Sic filler, composite material, and semiconductor device

Abstract

To provide a SiC filler capable of further improving thermal conductivity, a composite material containing the SiC filler, and a semiconductor device using the composite material, in view of the fact that SiC has started to be widely mounted in society as a power semiconductor material capable of reducing power loss.SOLUTION: The composite material (10) containing the SiC filler (12) has a structure in which the SiC filler is dispersed in a continuous phase (11) composed of a metal or a synthetic resin. The SiC filler is composed of a dendritic crystal having a roundness of less than 0.206 in a cross-sectional view. The composite material containing the SiC filler can be used for a plate-shaped or layer-shaped bonded body to be bonded to a semiconductor element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a SiC filler, a composite material containing the SiC filler, and a semiconductor device using the composite material. [Background technology]

[0002] For example, composite materials of metals and non-metallic inorganic materials are sometimes used as heat dissipation materials for semiconductor elements. In this regard, Patent Document 1 discloses a composite material suitable for use as a heat dissipation material for semiconductor elements. The composite material described in Patent Document 1 is a composite of magnesium or a magnesium alloy and SiC, and contains, for example, more than 70 volume % SiC, has a thermal expansion coefficient of 4 ppm / K or more and 8 ppm / K or less, and has a thermal conductivity of 180 W / m·K or more. This composite material has excellent thermal expansion coefficient matching with semiconductor elements and also has excellent heat dissipation properties, making it suitable for use as a heat dissipation material for semiconductor elements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-80145 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, SiC has begun to be widely used as a power semiconductor material that can reduce power loss. Compared to the existing material Si, SiC has higher thermal conductivity and breakdown field strength, allowing for high-temperature operation. As a result, SiC device mounting products will be used in environments with higher loads. Durability against temperature cycles is particularly required. Furthermore, mounting materials that come into contact with SiC semiconductor devices must have a small difference in thermal expansion coefficient and high thermal conductivity.

[0005] The present disclosure has been made in view of the circumstances exemplified above, etc. That is, the present disclosure provides, for example, a SiC filler capable of further improving thermal conductivity, a composite material containing the SiC filler, and a semiconductor device using the composite material. [Means for solving the problem]

[0006] In one aspect of the present disclosure, the SiC filler (12) is made of dendrites having a circularity of less than 0.206 in a cross-sectional view. In another aspect of the present disclosure, the composite material (10) has a structure in which the SiC filler is dispersed in a continuous phase (11) made of metal or synthetic resin. In yet another aspect of the present disclosure, a semiconductor device (20) includes: A semiconductor element (21), a bonded body (23, 24) formed in the shape of a plate or layer and bonded to the semiconductor element; It is equipped with:

[0007] In addition, in each section of the application documents, each element may be assigned a reference symbol in parentheses. In this case, the reference symbol merely indicates an example of the correspondence between the element and the specific configuration described in the embodiment described below. Therefore, the present disclosure is not limited in any way by the description of the reference symbol. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of the configuration of a composite material containing a SiC filler according to the present disclosure. [Figure 2] 2 is an optical microscope photograph showing an enlarged view of the SiC filler shown in FIG. 1. [Figure 3] 3 is a graph showing the particle size distribution after dry classification of the SiC filler shown in FIG. 2. [Figure 4] 3 is a table showing the evaluation results of the specific surface area after dry classification of the SiC filler shown in FIG. 2. [Figure 5]1 is a photograph showing a scanning electron microscope image of a cross section of a synthetic resin in which the SiC filler according to the present embodiment is dispersed, and a binarized image of one SiC filler in the image. [Figure 6] 1 is a photograph showing a scanning electron microscope image of a cross section of a synthetic resin in which a commercially available filler is dispersed as a comparative example, and a binarized image of one filler in the image. [Figure 7] 7 is a table showing evaluation results of the roundness of the fillers shown in FIGS. 5 and 6. [Figure 8] FIG. 2 is a cross-sectional view schematically illustrating another example of the configuration of a composite material containing a SiC filler according to the present disclosure. [Figure 9] 1 is a cross-sectional view showing an example of the configuration of a semiconductor device using a composite material according to an embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing another example of the configuration of a semiconductor device using the composite material according to the present embodiment. [Figure 11] FIG. 10 is a cross-sectional view showing yet another configuration example of a semiconductor device using the composite material according to the present embodiment. [Figure 12] FIG. 10 is a cross-sectional view showing yet another configuration example of a semiconductor device using the composite material according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Embodiment) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings as appropriate. Note that the following embodiments, their modifications, and the drawings related thereto are schematic or simplified for the purpose of concisely explaining the contents of the present disclosure, and are not intended to limit the contents of the present disclosure in any way. Therefore, it goes without saying that the descriptions in the drawings do not necessarily coincide with the specific device configurations actually manufactured and sold. In other words, unless expressly limited by the applicant in the prosecution history of this application, it goes without saying that the present disclosure should not be interpreted as being limited by the descriptions in the drawings and the corresponding descriptions of the configurations, functions, or operations described below.

