JP7829064B2 - Vacuum chuck and method for manufacturing the same - Google Patents

Description

This disclosure relates to a vacuum chuck and a method for manufacturing the same.

Conventionally, as a device for fixing objects to be adsorbed, such as semiconductor wafers, adsorption members such as those described in Patent Document 1 have been used. The adsorption member described in Patent Document 1 comprises an adsorbent and a support that supports the adsorbent. The adsorbent has a substrate made of porous ceramic and a semiconducting first coating film located on the surface of the substrate facing the object to be adsorbed. Furthermore, Patent Document 1 discloses that the support surface may have a second coating film made of the same material as the first coating film, connected to the first coating film, and the second coating film may cover the upper surface, outer surface, and lower surface of the support. With such a configuration, generated static electricity can be removed at an appropriate speed.

Japanese Patent Publication No. 2018-200972

The vacuum chuck according to this disclosure includes a plate-shaped ceramic porous body having a first surface which is the mounting surface side and pores communicating in the thickness direction, a support portion having an annular second surface located so as to surround the first surface, a first film having permeability and semiconductivity, and a second film having lower resistance than the first film. At least one of the support portion and the second film is not permeable. The first film covers from the first surface to the second surface. The second film covers at least the first film and the side surface of the support portion located on the second surface.

A method for manufacturing a vacuum chuck according to this disclosure includes the steps of: preparing a ceramic porous body having an upper surface, a lower surface, and side surfaces, and having pores communicating in the thickness direction; forming a first surface and an annular second surface located on the periphery of the upper surface so as to surround the first surface on the upper surface of the ceramic porous body; coating the first surface and the second surface with a first film having permeability and semiconductivity; coating at least the first film located on the second surface and the side surfaces of the ceramic porous body with a second film that has lower resistance than the first film and does not have permeability; and grinding the first film and the second film simultaneously to make the first film and the second film substantially flush.

Another method for manufacturing a vacuum chuck according to this disclosure includes the steps of: preparing a plate-shaped ceramic porous body having pores communicating in the thickness direction and a ceramic dense body having a recess for housing the ceramic porous body; joining the ceramic porous body to the recess and processing the ceramic porous body and the ceramic dense body so that they are substantially flush, thereby forming a first surface on the upper surface of the ceramic porous body; forming a third surface on the ceramic dense body that surrounds the recess, connects to the wall surface of the recess and is substantially flush with the first surface, and a second surface that surrounds the third surface and is located on the outer peripheral edge of the third surface; coating the first surface and the second surface with a first film that is permeable and semiconductive; coating at least the side surfaces of the first film and the ceramic dense body located on the second surface with a second film that has lower resistance than the first film; and grinding the first film and the second film simultaneously so that they are substantially flush.

This is a cross-sectional view showing a vacuum chuck according to one embodiment of the present disclosure. This is an enlarged diagram illustrating a modified example of region X shown in Figure 1. This is a cross-sectional view showing a vacuum chuck according to another embodiment of the present disclosure. This is an enlarged diagram illustrating a modified example of region Y shown in Figure 3. Figure 1 is a perspective view of the vacuum chuck.

In recent years, there has been a demand for adsorption materials that can more efficiently remove generated static electricity. To avoid sparks caused by rapid discharge upon contact with the object being adsorbed, the coating needs to be semiconductive. However, increasing the resistivity of the coating makes it more susceptible to static charge, while decreasing its resistivity increases the likelihood of sparks. Therefore, there is a need for a vacuum chuck that efficiently removes generated static electricity and reduces the occurrence of sparks.

The vacuum chuck according to this disclosure has a configuration as described in the section on means for solving the above problems, thereby efficiently removing generated static electricity and reducing the generation of sparks. Furthermore, the manufacturing method of the vacuum chuck according to this disclosure can provide a vacuum chuck in which generated static electricity is efficiently removed and the generation of sparks is reduced.

The vacuum chuck according to this disclosure includes, as described above, a ceramic porous body, a support portion, a first film, and a second film. The vacuum chuck according to this disclosure will be described with reference to Figures 1 to 5.

As shown in Figure 1, a vacuum chuck 10 according to one embodiment of the present disclosure has a structure in which a porous, integrally molded product 3, in which a ceramic porous body 1 and a support part 2 are integrated, is placed in contact with a base material 4. Figure 1 is a cross-sectional view showing a vacuum chuck 10 according to one embodiment of the present disclosure. The external appearance of the vacuum chuck 10 is shown in Figure 5. Figure 5 is a perspective view of a vacuum chuck 10 according to one embodiment of the present disclosure.

The ceramic porous body 1 is plate-shaped having a first surface 1a which is the mounting surface, and is not limited as long as it is made of porous ceramic. Examples of ceramics forming the ceramic porous body 1 include oxides such as aluminum oxide (alumina), titanium oxide and zinc oxide, carbides such as silicon carbide, and nitrides such as silicon nitride, boron nitride and aluminum nitride. "Porous" generally means having a certain degree of pores within an object. However, in this specification, "porous" means having pores to the extent that the pores are interconnected and allow for permeability.

