JP2007207959A - Member for electrostatic chuck and method for adjusting its surface resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a member for an electrostatic chuck and a method for adjusting the surface resistance of the member adjusting the surface resistance by a simple method that does not cause contamination to a member for the electrostatic chuck. <P>SOLUTION: The member for the electrostatic chuck has a base, an electrode layer formed on the top face of the base, and an upper insulating layer formed on the base so as to coat the electrode layer. In the member of the electrostatic chuck, the base, and the upper insulating layer are composed of ceramic materials of the same kind mainly comprising one kind of a material selected from AlN, Al<SB>2</SB>O<SB>3</SB>and Si<SB>3</SB>N<SB>4</SB>. In the member, the surface resistance at a normal temperature of a contact surface with a substance attracted in the upper insulating layer is adjusted previously before shipment so as to reach 1.0×10<SP>14</SP>to 1.5×10<SP>16</SP>Ω/sq. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an electrostatic chuck member and a method for adjusting the surface resistance thereof, and more particularly to an electrostatic chuck member for attracting and holding a silicon wafer or a liquid crystal substrate as an object to be adsorbed in a semiconductor or liquid crystal manufacturing process, and the surface thereof. The present invention relates to a resistance adjustment method.

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. Electrostatic chuck devices that attract and hold silicon wafers and liquid crystal substrates, which are objects to be attracted, are widely used as holding devices that meet these requirements, and are used for electrostatic chucks mounted on such devices. As the member, a member comprising a base, an electrode layer formed on the upper surface of the base, and an upper insulating layer formed on the base so as to cover the electrode layer is proposed. Has been.

Here, in recent years, adjustment of the surface resistance of the electrostatic chuck member mounted on the electrostatic chuck device has become an important issue in order to ensure the holding of the attracted object. The reason is that in the case of a member to which a high voltage is applied, such as an electrostatic chuck, the value of the voltage that can be applied is limited depending on the surface resistance. That is, if the surface resistance of the electrostatic chuck member has a small surface resistance, it is not preferable to obtain a sufficient attracting force due to the leak current, which exceeds the allowable power of the electrostatic chuck device. This is because if the surface resistance of the chuck member is too large, a sufficient suction force cannot be obtained.

The thing which gives a deep relation to the surface resistance of such a member for electrostatic chuck is the moisture adsorbed on the surface, and when there is a lot of moisture adsorbed on the surface, the surface resistance becomes small, and conversely, It is known that the surface resistance increases when the adsorbed moisture is small. Therefore, it is important to adjust the surface resistance of the electrostatic chuck member.

Conventionally, as a surface treatment method for controlling the amount of moisture adsorbed on the surface of a member, (1) a method of chemically treating the surface of a member with an inorganic substance such as a silane compound and a polymer organic substance (for example, see Patent Document 1) (2) A method in which the surface of the member is physically treated by sputtering, discharge, plasma, or the like (for example, see Patent Document 2) is performed.
Japanese Patent Laid-Open No. 10-180937 JP 7-118857 A

  However, the method of chemically treating the surface of the member with an inorganic material such as a silane compound and a polymer organic material is limited in application because the use temperature is limited depending on the material used for the chemical treatment. There is a problem. Furthermore, since the foreign substance is treated on the surface of the member, the foreign substance itself may become a contamination source, which has been a problem in the process.

In addition, the method of physically treating the surface of the member such as sputtering, discharge, or plasma has a problem that the surface is roughened by the member and a desired surface roughness cannot be controlled.
Furthermore, since the processing apparatus is expensive, there are problems that the processing cost is high and the processing procedure is complicated.

  Accordingly, an object of the present invention is to solve such a problem, and an electrostatic chuck member having a surface resistance adjusted by a method that is simple and does not contaminate the electrostatic chuck member. The object is to provide a method for adjusting the surface resistance.

The object of the present invention described above includes a base, an electrode layer formed on the upper surface of the base, and an upper insulating layer formed on the base so as to cover the electrode layer. A member for an electrostatic chuck, wherein the base and the upper insulating layer are made of the same kind of ceramic material whose main component is a material selected from AlN, Al ₂ O ₃ , and Si ₃ N ₄ , and The surface resistance of the contact surface of the upper insulating layer with the object to be adsorbed is adjusted in advance so that the surface resistance at room temperature is 1.0 × 10 ^{14 to} 1.5 × 10 ¹⁶ Ω / □ in advance. This is achieved by the featured electrostatic chuck member.

