JPH07297265A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To obtain an electrostatic chuck having a quick response characteristic, enabling an increase of the number of sheets handled for a unit time and having an excellent performance by a method wherein the surface roughness Ra on the attracting surface side of an insulative dielectric layer covering an electrode is made a specified value or below and also the degree of flatness is made a specified value or below. CONSTITUTION:This electrostatic chuck has a structure formed by covering the opposite sides of an electrode 1 with an insulative dielectric layer 2 constituted of a sintered and/or thermally sprayed ceramic. In this electrostatic chuck, the surface roughness Ra on the attracting surface side of the insulative dielectric layer 2 is made 0.25mum or below and also the degree of flatness 20mum or below. The constituent of the insulative dielectric layer 2 is an aluminum oxide, an aluminum nitride, a silicon nitride, a silicon oxide, a zirconium oxide, a titanium oxide, SIALON, a boron nitride, a silicon carbide or a mixture of them. The insulative dielectric layer 2 is polished by using abrasive grains of diamond, the silicon carbide, a cerium oxide, the aluminum oxide or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck, and in particular, to a semiconductor, a liquid crystal, or the like, which is capable of strongly adsorbing and holding an electrically conductive, semiconductive or insulating target object electrostatically and easily detaching it. The present invention relates to an electrostatic chuck that is useful in the manufacturing process of the above.

[0002]

2. Description of the Related Art In recent years, semiconductor and liquid crystal manufacturing processes, processes such as dry etching of semiconductor devices, ion implantation, vapor deposition, and the like have been automated and dried in recent years. Therefore, the number of processes used under vacuum conditions is increasing. .
In addition, the diameter of silicon wafers and glasses as substrates has been increasing, and the positional accuracy at the time of patterning has become more and more important as the circuit becomes highly integrated and miniaturized.
Therefore, a vacuum chuck is used for transporting and fixing the substrate, but this can not be used because there is no pressure difference under vacuum conditions, even if it can suck the substrate under non-vacuum. Because the suction part is locally sucked,
There is a disadvantage that the substrate is partially distorted and high-precision alignment cannot be performed. Therefore, this vacuum chuck is unsuitable for recent semiconductor and liquid crystal manufacturing processes.

As an improvement of this defect, an electrostatic chuck for transporting a substrate by using electrostatic force or for adsorbing and fixing the substrate has attracted attention and has begun to be used, but in recent semiconductor and liquid crystal manufacturing processes. Since the flatness of wafers or glass plates, which are substrates, has become important with the miniaturization, it has been considered to use an electrostatic chuck for the correction. This electrostatic chuck is generally made by coating both sides of an electrode with a ceramic such as a sintered body, and in order to exert an electrostatic force on the electrostatic chuck, a means for applying a voltage to the internal electrode is required. However, this is realized by providing an electrode power feeding part that communicates from the outside to the electrode in a part of the ceramic to be coated, and arranging a lead wire or the like from an external power source to the electrode power feeding part.

The electrode power feeding section serves as an electrode.
When a solderable material such as copper, platinum, nickel-plated or gold-plated tungsten is used, the solder has a melting point above the electrostatic chuck operating temperature through the holes that are opened to the electrodes in the ceramic. Solder the lead wire to the electrode by using, and if this electrode cannot be soldered like graphite, tungsten, titanium nitride, etc., make a pin with a screw part with a hole such as an alloy with a coefficient of thermal expansion of ceramics. The structure is such that silver brazing is applied to the electrodes through.

[0005]

However, when this electrostatic chuck is used in a semiconductor dry process or the like, the time from when a voltage is applied until the electrostatic attraction force is generated to reach the maximum force (electrostatic force). Adsorption force saturation time) and the time from when the voltage is turned off until the electrostatic adsorption force disappears (residual adsorption force disappearance time) are required. These two times are collectively called response characteristics, The shorter this response characteristic is, the more sheets can be processed, so it is desirable to be short, but in reality, this response characteristic is very long and the number of sheets processed per unit time is small, resulting in a very high efficiency. There is a problem that is bad.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an electrostatic chuck which solves the above disadvantages and problems, and it is an insulating dielectric made of a sintered body and / or a sprayed ceramics on both sides of an electrode. In an electrostatic chuck having a structure covered with a layer, the surface roughness Ra of the insulating surface of the insulating dielectric layer is 0.25 μm or less, and the flatness is 20 μm or less. .

