JP2001319966A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck capable of stably maintaining attraction even if using it in a long period since an electrostatic electrode does not react on a carbon even when the carbon is included in a ceramic substrate and/or ceramic dielectric film. SOLUTION: In an electrostatic chuck in which an electrode is formed on a ceramic substrate, and a ceramic dielectric film is provided on the electrode, the electrostatic electrode is composed of a conductive ceramic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Detailed description of the invention]

[0002]

2. Description of the Related Art Semiconductors are extremely important products required in various industries.
The silicon wafer is manufactured by slicing a silicon single crystal to a predetermined thickness to produce a silicon wafer, and then forming a plurality of integrated circuits and the like on the silicon wafer.

In the manufacturing process of this semiconductor chip,
Various processes such as etching and CVD are performed on the silicon wafer placed on the electrostatic chuck to form a conductive circuit, an element, and the like. At this time, since corrosive gases are used as a deposition gas, an etching gas, and the like, it is necessary to protect the electrostatic electrode layer from corrosion by these gases. Therefore, the electrostatic electrode layer usually has a structure covered with a ceramic dielectric film or the like.

Usually, metals such as tungsten and molybdenum are used as electrostatic electrodes in such an electrostatic chuck because they are relatively resistant to oxidation and have sufficient conductivity.

[0005] Further, it is desired that the substrate constituting such an electrostatic chuck be black because it has a large amount of radiant heat and is excellent in heating characteristics and concealability of electrodes and the like. As an electrostatic chuck with black processing,
For example, JP-A-9-48668 discloses an electrostatic chuck using a carbon-containing aluminum nitride substrate having a molybdenum electrode formed therein as a substrate.

As another black treatment, for example, a method is known in which an appropriate metal element (blackening agent) is added to raw material powder of a ceramic substrate, and the resultant is fired to blacken the ceramic substrate. However, according to this method, the content of metal impurities contained in the ceramic substrate is increased, which causes a defect to the silicon wafer, and is not preferred.

[0007]

However, when such a metal electrode as described above is used as an electrostatic electrode on such a carbon-containing ceramic substrate, if the substrate is heated to a high temperature, the substrate may be left in the substrate. The existing carbon and the electrode react with each other, and the portion including the surface of the electrode is gradually carbonized and may be changed to a metal carbide.

As described above, when a part of the metal-made electrostatic electrode changes to metal carbide, the resistance value of the electrostatic electrode changes and the chucking force also changes, so that the silicon wafer or the like is stably adsorbed. There was a problem that it was not possible.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an electrostatic electrode includes a ceramic substrate and / or
Another object of the present invention is to provide an electrostatic chuck that does not react with carbon present in a ceramic dielectric film and can stably maintain the chucking force of the electrostatic chuck.

[0010]

According to the present invention, there is provided an electrode for electrostatic attraction on a ceramic substrate (hereinafter referred to as an electrostatic electrode).
Is formed, and a ceramic dielectric film is provided on the electrostatic electrode, wherein the electrostatic electrode is made of a conductive ceramic.

[0011] The electrostatic chuck of the present invention uses conductive ceramic for the electrostatic electrode. Therefore, even if carbon is contained in the ceramic substrate and / or the ceramic dielectric film, the electrostatic chuck can be used. Since the carbon and the electrostatic electrode do not react with each other, the resistance value of the electrostatic electrode does not change, and the chucking force of the electrostatic chuck can be stably maintained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An electrostatic chuck according to the present invention is an electrostatic chuck in which an electrostatic electrode is formed on a ceramic substrate and a ceramic dielectric film is provided on the electrostatic electrode.
The electrostatic electrode is made of a conductive ceramic.

FIG. 1 is a longitudinal sectional view schematically showing an embodiment of the electrostatic chuck of the present invention, and FIG. 2 is a sectional view taken along line AA of the electrostatic chuck shown in FIG. , FIG.
FIG. 3 is a sectional view taken along line BB of the electrostatic chuck shown in FIG. 1.

In the electrostatic chuck 101, a chuck positive electrode electrostatic layer 2 is formed on a surface of a ceramic substrate 1 having a circular shape in plan view.
And a chuck negative electrode electrostatic layer 3 are formed, and a ceramic dielectric film 4 is formed so as to cover the electrostatic electrode layer. A silicon wafer 9 is placed on the electrostatic chuck 101 and is grounded.

As shown in FIG. 2, the chuck positive electrode electrostatic layer 2 includes a semicircular arc portion 2a and a comb tooth portion 2b.
The chuck negative electrode electrostatic layer 3 also includes a semicircular portion 3a and a comb tooth portion 3b, and the chuck positive electrode electrostatic layer 2 and the chuck negative electrode electrostatic layer 3 intersect the comb tooth portions 2b and 3b. and so is disposed opposite manner, the chuck positive electrostatic layer 2 and the chuck negative electrostatic layer 3, and the + side of each DC power source - the side are connected, so that the DC voltage V ₂ is applied It has become.

On the other hand, a resistance heating element 5 having a concentric circular shape in plan view as shown in FIG. 3 is provided inside the ceramic substrate 1 for controlling the temperature of the silicon wafer 9. at both ends of the external terminal pin 6 is connected, is fixed, so that the voltages V ₁ is applied. Although not shown in FIGS. 1 and 2, this ceramic substrate 1 has a bottomed hole 11 for inserting a temperature measuring element and a through hole for inserting a lifter pin as shown in FIG. 12 are formed. Note that the resistance heating element 5 may be formed on the bottom surface of the ceramic substrate.

The lifter pins 16 can place the silicon wafer 9 thereon and move it up and down, thereby transferring the silicon wafer 9 to a carrier (not shown), The wafer 9 can be received and the silicon wafer 9 can be received.
Can be fixed by placing it on the ceramic dielectric film 4 on the ceramic substrate 1 and adsorbing it.

