Multilayer substrate

Abstract

To provide a laminated substrate in which a diamond layer is directly laminated onto a carbon substrate, and which has thermal conductivity and insulating properties suitable for use as a heat dissipation member. [Solution] A laminated substrate comprising a carbon substrate and a diamond layer provided on the surface of the carbon substrate, the diamond layer being composed of diamond particles having an average particle size of more than 1 μm.

Description

Technical Field

[0001] The present disclosure relates to a laminated substrate suitable as a heat dissipation member.

Background Art

[0002] While carbon substrates such as graphite exhibit high thermal conductivity, they also exhibit conductivity. To use a carbon substrate as a heat dissipation member applied to heat dissipation applications of various electrical devices, insulation has been imparted by bonding aluminum nitride (AlN) or the like. However, aluminum nitride has a thermal conductivity that is 1 / 10 that of graphite, and the thermal conductivity is significantly reduced by imparting insulation.

[0003] Diamond is known as a material having a thermal conductivity comparable to that of graphite and exhibiting insulation, and a method of coating this on a carbon substrate has been studied. For example, in Patent Document 1, a laminated substrate in which an intermediate layer made of fine diamonds having an average diameter of 10 nm or less is formed on a carbon substrate and a diamond film is laminated thereon has been reported by a vapor phase synthesis method. Further, in Patent Document 2, it has been reported that a diamond film is formed on a carbon substrate by applying and drying a slurry containing diamond particles.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, an intermediate layer is required to laminate the diamond film to enhance its resistance, making it impossible to directly laminate the diamond film onto the carbon substrate. On the other hand, in Patent Document 2, since the laminated substrate is formed by a liquid-phase method, the inclusion of impurities is unavoidable, making it unsuitable for applications such as heat dissipation components used in electrochemical devices where impurity contamination is undesirable.

[0006] The present disclosure aims to provide at least one of the following: a laminated substrate in which a diamond layer is directly laminated onto a carbon substrate, having thermal conductivity and insulating properties suitable for use as a heat dissipation member, and a method for manufacturing the same. [Means for solving the problem]

[0007] The present invention is as described in the claims, and the gist of this disclosure is as follows: [1] A laminated substrate comprising a carbon substrate and a diamond layer provided on the surface of the carbon substrate, the diamond layer being composed of diamond particles having an average particle size of more than 1 μm. [2] The laminated substrate according to [1], wherein the average particle size of the diamond particles is 2 μm or more and 100 μm or less. [3] The laminated substrate according to [1] or [2], wherein the carbon substrate is a graphite substrate. [4] The laminated substrate according to any one of [1] to [3], wherein the carbon substrate is a graphite substrate oriented in the Z plane. [5] The laminated substrate according to any one of [1] to [4], wherein the diamond layer is formed by chemical vapor deposition. [6] A heat dissipation component, a laminated substrate as described in any one of [1] to [5]. [Effects of the Invention]

[0008] This disclosure provides at least one of the following: a laminated substrate in which a diamond layer is directly laminated onto a carbon substrate, having thermal conductivity and insulating properties suitable for use as a heat dissipation member, and a method for manufacturing the same. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing one embodiment of a laminated substrate in this disclosure. [Figure 2] This is a schematic diagram showing the Z-plane and XY-plane of graphite. [Figure 3] This is a schematic diagram showing a cross-section of a laminated substrate in which a diamond layer is stacked on a graphite substrate oriented in the Z plane. [Figure 4] The SEM observation results of the laminated substrate of Example 1, viewed from the Z-plane direction, are shown. [Modes for carrying out the invention]

[0010] This disclosure will be described in detail with reference to one embodiment. However, this disclosure is not limited to the following embodiment. Furthermore, this disclosure includes any combination of each configuration and parameter disclosed herein, and also includes any combination of upper and lower limits of the values ​​disclosed herein.