[0010] (SiC filler and composites containing it) As mentioned above, the mounting material in contact with the SiC semiconductor element needs to have a small difference in thermal expansion coefficient and high thermal conductivity. In this regard, Patent Document 1 proposes a composite member made by combining magnesium or a magnesium alloy with SiC that has the following characteristics (1) or (2), thereby realizing a composite material with a low thermal expansion coefficient and high thermal conductivity. (1) Contains more than 70% by volume of SiC. (2) It contains 50% or more by volume of SiC and has a network portion that connects the SiC particles together.

[0011] Basically, the higher the SiC filler content, the smaller the thermal expansion coefficient and the higher the thermal conductivity. However, most of these composite materials only have a thermal conductivity of about half of 490 W / mK, which is the inherent thermal conductivity of SiC. In Patent Document 1, the highest thermal conductivity is 318 W / mK when the SiC content is 85.7 volume % and the network thickness is large.

[0012] In this regard, when the filler shape, as represented by the aspect ratio, is distorted, the filler particles are expected to have more contact with each other, thereby improving thermal conductivity. Therefore, there is a demand for fillers with distorted shapes that can further improve thermal conductivity.

[0013] Therefore, this embodiment makes it possible to further improve thermal conductivity while maintaining a low thermal expansion coefficient. Specifically, referring to FIG. 1 , a composite material 10 according to this embodiment has a structure in which SiC fillers 12 are dispersed in a continuous phase 11 made of metal or synthetic resin. Hereinafter, the continuous phase 11 may be referred to as the "main phase." The SiC filler 12 includes powder particles made of dendrites having a circularity of less than 0.206 in a cross-sectional view. The diameter of these powder particles is 10 to 100 μm. The diameter of the SiC filler 12 refers to the median diameter. The SiC filler 12 has a crystal polymorphism of any one of 3C, 4H, 6H, and 15R, or a combination of two or more of these. The average circularity of the SiC filler 12 is 0.20 or less.

[0014] As a result of extensive research by the inventors, it was found that dendritic growth occurs when SiC is grown by CVD in a system with a small thermal gradient in the crystal growth region. An optical microscope photograph of a group of SiC filler particles 12 obtained by dendritic growth is shown in FIG. 2. The dendritic crystal growth method is, for example, as follows: A Si and C source gas and a carrier gas are used, a source gas decomposition region is at 1500 to 3000°C, the dendritic crystal precipitation region is at 2500°C or less, and the temperature gradient of the precipitation region relative to the growth axis direction is 5°C / mm or less. The source gas is SiH4, trichlorosilane, or C3H8. The carrier gas is H2 or Ar. The dendritic crystal precipitation region is a graphite member.

[0015] The obtained dendritic particles were classified, and the surface area, which is one of the indicators of shape distortion, was evaluated. The results are shown in Figures 3 and 4. From the results in Figure 3, the median diameter of the classified particles was 36.3 μm. The specific surface area of ​​a SiC simple sphere with a diameter of 36.3 μm is 0.05 m. 2 / g.

[0016] where: (Surface area ratio) = (specific surface area of ​​classified particles) / (specific surface area of ​​a simple sphere of median diameter of classified particles) In this case, the numerator is 0.74m from Figure 4. 2 / g, and the denominator value is 0.05m as above. 2 / g, the surface area ratio is 14.3. That is, the SiC filler 12 according to this embodiment has a surface area 14.3 times that of a simple sphere, and is therefore found to be a particle with a very distorted shape.

[0017] The evaluation results of the circularity of the SiC filler 12 according to this embodiment in a cross-sectional view will be described with reference to Figs. 5 to 7. The circularity is expressed by the following formula. The circularity is an index in which a perfect circle is 1, and the smaller the value, the more deformed the shape is. (Circularity) = 4π (area) / (perimeter)

[0018] G1 in FIG. 5 is a scanning electron microscope image of a cross section of a synthetic resin dispersion of SiC filler 12 according to this embodiment, in which 20 particles with relatively clear particle shapes are selected as particles of interest and shown as Nos. 1 to 20. G2 in FIG. 5 shows a binarized image of each of the particles of interest Nos. 1 to 20. FIG. 6 shows a commercially available crushed filler as a comparative example, in the same manner as FIG. 5. FIG. 7 is a table showing the calculation results of the circularity of each of the particles of interest Nos. 1 to 20 shown in FIGS. 5 and 6, as well as the maximum, minimum, and average values ​​of the circularity.