That is, the inventors of the present invention have conducted various studies to develop an electrostatic chuck that does not have the above-mentioned disadvantages, and as a result, the insulating dielectric in the electrostatic chuck in which both sides of the electrode are covered with the insulating dielectric layer is obtained. The surface roughness of the adsorption side of the layer is 0.25
If the flatness exceeds 20 μm and the flatness exceeds 20 μm, it is found that the electrostatic adsorption force saturation time and the residual adsorption force disappearance time, in other words, the response characteristics are significantly increased. The surface roughness Ra of the adsorbing surface is set to 0.25 μm or less and the flatness is 20 μm.
When the following is set, this response characteristic becomes dramatically faster,
The present invention has been completed by confirming that a high-performance electrostatic chuck can be obtained because the number of processed sheets increases. This will be described in more detail below.

[0008]

The present invention relates to an electrostatic chuck, which is, as described above, an electrostatic chuck having a structure in which both sides of an electrode are covered with an insulating dielectric layer made of a sintered body and / or a sprayed ceramic, The surface roughness Ra of the insulating surface of the insulating dielectric layer is 0.25 μm or less, preferably
In addition to 0.10 μm or less, the flatness is set to 20 μm or less, preferably 10 μm or less, more preferably 3 μm or less. According to this, the response characteristics described above are dramatically improved. The number of sheets to be processed per unit time can be increased, and an advantage that an electrostatic chuck with good performance can be obtained is given.

The electrostatic chuck of the present invention is supposed to have a structure in which both sides of an electrode are covered with an insulating dielectric layer. This electrode is made of aluminum, iron, copper, silver, gold, titanium, tungsten, molybdenum, It may be made of a metal such as platinum, a ceramic such as graphite, carbon, silicon carbide, titanium nitride, titanium carbide, or a mixture thereof, which is formed by screen printing, thermal spraying, photolithography or plating. You can do it in. In addition, the structure of this electrode may be a monopolar type in which one of the electrodes is attached to the substrate to be adsorbed and the other is formed in the electrostatic chuck. This is a bipolar type in which two electrodes are opposed to each other. It may be one.

The insulating dielectric layer that constitutes the electrostatic chuck serves as a chuck function portion, which is made of a sintered body and / or a sprayed ceramics. Therefore, this may be a sintered body or a mixture prepared by thermal spraying with plasma, CVD, etc., but specifically, the main component is aluminum oxide (alumina), aluminum nitride, silicon nitride, zirconium oxide, titanium oxide. Ceramics made of sialon, boron nitride, silicon carbide, or a mixture thereof.

The volume resistivity value of this insulating dielectric layer has an appropriate value depending on the temperature at which it is used. For example, when the temperature of the wafer held when this is used for a semiconductor device is 20 ° C. or lower. The volume resistivity of the insulating dielectric layer is 1
If it is about × 10 ⁸ to 1 × 10 ¹³ Ω · cm, the electrostatic force is sufficiently exerted and the device is not damaged. If the volume resistivity of the insulating dielectric layer is 1 × 10 ¹³ Ω · cm or more when the temperature of the wafer is 20 ° C or higher, the leak current flowing in the wafer is small and the circuit drawn on the wafer is small. It doesn't destroy. Therefore, for this volume resistivity value, if this is the optimum value for the temperature at which it is used,
A minute leak current flows between the insulator and the wafer, the electrostatic force is strongly generated by the Johnsen-Rahbek effect, and a good adsorption and holding state is obtained, and a chuck function section with good response characteristics can be obtained.

The electrostatic force of this electrostatic chuck is generally F = Aε (V / t) ² (where F: electrostatic force, ε: dielectric constant, V: voltage, t: thickness, A: Constant), even if high dielectric ceramic powder such as barium titanate, lead titanate, zirconium titanate, PLZT, etc. is mixed in this insulator, as long as it does not affect the semiconductor device. I don't care.

