JP7018839B2 - Ceramic structure and its manufacturing method - Google Patents

Description

The present disclosure relates to a ceramic structure and a method for manufacturing the same.

Alumina ceramics, which are relatively inexpensive and have excellent mechanical properties, have been developed into various structures. As one of the structures, a joining technique is used in the case where a cylindrical body is fitted into a hole of a plate-shaped body, and it is considered to increase the joining force from the viewpoint of improving reliability. ..

For example, in Patent Document 1, a ceramic disk in which a concave portion having a tapered surface whose peripheral surface is expanded outward is formed on one side, and a tapered surface that can be engaged with the tapered surface of the concave portion is the outer periphery of one end. There has been proposed a ceramic structure in which a ceramic cylinder similar to a ceramic disk is joined between both tapered surfaces via a joining layer containing an inorganic component as a main component.

Japanese Unexamined Patent Publication No. 2001-10872

When the outer diameter of the tubular body is as small as 1 mm or less, or when the wall thickness of the tubular body is as thin as 0.5 mm or less, the tubular body becomes a plate-like body due to a thermal cycle in which heating and cooling are repeated. There was a problem that it became easy to get out of.

The present disclosure provides a ceramic structure having excellent reliability against repeated heating and cooling in a structure made of bonded ceramics, and a method for manufacturing the same.

The ceramic structure of the present disclosure is made of an aluminous ceramic oxide containing silicon, and includes a base having holes and a shaft portion fitted into the holes. The base portion has a first region around the hole including a fitting surface with the shaft portion, and a second region excluding the first region, and the first region is larger than the second region. When the area ratio of silicon is small, the shaft portion contains silicon, and the portion including the fitting surface with the base portion is set as the third region, the third region is larger than the first region. The area ratio of silicon is large .

In the method for manufacturing a ceramic structure of the present disclosure, the base thereof is composed of a first substrate and a second substrate, and water droplets are sprayed on at least one of the fitting surface of the second substrate and the fitting surface of the shaft portion. And then heat-treat.

The ceramic structure of the present disclosure is excellent in reliability because the shaft portion does not easily come off from the base portion even after repeated heating and cooling.

An example of the ceramic structure of the present disclosure is shown, (a) is a perspective view, and (b) is a partial cross-sectional view showing a state of being cut along the axial center of the shaft portion. (A) is a photograph of the A part of the ceramic structure shown in FIG. 1 taken with a scanning electron microscope, (b) is an enlarged photograph of the C part in (a), and (c) is an electron beam. It is a color mapping image of silicon in the region (b) using a microanalyzer (EPMA). (A) is a perspective view, and (b) is a partial cross-sectional view including an axial center of a shaft portion, showing another example of the ceramic structure of the present disclosure. (A) is a perspective view, and (b) is a partial cross-sectional view showing a state of being cut along the axial center of the shaft portion, showing another example of the ceramic structure of the present disclosure.

Hereinafter, the ceramic structure of the present disclosure will be described in detail with reference to the drawings.

1, 3 and 4 show a plurality of examples of the ceramic structure of the present disclosure, (a) is a perspective view, and (b) is a partial cross-sectional view showing a state of being cut along an axial center of a shaft portion. Is.

2 (a) is a photograph of the A part of the ceramic structure shown in FIG. 1 taken with a scanning electron microscope, (b) is an enlarged photograph of the C part in (a), and (c) is a photograph. It is a color mapping image of silicon in the region (b) using an electron beam microanalyzer (EPMA).

In the color mapping image, the part where the presence of the element is recognized is displayed in white or colored, and the part where the presence of the element is not recognized is displayed in black. In this drawing, the portion other than black is the existing position of silicon. The ceramic structure 20 shown in FIG. 1 includes a base portion 1 having a hole 8 and a shaft portion 2 fitted into the hole 8. The base portion 1 and the shaft portion 2 are made of aluminum oxide ceramics. Further, the base 1 made of aluminum oxide ceramics contains silicon.

