JP2022002266A - Semiconductor light emitting device - Google Patents

Abstract

To provide a semiconductor light emitting device that has desired characteristics as a heat dissipating thin film of the semiconductor light emitting device.SOLUTION: A semiconductor light emitting device comprises: a semiconductor light emitting element; a support that supports the semiconductor light emitting element; and a composite plated layer that is between the semiconductor light emitting element and the support and includes a metal layer in which diamond particles are dispersed. The diamond particles have a first particle group having a volume occupancy rate of 59 vol% or more and a particle diameter of 64 μm or more and 200 μm or less, and a second particle group having a particle diameter of 16 μm or more and 50 μm or less. The diamond particles do not substantially have particles having a particle diameter exceeding 50 μm and less than 64 μm. The particle diameter when the particles take the maximum value of the volume occupancy rate in the second particle group is one-fourth or less of the particle diameter when the particles take the maximum value of the volume occupancy rate in the first particle group. The volume occupancy rate integrated within the particle diameter range of the second particle group is smaller than the volume occupancy rate integrated within the particle diameter range of the first particle group.SELECTED DRAWING: Figure 4

Description

The present invention relates to a semiconductor light emitting device.

A metal layer containing diamond particles has long been used as a heat-dissipating material for efficiently diffusing the heat generated by an electronic component to the outside. For example, Patent Document 1 and Patent Document 2 disclose a composite plating layer in which diamond particles are composited in a metal plating layer. Regarding the method for forming such a composite plating layer, Patent Document 1 describes electrolytic plating while stirring a plating solution in which diamond particles are dispersed, and fixes the diamond particles in the metal plating layer to obtain a composite plating layer. The method is disclosed. This film forming method is called a stirring method. In Patent Document 2, stirring of the plating solution in which diamond particles are dispersed is stopped, electrolytic plating is performed while depositing the settling diamond particles in the densest structure, and the diamond particles are fixed in the metal plating layer to form a composite plating layer. Is disclosed how to obtain. This film forming method is called a sedimentation method.

Further, as a metal layer containing diamond particles, a composite containing diamond particles is also known in addition to the above-mentioned composite plating layer. Patent Document 3 discloses an aluminum-diamond-based composite in which an aluminum alloy contains diamond powder composed of two particle groups having different particle diameters. Regarding the method for producing such a composite, Patent Document 3 describes a high-pressure container in which diamond powder is loaded and impregnated with a molten metal such as an aluminum alloy under high temperature and high pressure to form an aluminum-diamond composite. The obtained molten metal forging method is disclosed.

International Publication No. 2011/096432 Japanese Unexamined Patent Publication No. 2015-160996 International Publication No. 2018/1233380

Consider using a metal layer containing diamond particles as a heat-dissipating thin film that diffuses heat from a semiconductor light-emitting element to a support that supports the light-emitting element in a semiconductor light-emitting device such as an LD or LED. For forming such a metal layer, the method for forming a composite plating layer by electrolytic plating shown in Patent Documents 1 and 2 is easier to use than the molten metal forging method shown in Patent Document 3. One of the reasons is that the molten metal forging method requires complicated and large-sized manufacturing equipment to obtain a high-temperature and high-pressure environment, whereas the film-forming method by electrolytic plating requires relatively simple and small-sized manufacturing equipment. Can be mentioned. Therefore, there is a problem that it is expensive to make by the molten metal forging method and cannot be used for mass-produced products such as semiconductor light emitting devices, which require low cost. Therefore, a method of forming a composite plating layer by electrolytic plating is adopted for forming a heat-dissipating thin film of a semiconductor light emitting device.

However, with the stirring method shown in Patent Document 1, it is difficult to improve the volume occupancy of the diamond particles in the composite plating layer, so that the desired characteristics as a semiconductor light emitting device cannot be obtained. Further, in the sedimentation method shown in Patent Document 2, the volume occupancy of the diamond particles in the composite plating layer can be increased as compared with Patent Document 1, but the volume occupancy can be increased only up to 74 vol%.

It is an object of the present inventor to solve the above-mentioned problems and to provide a semiconductor light emitting device having desired characteristics as a heat dissipation thin film of the semiconductor light emitting device.

The semiconductor light emitting device of the present invention includes a semiconductor light emitting device and
A support that supports the semiconductor light emitting device and
A composite plating layer, which is between the semiconductor light emitting device and the support and is configured to include a metal layer in which diamond particles are dispersed, is provided.
In the composite plating layer, the volume occupancy of the diamond particles is 59 vol% or more, and the volume occupancy is 59 vol% or more.
The diamond particles have a first particle group having a particle diameter of 64 μm or more and 200 μm or less and a second particle group having a particle diameter of 16 μm or more and 50 μm or less, while substantially particles having a particle diameter of more than 50 μm and less than 64 μm. I don't have it
In the graph in which the particle size of the diamond particles is on the horizontal axis and the volume occupancy rate per unit particle size width of the diamond particles in the composite plating layer is on the vertical axis.
The first particle group and the second particle group each have at least one peak value of volume occupancy.
The particle diameter when the maximum value of the volume occupancy is taken among the peak values in the second particle group is the maximum value of the volume occupancy among the peak values in the first particle group. It is 1/4 times or less of the particle size,
The volume occupancy integrated in the range of the particle size of the second particle group is smaller than the volume occupancy integrated in the range of the particle size of the first particle group.

Although the details will be described later, the present invention can increase the volume occupancy of diamond particles in the composite plating layer, and bring the coefficient of thermal expansion of the composite plating layer closer to the coefficient of thermal expansion of the semiconductor light emitting element, resulting in the result. , Distortion given to the semiconductor light emitting element can be suppressed. In addition, the thermal conductivity of the composite plating layer is improved, and as a result, the heat dissipation is improved.

