JP2008177339A - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck which remarkably reduces the number of particles attaching to the rear face of a plate-like sample even if the plate-like sample stuck by electrostatic attraction on a mounting plane by irradiation of electron beams is electrified, and can quickly separate the plate-like sample stuck by electrostatic attraction from the mounting plane when the application of voltage is stopped. <P>SOLUTION: The electrostatic chuck comprises: a base 7 which has one principal plane serving as a mounting plane 2a for mounting the plate-like sample and includes internal electrodes 4 and 4 for electrostatic attraction inside; and terminals 6 and 6 which are held by the base 7 and apply voltage to the internal electrodes 4 and 4 for electrostatic attraction. The base 7 is made of a flat plate-like silicon carbide-aluminum oxide composite sintered material containing not less than 1 mass% and not more than 30 wt.% of silicon carbide, and the surface roughness Ra of the mounting plane 2a is 0.01 μm or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatic chuck, and more specifically, particles that are suitably used during electron beam irradiation when a plate-like sample such as a semiconductor wafer electrostatically attracted to a mounting surface is charged and adhere to the back surface of the plate-like sample. The present invention relates to an electrostatic chuck that can greatly reduce the number and can quickly detach a plate-like sample that has been electrostatically adsorbed from a mounting surface when voltage application is stopped.

The electrostatic chuck is provided with an internal electrode for electrostatic attraction inside a dielectric serving as a base. One main surface of the base is used as a mounting surface, and a plate-like sample such as a semiconductor wafer is mounted on the mounting surface. The plate sample is adsorbed and fixed by generating an electrostatic force between the plate sample and the electrostatic adsorption internal electrode.
This electrostatic chuck generates an electrostatic force almost uniformly over the entire surface of the plate-like sample by making the thickness of the dielectric constant and making the internal electrode for electrostatic adsorption substantially the same size as the plate-like sample. Therefore, the processing surface of the plate-like sample can be fixed with high precision so that it is flat, and since it uses electrostatic attraction force, it is hardly affected by the surrounding atmosphere, and even under vacuum Since it can be used, it is widely used in a semiconductor manufacturing process in which a plate-like sample such as a semiconductor wafer is subjected to a film forming process, an etching process, an exposure process, and the like.

  Incidentally, in recent years, in the semiconductor manufacturing process, it is required to prevent metal contamination, dust, dust and other particles from adhering to a plate-like sample such as a semiconductor wafer by integrating ICs and the like. That is, it is required to suppress the adhesion of particles that cause a decrease in the yield of a plate-like sample such as a semiconductor wafer in various processing steps. In film formation processing, etching processing, exposure processing, etc. There is an urgent need to reduce the adhesion of particles to the back surface of a plate-like sample such as an electroadsorbed semiconductor wafer.

However, in the conventional electrostatic chuck, the mounting surface (electrostatic adsorption surface) in contact with the plate-shaped sample such as a semiconductor wafer is rubbed with the plate-shaped sample such as the semiconductor wafer, and the dielectric material constituting the mounting surface There is a problem that at least particles are present due to particle sag, etc., and if the particles adhere to the back surface of a plate-like sample such as a semiconductor wafer to be electrostatically adsorbed, the productivity of the semiconductor decreases. .
Therefore, there is a strong demand to reduce the number of particles adhering to the back surface of a plate-like sample such as a semiconductor wafer.

As an electrostatic chuck capable of reducing the number of particles on the back surface of a plate-like sample, for example, the upper surface of a ceramic plate-like body having an internal electrode for electrostatic adsorption is used as an adsorption surface, and a shot blast method is applied to this adsorption surface. A concave portion is formed by, for example, the area ratio of the contact portion between the concave portion and the plate-like sample is 10 to 30%, and the surface roughness R _max (maximum height) of the contact portion is 0.8 μm or less. An electrostatic chuck has been proposed (Patent Document 1).
In addition, a large number of protrusions are formed on the upper surface of the dielectric layer containing the internal electrode for electrostatic adsorption by shot blasting or the like, and the upper surface serving as the adsorption surface of the protrusion has a surface roughness R _max (maximum height). Proposed is an electrostatic chuck in which R is 2.0 μm or less or R _a (centerline average height) is 0.25 μm or less, and the area ratio of the total area of the upper surface of the protrusion to the upper surface of the dielectric layer is 1 to 10% (Patent Document 2).