When the electrostatic chuck 101 is operated, a DC voltage V ₂ is applied to the chuck positive electrostatic layer 2 and the chuck negative electrostatic layer 3. As a result, the silicon wafer 9 is adsorbed and fixed to the chuck positive electrode electrostatic layer 2 and the chuck negative electrode electrostatic layer 3 via the ceramic dielectric film 4 by the electrostatic action (Coulomb force) of these electrodes. Will be done. After fixing the silicon wafer 9 on the electrostatic chuck 101 in this manner, the silicon wafer 9
Is subjected to various processes such as CVD.

In the electrostatic chuck of the present invention, the electrostatic electrodes formed on such a ceramic substrate are made of conductive ceramic. Examples of the conductive ceramic include at least one selected from carbides of tungsten and molybdenum. These conductive ceramics are more stable than metals, and are not carbonized by the carbon contained in the ceramic substrate and / or the ceramic dielectric film in the temperature range where the electrostatic chuck is used. This is because it has sufficient conductivity as an electrode.

Further, as described above, the ceramic dielectric film constituting the electrostatic chuck of the present invention is provided so as to cover the electrostatic electrodes formed on the ceramic substrate. It is preferable that the ceramic dielectric film and / or the ceramic substrate contain carbon. That is, at least one of the ceramic dielectric film and the ceramic substrate desirably contains carbon. This is for the following reasons.

First, regarding the ceramic dielectric film, when the ceramic dielectric film contains carbon, the amount of radiant heat increases, the heating characteristics of the silicon wafer are excellent, and the concealing properties of the electrostatic electrodes and the like are also excellent. It is. However, when a metal electrostatic electrode is formed under such a ceramic dielectric film, carbon in the dielectric film reacts with the electrostatic electrode. Therefore, it is necessary to use a conductive ceramic as the electrostatic electrode.

The high temperature of the ceramic dielectric film (about 5
When it is not desired to lower the thermal conductivity at around 00 ° C.), it is desirable to add crystalline carbon. When it is not desired to lower the volume resistivity at a high temperature, amorphous carbon is added. It is desirable. Therefore, in some cases, by adding both of them, both the volume resistivity and the thermal conductivity can be appropriately adjusted. Crystalline carbon can be determined by the size of the peak near 1550 cm ^-1 and near 1333 cm ^-1 when measured Raman spectrum.

When carbon is contained in the ceramic dielectric film, the content is preferably 100 to 5000 ppm. When the content of carbon is less than 100 ppm,
The electrostatic electrode and carbon in the dielectric film hardly react with each other, the radiation heat of the dielectric film is reduced, and it is difficult to hide the electrostatic electrode. On the other hand, when the content of carbon exceeds 5000 ppm, it is difficult to suppress densification and decrease in volume resistivity.

In order to make the carbon in the ceramic dielectric film amorphous, when a raw material powder, a resin or the like and a solvent are mixed to produce a molded body, the resin is hardly crystalline even when heated. Or a carbohydrate may be added, and the molded body may be degreased in an atmosphere containing less oxygen or a non-oxidizing atmosphere. Alternatively, amorphous carbon may be produced by heating a carbohydrate or resin which is likely to become amorphous by heating sucrose or the like, and then adding it. Further, when crystalline carbon is added, crystalline carbon black or graphite powder obtained by pulverizing graphite may be used.

By using an acrylic resin binder having a specific acid value, the amount of carbon and the crystallinity can be adjusted. This is because when the acid value of the acrylic resin binder changes, the ease of decomposition differs, and the amount and crystallinity remaining as carbon differ.

Next, regarding the ceramic substrate, when the above-mentioned ceramic substrate contains carbon, the amount of radiant heat increases and the concealing property of the electrostatic electrodes and the like is excellent. However, when a metal electrostatic electrode is formed on such a ceramic substrate, the carbon in the dielectric film reacts with the electrostatic electrode. Therefore, it is necessary to use a conductive ceramic as the electrostatic electrode. is there. Also in this case, the content of carbon is preferably about 100 to 5000 ppm. This is for the same reason as in the case of the ceramic dielectric film. As the carbon, as in the case of the ceramic dielectric film, one of crystalline and amorphous may be used, and both crystalline and amorphous may be used.

The electrostatic chuck according to the present invention has the above-described configuration, and an embodiment thereof includes, for example, those shown in FIGS. Hereinafter, each member constituting the electrostatic chuck, and
Other embodiments and the like of the electrostatic chuck according to the present invention will be sequentially described in detail.

The ceramic material constituting the ceramic dielectric film is not particularly limited, and examples thereof include a nitride ceramic, a carbide ceramic, and an oxide ceramic.

Examples of the nitride ceramic include metal nitride ceramics, for example, aluminum nitride, silicon nitride, boron nitride, titanium nitride and the like. Further, as the carbide ceramic, metal carbide ceramic,
For example, silicon carbide, zirconium carbide, titanium carbide,
Examples include tantalum carbide and tungsten carbide. Among these, silicon carbide and the like often use carbon as a sintering aid, so that reactivity with the electrode becomes a problem as in the present invention, and even in the case of aluminum nitride, carbon is used as a concealing agent and the like. Is often added, so that the reactivity with the electrode still becomes a problem.

Examples of the oxide ceramic include metal oxide ceramics such as alumina, zirconia, cordierite, and mullite. These ceramics may be used alone or in combination of two or more.

Among these ceramics, nitride ceramics and carbide ceramics are more preferable than oxide ceramics. This is because the thermal conductivity is high. Also, among nitride ceramics, aluminum nitride is most preferred. This is because the thermal conductivity is the highest at 180 W / m · K.

The thickness of the ceramic dielectric film is 50 to 50.
It is desirable to be 5000 μm. If the thickness of the ceramic dielectric film is less than 50 μm, a sufficient withstand voltage cannot be obtained because the film thickness is too small, and the dielectric breakdown of the ceramic dielectric film occurs when a silicon wafer is placed and adsorbed. In some cases, the thickness of the ceramic dielectric film is 50
If the thickness exceeds 00 μm, the distance between the silicon wafer and the electrostatic electrode becomes long, and the ability to adsorb the silicon wafer is reduced. The thickness of the ceramic dielectric film is more preferably 50 to 1500 μm.