Here, the aluminum oxide ceramics refer to ceramics in which aluminum oxide accounts for 70% by mass or more in the total content of 100% by mass of the components constituting the ceramics. Further, the content of each component constituting the ceramics is identified from the measurement result by the X-ray diffractometer using CuKα ray, and then the ICP (Inductively Coupled Plasma) emission spectroscopic analyzer or the fluorescent X-ray analyzer (XRF) is used. It may be used to determine the content of the element and convert it to the content of the identified component.

Further, the base 1 may be, for example, a disk having an outer diameter of 3 mm or more and 12 mm or less and a thickness of 2 mm or more and 8 mm or less. The shaft portion 2 is, for example, a cylinder having an outer diameter of 0.5 mm or more and 1.5 mm or less, an inner diameter of 0.2 mm 0.4 mm or less, and a height of 10 mm or more and 50 mm or less from the end face of the shaft portion 2 inside the base portion 1. It may be a body. In the ceramic structure 10 shown in FIG. 1, an example is shown in which the end surface of the shaft portion 2 and the bottom surface of the hole 8 of the base portion 1 (the surface facing the end surface of the shaft portion 2) are separated from each other. The end surface of the portion 2 and the bottom surface of the hole 8 of the base portion 1 may be in contact with each other.

As shown in FIG. 2, the base portion 1 has a first region 3 around a hole 8 including a fitting surface with the shaft portion 2, and a second region 4 excluding the first region 3. The first region 3 is a region up to 60 μm inward from the fitting surface with the shaft portion 2 (fitting surface at the base portion 1). In the ceramic structure 20 of the present disclosure, in the base 1, the area ratio of silicon in the first region 3 is smaller than the area ratio of silicon in the second region 4. Although the silicon in the second region 4 is not shown in FIG. 2 (c), the area ratio of silicon is larger than that in the first region 3.

In the ceramic structure 20 having such a configuration, since the base 1 has a strong force to compress the portion of the shaft 2 including the fitting surface, the shaft 2 is difficult to come off from the base 1 even after repeated heating and cooling. ..

Further, the shaft portion 2 made of aluminum oxide ceramics may also contain silicon. When the portion of the shaft portion 2 including the fitting surface (fitting surface with the base portion 1) is set as the third region 5 (see FIG. 2B), the area ratio of silicon in the first region 3 is the second. In addition to being smaller than the area ratio of silicon in the region 4, the third region 5 may have a larger area ratio of silicon than the first region 3. The third region 5 is a region up to 60 μm inward from the fitting surface of the shaft portion 2.

When such a configuration is satisfied, in the temperature range from room temperature to 400 ° C., the first region 3 has a higher linear expansion coefficient than the second region 4, and the third region has a lower linear expansion coefficient than the first region 3. Therefore, compressive stress is generated in the first region 3 and tensile stress is generated in the third region 5, and the third region 5 can easily accept the compressive force from the first region 3, so that heating and cooling are repeated. However, the shaft portion 2 is more difficult to come off from the base portion 1.

In the example shown in FIG. 2 (c), the area ratio S ₁ of the silicon 6 in the first region 3 is 4.9%, and the area ratio S ₂ of the third region 5 is 6.5%. As described above, the difference ΔS between the area ratio S1 of the silicon 6 in the _first region ₃ and the area ratio S2 of the silicon 7 in the third region 5 may be 1% or more. When such a configuration is satisfied, the difference between the compressive stress and the tensile stress becomes higher than when the difference ΔS is less than 1%, so that the shaft portion 2 is more difficult to come off from the base portion 1.

_The area ratios S1 and S2 of silicon ₆ and 7 in each region can be obtained by the following method. First, a cross section cut along the axis of the shaft portion 2 is polished using diamond abrasive grains to obtain a polished surface. The image analysis software "A image-kun (ver2.52)" is used for the silicon color mapping image (for example, FIG. 2C) obtained by irradiating the polished surface with an electron beam of an electron probe microanalyzer (EPMA). ) ”(Registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd. In addition, when the image analysis software“ A image kun ”is described below, it means the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.). It can be obtained by a method called particle analysis. As the setting conditions of this method, for example, a threshold value indicating the brightness of the image may be 15, the brightness may be bright, the small figure removal area may be 0.1 μm ² , and a noise removal filter may be provided.

