JP4326874B2 - Electrostatic chuck and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electrostatic chuck and a manufacturing method thereof. In particular, a base, a lower insulating layer formed on the upper surface of the base, an electrode layer formed on the lower insulating layer, and formed on the lower insulating layer so as to cover the electrode layer. The present invention also relates to an electrostatic chuck comprising the upper insulating layer and a method for manufacturing the same.

  For example, in a thin film forming process or a dry etching process in a semiconductor manufacturing process, since a required film forming process or etching process is performed on an article on a flat plate such as a wafer, it is necessary to securely hold it on a mounting table. As a holding device that meets these requirements, an electrostatic chuck that holds an article in close contact using electrostatic action is widely used.

  A conventional electrostatic chuck is formed by plasma-spraying ceramics such as alumina to form an insulating film so as to cover a metal plate electrode. For this reason, it can be manufactured with a relatively small number of steps, and the obtained electrostatic chuck has the advantage of being excellent in heat resistance and durability. However, recently, a type in which a lower insulating layer, an electrode layer, and an upper insulating layer are sequentially formed on a base by thermal spraying is becoming mainstream.

However, the insulating film, that is, the sprayed coating of the electrostatic chuck thus obtained has a porous shape with an infinite number of minute pores, so that the withstand voltage characteristic is not so high. Therefore, it is difficult to obtain a large holding force. In addition, a discharge phenomenon may occur in the pores. That is, a problem that current flows through the pores rarely occurs between the adsorbed and held article and the electrode layer, and there is still room for improvement. In view of such circumstances, a sealing treatment technique has been proposed that fills pores with a resin to improve withstand voltage characteristics and improve adsorption holding capacity (see, for example, Patent Document 1).
JP 59-152636 A

Incidentally, in recent years, there has been an increasing demand for an electrostatic chuck having improved withstand voltage characteristics for the purpose of obtaining a large holding force. For this reason, each of the methods that make up the electrostatic chuck has been dealt with by increasing the thickness of the sprayed coating. In this case, the thermal spray coating shrinks from the edge of the electrostatic chuck due to the contraction stress of the sprayed coating when the upper insulating layer is formed. There was a problem that peeling occurred. Therefore, the problem to be solved by the present invention is to provide an electrostatic chuck that exhibits excellent withstand voltage characteristics without causing peeling of the upper insulating layer even when the thickness of the upper insulating layer is large, and a method for manufacturing the same It is to be.

  In the process of pursuing earnest research to solve the above problems, the present inventors can suppress the peeling of the thermal spray coating if the shape is such that the shrinkage stress of the thermal spray coating can be reduced during the thermal spraying of the upper insulating layer. Thought. For this purpose, if the thermal spraying is performed using a frame-shaped masking jig having a special shape, that is, a frame-shaped masking jig provided with an overhanging portion, the amount of deposited thermal spray particles is reduced by the action of the overhanging portion. Since it gradually decreases toward the main body, the edge of the upper insulating layer naturally becomes a taper shape, and the present invention has been completed based on the idea that shrinkage stress will not increase. As a result, even when the upper insulating layer has a large thickness, it is possible to obtain an electrostatic chuck that exhibits excellent withstand voltage characteristics without peeling of the upper insulating layer film formed by thermal spraying. is there.

  That is, the above-mentioned problems are a base, a lower insulating layer formed on the upper surface of the base, an electrode layer formed on the lower insulating layer, and the lower insulating layer so as to cover the electrode layer. An electrostatic chuck comprising: an upper insulating layer formed on the layer, wherein the edge of the upper insulating layer is formed in a tapered shape. The

And further, the above issues
A base, a lower insulating layer formed on the upper surface of the base, an electrode layer formed on the lower insulating layer, and an upper portion formed on the lower insulating layer so as to cover the electrode layer A method for producing an electrostatic chuck comprising an insulating layer,
A first step of spraying a material to be the lower insulating layer on the upper surface of the base;
A second step of spraying the material to be the electrode layer except for the edge of the lower insulating layer obtained in the first step;
A frame-shaped masking jig provided with a projecting portion protruding above the upper insulating layer forming region so that a gap is formed between the edge surface of the lower insulating layer and the upper insulating layer forming region. A third step of spraying a material to be the upper insulating layer so as to cover the edge surface of the lower insulating layer and the electrode layer in a state of being arranged so as to surround the peripheral edge;
It solves by the manufacturing method of the electrostatic chuck of Claim 1 characterized by the above-mentioned.