[0011] <Laminated substrate> An embodiment of the laminated substrate of this disclosure will be described with reference to Figure 1. As shown in Figure 1, the laminated substrate 100 comprises a carbon substrate 10 and a diamond layer 20 made of diamond particles. In the laminated substrate 100, the diamond layer 20 is directly formed on one main surface of the carbon substrate 10. The laminated substrate 100 is a laminated substrate that does not have an intermediate layer between one main surface of the carbon substrate 10 and the diamond layer.

[0012] The laminated substrate 100 of this disclosure may have a diamond layer 20 on at least one surface of the carbon substrate 10.

[0013] (Carbon substrate) The carbon substrate 10 is a non-diamond carbon base material. As the constituent components of the carbon substrate 10, for example, one or more selected from the group of graphite, amorphous carbon, glassy carbon, amorphous carbon and diamond-like carbon (DLC) can be mentioned, and it is preferably graphite.

[0014] The carbon substrate 10 may be a substrate made of graphite. Graphite has a layered structure in which layers (graphene sheets) in which carbon atoms are bonded and arranged in a hexagonal lattice are stacked. As shown in FIG. 2, in the graphite substrate, the plane parallel to the graphene sheet is the XY plane, and the plane perpendicular to the graphene sheet (the plane in the stacking direction of the graphene sheet) is the Z plane.

[0015] The carbon substrate 10 is preferably a graphite substrate, and more preferably a graphite substrate with Z-plane orientation. The "graphite substrate with Z-plane orientation" in this specification is a graphite substrate whose main surface is the Z plane of graphite.

[0016] As shown in FIG. 3, when the carbon substrate 10 is a graphite substrate 10a with Z-plane orientation, the diamond layer 20 is stacked on the Z plane (Sz). Therefore, the thermal conductivity is further improved as compared with the case of, for example, an XY-plane-oriented graphite substrate whose main surface is the XY plane of graphite. The following is considered as the mechanism for obtaining such an effect, but the mechanism is not limited to this. In the graphite substrate, the thermal conductivity in the stacking direction (Z-axis direction) of the graphene sheets is lower than the thermal conductivity in the in-plane direction (XY plane) of the graphene sheets (thermal conductivity in the Z-axis direction: 7 W / (m·K), thermal conductivity in the in-plane direction: 1700 W / (m·K)). By providing the diamond layer 20 with high thermal conductivity on the surface (Z plane) of the Z-plane-oriented graphite substrate, the thermal conductivity in the Z-axis direction is improved, and as a result, the thermal conductivity of the entire laminated substrate is considered to be further improved. Accordingly, other embodiments of the present disclosure include a laminated substrate comprising a Z-plane oriented graphite substrate and a diamond layer provided on the surface of the graphite substrate, and further, a laminated substrate comprising a Z-plane oriented graphite substrate and a diamond layer provided on the Z-plane of the graphite substrate.

[0017] The thickness of the carbon substrate 10 may be any thickness suitable for use as a heat dissipation component, for example, it may be 50 μm or more, 500 μm or more, or 1 mm or more, and may be 10 mm or less, or 5 mm or less. The thickness of the carbon substrate 10 may be 50 μm or more and 10 mm or less, or 1 mm or more and 2 mm or less.

[0018] (Diamond layer) The diamond layer 20 is typically composed of diamond particles, and the diamond layer 20 consists of diamond particles with an average particle size of more than 1 μm. The fact that the average particle size of the diamond particles is within this range allows the laminated substrate of this embodiment to have insulating properties suitable for use as a heat dissipation member.

[0019] The average particle size of the diamond particles may be 1.5 μm or more, 2 μm or more, or 5 μm or more, as this further improves the insulating properties. The average particle size of the diamond particles may be 50 μm or less, 20 μm or less, or 10 μm or less, as this further improves the uniformity of the diamond layer. Examples of average particle sizes of diamond particles that are greater than 1 μm and 50 μm or less, or between 2 μm and 20 μm, are provided.