In the above measurement, the threshold value is set to 15, but the threshold value may be adjusted according to the brightness of the silicons 6 and 7. Specifically, the brightness is changed to bright and the binarization method is manual, the small figure removal area is 0.1 μm ² , and the noise removal filter is provided, and the size changes depending on the threshold value in the observation image. The threshold value may be adjusted so that the marker matches the shape of silicon 6 and 7. In the examples shown in FIGS. 2 (b) and 2 (c), the area of the first region 3 is 5540 μm ² , and the area of the third region 5 is 3100 μm ² .

Further, a part of the crystal particles 9 in the base portion 1 may be located over the shaft portion 2 on the fitting surface. When satisfying such a configuration, the crystal particles 9 play a role of preventing falling out, and the portion to which the compressing force is applied becomes closer to the shaft portion 2, so that the shaft portion 2 is more difficult to be pulled out from the base portion 1 and is made of ceramic. The reliability of the structure 20 is increased.

Further, the value obtained by subtracting the average value of the circle-equivalent diameter of the silicon 6 from the average value of the distance between the centers of gravity of the silicon 6 in the third region 5 is the average value of the distance between the centers of gravity of the silicon 7 in the first region 3 of the silicon 7. It may be smaller than the value obtained by subtracting the average value of the circle equivalent diameter.

The above is a comparison of the size and distribution state of silicon for each region. When such a configuration is satisfied, a strong compressive force is applied to the shaft portion 2 from the base portion 1, so that the shaft portion 2 is further divided into base portions. It becomes difficult to come off from 1, and the reliability of the ceramic structure 20 is further increased.

The corresponding circle diameter and the distance between the centers of gravity of silicon 6 and 7 can be obtained by the following methods. First, the image analysis software "A" targets the silicon color mapping image shown in FIG. 2 (c).
Using a technique called particle analysis using "Image-kun", the equivalent circle diameters of silicon 6 and 7 may be obtained. Similarly, the distance between the centers of gravity may be obtained by using the image analysis software "A image-kun" for the color mapping image of silicon shown in FIG. 2C and using a method called the distance between the centers of gravity. In either case, the setting conditions may be the same as the setting conditions for obtaining the area ratio S ₁ (S ₂ ).

Further, the coefficient of variation of the equivalent circle diameter of the silicon 6 in the third region 5 may be smaller than the coefficient of variation of the equivalent circle diameter of the silicon 7 in the first region 3. When such a configuration is satisfied, the compressive force applied from the base portion 1 to the shaft portion 2 has little variation, so that the reliability of the ceramic structure 20 is further increased. The coefficient of variation of the circle equivalent diameter is obtained by calculating the arithmetic mean and standard deviation of the circle equivalent diameter and dividing the standard deviation by the arithmetic mean.

FIG. 3 is a perspective view showing another example of the ceramic structure of the present disclosure.

In the ceramic structure 30 shown in FIG. 3, the base 1 has a first substrate 1a and a second substrate 1b. Specifically, the base 1 is composed of a first substrate 1a and a second substrate 1b mounted on the first substrate 1a and having holes 8. The shaft portion 2 is inserted into the hole 8 and is formed by joining the first substrate 1a and the second substrate 1b. In FIG. 3, the upper surface of the first substrate 1a and the lower surface of the second substrate 1b are joined. Then, the fitting surface of the shaft portion 2 and the second substrate 1b may be directly joined. The fitting surface between the shaft portion 2 and the second substrate 1b is the outer peripheral surface of the shaft portion 2 and the inner peripheral surface of the hole 8 of the second substrate 1b in the configuration shown in FIG. In addition, the direct bonding in the present disclosure means a bonding that does not go through a bonding layer, that is, does not use a bonding agent.

When satisfying such a configuration, in addition to excellent reliability, the position accuracy (squareness) of the shaft portion 2 with respect to the first substrate 1a can be increased.

Although the hole 8 shows an example of penetrating the second substrate 1b in the thickness direction in FIG. 3, it may not penetrate. Further, in FIG. 3, the shaft portion 2 is not in contact with the upper surface of the first substrate 1a in the drawing, but may be in contact with the upper surface. Further, in FIGS. 1 and 3, although the shaft portion 2 is shown as a cylindrical body, it may be a columnar shape.