In these electrostatic chucks, a concave portion and a large number of protrusions are formed on the upper surface, which is the mounting surface, so that the area ratio of the contact portion with respect to the entire suction surface is within a predetermined range. I keep it. In addition, by forming recesses and many projections on the adsorption surface, particles generated by contact (rubbing) between the plate-like sample and the adsorption surface and detachment from the mounting surface fall between the depressions and projections, resulting in a plate-like shape. It is said that particles do not easily adhere to the back surface of the sample, and that the detachability of the plate-like sample can be improved.
Furthermore, an electrostatic chuck in which a mounting plate on which a plate-like sample is mounted is formed of a silicon carbide-aluminum oxide composite sintered body has also been proposed (Patent Documents 3 to 5).
JP-A-5-6933 Japanese Patent Laid-Open No. 7-153825 JP-A-8-283606 JP 2001-351969 A Japanese Patent Laid-Open No. 2003-152065

However, in the conventional electrostatic chuck in which concave portions and many protrusions are formed on the mounting surface, when used during electron beam irradiation, the plate-like sample electrostatically adsorbed by the electron beam irradiation is charged, so that the inside of the concave portion is charged. Since the particles falling on the plate-like sample are electrostatically adsorbed on the back surface of the plate-like sample, there is still a problem that the particles adhere to the back surface of the plate-like sample.
In addition, the electrostatic chuck in which the conventional mounting plate is formed of a silicon carbide-aluminum oxide composite sintered body is intended to ensure good insulation of the mounting plate, and is irradiated with an electron beam. No consideration is given to the reduction of the number of particles when the electrostatically adsorbed plate-like sample is charged.

  The present invention has been made to solve the above problems, and even when the plate-like sample electrostatically adsorbed on the mounting surface by the electron beam irradiation is charged during the electron beam irradiation, An electrostatic chuck that can significantly reduce the number of particles adhering to the back surface of a plate-shaped sample and quickly detach the plate sample that has been electrostatically adsorbed from the mounting surface when voltage application is stopped The purpose is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the substrate is a flat silicon carbide-aluminum oxide composite sintered body containing 1% by mass to 30% by mass of silicon carbide. If the mounting surface on which the plate-like sample of the substrate is formed is mirror-polished so that the surface roughness Ra is 0.01 μm or less, the back surface of the plate-like sample is obtained even when irradiated with an electron beam. The number of particles adhering to the substrate is greatly reduced, and when the voltage application is stopped, it is found that the electrostatically adsorbed plate-like sample can be quickly detached from the mounting surface, and the present invention is completed. It was.

  That is, the electrostatic chuck of the present invention is an electrostatic chuck used at the time of electron beam irradiation, and has one main surface as a mounting surface on which a plate-like sample is mounted and an internal electrode for electrostatic adsorption is provided inside. And a power supply terminal which is held by the substrate and applies a voltage to the internal electrode for electrostatic adsorption, and the substrate contains silicon carbide in an amount of 1% by mass to 30% by mass. It is formed by a flat silicon carbide-aluminum oxide composite sintered body, and the surface roughness Ra of the mounting surface is 0.01 μm or less.

  In this electrostatic chuck, the substrate is formed of a flat silicon carbide-aluminum oxide composite sintered body containing silicon carbide in an amount of 1% by mass to 30% by weight, and the surface roughness of the mounting surface. By setting Ra to 0.01 μm or less, there is no degranulation from the mounting surface, and therefore the number of particles generated is reduced. Thereby, even if this electrostatic chuck is used at the time of electron beam irradiation, the number of particles adhering to the back surface of the electrostatically attracted plate-like sample is greatly reduced.