Another object of the present invention is to polish the surface roughness Ra of the contact surface of the upper insulating layer of the electrostatic chuck member with the object to be adsorbed to 0.5 μm or less, and the electrostatic chuck member. The step of heat treating at 400 to 900 ° C., the step of immersing the electrostatic chuck member in alcohol, and the step of drying the ceramic member at 100 ° C. or more include the static This is achieved by a method for adjusting the surface resistance of the electric chuck member.

ADVANTAGE OF THE INVENTION According to this invention, the member for electrostatic chucks which adjusted surface resistance by the method which is simple and does not contaminate the member for electrostatic chucks, and the adjustment method of the surface resistance can be provided.

In the present invention, an electrostatic chuck comprising a base, an electrode layer formed on the upper surface of the base, and an upper insulating layer formed on the base so as to cover the electrode layer A member for use in which the base and the upper insulating layer are made of 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 , and the upper insulating layer The surface resistance of the contact surface with the object to be adsorbed at room temperature is adjusted in advance so as to be 1.0 × 10 ^{14 to} 1.5 × 10 ¹⁶ Ω / □ before shipping. Proposal of electric chuck members.

Here, the reason why the base of the electrostatic chuck member and the upper insulating layer are made of the same kind of ceramic material whose main component is a kind of material selected from AlN, Al ₂ O ₃ and Si ₃ N ₄ is that Ceramic members made of materials are excellent in physical and chemical properties, and are suitable as ceramics for electrostatic chuck members that require mechanical strength, corrosion resistance, etc., such as semiconductor manufacturing equipment and liquid crystal manufacturing equipment. Because.
The reason why the base and the upper insulating layer are made of the same kind of ceramic material is to prevent cracking and peeling of the upper insulating layer due to a difference in thermal expansion during sintering.
Furthermore, the sintered density of the ceramic of the electrostatic chuck member is desirably 98% or more. The reason is that if the sintered density is lower than 98%, the surface pores increase, and a large amount of moisture remains in the pores, so that the surface resistance cannot be increased so as to be suitable as an electrostatic chuck member. It is.

Next, the reason why the surface resistance of the contact surface of the upper insulating layer with the object to be adsorbed at room temperature is adjusted to 1.0 × 10 ^{14 to} 1.5 × 10 ¹⁶ Ω / □ in advance is as follows. If the surface resistance is less than 1.0 × 10 ¹⁴ Ω / □, an attempt to obtain a sufficient attracting force due to the generated leakage current will exceed the allowable power of the electrostatic chuck device. This is because if it exceeds 1.5 × 10 ¹⁶ Ω / □, a sufficient attracting force cannot be obtained as an electrostatic chuck, which is not preferable.

Further, it is preferable that the adjustment of the surface resistance is adjusted in advance at a stage close to the final process before shipment of the electrostatic chuck member. The reason for this is that even if the surface resistance is adjusted to a desired value at the initial stage, the surface resistance once adjusted is changed from the desired value due to the processing in each manufacturing process of the electrostatic chuck member. Because there are cases.

In the present invention, the step of polishing the surface roughness Ra of the contact surface of the upper insulating layer of the electrostatic chuck member with the object to be adsorbed to 0.5 μm or less, and the electrostatic chuck member at 400 to 900 ° C. The electrostatic chuck member comprising: a step of performing a heat treatment at a step; a step of immersing the electrostatic chuck member in alcohol; and a step of drying the ceramic member at 100 ° C. or higher. A method for adjusting the surface resistance is proposed.

Here, the reason for polishing the surface roughness Ra of the contact surface of the upper insulating layer of the electrostatic chuck member with the object to be adsorbed to 0.5 μm or less in the present invention is the surface roughness Ra of the electrostatic chuck member. This is because if the thickness exceeds 0.5 μm, the roughness of the surface becomes rough, and the adsorbed moisture cannot be controlled by the adjustment method of the present invention. Therefore, it is not preferable because the surface resistance of the electrostatic chuck member cannot be accurately adjusted.

