Metal-ceramic composite material

Abstract

This metal-ceramic composite material has a metal phase (11) and a ceramic phase (12) dispersed in a matrix comprising the metal phase (11). The thermal conductivity of the metal phase (11) is higher than the thermal conductivity of the ceramic phase (12), and the linear expansion coefficient of the ceramic phase (12) is lower than the linear expansion coefficient of the metal phase (11). The metal phase (11) has a three-dimensional network structure, and in the cross-sectional structure, the ceramic phase (12) is unevenly distributed around the metal phase (11).

Description

Metal-ceramic composite materials

[0001] The present invention relates to a metal-ceramic composite material having excellent thermal conductivity and a low coefficient of linear expansion. This application claims priority to Japanese Patent Application No. 2024-153372, filed on September 5, 2024, the contents of which are incorporated herein by reference.

[0002] BACKGROUND ART Conventionally, in plasma etching apparatuses and plasma CVD apparatuses used in semiconductor device manufacturing processes, electrostatic chuck devices such as those described in Patent Documents 1 and 2 have been used to fix silicon wafers to be processed.

[0003] This electrostatic chuck has a metal base plate and a ceramic fixed plate joined to the base plate via a bonding material, and an internal electrode is disposed between the base plate and the fixed plate. The base plate has a cooling function.

[0004] In the electrostatic chuck, a silicon wafer placed on a ceramic fixing plate is fixed by Coulomb force generated by applying a voltage to the internal electrode. In a plasma etching apparatus, a plasma CVD apparatus, or the like, the silicon wafer fixed to the electrostatic chuck is subjected to processing such as etching or film formation by CVD.

[0005] When processing a silicon wafer in a plasma etching apparatus, a plasma CVD apparatus, or the like, the temperature rise of the silicon wafer is suppressed by the cooling function of the base plate, which causes a temperature difference to be applied to the electrostatic chuck that holds the silicon wafer, and the resulting difference in thermal contraction causes distortion of the electrostatic chuck, which may result in an inability to adequately hold the silicon wafer.

[0006] Therefore, as a material that suppresses thermal contraction and has excellent thermal conductivity, a composite material of metal and ceramics has been proposed, for example, as shown in Patent Document 3. In this composite material, the ceramic suppresses thermal contraction, and the metal improves thermal conductivity.

[0007] JP 2005-085979 A JP 2013-004900 A JP 2016-079465 A

[0008] Recently, there has been a demand for more precise processing of silicon wafers. To address this, for example, cryo-etching technology has been developed, which processes silicon wafers at extremely low temperatures, for example, below -100°C, when performing hole drilling on silicon wafers by plasma etching. By applying cryo-etching technology, selective etching is dramatically improved, enabling highly accurate processing.

[0009] However, as mentioned above, cryo-etching requires extremely low temperatures, for example, below -100°C, which means that the electrostatic chuck is subjected to a larger temperature difference than ever before. Therefore, further improvement in thermal conductivity and a reduction in the linear expansion coefficient are required. However, in conventional composite materials, the ceramic phase is dispersed relatively uniformly, which can disrupt the metal phase, which serves as a heat conduction path, resulting in a risk of insufficient improvement in thermal conductivity.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a metal-ceramic composite material having a sufficiently low coefficient of linear expansion and sufficiently excellent thermal conductivity.

[0011] In order to solve the above problems, a metal-ceramic composite material according to a first aspect of the present invention comprises a metal phase and a ceramic phase dispersed in a matrix made of the metal phase, wherein the thermal conductivity of the metal phase is higher than the thermal conductivity of the ceramic phase, the linear expansion coefficient of the ceramic phase is lower than the linear expansion coefficient of the metal phase, the metal phase has a three-dimensional network structure, and in a cross-sectional structure, the ceramic phase is unevenly distributed around the metal phase.

[0012] According to the metal-ceramic composite material of the first aspect of the present invention, the composite material has a metal phase with excellent thermal conductivity and a ceramic phase with a low linear expansion coefficient, the metal phase has a three-dimensional network structure, and in the cross-sectional structure, the ceramic phase is unevenly distributed around the metal phase, ensuring a heat conduction path for the metal phase and reliably improving thermal conductivity. Furthermore, the presence of the ceramic phase sufficiently reduces the linear expansion coefficient, making it possible to suppress thermal deformation even when a temperature difference occurs.