The diamond particles further have a third particle group having a particle diameter of 0.5 μm or more and less than 16 μm.
In the graph in which the particle diameter of the diamond particles is on the horizontal axis and the volume occupancy of the diamond particles per unit particle diameter width in the composite plating layer is on the vertical axis.
The third particle group has at least one peak value of volume occupancy.
The particle diameter at the time of taking the maximum value among the peak values in the third particle group is 1/4 times or less the particle diameter at the time of taking the maximum value among the peak values in the second particle group.
The volume occupancy integrated in the particle size range of the third particle group may be smaller than the volume occupancy integrated in the particle size range of the second particle group.

The volume occupancy integrated in the range of the particle diameter of the first particle group may be 40 vol% or less.

It is preferable that the diamond particles do not exist on the surface of the composite plating layer on the side on which the semiconductor light emitting device is placed.

When the composite plating layer is divided into two in the thickness direction and divided into a first layer close to the semiconductor light emitting element and a second layer close to the support, the volume occupancy of the diamond particles in the first layer is the above. It may be larger than the volume occupancy of the diamond particles in the second layer.

The metal layer may be a layer containing copper as a main component.

The semiconductor light emitting device is preferably GaAs-based. In addition, in this specification, a GaAs system includes a binary compound semiconductor composed of GaAs, as well as a ternary or more compound semiconductor such as AlGaAs or InGaAs.

This makes it possible to provide a semiconductor light emitting device having a composite plating layer showing high thermal conductivity and high mass productivity.

It is a partial cross-sectional view of the 1st Embodiment of a semiconductor light emitting device. FIG. 3 is an enlarged cross-sectional view of a main part of the A1 region of FIG. It is a figure which showed schematically the cross section of the composite plating layer of 1st Embodiment. For the diamond particles contained in the composite plating layer of the first embodiment, the graph shows the particle size of each diamond particle on the horizontal axis and the volume occupancy rate per unit particle size width of the diamond particles of each particle size on the vertical axis. be. It is a graph which showed the diamond particle diameter on the horizontal axis and thermal conductivity on the vertical axis for each volume occupancy of diamond particles about the composite plating layer of 1st Embodiment. It is a graph which showed the volume occupancy rate of the diamond particle in the composite plating layer on the horizontal axis, and the thermal expansion rate on the vertical axis about the composite plating layer of 1st Embodiment. It is an enlarged sectional view of the main part around the composite plating layer in the 2nd Embodiment of a semiconductor device. For the diamond particles contained in the composite plating layer of the second embodiment, the graph shows the particle size of each diamond particle on the horizontal axis and the volume occupancy rate per unit particle size width of the diamond particles of each particle size on the vertical axis. be. It is an enlarged sectional view of the main part of the 3rd Embodiment of a semiconductor light emitting device. It is an enlarged sectional view of the main part of the reference form of a semiconductor light emitting device. It is a top view of the 4th Embodiment of a semiconductor light emitting device. 11 is a cross-sectional view taken along the line A2-A2 of the semiconductor light emitting device of FIG. 11 in a plane.

An embodiment of the semiconductor light emitting device will be described with reference to the drawings. It should be noted that the drawings disclosed in the present specification are merely schematically illustrated. That is, the dimensional ratio on the drawing does not always match the actual dimensional ratio, and the dimensional ratio does not always match between the drawings.

Hereinafter, the description will be given with reference to the XYZ coordinate system as appropriate. Further, in the present specification, when the positive and negative directions are distinguished when expressing the directions, they are described with positive and negative signs such as "+ X direction" and "-X direction". Further, when expressing a direction without distinguishing between positive and negative directions, it is simply described as "X direction". That is, in the present specification, when it is simply described as "X direction", both "+ X direction" and "-X direction" are included. The same applies to the Y direction and the Z direction.

<First Embodiment>
[Semiconductor light emitting device]
The first embodiment of the semiconductor light emitting device will be described. FIG. 1 is a partial cross-sectional view of the semiconductor light emitting device 100. The semiconductor light emitting device 100 includes a semiconductor light emitting element 1 and a support 2 that supports the semiconductor light emitting element 1. Between the semiconductor light emitting element 1 and the support 2, a composite plating layer 3 and a seed layer 4 are provided in this order from the semiconductor light emitting element 1 side.

The semiconductor light emitting device 1 is composed of an end face light emitting type LD chip using a GaAs-based semiconductor material. The semiconductor light emitting device 1 emits the laser beam L1 from the light emitting end face 1e. The semiconductor light emitting device 1 is not limited to this embodiment, and for example, the semiconductor light emitting device 1 may be made of a semiconductor material other than the GaAs type (for example, GaN type, InP type, etc.). Further, the semiconductor light emitting device 1 may be an LED chip.

The seed layer 4 is used to enhance the adhesion between the composite plating layer 3 and the support 2. For example, when the surface of the support 2 is not conductive (for example, the surface of the support 2 is a SiO ₂ film), it is difficult to obtain sufficient adhesion by forming a film by electroplating, so that the surface of the support 2 is thinly conductive. A sex layer is formed. The seed layer 4 is not particularly limited, but is composed of, for example, a layer formed by sputtering titanium / platinum / gold, titanium / gold, chromium / platinum / gold, or chromium / gold. The seed layer 4 may be omitted.

The support 2 supports the semiconductor light emitting device 1 and absorbs and diffuses the heat generated in the semiconductor light emitting device 1. The support 2 may be, for example, a submount made of an AlN substrate or the like.

