Method for manufacturing semiconductor device, and semiconductor device

Abstract

The invention provides a method for manufacturing a semiconductor device and a semiconductor device, which can increase the reliability of the semiconductor device while expanding a bonding material to a corner part of a bonded body and controlling the density of the bonding material. This method for manufacturing a semiconductor device is provided with: a step for supplying a paste-like bonding material onto a base material; and a step in which the joined body is placed on the joining material, the joining material is flattened by the joined body, and the joined body is joined to the base material by the joining material. The joined body is rectangular in plan view. The bonding material supplied onto the base material has: a central section positioned in the center of the body to be bonded; extension sections extending from the central section toward the respective apexes of the body to be bonded and having shapes corresponding to the angular shapes of the respective apexes of the body to be bonded; and retreated sections retreated from the respective sides of the body to be bonded. The distance between the upper end of the bonding material climbing toward the side surface of the bonded body and the upper surface of the bonded body is 40 [mu] m or more.

Description

Technical Field

[0001] The present disclosure relates to a method and structure for manufacturing a semiconductor device, and more particularly to a technique for bonding a bonded body such as a semiconductor chip to a base material such as a substrate using a paste-like bonding material. Background Art

[0002] In the manufacture of a conventional semiconductor device, when a semiconductor chip is bonded to a substrate, first, molten solder is supplied to the upper surface of the substrate or the solder is melted on the substrate, then the semiconductor chip is placed on the molten solder and the solder is pressed so that the solder wets and spreads over the entire lower surface of the semiconductor chip, and then the solder is solidified to bond the semiconductor chip to the substrate. When the solder is pressed with the semiconductor chip, the solder spreads in a concentric circle shape, so it is difficult for the solder to spread to the corners of the semiconductor chip, and thus poor solder wetting is likely to occur at the corners of the semiconductor chip.

[0003] For example, Patent Document 1 below discloses a technique in which a cross portion is provided below the center portion of a semiconductor chip on a substrate and solder is supplied in a cross shape extending toward four corners of the semiconductor chip, thereby making it easier for the solder to spread to the corners of the semiconductor chip.

[0004] In addition, as described in the following patent document 2, in the manufacture of a semiconductor device using a general sintered bonding material (hereinafter referred to as "sintered material"), a paste-like sintered material is supplied in the same shape as a semiconductor chip, and after the sintered material is dried, the semiconductor chip is placed on it, and the semiconductor chip is bonded to a substrate by pressurization and heating. Patent document 2 discloses a technology for controlling the sintering density of the sintered material.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-238647

[0006] Patent Document 2: Japanese Patent Application Publication No. 2014-29897

[0007] An object of the present invention is to achieve both expansion of the bonding material to the corners of a semiconductor chip and control of the sintering density.

[0008] In addition, if the bonding material is solder, even if the solder flattened by the semiconductor chip is exposed to the outside of the semiconductor chip, the shape of the solder will change due to surface tension, so the solder will not climb to the side of the semiconductor chip that is difficult to be wetted by the solder. However, in the case where the bonding material is a paste-like sintered material, the shape change caused by surface tension will not occur, so the sintered material will climb to the side of the semiconductor chip. In the case where the sintered material climbs to the side of the semiconductor chip, there will be problems such as increased leakage current and reduced reliability when implementing a high temperature and high humidity bias test (THB test) and the like. Summary of the invention

[0009] The present disclosure is made to solve the above-mentioned problems, and its purpose is to achieve both the extension of the bonding material to the corners of the bonded body and the control of the density of the bonding material when the bonded body is bonded to the base material using a paste-like bonding material, and to contribute to the improvement of the reliability of the semiconductor device.

[0010] The manufacturing method of the semiconductor device disclosed in the present invention comprises the following steps: a. a step of supplying a paste-like bonding material onto a base material; and b. a step of placing a body to be bonded on the bonding material, flattening the bonding material with the body to be bonded, and bonding the body to be bonded to the base material through the bonding material. The body to be bonded is rectangular when viewed from above. The bonding material supplied onto the base material in step a has, when the body to be bonded is placed on the bonding material, a central portion located at the center of the body to be bonded, an extending portion extending from the central portion toward each vertex of the body to be bonded and having a shape corresponding to the angular shape of each vertex of the body to be bonded, and a retreat portion retreating from each side of the body to be bonded. After step b, the distance between the upper end of the bonding material climbing toward the side of the body to be bonded and the upper surface of the body to be bonded is greater than 40 μm.

