JP2020055715A - Dielectric material, method for producing the same, and electrostatic chuck device - Google Patents

Abstract

To provide a dielectric material capable of improving thermal uniformity of an electrostatic chuck, and to provide a method for producing the same and an electrostatic chuck device.SOLUTION: A dielectric material comprises a composite sintered body in which a metal oxide is used as a main phase, wherein in the composite sintered body: a plurality of crystal grains are oriented substantially in the same direction; length of the crystal grains in a minor axis direction is 0.1 μm or more and 1.0 μm or less; length of the crystal grains in a major axis direction is 0.2 μm or more and 10 μm or less; and an aspect ratio ( (the length in the major axis direction)/(the length in the minor axis direction)) is 2 or more.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a dielectric material, a method for manufacturing the dielectric material, and an electrostatic chuck device.

2. Description of the Related Art In recent years, in a semiconductor manufacturing apparatus that performs a plasma process, an electrostatic chuck device that can easily attach and fix a plate-shaped sample (wafer) to a sample stage and maintain the wafer at a desired temperature. Is used.
An oriented alumina sintered body may be used for the dielectric layer of the electrostatic chuck device (see Patent Document 1).

  In recent years, devices using semiconductors tend to be highly integrated. Therefore, at the time of manufacturing a device, fine processing technology of wiring and three-dimensional mounting technology are required. In carrying out such a processing technique, a semiconductor manufacturing apparatus is required to reduce the difference in the in-plane temperature distribution of the wafer (in other words, the temperature difference between the plasma irradiation surface of the wafer and the wafer fixing surface). Therefore, helium gas is flown through the back surface of the wafer for temperature control through the electrostatic chuck member for fixing the wafer. Due to the temperature control, the gas pressure of the flowing helium gas tends to increase. On the other hand, a high suction force (dielectric constant) is required to fix the wafer.

International Publication No. WO 2017/057273

However, when the dielectric constant is increased, the loss coefficient (dielectric constant × dielectric loss tangent) increases, and the high-frequency transmittance decreases. Then, there is a problem that the dielectric layer constituting the electrostatic chuck absorbs the plasma and generates heat, so that the uniformity of the electrostatic chuck cannot be secured.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a dielectric material capable of improving the thermal uniformity of an electrostatic chuck, a method for manufacturing the dielectric material, and an electrostatic chuck device.

That is, the present invention includes the following inventions [1] to [6].
[1] A dielectric material composed of a composite sintered body containing a metal oxide as a main phase, wherein the composite sintered body has a plurality of crystal grains oriented in substantially the same direction, The length in the axial direction is 0.1 μm or more and 1.0 μm or less, the length in the long axis direction is 0.2 μm or more and 10 μm or less, and the aspect ratio (length in the long axis direction / length in the short axis direction). ) Is 2 or more.
[2] The dielectric material according to [1], wherein the metal oxide is aluminum oxide.
[3] The dielectric material according to [1] or [2], wherein the composite sintered body contains silicon carbide as a subphase.
[4] In the powder X-ray diffraction measurement of the composite sintered body using CuKα radiation, a diffraction angle 2θ exists around 64.5 ° with respect to a (113) diffraction peak at around 68 ° with a (110) diffraction. The dielectric material according to any one of [1] to [3], wherein a peak intensity ratio (I ₁₁₀ / I ₁₁₃ ) is 0.5 or more.
[5] The method for producing a dielectric material according to any one of [1] to [4], wherein a step of obtaining a mixture containing a metal oxide that is a main phase is performed, and the mixture is subjected to uniaxial pressing. A method for producing a dielectric material, comprising a sintering step of sintering, wherein the sintering step is performed by a hot forge method and is performed under a pressure condition exceeding 20 MPa.
[6] A substrate, wherein the dielectric material according to any one of [1] to [4] is used as a forming material, and a main surface of which is a mounting surface on which a plate-like sample is mounted; An electrostatic chucking electrode provided on the opposite side of the mounting surface or inside the base.

  ADVANTAGE OF THE INVENTION According to this invention, the dielectric material which can improve the thermal uniformity of an electrostatic chuck, the manufacturing method of this dielectric material, and an electrostatic chuck apparatus can be provided.

It is a sectional view showing the electrostatic chuck device of this embodiment. 3 is an SEM image of the dielectric material of Example 1. 9 is an SEM image of a dielectric material of Comparative Example 1.

<Dielectric material>
The dielectric material of the present embodiment is composed of a composite sintered body having a metal oxide as a main phase. In the composite sintered body, a plurality of crystal grains are oriented in substantially the same direction.
The length of the crystal grains in the short axis direction is 0.1 μm or more and 1.0 μm or less, the length in the long axis direction is 0.2 μm or more and 10 μm or less, and the aspect ratio (length of the long axis direction / short axis direction) (Length in the direction) is 2 or more.