In the present embodiment, the semiconductor light emitting device 1 is in contact with the composite plating layer 3, but another layer is interposed between the semiconductor light emitting element 1 and the composite plating layer 3, and the semiconductor light emitting device 1 is the composite plating layer 3. It may be in a form that is not in contact with. Examples of another layer include a solder layer for joining the semiconductor light emitting device 1 and the composite plating layer 3, a solder block layer for preventing solder from flowing out to another layer, a light reflection layer, and the like. ..

[Overview of composite plating layer]
The composite plating layer 3 will be described. FIG. 2 is an enlarged cross-sectional view of a main part of the A1 region (region in which the semiconductor light emitting device 1 and the composite plating layer 3 are in contact with each other) in FIG. The composite plating layer 3 includes a layer in which diamond particles (31, 32) are dispersed in the metal layer 30. The metal layer 30 is a material having thermal conductivity, and in this embodiment, the metal layer 30 is made of copper. However, the metal layer 30 may be made of a copper alloy, or may be made of a non-copper material such as aluminum having a relatively high thermal conductivity. Further, as will be described in detail later, the diamond particles (31, 32) include diamond particles 31 constituting the first particle group and diamond particles 32 constituting the second particle group in descending order of particle diameter.

First, the significance of including diamond particles (31, 32) in the metal layer 30 will be described. First, diamond is a material having higher thermal conductivity than copper constituting the metal layer 30. Therefore, when the volume occupancy of the diamond particles (31, 32) in the composite plating layer 3 is improved, the heat conduction characteristics of the composite plating layer 3 are basically improved, and the heat dissipation of the semiconductor light emitting device 100 is improved accordingly. do. However, although the details will be described later, the thermal conduction characteristics of the composite plating layer 3 may not be improved depending on the particle size of the diamond particles (31, 32).

Next, the particle size of the diamond particles will be described. As used herein, the diameter of a diamond particle is defined by the diameter of a true sphere having the same volume as the diamond particle. For example, the particle diameter of the diamond particle 31 in FIG. 2 is represented by the diameter φ1 of a true sphere (a circle represented by a alternate long and short dash line in FIG. 2) having a volume equivalent to that of the diamond particle 31. The particle diameter of the diamond particles 32 is represented by a diameter of φ2. An example of this particle size measuring method is shown in the volume occupancy measuring method of diamond particles described later.

FIG. 3 is a diagram schematically showing a cross section of the composite plating layer 3 in a region in contact with the semiconductor light emitting device 1 (for example, an A1 region). In this figure, a diamond particle is drawn with a true sphere having the same volume as the diamond particle (31, 32). The actual shape of the diamond particles (31, 32) is complicated, and the orientation of the diamond particles (31, 32) is not unified, but the true sphere drawn in FIG. 3 is an actual diamond. It can be said that the volumes of the particles (31, 32) are averaged and displayed.

[Volume occupancy of diamond particles in the composite plating layer]
The volume occupancy of the diamond particles (31, 32) in the composite plating layer 3 will be described. The diamond particles 31 having a relatively large particle diameter are closely arranged close to each other in order to increase the volume occupancy. By arranging the diamond particles 32 having a relatively small particle diameter in the gaps between the adjacent diamond particles 31, the volume occupancy of the diamond particles (31, 32) in the composite plating layer 3 is increased. That is, by mixing diamond particles (31, 32) having different particle diameters, the volume occupancy in the composite plating layer 3 is increased, and the heat conduction characteristics of the composite plating layer 3 are improved. In the present specification, the volume occupancy rate indicates the ratio of the volume occupied by the diamond particles to the volume of the entire composite plating layer 3 as a percentage.

FIG. 4 shows the volume occupancy of the diamond particles (31, 32) contained in the composite plating layer 3 per unit particle size width of the diamond particles of each particle size with the particle size (μm) of each diamond particle as the horizontal axis. It is a graph which plotted (vol% / μm) on the vertical axis. By integrating this graph in the range of an arbitrary particle size, the volume occupancy of diamond particles in the range of the particle size in the composite plating layer 3 can be obtained. In this graph, the volume of diamond particles is measured using a three-dimensional X-ray microscope described later, and the particle size of a true sphere having the same volume as the diamond particles is derived from the measurement results, and each particle group by particle size is derived. Obtained by sorting and organizing.

The diamond particle 31 is composed of a first particle group 71 having a particle diameter of 64 μm or more and 200 μm or less. The diamond particle 32 is composed of a second particle group 72 having a particle diameter of 16 μm or more and 50 μm or less. As shown in FIG. 4, each particle group (71, 72) represents a set of diamond particles having a particle diameter in a certain range. In each particle group (71, 72), it is not necessary that the particle diameters of the diamond particles are all the same. Each particle swarm (71,72) has at least one peak value of volume occupancy. In this embodiment, the first particle group 71 has three peak values (P11, P12, P13) and the second particle group 72 has two peak values (P21, P22).

Of the two peak values (P21, P22) in the second particle group 72, the particle diameter (30 μm in FIG. 4) when the maximum value of the volume occupancy is taken is the peak value (P11, P11, in the first particle group 71). It is 1/4 times or less the particle size (180 μm in FIG. 4) when the maximum value is taken among P12 and P13). Therefore, the diamond particles 32 of the second particle group 72 can enter the gaps between the diamond particles 31 of the adjacent first particle group 71. In addition, even if the diamond particles 32 enter, the diamond particles 32 do not protrude from the composite plating layer 3 and the flatness of the upper surface 3a of the composite plating layer 3 can be maintained (see FIGS. 2 and 3).