The electrostatic chuck of the present invention is characterized in that the average particle diameter of the aluminum oxide particles in the silicon carbide-aluminum oxide composite sintered body is 5 μm or less.
In this electrostatic chuck, since the average particle diameter of the aluminum oxide particles is set to 5 μm or less, there is no degranulation from the mounting surface, and therefore the number of generated particles is greatly reduced. Thereby, even if this electrostatic chuck is used at the time of electron beam irradiation, the number of particles adhering to the back surface of the electrostatically attracted plate-like sample is further greatly reduced.

The electrostatic chuck of the present invention is characterized in that an average particle diameter of silicon carbide particles in the silicon carbide-aluminum oxide composite sintered body is 1 μm or less.
In this electrostatic chuck, by setting the average particle diameter of the silicon carbide particles to 1 μm or less, there is no degranulation from the mounting surface, and therefore the number of generated particles is greatly reduced. Thereby, even if this electrostatic chuck is used at the time of electron beam irradiation, the number of particles adhering to the back surface of the electrostatically attracted plate-like sample is further greatly reduced.

  According to the electrostatic chuck of the present invention, the substrate is formed of a flat silicon carbide-aluminum oxide composite sintered body containing silicon carbide in an amount of 1% by mass to 30% by weight, and the mounting surface. Since the surface roughness Ra is set to 0.01 μm or less, it is possible to eliminate degranulation from the mounting surface and to reduce the number of particles generated. Therefore, even when this electrostatic chuck is used at the time of electron beam irradiation, the number of particles adhering to the back surface of the electrostatically adsorbed plate sample can be greatly reduced.

  Moreover, since the average particle diameter of the aluminum oxide particles is set to 5 μm or less, it is possible to eliminate the degranulation from the mounting surface, and to greatly reduce the number of particles generated. Therefore, even if this electrostatic chuck is used at the time of electron beam irradiation, the number of particles adhering to the back surface of the electrostatically adsorbed plate-like sample can be further greatly reduced.

  Moreover, since the average particle diameter of the silicon carbide particles is set to 1 μm or less, it is possible to eliminate degranulation from the mounting surface, and to greatly reduce the number of particles generated. Therefore, even if this electrostatic chuck is used at the time of electron beam irradiation, the number of particles adhering to the back surface of the electrostatically adsorbed plate-like sample can be further greatly reduced.

The best mode of the electrostatic chuck of the present invention will be described with reference to the drawings.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

  FIG. 1 is a plan view showing a bipolar electrostatic chuck according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, and the upper surface of the electrostatic chuck 1 is a semiconductor wafer. A mounting surface 2a on which a plate-like sample such as a mounting surface 2a is mounted, a support plate 3 that is integrated with the mounting plate 2 and supports the mounting plate 2, and the mounting plate 2 The electrostatic adsorption internal electrodes 4, 4 provided between the support plate 3 and the insulating material layer 5 that insulates the periphery of the electrostatic adsorption internal electrodes 4, 4, and penetrates the support plate 3 and supports the support plate 3. And the power feeding terminals 6 and 6 which are integrated with each other and apply a DC voltage to the electrostatic adsorption internal electrodes 4 and 4 respectively.

Furthermore, DC power supplies 8 and 9 are connected to the power feeding terminals 6 and 6 so that the respective potentials are positive or negative, and the DC power supplies 8 and 9 are grounded.
Here, the term “integrated integration” means that they are closely fixed and integrated with no gap only by fitting, and are different from those integrated by adhesion or bonding.

The mounting plate 2 and the support plate 3 are disk-shaped with the same shape of the superimposed surface, and silicon carbide is 1% by mass to 30% by weight, preferably 3% by mass to 20% by weight. % Or less of silicon carbide-aluminum oxide composite sintered body.
The mounting surface 2a of the mounting plate 2 has a surface roughness (arithmetic mean roughness) Ra of 0.01 μm (10 nm) or less, preferably 0.005 μm (5 nm) or less, more preferably 0.003 μm (3 nm). It is mirror-polished to be as follows. The mounting surface 2a thus mirror-polished is less shed and worn even when it comes into contact with the plate-like sample to be mounted, and the generation of particles can be greatly reduced.