[0011] According to the present disclosure, when a bonded body is bonded to a base material using a paste-like bonding material, it is possible to achieve both expansion of the bonding material to the corners of the bonded body and control of the density of the bonding material, thereby contributing to improving the reliability of a semiconductor device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram showing a step of bonding a body to be bonded to a base material in the method for manufacturing a semiconductor device according to the embodiment.

[0013] Figure 2 It is a diagram showing a step of bonding a body to be bonded to a base material in the method for manufacturing a semiconductor device according to the embodiment.

[0014] Figure 3 It is a diagram showing a step of bonding a body to be bonded to a base material in the method for manufacturing a semiconductor device according to the embodiment.

[0015] Figure 4 It is a diagram showing a step of bonding a body to be bonded to a base material in the method for manufacturing a semiconductor device according to the embodiment.

[0016] Figure 5 The diagram shows an image of an observed object to be joined to a base material using the method for manufacturing a semiconductor device according to the embodiment.

[0017] Figure 6It means by Figure 5 FIG. 1 is a diagram of an enlarged image of the area enclosed by the four corners.

[0018] Figure 7 This is a diagram showing the results of observing the distance from the upper surface to the upper end of the bonding material in a semiconductor chip that failed in a THB test.

[0019] Figure 8 This is a diagram showing an image of the bonding material observed near the center of the bonded body.

[0020] Fig. 9 This is a diagram showing an image of the bonding material observed near the vertices of the bonded bodies.

[0021] Fig.10 This is a diagram showing an image of the bonding material observed near the side of the bonded body.

[0022] Explanation of reference numerals: 10 ... base material; 20 ... joining material; 21 ... central portion; 22 ... extension portion; 23 ... receding portion; 30 ... joined body; 40 ... collet. DETAILED DESCRIPTION

[0023] Figure 1 to Figure 4 1 is a diagram showing a step of bonding a bonded body 30 to a base material 10 in a method of manufacturing a semiconductor device according to an embodiment of the technology disclosed herein. Figure 1 to Figure 4 In each of the above, the top view is shown in the upper section, the cross-sectional view along the AA line of the top view is shown in the middle section, and the cross-sectional view along the BB line of the top view is shown in the lower section. Figure 4 An enlarged view of the end portion in the cross-sectional view along line AA is also shown.

[0024] First, if Figure 1 In this way, the paste-like bonding material 20 is supplied onto the base material 10. The base material 10 is, for example, an insulating substrate, a heat sink, etc., and has an area larger than the body to be bonded 30. The body to be bonded 30 is, for example, a semiconductor chip, an insulating substrate, and a terminal, and is rectangular in a plan view. The paste-like bonding material 20 is, for example, a non-melting bonding material such as a sintered material with a melting point of less than 400°C, a conductive adhesive, etc., which is made of a metal such as silver (Ag). The bonding material 20 is supplied to an area that is the same as or smaller than the external dimensions of the body to be bonded 30.

[0025] In this embodiment, the base material 10 is set as an insulating substrate, the body to be bonded 30 is set as a semiconductor chip, and the bonding material 20 is set as a sintered material composed of silver. In addition, the material of the semiconductor chip can be silicon or a wide bandgap semiconductor such as silicon carbide (SiC). Compared with the previous semiconductor devices using silicon, the semiconductor device formed using the wide bandgap semiconductor is excellent in operation under high voltage, high current and high temperature. As wide bandgap semiconductors, in addition to silicon carbide, there are also gallium nitride (GaN)-based materials, diamond, etc.

[0026] Next, if Figure 2 In this way, the object to be bonded 30 is adsorbed on the collet 40, and the position of the object to be bonded 30 is aligned on the bonding material 20. Figure 1 as well as Figure 2 As shown, the bonding material 20 supplied onto the base material 10 has, when the body to be bonded 30 is placed on the bonding material 20, a central portion 21 located in the center of the body to be bonded 30, an extending portion 22 extending from the central portion 21 toward each vertex (corner) of the body to be bonded 30 and having a shape corresponding to the angular shape of each vertex of the body to be bonded 30, and a receding portion 23 receding from each side of the body to be bonded 30.

[0027] Afterwards, if Figure 3 In this way, the body to be joined 30 is placed on the joining material 20, and the body to be joined 30 is pressed against the paste-like joining material 20 with a pressure of 0.05 MPa or less by the collet 40 to flatten the joining material 20. Figure 4 In this way, the bonding material 20 is pushed to the entire lower surface of the body 30 to be bonded. The pushed portion of the receding portion 23 of the bonding material 20 reaches each side of the rectangular body 30 to be bonded, and then the bonding material 20 that exceeds each side of the body 30 to be bonded climbs toward the side of the body 30 to be bonded. At this time, Figure 4 As shown in the enlarged view of the end of the body to be joined 30, the distance from the upper surface of the body to be joined 30 to the upper end of the bonding material 20 climbing up to the side of the body to be joined 30 is ensured to be 40 μm or more. In addition, the front end of the extended portion 22 of the bonding material 20 is aligned with the top of the body to be joined 30.