[0013] The metal-ceramic composite material of Aspect 2 of the present invention is the metal-ceramic composite material of Aspect 1, wherein the thermal conductivity λ of the metal-ceramic composite material and the thermal conductivity λ of the metal element constituting the metal phase are ０ The ratio λ / λ ０ According to the metal-ceramic composite material of the second aspect of the present invention, the thermal conductivity λ of the metal-ceramic composite material and the thermal conductivity λ of the metal element constituting the metal phase are in the range of 0.5 or more and less than 1.0. ０ The ratio λ / λ ０ Since the value of the thermal conductivity is within the range of 0.5 or more and less than 1.0, the material has sufficiently excellent thermal conductivity and is particularly suitable as a material for components intended for heat removal.

[0014] The metal-ceramic composite material of Aspect 3 of the present invention is the metal-ceramic composite material of Aspect 1 or Aspect 2, wherein the linear expansion coefficient α of the metal-ceramic composite material and the linear expansion coefficient α of the ceramic simple substance constituting the ceramic phase are ０ The ratio α / α ０According to the metal-ceramic composite material of the third aspect of the present invention, the linear expansion coefficient α of the metal-ceramic composite material and the linear expansion coefficient α of the ceramic simple substance constituting the ceramic phase are in the range of more than 1.0 and not more than 8.0. ０ The ratio α / α ０ Since the value is in the range of more than 1.0 and not more than 8.0, thermal deformation can be suppressed even when a temperature difference occurs.

[0015] A metal-ceramic composite material of Aspect 4 of the present invention is characterized in that, in the metal-ceramic composite material of any one of Aspects 1 to 3, the area ratio of the ceramic phase in the cross-sectional structure is in the range of 15% to 45%. According to the metal-ceramic composite material of Aspect 4 of the present invention, since the area ratio of the ceramic phase in the cross-sectional structure is in the range of 15% to 45%, the coefficient of linear expansion is further reduced, and thermal deformation can be suppressed even when a temperature difference occurs.

[0016] A metal-ceramic composite material of Aspect 5 of the present invention is the metal-ceramic composite material of any one of Aspects 1 to 4, characterized in that it has a density ratio of 90% or more. Since the metal-ceramic composite material of Aspect 5 of the present invention has a density ratio of 90% or more, it has few internal voids and is excellent in strength, making it particularly suitable as a material for various components.

[0017] A metal-ceramic composite material of Aspect 6 of the present invention is the metal-ceramic composite material of any one of Aspects 1 to 5, characterized in that the volume ratio of the ceramic phase is 10% or more. According to the metal-ceramic composite material of Aspect 6 of the present invention, the volume ratio of the ceramic phase is 10% or more, so that the linear expansion coefficient can be reliably reduced.

[0018] According to an aspect of the present invention, it is possible to provide a metal-ceramic composite material having a sufficiently low coefficient of linear expansion and sufficiently excellent thermal conductivity.

[0019] 1 is a cross-sectional observation photograph showing an example of a metal-ceramic composite material according to an embodiment of the present invention. 2 is a flow diagram showing an example of a method for producing a metal-ceramic composite material according to an embodiment of the present invention.

[0020] A metal-ceramic composite material according to an embodiment of the present invention will be described below with reference to the drawings. The metal-ceramic composite material according to this embodiment is used, for example, as a material for forming an electrostatic chuck that fixes a silicon wafer in a plasma processing apparatus such as a plasma etching apparatus or a plasma CVD apparatus used in a semiconductor device manufacturing process.

[0021] As shown in Fig. 1, the metal-ceramic composite material 10 of this embodiment has a metal phase 11 and a ceramic phase 12 dispersed in a matrix made of this metal phase 11. The thermal conductivity of the metal phase 11 is higher than the thermal conductivity of the ceramic phase 12, and the linear expansion coefficient of the ceramic phase 12 is lower than the linear expansion coefficient of the metal phase 11. In the cross-sectional structure of the metal-ceramic composite material 10 of this embodiment, as shown in Fig. 1, the ceramic phase 12 is unevenly distributed around the metal phase 11. Furthermore, the metal phase 11 has a three-dimensional network structure.