In other words, an object that has interconnected pores and is permeable is defined as a "porous material." Generally, "permeable" means having the property of being able to pass gas through. However, in this specification, "permeable" means having enough permeability to allow an object to be adsorbed, such as a substrate, to be adsorbed and held on the surface when the back surface of the porous material is sucked by a vacuum pump. When the bottom surface is sucked by connecting a suction tube to a vacuum pump, the pressure difference (pressure loss) between the atmospheric pressure inside the suction tube and the porous material may be 90 kPa or less. An object that does not have interconnected pores and is airtight is defined as a dense material. A dense material will be permeable if pores are formed through processing or other means.

The ceramic porous body 1 has, for example, a porosity of 10% to 50%, an average pore diameter of 20 μm to 100 μm, and an average particle size of 50 μm to 300 μm. If the porosity and pore diameter are within this range, the adsorption strength can be improved while balancing the strength and rigidity of the member with the air permeability resistance.

Porosity and pore size values can be determined, for example, by cutting a suitable size section of the material to be measured and using the mercury intrusion method in accordance with JIS R 1655-2003. Alternatively, they can be determined by observing an arbitrary cross-section of the material to be measured with an electron microscope or optical microscope and processing the observed image. Porosity of porous materials is best measured by the mercury intrusion method, while porosity of dense materials is best measured by cross-sectional observation.

The porosity (closed porosity) of a dense material is measured by the following method. First, the surface obtained by mirror-polishing the cross-section of the ceramic is observed at 500x magnification. Specifically, polishing is performed using the following procedure.
(1) First polishing: Polishing with a diamond disc using diamond abrasive grains with an average particle size D ₅₀ of 45 μm.
(2) Second polishing: Polishing with a copper plate using diamond abrasive grains with an average particle size D ₅₀ of 3 μm.
(3) Third polishing: Polishing with a tin plate using diamond abrasive grains with an average particle size D ₅₀ of 0.5 μm.

From the observed surface, an average area is selected, for example, an area with an area of 1.06 × ^{10⁶ μm²} (horizontal length 1190 μm, vertical length 890 μm), and this area is photographed with a scanning electron microscope to obtain an observation image at 100x magnification. Using this observation image, the area ratio of closed pores can be determined using particle analysis with the image analysis software "A-zo-kun (ver2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.). Hereafter, when the image analysis software "A-zo-kun" is mentioned, it refers to the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.

The settings for this method include, for example, setting the threshold value (an indicator of brightness in the image) to 91, the brightness to dark, the small figure removal area to 1 ^μm² , and enabling the noise reduction filter. The threshold value should be adjusted according to the brightness of the observed image. Alternatively, with the brightness set to dark, the binarization method to manual, the small figure removal area to 1 ^μm² , and the noise reduction filter enabled, the threshold value should be adjusted so that the markers appearing in the observed image match the shape of the closed pores.

Among these ceramics, the ceramic forming the porous ceramic body 1 is preferably a ceramic mainly composed of alumina. In this specification, "main component" means a component that is present in a proportion of 50% by mass or more when the total components constituting the ceramic are considered to be 100% by mass. The identification of each component contained in the ceramic can be performed, for example, by an X-ray diffractometer using CuKα rays. The content of each component can be determined, for example, by an ICP (Inductively Coupled Plasma) emission spectrometer or an X-ray fluorescence analyzer.

The shape and size of the ceramic porous body 1 are not limited and are appropriately set according to the intended use of the resulting vacuum chuck 10 or the shape of the object to be adsorbed. For example, the ceramic porous body 1 may have a circular, elliptical, or polygonal shape (triangular, quadrilateral, pentagonal, and hexagonal, etc.) when viewed from above. In the case of a polygonal shape, the shape of the ceramic porous body 1 may be a regular polygon or an irregular polygon.

The size of the ceramic porous body 1 is not limited; for example, its diameter may be between 50 mm and 500 mm. If the ceramic porous body 1 is elliptical, both its major and minor axes may be within this range. If the ceramic porous body 1 is polygonal, the length of one side may be, for example, between 50 mm and 500 mm. The thickness of the ceramic porous body 1 may be, for example, between 10 mm and 50 mm.

The support portion 2 is a member that supports the ceramic porous body 1. As shown in Figure 1, the support portion 2 has an annular second surface 2a that surrounds the first surface 1a of the ceramic porous body 1. The support portion 2 is not limited in shape and size as long as it can support the ceramic porous body 1. Furthermore, the material and raw materials of the support portion 2 are not limited; for example, it may be made of ceramics with the same main component as the ceramic porous body 1. If they are made of the same ceramics, the difference in thermal expansion coefficients will be small. Therefore, deformation when heat is applied will be small.

As shown in Figure 1, when using an integrally molded product 3 in which a ceramic porous body 1 and a support part 2 are integrated, the ceramic porous body 1 and the support part 2 are formed from the same raw material. In the integrally molded product 3, the boundary between the ceramic porous body 1 and the support part 2 is the second surface 2a. The portion located above the second surface 2a corresponds to the ceramic porous body 1, and the portion located below the second surface 2a corresponds to the support part 2. The integrally molded product 3 may be placed on a dense substrate 4. Specifically, as shown in Figure 1, the integrally molded product 3 is placed on the substrate 4 such that the surface opposite to the first surface 1a is in contact with the substrate 4. Examples of the substrate 4 include dense ceramics.