The porosity of the ceramic dielectric film is preferably 5% or less, and the maximum pore diameter is preferably 50 μm or less. If the porosity exceeds 5%, the number of pores in the ceramic dielectric film increases, and the pore diameter becomes too large. As a result, the pores easily communicate with each other, and the ceramic dielectric having such a structure is used. This is because the withstand voltage of the film decreases. Further, when the pore diameter of the maximum pore exceeds 50 μm, the ratio of the pore diameter to the thickness of the ceramic dielectric film increases, and the proportion of the pores communicating with each other increases, so that the withstand voltage also decreases. Because. The porosity is more preferably 0 or 3% or less, and the pore diameter of the maximum pore is more preferably 0 or 10 μm or less.

The porosity and the maximum pore diameter are adjusted by the pressurization time, pressure, temperature, and additives such as SiC and BN during sintering. Since SiC and BN hinder sintering, pores can be introduced. For the measurement of the pore diameter of the maximum pore, five samples were prepared, the surface thereof was mirror-polished,
This is performed by photographing the surface at 10 places with an electron microscope at a magnification of 00 times. Then, the maximum pore diameter is selected from the photographed images, and the average of 50 shots is defined as the maximum pore diameter.

The porosity is measured by the Archimedes method. Pulverize the sintered body, put the pulverized material in an organic solvent or mercury, measure the volume, calculate the true specific gravity from the weight and volume of the pulverized material, and calculate the porosity from the true specific gravity and the apparent specific gravity . In addition, as described above, a certain amount of pores may be present in the ceramic dielectric film, because the presence of some open pores on the surface of the ceramic dielectric film makes it possible to perform dechucking smoothly. Because you can.

The ceramic dielectric film contains 0.1 to
Desirably, it contains 5% by weight of oxygen. 0.1
If the amount is less than 5% by weight, the withstand voltage cannot be ensured. On the other hand, if the amount exceeds 5% by weight, the withstand voltage will also decrease due to a decrease in the high temperature withstand voltage characteristics of the oxide. Also,
If the amount of oxygen exceeds 5% by weight, the thermal conductivity decreases and the temperature raising / lowering characteristics deteriorate.

In order to make the above-mentioned nitride ceramic contain oxygen, usually, the raw material powder of the nitride ceramic is heated in the air or oxygen, or the raw material powder is mixed with a metal oxide and fired.

Examples of the above metal oxides include yttria (Y ₂ O ₃ ), alumina (Al ₂ O ₃ ), rubidium oxide (Rb ₂ O), lithium oxide (Li ₂ O), and calcium carbonate (CaCO ₃ ). And the like. The addition amount of these metal oxides is preferably 1 to 20 parts by weight based on 100 parts by weight of the nitride ceramic.

The material of the ceramic substrate used in the electrostatic chuck of the present invention is, for example, nitride ceramic,
Examples thereof include carbide ceramics and oxide ceramics.
Examples of the nitride ceramic, the carbide ceramic, and the oxide ceramic include those described in the description of the ceramic dielectric film.

Of these ceramics, nitride ceramics and carbide ceramics are desirable. These are because they have high thermal conductivity and can satisfactorily transmit the heat generated by the resistance heating element. Further, it is desirable that the ceramic dielectric film and the ceramic substrate are made of the same material. In this case, the green sheets produced by the same method are laminated,
This is because by firing under the same conditions, it can be easily manufactured. Also, among nitride ceramics, aluminum nitride is most preferred. Thermal conductivity 180W
/ M · K, which is the highest.

FIGS. 8 and 9 are horizontal sectional views schematically showing electrostatic electrodes of another electrostatic chuck.
In the electrostatic chuck 20 shown in FIG. 9, a semicircular chuck positive electrode electrostatic layer 22 and a chuck negative electrode electrostatic layer 23 are formed inside the ceramic substrate 1. In the electrostatic chuck shown in FIG. Are formed with chuck positive electrode electrostatic layers 32a and 32b and chuck negative electrode electrostatic layers 33a and 33b each having a shape obtained by dividing a circle into four parts. Further, the two positive electrode electrostatic layers 22a and 22b and the two chuck negative electrode electrostatic layers 33a and 33b are formed to cross each other. In the case of forming an electrode in which a circular electrode or the like is divided, the number of divisions is not particularly limited, and may be five or more, and the shape is not limited to a sector. Note that an RF electrode may be provided below the electrostatic electrode.

The electrostatic electrodes shown in FIGS. 8 and 9 are also made of conductive ceramic, like the electrostatic electrode 2 of the electrostatic chuck 101 (see FIGS. 1 and 2). Or, it is not carbonized by carbon contained in the ceramic dielectric film.

The electrostatic chuck of the present invention is usually provided with a temperature control means such as a resistance heating element as shown in FIG. This is because it is necessary to perform a CVD process or the like while heating the silicon wafer placed on the electrostatic chuck.

As the temperature control means, in addition to the resistance heating element 5 shown in FIG. 3, a Peltier element (see FIG. 6) can be mentioned. The resistance heating element may be provided inside the ceramic substrate, or may be provided on the bottom surface of the ceramic substrate. When a resistance heating element is provided, a blowing port for a coolant such as air may be provided as a cooling means in a support container into which the electrostatic chuck is fitted.

When the resistance heating element is provided inside the ceramic substrate, a plurality of layers may be provided. In this case, it is desirable that the patterns of the respective layers are formed so as to complement each other, and that the pattern is formed on any layer when viewed from the heating surface. For example, the structure is a staggered arrangement.

Examples of the resistance heating element include a sintered body of metal or conductive ceramic, a metal foil, a metal wire and the like. As the metal sintered body, at least one selected from tungsten and molybdenum is preferable. This is because these metals are relatively hard to oxidize and have a resistance value sufficient to generate heat.

