JP2005209755A - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck which does not cause breakdown when sucking an article of a simple insulating material, or of an insulating material that has a condcutor inside or on a surface opposite to a surface to be sucked, or of an article having a condcutive surface to be sucked. <P>SOLUTION: The electrostatic chuck comprises a dielectric 2 on whose one surface a plurality of irregularities are formed, electrodes 3a, 3b which are formed on bottoms of recessions of the dielectric 2, and an insulating material 4 which coats the recessions of the dielectric 2 to cover the electrodes 3a, 3b. It is desirable that the electrostatic chuck has a sucking surface which is the surface of the dielectric 2 that is opposite to the surface having irregularities. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrostatic chuck used in semiconductor and liquid crystal fields such as a semiconductor device manufacturing apparatus and a liquid crystal device manufacturing apparatus.

  When manufacturing semiconductor devices, liquid crystal devices, and the like, electrostatic chucks capable of surface adsorption from the conventional mechanical clamp method are being studied to hold silicon wafers, glass substrates, and the like, particularly in a vacuum atmosphere.

As the structure of the electrostatic chuck, for example, as described in Patent Document 1, a structure in which a plastic dielectric material is bonded on an insulator layer in which an electrode is embedded is known.
In addition, as described in Patent Documents 2, 3, and 4, there is known one in which an electrode is provided between two insulating ceramic plates.
Further, as described in Patent Document 5, an electrode in which an electrode on an insulating ceramic plate is coated with an insulating ceramic by a thermal spraying method is known.

Japanese Patent Laid-Open No. 53-077489 (page 1-3, FIG. 1) JP 63-095644 (page 3-4, Fig. 1) JP-A-4-206545 (page 1-5, FIGS. 1 and 2) Japanese Patent Laid-Open No. 5-036819 (page 1-5, FIG. 1) JP 59-152636 A (page 1-4, FIG. 3)

The electrostatic chuck is composed of a dielectric, an electrode, and, if necessary, a dielectric and a supporting base that supports the electrode. In the structure of a conventional bipolar electrostatic chuck, an electrode and an electrode are disposed between adjacent electrodes. There is an interface that connects the two at a shortest distance. For example, as described in Patent Documents 6 and 7, an electrostatic chuck using integral firing by a green sheet method has an interface when the green sheets are overlapped. In general, the withstand voltage at the interface is smaller than that of a single individual.
On the other hand, in order to attract an insulator such as glass with an electrostatic chuck, it is necessary to apply a voltage of ± 3 kV to ± 10 kV as described in Patent Document 8.

JP-A-5-013555 (page 1-3) Japanese Patent Laid-Open No. 5-304201 (page 1-4) JP 2000-332091 A (page 4-6)

  However, when the voltage shown above is applied, the conventional electrostatic chuck shown above has a problem that dielectric breakdown tends to occur at the interface existing between the electrodes. For this reason, the present situation is that an electrostatic chuck having a structure with higher withstand voltage is desired.

  In the present invention, an object to be adsorbed adsorbs an object to be adsorbed simply by an insulator, an insulator in which a conductor is formed inside or on the surface opposite to the surface to be adsorbed, or an adsorbed surface. However, an electrostatic chuck that does not cause dielectric breakdown is provided.

The present invention relates to a dielectric having a plurality of concave and convex shapes formed on one surface, an electrode formed on a bottom surface of a concave portion of the dielectric, and an electrostatic chuck made of an insulator covering the concave portion of the dielectric so as to cover the electrode.
The present invention also relates to an electrostatic chuck having a suction surface on the opposite side surface of the irregular shape of the dielectric.
The present invention also relates to an electrostatic chuck whose dielectric is a ceramic sintered body.

The present invention also relates to an electrostatic chuck in which the ceramic sintered body is alumina ceramic.
The present invention also relates to an electrostatic chuck in which the electrode is a conductive metal and the insulator is an epoxy resin.
The present invention also relates to an electrostatic chuck in which electrodes are divided into two groups, and a potential difference is applied between each group to electrostatically attract an object to be attracted.

  In the electrostatic chuck according to the present invention, an object to be adsorbed is a simple insulator, an insulator in which a conductor is formed inside or opposite to the surface to be adsorbed, or an adsorbed surface having conductivity. Even if an object is adsorbed, dielectric breakdown does not occur, and its reliability can be significantly improved compared to conventional electrostatic chucks, so it is used in the semiconductor and liquid crystal fields such as semiconductor device manufacturing equipment and liquid crystal device manufacturing equipment. It is suitable as an electrostatic chuck.

