JP2001351970A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck, capable of assuring insulation between resistance heating elements, even at a high temperature and preventing occurrence of a short circuit between electrostatic electrodes via the resistance heating element. SOLUTION: In the electrostatic chuck comprising a resistance heating element provided on a ceramic board, electrostatic electrodes formed on the board and a ceramic dielectric film provided integrally on the electrodes, the element is provided on a side face opposite to the surface of the board, having the ceramic dielectric film provided on the board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck mainly used in the semiconductor industry, and more particularly to an electrostatic chuck having a resistance heating element and having excellent temperature uniformity during heating.

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,
A semiconductor wafer such as a silicon wafer is placed on an apparatus capable of performing various processes, and subjected to various processes such as etching and CVD to form a conductor circuit, an element, and the like.

At this time, the semiconductor wafer needs to be firmly fixed to the device. For this reason, an electrostatic chuck provided with an electrostatic electrode for adsorbing and fixing a semiconductor wafer inside the apparatus is widely used.

Also, oxide ceramics such as alumina, nitride ceramics, and the like are used as materials for forming the electrostatic chuck. In the electrostatic chuck using such a ceramic, an electrostatic electrode is provided on a ceramic substrate, a thin dielectric film is formed on the electrostatic electrode, and a semiconductor wafer is coulombed through the dielectric film. The force is applied to the ceramic substrate.

Further, when performing thermal CVD or the like, the semiconductor wafer must be heated. Therefore, the electrostatic chuck is usually provided with a means for heating a ceramic substrate such as a resistance heating element. I have.

In order to improve the efficiency of heating an object to be heated, such as a semiconductor wafer, and to ensure corrosion resistance, a means for heating a ceramic substrate such as a resistance heating element is generally provided by a heating means. , That is, inside the ceramic substrate.

[0008]

However, when a resistance heating element is provided in a ceramic substrate and a semiconductor wafer is placed on the ceramic heating element and heating is performed, a short circuit occurs between the electrostatic electrodes during high-temperature operation. However, there is a problem that no chucking force is generated.

[0009]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of studying this problem, it was found that at a high temperature, the volume resistivity of the ceramic substrate was reduced, and as a result, a short circuit occurred via a resistance heating element.

Therefore, the present inventors have further studied and provided a resistance heating element on the side opposite to the surface of the ceramic substrate on which the ceramic dielectric film was provided (hereinafter referred to as the bottom surface), so that even at high temperatures, the resistance heating element was provided. It has been found that the insulation between the resistance heating elements can be ensured, thereby preventing a short circuit from occurring between the electrostatic electrodes via the resistance heating elements, thereby completing the present invention. .

That is, the present invention is an electrostatic chuck in which a resistance heating element is provided on a ceramic substrate, an electrostatic electrode is formed on the ceramic substrate, and a ceramic dielectric film is provided on the electrostatic electrode. , The resistance heating element,
An electrostatic chuck provided on a bottom surface of a ceramic substrate.

According to the above-mentioned electrostatic chuck, the resistance heating element is provided on the bottom surface of the ceramic substrate, and insulation between the resistance heating elements is made of an insulating material having high resistance even at a high temperature, such as air, atmospheric gas, glass, or resin. Therefore, short circuit between the electrostatic electrodes via the resistance heating element can be prevented from occurring.

The ratio (l / L) of the thickness l of the ceramic substrate to the total thickness L of the ceramic substrate and the ceramic dielectric film is 0.7 ≦ l / L <1.0. Is desirable. When 1 / L is 1.0, the ceramic dielectric film does not exist, so that a current flows through the semiconductor wafer and does not function as an electrostatic chuck. On the other hand, when 1 / L is less than 0.7, The chucking force may vary due to the influence of the temperature variation of the resistance heating element.

Preferably, the resistance heating element is coated with an insulator. This is because insulation between the resistance heating elements can be reliably ensured. It is desirable that the resistance value of the resistance heating element be adjusted by trimming. For example, by trimming the resistance heating element by laser light irradiation, forming a groove or notch and adjusting the resistance value, the temperature of the surface on which the semiconductor wafer is mounted and heated (hereinafter also referred to as a heating surface). Can be made uniform, and the semiconductor wafer or the like can be heated at a uniform temperature. The area resistivity of the resistance heating element is 0.1 to 1
Desirably, it is 0Ω / □. This is because by setting such a high sheet resistivity, a wide pattern (pattern width of 1 mm or more) can be obtained, and the influence of a variation in printing thickness can be reduced.