In the present invention, the reason for heat-treating the electrostatic chuck member at 400 to 900 ° C. is to remove the adsorbed water on the surface of the electrostatic chuck member. Here, if it is less than 400 ° C., the adsorbed water cannot be sufficiently removed, and heat treatment exceeding 900 ° C. is not preferable because the surface of the electrostatic chuck member deteriorates.
Next, in this invention, the process of immersing the member for electrostatic chucks in alcohol and the process of drying the member for electrostatic chucks at 100 degreeC or more are included. The reason is that the surface resistance at room temperature of the contact surface of the upper insulating layer with the object to be adsorbed can be adjusted to 1.0 × 10 ^{14 to} 1.5 × 10 ¹⁶ Ω / □ by these treatments. Because.

Here, in the step of immersing the electrostatic chuck member in alcohol, methanol, ethanol, or isopropyl alcohol (hereinafter abbreviated as IPA) can be suitably used as the alcohol.
In the step of immersing the electrostatic chuck member in alcohol, it is more efficient to apply ultrasonic waves while immersing the electrostatic chuck member in alcohol.
Further, the temperature for drying the electrostatic chuck member is more preferably 100 to 250 ° C.

Examples of the present invention will be specifically described below to explain the present invention in more detail.

(Example)
(1) Manufacture of electrostatic chuck member 100 kg / cm ² (= 9.8 MPa) of a mixed powder obtained by adding a rare earth oxide sintering aid in a commercially available AlN powder in the addition amount shown in Table 1. Was pressed uniaxially to prepare a disk-shaped molded body of φ200 mm × 10 mm. (After sintering, it corresponds to the base of the present invention.)
Next, a φ190 mm monopolar electrode (corresponding to the electrode layer of the present invention) was placed on the molded body, and the mixed powder was filled thereon (after sintering, the upper insulation of the present invention). After that, by performing hot press sintering under the conditions of firing temperature: 1900 ° C., firing time: 2 hours, press pressure: 100 kg / cm ² , a static made of plate-shaped ceramics of φ200 mm × 15 mm is obtained. An electric chuck member was obtained.
Next, grinding is performed so that the thickness of the upper insulating layer (the layer formed by the mixed powder filled on the electrode) of the obtained electrostatic chuck member becomes 1 mm, and a hole is formed on the opposite surface, A terminal for applying voltage to the electrostatic chuck was attached.

Next, the surface roughness Ra of the adsorption surface of the electrostatic chuck member (corresponding to the contact surface of the upper insulating layer of the present invention with the object to be adsorbed) was polished to 0.5 μm or less by buffing.

After the heat treatment at 500 ° C. for 2 hours in the atmosphere, ultrasonic cleaning with methanol, ethanol or IPA is performed for 10 minutes, and the member for electrostatic chuck according to the present invention is dried by heating at a temperature of 100 ° C. for 1 hour in the atmosphere. Obtained.
(2) Evaluation of static surface resistance Table 1 shows the results of measuring the surface resistance of the obtained electrostatic chuck member by the three-terminal method at room temperature.

As apparent from the results of Table 1, according to the present invention, the surface resistance of the contact surface of the upper insulating layer of the electrostatic chuck member with the object to be adsorbed is 1.0 × 10 ^{14 to} 1.5 × 10 6. It was found that the adjustment can be made to be ¹⁶ Ω / □.

(Comparative example)
An electrostatic chuck member was produced in the same manner as in the example. Thereafter, heat treatment was performed at 500 ° C. for 2 hours in the air. Next, Table 2 summarizes the results of measuring the surface resistance of the polished surface of the electrostatic chuck member by the three-terminal method at room temperature.

As is clear from the results in Table 2, since the immersion treatment in alcohol and the drying treatment at 100 ° C. were not performed unlike the examples, the surface resistance of the electrostatic chuck member was set to 1.0 × 10 ^14. It could not be adjusted to be -1.5 × 10 ¹⁶ Ω / □.