≪Composite sintered body≫
The composite sintered body used in the present embodiment may be a sintered body composed of a metal oxide or a composite sintered body of a metal oxide and other components. In the present embodiment, a composite sintered body of a metal oxide and silicon carbide is preferably used.
The crystal grains of the composite sintered body used in the present embodiment are preferably flat. Further, the length of the crystal grain in the minor axis direction is 0.1 μm or more and 1.0 μm or less. In the present embodiment, the length of the crystal grains in the minor axis direction is preferably 0.15 μm or more, more preferably 0.18 μm or more, and particularly preferably 0.2 μm or more. The length of the crystal grain in the minor axis direction is preferably 0.8 μm or less, more preferably 0.7 μm or less, and particularly preferably 0.5 μm or less.
The above upper limit and lower limit can be arbitrarily combined.

The length of the crystal grains of the composite sintered body used in the present embodiment in the major axis direction is 0.2 μm or more and 10 μm or less. In the present embodiment, the thickness is preferably 0.5 μm or more, more preferably 1.0 μm or more, and particularly preferably 2.0 μm or more. Moreover, it is preferably 8 μm or less, more preferably 6 μm or less, particularly preferably 5 μm or less.
The above upper limit and lower limit can be arbitrarily combined.

  The aspect ratio of the crystal grains of the composite sintered body used in the present embodiment is 2 or more, preferably 5 or more, more preferably 10 or more, and particularly preferably 20 or more.

In the present embodiment, the “length in the long axis direction” and the “length in the short axis direction” can be calculated by the following method.
Using a SEM, a cross section of the composite sintered body is observed at a magnification at which crystal grains can be visually recognized. For each of the observed crystal grains, the maximum value of the width in the direction in which the width is maximum is defined as “length in the major axis direction”. Then, the maximum value in the direction orthogonal to the “length in the long axis direction” is defined as the “length in the short axis direction”, and the average value of the “length in the long axis direction” and the “length in the short axis direction” is calculated. I do.

In the present embodiment, the plurality of crystal grains are oriented in substantially the same direction.
"Orientation in substantially the same direction" means, for example, a cross section of the composite sintered body of the present embodiment having a disk shape as described later, which is cut in a thickness direction, and the cross section is observed at a magnification at which crystal grains are visible. This means that the major axis direction of the crystal grains is oriented in substantially the same direction.
In addition, when the composite sintered body used in the present embodiment is observed from the direction of a plan view, the crystal grains may be radially oriented from the center to the outside.

Since the plurality of crystal grains are oriented in substantially the same direction, the thermal conductivity in the in-plane direction is higher than the thermal conductivity in the inter-plane direction, and the in-plane uniform heat is promoted.
Here, the “in-plane direction” means a two-dimensional direction in which crystal grains spread. "Inter-plane direction" means the direction in which crystal grains are stacked.

As the metal oxide used in the present embodiment, aluminum oxide (Al ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), mullite (3Al ₂ O ₃ .2SiO ₂ ), magnesium oxide (MgO), 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), A metal consisting of only one selected from the group of cerium oxide (CeO ₂ ) or a mixture of two or more kinds can be exemplified.

  In this embodiment, the metal oxide is preferably aluminum oxide among the above.

In the present embodiment, the composite sintered body preferably contains silicon carbide as a subphase.
Silicon carbide (SiC) contained in the composite sintered body includes crystal grains having an α-SiC type crystal structure (hereinafter, α-SiC grains) and crystal grains having a β-SiC type crystal structure (hereinafter, β -SiC grains).

  In the composite sintered body of the present embodiment, the crystal grains of SiC as the subphase are dispersed in the crystal grain boundaries and in the crystal grains of the main phase formed by sintering the crystal grains of the metal oxide.

  In the composite sintered body of the present embodiment, the content of SiC is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 10 parts by mass or less based on 100 parts by mass of the metal oxide.

In the composite sintered body of the present embodiment, in the powder X-ray diffraction measurement using CuKα ray, the diffraction angle 2θ exists around 64.5 ° with respect to the diffraction peak existing at around 68 ° (113) (110) (110). The diffraction peak intensity ratio (I ₁₁₀ / I ₁₁₃ ) is preferably 0.5 or more, more preferably 0.7 or more, and particularly preferably 1.0 or more.
When the intensity ratio of the diffraction peaks (I ₁₁₀ / I ₁₁₃ ) is in the above range, the composite sintered body has flatter crystal grains and promotes uniform heat in the in-plane direction.

<Method of manufacturing dielectric material>
The method for producing a dielectric material according to the present embodiment includes a step of obtaining a mixture containing a metal oxide as a main phase, and a sintering step of sintering the mixture under uniaxial pressure. In the present embodiment, the sintering step is performed by a hot forging method. A pre-oxidation step may be included as an optional step.