As shown in Figures 1 and 5, the first film 6 is positioned to cover the area from the first surface 1a of the ceramic porous body 1 to the second surface 2a of the support portion 2. Specifically in Figure 1, the first film 6 is positioned to cover the surface (first surface 1a, first side surface 81, and second surface 2a) of the integrally molded product 3. The first film 6 is permeable and semiconductive. In this specification, "semiconductive" means that the resistance value is between 1E+0.5Ω and 1E+10Ω. The object to be placed needs to be adsorbed onto the first surface 1a of the ceramic porous body 1 by suction from the suction hole 5. Therefore, the first film 6 needs to be permeable.

Furthermore, the second film 7 is positioned to cover at least the first film 6 located on the second surface 2a and the side surface (third side surface 83) of the support portion 2. The second film 7 has lower resistance than the first film 6 and is an impermeable film.

By using a semiconducting first film 6, the generation of sparks is reduced. By using a second film 7 with lower resistance than the first film 6, the generated static electricity is efficiently removed. Furthermore, because the first film 6 and the second film 7 overlap and are in contact on the second surface 2a, good electrical connection is achieved. A good connection can be obtained if the width of the overlapping portion between the first film 6 and the second film 7 is, for example, 1 mm or more. If both the first film 6 and the second film 7 are semiconducting films, it becomes difficult to quickly remove the generated static electricity. On the other hand, if both the first film 6 and the second film 7 are low-resistance films, it becomes difficult to reduce the generation of sparks.

The first film 6 is not limited to films that are permeable and semiconductive, and examples include films made of ceramics and resins. Among these, the first film 6 is preferably a film made of ceramics. Films made of ceramics have a small difference in thermal expansion with the ceramic porous body 1, and are less prone to deformation and stress when the temperature changes. Furthermore, films made of ceramics have good processing accuracy, and it is easy to obtain an adsorption surface with good flatness. Examples of films made of ceramics include films mainly composed of alumina, titanium oxide, zinc oxide, silicon carbide, diamond-like carbon, silicon nitride, boron nitride, and aluminum nitride.

The first film 6 is particularly preferable if its main component is the same as that of the ceramic porous body 1, because this reduces the difference in thermal expansion (deformation and stress during temperature changes). If the main component of the ceramic porous body 1 is alumina, then the first film 6 is preferably formed of a ceramic whose main component is alumina and which also contains at least one of titanium oxide and zinc oxide.

The resistivity of the first film 6 can be adjusted by the content of titanium dioxide and zinc oxide relative to the alumina. A higher content of titanium dioxide and zinc oxide results in a lower resistivity film. The resistivity of the first film 6 is preferably in the range of 1E+0.5Ω to 1E+10Ω, and the content of titanium dioxide and zinc oxide should be adjusted so that the resistivity falls within this range.

When the first film 6 is formed of ceramic, the first film 6 may be a ceramic thermal spray film. Thermal spraying can be performed at relatively low temperatures, has low thermal stress, and allows for relatively easy thickening of the film (leaving a uniform film even after surface processing). Examples of ceramic films that can be produced by thermal spraying include alumina, titanium oxide, and zinc oxide.

When the porous ceramic body 1 is formed from a ceramic mainly composed of alumina, and the first film 6 is formed from a ceramic containing alumina and at least one of titanium oxide and zinc oxide, the difference in physical properties (thermal expansion coefficient, Young's modulus, etc.) between the components is small. Therefore, thermal stress is reduced, and processing accuracy such as flatness is improved.

The second film 7 is not limited as long as it has lower resistance than the first film 6. If the support part 2 is porous, the second film 7 can be any film that does not allow air to pass through. The second film 7 can be made of, for example, ceramic, resin, or metal. Among these, the second film 7 is preferably made of ceramic. Examples of films made of ceramic include films made from titanium oxide, zinc oxide, lead oxide, alumina, and diamond-like carbon. In particular, the second film 7 is preferably made of ceramic containing titanium oxide as the main component. When the second film 7 is made of ceramic containing titanium oxide as the main component, it has high conductivity and can quickly remove generated static electricity. The resistance of the second film 7 may be, for example, 20 Ω or less.

If the main components of the first film 6 and the second film 7 are the same, for example, if the main component is alumina, it is preferable to adjust the second film 7 so that it contains a larger amount of the component added for conductivity control than the first film 6. If the main component is diamond-like carbon, it is preferable to make the second film 7 a film with a higher ratio of, for example, SP2 bonds than the first film 6.

If the second film 7 is formed of ceramic, the second film 7 may also be a ceramic thermal spray film. The second film 7 may be denser and thicker than the first film 6. If the second film 7 is denser and thicker than the first film 6, the conductivity will be higher. As a result, the generated static electricity will be removed more quickly. The first film 6 needs to be permeable. The first film 6 may be porous or dense as long as it is not thick enough to block the communicating pores that open on the first surface 1a of the ceramic porous body 1. The first film 6 may have a thickness of, for example, 10 μm or more and 200 μm or less. The second film 7 is preferably dense. The second film 7 may have a thickness of, for example, 100 μm or more and 2 mm or less, and a closed porosity of 10 area % or less.

The colors of the first film 6 and the second film 7 are not limited and may be achromatic colors such as white, black, and gray, or chromatic colors. The first film 6 and the second film 7 may have the same color or different colors. For example, if the first film 6 and the second film 7 have different colors, the outline of the first film 6 becomes clearer. As a result, when placing an object on the mounting surface (first surface 1a), it can be placed only on the first film 6 or on the second film 7 as well.