[0015]

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

In this electrostatic chuck 101, a semicircular arc portion 2a and a comb tooth portion 2 are formed on the surface of a disc-shaped ceramic substrate 1.
b, and an electrostatic electrode layer composed of a chuck negative electrode electrostatic layer 3 also composed of a semicircular arc-shaped part 3a and a comb tooth part 3b, and a comb tooth part 2b and a comb tooth part 3b Are formed so as to cross each other, and a thin ceramic dielectric film 4 is formed on the ceramic substrate 1 including this electrostatic electrode layer.
Are formed.

The positive and negative chucking electrostatic layers 2 and 3 have a positive and negative DC power supply, respectively.
Is connected to the side, the DC voltage V ₂ is adapted to be applied. The semiconductor wafer 9 is placed on the electrostatic chuck 101 and is grounded.

On the other hand, a resistance heating element 5 having a concentric circular shape in plan view as shown in FIG. 3 is provided at the bottom of the ceramic substrate 1 for controlling the temperature of the semiconductor wafer 9. External terminals 6 are connected to both ends of
The voltage V ₁ is fixed and applied. Although not shown in FIGS. 1 and 2, as shown in FIG. 3, this ceramic substrate 1 supports a bottomed hole 11 for inserting a temperature measuring element and a silicon wafer 9 and moves it up and down. Through hole 12 for inserting a lifter pin (not shown)
Are formed.

Then, when a DC voltage V ₂ is applied between the chucking positive electrode electrostatic layer 2 and the chucking negative electrode electrostatic layer 3, the semiconductor wafer 9 moves between the chucking positive electrode electrostatic layer 2 and the chucking negative electrode electrostatic layer 3. It is adsorbed and fixed to the ceramic dielectric film 4 by an electrostatic action (Coulomb force).

The diameter of the ceramic substrate constituting the electrostatic chuck of the present invention is desirably larger than 200 mm. This is because it is possible to cope with an increase in the size of the semiconductor wafer. The diameter of the ceramic substrate is 300 m.
m is more desirable. This is for dealing with the next generation of semiconductor wafers.

The ceramic substrate has a thickness of 20 m.
m or less, especially 10 mm or less. This is because, with the enlargement of the electrostatic chuck, the thickness is reduced to reduce the heat capacity thereof. In particular, by setting the thickness to 10 mm or less, the temperature lowering characteristics are improved. More preferably, the thickness of the ceramic substrate is 1 to 5 mm. This is because the variation in the temperature of the heating surface is reduced.

The electrostatic chuck of the present invention has the above-described configuration, and has, for example, the embodiment as shown in FIGS. In the following, each member constituting the electrostatic chuck and other embodiments of the electrostatic chuck of the present invention will be sequentially described in detail.

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. The ceramic material forming 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 such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride. Further, as the carbide ceramic, metal carbide ceramic,
For example, silicon carbide, zirconium carbide, titanium carbide,
Examples include tantalum carbide and tungsten carbide.

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 ceramic dielectric film contains 0.1 to
Desirably, it contains 20% by weight of oxygen. 0.
If the amount is less than 1% by weight, the withstand voltage cannot be ensured. On the other hand, if the amount exceeds 5% by weight, the withstand voltage also decreases due to the decrease in the high temperature withstand voltage characteristics of the oxide. On the other hand, if the oxygen content exceeds 20% by weight, the thermal conductivity decreases and the temperature rise / fall characteristics deteriorate.

In order to make the above-mentioned nitride ceramic, carbide ceramic and the like contain oxygen, usually, these raw material powders are heated in the air or oxygen or mixed with a metal oxide for firing. Examples of the metal oxide include yttria (Y ₂ O ₃ ), alumina (Al ₂ O ₃ )
₃ ), rubidium oxide (Rb ₂ O), lithium oxide (L
i ₂ O), and the like calcium carbonate (CaCO ₃₎ it is. 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 ceramic dielectric film desirably contains carbon. If it is not desired to lower the thermal conductivity of the ceramic dielectric film at high temperatures (about 500 ° C.), it is desirable to add crystalline carbon. If it is not desired to lower the volume resistivity at high temperatures, It is desirable to add amorphous carbon. Therefore, in some cases, by adding both,
Both volume resistivity and thermal conductivity can be adjusted appropriately.