[Step of obtaining a mixture]
As a step of obtaining a mixture containing the metal oxide as the main phase, for example, the metal oxide as the main phase and the sub-phase material are dispersed using a disperser such as an ultrasonic homogenizer, a bead mill, or an ultra-high pressure grinder. It is preferable to mix by dispersing in a medium.

  If the metal oxide as the main phase and the sub-phase material are not uniformly mixed, the distribution of SiC particles in the composite sintered body obtained by composite becomes non-uniform, and the reproducibility of electrical characteristics and The uniformity in the sintered body may be deteriorated. Therefore, it is preferable to appropriately select a dispersion medium, a dispersant, and dispersion treatment conditions, and to uniformly mix them. Note that the distribution of SiC particles may be such that the distribution of secondary particle diameters in which single particles are aggregated is uniform.

  The insulating particles and SiC particles dispersed in the dispersion medium are converted into composite particles using a drying device such as a spray drier.

[Optional step: pre-oxidation step]
The method for producing a dielectric material according to the present embodiment may include a step of subjecting the silicon carbide particles to be used to a heat treatment in an oxidizing atmosphere to previously oxidize the surface of the silicon carbide particles. Hereinafter, the oxidation treatment is referred to as “pre-oxidation”.

  The temperature condition of the pre-oxidation is preferably, for example, 300 ° C. or more and 500 ° C. or less. When the pre-oxidation temperature is 300 ° C. or higher, the surface of the silicon carbide particles can be oxidized. Further, when the pre-oxidation temperature is 500 ° C. or less, the oxidation of the surface of the silicon carbide particles does not proceed excessively. For example, when the oxidation temperature is set to 600 ° C. or higher, the oxidation of the surface of the silicon carbide particles proceeds excessively, and as a result, the silicon carbide particles may be bonded to each other via an oxide film on the particle surface, and may be coarsened.

  The pre-oxidation time is preferably 10 hours or more. If the pre-oxidation time is less than 10 hours, the oxidation does not proceed sufficiently. The pre-oxidation time may be long (for example, 50 hours), but after a certain amount of oxide film is formed, the amount of oxide film hardly changes. Therefore, the pre-oxidation time is preferably, for example, 10 hours or more and 20 hours or less.

  By pre-oxidizing the silicon carbide particles, the hydrophilicity of the silicon carbide particles is increased. Thereby, the dispersibility of the silicon carbide particles in the slurry is improved.

[Sintering process]
The step of sintering the mixture obtained in the above step under uniaxial pressure to obtain a composite fired product is performed by a hot forging method.
The firing step includes a main firing step performed by a hot forging method as an essential step, and may include an optional temporary firing step before the main firing step.

・ Preliminary firing step In the preliminary firing step, sintering is performed at a temperature lower than that of the main firing step, and when the preliminary firing step is completed, sintering is performed under the condition that the relative density of the sintered body is densified to 95% or more. Is preferred.
The sintering temperature in the temporary sintering step is preferably from 1300 ° C to 1700 ° C, more preferably from 1400 ° C to 1700 ° C. In order to sufficiently perform sintering, it is preferable to hold for one hour or more.
At that time, the pressing pressure of the sintered body is preferably 20 MPa or more, more preferably 30 MPa or more.

-Main firing step The main firing step is performed by a hot forging method. Specifically, when pressurizing in a uniaxial direction, pressurization is performed while being released without holding in a direction orthogonal to the pressing direction. By applying pressure in this manner, crystal grains in which the major axes of the crystal grains are arranged in a direction perpendicular to the pressure axis can be manufactured.
The firing step can be performed by a hot forging method using a die. In this case, a material that plastically deforms at the sintering temperature may be selected.

As the sintering condition in the hot forging method, the pressure is set under a pressure condition exceeding 20 MPa, and is preferably 25 MPa or more, more preferably 30 MPa or more.
By performing sintering while applying uniaxial pressure at the above pressure, crystal grains having a high aspect ratio can be obtained.

The sintering temperature in the main sintering step is preferably 1750 ° C. or more and 1900 ° C. or less.
Further, the heating rate is preferably from 2 ° C./min to 10 ° C./min, more preferably from 3 ° C./min to 5 ° C./min.
The time for maintaining the above sintering temperature is preferably 30 minutes or more and 10 hours or less, more preferably 1 hour or more and 8 hours or less.

  By performing the firing step by the hot forging method, the length of the crystal grains in the minor axis direction and the major axis direction, and the aspect ratio can be controlled within the scope of the present invention. Further, by performing the hot forging method, the crystal grains of the sintered body can be controlled to have a flat shape.