If the first film 6 is formed of a ceramic containing, for example, alumina and at least one of titanium oxide and zinc oxide , the color and resistivity of the first film 6 can be adjusted by the content of titanium oxide and zinc oxide. By including titanium oxide in a proportion of 30% to 50% by mass, a black, semiconducting first film 6 is formed. Therefore, when a white object is placed on it, the outline of the object can be clearly defined. On the other hand, by including zinc oxide in a proportion of 30% to 50% by mass, a white, semiconducting first film 6 is formed. Therefore, when a black object is placed on it, the outline of the object can be clearly defined.

Both titanium dioxide and zinc oxide impart semiconductivity to alumina. Therefore, by including them in the proportions described above, spark generation is reduced more efficiently. When titanium dioxide and zinc oxide are included in a total proportion of 30% to 50% by mass, a gray, semiconductive first film 6 is formed. Therefore, the outline of the object can be clearly defined whether a black or white object is placed on it.

As shown in Figure 1, the second surface 2a may be located lower than the first surface 1a. When the second surface 2a is located lower than the first surface 1a, sufficient thickness can be ensured for the first film 6 and the second film 7 that overlap on the second surface 2a. As a result, one of the films does not become too thin, and the electrical connection between the first film 6 and the second film 7 can be improved. The height from the second surface 2a to the first surface 1a is, for example, 50 μm or more.

Furthermore, the second film 7 located on the second surface 2a may be flush with the first film 6 located on the first surface 1a, or it may be located in a lower position than the first film 6 located on the first surface 1a. If the second film 7 located on the second surface 2a is flush with the first film 6 located on the first surface 1a, it becomes possible to achieve high flatness by lapping. On the other hand, if the second film 7 located on the second surface 2a is located in a lower position than the first film 6 located on the first surface 1a, it becomes less likely for the object to come into contact with the second film 7 when an object is placed on it. As a result, the generation of sparks is reduced more efficiently.

In a vacuum chuck 10 according to one embodiment, the first side surface 81 located between the first surface 1a and the second surface 2a may be substantially perpendicular to the first surface 1a and the second surface 2a, as shown in Figure 1, or it may be inclined outward from the first surface 1a to the second surface 2a, as shown in Figure 2. Figure 2 is an enlarged explanatory diagram for illustrating a modified example of the region X shown in Figure 1. In particular, when the first side surface 81 is inclined outward from the first surface 1a to the second surface 2a, the first film 6 bends gently rather than bends vertically. Therefore, the risk of breakage of the first film 6 is further reduced.

The corner C1 formed by the first surface 1a and the first side surface 81 may be approximately perpendicular to the first surface 1a and the second surface 2a, as shown in Figure 1, or it may be chamfered, as shown in Figure 2. In particular, if the corner C1 is chamfered, the first film 6 bends gently rather than bends perpendicularly. Therefore, the risk of breakage of the first film 6 is further reduced.

The corner C2 formed by the second surface 2a and the third surface 83, which is the outer surface of the support portion 2, may be approximately perpendicular to the second surface 2a, as shown in Figure 1, or it may be chamfered, as shown in Figure 2. In particular, if the corner C2 is chamfered, the second film 7 will bend gently at the corner C2 instead of bending vertically. Therefore, the risk of breakage of the second film 7 is further reduced.

The second surface 2a may be approximately horizontal to the first surface 1a, as shown in Figure 1, or it may be inclined to be lower towards the outside, as shown in Figure 2. In particular, if the second surface 2a is inclined to be lower towards the outside, the total thickness of the first film 6 and the second film 7 becomes larger towards the outer periphery (third side surface 83). As a result, the peeling of the first film 6 and the second film 7 from the third side surface 83 can be reduced. Furthermore, the bending of the second film 7 becomes gentler, and the breakage of the second film 7 is further reduced.

Next, a vacuum chuck according to another embodiment of the present disclosure will be described with reference to Figures 3 and 4. As shown in Figure 3, in the vacuum chuck 20 according to the other embodiment, the ceramic porous body 1 and the support part 2 are made of different materials. That is, the support part 2 is made of a ceramic dense body 21. Figure 3 is a cross-sectional view showing the vacuum chuck 20 according to the other embodiment of the present disclosure. The same reference numerals as in the vacuum chuck 10 according to one embodiment are used, and detailed explanations are omitted.

The dense ceramic body 21 is superior to porous ceramics in terms of mechanical strength, thermal conductivity, and airtightness. The dense ceramic body 21 is not limited as long as it is formed of dense ceramic. Examples of ceramics forming the dense ceramic body 21 include oxides such as aluminum oxide (alumina), titanium oxide, and zinc oxide, carbides such as silicon carbide, and nitrides such as silicon nitride, boron nitride, and aluminum nitride. The closed porosity of the dense ceramic body 21 is, for example, 10 area percent or less.

The dense ceramic body 21 may be formed from the same raw materials as the porous ceramic body 1. For example, if the porous ceramic body 1 is formed from a ceramic mainly composed of alumina, the dense ceramic body 21 may also be formed from a ceramic mainly composed of alumina.