The composite plating layer 3 does not substantially have diamond particles having a particle diameter of more than 50 μm and less than 64 μm. Here, "substantially having no diamond particles having a particle diameter of more than 50 μm and less than 64 μm" means that the volume occupancy integrated in the particle diameter range of 50 to 64 μm of the diamond particles is less than 1 vol%. Represents. As a result, the diamond particles 32 constituting the second particle group 72 have a size and number that are easily arranged in the gaps between the diamond particles 31 constituting the first particle group 71, and the diamond particles (31, 32) in the composite plating layer 3 are formed. ) Can increase the volume occupancy. In addition, the diamond particles 32 can maintain the flatness of the upper surface 3a of the composite plating layer 3 without protruding from the composite plating layer 3 (see FIGS. 2 and 3).

The reason why the upper limit of the first particle group 71 is 200 μm will be described. The composite plating layer 3 is often formed on the surface of a part of the support 2. For such partial film formation, a lift-off method is usually performed in which a composite plating layer 3 is provided on a resist pattern thicker than the thickness of the composite plating layer 3 and the composite plating layer 3 in an unnecessary portion is removed together with the resist pattern. Is used. Therefore, the upper limit of the thickness of the composite plating layer 3 depends on the upper limit of the thickness of the resist film used in the lift-off method. Considering that the upper limit of the thickness of the resist film which is easy to form a film is 200 μm, it is preferable that the upper limit of the thickness of the plating layer is also 200 μm or less in order to perform the lift-off method. The particle diameter φ1 of the diamond particles 31 is limited to the thickness of the composite plating layer 3. Therefore, the particle size of the diamond particles 31 is preferably 200 μm or less.

By the way, the thermal conductivity in the interface region between the diamond particles (31, 32) and the metal layer 30 is different from both the thermal conductivity of the diamond particles (31, 32) and the thermal conductivity of the metal layer 30. The present inventor has noted that when the metal layer 30 is copper, the thermal conductivity in the interface region between the diamond particles (31, 32) and copper is lower than the thermal conductivity of copper. It is presumed that the reason for this is that the minute gaps at the interface between the diamond particles (31, 32) and copper hinder heat conduction. This means that the larger the particle size of the diamond particles, the smaller the area of the interface between the copper and the diamond particles when the volume occupied by the diamond in the same volume is the same, and the heat conduction characteristics are enhanced. Means. In the semiconductor light emitting device 100 of the present embodiment, the volume occupancy S2 (total area of the hatching region consisting of horizontal lines in FIG. 4) integrated in the particle diameter range of 16 μm to 50 μm of the second particle group 72 is the first particle. It is smaller than the volume occupancy S1 (total area of the hatching region consisting of vertical lines in FIG. 4) integrated in the particle size range of 64 μm to 200 μm of the group 71. That is, the volume occupancy of the entire diamond particles 31 constituting the first particle group 71 is larger than the volume occupancy of the entire diamond particles 32 constituting the second particle group 72, and the thermal conductivity of the composite plating layer 3 is increased. Easy to raise.

[Heat conduction characteristics of composite plating layer]
The heat conduction characteristics of the composite plating layer will be described. The following theoretical formula is known for calculating the thermal conductivity of a composite plating layer containing diamond particles.

In (1), k: thermal conductivity of the composite plated layer _{(W / mK), k m} : thermal conductivity of the metal layer _{(W / mK), k d} : the thermal conductivity of the diamond particles (W / mK) , V _d : Volume occupancy of diamond particles, α: Radius of diamond particles (m), h _c : Thermal conductivity at the interface between diamond and metal layer (W / m ² K).

The theoretical value of the thermal conductivity of the composite plating layer containing diamond particles can be calculated by using the equation (1). 5, using the equation (1), each volume fraction V _d of the diamond particles, the particle size of the diamond particles ([mu] m) on the horizontal axis, the thermal conductivity of the composite plating layer (W / mK) Vertical It is a graph shown on the axis. From this graph, it can be seen that the smaller the particle diameter (diameter), the lower the thermal conductivity k of the composite plating layer. This is because the smaller the particle size, the larger the area of the interface between the diamond particles and the metal layer, and the lower the thermal conductivity.

From FIG. 5, when the particle size of the diamond particles is 16 μm or more, the thermal conductivity of copper exceeds 400 W / mK, but when the particle size is less than 16 μm, the thermal conductivity of the diamond particles is lower than the thermal conductivity of copper. Recognize. Therefore, by reducing the number of diamond particles having a particle size of less than 16 μm or increasing the number of diamond particles having a particle size of 16 μm or more, the thermal conductivity of the composite plating layer is higher than that of the metal layer made of copper. Can also be high.

[Thermal expansion characteristics of the composite plating layer]
Since the composite plating layer 3 is arranged in contact with the semiconductor light emitting device 1 or in the vicinity of the semiconductor light emitting device 1 via another thin film, the difference in thermal expansion rate between the semiconductor light emitting device 1 and the composite plating layer 3 is large. If it is large, when the temperature of the semiconductor light emitting device 100 changes, the semiconductor light emitting element 1 is pulled by the composite plating layer 3 and is easily distorted. By adjusting the amount of diamond particles in the composite plating layer 3, the effect of reducing the distortion of the semiconductor light emitting device 1 due to thermal expansion can be obtained. This will be described.

The coefficient of thermal expansion (hereinafter referred to as "CTE") of copper, which is the metal layer 30, is 16.5 × ^10-6 (/ K), whereas the CTE of diamond particles is 1. .1 × ^10-6 (/ K). That is, in the composite plating layer 3 composed of copper-diamond particles, the CTE of the composite plating layer 3 can be lowered by increasing the volume of the diamond particles.