<Electrostatic chuck device>
Hereinafter, the electrostatic chuck device according to the present embodiment will be described with reference to FIG. In all of the following drawings, dimensions, ratios, and the like of the components are appropriately changed in order to make the drawings easy to see.

FIG. 1 is a sectional view showing the electrostatic chuck device of the present embodiment. The electrostatic chuck device 1 according to the present embodiment includes a disc-shaped electrostatic chuck portion 2 having one main surface (upper surface) side as a mounting surface, and a statically disposed, provided below the electrostatic chuck portion 2. A temperature-adjusting base portion 3 which has a thickness and adjusts the temperature of the electro-chuck portion 2 to a desired temperature. The electrostatic chuck 2 and the temperature adjusting base 3 are bonded to each other via an adhesive layer 8 provided between the electrostatic chuck 2 and the temperature adjusting base 3.
Hereinafter, description will be made in order.

(Electrostatic chuck)
The electrostatic chuck unit 2 includes a mounting plate 11 whose upper surface is a mounting surface 11 a on which a plate-shaped sample W such as a semiconductor wafer is mounted, and a bottom side of the mounting plate 11 integrated with the mounting plate 11. A supporting plate 12 for supporting the electrodes, and an electrostatic attraction electrode 13 provided between the mounting plate 11 and the supporting plate 12 and an insulating layer 14 for insulating the periphery of the electrostatic attraction electrode 13. doing. The mounting plate 11 and the support plate 12 correspond to the “base” in the present invention. The base provided in the electrostatic chuck device of the present embodiment uses the dielectric material of the present invention as a forming material.

  The mounting plate 11 and the support plate 12 are disk-shaped members having the same shape of the superposed surfaces. The mounting plate 11 and the support plate 12 are made of a ceramic sintered body having mechanical strength and durability against corrosive gas and its plasma. The mounting plate 11 and the support plate 12 will be described later in detail.

  A plurality of projections 11b whose diameter is smaller than the thickness of the plate-shaped sample are formed on the mounting surface 11a of the mounting plate 11 at predetermined intervals, and these projections 11b support the plate-shaped sample W.

  The overall thickness including the mounting plate 11, the support plate 12, the electrostatic attraction electrode 13, and the insulating material layer 14, that is, the thickness of the electrostatic chuck portion 2 is, for example, 0.7 mm or more and 5.0 mm or less. is there.

  For example, if the thickness of the electrostatic chuck 2 is less than 0.7 mm, it is difficult to secure the mechanical strength of the electrostatic chuck 2. When the thickness of the electrostatic chuck unit 2 exceeds 5.0 mm, the heat capacity of the electrostatic chuck unit 2 increases, the thermal responsiveness of the placed plate-like sample W deteriorates, and the horizontal direction of the electrostatic chuck unit 2 decreases. Due to the increase in heat transfer, it becomes difficult to maintain the in-plane temperature of the plate-shaped sample W in a desired temperature pattern. In addition, the thickness of each part described here is an example, and is not limited to the above range.

  The electrostatic chucking electrode 13 is used as an electrostatic chucking electrode for generating an electric charge and fixing the plate-shaped sample W by the electrostatic chucking force. Adjusted.

Electrode 13 for electrostatic attraction is made of aluminum oxide-tantalum carbide (Al ₂ O ₃ -Ta ₄ C ₅ ) conductive composite sintered body, aluminum oxide-molybdenum carbide (Al ₂ O ₃ -Mo ₂ C) conductive composite firing. Sintered body, aluminum oxide-tungsten (Al ₂ O ₃ -W) conductive composite sintered body, aluminum oxide-silicon carbide (Al ₂ O ₃ -SiC) conductive composite sintered body, aluminum nitride-tungsten (AlN-W) ) conductive composite sintered body, an aluminum nitride - tantalum (AlN-Ta) conductive composite sintered body of yttrium oxide - molybdenum (Y 2 _{O 3 -Mo)} conductive composite sintered body or the like of the conductive ceramics or, It is preferably formed of a high melting point metal such as tungsten (W), tantalum (Ta), molybdenum (Mo).

  Although the thickness of the electrostatic attraction electrode 13 is not particularly limited, for example, a thickness of 0.1 μm or more and 100 μm or less can be selected, and a thickness of 5 μm or more and 20 μm or less is more preferable.

  If the thickness of the electrostatic attraction electrode 13 is less than 0.1 μm, it is difficult to secure sufficient conductivity. If the thickness of the electrostatic attraction electrode 13 exceeds 100 μm, the thickness of the electrostatic attraction electrode 13 and the mounting plate 11 and the supporting plate 12 are reduced due to the difference in the coefficient of thermal expansion between the mounting plate 11 and the support plate 12. Cracks are likely to occur at the joint interface between the plate 11 and the support plate 12.

  The electrostatic adsorption electrode 13 having such a thickness can be easily formed by a film forming method such as a sputtering method or an evaporation method, or a coating method such as a screen printing method.