The average particle diameter of the aluminum oxide particles in the silicon carbide-aluminum oxide composite sintered body constituting the mounting plate 2 is preferably 5 μm or less, more preferably 2 μm or less.
By setting the average particle diameter of the aluminum oxide particles in the above range, even if the mounting surface 2a comes into contact with the plate-like sample, there is no degranulation or wear, and the generation of particles can be further reduced.

Moreover, the average particle diameter of the silicon carbide particles in the silicon carbide-aluminum oxide composite sintered body constituting the mounting plate 2 is preferably 1 μm or less, more preferably 0.5 μm or less.
By setting the average particle diameter of the silicon carbide particles within the above range, even if the mounting surface 2a comes into contact with the plate-like sample, there is no degranulation or wear, and the generation of particles can be further reduced.

The mounting plate 2 and the support plate 3 are joined and integrated by an insulating material layer 5 made of an insulating material having the same composition or main component as the material constituting them by hot pressing under high temperature and high pressure described later. ing.
The insulating material layer 5 is for joining and integrating the boundary portion between the mounting plate 2 and the support plate 3, that is, the outer peripheral region other than the electrostatic adsorption internal electrodes 4 and 4.
The mounting plate 2, the support plate 3, the electrostatic adsorption internal electrodes 4, 4, and the insulating material layer 5 constitute a base 7.

The electrostatic adsorption internal electrodes 4 and 4 are used as an electrostatic chuck electrode for generating a charge and fixing the plate-like sample with an electrostatic adsorption force. Is adjusted accordingly. In FIG. 1, it is a wide semicircular ring.
The electrostatic adsorption internal electrodes 4 and 4 are made of aluminum oxide-tantalum carbide conductive composite sintered body, aluminum oxide-tungsten conductive composite sintered body, aluminum oxide-silicon carbide conductive composite sintered body, aluminum nitride- It is made of conductive ceramics such as tungsten conductive composite sintered body, aluminum nitride-tantalum conductive composite sintered body, or refractory metals such as tungsten, tantalum, and molybdenum.
In consideration of integration of the electrostatic adsorption internal electrodes 4, 4 with the mounting plate 2 and the support plate 3, conductive ceramics are preferable. The composition of the conductive ceramic is preferably such that the main component is the same as that of the insulating ceramic constituting the mounting plate 2 and the support plate 3 so that the thermal expansion coefficients are approximated.

The power feeding terminals 6, 6 are rod-shaped terminals provided for applying a DC voltage to the electrostatic adsorption internal electrodes 4, 4, and the electric conductivity constituting the electrostatic adsorption internal electrodes 4, 4. It is made of ceramics or a refractory metal such as tungsten, tantalum or molybdenum.
Considering that the power supply terminals 6 and 6 are integrated with the support plate 3, conductive ceramics are preferable. It is preferable that the composition of the conductive ceramic is the same as the main component of the insulating ceramic constituting the support plate 3 so that the thermal expansion coefficient is approximated.
The power feeding terminals 6 and 6 are fitted and integrated with the support plate 3 by a hot press process under high temperature and high pressure described later.

Next, a method for manufacturing the electrostatic chuck 1 will be described.
First, the disk-shaped mounting plate 2 and the support plate 3 are produced from a silicon carbide-aluminum oxide composite sintered body.
In this case, the silicon carbide powder is formed into a desired shape by mixing a powder mixture of 1% by mass or more and 30% by weight or less and the balance of the aluminum oxide powder, and then, for example, a temperature of 1600 ° C. to 2000 ° C., a non-oxidizing atmosphere, Preferably, the mounting plate 2 and the support plate 3 are obtained by baking for a predetermined time in an inert atmosphere. The silicon carbide-aluminum oxide composite sintered body thus obtained has a volume resistivity of about 10 ⁸ Ω · cm to 10 ¹⁵ Ω · cm at room temperature (25 ° C.), and adsorbs a plate-like sample. The response at the time of separation (desorption) is remarkably improved.