In order to exert an electrostatic force on this electrostatic chuck, a means for applying a voltage to the internal electrodes is required,
It is necessary to provide an electrode power feeding part that communicates from the outside to the electrode on a part of the ceramic to be coated, and to dispose a lead wire or the like from an external power source to the electrode power feeding part. However, when a solderable material such as copper, platinum, nickel-plated or gold-plated tungsten is used as the electrode in this electrode power supply part, electrostatic discharge is performed through the holes formed in the ceramic to the electrode. It suffices to solder the lead wire to the electrode with a solder having a melting point above the chuck operating temperature. When this electrode cannot be soldered like graphite, tungsten, titanium nitride, etc., it has a coefficient of thermal expansion of ceramics. A pin having a threaded portion made of an alloy or the like may be brazed to the electrode through the hole and silver brazed.

As shown in FIG. 1 as a longitudinal sectional view, the electrostatic chuck of the present invention has a structure in which both sides of an electrode 1 are covered with an insulating dielectric layer 2 made of a sintered body and / or a sprayed ceramics. It has what is provided with the electrode feeding part 3, and this surface 4 serves as an adsorption surface. However, in practice, it may be used by adhering it to the substrate 5. According to the present invention, this has a surface roughness Ra of 0.25 μm or less on the adsorption surface 4 side with the insulating dielectric layer,
The flatness is set to 20 μm or less, and the insulating dielectric layer may be polished by using abrasive grains such as diamond, silicon carbide (green carbon), cerium oxide, and aluminum oxide.

When the surface roughness Ra and the flatness are extremely small, the contact state between the chuck surface and the adsorbed material is good as shown in FIG. 2 which is a longitudinal sectional view of the mechanism of the electrostatic chuck of the present invention. Therefore, the charge is smoothly transferred and the response characteristics are extremely fast. However, in the conventionally known electrostatic chuck, the surface roughness Ra is as shown in FIG. 3 which is a longitudinal sectional view of the mechanism. Since the flatness is large, the movement of charges is small, and therefore the response characteristics are considered to be slow.

[0016]

EXAMPLES Examples and comparative examples of the present invention will be given below.
The surface roughness Ra and the flatness of the insulating dielectric layer in the examples are values measured by the following method. (Surface roughness Ra) According to JIS-B0601. Measuring device is D
R-100X31 (stylus type) [trade name of Kosaka Laboratory Ltd.] was used to measure the sample surface at 6 points, and the average value (μ
m) was calculated. (Flatness) BH50 at 50 points on the surface of the sample
6 [trade name of Mitutoyo Co., Ltd.] was used to obtain the height in the Z-axis direction three times (with the XY-axis as the sample surface).
The value at 150 points (μm) was calculated as the average. Examples 1 to 3, Comparative Examples 1 to 2 To 100 parts by weight of a mixture consisting of 96% by weight of aluminum oxide powder, 3% by weight of silica powder and 1% by weight of magnesia,
After adding 8 parts by weight of butyral resin, 60 parts by weight of ethanol and 12 parts by weight of dioctyl phthalate, they were kneaded in a ball mill for 50 hours to prepare a slurry.

Next, this slurry was treated with a vacuum defoaming machine to scatter a part of the solvent so as to have a viscosity of 30,000 centipoise, and a 0.7 mm thick green sheet was prepared from this slurry using a doctor blade. Two circular plates each having a diameter of 180 mm were cut out from this green sheet, and a bipolar electrode was concentrically printed at a distance of 2.5 mm by screen printing using tungsten paste on one of the green sheet circular plates. A hole of φ2 mm was made in the center of the remaining one green sheet to serve as an electrode power feeding part.