  The insulating material layer 14 surrounds the electrode 13 for electrostatic attraction and protects the electrode 13 for electrostatic attraction from corrosive gas and its plasma, and at the boundary between the mounting plate 11 and the support plate 12, The outer peripheral region other than the attraction electrode 13 is joined and integrated, and the same composition or main component as the material forming the mounting plate 11 and the support plate 12 is formed of the same insulating material.

(Base for temperature adjustment)
The temperature adjusting base portion 3 is for adjusting the temperature of the electrostatic chuck portion 2 to a desired temperature, and has a thick disk shape. As the temperature adjusting base 3, for example, a liquid cooling base or the like in which a flow path 3 </ b> A for circulating a refrigerant is formed is preferable.

There is no particular limitation on the material constituting the temperature control base 3 as long as it is a metal having excellent thermal conductivity, conductivity, and workability, or a composite material containing these metals. For example, aluminum (Al), aluminum alloy, copper (Cu), copper alloy, stainless steel (SUS) and the like are preferably used. It is preferable that at least the surface of the temperature control base portion 3 exposed to plasma is subjected to alumite treatment or is formed with an insulating film such as aluminum oxide (Al ₂ O ₃ , alumina). Hereinafter, in this specification, aluminum oxide is referred to as “Al ₂ O ₃ ”.

  An insulating plate 7 is adhered to the upper surface side of the temperature adjusting base 3 via an adhesive layer 6. The adhesive layer 6 is made of a heat-resistant and insulating sheet-like or film-like adhesive resin such as a polyimide resin, a silicon resin, and an epoxy resin. The adhesive layer has a thickness of, for example, about 5 to 100 μm. The insulating plate 7 is made of a heat-resistant resin thin plate, sheet, or film such as a polyimide resin, an epoxy resin, or an acrylic resin.

It should be noted that the insulating plate 7 may be an insulating ceramic plate instead of the resin sheet, or may be a sprayed film having an insulating property such as Al ₂ O ₃ .

(Focus ring)
The focus ring 10 is an annular member in plan view placed on the peripheral portion of the temperature adjustment base 3. The focus ring 10 is made of, for example, a material having the same electrical conductivity as the wafer placed on the placement surface. By arranging such a focus ring 10, the electrical environment with respect to the plasma at the peripheral portion of the wafer can be made substantially coincident with that of the wafer, and the difference or deviation in plasma processing between the central portion and the peripheral portion of the wafer can be achieved. Can hardly occur.

(Other components)
A power supply terminal 15 for applying a DC voltage to the electrostatic attraction electrode 13 is connected to the electrostatic attraction electrode 13. The power supply terminal 15 is inserted into a through hole 16 that penetrates the temperature control base 3, the adhesive layer 8, and the support plate 12 in the thickness direction. An insulator 15a having an insulating property is provided on the outer peripheral side of the power supply terminal 15, and the insulator 15a insulates the power supply terminal 15 from the metal temperature adjustment base 3.

  Although the power supply terminal 15 is shown as an integral member in the figure, a plurality of members may be electrically connected to form the power supply terminal 15. Since the power supply terminal 15 is inserted into the temperature adjustment base 3 and the support plate 12 having different thermal expansion coefficients, for example, the portions inserted into the temperature adjustment base 3 and the support plate 12 are respectively It is good to constitute with a different material.

The material of the portion (extraction electrode) of the power supply terminal 15 that is connected to the electrostatic attraction electrode 13 and inserted into the support plate 12 is particularly limited as long as it is a conductive material having excellent heat resistance. Although not a thing, it is preferable that the coefficient of thermal expansion approximates the coefficient of thermal expansion of the electrode 13 for electrostatic attraction and the support plate 12. For _example, it made of a conductive ceramic material such as Al ₂ O 3 -TaC.

  The portion of the power supply terminal 15 inserted into the temperature control base 3 is made of, for example, a metal material such as tungsten (W), tantalum (Ta), molybdenum (Mo), niobium (Nb), and Kovar alloy. Become.

  These two members are preferably connected by a silicon-based conductive adhesive having flexibility and electric resistance.

  A heater element 5 is provided on the lower surface side of the electrostatic chuck section 2. The heater element 5 is, for example, a non-magnetic metal thin plate having a constant thickness of 0.2 mm or less, preferably about 0.1 mm, for example, a titanium (Ti) thin plate, a tungsten (W) thin plate, a molybdenum (Mo) thin plate. It can be obtained by processing the entire contour of a desired heater shape, for example, a meandering strip-shaped conductive thin plate, into an annular shape by photolithography or laser processing.

  Such a heater element 5 may be provided by bonding a non-magnetic metal thin plate to the electrostatic chuck 2 and then processing and molding it on the surface of the electrostatic chuck 2. The heater element 5 may be provided by performing transfer printing on the surface of the electrostatic chuck section 2.