The crystalline carbon may 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 5 to 5000 ppm. When the content of carbon is less than 5 ppm, radiant heat is reduced, and it is difficult to conceal the electrostatic electrode. On the other hand, when the content of carbon exceeds 5000 ppm, densification and reduction in volume resistivity are suppressed. It will be difficult to do. The carbon content is 100 to 2000 ppm
Is more preferred.

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 a resin which tends to become amorphous by heating or the like, and then added. Further, when crystalline carbon is added, crystalline carbon black or graphite powder obtained by pulverizing graphite may be used. Further, since the acrylic resin binder has a different degree of decomposability depending on the acid value, it is possible to adjust the carbon amount and the crystallinity to some extent by changing the acid value.

The thickness of the ceramic dielectric film is 50 to
Desirably, it is 10,000 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 1
If the thickness exceeds 0000 μm, the distance between the silicon wafer and the electrostatic electrode becomes long, so that 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 pressurizing 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 .

As described above, the reason that the ceramic dielectric film may have a certain amount of pores is that the presence of a certain amount of open pores on the surface of the ceramic dielectric film facilitates the dechucking. Because it can be done.

Examples of the electrostatic electrode formed on the ceramic substrate include a sintered body of metal or conductive ceramic, a metal foil, and the like. The metal sintered body is preferably made of at least one selected from tungsten and molybdenum. It is desirable that the metal foil is also made of the same material as the metal sintered body. This is because these metals are relatively hard to be oxidized and have sufficient conductivity as electrodes.
As the conductive ceramic, at least one selected from carbides of tungsten and molybdenum can be used.

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.

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 and fired under the same conditions, whereby the green sheets can be easily produced. Also, among nitride ceramics, aluminum nitride is most preferred. This is because the thermal conductivity is the highest at 180 W / m · K.

The above ceramic substrate may contain carbon. Thereby, high radiant heat is obtained. The carbon content is preferably about 5 to 5000 ppm. The carbon may be crystalline such as graphite powder, or may be amorphous formed using a carbohydrate or resin that is likely to be amorphous,
Both crystalline and amorphous may be used.

It is preferable that 0.1 to 20% by weight of a metal oxide is contained in the ceramic such as a nitride ceramic constituting the ceramic substrate, as in the case of the ceramic dielectric film. The porosity of the ceramic substrate is preferably 5% or less, and the maximum pore diameter is preferably 50 μm or less. The porosity is more preferably 0 or 3% or less, and the maximum pore size is 0 or 10 μm.
m or less is more preferable.

When the ceramic substrate is made of a non-oxide ceramic, a protective layer 37 covering the ceramic substrate 1 and the ceramic dielectric film 4 may be formed as in an electrostatic chuck 301 shown in FIG. At this time, the surface roughness of the ceramic substrate surface is desirably Ra ≦ 20 μm.
In addition, as the protective layer 37, an oxide, for example, silica,
It is desirable to be formed of at least one selected from alumina, titania, zirconia and the like.

By forming the protective layer 37, when the semiconductor wafer 9 is heated by using the resistance heating element 35 provided on the electrostatic chuck 301, heat diffusion of iron, yttrium or the like to the semiconductor wafer 9 is prevented. be able to. Therefore, the semiconductor wafer is not contaminated.

FIGS. 7 and 8 are horizontal sectional views schematically showing electrostatic electrodes in another electrostatic chuck.
8 has a semicircular chuck positive electrode electrostatic layer 22 and a chuck negative electrode electrostatic layer 23 formed inside a ceramic substrate 1. In the electrostatic chuck shown in FIG. Inside are formed chuck positive electrostatic layers 32a and 32b and chuck negative electrostatic layers 33a and 33b each having a shape obtained by dividing a circle into four parts. Also, two positive electrode electrostatic layers 22a and 22b and two chuck negative electrode electrostatic layers 3
3a and 33b are formed to cross each other. Note that an RF electrode may be provided on the electrostatic chuck. 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.