  In producing this silicon carbide-aluminum oxide composite sintered body, the silicon carbide powder is preferably a powder having an average particle diameter of 1 μm or less, preferably 0.5 μm or less. The reason is that when silicon carbide powder having an average particle diameter exceeding 1 μm is used, the average particle diameter of silicon carbide particles in the obtained composite sintered body exceeds 1 μm, and the strength due to the addition of silicon carbide. This is because the improvement effect is small.

As the silicon carbide powder to be used, a powder obtained by a plasma CVD method is preferable. In particular, it is obtained by introducing a silane compound or a mixed gas of silicon halide and hydrocarbon into plasma in a non-oxidizing atmosphere, and performing a gas phase reaction while controlling the pressure of the reaction system in the range of 1 atm to 0.1 Torr. The obtained ultrafine powder having an average particle size of 0.1 μm or less is excellent in sinterability, high purity, and spherical in particle shape, and therefore has good dispersibility during molding.
On the other hand, the aluminum oxide powder is not particularly limited as long as it has a high purity. In particular, a powder having an average particle diameter of 5 μm or less is preferable because it has excellent sinterability and high adsorbing power.

  In this silicon carbide-aluminum oxide composite sintered body, a small amount of impurities is allowed. However, the decrease in lifetime and gate voltage in the semiconductor manufacturing process is caused by transition metal elements and alkali metals, and therefore, transition metal elements and alkali metals are not preferable as impurities. Furthermore, if the content of metal impurities other than aluminum and silicon exceeds 0.1% by weight, the possibility of contaminating the semiconductor wafer increases and the temperature dependency of the electrical resistance of the electrostatic chuck increases, which is preferable. Absent. Therefore, the content of metal impurities other than aluminum and silicon in the silicon carbide-aluminum oxide composite sintered body is preferably 0.1% by weight or less.

  Next, a plurality of fixing holes for fitting and holding the power supply terminals 6, 6 are formed in the support plate 3. The method for drilling these fixed holes is not particularly limited, but for example, drilling using a diamond drill, laser machining, electric discharge machining, ultrasonic machining, or the like can be used. it can. Further, the processing accuracy may be normal processing accuracy, and the yield is almost 100%.

Next, for example, the diameter of the power supply terminal 6 is made 10 to 100 μm smaller than the inner diameter of the fixed hole so that the power supply terminal 6 has a size and shape that can be fixed in close contact with the fixed hole of the support plate 3. Make it. As a method for producing the power supply terminal 6, for example, when the power supply terminal 6 is a conductive composite sintered body, a method of forming a conductive ceramic powder into a desired shape and pressurizing and firing it can be cited. . The conductive ceramic powder used at this time is preferably a conductive ceramic powder made of the same material as the electrostatic adsorption internal electrodes 4 and 4.
Moreover, when the power supply terminal 6 is made of metal, a method of using a refractory metal and a metal working method such as a grinding method or powder metallurgy, or the like can be used.
The power supply terminal 6 is refired at the time of subsequent hot pressing under high temperature and high pressure, is closely fixed to the support plate 3, and is integrally fitted.

Next, the conductive material such as the conductive ceramic powder is made of an organic material such as ethyl alcohol so as to come into contact with the power supply terminals 6 and 6 in a predetermined region on the surface of the support plate 3 in which the power supply terminals 6 and 6 are fitted. A coating liquid for forming an internal electrode for electrostatic adsorption dispersed in a solvent is applied and dried to form an internal electrode forming layer for electrostatic adsorption.
As this coating method, it is desirable to use a screen printing method or the like because it is necessary to apply the film to a uniform thickness. Other methods include forming a thin film of the refractory metal by vapor deposition or sputtering, or arranging an electroconductive ceramic or refractory metal thin plate to provide an internal electrode for electrostatic adsorption. There is a method of forming a formation layer.