FIG. 6 is a graph in which the horizontal axis represents the volume occupancy of diamond particles in the composite plating layer 3 and the vertical axis represents CTE. In the graph, the broken line G1 indicates the CTE of the composite plating layer 3 when the volume occupancy of the diamond particles contained in the composite plating layer 3 is changed. The broken line G1 is the point P1 (volume occupancy is 50 vol%, CTE is 6.6 × 10 ^-6 / K) and the point P2 (volume occupancy is 67 vol%, CTE is 6.05 × 10 ^{-6) obtained by calculation.} It is represented as a straight line passing through / K). ^{Line D1 represents 5.5 × 10-6} (/ K), which is the CTE of GaAs. The alternate long and short dash line Du represents + 15% (CTE: 6.33 × 10 ⁻⁶ ) with respect to the CTE of the line D1. The alternate long and short dash line Dd represents -15% (CTE: 4.68 × 10 ^-6 ) with respect to the CTE of the line D1.

As a result of the research by the present inventor, when the CTE of the composite plating layer 3 is in the range of Dd or more and Du or less, the CTE of the composite plating layer 3 approaches the CTE of the semiconductor light emitting device 1, so that the distortion given to the semiconductor light emitting device 1 is caused. It turned out that it can be suppressed. From this result and FIG. 6, in order to suppress the strain applied to the semiconductor light emitting device 1, the volume occupancy of the diamond particles (integrated at each particle diameter) in the composite plating layer 3 should be 59 vol% or more. I understand.

Further, the support 2 is usually made of a material having a small CTE. Considering that the CTE of the composite composed of the support 2 and the composite plating layer 3 is designed to be balanced with the semiconductor light emitting device 1, the CTE of the composite plating layer 3 has a value of + 6% or less with respect to the CTE of D1. It is more preferable to set to. From this, it is more preferable that the volume occupancy of the composite plating layer 3 is 76 vol% or less.

From the above, the particle size and volume occupancy of the diamond particles contained in the composite plating layer 3 are determined from the viewpoints of thermal conductivity and CTE. Considering only the thermal conductivity, the composite plating layer 3 may be formed only of diamond particles having a particle diameter of 16 μm or more. However, if the CTE of the composite plating layer 3 is also taken into consideration, diamond particles having a particle size of less than 16 μm may be used in combination to increase the volume occupancy. Of course, only diamond particles having a particle diameter of 16 μm or more may be used, the volume occupancy of the composite plating layer 3 may be 59 vol%, and the CTE of the composite plating layer 3 may be set to a desired value.

[Method for forming composite plating layer]
The composite plating layer 3 is formed by an electrolytic plating method. In the case of the stirring method, diamond particles (31, 32) composed of the above-mentioned particle group are put into the plating solution which is the material of the metal layer 30, and the support 2 is arranged in the plating solution. Then, electrolytic plating is performed while stirring the plating solution, and the metal layer 30 (that is, that is, the metal layer 30 (that is, 32) containing diamond particles (31, 32) is formed on the surface of the support 2 (or the seed layer 4 provided on the surface of the support 2). , A composite plating layer 3) is formed.

When the stirring method is used, the volume occupancy of the composite plating layer 3 is limited to 40 vol% when only diamond particles composed of a single particle group are used. It is considered that the reason is that the diamond particles in the plating solution do not adhere to each other but exist through the space where they can flow with each other, and are smaller than the volume occupancy in the close contact state. For example, the volume occupancy of a true sphere with respect to a cube is 52%, but considering the above-mentioned flow space, the volume occupancy after plating becomes smaller than this.

However, the present inventors can apply a stirring method by adding diamond particles 32 (diamond particles of a small particle group) composed of the second particle group 72 to the diamond particles 31 of the first particle group 71. It has been found that the volume occupancy of the composite plating layer 3 as a whole can be increased even if it is used.

In the case of the settling method, the components of the plating solution in which the diamond particles composed of the desired particle group are dispersed are settled, and electrolytic plating is performed while taking longer than the stirring method to obtain the composite plating layer 3. Since the sedimentation method has a close-packed structure, the volume occupancy of the diamond particles can be increased as compared with the case of using the stirring method. The diamond particles to be charged into the plating solution may be formed into a desired composition by appropriately combining commercially available diamond particles defined by the particle size. Further, the film may be formed by the stirring method at first, and then switched to the sedimentation method in the middle to form the film. Hereinafter, this method is referred to as a stirring sedimentation method. The stirring sedimentation method can form a film in a shorter time than the case where only the sedimentation method is used.

[Method for measuring volume occupancy of diamond particles in composite plating layer]
The volume occupancy of the diamond particles is determined by counting the volume and number of the charged diamond particles for each particle size at the time of film formation of the composite plating layer 3 and determining the film formation thickness of the composite plating layer 3. Can be guided. As a method for obtaining the volume occupancy of diamond particles from the composite plating layer 3 after film formation, there is a method using a three-dimensional X-ray microscope (X-ray CT, for example, ZEISS Xradia 510 Versa manufactured by Carl Zeiss). Using X-ray CT, and measuring the volume of the diamond particles contained in the composite plating layer 3 of an arbitrary area and thickness, the official volume of the measured volume and sphere of each particle (V = πD ^3/6, where Then, V represents the volume of the sphere, and D represents the diameter of the sphere). It can be calculated by obtaining the volume occupancy in the layer 3.

<Second embodiment>
A second embodiment of the semiconductor light emitting device will be described with reference to FIGS. 7 and 8. Matters other than those described below can be carried out in the same manner as in the first embodiment. The same applies to the third and subsequent embodiments.