[0022] Here, for example, aluminum, copper, silver, etc. can be used as the metal phase 11. In this embodiment, the metal phase 11 is made of aluminum. In addition, for example, silicon carbide (SiC), silicon nitride (SiN), silicon oxide, etc. can be used as the ceramic phase 12. In this embodiment, the ceramic phase 12 is made of silicon carbide (SiC).

[0023] In the metal-ceramic composite material 10 of this embodiment, the thermal conductivity λ of the metal-ceramic composite material 10 and the thermal conductivity λ of the metal element constituting the metal phase 11 are ０ The ratio λ / λ ０is preferably in the range of 0.5 or more and less than 1.0, and more preferably in the range of 0.6 or more and less than 1.0. Since the thermal conductivity has a temperature dependency, the ratio λ / λ ０ is the ratio of thermal conductivities under the same temperature conditions.

[0024] In this embodiment, since the metal phase 11 is made of aluminum, for example, the thermal conductivity λ of the metal alone that makes up the metal phase 11 is ０ If the ratio is 225W / (m·K), then the ratio λ / λ ０ When is 0.6 or more and less than 1.0, the thermal conductivity λ of the metal-ceramic composite material 10 is in the range of 135 W / (m·K) or more and less than 225 W / (m·K).

[0025] In this embodiment, the thermal conductivity λ of the metal-ceramic composite material 10 and the thermal conductivity λ of the metal element constituting the metal phase 11 are ０ The ratio λ / λ ０ The lower limit is more preferably 0.8 or more, and even more preferably 0.9 or more.

[0026] In the metal-ceramic composite material 10 of this embodiment, the linear expansion coefficient α of the metal-ceramic composite material 10 and the linear expansion coefficient α of the ceramic single material constituting the ceramic phase 12 are ０ The ratio α / α ０ is preferably in the range of more than 1.0 and not more than 8.0, and more preferably in the range of more than 1.0 and not more than 5.0. Since the linear expansion coefficient has temperature dependency, the ratio α / α ０ is the ratio of the linear expansion coefficients under the same temperature conditions.

[0027] In this embodiment, since the ceramic phase 12 is made of silicon carbide (SiC), for example, the linear expansion coefficient α of the ceramic alone that constitutes the ceramic phase 12 ０ is 2.3 x 10 －６ / K, the ratio α / α ０ When the coefficient of linear expansion of the metal-ceramic composite material 10 is greater than 1.0 and less than or equal to 5.0, the coefficient of linear expansion of the metal-ceramic composite material 10 is 2.3 × 10 －６ / K super 11.5×10－６ / K or less.

[0028] In this embodiment, the linear expansion coefficient α of the metal-ceramic composite material 10 and the linear expansion coefficient α of the ceramic single material constituting the ceramic phase 12 are ０ The ratio α / α ０ The lower limit of is more than 1.0, and preferably 1.5 or more. On the other hand, the linear expansion coefficient α of the metal-ceramic composite material 10 and the linear expansion coefficient α of the ceramic simple substance that constitutes the ceramic phase 12 ０ The ratio α / α ０ The upper limit of is more preferably 5.0 or less, and even more preferably 4.0 or less.

[0029] Furthermore, in the metal-ceramic composite material 10 of this embodiment, the area ratio of the ceramic phase 12 in the cross-sectional structure is preferably within the range of 15% to 45%. In this embodiment, the lower limit of the area ratio of the ceramic phase 12 in the cross-sectional structure is more preferably 30% or more, and even more preferably 32% or more. On the other hand, the upper limit of the area ratio of the ceramic phase 12 in the cross-sectional structure is more preferably 38% or less, and even more preferably 36% or less.

[0030] Furthermore, in the metal-ceramic composite material 10 of this embodiment, the density ratio is preferably 90% or more. In this embodiment, the density ratio is more preferably 95% or more. From the densities and volume ratios of the metal and ceramic used as raw materials, the density (theoretical density) when the metal and ceramic are packed without gaps is calculated. The ratio of the density of the metal-ceramic composite material to the theoretical density is defined as the density ratio.

[0031] The volume ratio of the ceramic phase 12 is preferably 10% or more, more preferably 10% to 50%, and even more preferably 20% to 50%. The volume ratio of the ceramic phase 12 is the ratio of the volume of the ceramic powder to the volume of the mixed raw material powder prepared in the manufacturing method described below.

