JP6361717B2 - Dielectric material - Google Patents

Description

  The present invention relates to a dielectric material, and more particularly, a dielectric suitable for use as a material for constituent members of a vacuum process apparatus such as an etching apparatus, a sputtering apparatus, or a CVD apparatus applied to a manufacturing process of a semiconductor or a liquid crystal display. It relates to materials.

Conventionally, components made of ceramics such as alumina have been widely used in various processes such as etching and sputtering in a production line of semiconductor devices such as IC, LSI, and VLSI. For example, an electrostatic chuck is mentioned as a ceramic component in a semiconductor manufacturing apparatus.
An electrostatic chuck requires high adhesion performance, excellent thermal conductivity, and durability as a support mechanism for a semiconductor substrate such as a silicon wafer. The electrostatic chuck includes a substantially disk-shaped insulator on which a semiconductor substrate is placed, and an electrostatic chucking internal electrode embedded in the insulator. By applying a DC voltage to the semiconductor substrate placed on the insulator, an electrostatic adsorption force due to Coulomb force or minute leakage current is generated, and the semiconductor substrate is placed on the insulator by this electrostatic adsorption force. It is fixed.

As an insulator used for the electrostatic chuck, ceramics such as aluminum oxide and aluminum nitride are generally used.
Ceramics are particularly excellent in thermal conductivity and plasma resistance, but they are hard to conform to the substrate due to the hard material, and as a result, scratches, cracks, etc. occur when transporting the semiconductor substrate, or long There is a risk of insulation deterioration due to use over a period of time and breakdown due to damage by plasma or corrosive gas, and elements on the semiconductor substrate may be destroyed during various processes such as etching and sputtering. There is.

Therefore, as a technology to detect dielectric breakdown of the insulator of the electrostatic chuck, the dielectric breakdown of the insulator was detected by installing a current detector in the circuit of the power supply connected to the electrostatic chuck, and the dielectric breakdown occurred. Techniques for preventing the electrostatic chuck from being used continuously have been proposed (see Patent Documents 1 and 2).
In addition, a technique for detecting a dielectric breakdown of an insulator by measuring a potential difference between an electrostatic chuck internal electrode for electrostatic chuck and a ground electrode has been proposed (see Patent Document 3, etc.).
Further, an electrostatic chuck using a porous dielectric instead of an insulator has been proposed (see Patent Document 4). This electrostatic chuck employs a diagnostic method for preventing dielectric breakdown due to moisture adsorption.

JP 2005-175122 A JP 2002-305237 A Japanese Patent Laid-Open No. 06-267905 JP 2008-47564 A

  However, in the conventional Coulomb force type electrostatic chuck, since a high voltage of 1000 V or more is applied to the insulator, the dielectric breakdown occurs when the dielectric breakdown occurs during the application of the high voltage. Occurs instantaneously and at the same time a large current flows, so that the electrostatic chuck becomes unusable when dielectric breakdown is detected. Therefore, the methods described in Patent Documents 1 to 3 have a problem that it is impossible to predict in advance that the electrostatic chuck cannot be used due to dielectric breakdown.

  In addition, when the electrostatic chuck breaks down, when the large current generated by the breakdown is detected, the large current flows in a concentrated manner at one point where the breakdown occurs. The above device will be damaged. Therefore, it is difficult to prevent dielectric breakdown from occurring in the electrostatic chuck during use, and it is difficult to prevent damage to the device due to dielectric breakdown.

  On the other hand, in the electrostatic chuck using a porous dielectric instead of the insulator described in Patent Document 4, it is only possible to detect the deterioration of insulation due to moisture adsorption of the porous dielectric, It is not possible to detect the essential insulation deterioration of the dielectric itself. Therefore, it is impossible to predict in advance that the electrostatic chuck cannot be used due to dielectric breakdown, and it is impossible to prevent dielectric breakdown from occurring in the electrostatic chuck during use. It is also difficult to prevent damage to the device.

  The present invention has been made in view of the above circumstances, and can provide a dielectric material that can detect a dielectric breakdown sign before or during use, and thus can predict dielectric breakdown in advance. The purpose is to provide.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a dielectric material comprising a composite sintered body in which conductive particles are dispersed in an insulating material, the insulating material is Al ₂ O _3. Y ₂ O ₃ or Si ₃ N ₄ , the conductive particles are SiC particles, and the composite sintered body is an Al ₂ O ₃ —SiC composite sintered body, Y ₂ O ₃ —SiC composite sintered body. A sintered body or a Si ₃ N ₄ —SiC composite sintered body, wherein the content of the conductive particles is 4% by mass or more and 20% by mass or less, and the conductive particles have a cumulative volume in the volume particle size distribution. The particle diameter D10 having a percentage of 10% by volume is 0.2 μm or less, the particle diameter D90 having a cumulative volume percentage of 90% by volume is 2 μm or less, and the cumulative volume percentage of the particle diameter D90 having a cumulative volume percentage of 90% by volume is 10 volumes. % Of particle size D10 The ratio (D90 / D10) is 3.0 or more, and the ratio (D90 / D50) of the particle size D90 having a cumulative volume percentage of 90% by volume to the particle size D50 having a cumulative volume percentage of 50% by volume is 1.4 or more. , and the if the dielectric material breakdown characteristics were evaluated after following withstand voltage test is as also satisfying the following condition, it is possible to proceed gently breakdown of the dielectric material, thus, used It has been found that dielectric breakdown can be predicted in advance by measuring the electric resistance of the dielectric material before or during use, and the present invention has been completed.
(anti-voltage test)
A dielectric material having a thickness of 1.0 mm is sandwiched between first electrodes, a predetermined measurement voltage is applied between the first electrodes and held for 1 minute, and then a current value flowing between the first electrodes is 1 nA. The measured voltage when the current value is higher than / cm ² is defined as the withstand voltage value.
(Dielectric breakdown characteristics)
A second electrode smaller than the first electrode is disposed at a position on the surface of the dielectric material where the first electrode is disposed in the withstand voltage test to sandwich the dielectric material, and A current value that flows when the same voltage as the withstand voltage value is applied between the second electrodes is measured.
(conditions)
When nine positions of the second electrode are selected at the position and the current values at nine points are measured, the ratio between the maximum value (Amax) and the minimum value (Amin) among the nine current values ( Amax / Amin) is 1000 times or less.