In the electrostatic chuck of the present invention, as shown in FIG. 1, a resistance heating element is provided on the bottom surface of the ceramic substrate as temperature control means. 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 above-mentioned temperature control means, in addition to the resistance heating element 5 shown in FIG.
2 (see FIG. 4). In addition, the support container into which the electrostatic chuck is fitted may be provided with an outlet for a coolant such as air as a cooling means.

As shown in FIG. 3, the resistance heating element 5 in which concentric circles partially cut are connected at adjacent ends to form a series of circuits, or FIG. As shown in the figure, a resistance heating element 65 and the like in which a resistance heating element 65a having a repeating pattern of bent lines is formed on the outer peripheral portion and resistance heating elements 65b to 65d having a concentric pattern are formed on the inside. However, the pattern of the resistance heating element is not limited to these, for example,
A pattern formed by a combination of arcs and bends,
A spiral pattern or the like may be used.

Examples of the resistance heating element include a sintered body of metal or conductive ceramic, a metal foil, and a metal wire. 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 area resistivity of the resistance heating element is 0.1
It is desirable to be 10 Ω / □.

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, scaly, or a mixture of spherical and scaly.

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.

The content of the metal oxide is desirably from 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.

The surface of the resistance heating element 5 provided on the bottom surface of the ceramic substrate is preferably covered with a metal layer 5a (see FIG. 1). The resistance heating element 5 is a sintered body of metal particles, and is easily oxidized when exposed, and the oxidation changes the resistance value. Therefore, the surface is formed by the metal layer 5a.
Oxidation can be prevented by coating with.

The thickness of the metal layer 5a is desirably 0.1 to 10 μm. Without changing the resistance value of the resistance heating element
This is because the oxidation of the resistance heating element can be prevented. The metal used for coating may be a non-oxidizing metal. Specifically, at least one selected from gold, silver, palladium, platinum, and nickel is preferable. 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.

The resistance value of the resistance heating element may be adjusted by subjecting the resistance heating element to a trimming process using a laser. At this time, a groove can be formed by trimming the surface of the resistance heating element substantially in parallel with the direction in which the current flows, and the side surface of the resistance heating element can be trimmed substantially perpendicular to the direction in which the current flows. Can form a notch. Further, the thickness of a part of the resistance heating element may be trimmed thinly over the entire width.

The groove preferably has a depth of 20% or more of the thickness of the resistance heating element. This is because the resistance value can be changed. If the depth of the groove is less than 20%, the resistance value hardly changes.

Regarding the variation of the resistance value of the resistance heating element adjusted by the trimming, the variation of the resistance value with respect to the average resistance value is preferably 5% or less, more preferably 1%. The resistance heating element is usually divided into a plurality of circuits, but by reducing the variation in resistance value in this way, the number of divisions of the resistance heating element can be reduced, and the temperature can be easily controlled. Further, it is possible to make the temperature of the heating surface uniform during the transition of the temperature rise.

The width of the groove is desirably about 1 to 100 μm. If the width exceeds 100 μm, disconnection or the like is likely to occur, while if the width is 1 μm, it is difficult to adjust the resistance value of the resistance heating element. The spot diameter of the laser beam is 1
Adjust between μm and 2 cm.

As the type of laser, for example, a YAG laser, a carbon dioxide laser, an excimer (KrF) laser,
V (ultraviolet) laser and the like. Among them, a YAG laser and an excimer (KrF) laser are most suitable.

As a YAG laser, an SAG manufactured by NEC
L432H, SL436G, SL432GT, SL41
1B can be adopted. Preferably, the laser is pulsed light. This is because large energy can be applied to the resistance heating element in an extremely short time, and damage to the ceramic substrate can be reduced. The pulse is desirably 1 kHz or less. If the frequency exceeds 1 kHz, the energy of the first pulse of the laser becomes high and the laser is excessively trimmed.

The processing speed is desirably 100 mm / sec or less. If the speed exceeds 100 mm / sec, grooves cannot be formed unless the frequency is increased. As described above, since the upper limit of the frequency is 1 kHz or less, the frequency is desirably 100 mm / sec or less.

As the temperature control means, a Peltier element which can perform both heat generation and cooling by changing the direction of current flow may be used. As shown in FIG. 4, the Peltier element 8 is formed by connecting p-type and n-type thermoelectric elements 81 in series and joining them to a ceramic substrate 82 or the like. Peltier devices include, for example, silicon-germanium, bismuth-antimony, lead,
And tellurium-based materials.