The conductive ceramic may be at least one selected from carbides of tungsten and molybdenum.
Seeds can be used. Further, when a resistance heating element is formed on the bottom surface of the ceramic substrate, it is desirable to use a noble metal (gold, silver, palladium, platinum) or nickel as the metal sintered body. Specifically, silver, silver-palladium, or the like can be used. The metal particles used in the metal sintered body may be spherical, flaky, or a mixture of spherical and flaky.

A metal oxide may be added to the metal sintered body. The use of the metal oxide is for bringing the ceramic substrate and the metal particles into close contact. Although the reason why the metal oxide improves the adhesion between the ceramic substrate and the metal particles is not clear, the surface of the metal particles has a slight oxide film formed thereon, and the ceramic substrate is formed of an oxide. Of course, even in the case of a non-oxide ceramic, an oxide film is formed on the surface. Therefore, it is considered that this oxide film is sintered and integrated on the surface of the ceramic substrate via the metal oxide, so that the metal particles and the ceramic substrate adhere to each other.

As the metal oxide, for example, oxidized
Lead, zinc oxide, silica, boron oxide (B _Two O_Three ), Al
At least one selected from Mina, Yttria and Titania
Species are preferred. These oxides have the resistance value of the resistance heating element.
Between the metal particles and the ceramic substrate without increasing the
This is because adhesion can be improved.

It is desirable that the amount of the metal oxide is 0.1 to less than 10 parts by weight based on 100 parts by weight of the metal particles. By using a metal oxide in this range,
This is because the resistance value does not become too large and the adhesion between the metal particles and the ceramic substrate can be improved.

The ratio of lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania is such that when the total amount of metal oxide is 100 parts by weight, 10 parts by weight, 1 to 30 parts by weight of silica, 5 to 50 parts by weight of boron oxide, 20 to 7 parts of zinc oxide
0 parts by weight, alumina 1 to 10 parts by weight, yttria 1
-50 parts by weight and titania of 1-50 parts by weight are preferred.
However, it is desirable that the total be adjusted so that the total does not exceed 100 parts by weight. This is because these ranges can particularly improve the adhesion to the ceramic substrate.

When the resistance heating element is provided on the bottom surface of the ceramic substrate, it is desirable that the surface of the resistance heating element 15 be covered with a metal layer 150 (see FIG. 4). The resistance heating element 15 is a sintered body of metal particles, and is easily oxidized when exposed, and the oxidation changes the resistance value. Therefore, by covering the surface with the metal layer 150, oxidation can be prevented.

The thickness of the metal layer 150 is 0.1 to 10 μm
Is desirable. This is because the oxidation of the resistance heating element can be prevented without changing the resistance value of the resistance heating element. The metal used for coating may be a non-oxidizing metal. Specifically, gold, silver, palladium, platinum,
At least one selected from nickel is preferred.
Among them, nickel is more preferable. The resistance heating element requires a terminal for connection to a power supply, and this terminal is attached to the resistance heating element via solder. Nickel prevents thermal diffusion of the solder. As connection terminals, terminal pins made of Kovar can be used.

When the resistance heating element is formed inside the heater plate, the surface of the resistance heating element is not oxidized, so that the coating is unnecessary. When the resistance heating element is formed inside the heater plate, a part of the surface of the resistance heating element may be exposed.

As the metal foil to be used as the resistance heating element, it is desirable to use a nickel foil or a stainless steel foil as a resistance heating element by forming a pattern by etching or the like. The patterned metal foil may be bonded with a resin film or the like. Examples of the metal wire include a tungsten wire and a molybdenum wire.

When a Peltier element is used as the temperature control means, heat is generated by changing the direction of current flow.
This is advantageous because both cooling can be performed. As shown in FIG. 6, the Peltier element 8 is composed of p-type and n-type thermoelectric elements 81.
Are connected in series and joined to a ceramic plate 82 or the like. Examples of the Peltier element include a silicon-germanium-based material, a bismuth-antimony-based material, and a lead / tellurium-based material.

In the electrostatic chuck according to the present invention, for example, as shown in FIG. 1, a chuck positive electrostatic layer 2 and a chuck negative electrostatic layer 3 are provided between a ceramic substrate 1 and a ceramic dielectric film 4. And an electrostatic chuck 10 having a resistance heating element 5 provided inside the ceramic substrate 1.
1. As shown in FIG. 4, a chuck positive electrode electrostatic layer 2 and a chuck negative electrode electrostatic layer 3 are provided between a ceramic substrate 1 and a ceramic dielectric film 4, and a resistance heating element 15 is provided on the bottom surface of the ceramic substrate 1. An electrostatic chuck 201 having a configuration provided with
As shown in FIG. 5, a chuck positive electrode electrostatic layer 2 and a chuck negative electrode electrostatic layer 3 are provided between a ceramic substrate 1 and a ceramic dielectric film 4, and a metal as a resistance heating element is provided inside the ceramic substrate 1. Electrostatic chuck 3 in which wire 7 is embedded
01, as shown in FIG. 6, a chuck positive electrostatic layer 2 and a chuck negative electrostatic layer 3 are provided between a ceramic substrate 1 and a ceramic dielectric film 4, and a thermoelectric element 81 is provided on the bottom surface of the ceramic substrate 1. An example is an electrostatic chuck 401 having a configuration in which the Peltier element 8 made of the ceramic plate 82 is formed.

In the present invention, as shown in FIGS. 1 to 6, the chuck positive electrostatic layer 2 and the chuck negative electrostatic layer 3 are provided between the ceramic substrate 1 and the ceramic dielectric film 4.
Since the resistance heating elements 5 and the metal wires 7 are formed inside the ceramic substrate 1, connection portions (through holes) 16 and 17 for connecting these to external terminals are required. The through holes 16 and 17 are formed by filling a high melting point metal such as a tungsten paste or a molybdenum paste, or a conductive ceramic such as tungsten carbide or molybdenum carbide.