[0028] Then, by Figure 4 The body to be joined 30 and the base material 10 are joined via the joining material 20 by heating in a state of being heated. Since the joining material 20 is a non-melting joining material, the shape of the joining material 20 can be maintained even in the joining process based on heating. In addition, when the joining material 20 is a sintered material, unlike solder, the joining process based on heating can also be non-pressurized, that is, the pressurization is zero.

[0029] Figure 5is an image showing an observation of a body to be joined 30 joined to a base material 10 via a joining material 20. Figure 6 Is Figure 5 Although the bonding material 20 is extended until it is exposed from each side of the bonded body 30, the bonding material 20 exposed from each side climbs up to the side of the bonded body 30, so that Figure 5 Thus, when a plurality of the objects to be joined 30 are joined side by side, the interval between them can be narrowed to about 0.5 mm.

[0030] In addition, the extended bonding material 20 reaches the corner of the bonded body 30. However, the extended portion 22 of the bonding material 20 has its front end aligned with the top of the bonded body 30. Figure 6 In this way, the bonding material 20 is prevented from being exposed from the corners (portions indicated by arrows) of the bonded body 30. Since the bonding material 20 reaches the corners of the bonded body 30, stress concentration caused by thermal stress is reduced, and cracks in the bonding material 20 are prevented. In addition, the heat dissipation of the bonded body 30 can be improved.

[0031] A semiconductor device manufactured by the semiconductor device manufacturing method of the embodiment (the base material 10 is an insulating substrate, the bonded body 30 is a semiconductor chip, and the bonding material 20 is a sintered material composed of silver) was subjected to a THB test with a voltage of 2970V applied in an environment of a temperature of 90°C and a humidity of 90%. As a result, an undesirable condition of increased leakage current occurred 1000 hours after the start of the test. When observing the area around the discharge mark of the semiconductor chip with increased leakage current using an optical microscope (Hisomet (registered trademark)), as shown in FIG. Figure 7 In this way, it is confirmed that the distance from the upper surface of the semiconductor chip to the upper end of the bonding material that climbs up to the side of the semiconductor chip is less than 40 μm. On the other hand, when the distance from the upper surface of the semiconductor chip to the upper end of the bonding material is greater than 40 μm, the above-mentioned defect does not occur. Therefore, by ensuring that the distance from the upper surface of the semiconductor chip to the upper end of the bonding material is greater than 40 μm, it can help improve the reliability of the semiconductor device.

[0032] In particular, when the bonding material is a sintered material composed of silver (Ag), the rise of Ag to the side of the semiconductor chip has the disadvantage of inducing Ag electromigration. However, as in the present embodiment, by ensuring that the distance from the upper surface of the semiconductor chip to the upper end of the bonding material (Ag) is greater than 40 μm, the effect of avoiding the occurrence of Ag electromigration can also be obtained.

[0033] Here, the density of the bonding material 20 is described. When the paste-like bonding material 20 is spread, particles in the bonding material 20 collide with each other in the central portion 21 and the extended portion 22 of the bonding material 20, so that the bonding material 20 becomes dense. On the other hand, in the receding portion 23 of the extended portion 22, the bonding material 20 becomes sparse due to expansion into space.

[0034] exist Figure 8 to Figure 10 The image shows the state of the bonding material 20 after being sintered. Figure 8 This is an image of the portion where the central portion 21 of the bonding material 20 is pushed (near the central portion of the bonded body 30). Fig. 9 This is an image of the portion where the extended portion 22 of the bonding material 20 is extended (near the apex of the bonded body 30 ). Fig.10 23 of the bonding material 20 is pushed out (near the edge of the bonding body 30). Figure 8 ) and the extended portion 22 ( Fig. 9 ), the void ratio (the proportion of the void portion) is less than 10% (i.e., the density is more than 90%), whereas, in the portion where the receding portion 23 is extended, the void ratio is approximately 20% (i.e., the density is approximately 80%).

[0035] Since the void ratio of the bonding material 20 is distributed in this way, cracks in the bonding material 20, especially in the corners, are suppressed. In addition, when the bonded body 30 is a semiconductor chip, the density of the bonding material 20 is high near the center of the bonded body 30, which can help improve the heat dissipation of the semiconductor chip. In this way, in this embodiment, the density of the bonding material 20 can be controlled.