That is, the dielectric material of the present invention satisfies the following.
The dielectric material was processed to a constant thickness, a voltage was applied and a current of 100 nA / cm ² was applied for 1 second or less, and then an electrode having a predetermined area was placed on nine points on the surface and a voltage was applied. In this case, the ratio (Amax / Amin) between the maximum value (Amax) and the minimum value (Amin) among the current values of the currents flowing from the nine electrodes in the thickness direction of the dielectric material is 1000 times or less.
Further, the dielectric material is preferably the time required for the current value due to insulation breakdown increases from 1 nA / cm ² to 100 nA / cm ² is not less than 3 seconds.
The dielectric material of one embodiment is a dielectric material composed of a composite sintered body in which conductive particles are dispersed in an insulating material, and the conductive particles have a cumulative volume percentage in the volume particle size distribution. The 10% by volume particle diameter D10 is 0.2 μm or less, the cumulative volume percentage is 90% by volume, the particle diameter D90 is 2 μm or less, the cumulative volume percentage is 90% by volume, and the cumulative volume percentage of the particle diameter D90 is 10% by volume. The ratio (D90 / D10) to the particle diameter D10 is 3.0 or more, and the ratio (D90 / D50) of the particle diameter D90 having a cumulative volume percentage of 90 volume% to the particle diameter D50 having a cumulative volume percentage of 50 volume% is 1 .4 Ru der more.

The content of the conductive particles is preferably 4% by mass or more and 20% by mass or less.
The conductive particles are preferably one or more selected from the group consisting of conductive silicon carbide particles, molybdenum particles, tungsten particles, tantalum particles, and carbon particles.
The insulating material is preferably one or more selected from the group consisting of aluminum oxide, yttrium oxide, silicon oxide, zirconium oxide, aluminum nitride, silicon nitride, and mullite.

The relative dielectric constant is preferably 11 or more.
The withstand voltage is preferably 5 kV / mm or more.

According to the dielectric material of the present invention, the location of the dielectric breakdown is not formed in a pinhole shape, and the current value increases simultaneously due to the dielectric breakdown inside. For this reason, the dielectric breakdown of the dielectric material can be allowed to proceed gently. Therefore, by measuring the electrical resistance before or during use of the dielectric material made of the composite sintered body, a sign of dielectric breakdown can be known from the value of the electrical resistance. As a result, dielectric breakdown of the dielectric material made of this composite sintered body can be predicted in advance.

The form for implementing the dielectric material of this invention is demonstrated.
The following embodiments are specifically described for better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified.

[Dielectric material]
The dielectric material of the present embodiment is a dielectric material composed of a composite sintered body in which conductive particles are dispersed in an insulating material. The conductive particles have a cumulative volume percentage of 10 volume% in the volume particle size distribution. The particle diameter D10 is 0.2 μm or less, the cumulative volume percentage is 90 volume%, the particle diameter D90 is 2 μm or less, the cumulative volume percentage is 90 volume%, and the ratio of the cumulative volume percentage to 10 volume% is 10% by volume. A dielectric material having a ratio (D90 / D50) of 1.4 or more (D90 / D10) of 3.0 or more, a cumulative volume percentage of 90 volume% to a particle diameter D50 of 50 volume% of the cumulative volume percentage of D90 It is.

Here, the background to the knowledge of the dielectric material of the present embodiment will be described.
The formation of a conductive path of a dielectric material made of a composite sintered body in which conductive particles are dispersed in an insulating material can be explained by percolation theory.
In this percolation theory, when the ratio of the conductive particles dispersed in the insulating material exceeds a certain threshold, the conductivity increases rapidly (resistance value decreases), and the connection of the conductive particles near this threshold is fractal. It is known to show.

Therefore, the present inventors have made it easy to moderate the dielectric breakdown of the dielectric material made of the composite sintered body, that is, to improve the dielectric breakdown characteristics of the dielectric material, the conductive path at the time of the dielectric breakdown. We thought that it was necessary to increase the branch of the current path, that is, to increase the fractal dimension of the conductive path.
Based on this idea, a dielectric material that moderates dielectric breakdown was produced by dispersing a certain amount of conductive particles satisfying a certain particle size distribution in the insulating material. It was found that when the fractal dimension of the conductive path is increased, the dielectric breakdown does not occur in the form of pinholes but occurs with a wide distribution, so that the characteristic of gradual dielectric breakdown can be obtained.

In addition, by widening the particle size distribution of the conductive particles in the insulating material, when the conductive particles greater than the threshold are added, the fractal dimension of the connection of the conductive particles is increased, while It was found that when conductive particles were added, the fractal dimension of the conductive path caused by dielectric breakdown increased.
In addition, if the particle size distribution of the conductive particles in the insulating material is widened, the content of the conductive particles can be increased, and the threshold value for forming a conductive path is increased, so that the insulating property is maintained. It turned out that the content rate of electroconductive particle can be made high and a dielectric material with a high dielectric constant is obtained.
As described above, if a Coulomb force type electrostatic chuck base material is produced using a dielectric material having a high dielectric constant, the dielectric breakdown of the electrostatic chuck can be predicted by measuring the electric resistance or the current value. It is understood that the present invention has been created.

Next, the dielectric material of this embodiment will be described in detail.
As the insulating material used for this dielectric material, various organic resins such as polyimide resin and silicon resin and insulating ceramics can be selected as appropriate. Insulating ceramics is preferably used because it may be difficult to obtain characteristics that cause gradual destruction.

As this insulating material, that is, insulating ceramics, aluminum oxide (Al ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), silicon oxide (SiO ₂ ), zirconium oxide (ZrO ₂ ), aluminum nitride (AlN), Silicon nitride (Si ₃ N ₄ ), mullite (3Al ₂ O ₃ .2SiO ₂ ), hafnium oxide (HfO ₂ ), scandium oxide (Sc ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), niobium oxide (Nb ₂₎ O ₅ ), samarium oxide (Sm ₂ O ₃ ), ytterbium oxide (Yb ₂ O ₃ ), erbium oxide (Er ₂ O ₃ ), oxide consisting of only one selected from the group of cerium oxide (CeO ₂ ) Or a composite oxide formed by mixing two or more kinds.

Among these, aluminum oxide (Al ₂ O ₃ ) is particularly suitable for the dielectric material of this embodiment because it is inexpensive, excellent in heat resistance, and has good mechanical properties of the composite sintered body. .
Further, when it is desired to further enhance the case and corrosion resistance to be used aluminum (Al) content is less insulating ceramics, yttrium oxide _{(Y 2 O} 3), yttrium aluminum garnet _{(YAG: 3Y 2 O 3 ·} 5Al ₂ O ₃ ) or the like can also be used.