Further, the connecting portions (through holes) 16 and 17
Is preferably 0.1 to 10 mm. This is because cracks and distortion can be prevented while preventing disconnection. The external terminal pins 6 and 18 are connected using the through holes as connection pads (see FIG. 7D).

The connection is made by solder or brazing material. As brazing materials, silver brazing, palladium brazing, aluminum brazing,
Use gold brazing. As the gold solder, an Au-Ni alloy is desirable. This is because the Au-Ni alloy has excellent adhesion to tungsten.

The ratio of Au / Ni is [81.5-82.
5 (% by weight)] / [18.5 to 17.5 (% by weight)] is desirable. The thickness of the Au—Ni layer is desirably 0.1 to 50 μm. This is because the range is sufficient to secure the connection.
Moreover, 500-1000 at a high vacuum of 10 ^-6 to 10 ^-5 Pa.
When used at high temperature of ℃, Au-Cu alloy deteriorates,
An Au-Ni alloy is advantageous without such deterioration.
The total amount of impurity elements in the Au—Ni alloy is 100%.
It is desirable that the amount be less than 1 part by weight when it is used as a part by weight.

In the present invention, a thermocouple can be embedded in the bottomed hole of the ceramic substrate 1 as necessary.
This is because the temperature of the resistance heating element can be measured using a thermocouple, and the temperature and the amount of current can be changed based on the data to control the temperature. The size of the junction of the metal wires of the thermocouple is preferably equal to or larger than the element diameter of each metal wire and 0.5 mm or less. With such a configuration, the heat capacity of the junction is reduced, and the temperature is accurately and quickly converted to a current value. For this reason, the temperature controllability is improved and the temperature distribution on the heated surface of the wafer is reduced. Examples of the thermocouple include J
As listed in IS-C-1602 (1980),
K-type, R-type, B-type, S-type, E-type, J-type, and T-type thermocouples are exemplified.

FIG. 10 is a sectional view schematically showing a supporting container 41 for disposing the electrostatic chuck 101 of the present invention having the above-described structure. The electrostatic chuck 101 is fitted into the support container 41 via a heat insulating material 45. The support container 41 has a refrigerant outlet 42 formed therein. The refrigerant is blown from the refrigerant inlet 44 and passes through the refrigerant outlet 42 to the outside through the suction port 43. The operation of the coolant can cool the electrostatic chuck 101.

Next, an example of the method of manufacturing the electrostatic chuck according to the present invention will be described with reference to the sectional view shown in FIG. (1) First, a slurry is prepared by mixing a ceramic powder such as an oxide ceramic, a nitride ceramic, and a carbide ceramic with a binder and a solvent, and then the green sheet 50 is manufactured by using this slurry by a doctor blade method. . As the ceramic powder described above, for example,
Aluminum nitride, silicon carbide, or the like can be used, and a sintering aid such as yttria may be added as necessary.

It is to be noted that several or one green sheet 50 laminated on the green sheet 50 on which the later-described electrostatic electrode layer printed body 51 is formed is a layer to be the ceramic dielectric film 4. Usually, it is desirable to use the same material for the ceramic dielectric film 4 and the material for the ceramic substrate 1. This is because these are often sintered together, and the firing conditions are the same. However, when the materials are different, it is also possible to manufacture a ceramic substrate first, form an electrostatic electrode layer thereon, and further form a ceramic dielectric film thereon.

Examples of the binder usually used include an acrylic binder, ethyl cellulose, butyl cellosolve,
Examples thereof include polyvinyl alcohol, and at least one selected from these can be used as a binder for forming a ceramic substrate.

Normally, carbon can be contained in a ceramic substrate to be produced by using an acrylic binder. In addition, by using one having a different acid value, it is possible to change the residual amount of carbon in the ceramic substrate or change the crystallinity of carbon to some extent. Further, graphite powder or carbon black may be added to the slurry.

Further, the solvent is preferably at least one selected from α-terpineol and glycol.

The green sheet 50 may be provided with a through hole for inserting a lifter pin of a silicon wafer or a concave portion for burying a thermocouple as required. The through holes and the concave portions can be formed by punching or the like. The thickness of the green sheet 50 is preferably about 0.1 to 5 mm.

Next, a conductor paste serving as an electrostatic electrode layer and a resistance heating element is printed on the green sheet 50. The printing is performed so as to obtain a desired aspect ratio in consideration of the shrinkage ratio of the green sheet 50, thereby obtaining the electrostatic electrode layer print body 51 and the resistance heating element layer print body 52. The electrostatic electrode layer printed body 51 is formed by printing a conductive paste containing conductive ceramic particles, and the resistance heating element layer printed body 52 is formed by printing a conductive paste containing conductive ceramic particles, metal particles, and the like.

As the conductive ceramic particles contained in these conductor pastes, carbides of tungsten or molybdenum are most suitable. This is because it is difficult to be oxidized, the thermal conductivity is hardly lowered, and furthermore, it does not react with carbon contained in the ceramic substrate. Further, as the metal particles, for example, tungsten, molybdenum, platinum,
Nickel or the like can be used.

The average particle size of the conductive ceramic particles and metal particles is preferably 0.1 to 5 μm. This is because it is difficult for these particles to print the conductor paste even if they are too large or too small.

As such a paste, 85 to 97 parts by weight of conductive ceramic particles or metal particles, 1.5 to 10 parts by weight of at least one kind of binder selected from acrylic, ethyl cellulose, butyl cellosolve and polyvinyl alcohol, α- A conductor paste prepared by mixing 1.5 to 10 parts by weight of at least one solvent selected from terpineol, glycol, ethyl alcohol and butanol is most suitable. Further, the holes formed by punching or the like are filled with a conductive paste to obtain through-hole prints 53 and 54.