  Further, in order to improve insulation, corrosion resistance, and plasma resistance in a region other than the region where the electrostatic adsorption internal electrode forming layer is formed on the support plate 3, the same as the mounting plate 2 and the support plate 3 The insulating material layer 5 including a powder material having the same composition or main component is formed. The insulating material layer 5 is formed by, for example, applying a coating liquid in which an insulating material powder having the same composition or the same main component as the mounting plate 2 and the supporting plate 3 is dispersed in an organic solvent such as ethyl alcohol to the predetermined region by screen printing or the like It can be formed by applying and drying.

Next, the mounting plate 2 is overlaid on the electrostatic adsorption internal electrode forming layer and the insulating material layer 7 on the support plate 3, and then these are integrated by hot pressing under high temperature and high pressure. The atmosphere at this time is preferably a vacuum or an inert atmosphere such as Ar, He, N ₂ or the like. The pressure is preferably 5 to 10 MPa, and the temperature is preferably 1600 ° C to 1850 ° C.

By this hot pressing, the internal electrode forming layer for electrostatic adsorption is fired to become the internal electrodes 4 and 4 for electrostatic adsorption made of a conductive composite sintered body. At the same time, the support plate 3 and the mounting plate 2 are joined and integrated through the insulating material layer 5.
The power feeding terminals 6 and 6 are refired by hot pressing under high temperature and high pressure, and are fixed in close contact with the fixing holes of the support plate 3.
Finally, the surface of the mounting plate 2 is polished using a lapping machine, for example, so that the surface roughness Ra (arithmetic mean roughness) is 0.01 μm (10 nm) or less. Let the surface be a mounting surface 2a.

In this manufacturing method, an adhesive or bonding agent made of organic matter or metal is not interposed between the fixing hole of the support plate 3 and the power feeding terminal 6 and between the support plate 3 and the mounting plate 2. These are joined and integrated only by firing under pressure.
That is, the mounting plate 2, the support plate 3, the electrostatic adsorption internal electrodes 4, 4, the insulating material layer 5, and the power feeding terminals 6, 6 are integrated in a closely contacted state.
As described above, the electrostatic chuck 1 of this embodiment can be manufactured.

  In this embodiment, the bipolar electrostatic chuck is described as an example. However, the electrostatic chuck of the present invention is not limited to the bipolar type, and can be applied to a single type electrostatic chuck. can do.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.
"Example 1"
(Production of power supply terminals)
40 parts by weight of aluminum oxide powder (average particle size 0.2 μm, manufactured by Daimei Chemicals Co., Ltd.), tantalum carbide powder (average particle size 1 μm, manufactured by Nippon Shin Metal Co., Ltd.), 2-propanol 150 The parts by weight were mixed and further dispersed uniformly using a planetary ball mill to obtain a slurry. From this slurry, 2-propanol was removed by suction filtration and then dried to obtain an aluminum oxide-tantalum carbide composite powder.

Next, this aluminum oxide-tantalum carbide composite powder is molded, and then pressed and fired to obtain a rod-shaped aluminum oxide-tantalum carbide conductive composite sintered body having a diameter of 2.5 mm and a length of 10 mm, which is used as a power supply terminal. It was set to 6. The pressure firing was performed using a hot press under conditions of a temperature of 1700 ° C. and a pressure of 20 MPa.
The relative density of the obtained aluminum oxide-tantalum carbide conductive composite sintered body was 98%.

(Preparation of support plate)
5 parts by weight of high-purity silicon carbide fine powder (average particle size 0.01 μm, manufactured by Sumitomo Osaka Cement Co., Ltd.) synthesized by vapor phase plasma CVD method and aluminum oxide powder (average particle size 0.2 μm, Daimei Chemical Industries) A mixed powder consisting of 95 parts by weight of Sumi Co., Ltd. was molded and fired to obtain a disk-shaped silicon carbide-aluminum oxide composite sintered body having a diameter of 230 mm and a thickness of 10 mm. It was the same as the terminal 6. Next, a fixing hole for incorporating and fixing the power feeding terminals 6 and 6 was formed in this silicon carbide-aluminum oxide composite sintered body by drilling with a diamond drill, A support plate 3 made of a silicon carbide-aluminum oxide composite sintered body was obtained.