[0020] The particle size of each diamond particle may be any size that allows the diamond layer 20 to be formed, but the minimum diameter of the diamond particle may be 0.1 μm or larger, 0.5 μm or larger, or 0.8 μm or larger, and may also be 10 μm or smaller, 5 μm or smaller, or 2 μm or smaller. The minimum diameter of the diamond particle may be 0.1 μm or larger and 10 μm or smaller, or 0.8 μm or larger and 2 μm or smaller.

[0021] Similarly, the maximum diameter of the diamond particles can be 5 μm or more, 10 μm or more, or 15 μm or more, and can also be 100 μm or less, 50 μm or less, or 20 μm or less. The maximum diameter of the diamond particles can be 5 μm or more and 100 μm or less, or 15 μm or more and 20 μm or less.

[0022] The average particle size, minimum diameter, and maximum diameter of diamond particles are calculated by image analysis of scanning electron microscope observations taken under the following conditions. Specifically, they are measured under the following conditions. Magnification: 300x or 1000x Acceleration voltage: 10kV or 3kV These values ​​can be determined by binarizing the observation images obtained from SEM observation and performing image analysis on the resulting binarized images. In image analysis, the particle size of each diamond particle can be taken as the diameter of the longest measured particle. The average particle size can be calculated from the average particle size of 100 ± 20 diamond particles. General image analysis software (e.g., ImageJ) can be used for image analysis.

[0023] The thickness of the diamond layer 20 may be, for example, 0.1 μm or more, 0.2 μm or more, or 0.4 μm or more, and may be 2000 μm or less, 1000 μm or less, or 500 μm or less.

[0024] The diamond layer 20 is preferably a diamond layer (CVD film) formed by chemical vapor deposition (CVD). Examples of chemical vapor deposition include plasma CVD and thermal filament CVD, at least one of each. Examples of plasma CVD include one or more selected from the group consisting of microwave plasma CVD, high-frequency plasma CVD, DC plasma CVD, and electric field-assisted microwave plasma CVD. The diamond layer 20 is particularly preferably a diamond layer formed by microwave plasma CVD.

[0025] (Thickness of the laminated substrate) The thickness of the laminated substrate 100 may be, for example, 10 μm or more, 50 μm or more, or 100 μm or more, and may be 10,000 μm or less, 5,000 μm or less, or 1,000 μm or less.

[0026] (Thermal conductivity of laminated substrates) The thermal conductivity of the laminated substrate 100 may be 1620 W / (m·K) or higher or 1650 W / (m·K) or higher, and may be 2000 W / (m·K) or lower or 1800 W / (m·K) or lower. Examples of thermal conductivity of the laminated substrate 100 include 1620 W / (m·K) or higher and 2000 W / (m·K) or lower, or 1640 W / (m·K) or higher and 1800 W / (m·K) or lower.

[0027] Thermal conductivity is calculated using the formula: λ = ρ·Cp·α. In this formula, λ is the thermal conductivity [W / (m·K)], and ρ is the density of the carbon substrate [g / cm³]. 3 ], Cp is the specific heat capacity [J / (g·K)], and α is the thermal diffusivity [m 2 This indicates [ / s]. Examples of measurement conditions for specific heat capacity and thermal diffusivity are described in the examples below.

[0028] (Applications of multilayer substrates) The laminated substrate 100 can be used in general applications of laminated substrates equipped with a diamond layer (diamond film). Particularly preferred applications include at least one of a heat dissipation member and a seed substrate for diamond wafer growth, and furthermore, a heat dissipation member.

[0029] <Manufacturing method for laminated substrates> The manufacturing method for the laminated substrate described herein can be any method as long as a laminated substrate 100 satisfying the above-described configuration is obtained. However, a preferred manufacturing method is one that includes a lamination step of forming a diamond layer 20 on the surface of a carbon substrate 10 by chemical vapor deposition (CVD) to obtain a laminated substrate. The CVD method is preferably a plasma CVD method, and more preferably a microwave plasma CVD method.