As the raw material powder of aluminum oxide (Al ₂ O ₃ ), it is preferable to use an aluminum oxide powder having an average particle diameter of 1 μm or less.
The reason is that in the silicon carbide-aluminum oxide composite sintered body obtained by using the aluminum oxide powder having an average particle diameter exceeding 1 μm, the average particle diameter of the aluminum oxide particles in the composite sintered body exceeds 2 μm. Thus, when a substrate of an electrostatic chuck device is produced using this silicon carbide-aluminum oxide composite sintered body, the upper surface of the substrate on which the plate-like sample is placed is easily etched by plasma. This is because sputter marks are formed on the upper surface of the base material, which may cause contamination of the object to be adsorbed such as a silicon wafer.
The raw material powder of aluminum oxide (Al ₂ O ₃ ) is not particularly limited as long as it has an average particle diameter of 1 μm or less and high purity.

The conductive particles include conductive ceramic particles such as conductive silicon carbide (SiC) particles, refractory metal particles such as molybdenum (Mo) particles, tungsten (W) particles, and tantalum (Ta) particles, and carbon (C) particles. It is preferable that it is 1 type, or 2 or more types selected from the group of these.
Among these, when conductive silicon carbide (SiC) particles are compounded with aluminum oxide (Al ₂ O ₃ ) particles, the obtained composite sintered body has a small temperature dependency of electrical characteristics, It is preferable since it has excellent corrosion resistance against gas, is excellent in heat resistance and thermal shock resistance, and has a low risk of damage due to thermal stress even when used at high temperatures.

As the conductive silicon carbide (SiC) particles, silicon carbide powder having a β-type crystal structure is preferably used because of its excellent conductivity. In addition, in order to control the conductivity of the silicon carbide powder, a material in which the nitrogen content in silicon carbide is appropriately controlled may be used.
As the conductive silicon carbide (SiC) particles, silicon carbide powder obtained by various methods such as a plasma CVD method, a precursor method, a thermal carbon reduction method, and a laser pyrolysis method can be used. In particular, when the dielectric material of this embodiment is used in a semiconductor process, it is preferable to use a high-purity material in order to prevent adverse effects in the semiconductor process.

In the dielectric material, the conductive particle has a particle size D10 having a cumulative volume percentage of 10% by volume in a volume particle size distribution of 0.2 μm or less, and a particle size D90 having a cumulative volume percentage of 90% by volume of 2 μm or less. The ratio (D90 / D10) of the particle size D90 having a cumulative volume percentage of 90% by volume to the particle size D10 having a cumulative volume percentage of 10% by volume is preferably 3.0 or more.
Further, the ratio (D90 / D50) of the particle size D90 having a cumulative volume percentage of 90% by volume to the particle size D50 having a cumulative volume percentage of 50% by volume is preferably 1.4 or more, and more preferably 1.5 or more. Is more preferable.

Here, the reason why various numerical values in the volume particle size distribution of the conductive particles are defined as described above will be described.
If there are too many large conductive particles in the dielectric material, there is a possibility that the plasma resistance and the number of particles when used as a base material for an electrostatic chuck may be deteriorated. Accordingly, the particle diameter D90 having a cumulative volume percentage of 90% by volume is preferably 2 μm or less (2% or more conductive particles are 10% or less), preferably 1 μm or less (1 μm or more conductive particles is 10% or less). More preferably.

  Also, if there are too many conductive particles with a fine particle size, when the amount of conductive particles is increased, the number of conductive particles becomes too large, leading to conductive particles existing at the grain boundaries of the insulating particles. Since it becomes easy to increase the withstand voltage and increase the blending amount of the conductive particles, that is, the dielectric constant cannot be increased, the particle diameter D90 having a cumulative volume percentage of 90% by volume is 0.5 μm or more. It is preferable. For the same reason, the particle diameter D50 having a cumulative volume percentage of 50% by volume is preferably 0.3 μm or more.

On the other hand, the thickness of the thinnest conductive path formed by dielectric breakdown depends on the size and ratio of conductive particles dispersed in the dielectric material. Therefore, in order to make it easy to obtain a characteristic that causes a gradual breakdown, it is necessary to reduce the thickness of the thinnest conductive path. Therefore, particles whose cumulative volume percentage in the volume particle size distribution of the conductive particles is 10% by volume. The diameter D10 is preferably 0.2 μm or less.
Furthermore, in order to make the branch of the dielectric breakdown finer and increase the branch of the conductive path, it is preferable that particles of 0.04 μm or less are contained in an amount of 0.001% or more, more preferably 1% or more and 10% or less.

Further, in order to moderate the dielectric breakdown, in addition to the condition that the particle diameter D10 having a cumulative volume percentage of 10 volume% is 0.2 μm or less, the cumulative volume percentage of the particle diameter D90 having a cumulative volume percentage of 90 volume% is The ratio (D90 / D10) of 10 volume% to the particle diameter D10 is 3.0 or more, and the ratio of the cumulative volume percentage of the particle diameter D90 of 90 volume% to the 50 volume% of the particle diameter D50 (D90 / D50) is preferably 1.4 or more, and more preferably 1.5 or more.
In order to obtain the effect of widening the particle size distribution efficiently, it is preferable that the particle size distribution is a smooth curve when graphed.

Note that the particle diameter in the raw material powder of the conductive particles and the particle diameter in the dielectric material are changed by pulverization and sintering in the manufacturing process, and thus do not have the same particle diameter. Therefore, it is necessary to determine the particle size of the raw material powder of the conductive particles so that the particle size of the conductive particles in the dielectric material is in the above range.
By the way, since it is difficult to obtain particles having a size of 0.04 μm or less by pulverization in the manufacturing process, the conductive particles contained in the dielectric material should contain 0.001% or more of particles having a size of 0.04 μm or less. It is preferable to use a material having a particle size of 0.04 μm or less in an amount of 1% or more (particle diameter D1 having a cumulative volume percentage of 1% by volume is 0.04 μm or less).

Further, in order to make the amount of the conductive particles contained in the composite sintered body 2 μm or more 10% or less (particle diameter D90 is 2 μm or less), the particle diameter of 1 μm or more in the raw material of the conductive particles The particles are preferably 1% or less (particle diameter D1 is 1 μm or less).
Furthermore, when several types of conductive particles are used in combination, the total of the various types of conductive particles preferably satisfies the above conditions.

The content of the conductive particles in the dielectric material is preferably 4% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 12% by mass. More preferably, it is at most mass%.
Here, the reason why the content of the conductive particles is in the above range is that when the content of the conductive particles is less than 4% by mass, the amount of the conductive particles is too small with respect to the insulating material. This is because conductivity cannot be obtained, and because the distance between the conductive particles contained in the dielectric material is too far away, it is difficult to obtain the characteristic that dielectric breakdown proceeds. On the other hand, when the content of the conductive particles exceeds 20% by mass, the amount of the conductive particles is too much with respect to the insulating material, and the conductive particles become large due to aggregation or sintering, and there are many particles of 2 μm or more. This is because it is easy to be obtained, and good dielectric characteristics can be obtained, but it is difficult to obtain a withstand voltage characteristic necessary for use as an electrostatic chuck.