The shape and size of the dense ceramic body 21 are not limited and are appropriately set according to the intended use of the resulting vacuum chuck 20 and the shape of the porous ceramic body 1. The shape of the dense ceramic body 21 is not limited. For example, when viewed from above, the dense ceramic body 21 may have a circular, elliptical, or polygonal shape (triangular, quadrilateral, pentagonal, and hexagonal, etc.). In the case of a polygonal shape, the shape of the dense ceramic body 21 may be a regular polygon or an irregular polygon.

The dense ceramic body 21 has recesses 211 for accommodating the porous ceramic body 1. The recesses 211 are formed according to the shape and size of the porous ceramic body 1. The third surface 2b, which connects to the wall surface of the recess 211, is positioned substantially flush with the first surface 1a, as shown in Figure 3. "Substantially flush" includes cases where the first surface 1a and the third surface 2b are not perfectly flush, but there is a difference of 100 μm or less between them.

In the vacuum chuck 20 according to another embodiment, the second surface 2a is located on the outer peripheral edge side of the third surface 2b, as shown in Figure 3. The height from the second surface 2a to the third surface 2b is, for example, 500 μm or more.

In the vacuum chuck 20 according to another embodiment, the second side surface 82 located between the third surface 2b and the second surface 2a may be substantially perpendicular to the third surface 2b and the second surface 2a, as shown in Figure 3, or it may be inclined outward from the third surface 2b to the second surface 2a, as shown in Figure 4. Figure 4 is an enlarged explanatory diagram illustrating a modified example of region Y shown in Figure 3. In particular, when the second side surface 82 is inclined outward from the third surface 2b to the second surface 2a, the first film 6 bends gently rather than vertically. As a result, the risk of breakage of the first film 6 is further reduced.

The corner C3 formed by the third surface 2b and the second surface 82 may be approximately perpendicular to the third surface 2b and the second surface 2a, as shown in Figure 3, or it may be chamfered, as shown in Figure 4. In particular, if the corner C3 is chamfered, the first film 6 bends gently rather than bends perpendicularly. Therefore, the risk of breakage of the first film 6 is further reduced.

As shown in Figures 1 and 3, the vacuum chucks 10 and 20 have suction holes 5. The suction holes 5 have openings on the side of the vacuum chucks 10 and 20 opposite to the first surface 1a on which the object is placed, and penetrate to the lower surface of the ceramic porous body 1 or the lower surface of the support portion 2 made of the porous body. The suction holes 5 are connected to a suction source (not shown), such as a vacuum pump. When the suction source is activated, the suction holes 5 become a path for drawing in air, which then adsorbs and holds the object placed on them via the ceramic porous body 1 (first surface 1a).

Next, a method for manufacturing the adsorption member of the present disclosure will be described. A method for manufacturing a vacuum chuck 10 according to one embodiment of the present disclosure includes the following steps (a) to (e).
(a) A step of preparing a ceramic porous body having an upper surface, a lower surface, and side surfaces.
(b) A step of forming a first surface and an annular second surface located on the periphery of the upper surface so as to surround the first surface on the upper surface of the porous ceramic body.
(c) A step of coating the surface from the first surface to the second surface with a first film that is breathable and semiconductive.
(d) A step of coating the first film and the sides of the ceramic porous body, which are located on at least the second surface, with a second film that has lower resistance than the first film and is not permeable.
(e) A step of grinding the first film and the second film simultaneously to make the first film and the second film substantially flush.

Step (a) is the step of preparing a ceramic porous body having a top surface, a bottom surface, and side surfaces. As shown in Figure 1, this ceramic porous body is processed into an integral molded product 3 in which the ceramic porous body 1 and the support part 2 are integrated. The ceramic forming the ceramic porous body is the same as the ceramic forming the ceramic porous body 1, so a detailed explanation is omitted. Below, an example of a method for manufacturing a ceramic porous body containing alumina as the main component will be described.

First, aluminum oxide powder with an average particle size _D50 of 50 μm to 250 μm, glass powder with an average particle size _D50 of 4 μm to 40 μm, water, and a binder are mixed. The ratio of glass powder to 100 parts by mass of aluminum oxide powder is 5 parts by mass to 10 parts by mass. The glass powder becomes a glass component that binds the crystalline particles of aluminum oxide that form a ceramic porous body through the heat treatment described later, and its softening point is 750°C to 940°C. The proportion of water is 5 parts by mass to 10 parts by mass per 100 parts by mass of the total of aluminum oxide powder and glass powder. Other polar solvents may be used instead of water.

Granules are obtained by granulating a mixture of aluminum oxide powder and glass powder using various granulating machines such as a rolling granulator, spray dryer, compression granulator, and extrusion granulator.

Next, the obtained granules are filled into a mold and molded under hydrostatic pressure. The resulting molded body is then heat-treated, for example, in an air atmosphere or a nitrogen atmosphere at a temperature of 900°C to 1300°C to obtain a porous ceramic body.

Step (b) is a step in which a first surface 1a and an annular second surface 2a located on the periphery of the upper surface of the ceramic porous body obtained in step (a) are formed on the upper surface of the ceramic porous body obtained in step (a). As shown in Figure 1, the second surface 2a is preferably formed in a lower part than the first surface 1a. For example, the periphery of the upper surface of the ceramic porous body can be removed by cutting or grinding.

