JP2007214339A - Bipolar electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bipolar electrostatic chuck capable of developing a required attracting force even when contaminant, such as moisture, organic matters or the like, is adhered to the surface of the electrostatic chuck serving as an attracting surface. <P>SOLUTION: The bipolar electrostatic chuck 1 is equipped with a base mount 4, a pair of positive and negative electrodes 2a, 2b formed on the upper surface of the base mount 4, and an insulating layer 3 formed on the base mount 4 so as to cover the electrodes 2a, 2b. In such a bipolar electrostatic chuck 1, a groove 6 whose depth from the surface of the insulating layer is larger than the depth of the position of the pair of positive and negative electrodes 2a, 2b, is formed so as to part between the pair of positive and negative electrodes 2a, 2b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a bipolar electrostatic chuck, and more particularly, to a bipolar electrostatic chuck that holds a silicon wafer or a liquid crystal substrate, which is an object to be attracted, in a semiconductor or liquid crystal manufacturing process.

For example, in various processing steps in a semiconductor manufacturing process and a liquid crystal manufacturing process, it is necessary to securely hold a silicon wafer or a liquid crystal substrate on a mounting table. As a holding device that meets these requirements, an electrostatic chuck device that attracts and holds a silicon wafer or a liquid crystal substrate, which is an object to be attracted, is widely used by utilizing electrostatic action, and as an electrostatic chuck mounted on the device. Has been proposed which comprises a base, an electrode formed on the upper surface of the base, and an insulating layer formed on the base so as to cover the electrode.

Electrostatic chucks are roughly classified into a monopolar electrostatic chuck having a single electrode and a bipolar electrostatic chuck having a pair of positive and negative electrodes, depending on the electrode configuration. Among these, bipolar electrostatic chucks do not need to ground the object to be attracted unlike single-pole electrostatic chucks, and can increase the product area, so that they are widely used in recent years. It has become like this. (For example, see Patent Document 1)
In addition, as the electrode structure of the bipolar electrostatic chuck, in addition to a pair of electrode layers facing each other, a pair of comb-shaped electrodes, an inner peripheral electrode and a ring-shaped electrode formed on the outer periphery, etc. Various things are used according to use conditions.
Japanese Patent Laid-Open No. 11-186371

Here, the bipolar electrostatic chuck according to the present invention has a pair of positive and negative electrodes inside, and is configured to exhibit an attractive force by a potential difference between the electrodes. That is, there is an insulating layer made of ceramics as a material of the electrostatic chuck between the electrodes, and a positive and negative potential difference is generated through this insulating layer. However, if contaminants such as moisture or organic matter adhere to the surface of the electrostatic chuck that becomes the adsorption surface, the insulation of the surface will be reduced, so that no potential is generated on the surface of the electrostatic chuck and the adsorption force will be reduced. was there.
As described above, in the bipolar electrostatic chuck in which the distance between the positive and negative electrodes is short, a state in which a potential difference does not easily occur even with a small amount of adhering matter occurs, which is a cause that the adsorption force cannot be expressed.
The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a bipolar electrostatic chuck that can exhibit an attracting force without being affected by contaminants on the surface.

The present inventors have intensively studied to solve the problems of the prior art as described above, and have completed the present invention. That is, an object of the present invention is to provide a bipolar electrostatic chuck that can exhibit a desired adsorption force even when contaminants such as moisture and organic matter adhere to the surface of the electrostatic chuck serving as an adsorption surface. There is.

  An object of the present invention described above includes a base, a pair of positive and negative electrodes formed on the upper surface of the base, and an insulating layer formed on the base so as to cover the electrodes. In such a bipolar electrostatic chuck, a groove portion whose depth from the surface of the insulating layer is larger than the depth at which the pair of positive and negative electrodes is located is divided between the pair of positive and negative electrodes. This is achieved by a bipolar electrostatic chuck characterized in that it is formed.

The object of the present invention is achieved by the bipolar electrostatic chuck described above, wherein the groove has a width of 5 mm or less.

According to the present invention, even if a contaminant such as moisture or organic matter adheres to the surface of the electrostatic chuck serving as an adsorption surface, a bipolar electrostatic chuck capable of expressing a desired adsorption force can be obtained. There is.

  In the present invention, a bipolar circuit comprising a base, a pair of positive and negative electrodes formed on the upper surface of the base, and an insulating layer formed on the base so as to cover the electrodes. In the type electrostatic chuck, a groove portion whose depth from the surface of the insulating layer is larger than the depth at which the pair of positive and negative electrodes is located is formed so as to divide the pair of positive and negative electrodes. A bipolar electrostatic chuck characterized by the above is proposed.

Here, a schematic sectional view of the bipolar electrostatic chuck according to the embodiment of the present invention is shown in FIG. 1, and a plan view thereof is shown in FIG.
The bipolar electrostatic chuck 1 of the present invention covers a base 4, a pair of positive and negative electrodes (2 a, 2 b) formed on the upper surface of the base 4 and connected to a power source 5, and the electrodes. And an insulating layer 3 formed on the base 4. In the bipolar electrostatic chuck of the present invention, the groove 6 having a depth from the surface of the insulating layer larger than the depth at which the pair of positive and negative electrodes is located is divided between the pair of positive and negative electrodes. Forming.