In addition, since the content rate of the electroconductive particle in this dielectric material changes with the kind of insulating material to be used, and a required characteristic, it is preferable to optimize the content rate of electroconductive particle within the said range.
For example, when insulating ceramics are used as the insulating material, most of the conductive particles are unevenly distributed at the grain boundaries of the insulating ceramic crystal particles in the sintering stage, compared with the case where they are dispersed in the insulating resin. The threshold value for forming the conductive path is reduced.
This is because the larger the size of the insulating ceramic crystal particles with respect to the conductive particles, and the smaller the conductive particles taken into the insulating ceramic crystal particles, the more prominent.

Therefore, widening the particle size distribution of the conductive particles has the effect of increasing the threshold value for forming a conductive path even if the crystal size of the insulating ceramic crystal particles is the same. For example, when the particle diameter of the insulating ceramic crystal particles is 0.1 to 10 μm, the threshold value for forming the conductive path is about 4 to 20%.
Therefore, the content of conductive particles is preferably about 0.05 to 8% by volume smaller than the above threshold value, for example, so that the withstand voltage satisfies the specifications of the electrostatic chuck. It is more preferable to make the value about 5% by volume smaller.

  In addition, if the particle size distribution of the conductive particles is widened, it is possible to contain more conductive particles due to the effect of increasing the threshold value for forming a conductive path even if the crystal size of the insulating ceramic crystal particles is the same. The dielectric constant can be further increased.

[Production method of dielectric material]
The dielectric material manufacturing method according to the present embodiment is obtained by mixing a raw material powder of an insulating material, a raw material powder of conductive particles, and a dispersion medium to form a slurry, and spray-drying the slurry to form granules. Is fired under a pressure of 1 MPa or more and 100 MPa or less to form a composite sintered body.
Next, this manufacturing method will be described in detail.

First, a raw material powder of an insulating material, a raw material powder of conductive particles, and a dispersion medium are mixed to form a slurry.
As a dispersion medium used for this slurry, water and an organic solvent can be used. Examples of the organic solvent include monohydric alcohols such as methanol, ethanol, 2-propanol, butanol, and octanol and modified products thereof; alcohols belonging to monocyclic monoterpenes such as α-terpineol; carbs such as butyl carbitol. Tolls; Esters such as ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, butyl carbitol acetate, γ-butyrolactone; diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), Ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, diethyl Ethers such as lenglycol monoethyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; dimethylformamide, N, N-dimethylacetamide, Amides such as N-methylpyrrolidone are preferably used, and one or more of these solvents can be used.

A dispersant or a binder may be added when preparing this slurry.
As the dispersant and binder, for example, polycarboxylic acid salts such as polycarboxylic acid ammonium salt, organic polymers such as polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone are used.
Although it does not specifically limit as a dispersion process, A dispersion process is made | formed using dispersers, such as an ultrasonic homogenizer, a bead mill, and an ultrahigh pressure grinder.
If the raw material powder of insulating particles and the raw material powder of conductive particles are not mixed uniformly, the distribution of the conductive particles in the dielectric material obtained by the composite becomes non-uniform, and the electrical characteristics Since reproducibility and uniformity in the sintered body may be deteriorated, it is preferable to select a dispersion medium, a dispersant, and dispersion treatment conditions and to mix them uniformly.

The slurry is then spray dried by a spray drying method. As the spray drying apparatus, a spray dryer or the like is preferably used.
Here, the slurry is sprayed into a heated air stream and dried, so that only the dispersion medium is scattered in the insulating material while the insulating material and the conductive particles in the slurry are uniformly dispersed. A granulated powder in which conductive particles are uniformly dispersed is obtained.

Next, the granulated powder is fired under a pressure of 1 MPa or more and 100 MPa or less in a predetermined firing atmosphere to obtain a composite sintered body.
Here, as the firing atmosphere, when conductive silicon carbide (SiC) particles, molybdenum (Mo) particles, tungsten (W) particles, tantalum (Ta) particles, or the like is used as the conductive particles, oxidation of these is prevented. Since it is necessary, a non-oxidizing atmosphere, for example, an argon (Ar) atmosphere, a nitrogen (N ₂ ) atmosphere, or the like is preferable.

  Here, the reason for setting the pressure during firing to 1 MPa or more and 100 MPa or less is that when the pressure is less than 1 MPa, the density of the obtained sintered body is lowered, the corrosion resistance is lowered, and a dense sintered body is obtained. This is because the conductivity is increased and the use is limited when used as a member for a semiconductor manufacturing apparatus, and versatility is impaired. On the other hand, when the pressure exceeds 100 MPa, there is no problem with the density and conductivity of the obtained sintered body. This is because restrictions occur.

Moreover, the normal sintering temperature used for the insulating material to be used can be applied to the firing temperature. For example, when aluminum oxide is used as the insulating material, the temperature is preferably 1500 ° C. or higher and 1900 ° C. or lower.
The reason why the granulated powder is preferably fired at 1500 ° C. or more and 1900 ° C. or less is that if the firing temperature is less than 1500 ° C., the sintering is insufficient and a dense composite sintered body may not be obtained. On the other hand, if the firing temperature exceeds 1900 ° C., there is a risk that sintering proceeds excessively and abnormal grain growth or the like occurs, and as a result, a dense composite sintered body may not be obtained. Because.
Moreover, the firing time should just be sufficient time to obtain a precise | minute sintered compact, for example, is 1 to 6 hours.

  Thus, the density of the composite sintered body is improved while suppressing the grain growth of each of the insulating material and the conductive particles by simultaneously applying pressure of 1 MPa or more and 100 MPa or less when the granulated powder is fired. Can do.

Since the particle size distribution of the conductive particles in this composite sintered body changes depending on the raw materials used and the sintering of the conductive particles in the firing process, etc., the target characteristics can be adjusted by adjusting the raw materials used and the firing conditions. Can be obtained.
Control methods at the slurry production stage include a method using a conductive particle material having a wide particle size distribution, a method using a mixture of materials having different particle diameters, a mixture of an insulating material material and a conductive particle material. In this case, a method for controlling the aggregation state of the conductive particles, a method combining these, or the like is appropriately used.
Examples of the method of controlling by firing conditions include molding conditions, pressure in firing, atmosphere, firing temperature, and the like.