In the electrostatic chuck according to the present invention, 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. An electrostatic chuck 101 having a configuration in which the resistance heating element 5 is provided on the bottom surface of the ceramic substrate 1 is exemplified. In addition, as shown in FIG. 4, a chuck positive electrode electrostatic layer 2 and a chuck negative electrode electrostatic layer 3 are provided between the ceramic substrate 1 and the ceramic dielectric film 4, and are provided on the bottom surface of the ceramic substrate 1. An electrostatic chuck 201 having a Peltier element 8 composed of a thermoelectric element 81 and a ceramic substrate 82 is formed. As shown in FIG. A protection layer 37 is formed to cover the ceramic substrate 1 and the ceramic dielectric film 4;
An electrostatic chuck 301 having a configuration in which the resistance heating element 35 is formed on the surface of the protective layer 37 can be used.

In the present invention, as shown in FIGS. 1 to 5, 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. A connecting portion (through hole) 16 for connecting these to an external terminal is required. Through hole 16
Is 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.

The diameter of the connecting portion (through hole) 16 is preferably 0.1 to 10 mm. While preventing disconnection,
This is because cracks and distortion can be prevented. The external terminals 18 are connected using the through holes as connection pads (FIG. 6).
(D)).

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 [8
1.5 to 82.5 (% by weight)] / [18.5 to 17.5
(% By weight)] is desirable. The thickness of the Au—Ni layer is 0.1 μm.
1 to 50 μm is desirable. This is because the range is sufficient to secure the connection. Further, at a high vacuum of 10 ^-6 to 10 ^-5 Pa, 5
When used at a high temperature of 00 to 1000 ° C., the Au—Cu alloy deteriorates, but the Au—Ni alloy is advantageous because such deterioration does not occur. The amount of the impurity element in the Au—Ni alloy is desirably less than 1 part by weight when the total amount is 100 parts by weight.

In the present invention, a thermocouple can be embedded in the bottomed hole 11 of the ceramic substrate 1 as needed. 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. As the thermocouple, for example,
As described in JIS-C-1602 (1980), K-type, R-type, B-type, S-type, E-type, J-type, and T-type thermocouples are included.

FIG. 9 is a cross-sectional view schematically showing a support container 41 for disposing the electrostatic chuck of the present invention having the above-described structure. The support container 41 includes the electrostatic chuck 10
1 is fitted through a heat insulating material 45. In addition, the support container 11 has a refrigerant outlet 42.
Is formed, and the refrigerant is blown from the refrigerant injection port 44 and goes out of the suction port 43 through the refrigerant discharge port 42, and the electrostatic chuck 101 is cooled by the action of the refrigerant. You can do it. Further, the support container may be configured such that, after placing the ceramic substrate on the upper surface of the support container, the support substrate is fixed with a fixing member such as a bolt.

Next, an example of the method for manufacturing the electrostatic chuck according to the present invention will be described with reference to the sectional views shown in FIGS. (1) First, a ceramic powder such as an oxide ceramic, a nitride ceramic, or a carbide ceramic is mixed with an auxiliary agent, a binder, a solvent, and the like to prepare a paste, and the paste is formed into a sheet by a doctor blade method or the like. The green sheet 50 is formed by molding. As the above-mentioned ceramic powder, for example, aluminum nitride, silicon carbide or the like can be used, and if necessary, a sintering aid such as yttria or carbon may be added.

It is to be noted that several or one green sheet 50 laminated on a green sheet on which an electrostatic electrode layer printed body 51 to be described later 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. Because these are often sintered together,
This is because suitable 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. Further, as the solvent, at least one selected from α-terpineol and glycol is desirable.

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 to be an electrostatic electrode layer is printed on the green sheet 50. 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 printed body 51.
The printed body is formed by printing a conductive paste containing conductive ceramic, 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 hard to be oxidized and the thermal conductivity is hard to decrease. Further, as the metal particles, for example, tungsten, molybdenum, platinum, nickel and 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 to print the conductor paste when these particles are too large or too small. As such a paste, 85 to 97 parts by weight of metal particles or conductive ceramic particles, 1.5 to 10 parts by weight of at least one binder selected from acrylic, ethyl cellulose, butyl cellosolve and polyvinyl alcohol, α-terpineol, glycol A paste for a conductor prepared by mixing 1.5 to 10 parts by weight of at least one solvent selected from ethyl alcohol and butanol is most suitable. Further, a conductor paste is filled into the holes formed by punching or the like, to obtain a through-hole print 53.