Next, a schematic plan view of a bipolar electrostatic chuck according to another embodiment of the present invention is shown in FIG. As the electrode structure of the bipolar electrostatic chuck according to the present invention, a pair of positive and negative electrodes, as shown in FIG. 3, is used as an inner peripheral electrode 2a and a ring outer peripheral electrode. The groove portion 6 (schematically shown by a thick solid line in the drawing) may be formed so as to divide between a pair of positive and negative electrodes.
FIG. 4 shows a schematic plan view of a bipolar electrostatic chuck according to another embodiment of the present invention. As shown in FIG. 4, a pair of positive and negative comb-shaped electrodes (2a, 2b) is formed, and the groove 6 (shown schematically by a thick solid line in the drawing) is formed between the pair of positive and negative comb-shaped electrodes. You may form so that a space | interval may be parted.

Here, the material constituting the base of the electrostatic chuck and the insulating layer is preferably the same kind of ceramic material mainly composed of one kind of material selected from AlN, Al ₂ O ₃ , and Si ₃ N ₄ . The reason for this is that ceramic members made of these materials have excellent physical and chemical properties, so that electrostatic chucks that require mechanical strength, corrosion resistance, etc., such as semiconductor manufacturing equipment and liquid crystal manufacturing equipment. It is because it is suitable as a material.

Since an electrostatic chuck applies a high voltage to adsorb an object to be adsorbed such as a Si wafer by Coulomb force or Johnson Rahbek force, as described above, moisture is adsorbed on the surface of the electrostatic chuck serving as an adsorbing surface. A state in which a contaminant such as organic substances or the like adheres and no potential difference occurs on the adsorption surface is not preferable.

Therefore, in the present invention, a groove portion is formed on the surface of the bipolar electrostatic chuck, and the insulating layer between the electrodes is physically divided so that the adsorption force can be expressed regardless of what is attached to the surface. It is. That is, according to the present invention, even if contaminants such as moisture and organic matter adhere to the surface of the electrostatic chuck, the contaminants are divided at the groove portion, so that the surface insulation is not lowered, and the adsorption power There is an effect that the problem that it becomes impossible to develop will not occur.

Here, in order to make the influence of contaminants on the adsorption force of the bipolar electrostatic chuck small so as to be negligible, the depth from the surface of the insulating layer is larger than the depth at which the pair of positive and negative electrodes are located. Is preferably formed so that the gap between the pair of positive and negative electrodes is divided. This is because if the depth of the groove is shallower than the position of the electrode, the adsorption force cannot be sufficiently exerted due to the influence of adhesion of contaminants on the adsorption surface.
Here, it is particularly preferable that the depth of the groove is greater than the depth at which the electrode is located and is further 0.1 to 3.0 mm greater than the lower surface of the electrode. The reason is that if it is less than 0.1 mm, the adsorption force is affected by the adhesion of contaminants, and if it exceeds 3.0 mm, the mechanical strength of the base is reduced, which is not preferable.

Next, the present invention proposes the bipolar electrostatic chuck described above, wherein the groove has a width of 5 mm or less.
Here, the reason why the width of the groove is preferably 5 mm or less is that, if the width of the groove is larger than 5 mm, the flow is performed for the purpose of uniformizing the heat distribution of the object to be adsorbed on the electrostatic chuck. This is because the gas stays in the groove and the heat distribution of the object to be adsorbed becomes uneven, which is not preferable.
Moreover, since the influence of a deposit | attachment cannot be excluded if the width | variety of a groove part is less than 0.5 mm, it is preferable that the width | variety of a groove part is 0.5-5 mm.