Hereinafter, the principle of the electrostatic chuck according to the present invention will be specifically described.
In general, an insulator does not have free electrons that can be moved by an electric field therein, and thus is electrically insulative. However, since an electric dipole is induced by the electric field, the insulator is also called a dielectric.
In many cases, the dielectric is composed of countless minute dielectric particles. When one of the dielectric particles is considered, the same number of positive and negative charges are contained in the dielectric particles, and the electrical neutrality is maintained.

When this dielectric particle is placed in an electric field, dielectric polarization occurs according to the strength of the electric field, and the amount of polarization charge at this time is equal in both positive and negative directions. When the electric field on which the dielectric particles are placed is an equal electric field, the forces acting on the positive and negative polarization charges cancel each other, and no force acts on the dielectric particles.
On the other hand, when the electric field on which the dielectric particles are placed is an unequal electric field, the forces acting on the positive and negative polarization charges do not cancel each other, and a force directed toward the stronger electric field acts on the dielectric particles. The direction of this force is a force that always goes in the direction of a strong electric field, and is generally called an electric field gradient force.
When the dielectric or dielectric crystal, which is an aggregate of dielectric particles, is placed in an unequal electric field, the above-described electric field gradient force exerts a force toward the direction in which the electric field is strong.

When the insulator is attracted by the electrostatic chuck, the electric field gradient force described above is used. In order to obtain a large adsorption force, it is necessary to increase the electric field gradient force, that is, to increase the electric field gradient formed in the object to be adsorbed. Examples of such means include reducing the distance between adjacent electrodes and electrodes, increasing the potential difference applied between the electrodes and electrodes, and decreasing the distance between the electrodes and the adsorption surface (distance between the electrodes and the object to be adsorbed).

  However, when the electrode-electrode distance is reduced and the potential difference is increased, there is a risk of causing dielectric breakdown between the electrodes. The electrostatic chuck according to the present invention is composed of a single solid dielectric having a plurality of concave and convex shapes in the vicinity where adjacent electrodes are connected at the shortest distance. To prevent it from happening. In addition, an interface exists between a dielectric having a plurality of concavo-convex shapes and an insulator covering the recess, but there is no interface in the vicinity connecting the electrodes to each other with the shortest distance. Therefore, the electrostatic chuck obtained by the present invention has a high withstand voltage and prevents dielectric breakdown from occurring between the electrodes.

  For this reason, the electrostatic chuck according to the present invention drastically improves the reliability against dielectric breakdown as long as the potential difference applied between the electrodes during adsorption is the same. In addition, since a larger potential difference can be given between the adjacent electrodes-electrodes than the electrostatic chuck having the conventional structure, a larger attracting force than the electrostatic chuck having the conventional structure can be obtained.

  When the electrostatic chuck according to the present invention attracts an object to be attracted having conductivity to the surface to be attracted, the Coulomb force is used. Coulomb force is generally known as a force acting between charges. When the signs of two charges are different signs, they attract each other (suction force), and when they have the same sign, retreat forces (repulsive force, repulsive force) Become. Also, the magnitude of the Coulomb force is proportional to the product of both charge amounts and inversely proportional to the square of the distance between the two charges.

  Further, when the surface to be adsorbed by the electrostatic chuck according to the present invention adsorbs an object to be adsorbed with conductivity, the electrically conductive portion of the conductor on the adsorption surface of the object to be adsorbed is used. As long as it can be adsorbed by an electrode having a different polarity, there is no restriction that a potential of a different polarity must be applied to an adjacent electrode.

  At this time, it is desirable that the ratio of the electrode areas of the polarities of the electrodes that adsorb the object to be adsorbed whose surface to be adsorbed is substantially equal. This is because, when the area of the electrode of polarity 1 among the electrodes is a and the area of the electrode of polarity 2 is b, b = 1−a, and the attractive force is proportional to the product of a and b. That is, if the other conditions are constant, the adsorption force is maximized when the areas of the polar 1 and polar 2 electrodes are equal.

  This is not the case when the conductive portion of the object to be attracted, whose surface to be attracted has conductivity, is electrically connected to a charge supply source (such as ground) other than the electrostatic chuck. That is, it does not depend on the ratio of the polar 1 and polar 2 electrode areas. Further, even if the charges applied to the electrodes are all the same polarity, they can be adsorbed.