[0030] The carbon substrate 10 on which the diamond layer 20 is formed is preferably a graphite substrate oriented in the Z plane. This facilitates the formation of a diamond layer 20 on the surface of the carbon substrate 10, consisting of diamond particles with an average particle size within the range described above.

[0031] The lamination process can be carried out, for example, by a method that includes supplying a raw material gas (forming gas) that serves as the raw material for diamond particles into the reaction chamber of a CVD apparatus in which a carbon substrate 10 is placed, and inducing a film formation reaction to form a diamond layer 20 on the surface of the carbon substrate 10.

[0032] Examples of forming gases include a mixture of hydrogen (H2) and hydrocarbons, a mixture of hydrogen and hydrocarbons having 1 to 5 carbon atoms, and a mixture of hydrogen and at least one of methane (CH4) and ethane (C2H6), particularly a mixture of hydrogen and methane.

[0033] The concentration of hydrocarbons in the formed gas may be 0.1% by volume or more, or 1% by volume or more, and 10% by volume or less, or 5% by volume or less, based on the total volume of the formed gas (total volume of hydrogen and hydrocarbons). Examples of hydrocarbon concentrations in the formed gas include 0.1% by volume or more and 10% by volume or less, or 1% by volume or more and 5% by volume or less.

[0034] The volumetric flow rate of hydrocarbons per minute (in sccm) under standard conditions (0°C, 1 atm) may be 0.5 sccm or more, 1 sccm or more, or 2 sccm or more, and may be 100 sccm or less, 50 sccm or less, or 10 sccm or less.

[0035] The concentration of hydrogen in the formed gas does not need to be greater than the volume occupied by hydrocarbons in the formed gas, and may be 90% or more by volume, 95% or more by volume, and 99.9% or less by volume, or 99% or less by volume, based on the total volume of the formed gas (total volume of hydrogen and hydrocarbons).

[0036] The volumetric flow rate of hydrogen per minute (in sccm) under standard conditions (0°C, 1 atm) may be 50 sccm or more, 100 sccm or more, or 150 sccm or more, and may be 1000 sccm or less, 500 sccm or less, or 250 sccm or less.

[0037] The temperature (formation temperature), pressure (formation pressure), and time (formation time) used when forming the diamond layer 20 on the surface of the carbon substrate 10 can be appropriately set according to the type of carbon substrate, the method of forming the diamond layer, and so on.

[0038] The formation temperature may be, for example, 600°C or higher or 800°C or higher, 1100°C or lower or 1000°C or lower, and preferably 800°C or higher and 1000°C or lower.

[0039] The formation pressure can be any pressure at which the CVD reaction proceeds, for example, it may be 3 kPa or more, 5 kPa or more, 20 kPa or less, or 13 kPa or less. Examples of formation pressures include 3 kPa to 20 kPa or 5 kPa to 13 kPa. In this embodiment, the formation pressure is the pressure at which the diamond layer is formed and the pressure at which the formation gas is supplied.

[0040] The longer the formation time, the thicker the diamond layer tends to be. Formation times can be, for example, 1 hour or more, 4 hours or more, or 20 hours or less, or 15 hours or less. The film deposition time is the elapsed time from the start of supplying the forming gas and initiating the film deposition reaction to the stop of supplying the raw material gas and initiating the film deposition reaction. [Examples]

[0041] The present disclosure will be described below with reference to examples. However, the present disclosure is not limited to these examples.

[0042] (Tissue observation and particle size) Microstructure observation of the substrate samples was performed using a scanning electron microscope (device name: S4800, manufactured by Hitachi High-Tech Corporation) under the following conditions. Magnification: 300x or 1000x Acceleration voltage: 10kV or 3kV Prior to tissue observation, the sample substrate was cut to a size that would fit into the sample holder to prepare it as a measurement sample. The average particle size, minimum diameter, and maximum diameter were determined by performing image analysis on the binarized images obtained by binarizing the SEM observation data. Image analysis software (software name: ImageJ) was used for the image analysis.