  The heater element 5 is adhered and fixed to the bottom surface of the support plate 12 by a sheet-like or film-like adhesive layer 4 made of a silicon resin or an acrylic resin having a uniform thickness and heat resistance and insulating properties.

  A power supply terminal 17 for supplying power to the heater element 5 is connected to the heater element 5. The material constituting the power supply terminal 17 may be the same as the material constituting the power supply terminal 15 described above. The power supply terminals 17 are provided so as to penetrate through holes 3b formed in the temperature adjustment base portion 3, respectively.

  A temperature sensor 20 is provided on the lower surface side of the heater element 5. In the electrostatic chuck device 1 of the present embodiment, the installation holes 21 are formed so as to penetrate the temperature adjusting base 3 and the insulating plate 7 in the thickness direction, and the temperature sensor 20 is provided at the uppermost portion of these installation holes 21. is set up. Since the temperature sensor 20 is desirably installed at a position as close to the heater element 5 as possible, an installation hole 21 is formed so as to extend from the structure shown in FIG. And the heater element 5 may be brought closer to each other.

  The temperature sensor 20 is, for example, a fluorescent light-emitting type temperature sensor in which a phosphor layer is formed on the upper surface side of a rectangular parallelepiped light-transmitting member made of quartz glass or the like, and has a light-transmitting property and heat resistance. It is adhered to the lower surface of the heater element 5 by a silicone resin adhesive or the like.

  The phosphor layer is made of a material that generates fluorescence in response to heat input from the heater element 5. As the material for forming the phosphor layer, various kinds of fluorescent materials can be selected as long as they generate fluorescence in response to heat generation. Examples of the material for forming the phosphor layer include a phosphor material to which a rare earth element having an energy order suitable for light emission is added, a semiconductor material such as AlGaAs, a metal oxide such as magnesium oxide, and a mineral such as ruby and sapphire. It can be used by appropriately selecting from these materials.

  The temperature sensors 20 corresponding to the heater elements 5 are provided at arbitrary positions in the circumferential direction of the lower surface of the heater element 5 so as not to interfere with the power supply terminals and the like.

  The temperature measuring unit 22 that measures the temperature of the heater element 5 from the fluorescence of the temperature sensor 20 is, for example, an excitation light for the phosphor layer outside (below) the installation hole 21 of the temperature adjustment base 3. An excitation unit 23 for irradiating light, a fluorescence detector 24 for detecting the fluorescence emitted from the phosphor layer, and a control unit for controlling the excitation unit 23 and the fluorescence detector 24 and calculating the temperature of the main heater based on the fluorescence. 25.

  Further, the electrostatic chuck device 1 has a pin insertion hole 28 provided so as to penetrate from the temperature adjustment base 3 to the mounting plate 11 in the thickness direction thereof. A lift pin for detaching a plate-like sample is inserted into the pin insertion hole 28. A cylindrical insulator 29 is provided on an inner peripheral portion of the pin insertion hole 28.

Further, the electrostatic chuck device 1 has a gas hole (not shown) provided so as to penetrate from the temperature adjustment base portion 3 to the mounting plate 11 in the thickness direction thereof. The gas hole may have the same configuration as the pin insertion hole 28, for example. A cooling gas for cooling the plate-shaped sample W is supplied to the gas holes. The cooling gas is supplied to the groove 19 formed between the plurality of protrusions 11b on the upper surface of the mounting plate 11 through the gas holes, and cools the plate-like sample W.
The electrostatic chuck device 1 is configured as described above.

  Next, the present invention will be described in more detail with reference to examples.

(Thermal conductivity)
The thermal conductivity was calculated from the measurement result of the thermal diffusivity by the laser flash method and the measurement result of the specific heat by the DSC method.

(Thermal uniformity)
As a test body for evaluating the thermal uniformity, a sintered body having a diameter of 350 mm × 1 mm was prepared and used as a test body. Specifically, after a sintered body having a diameter of 350 mm and a thickness of more than 1 mm was produced, the surface was subjected to surface grinding to adjust the thickness to obtain a 1 mm thick sintered body (test body).

  The obtained test piece for heat uniformity evaluation was sandwiched between a first metal plate having a heater and having a diameter of 350 mm and a second metal plate having a diameter of 350 mm.

  The test piece was heated using the heating plate, and the temperature of the test piece was given a temperature gradient such that the temperature on the heating plate side was high and the temperature on the cooling plate side was low. Five minutes after the start of heating, it was considered that the heat flow of the test plate was in a steady state, and the temperatures of three places on the surface of the test piece on the cooling plate side were measured.