As shown in Figure 2, when forming the second surface 2a, the first side surface 81 located between the first surface 1a and the second surface 2a may be processed to incline outward as needed. The second surface 2a may also be processed to incline so that it becomes lower towards the outside. Furthermore, the corner C1 formed between the first surface 1a and the first side surface 81 located between the first surface 1a and the second surface 2a may be subjected to chamfering. The corner C2 formed between the second surface 2a and the third side surface 83, which is the outer surface of the support part 2 (integrated molded product 3), may also be subjected to chamfering.

Step (c) is a step of coating the surface from the first surface 1a to the second surface 2a with a first film 6 that is permeable and semiconductive. The first film 6 is as described above, so a detailed explanation will be omitted. Below, an example using plasma spraying as the method for producing the first film 6 containing alumina and titanium oxide will be described.

A ceramic porous body 1 is placed in a plasma spraying apparatus. A voltage is applied between the anode and cathode to generate a DC arc, and a gas such as argon is supplied to generate a plasma jet. A spray powder consisting of a mixture of alumina and titanium oxide is supplied into the plasma jet using argon gas or the like to form a sprayed film (first film 6) on the surface of the ceramic porous body 1. The mixing ratio of alumina and titanium oxide is adjusted so that the first film 6 has the desired color (brightness) and resistance value. Areas of the surface of the ceramic porous body 1 where the first film 6 is not to be formed should be covered with a mask.

Step (d) is a step of coating the first film 6 located on at least the second surface 2a and the side surface (third side surface 83) of the ceramic porous body 1 with a second film 7 that has lower resistance than the first film 6 and is not permeable. The second film 7 is as described above, and a detailed explanation is omitted. Hereinafter, the second film 7, which mainly contains titanium dioxide, can be produced in the same manner as the first film 6, using thermal spray powder mainly composed of titanium dioxide.

Step (e) is a step in which the first film 6 and the second film 7 are ground simultaneously to make them substantially flush. In steps (c) and (d), the first film 6 and the second film 7 are formed to be slightly thicker than the desired thickness, and in step (e), they are ground together by, for example, surface grinding and lapping to make them substantially flush.

Through these steps (a) to (e), a vacuum chuck 10 according to one embodiment, as shown in Figures 1 and 5, can be obtained.

Next, a method for manufacturing a vacuum chuck 20 according to another embodiment of the present disclosure includes the following steps (A) to (F).
(A) A step of preparing a ceramic porous body and a ceramic dense body having recesses for accommodating the ceramic porous body.
(B) A step of joining a porous ceramic body to a recess and processing it so that the porous ceramic body and the dense ceramic body are substantially flush, thereby forming a first surface on the upper surface of the porous ceramic body.
(C) A step of forming a third surface in a dense ceramic body that surrounds the recess, connects to the wall surface of the recess and is substantially flush with the first surface, and a second surface on the outer edge of the third surface so as to surround the third surface.
(D) A step of coating the surface from the first surface to the second surface with a first film that is breathable and semiconductive.
(E) A step of coating the side surfaces of the first film and the dense ceramic body, which are located on at least the second surface, with a second film that has lower resistance than the first film.
(F) A step of grinding the first film and the second film simultaneously to make the first film and the second film substantially flush.

Step (A) is a step of preparing a ceramic porous body 1 and a ceramic dense body 21 having recesses 211 for accommodating the ceramic porous body 1. The ceramic porous body 1 is a thinner version of the ceramic porous body described in step (a) above, and a detailed explanation is omitted. The ceramic dense body 21 is as described above, and a detailed explanation is omitted. Below, an example of a method for manufacturing the ceramic dense body 21, which mainly contains alumina, will be described.

First, aluminum oxide powder (purity of 99.9% by mass or higher), along with magnesium hydroxide, silicon oxide, and calcium carbonate powders, are placed in a grinding mill along with a solvent (deionized water) and a dispersant. After grinding until the average particle size (D ₅₀ ) of the powder is 1.5 μm or less, an organic binder, plasticizer, and release agent are added and mixed to obtain a slurry.

The magnesium hydroxide powder content in the total 100% by mass of the above powder is 0.2% to 0.5% by mass, the silicon dioxide powder content is 0.03% to 0.06% by mass, the calcium carbonate powder content is 0.015% to 0.025% by mass, and the remainder is aluminum oxide powder and unavoidable impurities.

Examples of organic binders include acrylic emulsion, polyvinyl alcohol, polyethylene glycol, and polyethylene oxide. The amount of organic binder added is 3 to 8 parts by mass per 100 parts by mass of the above powder.

Granules are obtained by granulating the above slurry using a spray dryer. Next, the obtained granules are filled into a mold and molded under hydrostatic pressure to obtain a molded body. The molding pressure is, for example, 78 MPa to 128 MPa. The obtained molded body is processed to obtain a precursor having recesses and the like. A sintered body is obtained by firing this precursor in an atmospheric atmosphere at a temperature of 1500°C to 1700°C and a holding time of 4 hours to 6 hours. A dense ceramic body 21 is obtained by grinding this sintered body.

The recess 211 may be formed when obtaining the molded body before firing. Alternatively, the recess 211 may be formed after firing by subjecting the sintered body to cutting or grinding processes.