Further, in the ceramic structure of the present disclosure, the relative density of the shaft portion 2 may be higher than the relative density of the second substrate 1b. When the relative density of the shaft portion 2 is higher than the relative density of the second substrate 1b, the thermal conductivity of the shaft portion 2 is high, so that the heat generated in the second substrate 1b or the heat given from the outside is used as the shaft portion. You can escape to 2. That is, the second substrate 1b can be cooled quickly.

The relative density is expressed as a percentage (ratio) of the apparent density of the ceramics determined according to JIS R 1634-1998 with respect to the theoretical density of the identified main component ceramics.

Further, in addition to the relationship of relative density, the average crystal grain size of aluminum oxide in the shaft portion 2 may be smaller than the average crystal grain size of aluminum oxide in the second substrate 1b. When satisfying such a configuration, the shaft portion 2 has high fracture toughness and mechanical strength, so that it can withstand long-term use and has excellent reliability.

Regarding the measurement of the average crystal grain size of aluminum oxide, first, the surface to be measured is heat-treated at a temperature 50 to 100 ° C. lower than the firing temperature. Then, the heat-treated surface is photographed using an optical microscope with a magnification of 400 times and a measurement target range of, for example, a horizontal length of 200 μm and a vertical length of 140 μm. Next, by using image analysis software (for example, Win ROOF manufactured by Mitani Shoji Co., Ltd.) with the central part (area of 1.05 x ¹⁰⁵ μm) as the measurement range of the captured images. , The value of the average crystal grain size of aluminum oxide can be obtained. In the analysis, the threshold value of the particle size is 0.21 μm, and the particle size less than 0.21 μm is not included in the calculation of the average crystal particle size. It can be said that this threshold value is for simply selecting aluminum oxide crystal particles.

Further, the second substrate 1b and the shaft portion 2 contain silicon and at least one of magnesium and calcium, and the total content of silicon, magnesium and calcium converted into oxides is higher than that of the second substrate 1b in the shaft portion 2. May be less.

When such a configuration is satisfied, the thermal conductivity of the shaft portion 2 is high, and the residual stress generated in the shaft portion 2 can be reduced from that of the second substrate 1b even if heating and cooling are repeated, so that the residual stress generated in the shaft portion 2 can be reduced over a long period of time. Can be used. Further, when only the shaft portion 2 is used in an environment exposed to plasma, its deterioration can be suppressed.

For the content of each of silicon, magnesium and calcium, the content of each of these elements is determined by ICP or XRF, and the content of each of these elements is converted into oxides (SiO ₂ , MgO, CaO), respectively. Can be calculated.

Further, the shaft portion 2 may be a tubular body and may have a covering layer 9 extending from the inner peripheral surface of the tubular body to the facing surface of the first substrate 1a with respect to the shaft portion 2. The ceramic structure 40 of FIG. 4 shows this configuration. Here, the surface of the first substrate 1a facing the shaft portion 2 corresponds to the upper surface of the first substrate 1a in FIG. When satisfying such a configuration, the shaft portion 2 is more difficult to come off, and therefore has further excellent reliability.

Next, an example of the method for manufacturing the ceramic structure of the present disclosure will be described.

First, an example of a method for manufacturing a base (first substrate and second substrate) will be described.

Aluminum oxide powder (purity of 99.9% by mass or more), which is the main component, and magnesium hydroxide, silicon oxide, and calcium carbonate powders are put into a pulverizing mill together with a solvent (ion-exchanged water) to prepare the powder. After pulverizing until the average particle size (D ₅₀ ) becomes 1.5 μm or less, an organic binder and a dispersant for dispersing aluminum oxide powder are added and mixed to obtain a slurry.

Here, the content of the magnesium hydroxide powder in the total 100% by mass of the powder is 0.3 to 0.42% by mass, the content of the silicon oxide powder is 0.5 to 0.8% by mass, and the content of the calcium carbonate powder is The content is 0.060 to 0.1% by mass, and the balance is aluminum oxide powder and unavoidable impurities.

Examples of the organic binder are acrylic emulsions, polyvinyl alcohols, polyethylene glycols, polyethylene oxides and the like.