FIG. 7 is an enlarged cross-sectional view of a main part around the composite plating layer 5, similarly to FIG. 2. As in FIG. 4, FIG. 8 shows the volume occupancy of the diamond particles contained in the composite plating layer 5 per unit particle size width of the diamond particles of each particle size with the particle size (μm) of each diamond particle as the horizontal axis. It is a graph which showed the rate (vol% / μm) on the vertical axis. In the composite plating layer 5 of the present embodiment, the diamond particles 31 constituting the first particle group 71 having a particle size of 64 μm or more and 200 μm or less and the second particles having a particle size of 16 μm or more and 50 μm or less are formed in descending order of particle size. The diamond particles 32 constituting the group 72, the diamond particles 33 constituting the third particle group 73 having a particle size of 0.5 μm or more and less than 16 μm, and the fourth particle group 74 having a particle size of less than 0.5 μm are formed. The diamond particles 34 and the like are included. Further, the composite plating layer 5 does not substantially have diamond particles having a particle diameter of more than 50 μm and less than 64 μm.

The third particle group 73 has at least one peak value of volume occupancy (one of the peak values P31 in FIG. 8). The particle diameter (1 μm in FIG. 8) when the maximum value of the peak value P31 in the third particle group 73 is taken is the particle diameter when the maximum value is taken among the peak values (P21, P22) in the second particle group 72. It is 1/4 times or less of (30 μm in FIG. 8). The fourth particle group 74 has at least one peak value of volume occupancy (particle diameter is 0.1 μm) (one of the peak values P41 in FIG. 8). The integrated value S3 of the volume occupancy of the third particle group 73 (the area of the hatched region consisting of diagonal lines rising to the left) is the integrated value S2 of the volume occupancy of the second particle group 72 (the area of the hatched region consisting of the horizontal lines). Smaller than.

In the composite plating layer 5, the metal layer 30 in the gaps between the diamond particles (31, 32) can be filled with the diamond particles 33. In addition, the metal layer 30 in the gaps between the diamond particles (31, 32, 33), which are too large to be filled with the diamond particles 33, can be filled with the diamond particles 34. As a result, the volume occupancy in the composite plating layer 5 can be further increased and the CTE can be lowered.

As a modification of the present embodiment, a composite plating layer composed of the first particle group 71, the second particle group 72, and the third particle group 73, which does not include the fourth particle group 74, may be used.

<Third embodiment>
The third embodiment will be described with reference to FIG. 9. FIG. 9 is an enlarged cross-sectional view of a main part, similar to FIG. 2. The composite plating layer 6 of the present embodiment has an electrodeposition layer 35 at the boundary with the seed layer 4 which is the lower layer, and has a cap layer 36 at the boundary with the semiconductor light emitting device 1 which is the upper layer.

The electrodeposition layer 35 will be described. The electrodeposition layer 35 is a layer composed of only the diamond particles 31 constituting the first particle group 71 and the metal layer 30 (or the diamond particles 32 composed of the diamond particles 31 and a relatively small amount of the second particle group 72). And a layer composed of only the metal layer 30). The electrodeposition layer 35 can be obtained by performing electrolytic plating with a plating solution containing no diamond particles 32 or a relatively small amount of diamond particles 32 at the initial stage of forming the composite plating layer 6. .. The thickness of the electrodeposition layer 35 may be thinner than the particle diameter φ1 of the diamond particles 31 constituting the first particle group 71.

The advantages of providing the electrodeposition layer 35 will be described. In the case of a plating solution containing diamond particles 31 constituting the first particle group 71 and diamond particles 32 constituting the second particle group 72 in a normal amount, small diamond particles are formed at the initial stage of forming the composite plating layer 6. If a large number of 32 enters between the large diamond particles 31 and the support 2, the diamond particles 31 may be prevented from sticking to the support 2. Therefore, by forming the electrodeposition layer 35 with a plating solution that does not contain the diamond particles 32 constituting the second particle group 72 or is limited to a relatively small amount, the diamond particles 31 can be easily fixed to the support 2. ..

Next, the cap layer 36 will be described. The cap layer 36 is a layer composed of only the metal layer 30 containing no diamond particles (31, 32). The cap layer 36 is obtained by performing electrolytic plating with a plating solution containing no diamond particles (31, 32).

The advantage of providing the cap layer 36 will be described with reference to the reference embodiment of the semiconductor light emitting device shown in FIG. FIG. 10 is an enlarged cross-sectional view of a main part of the composite plating layer 7 having no cap layer. As in the B1 region and the B2 region in FIG. 10, some diamond particles (31, 32) may protrude from the upper surface 7a of the composite plating layer 7. When the diamond particles (31, 32) protrude, the flatness of the upper surface 7a of the composite plating layer 7 is lowered, and the adhesion between the composite plating layer 7 and the semiconductor light emitting device 1 is deteriorated.

Therefore, at the final stage of forming the composite plating layer, only the metal layer containing no diamond particles is formed to form the cap layer 36 (see FIG. 9). As a result, the diamond particles do not exist on the surface of the composite plating layer in contact with the semiconductor light emitting device 1, so that the diamond particles are prevented from protruding and the flatness of the upper surface 6a of the composite plating layer 6 is improved. Therefore, the adhesion between the composite plating layer 6 and the semiconductor light emitting device 1 is maintained. In addition, in order to improve the flatness of the upper surface 6a of the composite plating layer 6, the upper surface 6a of the composite plating layer 6 may be polished.

In the present embodiment, both the electrodeposition layer 35 and the cap layer 36 are provided, but either the electrodeposition layer 35 or the cap layer 36 may be provided. When at least one of the electrodeposition layer 35 and the cap layer 36 is provided, the composite plating layer 6 is divided into two in the thickness direction, and is divided into a first layer close to the semiconductor light emitting device 1 and a second layer close to the support 2. Then, the volume occupancy of the diamond particles in the first layer becomes larger than the volume occupancy of the diamond particles in the second layer.