[Characteristics of dielectric materials]
Electrical characteristics such as dielectric strength, dielectric strength, etc. in the composite sintered body are the dispersion state of the conductive particles dispersed in the insulating material, the size of the insulating material particles, and the insulating properties. It varies depending on various factors such as the proportion of conductive particles in the material and the particle size distribution of the insulating material particles, and it is difficult to uniquely determine the relationship between the particle size distribution of the conductive particles and the electrical characteristics.
Therefore, a composite sintered body in which the particle size distribution of the conductive particles in the insulating material is changed by various particle size distribution methods is manufactured, and the optimum value is experimentally obtained from the evaluation result of the electrical characteristics. The method is used.

Among them, since the reproducibility of the experiment is good, the manufacturing conditions of the composite sintered body are made constant, and several types of conductive particles with different particle diameters are used as the conductive particles used as the raw material. A method of obtaining the optimum value by changing the ratio of the active particles is preferably used.
In addition, the optimum type and particle size of the conductive particles and the optimal ratio of the conductive particles in the insulating material are required, and in the case of test production or mass production of a composite sintered body having the same characteristics as this, By changing the manufacturing conditions of the conductive particles themselves so as to obtain an optimal particle size distribution, the electrical characteristics of the composite sintered body can be optimized even when one kind of conductive particles and insulating material is used. be able to.

[Electrical properties of composite sintered body]
(1) Withstand voltage characteristics The withstand voltage characteristics of the composite sintered body are measured by providing electrodes on both sides of the composite sintered body and gradually increasing the DC voltage applied to these electrodes. This is done by measuring the flowing current.

Here, a silicon wafer having an area of 10 cm ² or more is used as the electrode in consideration of the following “confirmation that dielectric breakdown is not formed in a pinhole”.
The withstand voltage of this composite sintered body, that is, the voltage at which the current value by voltage application increases due to dielectric breakdown and the current value becomes 1 nA / cm ² or more was applied to the base material of the electrostatic chuck. In this case, since it is necessary to have a value higher than the specification of the working voltage and withstand voltage, it is preferably 5 k / Vmm or more, more preferably 8 kV / mm or more, and 10 kV / mm or more. More preferably.

By the way, when a DC voltage is applied to these electrodes, electric charges are stored in these electrodes, so that the current value temporarily rises to 1 nA / cm ² or more as the voltage increases. Here, after a certain amount of charge is stored in these electrodes, the current value decreases. The current value measured here is the current value after the charge is stored. In this process, if dielectric breakdown proceeds in the composite sintered body, the current value continues to rise after the charge is stored due to the influence of this dielectric breakdown, and as a result, the current value gradually increases. Become.

(2) Dielectric breakdown characteristics The dielectric breakdown characteristics of this composite sintered body are measured on the electrodes of the composite sintered body after performing the above-mentioned withstand voltage measurement, for example, using a silicon wafer having an area of 10 cm ² or more as a measurement terminal. After the above withstand voltage measurement, there is a method of measuring the current value by applying the same voltage again using a measurement electrode smaller than the electrode used for the withstand voltage measurement, for example, a silicon chip cut into a 5 mm square. .

In a normal insulator, dielectric breakdown occurs instantaneously, and increases instantaneously until the allowable current value of the power source to which the voltage is applied is exceeded or the material and surrounding equipment are damaged by heat generation or discharge.
On the other hand, in the composite sintered body of the present embodiment, the current value gradually increases even when dielectric breakdown progresses in the composite sintered body. Signs of body dielectric breakdown can be detected. In addition, since dielectric breakdown is an irreversible phenomenon, even if dielectric breakdown has progressed during past use, measure the voltage again and compare it with the result measured before dielectric breakdown occurs. By confirming that the current value is increased, a sign of dielectric breakdown can be detected.

The composite sintered body of the present embodiment, when measuring the withstand voltage characteristics, that the time required for the current value due to insulation breakdown increases from 1 nA / cm ² to 100 nA / cm ² is not less than 3 seconds Preferably, it is 10 seconds or more, and more preferably 60 seconds or more.
The reason why the current value for starting the measurement of the time required to increase the current value due to the dielectric breakdown is set to 1 nA / cm ² is that if it is 1 nA / cm ² or less, it is difficult to distinguish it from noise of the measurement system. is there.
The current value for ending the measurement of the time required to increase the current value due to dielectric breakdown was set to 100 nA / cm ² because the silicon wafer is attracted as an electrostatic chuck when the current value is 100 nA / cm ² or more. This is because when the voltage is applied to the whole, the total amount of flowing current values may become too large.

If the time required for the above is preferably 3 seconds or more, more preferably 10 seconds or more, and even more preferably 60 seconds or more, the device in the wafer placed on the composite sintered body is destroyed by the current due to dielectric breakdown. The apparatus can be stopped by detecting a sign of dielectric breakdown of the composite sintered body before or before damaging another apparatus by electric discharge.
In addition, since dielectric breakdown is an irreversible phenomenon, even if the withstand voltage characteristics have deteriorated during past use, before using this composite sintered body, it must exceed the operating voltage and be By applying a voltage equal to or lower than the withstand voltage value of and measuring the current value, the sign of dielectric breakdown of the composite sintered body can be known.

  When this composite sintered body is used as a base material for an electrostatic chuck, since a voltage is applied to a wide area, the total amount of current value is increased, and therefore the accuracy of the current value detected per unit area is increased. Is possible. Further, by combining this composite sintered body with a highly accurate ammeter capable of detecting a small current value, an indication of dielectric breakdown can be detected at an earlier stage.

(3) Fractal nature of dielectric breakdown By widening the particle size distribution of the conductive particles dispersed in the insulating material of the composite sintered body, the fractal nature of the connection of the conductive particles and the fractal nature of the dielectric breakdown shape. Can be high.
Here, the fractal property of the dielectric breakdown refers to the degree of the number of branches of the conductive path caused by the dielectric breakdown in the composite sintered body, and the case where there are many branches of the conductive path is referred to as high fractal property.
In this composite sintered body, when the location of dielectric breakdown is formed in a pinhole shape, the pinhole is formed at one point or a plurality of points. There is a difference.

  As a method for judging the fractal nature of this dielectric breakdown for convenience, a measurement terminal, for example, a silicon chip cut into 5 mm squares is placed on the surface of the composite sintered body, and currents at a plurality of locations on this surface are placed. When the distribution of the value distribution is measured, that is, when the ratio (Amax / Amin) between the maximum value (Amax) and the minimum value (Amin) of the current value is less than a predetermined value, it is determined that “there is fractal”. A method of determining “no fractal property” when the value is equal to or greater than a predetermined value is adopted.