Next, as shown in FIG.
A green sheet 50 having 1, 52, 53, 54;
The green sheet 50 having no printed body is laminated. On the green sheet on which the electrostatic electrode layer printed body 51 is formed, several or one green sheets 5 having the above-described configuration are provided.
0 is laminated. The reason why the green sheet 50 having no printed body is laminated on the side where the resistance heating element is formed is to prevent the end face of the through hole from being exposed and being oxidized during firing for forming the resistance heating element. . If baking for forming the resistance heating element is performed while the end face of the through hole is exposed, it is necessary to sputter a metal that is difficult to oxidize, such as nickel, and more preferably to coat it with Au-Ni gold solder. Is also good.

(2) Next, as shown in FIG. 7B, the laminate is heated and pressed to sinter the green sheet and the conductive paste. Heating temperature is 1000-20
The temperature and the pressure are preferably from 10 to 20 MPa at 00 ° C., and the heating and pressurization are performed in an inert gas atmosphere. As the inert gas, argon, nitrogen, or the like can be used. In this step, the through holes 16 and 17, the chuck positive electrode electrostatic layer 2, the chuck negative electrode electrostatic layer 3, the resistance heating element 5, and the like are formed.

(3) Next, as shown in FIG. 7C, blind holes 13 and 14 for connecting external terminals are provided. Blind hole 1
At least a part of the inner walls of the electrodes 3 and 14 are made conductive, and the conductive inner walls are connected to the chuck positive electrostatic layer 2, the chuck negative electrostatic layer 3, the resistance heating element 5, and the like. desirable.

(4) Finally, as shown in FIG.
External terminals 6 and 18 are provided in blind holes 13 and 14 via a brazing filler metal. Further, if necessary, bottomed holes 11 (see FIG. 3)
And a thermocouple can be embedded therein. As the solder, alloys such as silver-lead, lead-tin, and bismuth-tin can be used. The thickness of the solder layer is 0.1 to
50 μm is desirable. This is because the range is sufficient to secure the connection by soldering.

In the above description, the electrostatic chuck 101
(See FIG. 1), the electrostatic chuck 201 (see FIG.
In the case of manufacturing, a ceramic plate having an electrostatic electrode layer is manufactured, and then a conductive paste is printed and fired on the bottom surface of the ceramic plate to form a resistance heating element 15, and thereafter, electroless plating or the like is performed. May be used to form the metal layer 150. When the electrostatic chuck 301 (see FIG. 5) is manufactured, a conductive ceramic foil or a metal wire may be embedded in ceramic powder as an electrostatic electrode or a resistance heating element and sintered. Further, when manufacturing the electrostatic chuck 401 (see FIG. 6), after manufacturing a ceramic substrate having an electrostatic electrode layer, a Peltier element may be joined to the ceramic substrate via a sprayed metal layer.

[0079]

The present invention will be described in more detail below. (Example 1) Manufacture of electrostatic chuck (see FIG. 1) (1) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama, average particle size 1.1 μm), yttria (average particle size:
0.4 μm) 4 parts by weight, 8 parts by weight of an acrylic resin binder (KC-600 manufactured by Kyoeisha Co., Ltd., acid value 10 KOHmg / g), 0.5 part by weight of a dispersant, and 53 parts by weight of alcohol composed of 1-butanol and ethanol Using the paste that has been molded by the doctor blade method,
A green sheet having a thickness of 0.47 mm was obtained.

(2) Next, the green sheet is heated to 80 ° C.
After drying for 5 hours, a portion serving as a through hole for inserting a lifter pin by punching, a portion serving as a through hole for connecting to an external terminal, and the like were provided.

(3) 100 parts by weight of tungsten carbide particles having an average particle diameter of 1 μm, acrylic binder 3.0
By weight, 3.5 parts by weight of the α-terpineol solvent and 0.3 parts by weight of the dispersant were mixed to prepare a conductor paste A. A conductive paste B was prepared by mixing 100 parts by weight of tungsten particles having an average particle diameter of 3 μm, 1.9 parts by weight of an acrylic binder, 3.7 parts by weight of an α-terpineol solvent, and 0.2 parts by weight of a dispersant.

The conductor paste A was printed on a green sheet by screen printing to form a conductor paste layer. The printing pattern was a concentric pattern. Further, a conductor paste layer composed of an electrostatic electrode pattern having the shape shown in FIG. 2 was formed on another green sheet. In addition, a conductive paste B
Was charged.

On the green sheet 50 on which the concentric pattern is printed, 34 green sheets 50 on which the conductor paste A is not printed are printed on the upper side (heating surface) and 13 on the lower side.
And a green sheet 50 on which a conductive paste layer made of an electrostatic electrode pattern is printed, and two green sheets 50 on which no conductive paste A is printed are further stacked thereon. The laminate was formed by pressure bonding at 8 ° C. and a pressure of 8 MPa (FIG. 7A).

(4) Next, the obtained laminate was heated at 350 ° C. for 4 hours in nitrogen gas, and at 1890 ° C. under a pressure of 15 M
Hot pressing was performed at Pa for 3 hours to obtain an aluminum nitride plate having a thickness of 3 mm. This was cut out into a 230 mm disk shape, and a plate-shaped body made of aluminum nitride having therein a resistance heating element 5 having a thickness of 6 μm and a width of 10 mm, and a chuck positive electrostatic layer 2 and a chuck negative electrostatic layer 3 having a thickness of 10 μm. (FIG. 7B).

At this time, the amount of carbon contained in the plate was measured by the following method.
m. Further, when the laser Raman spectrum was measured, it was carbon with reduced crystallinity in which peaks were observed at around 1580 cm ^{-1 and} around 1355 cm ^-1 .

(5) Next, the plate obtained in (4) is
After polishing with a diamond grindstone, a mask is placed and Si
A bottomed hole (diameter: 1.2 mm, depth: 2.0 mm) for a thermocouple was provided on the surface by blasting treatment with C or the like.

(6) Further, the portions where the through holes are formed are cut out to form blind holes 13 and 14 (FIG. 7).
(C)) External holes 6 and 18 made of Kovar were connected to the blind holes 13 and 14 by heating and reflowing at 700 ° C. using gold solder made of Ni—Au (FIG. 7D).