[0036] As described above, according to the method for manufacturing a semiconductor device of this embodiment, in the step of bonding the body to be bonded 30 to the base material 10 using the paste-like bonding material 20 , it is possible to achieve both extending the bonding material 20 to the corners of the body to be bonded 30 and controlling the density of the bonding material 20 .

[0037] Furthermore, the various embodiments may be freely combined, or may be appropriately modified or omitted.

[0038] <Note>

[0039] Hereinafter, various aspects of the present disclosure are collectively described as supplementary notes.

[0040] (Note 1)

[0041] A method for manufacturing a semiconductor device, comprising the following steps:

[0042] a. A step of supplying a paste-like bonding material to the base material; and

[0043] b. placing a body to be joined on the joining material, flattening the joining material with the body to be joined, and joining the body to be joined to the base material through the joining material,

[0044] The body to be joined is rectangular in plan view,

[0045] The bonding material supplied onto the base material in the step a has, when the body to be bonded is placed on the bonding material, a central portion located at the center of the body to be bonded, an extending portion extending from the central portion toward each vertex of the body to be bonded and having a shape corresponding to the angular shape of each vertex of the body to be bonded, and a retreat portion retreated from each side of the body to be bonded,

[0046] After the step b, the distance between the upper end of the bonding material climbing toward the side surface of the bonded body and the upper surface of the bonded body is 40 μm or more.

[0047] (Note 2)

[0048] The method for manufacturing a semiconductor device according to Supplement 1, wherein:

[0049] The bonding material is a non-melting bonding material.

[0050] (Note 3)

[0051] The method for manufacturing a semiconductor device according to Supplement 1 or 2, wherein:

[0052] In the step b, the extended portion of the receding portion of the bonding material reaches each side of the rectangular shape of the bonded body.

[0053] (Note 4)

[0054] The method for manufacturing a semiconductor device according to any one of Supplements 1 to 3, wherein:

[0055] In the bonding material after the step b, the void ratio of the portion where the receded portion is extended is higher than the void ratio of the central portion.

[0056] (Note 5)

[0057] A semiconductor device, wherein:

[0058] A rectangular body to be joined is joined to a base material via a joining material.

[0059] The bonding material is in contact with each vertex and each side of the bonded body, and the distance between the upper end of the bonding material climbing toward the side surface of the bonded body and the upper surface of the bonded body is 40 μm or more.

[0060] (Note 6)

[0061] The semiconductor device according to Supplementary Note 5, wherein:

[0062] The bonding material is a non-melting bonding material.

[0063] (Note 7)

[0064] The semiconductor device according to Supplementary Note 5 or 6, wherein:

[0065] In the bonding material, a void ratio near each side of the bonded body is higher than a void ratio near each vertex of the bonded body.

Claims

1. A method for manufacturing a semiconductor device, characterized in that: The following processes are available: a. A process of supplying a paste-like bonding material to a base material; and b. placing a body to be joined on the joining material, flattening the joining material with the body to be joined, and joining the body to be joined to the base material through the joining material, The body to be joined is rectangular in plan view, The bonding material supplied onto the base material in the step a has, when the body to be bonded is placed on the bonding material, a central portion located at the center of the body to be bonded, an extending portion extending from the central portion toward each vertex of the body to be bonded and having a shape corresponding to the angular shape of each vertex of the body to be bonded, and a retreat portion retreated from each side of the body to be bonded, After the step b, the distance between the upper end of the bonding material climbing toward the side surface of the bonded body and the upper surface of the bonded body is 40 μm or more.

2. The method for manufacturing a semiconductor device according to claim 1, wherein: The bonding material is a non-melting bonding material.

3. The method for manufacturing a semiconductor device according to claim 1 or 2, wherein: In the step b, the extended portion of the receding portion of the bonding material reaches each side of the rectangular shape of the bonded body.

4. The method for manufacturing a semiconductor device according to any one of claims 1 to 3, wherein: In the bonding material after the step b, the void ratio of the portion where the receded portion is extended is higher than the void ratio of the central portion.

5. A semiconductor device, characterized in that: A rectangular body to be joined is joined to a base material via a joining material. The bonding material is in contact with each vertex and each side of the bonded body, and the distance between the upper end of the bonding material climbing toward the side surface of the bonded body and the upper surface of the bonded body is 40 μm or more.

6. The semiconductor device according to claim 5, wherein: The bonding material is a non-melting bonding material.

7. The semiconductor device according to claim 5 or 6, characterized in that: In the bonding material, a void ratio near each side of the bonded body is higher than a void ratio near each vertex of the bonded body.

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