When the current value is simply measured in this manner, when the location of the dielectric breakdown is formed in a pinhole shape, the pinhole is formed at one point or a plurality of points. Amax / Amin) has a difference of 1000 times or more.
On the other hand, when the location of dielectric breakdown is not formed in a pinhole shape, the difference in the ratio (Amax / Amin) becomes small.
As a result, when the composite sintered body breaks down, the device is not damaged due to current concentration. In order to prevent the device from being damaged, a silicon chip cut to 5 mm square is placed on the surface of the composite sintered body and the current value distribution is measured. Variation, that is, the ratio (Amax / Amin) between the maximum value (Amax) and the minimum value (Amin) of the current value is preferably 1000 times or less. More preferably, the value is increased.

  When this composite sintered body is used as a base material for an electrostatic chuck, the electrostatic chuck has a voltage lower than the voltage applied at the time of evaluation. It tends to occur gradually due to damage due to or deterioration due to repeated use. Therefore, if the characteristic that the dielectric breakdown gradually proceeds is obtained by these evaluations, the characteristic that the dielectric breakdown gradually proceeds even when used as an electrostatic chuck can be obtained.

(3) Dielectric constant When the composite sintered body is used as a base material for an electrostatic chuck, the dielectric constant of the composite sintered body is preferably high in order to increase the adsorption force of the electrostatic chuck. Preferably, it is 13 or more, more preferably 15 or more.
In the case of a composite sintered body having a high dielectric constant, the withstand voltage may be low, and therefore it is preferable to adjust appropriately according to the required characteristics.

  As described above, according to the composite sintered body of the present embodiment, the conductive particles dispersed in the insulating material of the composite sintered body have an accumulated volume percentage of 10 volume% in the volume particle size distribution. The ratio of the particle diameter D10 of 0.2 μm or less, the cumulative volume percentage of 90% by volume to the particle diameter D90 of 2 μm or less, the cumulative volume percentage of 90% by volume, and the cumulative volume percentage of 10% by volume to the particle diameter D10 ( D90 / D10) is 3.0 or more, and the ratio (D90 / D50) of the particle size D90 with a cumulative volume percentage of 90% by volume to the particle size D50 with a cumulative volume percentage of 50% by volume is 1.4 or more. By increasing the particle size distribution of the conductive particles dispersed in the insulating material of the composite sintered body, the fractal dimension of the dielectric breakdown shape can be increased, and the dielectric material comprising this composite sintered body Insulation break Breaking can proceed gently. Therefore, by measuring the electrical resistance before or during use of the dielectric material made of the composite sintered body, a sign of dielectric breakdown can be known from the value of the electrical resistance. As a result, dielectric breakdown of the dielectric material made of this composite sintered body can be predicted in advance.

In addition, by using a material with high fractal properties for the composite sintered body, it is possible to disperse current due to dielectric breakdown, and even in the case where dielectric breakdown occurs, in the wafer placed on this composite sintered body Damage to your device can be eliminated.
In addition, by using a composite sintered body having a high fractal property, it becomes easy to obtain a characteristic that the dielectric breakdown gradually proceeds.
Further, by increasing the particle size distribution of the conductive particles dispersed in the insulating material of the composite sintered body, the dielectric constant can be increased while maintaining a high withstand voltage. Therefore, this composite sintered body can be applied to a Coulomb force type electrostatic chuck.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

"Example 1"
Mass of silicon carbide (SiC) powder having an average particle size of 0.05 μm, silicon carbide (SiC) powder having an average particle size of 0.5 μm, and silicon carbide (SiC) powder having an average particle size of 1.0 μm By mixing at a ratio of 50: 45: 5, SiC mixed powder was obtained.
Then, the SiC powder mixture is 8% by volume, the average aluminum oxide _(Al 2 _{O 3)} particle size 0.1μm powder were weighed so as to be 92% by volume, these SiC powder mix and _Al 2 _{O 3} The powder was put into pure water, dispersed for 5 hours with an ultrasonic disperser, and further dispersed for 4 hours with a planetary ball mill to obtain a dispersion.

Next, this dispersion was dried at 200 ° C. using a spray dryer to obtain Al ₂ O ₃ —SiC composite powder.
Next, this Al ₂ O ₃ —SiC composite powder was baked for 2 hours at 1650 ° C. under a pressure of 25 MPa in an argon (Ar) atmosphere using a hot press to obtain an Al ₂ O ₃ —SiC composite sintered body. Was made.
This composite sintered body was processed into a disk shape having a diameter of 100 mm and a thickness of 1.0 mm to produce the Al ₂ O ₃ —SiC composite sintered body of Example 1.

"Example 2"
An Al ₂ O ₃ —SiC composite sintered body of Example 2 was produced in the same manner as in Example 1, except that the SiC mixed powder was 11% by volume and the Al ₂ O ₃ powder was 89% by volume.

"Example 3"
An Al ₂ O ₃ —SiC composite sintered body of Example 3 was produced in the same manner as in Example 1, except that the SiC mixed powder was 9% by volume and the Al ₂ O ₃ powder was 91% by volume.

Example 4
Ultrasonic dispersion with 9% by volume of SiC powder having an average particle size of 0.05 μm, 91% by volume of Al ₂ O ₃ powder having an average particle size of 0.1 μm, a firing temperature of 1800 ° C., and a pressure of 40 MPa. An Al ₂ O ₃ —SiC composite sintered body of Example 4 was produced in the same manner as in Example 1 except that the dispersion treatment in the planetary ball mill was not performed after the dispersion treatment in the machine.

"Example 5"
An SiC powder having an average particle size of 0.03 μm, an SiC powder having an average particle size of 0.05 μm, and an SiC powder having an average particle size of 0.1 μm are mixed at a mass ratio of 1: 1: 1. Thus, a SiC mixed powder was obtained.
Next, in the same manner as in Example 1, except that the SiC mixed powder was 10% by volume and the aluminum oxide (Al ₂ O ₃ ) powder having an average particle diameter of 0.1 μm was 90% by volume, Example 5 An Al ₂ O ₃ —SiC composite sintered body was produced.

  In addition, the content rate (10 volume%) of SiC mixed powder produced the sample which changed content of the SiC mixed powder from 4 volume% to 13 volume% at 1 volume% intervals, and used these samples. When a composite sintered body was produced in the same manner as in Example 1, the content was set to 10% by volume, which is 3% by volume less than the content at which the electrical characteristics change from the insulator to the conductor.