(7) Next, a plurality of thermocouples for temperature control were embedded in the bottomed holes, and the manufacture of the electrostatic chuck having the resistance heating element was completed. The chucking force of the electrostatic chuck having the resistance heating element thus manufactured was measured by the following method. The results are shown in Table 1 below.

Example 2 Production of Electrostatic Chuck (See FIG. 4) (1) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama, average particle size 1.1 μm), yttria (average particle size:
0.4 μm) 4 parts by weight, 8 parts by weight of an acrylic resin binder (KC-600 manufactured by Kyoeisha Co., Ltd., acid value 17 KOHmg / g), 0.5 part by weight of a dispersant, and 53 parts by weight of alcohol composed of 1-butanol and ethanol Using the paste thus obtained, a green sheet having a thickness of 0.47 mm was obtained by a doctor blade method.

(2) Next, the green sheet is heated to 80 ° C.
After drying for 5 hours, a portion serving as a through hole for inserting a lifter pin by punching, a portion serving as a through hole for connecting to an external terminal, and the like were provided.

(3) 100 parts by weight of tungsten carbide particles having an average particle diameter of 1 μm, acrylic binder 3.0
By weight, 3.5 parts by weight of the α-terpineol solvent and 0.3 parts by weight of the dispersant were mixed to prepare a conductor paste A. A conductive paste B was prepared by mixing 100 parts by weight of tungsten particles having an average particle diameter of 3 μm, 1.9 parts by weight of an acrylic resin binder, 3.7 parts by weight of an α-terpineol solvent, and 0.2 parts by weight of a dispersant. This conductor paste A was printed on a green sheet by screen printing to form a conductor paste layer composed of an electrostatic electrode pattern having the shape shown in FIG.

Further, a conductive paste B was filled in a through hole for a through hole for connecting an external terminal. On the green sheet 50 on which the electrostatic electrode pattern is printed, one green sheet 50 on which the conductive paste A is not printed is laminated on the upper side (heating surface) and 48 on the lower side, and these are laminated at 130 ° C. and a pressure of 8 MPa. To form a laminate.

(4) Next, the obtained laminate was heated in a nitrogen gas at 600 ° C. for 1 hour, at 1890 ° C. and a pressure of 15M.
Hot pressing was performed at Pa for 3 hours to obtain an aluminum nitride plate having a thickness of 3 mm. This is cut out into a 230 mm disk shape, and a 10 μm thick chuck positive electrode electrostatic layer 32 is formed inside.
a, b and a plate made of aluminum nitride having chuck negative electrode electrostatic layers 33a, b.

At this time, the amount of carbon contained in the plate was measured by the following method.
m. Further, when the laser Raman spectrum was measured, it was carbon with reduced crystallinity in which peaks were observed at around 1580 cm ^{-1 and} around 1355 cm ^-1 .

(5) A mask was placed on the bottom surface of the plate obtained in the above (4), and a concave portion (not shown) for a thermocouple was provided on the surface by blasting with SiC or the like. (6) Next, the resistance heating element 15 was printed on the surface (bottom surface) facing the wafer mounting surface. For printing, a conductor paste was used.
The conductive paste is Solvest PS60 manufactured by Tokuri Chemical Laboratory, which is used to form through holes in printed wiring boards.
3D was used. This conductor paste is a silver / lead paste, and a metal oxide composed of lead oxide, zinc oxide, silica, boron oxide, and alumina (the weight ratio of each is 5 /
55/10/25/5) per 100 parts by weight of silver.
It contained 5 parts by weight. The silver had a scaly shape with an average particle size of 4.5 μm.

(7) The plate on which the conductor paste was printed was heated and baked at 780 ° C. to sinter silver and lead in the conductor paste and baked the ceramic paste on a ceramic substrate to obtain a resistance heating element 15. Further, the plate is immersed in an electroless nickel plating bath composed of an aqueous solution containing 30 g / l of nickel sulfate, 30 g / l of boric acid, 30 g / l of ammonium chloride and 60 g / l of Rochelle salt, and the surface of the resistance heating element 15 is thickened. A metal layer 150 made of nickel having a thickness of 1 μm and a boron content of 1% by weight or less was deposited. Thereafter, the plate was subjected to annealing at 120 ° C. for 3 hours. The resistance heating element 15 made of a silver sintered body had a thickness of 5 μm, a width of 2.4 mm, and an area resistivity of 7.7 mΩ / □.

(8) Next, blind holes for exposing the through holes 16 were formed in the ceramic substrate. N
Using a gold solder made of an i-Au alloy (81.5% by weight of Au, 18.4% by weight of Ni, 0.1% by weight of impurities),
After heating and reflow at 0 ° C., external terminal pins made of Kovar were connected. Also, external terminal pins made of Kovar were formed on the resistance heating element via solder (tin 9 / lead 1).

(9) Next, a plurality of thermocouples for temperature control were buried in the concave portions to obtain the electrostatic chuck 201. The chucking force of the electrostatic chuck having the resistance heating element thus manufactured was measured by the following method. The results are shown in Table 1 below.

(Embodiment 3) Electrostatic chuck 301 (FIG. 5)
(1) Two electrodes having the shape shown in FIG. 8 were formed by punching a tungsten carbide foil having a thickness of 10 μm. An aluminum nitride powder (manufactured by Tokuyama Corporation, average particle size 1.1 μm) was formed using the two electrodes and the tungsten wire.
100 parts by weight, 4 parts by weight of yttria (average particle size: 0.4 μm), acrylic resin binder (KC-60 manufactured by Kyoeisha Co., Ltd.)
0 acid value 17KOHmg / g) 8 parts by weight together, put in a mold and heated in nitrogen gas at 350 ° C. for 4 hours,
Hot pressed at 1890 ° C, pressure 15MPa for 3 hours,
An aluminum nitride plate having a thickness of 3 mm was obtained. This was cut into a circular shape having a diameter of 230 mm to obtain a plate-like body. At this time, the thickness of the electrostatic electrode layer was 10 μm. At this time, when the amount of carbon contained in the plate was measured by the following method, the amount of carbon was 805 ppm.