[0032] Next, a method for producing the metal-ceramic composite material 10 according to this embodiment will be described with reference to FIG.

[0033] As shown in FIG. 2 , the method for producing the metal-ceramic composite material 10 according to this embodiment includes a metal powder preparation step S01 for preparing metal powder to become the metal phase 11, a ceramic powder preparation step S02 for preparing ceramic powder to become the ceramic phase 12, a mixing step S03 for mixing the metal powder and ceramic powder to form a mixed raw material powder, and a sintering step S04 for sintering the obtained mixed raw material powder.

[0034] Each step of the method for producing the metal-ceramic composite material 10 according to this embodiment will be described in detail below.

[0035] (Metal Powder Preparation Step S01) First, metal powder to be the metal phase 11 is prepared. As described above, it is preferable to use a metal having excellent thermal conductivity, such as aluminum, copper, silver, or an alloy thereof, as the metal powder to be the metal phase 11. Here, the average particle diameter d of the metal powder is １１ is preferably in the range of 5 μm or more and 1000 μm or less, and more preferably in the range of 10 μm or more and 200 μm or less. １１ The particle size distribution of the metal powder on a volume basis was measured by a laser diffraction scattering method, and the median diameter (D50) was taken as the average particle size.

[0036] (Ceramic powder preparation step S02) Furthermore, ceramic powder to become the ceramic phase 12 is prepared. As described above, it is preferable to use ceramics with a low linear expansion coefficient such as silicon carbide (SiC), silicon nitride (SiN), silicon oxide, etc., as the ceramic powder to become the ceramic phase 12. Here, the average particle diameter d １２ is preferably in the range of 5 μm or more and 1000 μm or less, and more preferably in the range of 10 μm or more and 200 μm or less. １２ The particle size distribution of the ceramic powder on a volume basis was measured by a laser diffraction scattering method, and the median diameter (D50) was taken as the average particle size.

[0037] (Mixing step S03) Next, the prepared metal powder and ceramic powder are weighed and mixed to a predetermined ratio to obtain a mixed raw material powder. １１ and the volume of ceramic powder V １２ The ratio V １１ / V １２ is preferably in the range of 1 or more and 9 or less, and more preferably in the range of 1 or more and 4 or less. １１ was calculated by dividing the weight of the metal powder by the theoretical density of the bulk material of the metal powder. １２ was calculated by dividing the weight of the ceramic powder by the theoretical density of the bulk material of the ceramic powder.

[0038] The mixing method is not particularly limited and may be appropriately selected from existing mixing methods. In this embodiment, mixing is preferably carried out using a grinding / mixing device such as a ball mill, basket mill, or bead mill.

[0039] (Sintering Step S04) Next, the mixed raw material powder is filled into a molding container and sintered by heating and pressure to obtain a sintered body. In this embodiment, sintering is performed by hot pressing (HP). The sintering temperature in this sintering step S04 is in the range of 500°C to 630°C, and the holding time at the sintering temperature is in the range of 30 to 240 minutes. The pressing pressure in the sintering step S04 is 20 MPa or more. The upper limit of the pressing pressure in the sintering step S04 is preferably 40 MPa or less. Here, in this embodiment, the sintering temperature is preferably 550°C or more, more preferably 570°C or more. The sintering temperature is preferably 610°C or less, more preferably 600°C or less. The holding time at the sintering temperature is preferably 60 minutes or more, more preferably 120 minutes or more. The holding time at the sintering temperature is preferably 200 minutes or less, more preferably 180 minutes. Furthermore, the pressure is preferably 30 MPa or more, and more preferably 35 MPa or more.

[0040] (Processing Step S05) Next, the obtained sintered body is machined to obtain a metal-ceramic composite material 10 of a predetermined size.

[0041] Through the above steps, the metal-ceramic composite material 10 of this embodiment is manufactured.

[0042] The metal-ceramic composite material 10 of this embodiment configured as described above has a metal phase 11 with excellent thermal conductivity and a ceramic phase 12 with a low linear expansion coefficient, and the metal phase 11 has a three-dimensional network structure, and the ceramic phase 12 is unevenly distributed around the metal phase 11 in the cross-sectional structure, ensuring a heat conduction path for the metal phase 11 and reliably improving thermal conductivity. Furthermore, the presence of the ceramic phase 12 sufficiently reduces the linear expansion coefficient, making it possible to suppress thermal deformation even when a temperature difference occurs.