(Production of mounting plate)
A disk-shaped silicon carbide-aluminum oxide composite sintered body having a diameter of 230 mm and a thickness of 5 mm was obtained in accordance with the production of the support plate 3 described above.

(Integrated)
The power supply terminals 6 and 6 were fitted and fixed in the fixing holes formed in the support plate 3. Next, a coating liquid in which a mixed powder composed of 40% by weight of aluminum oxide powder and 60% by weight of tantalum carbide powder is dispersed in ethanol in a region where the internal electrode for electrostatic adsorption on the support plate 3 is to be formed is screen-printed. It was applied by the method, and then dried to form an internal electrode forming layer for electrostatic adsorption.

Next, a coating solution containing aluminum oxide powder (average particle size 0.2 μm, manufactured by Daimei Chemical Industry Co., Ltd.) and ethanol in a region other than the region where the internal electrode for electrostatic adsorption on the support plate 3 is to be formed. Then, it was applied by a screen printing method and then dried to form an insulating material layer forming layer.
Next, the mounting plate 2 was superposed on the internal electrode forming layer for electrostatic attraction and the insulating material layer forming layer of the support plate 3, and then these were integrated by pressing and baking with a hot press. The conditions at this time were a temperature of 1750 ° C. and a pressure of 7.5 MPa.
Next, the mounting surface 2a of the integrated mounting plate 2 was mirror-polished by a lapping method to obtain a bipolar electrostatic chuck of the example.

The surface roughness Ra of the mounting surface 2a was measured using a phase shift interferometer GPI-XPHR manufactured by Zygo, and found to be 3 nm (0.003 μm).
The volume resistivity of the mounting plate 2 was measured at room temperature (25 ° C.) in accordance with Japanese Industrial Standard JIS C 2141 “Ceramic Material Test Method for Electrical Insulation” and found to be 1.0 × 10 ¹⁴ Ω · cm. Met.
Furthermore, when the average particle diameter of each of the aluminum oxide particles and the silicon carbide particles in the silicon carbide-aluminum oxide composite sintered body constituting the mounting plate 2 was measured by a scanning electron microscope (SEM) observation method, the aluminum oxide particles The average particle size of the silicon carbide particles was 1.5 μm, and the average particle size of the silicon carbide particles was 0.4 μm.

(Evaluation)
Using this electrostatic chuck, a 12-inch silicon wafer is electrostatically adsorbed in a vacuum (0.05 Pa) at room temperature (25 ° C.), and the silicon wafer is irradiated with an electron beam. When the electrostatic adsorption force, the electrostatic adsorption time, and the separation time were measured, they were 15.0 kPa, 3 seconds, and 1 second, respectively.
Here, the electrostatic adsorption time is a time until the electrostatic adsorption force becomes 15000 Pa (310 gf / cm ² ) when a DC voltage of 1000 V is applied between the power supply terminals 6 and 6. The separation time refers to the application of a DC voltage of 1000 V between the power feeding terminals 6 and 6 for 1 minute, then the application is stopped, and the electrostatic attraction force becomes 980 Pa (10 gf / cm ² ) from the time of the stop. It is time to become.

  Further, a DC voltage of 1000 V is applied between the power feeding terminals 6 and 6 by using this electrostatic chuck, and a 12-inch silicon wafer is subjected to vacuum (0.05 Pa) at room temperature (25 ° C.). Then, the silicon wafer was removed from the electrostatic chuck, and the number of particles adhering to the back surface of the silicon wafer was measured with a particle counter SP1 (manufactured by TENKOR). The results are shown in Table 1.