(2) The steps (5) to (7) of Example 1 were performed on the plate-like body to obtain an electrostatic chuck 301. The chucking force of the electrostatic chuck having the resistance heating element thus manufactured was measured by the following method. The results are shown in Table 1 below.

(Embodiment 4) Electrostatic chuck 401 (FIG. 6)
Production of Acrylic Resin Binder (KC-600, manufactured by Kyoeisha Co., Ltd., acid value 17 KOHmg / g) 8 parts by weight, and after performing the steps (1) to (5) of Example 2, nickel was further sprayed on the bottom surface. Thereafter, a lead / tellurium-based Peltier element was joined to obtain an electrostatic chuck 401. At this time, when the amount of carbon contained in the plate was measured by the following method, the amount of carbon was 800 ppm.
Met. The chucking force of the electrostatic chuck having the resistance heating element thus manufactured was measured by the following method. The results are shown in Table 1 below.

Comparative Example 1 A conductive paste made of tungsten was used for the electrostatic electrode and the resistance heating element, except that
An electrostatic chuck was manufactured in the same manner as in Example 1. The chucking force and the carbon content of the electrostatic chuck having the resistance heating element thus manufactured were measured by the following methods. The results are shown in Table 1 below.

Comparative Example 2 A conductive paste made of tungsten was used for an electrostatic electrode and a resistance heating element, except that
An electrostatic chuck was manufactured in the same manner as in Example 2. The chucking force and the carbon content of the electrostatic chuck having the resistance heating element thus manufactured were measured by the following methods. The results are shown in Table 1 below.

Comparative Example 3 An electrostatic chuck was manufactured in the same manner as in Example 3 except that a tungsten foil was used for the electrostatic electrode and the resistance heating element. The chucking force and the carbon content of the electrostatic chuck having the resistance heating element thus manufactured were measured by the following methods. The results are shown in Table 1 below.

Comparative Example 4 A conductive paste made of tungsten was used for an electrostatic electrode and a resistance heating element, except that
An electrostatic chuck was manufactured in the same manner as in Example 4. The chucking force and the carbon content of the electrostatic chuck having the resistance heating element thus manufactured were measured by the following methods. The results are shown in Table 1 below.

[0106]Evaluation method  (1) Measurement of chuck force First, the temperature was raised to 400 ° C, and a load cell (Shimadzu Corporation)
Using an Autograph AGS-50A manufactured by
The locking force was measured. Next, energize each electrostatic chuck.
Cut and let the ceramic substrate cool down to room temperature.
Repeat the process of raising the temperature to 00 ° C 1000 times
After performing the cycle test, use the load cell again
Measure the chucking force of the electrostatic chuck and determine the initial chucking force.
And the rate of change of chuck force after heat cycle. So
Are shown in Table 1 below.

(2) Measurement of Carbon Content of Ceramic Substrate After crushing the sintered body, the sintered body is heated at 500 to 800 ° C. to collect generated CO _x gas and measure the capacity. Was.

[0108]

[Table 1]

As apparent from Table 1 above, Examples 1 to
In the electrostatic chuck according to Comparative Example 4, the change rate of the chucking force before the heat cycle test and the change rate of the chucking force after the test were 4-5%, which was not much changed. In the case of the electric chuck, the change rate of the chuck force before the heat cycle test and the change rate of the chuck force after the test were as large as 15 to 20%.

[0110]

As described above, in the electrostatic chuck of the present invention, since the above-mentioned electrostatic electrodes are made of conductive ceramic, carbon is contained in the ceramic substrate and / or the ceramic dielectric film. However, the electrostatic electrode does not react with the carbon, and the chucking force of the electrostatic chuck can be stably maintained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of the electrostatic chuck of the present invention.

FIG. 2 is a sectional view taken along line AA of the electrostatic chuck shown in FIG.

FIG. 3 is a sectional view taken along line BB of the electrostatic chuck shown in FIG. 1;

FIG. 4 is a cross-sectional view schematically showing one example of the electrostatic chuck of the present invention.

FIG. 5 is a cross-sectional view schematically showing one example of the electrostatic chuck of the present invention.

FIG. 6 is a cross-sectional view schematically showing one example of the electrostatic chuck of the present invention.

FIGS. 7A to 7D are cross-sectional views schematically showing a part of the manufacturing process of the electrostatic chuck of the present invention.

FIG. 8 is a horizontal sectional view schematically showing the shape of another electrostatic electrode constituting the electrostatic chuck of the present invention.

FIG. 9 is a horizontal sectional view schematically showing the shape of still another electrostatic electrode constituting the electrostatic chuck of the present invention.

FIG. 10 is a cross-sectional view schematically showing a state where the electrostatic chuck of the present invention is fitted in a support container.

[Description of Signs] 101, 201, 301, 401 Electrostatic chuck 1 Ceramic substrate 2, 22, 32a, 32b Chuck positive electrode electrostatic layer 3, 23, 33a, 33b Chuck negative electrode electrostatic layer 2a, 3a Semicircular portion 2b 3b comb tooth part 4 ceramic dielectric film 5 resistance heating element 6, 18 external terminal pin 7 metal wire 8 Peltier element 9 silicon wafer 11 bottomed hole 12 through hole 13, 14 blind hole 15 resistance heating element 150 metal layer 16, 17 Through-hole 41 Support container 42 Refrigerant outlet 43 Inlet 44 Refrigerant inlet 45 Insulation material

Continued on the front page F term (reference) 3C016 GA10 5F004 BB22 BB26 5F031 CA02 HA02 HA17 HA18 HA33 HA37 HA38 JA01 JA46 MA28 5F045 AF03 EK09 EM05 EM09 EM10

Claims (1)

[Claims] 1. An electrostatic chuck in which an electrode is formed on a ceramic substrate and a ceramic dielectric film is provided on the electrode, wherein the electrode is made of conductive ceramic. .