<Fourth Embodiment>
A fourth embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a top view of the semiconductor light emitting device 200 (a view of the semiconductor light emitting device 200 viewed from the + Z side). Note that FIG. 11 omits the illustration of the light transmitting member 9 described later. FIG. 12 is a cross-sectional view taken along the line A2-A2 of FIG. 1 in the YZ plane. In the cross-sectional view shown in FIG. 12, the illustration of the object located behind the cross section is omitted.

With reference to FIG. 12, the semiconductor light emitting device 200 has a recess 61 on the main surface 60a on the + Z side, and is mounted on a semiconductor substrate 60 mainly composed of silicon and a part of the bottom surface 62 of the recess 61. Further, it has a semiconductor light emitting element 1 that emits laser light from an end face. The light emitting end surface 1e is parallel to the XZ plane.

The semiconductor substrate 60 is shown hatched in FIG. The recess 61 has a shape formed by removing the square pyramid shape from the plate-shaped member, and has a side wall 65 inclined with respect to the bottom surface 62. The area of the recess 61 on the opening side is larger than the area of the recess 61 on the bottom surface 62 side. When viewed from the + Z direction of the semiconductor substrate 60, the side wall 65 exists on all sides surrounding the bottom surface 62.

The laser beam L1 emitted from the semiconductor light emitting device 1 has an inclination facing the emitter and a reflection layer 80 provided on the bottom surface 62 between the emitter (light emitting end surface 1e) and the side wall 65 facing the emitter. The light is reflected by the reflective layer 85 provided on the side wall 65. The reflected laser beam L1 is emitted in the + Z direction so as to be away from the semiconductor light emitting device 200.

The semiconductor light emitting element 1 is directly mounted on the semiconductor substrate 60 without using a submount or the like, and the composite plating layer 8 that functions as a heat dissipation member and a power feeding member between the semiconductor light emitting element 1 and the semiconductor substrate 60. There is. The composite plating layer 8 is composed of the above-mentioned metal layer containing diamond particles. The composite plating layer 8 is electrically connected to an electrode 75 provided on the back surface of the semiconductor substrate 60 through a feeding path 78 buried in a through hole of the semiconductor substrate 60. The feeding path 78 and the electrode 75 do not have to be a metal layer in which diamond particles are dispersed.

The first to fourth embodiments have been described above. However, the present invention is not limited to each of the above-described embodiments, and each of the above-described embodiments may be combined, or various changes or improvements may be made to each embodiment within a range not deviating from the gist of the present invention. You can add it.

The presence or absence of the third particle group 73 and the fourth particle group 74, and the composite plating layer of copper-diamond particles having different volume occupancy of each particle group are described as Examples and Comparative Examples. Conditions other than those described below are common to each Example and each Comparative Example.

[Examples 1 to 4]
Examples 1 to 4 will be described. The composite plating layer was formed by using the film forming method shown in Table 1. The diamond particles contained in the composite plating layer are composed of the first particle group 71 and the second particle group 72, and the diamond particles 33 composed of the third particle group 73 and the diamond particles 34 composed of the fourth particle group 74. Has virtually no.

When the formed composite plating layer was measured using X-ray CT, the values shown in Table 1 were obtained for the volume occupancy of each particle group. In Examples 1 to 4, the total volume occupancy of the diamond particles was 59 vol% or more. Therefore, in Examples 1 to 4, the CTE of the composite plating layer was the CTE of the semiconductor light emitting device 1 (GaAs). The condition of ± 15% or less was satisfied. That is, in Examples 1 to 4, the strain given to the semiconductor light emitting device 1 by the composite plating layer can be sufficiently suppressed.

In addition, the thermal conductivity of the composite plating layer was calculated based on the volume occupancy of each particle group. This calculation is performed as follows. In the case of Example 1, first, assuming that the first particle group is composed of diamond particles having a specific particle size, the composite plating layer is assumed to be only the first particle group by using the equation (1). The thermal conductivity k _{1 of the composite plating layer when it was constructed and the thermal conductivity k 2} of the composite plating layer when the composite plating layer was composed of only the second particle group were obtained. In the case of Example 1, k ₁ = 533 (W / mK) and k ₂ = 429 (W / mK). Next, the volume occupancy of each particle group, in using a proportion of the volume fraction of diamond particles Sum performs weighting working thermal conductivity k ₁ and k _2, the composite plating layer having a different particle groups The thermal conductivity _kt was determined. For example, in the case of Example 1, obtained by the thermal conductivity _{k t = 36/59 × k} 1 + 23/59 × k 2, to obtain the thermal conductivity _k t = 492 to (W / mK). The other examples and comparative examples were calculated in the same manner.

In Examples 1 to 4, since the thermal conductivity kt of the composite plating layer exceeded the thermal conductivity of copper of 400 W / mK, the thermal conductivity was improved by including the diamond particles. Further, in both the sedimentation method and the stirring sedimentation method, the film formation speed of the plating layer composed of a plurality of particle groups is faster than the film formation speed of the plating layer composed of a single particle group.

[Examples 5 to 8]
Examples 5 to 8 will be described. The composite plating layer was formed by using the film forming method shown in Table 1. The diamond particles contained in the composite plating layer are composed of the first particle group 71, the second particle group 72, and the third particle group 73, and do not substantially have the fourth particle group 74. When the formed composite plating layer 3 was measured using X-ray CT, the values shown in Table 1 were obtained for the volume occupancy of each particle group. In Examples 5 to 8, since the total volume occupancy of the diamond particles is 59 vol% or more, the strain given to the semiconductor light emitting device 1 by the composite plating layer can be sufficiently suppressed. Further, since the composite plating layer exceeded the thermal conductivity of copper of 400 W / mK, the thermal conductivity was improved by including the diamond particles. In particular, in Example 5, since the volume occupancy of the first particle group 71 is as low as 40 vol% or less, the composite plating layer 3 of the present invention can be formed by a stirring method. Further, even in the stirring method, the film forming speed of the plating layer composed of a plurality of particle groups is faster than the film forming speed of the plating layer composed of a single particle group.