Next, as shown in FIG.
The green sheet 50 having Nos. 1 and 53 and the green sheet 50 having no printed body are laminated. On the green sheet on which the electrostatic electrode layer printed body 51 is formed, several or one green sheet 50 having the above-described configuration is laminated.
Green sheet 5 having no printed body on the side where the resistance heating element is formed
The reason why 0 is laminated 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 with the end face of the through hole exposed, it is necessary to sputter a metal which is hardly oxidized such as nickel. Furthermore, it is preferable to coat with Au-Ni gold solder.

(2) Next, as shown in FIG. 6B, 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 100 to 200 kg / cm ^{2 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 hole 16, the chuck positive electrode electrostatic layer 2, the chuck negative electrode electrostatic layer 3, and the like are formed.

(3) Next, as shown in FIG. 6C, a conductor paste for forming the resistance heating element 5 is printed on the ceramic substrate 1. Thereafter, the ceramic substrate 1 on which the conductive paste layer is printed is fired, so that the resistance heating element 5 is formed.
To form The resistance heating element 5 is formed by electroless plating or the like.
It is desirable to form a metal coating layer (not shown) on the surface of the substrate. This is because oxidation of the resistance heating element 5 can be prevented, and a change in resistance value can be prevented.

(4) Finally, as shown in FIG.
External terminals 6 and 18 are provided in a blind hole (not shown) via a brazing material such as gold brazing. Further, if necessary, the bottomed hole 1
2 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
５０50 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 the Peltier device 8, a ceramic substrate having an electrostatic electrode layer may be manufactured, and then the Peltier device 8 may be joined to the ceramic substrate via a sprayed metal layer or the like. further,
When the electrostatic chuck 301 (see FIG. 5) is manufactured, after a ceramic substrate having an electrostatic electrode layer is manufactured, a sol solution or the like is applied, and the protective layer 37 is formed by drying and baking. Print conductive paste on the bottom of the board,
After baking, the resistance heating element 35 is formed, and thereafter, the metal coating layer 35a may be formed by electroless plating or the like.

[0084]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. (Example 1) (1) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama Corporation, average particle size: 1.1 μm), yttria (average particle size:
0.4 μm) Using a paste obtained by mixing 4 parts by weight, 11.5 parts by weight of an acrylic binder, 0.5 parts by weight of a dispersant, and 53 parts by weight of alcohol composed of 1-butanol and ethanol, molding is performed by a doctor blade method. hand,
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, punch 1.8m in diameter
m, a portion serving as a through hole for inserting a lifter pin for a 3.0 mm and 5.0 mm semiconductor wafer, and a portion serving as a through hole for connecting to an external terminal 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. This conductive paste A was printed on a green sheet by screen printing to form a conductive 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 after the above processing, two green sheets 50 on which the tungsten paste is not printed are further laminated on the upper side (heating surface) and 48 on the lower side.
The laminate was formed by pressure bonding at 0 ° C. and a pressure of 80 kg / cm ² .

(4) Next, the obtained laminate was degreased in nitrogen gas at 600 ° C. for 5 hours, and at 1890 ° C. under a pressure of 150
It was hot-pressed at kg / cm ² for 3 hours to obtain an aluminum nitride plate having a thickness of 25 mm. This was cut out into a 210 mm disk shape, and a plate-like body made of aluminum nitride having a chuck positive electrode electrostatic layer 2 and a chuck negative electrode electrostatic layer 3 having a thickness of 15 μm therein and having a dielectric film thickness of 1 mm. did.

(5) A mask was placed on the bottom of the plate obtained in (4) above, and a recess (not shown) for a thermocouple was provided on the surface by blasting with SiC or the like. (6) Next, a conductor layer serving as the resistance heating element 5 was printed on the surface (bottom surface) facing the wafer mounting surface by screen printing. The pattern of the printed resistance heating element was the same pattern as the resistance heating element 5 of FIG. For printing, a conductor paste was used. The conductive paste is Solvest PS manufactured by Tokurika Chemical Laboratory, which is used to form through holes in printed wiring boards.
603D was used. This conductor paste is a silver / lead paste, and includes lead oxide, zinc oxide, silica, boron oxide,
Metal oxide composed of alumina (the weight ratio of each is
5/55/10/25/5) was contained in an amount of 7.5 parts by weight based on 100 parts by weight of silver. The silver had a scaly shape with an average particle size of 4.5 μm.