  The measurement position is the center of the specimen (coordinate position 0,0), -160 mm in the 270 ° direction (coordinate position -160,0) from the center of the specimen, and 160 mm (160,0) in the 90 ° direction from the center. ).

  If the difference between the maximum value and the minimum value of the measured temperature was within 5 ° C. at the three temperature measurement positions, it was evaluated that the heat uniformity was good. When the difference between the maximum value and the minimum value of the measured temperature exceeded 5 ° C., it was evaluated that the heat uniformity was poor. Table 1 shows the case of good and "x" for bad.

(Analysis of crystal phase)
The crystal phase was identified by an X-ray powder diffraction method using an X-ray diffractometer (manufactured by PANalital, model name X'Pert PRO MPD).
At this time, the intensity of the diffraction line of (110), which is a plane parallel to the c-axis of alumina, was defined as (I ₁₁₀ / I ₁₁₃ ) based on the diffraction line intensity of the (113) plane as an index of orientation.

(Measurement of crystal grain size)
In this example, the surface of the composite sintered body was mirror-polished with a 3 μm diamond paste, and then subjected to thermal etching at 1400 ° C. for 30 minutes in an argon atmosphere.
The structure of the surface of the obtained composite sintered body was observed at a magnification of 10,000 times using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, model number: S-4000).

  The electron micrograph was taken into image analysis type particle size distribution measurement software (Mac-View Version 4), and the length of the 200 or more crystal grains in the short axis direction and the length in the long axis direction were calculated. The arithmetic average of the length in the short axis direction and the length in the long axis direction of each of the obtained crystal grains was defined as “length in the short axis direction” or “length in the long axis direction”.

(Example 1)
Step of Obtaining a Mixture As starting materials, β-SiC type silicon carbide (β-SiC) particles having an average particle diameter of 30 μm and synthesized by thermal plasma CVD, and aluminum oxide (Al) having an average particle diameter of 0.15 μm ₂ O ₃ ) particles.

The β-SiC particles were weighed so as to be 8.5% by mass with respect to the total amount of the β-SiC particles and the Al ₂ O ₃ particles, and were weighed into distilled water containing a dispersant. The dispersion liquid containing the β-SiC particles and the Al ₂ O ₃ particles was subjected to a dispersion treatment by an ultrasonic dispersion device, and then pulverized and mixed using a two-stream particle collision type pulverization mixing device.

  For the obtained mixed solution, nitric acid was added to the slurry to adjust the pH of the slurry to 6.5.

The slurry whose pH was adjusted was spray-dried with a spray-drying device to obtain mixed particles of β-SiC and Al ₂ O ₃ .

-Sintering process In the following Examples and Comparative Examples, a hot forge without using a die was used. The mixed particles obtained in the mixing step were uniaxially press-formed at a press pressure of 8 MPa to obtain a formed body having a diameter of 320 mm × 15 mm. The temperature was raised to 500 ° C. without applying press pressure to remove water and dispersant (contaminants). Then, the compact from which impurities were removed was heated to 400 ° C. in the air to oxidize the surface of the β-SiC particles contained in the compact. The obtained molded body was sandwiched between graphite spacers having a diameter of 400 mm, and pressure sintering was performed without using a mold. In the pressure sintering, first, the compact was heated to 1200 ° C. in a vacuum atmosphere without applying a pressing pressure. Thereafter, sintering was performed at a pressure of 20 MPa and 1820 ° C. in an argon atmosphere to obtain a sintered body of Example 1.

  FIG. 2 is an SEM (Scanning Electron Microscope) image of the composite sintered body of Example 1, and is an image of a surface of the composite sintered body whose surface has been thermally etched after polishing of its cross section.

Regarding the composite sintered body of Example 1, the composition, the sintering temperature, the sintering method, the pressure in the sintering step, the length of the crystal grains in the short axis direction, the length in the long axis direction, the aspect ratio, I ₁₁₀ / I _113, the thermal conductivity and thermal uniformity evaluation are described in Table 1.

(Example 2)
In the firing step, a composite sintered body was manufactured in the same manner as in Example 1 except that the pressure was changed to 40 MPa.

Regarding the composite sintered body of Example 2, the composition, the sintering temperature, the sintering method, the pressure in the sintering step, the length of the crystal grains in the short axis direction, the length in the long axis direction, the aspect ratio, I ₁₁₀ / I _113, the thermal conductivity and thermal uniformity evaluation are described in Table 1.

(Example 3)
A composite sintered body was manufactured in the same manner as in Example 1 except that aluminum oxide was used as the metal oxide.

Regarding the composite sintered body of Example 3, the composition, the sintering temperature, the sintering method, the pressure in the sintering step, the length of the crystal grains in the short axis direction, the length in the long axis direction, the aspect ratio, I ₁₁₀ / I _113, the thermal conductivity and thermal uniformity evaluation are described in Table 1.