EXAMPLES Hereinafter, the Example of this invention is specifically given with a comparative example, and this invention is demonstrated in detail.
Example 1
(1) Manufacture of bipolar electrostatic chuck A mixed powder obtained by adding a sintering aid of a rare earth oxide to a commercially available AlN powder is uniaxially pressed at 100 kg / cm ² (= 9.8 MPa), and φ200 mm × 10 mm A disk-shaped molded body was prepared. (After sintering, it corresponds to the base of the present invention.)
Next, a pair of inner peripheral electrodes and a ring-shaped outer peripheral electrode (see FIG. 3) having a thickness of 0.1 mm are arranged on the molded body, and the mixed powder is filled thereon (after sintering). And corresponds to the insulating layer of the present invention.) After that, by performing hot press sintering under conditions of firing temperature: 1900 ° C., firing time: 2 hours, press pressure: 100 kg / cm ² , a disk shape of φ200 mm × 15 mm An electrostatic chuck member made of the above ceramics was obtained.
Next, the obtained electrostatic chuck member is ground so that the insulating layer (layer formed by the mixed powder filled on the electrode) has a thickness of 1 mm, and holes are formed at two locations on the opposite surface. A terminal for applying voltage to a pair of positive and negative electrodes was attached.
Thereafter, the width is 2 mm so that the pair of positive and negative electrodes are divided, the depth from the insulating layer surface (adsorption surface) is larger than the depth at which the pair of positive and negative electrodes are located, A groove portion that is 1 mm deeper than the lower surface portion was processed by a machining center (a schematic configuration cross-sectional view of the groove portion of the example is shown in FIG. 5) to obtain a bipolar electrostatic chuck that is an example of the present invention.
(2) Measurement of adsorption force Next, with respect to the obtained bipolar electrostatic chuck, a DC voltage up to 3 KV was applied to evaluate the withstand voltage and the adsorption force. For the evaluation of the adsorption force, the Si wafer was placed on the adsorption surface of the electrostatic chuck and adsorbed, the Si wafer was pulled with a force gauge, and the force when the Si wafer was peeled off from the adsorption surface was measured as the adsorption force.
As a result, the withstand voltage was sufficiently large so that there was no problem in practical use, and the adsorption force was as large as 483 g.
(3) Moisture adhesion test on the surface Next, the bipolar electrostatic chuck obtained in the example was allowed to stand in a high-humidity tank having a humidity of 90% for 4 hours to sufficiently adhere moisture to the surface of the electrostatic chuck. It was. Then, as a result of measuring the said adsorption power, the adsorption power became 503g. As described above, the attracting force of the bipolar electrostatic chuck according to the embodiment of the present invention was almost the same as that before the standing even when the moisture adhered to the surface after leaving in the high-humidity tank.

(Example 2)
(1) Manufacture of bipolar electrostatic chuck A pair of positive and negative electrodes is separated from an electrostatic chuck manufactured by the same method as in Example 1 except that the electrode has a comb-like shape (see FIG. 4). As shown in the figure, a groove having a width of 2 mm, the depth from the surface of the insulating layer is larger than the depth at which the pair of positive and negative electrodes are located, and a groove portion that is 1 mm deeper than the lower surface of the electrode is processed by a machining center A bipolar electrostatic chuck as an example of the invention was obtained.
(2) Measurement of adsorption force Next, with respect to the obtained bipolar electrostatic chuck, a DC voltage up to 3 KV was applied to evaluate the withstand voltage and the adsorption force. For the evaluation of the adsorption force, the Si wafer was placed on the adsorption surface of the electrostatic chuck and adsorbed, the Si wafer was pulled with a force gauge, and the force when the Si wafer was peeled off from the adsorption surface was measured as the adsorption force.
As a result, the withstand voltage was sufficiently large so that there was no problem in practical use, and the adsorption force was as large as 658 g.
(3) Moisture adhesion test on surface Next, the obtained bipolar electrostatic chuck was left in a high-humidity tank having a humidity of 90% for 4 hours to sufficiently adhere moisture to the surface of the electrostatic chuck. Then, as a result of measuring the above-mentioned adsorption force, the adsorption force was 631 g, which was almost the same as that before leaving even when the moisture adhered to the surface after leaving in a high-humidity tank.

(Comparative example)
The depth of the groove from the surface of the insulating layer (adsorption surface) is smaller than the depth at which the pair of positive and negative electrodes are located and is shallower by 0.5 mm than the lower surface of the electrode (see FIG. A bipolar electrostatic chuck was produced in the same manner as in Example 1 except that the schematic configuration sectional view was shown), and the adsorption force was measured.

Next, in the same manner as in the example, it was left in a high-humidity tank having a humidity of 90% for 4 hours, and the adsorption force was measured in a state where moisture sufficiently adhered to the surface.
As a result, the adsorption power before leaving the high-humidity tank was 462 g, which was as large as that of the example, but the adsorption power after leaving the high-humidity tank was 130 g, which was less than half that before leaving the high-humidity tank. .

As described above, as in the present invention, by forming the groove so that the electrodes of the bipolar electrostatic chuck are divided, the influence of contaminants on the adsorption surface of the bipolar electrostatic chuck is not affected. It was confirmed that a bipolar electrostatic chuck capable of expressing a stable attracting force could be provided.

1 is a schematic cross-sectional view of a bipolar electrostatic chuck according to an embodiment of the present invention. 1 is a schematic plan view of a bipolar electrostatic chuck according to an embodiment of the present invention. 1 is a schematic plan view of a bipolar electrostatic chuck according to an embodiment of the present invention. 1 is a schematic plan view of a bipolar electrostatic chuck according to an embodiment of the present invention. It is schematic structure sectional drawing of the groove part which concerns on an Example. It is schematic structure sectional drawing of the groove part which concerns on a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Electrostatic chuck | zipper 2a, 2b; Electrode 3; Insulating layer 4; Base 5; Power supply 6;

Claims (2)

Bipolar electrostatic chuck comprising a base, a pair of positive and negative electrodes formed on the upper surface of the base, and an insulating layer formed on the base so as to cover the electrodes The groove portion is formed so that the depth from the surface of the insulating layer is larger than the depth at which the pair of positive and negative electrodes is located so that the gap between the pair of positive and negative electrodes is divided. Bipolar electrostatic chuck. 2. The bipolar electrostatic chuck according to claim 1, wherein the width of the groove is 5 mm or less.

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