(7) The plate-like body on which the conductor paste is printed is
By heating and baking at 80 ° C., silver and lead in the conductor paste were sintered and baked on a ceramic substrate. Further, the plate was 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 5 was thickened. A metal coating layer 5a 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 5 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., an external terminal made of Kovar was connected. External terminals 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 101. (10) Next, the electrostatic chuck 101 was fitted into a stainless steel support container 41 having a cross-sectional shape shown in FIG. 9 via a heat insulating material 45 made of ceramic fiber (trade name: IBIWOOL, manufactured by IBIDEN). The supporting container 41 has a cooling gas outlet 42 for cooling gas, and the electrostatic chuck 1
01 temperature adjustment can be performed. This support container 41
The resistance heating element 5 of the electrostatic chuck 101 fitted in the heater was energized to raise the temperature, and the temperature of the electrostatic chuck 101 was controlled by flowing a coolant through the supporting container. I was able to.

(Example 2) An electrostatic chuck was manufactured in the same process as in Example 1. However, the pattern of the resistance heating element had the same shape as the pattern of the resistance heating element shown in FIG. Also, 10 green sheets are placed on the upper side and 4 green sheets are placed on the lower side.
By stacking 0 sheets, an electrostatic chuck having a dielectric film thickness of 5 mm and a ceramic substrate thickness of 20 mm was manufactured.

Example 3 An electrostatic chuck was manufactured through substantially the same steps as in Example 1. However, 20 green sheets are stacked on the upper side and 30 green sheets are stacked on the lower side to form a ceramic substrate having a dielectric film thickness of 10 mm and a ceramic substrate thickness of 15 mm, and a resistance heating element is formed. Glass paste on the surface (G-525 manufactured by Shoei Chemical Industry Co., Ltd.)
8T), heated to 600 ° C. and heated to a thickness of 20
The resistance heating element was covered with a μm insulator.

Comparative Example 1 (1) The same steps as in (1) and (2) of Example 1 were performed to obtain a green sheet having a portion to be a through hole and a portion to be a through hole.

(2) Conductor paste A as in Example 1
A conductor paste B was prepared. The conductor paste A was printed on a green sheet by screen printing to form a conductor paste layer serving as a resistance heating element. The printing pattern had the same shape as the resistance heating element 5 shown in FIG. Further, a conductor paste layer composed of an electrostatic electrode pattern having the shape shown in FIG. 2 was formed on another green sheet.

(3) Further, a conductive paste B was filled in a through hole for a through hole for connecting an external terminal.
On the green sheet on which the conductive paste layer having the same pattern as that of the resistance heating element 5 is formed, 34 green sheets on which the conductive paste layer is not formed are further formed on the upper side (heating surface).
13 sheets are laminated on the lower side, and a green sheet on which a conductive paste layer composed of an electrostatic electrode pattern is printed is laminated thereon,
Two green sheets on which the conductor paste was not printed were laminated thereon, and these were pressed at 130 ° C. under a pressure of 80 kg / cm ² to form a laminate.

(4) Next, the obtained laminate was degreased in nitrogen gas at 600 ° C. for 5 hours, and at 1890 ° C. under a pressure of 150
It was hot-pressed at kg / cm ² for 3 hours to obtain an aluminum nitride plate having a thickness of 5 mm. This was cut into a disk of 210 mm, and an aluminum nitride ceramic substrate having a 6 μm-thick and 10 mm-wide resistance heating element and a 10 μm chuck positive electrode electrostatic layer and a chuck negative electrode electrostatic layer of 10 μm inside was cut out.

(5) Thereafter, (5) to (9) of Example 1
Was carried out to obtain an electrostatic chuck having a resistance heating element inside a ceramic substrate.

Comparative Example 2 An electrode made of nickel foil having a thickness of 20 μm was formed on a surface of a ceramic substrate using a glass paste (manufactured by Shoei Chemical Industry Co., Ltd.) without printing the electrode on the green sheet.
G-5258T), and the temperature was raised to 600 ° C. to form electrodes on the surface of the ceramic substrate.
An electrostatic chuck was manufactured in the same manner as described above.