  In the present invention, the “tapered shape” means a shape whose thickness decreases toward the end. Therefore, the slope of the tapered edge portion may be flat or may be a curved surface convex upward (or downward).

According to the present invention, it has a shape that can reduce the shrinkage stress of the thermal spray coating during the thermal spraying of the upper insulating layer (that is, the edge of the upper insulating layer is configured in a tapered shape). As is clear from the examination results of the comparative example, even if an electrostatic chuck is configured by including a thick upper insulating layer, the static insulation having excellent withstand voltage characteristics without peeling of the upper insulating layer film formed by thermal spraying. There is an effect that an electric chuck can be obtained.

  The first embodiment of the present invention will be specifically described below with reference to FIGS. 1 is a plan view of the electrostatic chuck according to the present invention, FIG. 2 is an enlarged cross-sectional view of the main part of the electrostatic chuck taken along line XX in FIG. 1, and FIGS. It is the schematic which shows the procedure of the manufacturing method of the electrostatic chuck which concerns on embodiment. (FIGS. 1 to 3 are all schematic views schematically shown.)

  The electrostatic chuck according to the present embodiment (hereinafter referred to as the present electrostatic chuck) is a monopolar type as shown in FIGS. 1 and 2 and has an outer shape of a short flat plate. As will be described later, this electrostatic chuck is obtained using the electrostatic chuck manufacturing method according to the present embodiment (hereinafter referred to as the present manufacturing method), as can be seen from FIG. As main components, a base 1, a lower insulating layer 2, an electrode layer 3, and an upper insulating layer (dielectric layer) 4 are provided. Further, the edge of the upper insulating layer 4 is tapered (4a in the figure).

  Among these, the base 1 is comprised from the metal-ceramics composite material (MMC), and the through-hole for installing the electrode terminal mentioned later is actually formed in multiple numbers. However, the material of the base 1 may be basically any material, and is composed of, for example, a single metal such as aluminum, an aluminum alloy, or another low thermal expansion alloy in addition to the metal-ceramic composite material. . Which material is used is selected in consideration of the operating temperature of the electrostatic chuck.

  Next, regarding the lower insulating layer 2 provided on the upper surface of the base 1, this is formed by plasma spraying, for example, alumina or the like on the upper surface of the base 1. On the other hand, the electrode layer 3 provided on the lower insulating layer 2 has a short shape slightly smaller than that of the base 1, for example, nickel (or a single metal such as aluminum, chromium, cobalt, molybdenum, tungsten, These alloys are formed by plasma spraying the surface of the lower insulating layer 2. Further, the edge of the electrode layer 3 is tapered, in other words, the edge is composed of an upwardly convex curved surface whose thickness gradually decreases toward the end.

  The upper insulating layer 4 provided on the lower insulating layer 2 so as to cover the electrode layer 3 is plasma sprayed with, for example, alumina containing a small amount of titanium oxide on the surface of the electrode layer 3 and thus on the lower insulating layer 2. It is formed by doing. The surface roughness Ra of the upper insulating layer 4 is about 0.1 to 2.0 μm. However, besides alumina, an appropriate material can be selected and used according to the required dielectric constant value. In the present embodiment, the monopolar electrostatic chuck is taken as an example, but the technique of the present invention can also be applied to a bipolar electrostatic chuck having two electrodes. Moreover, although the base 1 and the electrode layer 3 were made into short shape here, it cannot be overemphasized that these shapes are arbitrary.

  Although not particularly illustrated, the electrode layer 3 is connected to the electrode terminal for feeding described above. By applying a voltage to the electrode layer 3 using this, the electrostatic chuck can attract and hold the article on the surface of the upper insulating layer 4 (at this time, the article is grounded).