(Example of member for Al ₂ O ₃ electrostatic chuck)
Commercially available Al ₂ O ₃ powder was uniaxially pressed at 70 kg / cm ² (= 6.89 MPa) to produce a disk-shaped molded body having a diameter of 200 mm × 10 mm. (After sintering, it corresponds to the base of the present invention.)
Next, a φ190 mm monopolar electrode (corresponding to the electrode layer of the present invention) was placed on the molded body, and the mixed powder was filled thereon (after sintering, the upper insulation of the present invention). After that, by performing hot press sintering under the conditions of firing temperature: 1600 ° C., firing time: 2 hours, press pressure: 70 kg / cm ² , a static made of plate-shaped ceramics of φ200 mm × 15 mm is obtained. An electric chuck member was obtained.
Next, grinding is performed so that the thickness of the upper insulating layer (the layer formed by the mixed powder filled on the electrode) of the obtained electrostatic chuck member becomes 1 mm, and a hole is formed on the opposite surface, A terminal for applying voltage to the electrostatic chuck was attached.

(Example of member for Si ₃ N ₄ electrostatic chuck)
A mixed powder obtained by adding 0.5 wt% and 1.0 wt% of magnesium oxide as a sintering aid to commercially available Si ₃ N ₄ powder was uniaxially pressed at 80 kg / cm ² (= 7.84 MPa), and φ200 mm × A 10 mm disk-shaped molded body was produced. (After sintering, it corresponds to the base of the present invention.)
Next, a φ190 mm monopolar electrode (corresponding to the electrode layer of the present invention) was placed on the molded body, and the mixed powder was filled thereon (after sintering, the upper insulation of the present invention). After that, by performing hot press sintering under the conditions of firing temperature: 1750 ° C., firing time: 2 hours, press pressure: 80 kg / cm ² , a static made of plate-shaped ceramics of φ200 mm × 15 mm is obtained. An electric chuck member was obtained.
Next, grinding is performed so that the thickness of the upper insulating layer (the layer formed by the mixed powder filled on the electrode) of the obtained electrostatic chuck member becomes 1 mm, and a hole is formed on the opposite surface, A terminal for applying voltage to the electrostatic chuck was attached.

Thus obtained adsorption surfaces of the electrostatic chuck members of the Al ₂ O ₃ electrostatic chuck member and the Al ₂ O ₃ electrostatic chuck member (with the object to be adsorbed on the upper insulating layer of the present invention) The surface roughness Ra was polished to 0.5 μm or less by buffing.
Next, after heat treatment at 500 ° C. for 2 hours in the atmosphere, ultrasonic cleaning with methanol, ethanol, or IPA is performed for 10 minutes, and heat drying is performed at a temperature of 100 ° C. for 1 hour in the atmosphere, thereby the electrostatic chuck according to the present invention. A member was obtained.
Table 3 summarizes the results of measuring the surface resistance of each obtained electrostatic chuck member by the three-terminal method at room temperature.

As is apparent from the results in Table 3, according to the present invention, the surface resistance of the contact surface of the upper insulating layer of the electrostatic chuck member with the object to be adsorbed is 1.0 × 10 ^{14 to} 1.5 × 10 6. It was found that the adjustment can be made to be ¹⁶ Ω / □.

Moreover, when the electrostatic chuck member obtained by the present invention was actually mounted as an electrostatic chuck device, the leakage current was small within the standard design value, and it was confirmed that a sufficient attracting force was obtained.

Claims (2)

An electrostatic chuck member comprising a base, an electrode layer formed on the upper surface of the base, and an upper insulating layer formed on the base so as to cover the electrode layer. The base and the upper insulating layer are made of 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 , and the adsorbent of the upper insulating layer The member for an electrostatic chuck, wherein the surface resistance of the contact surface at room temperature is adjusted in advance so as to be 1.0 × 10 ^{14 to} 1.5 × 10 ¹⁶ Ω / □ in advance. . Polishing the surface roughness Ra of the contact surface of the upper insulating layer of the electrostatic chuck member with the object to be adsorbed to 0.5 μm or less, and heating the electrostatic chuck member at 400 to 900 ° C. The surface resistance of the electrostatic chuck member according to claim 1, comprising: a step of immersing the electrostatic chuck member in alcohol; and a step of drying the ceramic member at 100 ° C. or higher. Adjustment method.