  In general, when the applied voltage to the electrostatic chuck is the same, the attracting force to the attracted object is that the attracted surface has conductivity, and the insulation is formed on the insulator and the conductor on the surface opposite to the attracted surface. Greater than the body's adsorption power. Therefore, the potential difference necessary to obtain the same level of adsorption force is greater than that in the case where the object to be adsorbed is an insulator and an insulator in which a conductor is formed inside or opposite to the surface to be adsorbed. It is possible to reduce the size when the surface to which the material is adsorbed is a conductive adsorbent. For this reason, since the electrostatic chuck is less likely to cause dielectric breakdown when the attracted surface attracts an object to be adsorbed with conductivity, the surface attracted by the electrostatic chuck according to the present invention is not electrically conductive. There is no problem with adsorbing the adsorbate to be adsorbed.

  When the electrostatic chuck according to the present invention attracts an insulator having a conductor formed inside or on the surface opposite to the surface to be attracted, the attracting force is obtained by both the electric field gradient force and the Coulomb force. be able to. That is, it is attracted by the electric field gradient force to the insulator portion and by the Coulomb force to the conductor portion. However, the working ratio of the electric field gradient force and the Coulomb force, that is, which is dominant, depends on the physical properties and structure of the object to be adsorbed, the electrode-electrode distance of the electrostatic chuck, and the electrode-adsorption surface distance.

Hereinafter, materials and configurations used for the electrostatic chuck according to the present invention will be described.
As a dielectric material that forms a plurality of concave and convex shapes on one surface, ceramic materials such as alumina, silicon nitride, aluminum nitride, zirconia, cordierite, and glass are used. In view of the above, it is preferable to use alumina ceramics.

  The concavo-convex shape formed on the dielectric can be formed on the flat plate by mechanical processing such as grooving by a grinder, GMC processing, or blast processing. It can also be formed by mold molding, injection molding, pressure molding or the like. Furthermore, when ceramics are used for the dielectric, a ceramic dielectric having a plurality of concave and convex shapes can be obtained by forming a concave and convex shape at the stage of the molded body and firing the molded body. For the ceramic molded plate before firing, the ceramic molded body may be obtained by forming a concavo-convex shape by mechanical processing such as groove processing, GMC processing, and blast processing by a grinding machine.

  The electrode formed on the bottom surface of the concave portion of the dielectric is formed, for example, by closely attaching a metal plate or foil such as aluminum, copper, or stainless steel. Alternatively, a paste made of a metal such as silver or gold and glass may be baked.

  As an insulator that covers the surface of the electrode formed on the bottom surface of the concave portion of the dielectric and covers the concave portion of the dielectric, it has excellent insulation performance and excellent adhesion to the dielectric formed with a plurality of concave and convex shapes. It is desirable. For example, it is preferable to fill with an epoxy resin. Moreover, it can also coat | cover by fitting another insulator, for example, an insulating ceramic sintered compact, or fixing with an insulating adhesive agent.

  The electrode formed on the bottom surface of the concave portion of the dielectric is connected to the voltage generator through a conductor plate, a conductor wire, a disconnect switch, a control circuit, and the like. The potential applied to each electrode may be changed by controlling the wiring method and applied voltage.

  The attracting surface is preferably a surface opposite to the concave-convex shape of the dielectric, and the attracting surface is preferably processed into a flat surface by surface grinding or the like. Adsorbed objects are adsorbed at atmospheric pressure (high pressure), and when the atmosphere continuously changes to a vacuum (low pressure) state while adsorbed objects are adsorbed, or the adsorbed objects are in a vacuum (low pressure) state. When the atmosphere is continuously changed to the atmospheric pressure (high pressure) state while adsorbing the adsorbed object, the gas existing between the adsorbing surface and the adsorbed object can easily move, It is preferable to groove the suction surface.