[0101]Evaluation method  (1) Measurement of leakage current The electrostatic chucks according to the example and the comparative example were heated to 400 ° C.
And apply 500 V to flow between the electrostatic electrode and the heating element.
The amount of current flowing was measured.

(2) Measurement of Variation in Chuck Force of Silicon Wafer The silicon wafer divided into 10 was placed on the electrostatic chucks according to the embodiment and the comparative example, and energization was performed, and the electrostatic chuck was heated to 400 ° C. did. Then, the chucking force of the silicon wafer in each divided section was measured with a load cell, and the average value was calculated. Furthermore, the difference between the maximum chucking force and the minimum chucking force was divided by the average and expressed as a percentage.

[0103]

[Table 1]

As a result, as is apparent from Table 1, 1 /
When L was less than 0.7, the chucking force varied. It is considered that the reason for this is that the chucking force changes due to the temperature variation of the resistance heating element because the electrostatic electrode is too close to the resistance heating element. Also, it was found that the formation of the resistance heating element on the surface can reduce the leakage current, rather than the formation of the resistance heating element inside.

[0105]

As described above, in the electrostatic chuck of the present invention, since the resistance heating elements are provided on the bottom surface of the ceramic substrate, insulation between the resistance heating elements can be ensured even at a high temperature. This can prevent a short circuit from occurring between the electrostatic electrodes via the resistance heating element.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing one example of an 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 plan view of the electrostatic chuck shown in FIG. 1 as viewed from a bottom surface side.

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

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

FIGS. 6A to 6D are longitudinal sectional views schematically showing a part of a manufacturing process of the electrostatic chuck.

FIG. 7 is a horizontal sectional view schematically showing one example of an electrostatic electrode constituting the electrostatic chuck of the present invention.

FIG. 8 is a horizontal sectional view schematically showing one example of an electrostatic electrode constituting the electrostatic chuck of the present invention.

FIG. 9 is a cross-sectional view schematically showing a state where the electrostatic chuck of the present invention is fixed to a supporting container.

FIG. 10 is a plan view of one example of the electrostatic chuck of the present invention as viewed from the bottom surface side.

[Explanation of symbols]

1, 21, 31, 61, 82 Ceramic substrate 2, 22, 32a, 32b Chuck positive electrode electrostatic layer 2a, 3a Semi-circular part 2b, 3b Comb tooth part 3, 23, 33a, 33b Chuck negative electrode electrostatic layer 4 Ceramic Dielectric film 5, 35, 65 (65a to 65d) Resistance heating element 5a, 35a Metal coating layer 6 External terminal 8 Peltier device 9 Semiconductor wafer 20, 30, 60, 101, 201, 301 Electrostatic chuck 11, 61 Bottom Holes 12, 62 Through holes 16 Through holes 37 Protective layer 41 Support container 42 Refrigerant outlet 43 Suction port 44 Refrigerant inlet 45 Insulation material 81 Thermoelectric element

Continued on the front page F term (reference) 3C016 CE05 GA10 3K034 AA02 AA05 AA10 AA16 AA19 AA21 AA28 AA34 AA37 BA06 BA14 BB06 BB14 BC04 BC17 DA04 HA10 JA02 JA10 5F031 CA02 HA02 HA16 HA37 MA28 MA30 PA11 PA30

Claims (4)

[Claims] 1. A resistance heating element is provided on a ceramic substrate, and an electrostatic electrode is formed on the ceramic substrate.
An electrostatic chuck in which a ceramic dielectric film is integrally provided on the electrostatic electrode, wherein the resistance heating element is provided on a side of the ceramic substrate opposite to a surface on which the ceramic dielectric film is provided. An electrostatic chuck characterized in that: 2. The ratio (l / L) of the thickness l of the ceramic substrate to the total thickness L of the ceramic substrate and the ceramic dielectric film is 0.7 ≦ l / L <1. The electrostatic chuck according to claim 1, wherein the value is zero. 3. The electrostatic chuck according to claim 1, wherein the resistance heating element is covered with an insulator. 4. The electrostatic chuck according to claim 1, wherein the resistance value of the resistance heating element is adjusted by trimming.