Step (B) is a step in which the ceramic porous body 1 is joined to the recess 211 and processed so that the ceramic porous body 1 and the ceramic dense body 21 are substantially flush, thereby forming a first surface 1a on the upper surface of the ceramic porous body 1. The method of joining the ceramic porous body 1 and the ceramic dense body 21 (recess 211) is not limited and can be done using, for example, an adhesive.

After joining the porous ceramic body 1 to the recess 211, the porous ceramic body 1 and the dense ceramic body 21 are processed so that they are substantially flush. Specifically, grinding and polishing can be used to make the porous ceramic body 1 and the dense ceramic body 21 substantially flush.

Step (C), as shown in Figure 3, is the process of forming a third surface 2b in the dense ceramic body 21 that surrounds the recess 211, connects to the wall surface of the recess 211 and is substantially flush with the first surface 1a, and a second surface 2a on the outer edge of the third surface 2b so as to surround the third surface 2b. The second surface 2a is preferably formed in a lower part than the first surface 1a. The method for forming the second surface 2a is the same as in step (b) above, and a detailed explanation is omitted.

The third surface 2b located on the dense ceramic body 21 is processed in step (B) above so that the porous ceramic body 1 and the dense ceramic body 21 are substantially flush. Therefore, by forming the second surface 2a, the third surface 2b is also inevitably formed.

As shown in Figure 4, when forming the second surface 2a, the second side surface 82 located between the third surface 2b and the second surface 2a may be processed to incline outward as needed. The second surface 2a may also be processed to incline so that it becomes lower towards the outside. Furthermore, the corner C3 formed between the third surface 2b and the second side surface 82 located between the third surface 2b and the second surface 2a may be subjected to chamfering. The corner C2 formed between the second surface 2a and the third side surface 83, which is the outer surface of the support portion 2 (ceramic dense body 21), may also be subjected to chamfering.

Step (D) is a step of coating the surface from the first surface 1a to the second surface 2a with a first film 6 that is permeable and semiconductive. The first film 6 and the method for producing the first film 6 are as described above, and a detailed explanation is omitted.

Step (E) is a step of coating the first film 6 located on at least the second surface 2a and the side surface (third side surface 83) of the dense ceramic body 21 with a second film 7 which has lower resistance than the first film 6. The second film 7 and the method for producing the second film 7 are as described above, and a detailed explanation is omitted.

Step (F) is a process in which the first film 6 and the second film 7 are ground simultaneously to make them substantially flush. Step (F) is as described in step (e) above, and a detailed explanation is omitted here.

In this way, by steps (A) to (F), a vacuum chuck 20 according to another embodiment, as shown in Figure 3, can be obtained. The vacuum chuck 10 according to one embodiment and the vacuum chuck 20 according to the other embodiment obtained in this way can be used, for example, as a component of a processing device that fixes an object to be adsorbed, such as a semiconductor wafer, and processes the surface of the object to be adsorbed.

The embodiments of the present disclosure have been described above. However, the inventions relating to the present disclosure are not limited to the embodiments described above, and various modifications and improvements are possible within the scope of the present disclosure as shown in (1), (12), and (13) below.

(1) The vacuum chuck according to the present disclosure includes a plate-shaped ceramic porous body having a first surface which is the mounting surface side and pores communicating in the thickness direction, a support portion having an annular second surface located so as to surround the first surface, a first film having permeability and semiconductivity, and a second film having lower resistance than the first film. At least one of the support portion and the second film is not permeable. The first film covers from the first surface to the second surface. The second film covers at least the first film and the side surface of the support portion located on the second surface.

With regard to embodiments of the present disclosure, the embodiments shown in (2) to (11) below are further disclosed.

(2) In the vacuum chuck described in (1) above, the ceramic porous body and the support part are integrally molded.
(3) In the vacuum chuck described in (1) above, the support portion is a dense ceramic body having a recess for accommodating a porous ceramic body. It has a third surface that surrounds the recess, connects to the wall surface of the recess, and is substantially flush with the first surface, and a second surface that surrounds the third surface on the outer peripheral edge of the third surface.
(4) In the vacuum chuck described in (2) above, the integrally molded product is placed such that the surface opposite to the first surface is in contact with the base material.
(5) In the vacuum chuck described in any of (1) to (4) above, the second surface is located in a lower part than the first surface. The second film located on the second surface is flush with the first film located on the first surface, or is located in a lower part than the first film located on the first surface.
(6) In the vacuum chuck described in any of (1) to (5) above, the first film and the second film are ceramic thermal spray films.
(7) In the vacuum chuck described in any of (1) to (6) above, the first film has a different color from the second film.
(8) In the vacuum chuck described in any of (2) and (4) to (7) above, the ceramic porous body is mainly composed of alumina, and the first film comprises alumina and at least one of titanium oxide and zinc oxide.
(9) In the vacuum chuck described in any of (3) and (5) to (7) above, the ceramic porous body and the ceramic dense body are mainly composed of alumina, and the first film comprises alumina and at least one of titanium oxide and zinc oxide.
(10) In the vacuum chuck described in any of (1) to (9) above, the second film contains titanium oxide as the main component.
(11) In the vacuum chuck described in any of (1) to (10) above, the second film is denser and thicker than the first film.