Next, after the slurry is spray-granulated to obtain granules, a substrate-like molded body is formed by pressurizing the molding pressure to 78 MPa or more and 128 MPa or less using a uniaxial press molding device or a cold hydrostatic press molding device. To get.

A part of the molded body forms a hole by cutting.

Next, the first substrate and the second substrate are obtained by firing the molded body without holes and the molded body having holes, respectively, with the firing temperature set to 1500 ° C. or higher and 1700 ° C. or lower and the holding time set to 4 hours or longer and 6 hours or lower. ..

Next, an example of a method for manufacturing the shaft portion will be described.

An organic binder, a plasticizer, a lubricant and ion-exchanged water are added to each of the main components, aluminum oxide powder (purity of 99.9% by mass or more) and magnesium hydroxide, silicon oxide and calcium carbonate powders. After stirring using a universal stirrer, a rotary mill, a V-type stirrer, or the like, further kneading is performed using a three-roll mill, a kneader, or the like to obtain plasticized clay.

Here, the content of the magnesium hydroxide powder in the total 100% by mass of the powder is 0.43 to 0.53% by mass, the content of the silicon oxide powder is 0.02 to 0.04% by mass, and the content of the calcium carbonate powder is The content is 0.020 to 0.071% by mass, and the balance is aluminum oxide powder and unavoidable impurities.

The organic binder is a water-soluble binder such as methyl cellulose and hydroxypropyl methyl cellulose.

Here, in order to make the average crystal grain size of the aluminum oxide crystal particles in the shaft portion smaller than the average crystal grain size of the aluminum oxide crystal particles in the second substrate, for example, the aluminum oxide powder used to obtain the shaft portion. The average particle size of the aluminum oxide powder used to obtain the second substrate should be smaller than the average particle size of the aluminum oxide powder, and the firing temperature for obtaining the shaft portion should be lower than the firing temperature for obtaining the second substrate. Just do it.

In addition, in order to reduce the total content of silicon, magnesium and calcium converted to oxides in the shaft portion compared to the second substrate, the contents of magnesium hydroxide powder, silicon oxide powder and calcium carbonate powder should be reduced. The total may be smaller in the shaft portion than in the second substrate.

Further, the value obtained by subtracting the average value of the equivalent diameter of the circle of silicon from the average value of the distance between the centers of gravity of silicon in the third region is the average value of the equivalent diameter of the circle of silicon from the average value of the distance between the centers of gravity of silicon in the first region. In order to make it smaller than the value obtained by subtracting, the content of the silicon oxide powder used to obtain the shaft portion may be smaller than the content of the silicon oxide powder used to obtain the base portion.

Further, in order to make the coefficient of variation of the equivalent circle diameter of silicon in the third region smaller than the coefficient of variation of the equivalent circle diameter of silicon in the first region, the average particle size of the silicon oxide powder used to obtain the shaft portion should be adjusted. , The dispersibility may be improved by making the particle size smaller than the average particle size of the silicon oxide powder used to obtain the base.

Next, the clay is molded by an extrusion molding machine to obtain a tubular or columnar molded body.

Here, in order to make the relative density of the shaft portion higher than the relative density of the second substrate, the extrusion speed of the clay during the formation of the molded body to be the shaft portion should be made as slow as possible, for example, 20 m / min or less. good.

Then, a tubular or columnar sintered body can be obtained by firing the molded product at a firing temperature of 1500 ° C. or higher and 1700 ° C. or lower and a holding time of 4 hours or longer and 6 hours or lower.

Then, the ceramic structure of the present disclosure can be obtained by spraying and adsorbing water droplets on at least one of the fitting surface of the second substrate and the fitting surface of the shaft portion and then heat-treating. Here, water droplets may be sprayed and adsorbed on at least one of the upper surface of the first substrate and the lower surface of the second substrate.

Elements other than Al induced by the hydration reaction (local OH group hydrolysis reaction by _H2O with few impurities), in which the surfaces on which the sprayed water droplets face each other can be brought into close contact with each other by surface tension ( Si, Mg, Ca) are recrystallized from aluminum oxide due to the difference in electronegativity, and a strong bond can be obtained.