"Example 6"
An Al ₂ O ₃ —SiC composite sintered body of Example 6 was produced in the same manner as in Example 1 except that the SiC mixed powder was 5% by volume and the Al ₂ O ₃ powder was 95% by volume.

"Example 7"
An Al ₂ O ₃ —SiC composite sintered body of Example 7 was produced in the same manner as in Example 1 except that the SiC mixed powder was 12% by volume and the Al ₂ O ₃ powder was 88% by volume.

"Example 8"
A SiC mixed powder was obtained in the same manner as in Example 1.
Next, this SiC mixed powder was weighed so that the volume of yttrium oxide (Y ₂ O ₃ ) powder having an average particle diameter of 0.1 μm was 10 volume% and 90 volume%, and these SiC mixed powder and Y ₂ O ₃ The powder was put into ion-exchanged water in a ball mill using Teflon (registered trademark) balls and a polyethylene pot and dispersed for 48 hours to obtain a dispersion.

Next, this dispersion was dried at 200 ° C. using a spray dryer to obtain a Y ₂ O ₃ —SiC composite powder.
Next, this Y ₂ O ₃ —SiC composite powder was baked for 1 hour at 1600 ° C. under a pressure of 40 MPa in an argon (Ar) atmosphere using a hot press, and a Y ₂ O ₃ —SiC composite sintered body was obtained. Was made.
This composite sintered body was processed into a disk shape having a diameter of 100 mm and a thickness of 1.0 mm to produce a Y ₂ O ₃ —SiC composite sintered body of Example 8.

  Note that the content of SiC mixed powder (10% by volume) was obtained by preparing a sample in which the content of SiC mixed powder was changed from 8% by volume to 15% by volume at intervals of 1% by the same method. When the bonded body was produced, the content was set to 10% by volume, which is 3% by volume less than the content at which the electrical characteristics change from the insulator to the conductor.

"Example 9"
A SiC mixed powder was obtained in the same manner as in Example 1.
Next, 9% by volume of this SiC mixed powder, 85% by volume of silicon nitride (Si ₃ N ₄ ) powder having an average particle size of 0.2 μm, and yttrium oxide (Y) having an average particle size of 0.05 μm as a sintering aid. ₂ O ₃₎ were weighed so as powder becomes 6 vol%, these SiC mixed powder, the _Si 3 _{N 4} powder and _Y 2 _{O 3} powder was used Teflon balls and polyethylene pot The solution was put into ethanol in a ball mill and dispersed for 48 hours to obtain a dispersion.

Subsequently, ethanol was extracted from the above dispersion using an evaporator, and then vacuum-dried to obtain a Si ₃ N ₄ —SiC composite powder.
Next, this Si ₃ N ₄ —SiC composite powder was baked at 1800 ° C. under a pressure of 35 MPa for 2 hours in a nitrogen (N ₂ ) atmosphere using a hot press, and the Si ₃ N ₄ —SiC composite sintered The body was made.
This composite sintered body was processed into a disk shape having a diameter of 100 mm and a thickness of 1.0 mm to produce the Si ₃ N ₄ —SiC composite sintered body of Example 9.

  Note that the content of SiC mixed powder (9% by volume) was determined by preparing a sample in which the content of SiC mixed powder was changed from 5% by volume to 15% by volume at intervals of 1% by the same method. When the bonded body was produced, the content rate was set to 9% by volume, which is 3% by volume less than the content rate at which the electrical characteristics change from the insulator to the conductor.

"Comparative Example 1"
A commercially available Al ₂ O ₃ sintered body having a purity of 99.9% was processed into a disk shape having a diameter of 100 mm and a thickness of 1.0 mm to produce an Al ₂ O ₃ sintered body of Comparative Example 1.

“Comparative Example 2”
The Al ₂ O ₃ —SiC composite sintering of Comparative Example 2 was performed in the same manner as in Example 1 except that only silicon carbide (SiC) powder having an average particle diameter of 0.3 μm was used instead of the SiC mixed powder. The body was made.

“Comparative Example 3”
9% by volume of SiC powder having an average particle size of 0.05 .mu.m, the _Al 2 _{O 3} powder having an average particle size of 0.1μm and 91% by volume, in the same manner as in Example 1, _Al 2 _{O 3} of Comparative Example 3 A SiC composite sintered body was produced.

“Comparative Example 4”
An Al ₂ O ₃ —SiC composite sintered body of Comparative Example 4 was produced in the same manner as in Example 1 except that the SiC mixed powder was 1% by volume and the Al ₂ O ₃ powder was 99% by volume.

“Comparative Example 5”
An Al ₂ O ₃ —SiC composite sintered body of Comparative Example 5 was produced in the same manner as in Example 1, except that the SiC mixed powder was 13 vol% and the Al ₂ O ₃ powder was 87 vol%.

“Comparative Example 6”
The yttrium oxide _(Y 2 _{O 3)} powder having an average particle diameter of 0.1 [mu] m, using a hot press, argon (Ar) atmosphere, 1600 ° C., baked for one hour at a pressure 40 _MPa, Y 2 _{O 3} sintered A ligature was prepared.
This sintered body was processed into a disk shape having a diameter of 100 mm and a thickness of 1.0 mm to produce a Y ₂ O ₃ sintered body of Comparative Example 6.

“Comparative Example 7”
Silicon nitride (Si ₃ N ₄ ) powder with an average particle size of 0.2 μm is 93% by volume, and yttrium oxide (Y ₂ O ₃ ) powder with an average particle size of 0.05 μm is 7% by volume as a sintering aid. The Si ₃ N ₄ powder and the Y ₂ O ₃ powder were put into ethanol in a ball mill using a Teflon (registered trademark) ball and a polyethylene pot, and dispersed for 48 hours. Got.

Subsequently, ethanol was extracted from the above dispersion using an evaporator, and then vacuum-dried to obtain Si ₃ N ₄ powder.
Next, this Si ₃ N ₄ powder was baked for 2 hours at 1800 ° C. under a pressure of 35 MPa in a nitrogen (N ₂ ) atmosphere using a hot press to prepare a Si ₃ N ₄ sintered body.
This sintered body was processed into a disk shape having a diameter of 100 mm and a thickness of 1.0 mm, and a Si ₃ N ₄ sintered body of Comparative Example 7 was produced.

"Evaluation of composite sintered body or sintered body"
(1) Particle size and particle size distribution The particle size and particle size distribution of the SiC particles in each of the composite sintered bodies of Examples 1 to 9 and Comparative Examples 2 to 5 were measured by an SEM observation method.
Here, the particle diameters D10, D50, D90, the ratio (D90 / D50) and the ratio (D90 / D10) of the SiC particles were obtained by measurement.
The measurement results are shown in Table 1.