[0019] The circularity of the SiC filler 12 according to this embodiment is smaller than that of the commercially available crushed filler, so the shape is distorted and the surface area is large. Also, the minimum circularity of the commercially available crushed filler is 0.206, while the average circularity of the SiC filler 12 according to this embodiment is lower, at 0.150.

[0020] As described above, the SiC filler 12 according to this embodiment is composed of dendrites having a circularity of less than 0.206. The average circularity of the SiC filler 12 may be 0.20 or less. Furthermore, from the viewpoint of reducing the difference in thermal expansion coefficients and improving thermal conductivity, it may be 0.15 or less. The average circularity is determined by selecting 20 particles from a scanning electron microscope image of a cross section of a composite in which the SiC filler 12 is dispersed in a synthetic resin, calculating the circularity of each of the 20 particles, and averaging the circularity of the 20 particles. The composite material 10 according to this embodiment has a structure in which the SiC filler 12 is dispersed in a continuous phase 11 made of metal or synthetic resin. This allows the composite material 10, when used as a mounting material in contact with a SiC semiconductor element, to improve thermal conductivity while minimizing the difference in thermal expansion coefficients.

[0021] As shown in FIG. 8, the composite material 10 may further contain an additional filler 13 different from the SiC filler 12 having the above-described characteristics. The different additional filler 13 may be a filler made of a material different from SiC. The additional filler 13 may be any one of diamond, AlN, Si, and carbon (e.g., carbon nanotubes), or a combination thereof. This improves the filling rate, thereby further improving the thermal conductivity. The shape of the additional filler 13 is not particularly limited, and may be, for example, spherical, polyhedral, or amorphous.

[0022] (Semiconductor Devices) An example of the configuration of a semiconductor device 20 using the composite material 10 containing the SiC filler 12 according to this embodiment as described above will be described below with reference to Fig. 9 etc. Note that in Fig. 9 etc., the up-down direction in the drawing is merely for convenience of illustration and does not necessarily coincide with the direction of gravity.

[0023] 9, the semiconductor device 20 includes a semiconductor element 21, a heat sink 22, a first bonding body 23, and a second bonding body 24. That is, the semiconductor device 20 has a configuration as a bonding body of the semiconductor element 21, the heat sink 22, the first bonding body 23, and the second bonding body 24.

[0024] The semiconductor element 21 has a configuration as a SiC semiconductor element. The heat sink 22 is a so-called heat sink for cooling the semiconductor element 21, and is formed of a metal with high thermal conductivity, such as aluminum. The first bonding body 23 is provided between the bottom surface of the semiconductor element 21 and the top surface of the heat sink 22. The first bonding body 23 is a composite material 10 formed in a plate or layer shape with a metal as the main phase, and is bonded to the semiconductor element 21 and the heat sink 22. The second bonding body 24 is a composite material 10 formed in a plate or layer shape with a metal as the main phase, and is bonded to the top surface of the semiconductor element 21.

[0025] In such a configuration, the first bonding body 23 formed from the composite material 10 according to this embodiment can effectively promote heat dissipation from the semiconductor element 21 to the heat sink 22. Furthermore, the second bonding body 24 formed from the composite material 10 according to this embodiment can effectively promote heat dissipation from the semiconductor element 21 to the outside air.

[0026] 10 shows a configuration in which an insulating package 25 that covers the semiconductor element 21, the first bonded body 23, and the second bonded body 24 is added to the configuration shown in FIG. 9. Here, the insulating package 25 can be formed from a composite material 10 whose main phase is a synthetic resin. This can further promote heat dissipation from the semiconductor element 21 to the outside air.

[0027] Fig. 11 shows an example in which the heat sink 22 is formed of a composite material 10 containing a metal as a main phase in the configuration shown in Fig. 9, thereby omitting the first bonding body 23. With this configuration, the same effects as those of the configuration shown in Fig. 9 can be achieved.

[0028] FIG. 12 shows a configuration in which a cooling device 26 is added to the configuration shown in FIG. 10. The cooling device 26 is joined to the heat sink 22 via a TIM material 27. TIM is an abbreviation for Thermal Interface Material. The cooling device 26 is configured to radiate heat absorbed from the heat sink 22 to the outside by, for example, passing a refrigerant such as cooling water through the inside of the cooling device 26. Here, by forming the TIM material 27 using a composite material 10 having a metal as the main phase, the cooling efficiency of the cooling device 26 for the heat sink 22 is improved.