[0043] (Specific heat capacity) The specific heat capacity of the substrate sample was measured by the DSC method under the following conditions. A DCS 8000 (manufactured by PerkinElmer) was used as the measuring instrument. Measurement sample: □4.2×1.0mm Reference sample: Sapphire Measurement temperature: 25℃ Heating rate: 20℃ / m Measurement atmosphere: Nitrogen atmosphere

[0044] (Thermal diffusivity) The thermal diffusivity of the substrate sample was measured using the flash method under the following conditions. An LFA467 (NETZSCH) was used as the measuring instrument. Measurement method: Non-contact temperature measurement using a sensor. Sample size: □5×2mm Surface treatment: None (graphite surface) Metal thin film + blackening agent coating (diamond film surface) Measurement temperature: room temperature Measurement atmosphere: Nitrogen atmosphere Analysis method: Analysis including pulse width correction and heat loss correction.

[0045] (Thermal conductivity) The thermal conductivity of the substrate sample was calculated using the following formula, based on measured values ​​of thermal diffusivity and specific heat capacity. λ = ρ·Cp·α In the above equation, λ is the thermal conductivity [W / (m·K)], and ρ is the density of the graphite substrate [2.22 g / cm³]. 3 ], Cp is the specific heat capacity [J / (g·K)], and α is the thermal diffusivity [m 2 / s]

[0046] Example 1 A highly oriented graphite substrate (2 mm thick, manufactured by Thermographics Inc.) oriented along the Z-plane was used as the substrate, and a diamond layer was formed by microwave plasma CVD under the following conditions to obtain the laminated substrate of this embodiment. Forming temperature: 950℃ Forming gases: Hydrogen 197.5 sccm, Methane 2.5 sccm Formation pressure: 10.0 kPa Formation time: 5 hours

[0047] As shown in Figure 4, the diamond layer was composed of diamond particles, with a minimum diameter of 1.0 μm, a maximum diameter of 10 μm, and an average particle size of 3.5 μm.

[0048] Example 2 The diamond layer was formed in the same manner as in Example 1, except that the film deposition time was 15 hours, to obtain the laminated substrate of this example.

[0049] The diamond layer was composed of diamond particles, with a minimum diameter of 5 μm, a maximum diameter of 16 μm, and an average particle size of 12 μm.

[0050] Comparative Example 1 A highly oriented graphite substrate (manufactured by Thermographics, Inc.), similar to that used in Example 1, was used as the substrate for this comparative example.

[0051] The evaluation results for the examples and comparative examples are shown in the table below. [Table 1]

[0052] As shown in the table above, the laminated substrate of Example 1, despite being a carbon substrate with a diamond layer on the Z-plane of a graphite substrate consisting of diamond particles with an average particle size of 1 μm or more, had the same thermal conductivity as Comparative Example 1, which was a graphite substrate only. From this, it was confirmed that in Example 1, there was no decrease in thermal conductivity due to the formation of the diamond layer. [Explanation of symbols]

[0053] 10...Carbon substrate, 10a...Graphite substrate oriented on the Z plane, 20...Diamond layer, 100...Laminated substrate, Sz...Z plane of the graphite substrate.

Claims

1. A laminated substrate comprising a carbon substrate and a diamond layer provided on the surface of the carbon substrate, the diamond layer being composed of diamond particles having an average particle size of more than 1 μm.

2. The laminated substrate according to claim 1, wherein the average particle size of the diamond particles is 2 μm or more and 100 μm or less.

3. The laminated substrate according to claim 1 or 2, wherein the carbon substrate is a graphite substrate.

4. The laminated substrate according to claim 1 or 2, wherein the carbon substrate is a graphite substrate oriented in the Z plane.

5. The laminated substrate according to claim 1 or 2, wherein the diamond layer is formed by chemical vapor deposition.

6. A laminated substrate according to claim 1 or 2, which is a heat dissipation member.

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