Hereinafter, an example of the electrostatic chuck structure of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing a cross section of an electrostatic chuck according to an embodiment of the present invention and a power feeding circuit portion for supplying electric charges to the electrostatic chuck.
An electrostatic chuck 1 shown in FIG. 1 includes a dielectric 2 having a plurality of concave and convex shapes formed on one surface, electrodes 3a and 3b formed on the bottom surface of the concave portion of the dielectric 2, and a dielectric so as to cover the electrodes 3a and 3b. The concave portion 2 is covered with an insulator 4, and the opposite side surface of the dielectric 2 to the concave-convex shape is an adsorption surface 5. In FIG. 1, reference numeral 9 denotes an insulating base material fixed with an insulating adhesive 10 in order to give the electrostatic chuck 1 strength.
Further, the electrodes 3a and 3b formed on the electrostatic chuck 1 have the opposite electrodes 3a and 3b having different polarities from the voltage generator 7 through the disconnect switch 8a, the wiring portion 8b, and the power supply wirings 6a and 6b. In this way, a power feeding unit 11 that supplies electric charges is connected.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to this.
Example 1
As shown in FIG. 1, alumina ceramics (trade name: Halox, manufactured by Hitachi Chemical Co., Ltd.) having a volume resistivity of 10 ¹⁴ Ωm and dimensions of 80 mm × 80 mm × thickness 4 mm are prepared as dielectric 2 On one surface of the alumina ceramic, recesses having a width of 1 mm and a depth of 2 mm were formed at intervals of 1 mm by grooving with a surface grinder, and then an aluminum plate was attached to the bottom surface of the recess to form electrodes 3a and 3b.

  Next, power supply wirings 6a and 6b are connected to the electrodes 3a and 3b so that the polarities are alternated, and then an insulating epoxy resin (trade name WZ-made by Hitachi Chemical Co., Ltd.) is used as the insulator 4 in the recess. 9043) is injected to cover the electrodes 3a and 3b and the entire surface of the recess is coated, and then the insulating epoxy resin is cured, and then the insulation used above on the surface of the cured insulating epoxy resin to give strength. Alumina ceramics were fixed as the base material 9 using the conductive epoxy resin 10, and the suction surface 5 was ground by surface grinding to obtain an electrostatic chuck.

Comparative Example 1
As shown in FIG. 2, an insulating epoxy resin similar to that of Example 1 is applied to the exposed surfaces of the electrodes 3a and 3b and the lower exposed surface of the dielectric 2 without forming an uneven shape on the dielectric 2, and cured. Thereafter, an electrostatic chuck was obtained through the same steps as in Example 1 except that the base material 9 was fixed to the surface using the same insulating adhesive as in Example 1.

  Next, the electrostatic chuck obtained in Example 1 and Comparative Example 1 is given a potential difference from the voltage generator 7 to the electrodes 3a and 3b via the power supply wirings 6a and 6b, the disconnection switch 8a, and the wiring part 8b, and the electrode 3a. And the dielectric breakdown potential difference between 3b was measured. The results are shown in Table 1. In addition, this measurement was performed in air | atmosphere and a vacuum (1 Pa), and the potential difference given was 20 kV at maximum.

  As shown in Table 1, the electrostatic chuck according to the present invention did not cause dielectric breakdown even when a potential difference of 20 kV was applied, whereas the electrostatic chuck of the comparative example had dielectric 2, insulator 4 and At the interface, dielectric breakdown occurred at 12 kV in the atmosphere and 11 kV in vacuum (1 Pa). From this, it is clear that the electrostatic chuck according to the present invention has a higher dielectric breakdown potential difference that causes dielectric breakdown than the electrostatic chuck of the comparative example, that is, a higher withstand voltage.

It is the schematic which shows the cross section of the electrostatic chuck which becomes an Example of this invention, and the electric power feeding circuit part for supplying an electric charge to this electrostatic chuck. It is the schematic which shows the cross section of the electrostatic chuck of a comparative example, and the electric power feeding circuit part for supplying an electric charge to this electrostatic chuck.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrostatic chuck 2 Dielectric material 3a, 3b Electrode 4 Insulator 5 Adsorption surface 6a, 6b Power supply wiring 7 Voltage generator 8a Disconnect switch 8b Wiring part 9 Base material 10 Insulating adhesive 11 Power supply part

Claims (6)

  An electrostatic chuck comprising a dielectric having a plurality of concave and convex shapes on one surface, an electrode formed on a bottom surface of a concave portion of the dielectric, and an insulator covering the concave portion of the dielectric so as to cover the electrode.   The electrostatic chuck according to claim 1, wherein a side surface opposite to the uneven shape of the dielectric is an adsorption surface.   The electrostatic chuck according to claim 1, wherein the dielectric is a ceramic sintered body.   The electrostatic chuck according to claim 3, wherein the ceramic sintered body is alumina ceramic.   The electrostatic chuck according to claim 1, wherein the electrode is a conductive metal and the insulator is an epoxy resin. The electrostatic chuck according to claim 1, wherein the electrode is divided into two groups, and an object to be adsorbed is electrostatically adsorbed by applying a potential difference between each group.

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