(12) A method for manufacturing a vacuum chuck according to the present disclosure includes the steps of: preparing a ceramic porous body having an upper surface, a lower surface, and side surfaces, and having pores communicating in the thickness direction; forming a first surface and an annular second surface on the upper surface of the ceramic porous body, which are located on the peripheral edge of the upper surface so as to surround the first surface; coating the first surface and the second surface with a first film that is permeable and semiconductive; coating at least the first film and the side surfaces of the ceramic porous body located on the second surface with a second film that is less resistant than the first film and is not permeable; and grinding the first film and the second film simultaneously to make the first film and the second film substantially flush.

(13) A method for manufacturing another vacuum chuck according to the present disclosure includes the steps of: preparing a plate-shaped ceramic porous body having pores communicating in the thickness direction and a ceramic dense body having a recess for housing the ceramic porous body; joining the ceramic porous body to the recess and processing the ceramic porous body and the ceramic dense body so that they are substantially flush, thereby forming a first surface on the upper surface of the ceramic porous body; forming a third surface on the ceramic dense body that surrounds the recess, connects to the wall surface of the recess and is substantially flush with the first surface, and a second surface that surrounds the third surface and is located on the outer peripheral edge of the third surface; coating the ceramic dense body from the first surface to the second surface with a first film that is permeable and semiconductive; coating at least the side surfaces of the first film and the ceramic dense body located on the second surface with a second film that has lower resistance than the first film; and grinding the first film and the second film simultaneously so that they are substantially flush.

1. Ceramic porous body 1a. First surface 2. Support part 21. Ceramic dense body 211. Recess 2a. Second surface 2b. Third surface 3. One-piece molded product 4. Dense substrate 5. Suction hole 6. First film 7. Second film 81. First side 82. Second side 83. Third side 10, 20. Vacuum chuck

Claims (13)

A ceramic porous body having a plate-like first surface which is the mounting surface, and having pores that communicate in the thickness direction,
A support portion having an annular second surface positioned to surround the first surface,
A first membrane having breathability and semiconductivity,
A second film having lower resistance than the first film,
Includes,
At least one of the support portion and the second membrane is not breathable.
The first film covers from the first surface to the second surface,
The second film covers at least the first film and the side surface of the support portion located on the second surface.
Vacuum chuck. The vacuum chuck according to claim 1, wherein the ceramic porous body and the support portion are integrally molded. The support portion is a dense ceramic body having a recess for accommodating the porous ceramic body.
The outer peripheral edge of the recess has a third surface that surrounds the recess, connects to the wall surface of the recess, and is substantially flush with the first surface, and the outer peripheral edge of the third surface has a second surface that surrounds the third surface.
The vacuum chuck according to claim 1. The vacuum chuck according to claim 2, wherein the integrally molded product is placed such that the surface opposite to the first surface is in contact with the substrate. The second surface is located in a lower part than the first surface.
The second film located on the second surface is either flush with the first film located on the first surface, or located in a lower position than the first film located on the first surface.
A vacuum chuck according to any one of claims 1 to 4. The vacuum chuck according to any one of claims 1 to 4 , wherein the first film and the second film are ceramic thermal spray films. The vacuum chuck according to any one of claims 1 to 4 , wherein the first film has a different color from the second film. The vacuum chuck according to claim 2 or 4 , wherein the ceramic porous body is mainly composed of alumina, and the first film comprises alumina and at least one of titanium oxide and zinc oxide. The vacuum chuck according to claim 3 , wherein the ceramic porous body and the ceramic dense body are mainly composed of alumina, and the first film comprises alumina and at least one of titanium oxide and zinc oxide. The vacuum chuck according to any one of claims 1 to 4 , wherein the second film contains titanium oxide as the main component. The vacuum chuck according to any one of claims 1 to 4 , wherein the second film is denser and thicker than the first film. A step of preparing a ceramic porous body having an upper surface, a lower surface, and side surfaces, and having pores that communicate in the thickness direction,
A step of forming a first surface and an annular second surface located on the peripheral edge of the upper surface so as to surround the first surface on the upper surface of the ceramic porous body,
A step of coating the first surface with a first film that is breathable and semiconductive, from the first surface to the second surface,
A step of coating at least the side surfaces of the first film and the ceramic porous body located on the second surface with a second film that has lower resistance than the first film and does not allow air to pass through,
A step of grinding the first film and the second film simultaneously to make the first film and the second film substantially flush,
A method for manufacturing a vacuum chuck, including the method described above. A step of preparing a plate-shaped ceramic porous body having pores that communicate in the thickness direction, and a ceramic dense body having recesses for housing the ceramic porous body,
The steps include joining the porous ceramic body to the recess, processing the porous ceramic body and the dense ceramic body so that they are substantially flush, thereby forming a first surface on the upper surface of the porous ceramic body,
A step of forming a third surface on the dense ceramic body that surrounds the recess, connects to the wall surface of the recess, and is substantially flush with the first surface, and a second surface that surrounds the third surface and is located on the outer edge side of the third surface.
A step of coating the first surface with a first film that is breathable and semiconductive, from the first surface to the second surface,
A step of coating the side surfaces of the first film and the dense ceramic body, which are located at least on the second surface, with a second film having lower resistance than the first film,
A step of grinding the first film and the second film simultaneously to make the first film and the second film substantially flush,
A method for manufacturing a vacuum chuck, including the method described above.