[Examples 9 to 14]
Examples 9 to 14 will be described. The composite plating layer 3 was formed by using the film forming method shown in Table 1. The diamond particles contained in the composite plating layer 3 are composed of a first particle group 71, a second particle group 72, a third particle group 73, and a fourth particle group 74. When the formed composite plating layer 3 was measured using X-ray CT, the values shown in Table 1 were obtained for the volume occupancy of each particle group. In Examples 9 to 14, since the total volume occupancy of the diamond particles is 59 vol% or more, the strain given to the semiconductor light emitting device 1 by the composite plating layer can be sufficiently suppressed. Further, since the composite plating layer exceeded the thermal conductivity of copper of 400 W / mK, the thermal conductivity was improved by including the diamond particles. In particular, in Examples 9 to 11, since the volume occupancy of the first particle group 71 is as low as 40 vol% or less, the composite plating layer 3 of the present invention can be formed by a stirring method.

[Comparative Examples 1 to 6]
Comparative Examples 1 to 6 will be described. The composite plating layer 3 was formed by using the film forming method shown in Table 2. When the formed composite plating layer 3 was measured using X-ray CT, the values in Table 2 were obtained for the volume occupancy of each particle group. In Comparative Examples 1 to 5, since the composite plating layer exceeded the thermal conductivity of 400 W / mK of copper, the thermal conductivity was improved by including the diamond particles. In Comparative Example 6, the composite plating layer had a thermal conductivity of less than 400 W / mK of copper. This is because the number of diamond particles having a small particle size is relatively large, and the area of the interface between the copper (metal layer) and the diamond particles is large. In each of the comparative examples, the total volume occupancy of the diamond particles was less than 59 vol%. Since the condition that the CTE of the composite plating layer is within ± 15% of the CTE of the semiconductor light emitting device 1 (GaAs) is not satisfied, in each of the comparative examples, the distortion given to the semiconductor light emitting device 1 by the composite plating layer is sufficiently sufficient. Difficult to suppress.

1: Semiconductor light emitting element 1e: Light emitting end surface 2: Support 3, 5, 6, 7, 8: Composite plating layer 3a: Top surface 4: Seed layer 6a, 7a: Top surface (of composite plating layer) 9: Light transmitting member 30: Metal layer 31, 32, 33, 34: Diamond particles 35: Electrodeposition layer 36: Cap layer 60: Semiconductor substrate 61: Recessed portion 62: Bottom surface 65: Side wall 71: First particle group 72: Second particle group 73: Third particle group 74: Fourth particle group 75: Electrode 78: Feed path 80: Reflective layer 85: Reflective layer 100, 200: Semiconductor light emitting device

Claims (7)

With semiconductor light emitting devices,
A support that supports the semiconductor light emitting device and
A composite plating layer, which is between the semiconductor light emitting device and the support and is configured to include a metal layer in which diamond particles are dispersed, is provided.
In the composite plating layer, the volume occupancy of the diamond particles is 59 vol% or more, and the volume occupancy is 59 vol% or more.
The diamond particles have a first particle group having a particle diameter of 64 μm or more and 200 μm or less and a second particle group having a particle diameter of 16 μm or more and 50 μm or less, while substantially particles having a particle diameter of more than 50 μm and less than 64 μm. I don't have it
In the graph in which the particle size of the diamond particles is on the horizontal axis and the volume occupancy rate per unit particle size width of the diamond particles in the composite plating layer is on the vertical axis.
The first particle group and the second particle group each have at least one peak value of volume occupancy.
The particle diameter when the maximum value of the volume occupancy is taken among the peak values in the second particle group is the maximum value of the volume occupancy among the peak values in the first particle group. It is 1/4 times or less of the particle size,
A semiconductor light emitting device, characterized in that the volume occupancy integrated in the range of the particle diameter of the second particle group is smaller than the volume occupancy integrated in the range of the particle diameter of the first particle group. The diamond particles further have a third particle group having a particle diameter of 0.5 μm or more and less than 16 μm.
In the graph in which the particle diameter of the diamond particles is on the horizontal axis and the volume occupancy of the diamond particles per unit particle diameter width in the composite plating layer is on the vertical axis.
The third particle group has at least one peak value of volume occupancy.
The particle diameter at the time of taking the maximum value among the peak values in the third particle group is 1/4 times or less the particle diameter at the time of taking the maximum value among the peak values in the second particle group.
The first aspect of the present invention is characterized in that the volume occupancy integrated in the particle size range of the third particle group is smaller than the volume occupancy integrated in the particle size range of the second particle group. Semiconductor light emitting device. The semiconductor light emitting device according to claim 1 or 2, wherein the volume occupancy integrated in the range of the particle diameter of the first particle group is 40 vol% or less. The semiconductor light emitting device according to any one of claims 1 to 3, wherein the diamond particles are not present on the surface of the composite plating layer on the side on which the semiconductor light emitting device is placed. When the composite plating layer is divided into two in the thickness direction and divided into a first layer close to the semiconductor light emitting device and a second layer close to the support, the volume occupancy of the diamond particles in the first layer is the above. The semiconductor light emitting device according to any one of claims 1 to 4, wherein the volume occupancy of the diamond particles in the second layer is larger than that of the second layer. The semiconductor light emitting device according to any one of claims 1 to 5, wherein the metal layer is a layer containing copper as a main component. The semiconductor light emitting device according to any one of claims 1 to 6, wherein the semiconductor light emitting device is a GaAs type.

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