Here, at least one of the fitting surface of the second substrate and the fitting surface of the shaft portion may be polished, and the average particle size D ₅₀ is polished using, for example, diamond abrasive grains of 2 μm or less. May be good. Polishing activates the reaction of hydrolysis of the polished surface, so that a stronger bond can be obtained. The arithmetic mean roughness Ra of the polished surface may be 0.4 μm or less.

Next, water droplets are sprayed, adsorbed and fitted, and then heat-treated at a temperature of 1000 ° C. or higher and 1800 ° C. or lower. Silicon diffuses and moves toward. As a result, in the base portion, the area ratio of silicon in the first region is smaller than that in the second region. Further, by setting the heat treatment temperature to 1100 ° C. or higher and 1800 ° C. or lower, the area ratio of silicon in the third region can be increased as compared with the first region. Further, in order to make the difference between the area ratio of silicon in the first region and the area ratio of silicon in the third region 1% or more, the temperature may be 1200 ° C. or higher and 1800 ° C. or lower.

The ceramic structure obtained by the above-mentioned manufacturing method is excellent in reliability because the shaft portion does not easily come off from the base portion even after repeated heating and cooling. Therefore, it can be suitably used for applications that require excellent reliability, for example, a member for a semiconductor manufacturing device and a member for a liquid crystal manufacturing device.

1: Base 1a: 1st substrate 1b: 2nd substrate 2: Shaft 3: 1st region 4: 2nd region 5: 3rd region 6: Silicon 7: Silicon 8: Hole 9: Crystal particles 10: Coating portion 20 , 30, 40: Ceramic structure

Claims (10)

The base with holes and
A shaft portion fitted into the hole is provided, and the shaft portion is provided.
The base and the shaft are made of aluminum oxide ceramics.
At least the base contains silicon and
The base portion has a first region around the hole including a fitting surface with the shaft portion, and a second region excluding the first region.
The area ratio of silicon in the first region is smaller than that in the second region.
When the shaft portion contains silicon and the portion including the fitting surface with the base portion is set as the third region,
The third region is a ceramic structure having a larger area ratio of silicon than the first region . The ceramic structure according to claim 1 , wherein the difference between the area ratio of silicon in the first region and the area ratio of silicon in the third region is 1% or more. The ceramic structure according to claim 1 or 2 , wherein a part of the crystal particles in the base portion is located over the shaft portion on the fitting surface. The value obtained by subtracting the average value of the circle-equivalent diameter of the silicon from the average value of the center-of-gravity distance of the silicon in the third region is the value of the circle-equivalent diameter of the silicon from the average value of the center-of-gravity distance of the silicon in the first region. The ceramic structure according to any one of claims 1 to 3 , which is smaller than the value obtained by subtracting the average value. The ceramic structure according to any one of claims 1 to 4 , wherein the coefficient of variation of the equivalent circle diameter of silicon in the third region is smaller than the coefficient of variation of the equivalent circle diameter of silicon in the first region. The base portion is composed of a first substrate and a second substrate mounted on the first substrate and having the holes, and the shaft portion is joined to the first substrate and the second substrate. The ceramic structure according to any one of claims 1 to 5 , wherein the fitting surface of the shaft portion and the fitting surface of the second substrate are directly joined to each other. The ceramic structure according to claim 6 , wherein the relative density of the shaft portion is higher than the relative density of the second substrate. The ceramic structure according to claim 6 or 7 , wherein the shaft portion is a tubular body and has a coating layer extending from an inner peripheral surface of the tubular body to a surface facing the shaft portion in the first substrate. body. The method for manufacturing a ceramic structure according to any one of claims 6 to 8 , wherein in the fitting step, water droplets are formed on at least one of the fitting surface of the second substrate and the fitting surface of the shaft portion. A method for manufacturing a ceramic structure, in which a ceramic structure is sprayed and adsorbed, then fitted, and then a heat treatment step is performed. The method for manufacturing a ceramic structure according to claim 9 , wherein a polishing step of polishing at least one of the fitting surface of the second substrate and the fitting surface of the shaft portion is performed before the fitting step.

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