In addition, since the particle | grains below 0.04 micrometer may be unable to be discriminate | determined by the measurement by a SEM observation method, about "the presence or absence of electroconductive fine particles" about each compound sintered body of Examples 1-9 and Comparative Examples 2-5, ie, Whether or not conductive fine particles of 0.04 μm or less were contained in the composite sintered body was 0.001% or more and 5% or less was observed by a TEM observation method.
Here, the particle diameter of each of the 500 conductive particles is measured, and when the conductive fine particles of 0.04 μm or less are contained in 0.001% or more and 5% or less, it is determined that the conductive fine particles are present. A case where the conductive fine particles were not contained in an amount of 0.001% or more and 5% or less was judged to be no conductive fine particles, and was evaluated as “x”.

(2) Dielectric strength and dielectric breakdown time Each of the composite sintered bodies or sintered bodies of Examples 1 to 9 and Comparative Examples 1 to 7 was sandwiched between 35 mm square silicon wafers so that no creeping discharge occurred between the electrodes. Increase the voltage to a predetermined measurement voltage every 1 kV / mm up to 10 kV / mm, and every 0.5 kV / mm above 10 kV / mm, and measure the current value after holding this predetermined measurement voltage for 1 minute did.
Here, when the current value after holding for 1 minute was 1 nA / cm ² or less, the voltage was further increased by 1 kV / mm or 0.5 kV / mm, and the measurement was continued.
In addition, when the current value is 1 nA / cm ² or more and the ammeter value decreases after 1 minute, the measurement is continued by increasing the voltage after holding the current meter to 1 nA / cm ² . .

Further, when the current value was increased and exceeded 100 nA / cm ² , the applied voltage was set to a withstand voltage value, and the dielectric breakdown time was set to 1 second or less.
In the case where the current value is increasing and the current value is 100 nA / cm ² or less, the time from when the voltage starts to reach 100 nA / cm ² is defined as the dielectric breakdown time.
In addition, when it did not exceed 100 nA / cm ² even after 1 minute or more after the holding, the held voltage was set to a withstand voltage value, and the dielectric breakdown time was set to 60 seconds or more.
The measurement results are shown in Table 2.

(3) Fractal property of dielectric breakdown A 12 mm square silicon chip was placed as an electrode at the measurement location of the withstand voltage characteristic, and the distribution of the current value of the composite sintered body or sintered body was measured using this electrode. Fractal property of fracture was evaluated.
Here, when it was confirmed that the applied voltage was 100 nA / cm ² or more with the withstand voltage value as the upper limit, the measurement at the measurement point was completed. This operation was repeated, and nine current values were measured from the place where the dielectric breakdown test was performed.

When the ratio of the maximum current value to the minimum value (Amax / Amin) at 9 points measured was 1000 or less, it was judged that there was fractal property, and the evaluation result was “◯”.
In addition, when the ratio between the maximum value and the minimum value (Amax / Amin) is greater than 1000, a detailed distribution of current values is measured in order to confirm that dielectric breakdown occurs in a pinhole shape. did. Therefore, measurement is performed while moving a 12 mm square silicon chip at intervals of 2 mm, and the area of a region having a current value of 100 nA / cm ² or more is obtained. If this area is a spot of 4 mm ² or less, dielectric breakdown occurs. Since it occurred in a pinhole shape, it was judged that there was no fractal property, and the evaluation result was “x”. Even if the location where dielectric breakdown occurs can be visually confirmed due to damage, etc., it is judged that there is no fractal property. In this case as well, the evaluation result is “x”. Is not generated in the form of a pinhole, but “Δ” is indicated when the variation in current caused by dielectric breakdown is large.
The measurement results are shown in Table 2.

(4) Dielectric Constant The dielectric constant at 1 kHz of each of the composite sintered bodies or sintered bodies of Examples 1 to 9 and Comparative Examples 1 to 7 was measured using a dielectric measurement system 126096W (manufactured by Toyo Corporation).
The measurement results are shown in Table 2.

Claims (5)

A dielectric material comprising a composite sintered body in which conductive particles are dispersed in an insulating material,
The insulating material is Al ₂ O ₃ , Y ₂ O ₃ or Si ₃ N ₄ ,
The conductive particles are SiC particles,
The composite sintered body is an Al ₂ O ₃ —SiC composite sintered body, a Y ₂ O ₃ —SiC composite sintered body, or a Si ₃ N ₄ —SiC composite sintered body,
The content of the conductive particles is 4% by mass or more and 20% by mass or less,
The conductive particles have a particle size D10 having a cumulative volume percentage of 10% by volume in the volume particle size distribution of 0.2 μm or less, a particle diameter D90 of 90% by volume, and 2 μm or less, and a cumulative volume percentage of 90%. The ratio (D90 / D10) of the cumulative volume percentage of the volume% particle diameter D90 to the 10 volume% particle diameter D10 is 3.0 or more, and the cumulative volume percentage of the particle diameter D90 whose cumulative volume percentage is 90 volume% is 50. The ratio of volume% to particle diameter D50 (D90 / D50) is 1.4 or more,
Breakdown characteristics were evaluated for the dielectric material after the following withstand voltage test, satisfying the following condition, a dielectric material.
(anti-voltage test)
A dielectric material having a thickness of 1.0 mm is sandwiched between first electrodes, a predetermined measurement voltage is applied between the first electrodes and held for 1 minute, and then a current value flowing between the first electrodes is 1 nA. The measured voltage when the current value is higher than / cm ² is defined as a withstand voltage value.
(Dielectric breakdown characteristics)
A second electrode smaller than the first electrode is disposed at a position on the surface of the dielectric material where the first electrode is disposed in the withstand voltage test to sandwich the dielectric material, and A current value that flows when the same voltage as the withstand voltage value is applied between the second electrodes is measured.
(conditions)
When nine positions of the second electrode are selected at the position and the current values at nine points are measured, the ratio between the maximum value (Amax) and the minimum value (Amin) among the nine current values ( Amax / Amin) is 1000 times or less. The dielectric material according to claim 1, wherein the conductive particles include 0.001% or more of particles of 0.04 μm or less. The dielectric material according to claim 1 or 2, characterized in that the time required for the current value due to insulation breakdown increases from 1 nA / cm ² to 100 nA / cm ² is not less than 3 seconds. The dielectric material according to any one of claims 1 to 3, wherein a relative dielectric constant is 11 or more.   The dielectric material according to any one of claims 1 to 4, wherein a withstand voltage is 5 kV / mm or more.