covered by the polyimide film;
A nickel layer covering a range straddling the surface of the first AlSi layer in a range not covered by the polyimide film and the surface of the second AlSi layer;
A semiconductor device.

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