[0029] (Variation) The present disclosure is not limited to the above-described embodiment. Therefore, the above-described embodiment can be modified as appropriate. Representative modifications will be described below. In the following description of the modifications, differences from the above-described embodiment will be mainly described. Furthermore, the same reference numerals are used for parts that are identical or equivalent to each other in the above-described embodiment and the modifications. Therefore, in the following description of the modifications, the description of the above-described embodiment can be used as appropriate for components that have the same reference numerals as the above-described embodiment, unless there is a technical contradiction or special additional explanation.

[0030] The present disclosure is not limited to the specific configurations or structures described in the above embodiments and examples. That is, for example, the SiC filler 12 may include SiC powder particles that do not satisfy the above conditions, such as SiC powder particles having a circularity of 0.206 or more. In other words, the SiC filler 12 may be a mixed powder of dendrites having a circularity of 0.206 or more and dendrites having a circularity of less than 0.206 dispersed in the continuous phase 11. Alternatively, for example, SiC dendrite powder particles having a circularity of 0.206 or more may be considered to be the additional filler 13 shown in FIG. 8.

[0031] 9 and other figures, either the first bonding body 23 or the second bonding body 24 may be formed of a material different from that of the composite material 10. The cooling device 26 shown in FIG. 12 may be configured without using a refrigerant, for example, may be configured using a Peltier element.

[0032] It goes without saying that the elements constituting the above-described embodiments are not necessarily essential unless expressly stated as essential or clearly considered essential in principle. Furthermore, when numerical values ​​such as the number, amount, and range of components are mentioned, the present disclosure is not limited to those specific numerical values ​​unless expressly stated as essential or clearly limited to specific numerical values ​​in principle. Similarly, when the shape, direction, positional relationship, etc. of components are mentioned, the present disclosure is not limited to those shapes, directions, positional relationships, etc., unless expressly stated as essential or clearly limited to specific shapes, directions, positional relationships, etc. in principle.

[0033] The modified examples are not limited to the above examples. For example, other than those exemplified above, multiple embodiments may be combined with each other as long as there is no technical contradiction. Similarly, multiple modified examples may be combined with each other as long as there is no technical contradiction.

[0034] (Disclosure perspective) As is clear from the above description of the embodiments and modifications, the present specification and drawings disclose at least the following matters, although the disclosed matters are not limited to those described below.

[0035] [First viewpoint] A SiC filler (12), The dendrites have a circularity of less than 0.206 in a cross-sectional view. SiC filler. [Second perspective] The crystalline polymorphism is any one of 3C, 4H, 6H, and 15R, or a combination of two or more of these. The SiC filler according to the first aspect. [Third Perspective] The size diameter is 10 to 100 μm. A SiC filler according to the first or second aspect. [Fourth viewpoint] The average value of the circularity is 0.20 or less. The SiC filler according to any one of the first to third aspects. [Fifth viewpoint] A composite material (10) containing the SiC filler according to any one of the first to fourth aspects, The SiC filler is dispersed in a continuous phase (11) made of metal or synthetic resin. Composite material. [Sixth viewpoint] Further containing an additional filler (13) different from the SiC filler, A composite according to the fifth aspect. [Seventh viewpoint] The additional filler is spherical. A composite material according to a sixth aspect. [Eighth viewpoint] A semiconductor device (20) using the composite material according to any one of the fifth to seventh aspects, A semiconductor element (21), a bonded body (23, 24) formed in the shape of a plate or layer and bonded to the semiconductor element; A semiconductor device comprising: [Explanation of symbols]

[0036] 10 Composite materials 11 Continuous Phase 12 Filler 20 Semiconductor Devices 21 elements 22 Heat sink 23 Daiichi composite material 24 Second composite material 26 Cooling device 27 TIM material

Claims

1. A SiC filler (12), The dendrites have a circularity of less than 0.206 in a cross-sectional view. SiC filler.

2. The crystalline polymorph is any one of 3C, 4H, 6H, and 15R, or a combination of two or more thereof; The SiC filler according to claim 1 .

3. The size diameter is 10 to 100 μm. The SiC filler according to claim 1 .

4. The average value of the circularity is 0.20 or less. The SiC filler according to claim 1 .

5. A composite material (10) containing the SiC filler according to any one of claims 1 to 4, The SiC filler is dispersed in a continuous phase (11) made of a metal or a synthetic resin. Composite material.

6. Further containing an additional filler (13) different from the SiC filler, The composite material of claim 5.

7. The additional filler is spherical. The composite material of claim 6.

8. A semiconductor device (20) using the composite material according to claim 5, A semiconductor element (21); a bonded body (23, 24) formed in the shape of a plate or layer and bonded to the semiconductor element; A semiconductor device comprising:

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