[0043] In the metal-ceramic composite material 10 of this embodiment, the thermal conductivity λ of the metal-ceramic composite material 10 and the thermal conductivity λ of the metal element constituting the metal phase 11 are ０ The ratio λ / λ ０ When the ratio is in the range of 0.5 or more and less than 1.0, the thermal conductivity is sufficiently excellent and the material can be suitably used as a material for a member intended for heat removal.

[0044] Furthermore, in the metal-ceramic composite material 10 of this embodiment, the linear expansion coefficient α of the metal-ceramic composite material 10 and the linear expansion coefficient α of the ceramic single material constituting the ceramic phase 12 are ０ The ratio α / α ０ When the coefficient of linear expansion is in the range of more than 1.0 and not more than 8.0, the coefficient of linear expansion is kept sufficiently low, and thermal deformation can be suppressed even when a temperature difference occurs.

[0045] Furthermore, in the metal-ceramic composite material 10 of this embodiment, when the area ratio of the ceramic phase 12 in the cross-sectional structure is within the range of 15% or more and 45% or less, the linear expansion coefficient is further reduced, and thermal deformation can be further suppressed even when a temperature difference occurs.

[0046] Furthermore, in the metal-ceramic composite material 10 of this embodiment, when the density ratio is 90% or more, there are few voids inside, and the strength is excellent, making it particularly suitable as a material for various components.

[0047] Although the present invention has been described above as an embodiment, it is not limited thereto and can be modified as appropriate within the scope of the technical requirements of the invention. In this embodiment, the present invention has been described as being used as a material for constituting an electrostatic chuck that fixes a silicon wafer in a plasma processing apparatus, but the present invention is not limited thereto and may be used for other purposes.

[0048] The results of confirmation experiments conducted to confirm the effectiveness of the present invention will be described below.

[0049] The metal powders and ceramic powders shown in Table 1 were prepared, weighed out to obtain the ratios shown in Table 1, and mixed using a ball mill (media: zirconia balls) for 3 hours at a rotation speed of 97 rpm to obtain a mixed raw material powder. The obtained mixed raw material powder was sintered by the HP method under the conditions of a temperature of 580°C, a time of 120 minutes, a pressure load of 35 MPa, and a vacuum atmosphere to obtain metal-ceramic composite materials of the present invention and comparative examples.

[0050] The obtained metal-ceramic composite materials were evaluated for the presence or absence of a three-dimensional network structure of the metal phase, the area ratio of the ceramic phase, the density ratio, the thermal conductivity, and the linear expansion coefficient as follows.

[0051] (Presence or absence of a three-dimensional network structure of the metal phase) Observation samples were cut out from the metal-ceramic composite material, and the structure was observed from three mutually perpendicular directions, the X direction, the Y direction, and the Z direction. If it was observed that the ceramic phase was unevenly distributed around the metal phase and that the metal phase was connected, it was evaluated as "○" (good), and if not, it was evaluated as "×" (poor). The evaluation results are shown in Table 2.

[0052] (Area ratio of ceramic phase) An observation sample was cut out from the metal-ceramic composite material, and an image was taken using a scanning electron microscope (SEM) at a magnification of 500 times. The captured image was analyzed to measure the area of ​​the ceramic phase. The area of ​​the ceramic phase was then divided by the area of ​​the measured field of view to calculate the area ratio of the ceramic phase. This procedure was performed three times, and the average values ​​are shown in Table 2.

[0053] (Density Ratio) A measurement sample (35 mm × 35 mm × 2 mm (thickness t)) was cut out from the metal-ceramic composite material, and its weight was measured to calculate the density. The density ratio was then calculated by dividing the calculated density by the theoretical density. In Table 2, a density ratio of 90% or more is represented as "○" (good), and a density ratio of less than 90% is represented as "×" (poor). The theoretical density was calculated by calculating the density when the metals and ceramics used as raw materials were packed together without gaps from the density and volume ratio.