"Comparative Example 1"
An electrostatic chuck of Comparative Example 1 was obtained in the same manner as in Example except that unevenness was formed on the mounting plate 2 by sandblasting and the top surface of the convex portion was used as a mounting surface.
When the top surface of the convex portion was measured using a phase shift interferometer GPI-XPHR manufactured by Zygo, the surface roughness Ra was 20 nm (0.02 μm), the height of the convex portion was 25 μm, and the top surface of the convex portion was The area ratio of the total area to the electrostatic adsorption surface was 15%.

Further, when the electrostatic chucking force, electrostatic chucking time, and separation time of the electrostatic chuck were measured in accordance with the example without flowing the gas into the recess, the electrostatic chuck was almost the same as the electrostatic chuck of Example 1. Results were obtained.
Further, for this electrostatic chuck, the number of particles adhering to the back surface of the silicon wafer was measured according to Example 1. The results are shown in Table 1.

"Comparative Example 2"
An electrostatic chuck of Comparative Example 2 was obtained according to the example except that the mounting plate 2 and the support plate 3 were formed of an aluminum oxide sintered body.
When the volume resistivity of the mounting plate 2 at room temperature (25 ° C.) was measured according to the example, it was 1 × 10 ¹⁵ Ω · cm.

Further, when the electrostatic chucking force, electrostatic chucking time, and separation time of the electrostatic chuck were measured in accordance with the example without flowing the gas into the recess, the electrostatic chuck was almost the same as the electrostatic chuck of Example 1. Results were obtained.
Further, for this electrostatic chuck, the number of particles adhering to the back surface of the silicon wafer was measured according to Example 1. The results are shown in Table 1.

“Comparative Example 3”
Although the composition of the silicon carbide-aluminum oxide composite sintered body was changed to 35% by mass of silicon carbide and 65% by weight of aluminum oxide, an attempt was made to produce an electrostatic chuck of Comparative Example 3 according to the example. The surface could not be mirror polished.

“Comparative Example 4”
An electrostatic chuck of Comparative Example 4 was obtained according to the example except that the surface roughness Ra of the mounting surface 2a was 15 nm (0.015 μm).
When the electrostatic chucking force, electrostatic chucking time, and separation time of this electrostatic chuck were measured according to the example without flowing gas into the recess, the results were almost the same as those of the electrostatic chuck of Example 1. Obtained.
Further, for this electrostatic chuck, the number of particles adhering to the back surface of the silicon wafer was measured according to Example 1. The results are shown in Table 1.

  In the electrostatic chuck of the present invention, the substrate is formed of a flat silicon carbide-aluminum oxide composite sintered body containing silicon carbide in an amount of 1% by mass to 30% by mass, and the surface of the mounting surface is roughened. Since the Ra is 0.01 μm or less, the number of particles adhering to the back surface of the electrostatically adsorbed plate-like sample can be greatly reduced even when used during electron beam irradiation. The present invention can be applied to a plate-like sample holding member other than the electrostatic chuck, and its usefulness is very large.

It is a top view which shows the bipolar electrostatic chuck of one Embodiment of this invention. It is sectional drawing which follows the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrostatic chuck 2 Mounting plate 2a Mounting surface 3 Support plate 4 Electrostatic adsorption internal electrode 5 Insulating material layer 6 Power supply terminal 7 Substrate 8, 9 DC power supply

Claims (3)

An electrostatic chuck used during electron beam irradiation,
A main surface is used as a mounting surface on which a plate-like sample is mounted and an electrostatic adsorption internal electrode is provided inside, and a voltage is applied to the electrostatic adsorption internal electrode held by the substrate. Power supply terminal,
The base is formed of a flat silicon carbide-aluminum oxide composite sintered body containing silicon carbide in an amount of 1% by weight to 30% by weight,
The electrostatic chuck characterized in that the surface roughness Ra of the mounting surface is 0.01 μm or less.   The electrostatic chuck according to claim 1, wherein an average particle diameter of aluminum oxide particles in the silicon carbide-aluminum oxide composite sintered body is 5 μm or less.   3. The electrostatic chuck according to claim 1, wherein an average particle diameter of silicon carbide particles in the silicon carbide-aluminum oxide composite sintered body is 1 μm or less.

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