On the printed surface of the printed green sheet, another green sheet provided with an electrode power feeding portion is superposed and integrated with a press heated to 100 ° C. under a pressure of 80 kg / cm ² . Then, when sintered in an atmosphere gas of 25% hydrogen and 75% nitrogen at a temperature of 1,630 ° C, a sintered body was obtained. Both sides of this sintered body were polished with diamond fixed abrasive grains # 3,000. The thickness is 1mm and the surface roughness is 0.13μm, 0.22μm, 0.10μm.
And flatness of 6.8 μm, 2.7 μm, 9.2 μm (Examples 1 to 3), and surface roughness Ra of 0.35 μm,
We have produced 19μm and flatness of 120.5μm and 150.6μm (Comparative Examples 1 and 2), and the nickel electrode and the gold electrode are applied to the tungsten electrode which is seen from this electrode power supply part, and two lead wires are attached to this. When an electrostatic chuck was manufactured by soldering with a solder having a melting point of 300 ° C. and the response characteristics of the electrostatic chuck were measured, the results shown in Table 1 were obtained.

[0019]

[Table 1]

[0020]

As described above, the present invention relates to an electrostatic chuck, which has a sintered body and / or a sintered body on both sides of an electrode.
Alternatively, in an electrostatic chuck having a structure coated with an insulating dielectric layer made of sprayed ceramics, the surface roughness Ra of the insulating surface of the insulating dielectric layer is 0.25 μm or less,
The feature is that the flatness is set to 20 μm or less. According to this, the response characteristic can be remarkably increased as described above, and the number of processed sheets per unit time is remarkably improved. As a result, a high-performance electrostatic chuck can be obtained, which is advantageous in that it is useful in a semiconductor or liquid crystal manufacturing process.

[Brief description of drawings]

FIG. 1 shows a series of vertical cross-sectional views of an electrostatic chuck of the present invention.

FIG. 2 is a vertical sectional view of the mechanism of the electrostatic chuck of the present invention.

FIG. 3 is a vertical sectional view of a mechanism of a conventional electrostatic chuck.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electrode 2 ... Insulating dielectric layer 3 ... Electrode power feeding part 4 ... Adsorption surface 5 ... Substrate 6 ... Wafer 7 ... Charge flow

[Procedure amendment]

[Submission date] June 27, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

On the printed surface of the printed green sheet, another green sheet provided with an electrode power feeding portion is superposed and integrated with a press heated to 100 ° C. under a pressure of 80 kg / cm ² . Then, when sintered in an atmosphere gas of 25% hydrogen and 75% nitrogen at a temperature of 1,630 ° C, a sintered body was obtained. Both sides of this sintered body were polished with diamond fixed abrasive grains # 3,000. The thickness is 1mm and the surface roughness is 0.13μm, 0.22μm, 0.10μm.
And flatness of 6.8 μm, 2.7 μm, 9.2 μm (Examples 1 to 3), and surface roughness Ra of 0.35 μm,
We manufactured 19 μm flatness 3.5 μm and 38.0 μm (Comparative Examples 1 and 2). Nickel plating and gold plating were applied to the tungsten electrode seen from this electrode power supply part, and two lead wires were attached to this. When an electrostatic chuck was manufactured by soldering with a solder having a melting point of 300 ° C. and the response characteristics of the electrostatic chuck were measured, the results shown in Table 1 were obtained.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiro Kubota 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratory

Claims (3)

[Claims] 1. An electrostatic chuck having a structure in which both sides of an electrode are covered with an insulating dielectric layer made of a sintered body and / or a sprayed ceramics, and a surface roughness Ra of the insulating dielectric layer on the attracting surface side. Is less than 0.25 μm and the flatness is less than 20 μm. 2. The electrode is aluminum, iron, copper, silver, gold,
Metals such as titanium, tungsten, molybdenum, platinum,
The electrostatic chuck according to claim 1, which is made of ceramics such as graphite, carbon, silicon carbide, titanium nitride and titanium carbide, or a mixture thereof. 3. The insulating dielectric layer comprises aluminum oxide, aluminum nitride, silicon nitride, silicon oxide, zirconium oxide, titanium oxide, sialon, boron nitride, silicon carbide or a mixture thereof. The electrostatic chuck according to claim 1, wherein