(Comparative Example 1)
In the firing step, a composite sintered body was manufactured in the same manner as in Example 1, except that the pressure was set to 40 MPa and the hot press method was changed.
Specific conditions are as follows.
The mixed particles obtained in the mixing step were uniaxially press-formed at a press pressure of 8 MPa to obtain a formed body having a diameter of 320 mm × 15 mm. The temperature was raised to 500 ° C. without applying press pressure to remove water and dispersant (contaminants). Then, the compact from which impurities were removed was heated to 400 ° C. in the air to oxidize the surface of the β-SiC particles contained in the compact.

  The obtained molded body was set in a graphite mold and subjected to pressure sintering. First, the molded body was heated to 1200 ° C. in a vacuum atmosphere without applying a pressing pressure. Thereafter, sintering was performed at a pressure of 40 MPa and 1820 ° C. in an argon atmosphere to obtain a sintered body of Comparative Example 1.

Regarding the composite sintered body of Comparative Example 1, the composition, the sintering temperature, the sintering method, the pressure in the sintering step, the length of the crystal grains in the short axis direction, the length in the long axis direction, the aspect ratio, I ₁₁₀ / I _113, the thermal conductivity and thermal uniformity evaluation are described in Table 1.

  FIG. 3 is an SEM (Scanning Electron Microscope, Scanning Electron Microscope) of the composite sintered body of Comparative Example 1, and is an image of a surface of the composite sintered body whose surface has been thermally etched after polishing of its cross section.

(Comparative Example 2)
In the firing step, a composite sintered body was manufactured in the same manner as in Example 1 except that the pressure was changed to 20 MPa.

Regarding the composite sintered body of Comparative Example 2, the composition, the sintering temperature, the sintering method, the pressure in the sintering step, the length of the crystal grains in the short axis direction, the length in the long axis direction, the aspect ratio, I ₁₁₀ / I _113, the thermal conductivity and thermal uniformity evaluation are described in Table 1.

As shown in the above Table 1, in Examples 1 to 3 to which the present invention was applied, the aspect ratio of the crystal grains was high and the crystal grains were flat. In Examples 1 to 3 using such a composite sintered body, the thermal conductivity in the in-plane direction was higher than the thermal conductivity in the inter-plane direction, and the heat uniformity was good.
On the other hand, Comparative Example 1 in which the present invention was not applied and the sintering step was performed by hot pressing, and Comparative Example 2 in which the sintering step was performed under a pressure of 20 MPa had small aspect ratios and were granular crystal grains. . In Comparative Examples 1 and 2 using such a composite sintered body, the thermal conductivity in the in-plane direction and the thermal conductivity in the inter-plane direction were almost the same, and the heat uniformity was not good.

  As shown in the results shown in FIG. 2, it was confirmed that the composite sintered body of Example 1 was flat crystal grains. On the other hand, as shown in the results shown in FIG. 3, the composite sintered body of Comparative Example 1 was granular crystal grains.

DESCRIPTION OF SYMBOLS 1 ... Electrostatic chuck apparatus, 11 ... Placement plate (substrate), 11a ... Placement surface, 12 ... Support plate (substrate), 13 ... Electrostatic adsorption electrode, W ... Plate sample

Claims (6)

A dielectric material comprising a composite sintered body having a metal oxide as a main phase,
In the composite sintered body, a plurality of crystal grains are oriented in substantially the same direction,
The length of the crystal grains in the short axis direction is 0.1 μm or more and 1.0 μm or less, the length in the long axis direction is 0.2 μm or more and 10 μm or less, and the aspect ratio (length in the long axis direction / short length). A length in the axial direction) of 2 or more.   The dielectric material according to claim 1, wherein the metal oxide is aluminum oxide.   The dielectric material according to claim 1, wherein the composite sintered body contains silicon carbide as a subphase. In the powder X-ray diffraction measurement using CuKα radiation of the composite sintered body, the intensity of a (110) diffraction peak existing at about 64.5 ° with respect to a (113) diffraction peak having a diffraction angle 2θ of about 68 °. The dielectric material according to any one of claims 1 to 3, wherein a ratio ( _I110 / _I113 ) is 0.5 or more. It is a manufacturing method of the dielectric material as described in any one of Claims 1-4, Comprising:
Obtaining a mixture containing a metal oxide that is a main phase;
A method for producing a dielectric material, comprising a sintering step of sintering the mixture under uniaxial pressure, wherein the sintering step is performed by a hot forge method and is performed under a pressing condition exceeding 20 MPa. A substrate, wherein the dielectric material according to any one of claims 1 to 4 is used as a forming material, and one main surface is a mounting surface on which the plate-like sample is mounted.
An electrostatic chuck device comprising: an electrostatic chucking electrode provided on the side of the base opposite to the mounting surface or inside the base.