[0054] (Thermal Conductivity) Measurement samples cut out from the metal-ceramic composite material and measurement samples of the simple metals that make up the metal phase were prepared, and the thermal conductivity of these was measured under the following conditions: measurement temperature: 25°C, Xe lamp voltage: 230V, light pulse width: 300 μsec, standard comparison sample for specific heat measurement: SUS310 (10 mm × 10 mm × 2 mm (thickness t)). Table 2 shows the thermal conductivity λ of the metal-ceramic composite material and the thermal conductivity λ of the simple metals that make up the metal phase. ０ The ratio λ / λ ０ is in the range of 0.5 or more and less than 1.0, it is "○" (good), and the ratio λ / λ ０ When the value was outside the range of 0.5 or more and less than 1.0, it was marked as "x" (poor).

[0055] (Linear expansion coefficient) Measurement samples cut out from the metal-ceramic composite material and measurement samples of the ceramics alone that constitute the ceramic phase were prepared, and the linear expansion coefficients of these were measured under the following conditions: temperature program: temperature increase rate 10°C / min from 30°C to 500°C, atmosphere: Ar (G2 grade), standard sample: alumina, load 10 g. Table 2 shows the linear expansion coefficient α of the measurement sample cut out from the metal-ceramic composite material when the temperature changes from 30°C to 40°C, and the linear expansion coefficient α of the ceramics alone that constitute the ceramic phase when the temperature changes from 30°C to 40°C. ０ The ratio α / α ０ is in the range of more than 1.0 and not more than 8.0, it is "○" (good), the ratio α / α ０ When the value was outside the range of more than 1.0 and not more than 8.0, it was marked as "x" (poor).

[0056]

[0057]

[0058] In Comparative Example 1, the metal phase did not have a three-dimensional network structure and the area ratio of the ceramic phase was low, so the linear expansion coefficient was not sufficiently low. In Comparative Example 2, the metal phase did not have a three-dimensional network structure and the area ratio of the ceramic phase was high, so the thermal conductivity was not sufficiently high. In Comparative Example 3, the density ratio was low, so a metal-ceramic composite material could not be produced well, and the linear expansion coefficient and thermal conductivity could not be measured. In Comparative Example 4, the metal phase did not have a three-dimensional network structure and the thermal conductivity was not sufficiently high.

[0059] In contrast, in Examples 1 to 8 of the present invention, the metal phase had a three-dimensional network structure, ensuring a heat conduction path for the metal phase and resulting in excellent thermal conductivity. In addition, the presence of the ceramic phase resulted in a sufficiently low linear expansion coefficient.

[0060] As a result of the above, it was confirmed that the present invention can provide a metal-ceramic composite material having a sufficiently low coefficient of linear expansion and sufficiently excellent thermal conductivity.

[0061] The metal-ceramic composite material of this embodiment is suitably used as a material for forming an electrostatic chuck for fixing a silicon wafer in a plasma processing apparatus such as a plasma etching apparatus or a plasma CVD apparatus.

[0062] 10 Metal-ceramic composite 11 Metal phase 12 Ceramic phase.

Claims

1. A metal-ceramic composite material comprising a metal phase and a ceramic phase dispersed within a matrix made of said metal phase, wherein the thermal conductivity of said metal phase is higher than the thermal conductivity of said ceramic phase and the linear expansion coefficient of said ceramic phase is lower than the linear expansion coefficient of said metal phase, said metal phase has a three-dimensional network structure, and in a cross-sectional structure, said ceramic phase is unevenly distributed around the metal phase.

2. The thermal conductivity λ of the metal-ceramic composite material and the thermal conductivity λ of the metal element that constitutes the metal phase ０ The ratio λ / λ ０ 2. The metal-ceramic composite material according to claim 1, wherein the value of σ is in the range of 0.5 or more and less than 1.

0.

3. The linear expansion coefficient α of the metal-ceramic composite material and the linear expansion coefficient α of the ceramic single material that constitutes the ceramic phase ０ The ratio α / α ０ The metal-ceramic composite material according to claim 1, characterized in that the value of the tensile strength is in the range of more than 1.0 and not more than 8.

0.

4. The metal-ceramic composite material according to claim 1, wherein the area ratio of the ceramic phase in the cross-sectional structure is within the range of 15% to 45%.

5. The metal-ceramic composite material according to claim 1, characterized in that the density ratio is 90% or more.

6. The metal-ceramic composite material according to claim 1, wherein the volume ratio of the ceramic phase is 10% or more.

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