  In the present embodiment, the thickness of the lower insulating layer 2 and the effective thickness of the upper insulating layer 4 are both 100 to 800 μm. If the thickness is within this range, sufficient withstand voltage performance can be obtained, so that dielectric breakdown is unlikely to occur, and furthermore, the difference in thermal expansion from the base 1 is suppressed to such an extent that it does not matter at all. Cracks and breakage due to thermal shock are less likely to occur. On the other hand, the thickness of the electrode layer 3 is about 30 to 100 μm. If the thickness of the electrode layer 3 is within this range, a particularly uniform sprayed coating can be obtained, so that unevenness in adsorption force does not occur. In addition, since the step between the electrode layer 3 and the lower insulating layer 2 is sufficiently small, the withstand voltage characteristic of the upper insulating layer 4 does not deteriorate due to the presence of the step.

  Subsequently, the present manufacturing method, that is, the base 1, the lower insulating layer 2 formed on the upper surface, the electrode layer 3 formed thereon, and the upper insulating formed on the lower insulating layer 2 so as to cover it. A manufacturing procedure of the electrostatic chuck including the layer 4 will be described.

  In order to obtain this electrostatic chuck, first, the surface of the base 1 is uniformly roughened by using a blast material such as alumina or silicon carbide. After the cleaning, an undercoat layer is further formed on the surface of the base 1 for enhancing the adhesion between the base 1 and the insulating layer formed thereon. Specifically, a metal thin film made of a single metal such as nickel, aluminum, chromium, cobalt, molybdenum, or an alloy of these metals is formed on the surface of the base 1 using an arc spraying method or a plasma spraying method. Note that this undercoat layer is not indispensable, and whether or not to provide it is determined in consideration of the use environment of the electrostatic chuck.

  Subsequently, a material to be the lower insulating layer 2 is sprayed on the undercoat layer and thus on the base 1. That is, the lower insulating layer 2 made of ceramics such as alumina is formed by plasma spraying (first step: see FIG. 3A). However, the undercoat layer is not shown in FIG.

  When the lower insulating layer 2 is obtained by the first step, the masking tape 5 is attached to the edge surface of the lower insulating layer so as to surround the electrode layer forming region (the region surrounded by the broken line in FIG. 1). wear. Then, nickel (a material to be an electrode layer) is plasma sprayed in a specific region on the lower insulating layer 2 surrounded by the masking tape 5 to form the electrode layer 3 [second step: FIG. reference〕.

  Thereafter, the masking tape 5 is removed. At this time, a burr 3a is formed on the edge of the electrode layer 3 obtained in the second step, as shown in FIG. Therefore, in this manufacturing method, this burr 3a is removed using a diamond tool (not shown). That is, the edge of the electrode layer 3 is polished into a taper shape so that the thickness decreases toward the end (see FIG. 3D).

  When the above process is completed, plasma spraying of alumina containing a small amount of titanium oxide (a material that becomes the upper insulating layer) is performed so as to cover the edge surface of the lower insulating layer and the electrode layer 3, and the upper insulating layer (dielectric layer) ) 4 is formed [third step: see FIG. 3 (e)]. At this time, the frame-shaped masking jig 6 having a special shape shown in FIG. 4 is arranged on the jig mounting table 7 so as to surround the periphery of the base 1 as shown in FIG. . By doing so, an electrostatic chuck characterized in that the edge of the upper insulating layer of the present invention is formed in a tapered shape can be obtained. This shape has the effect of reducing the shrinkage stress of the thermal spray coating during the thermal spraying of the upper insulating layer, and therefore has an effect of suppressing peeling of the upper insulating layer coating.

Here, the frame-shaped masking jig 6 will be described in detail. FIG. 4 shows a partially broken perspective view (a) and an enlarged sectional view (b) of a main part of the frame-shaped masking jig according to the present invention.
The frame-shaped masking jig 6 has a mouth shape made of stainless steel (SUS304) and has a substantially L-shaped cross section as shown in an enlarged view in FIG. That is, the masking jig includes an overhanging portion that protrudes above the upper insulating layer formation region. The overhanging portion is formed so that a gap is formed between the frame-shaped masking jig and the upper insulating layer forming region on the edge surface of the lower insulating layer when the frame-shaped masking jig is placed so as to surround the peripheral portion of the base. It will protrude above the upper insulating layer formation region. Therefore, the vertical and horizontal dimensions of the opening of the frame-shaped masking jig are slightly smaller than the vertical and horizontal dimensions of the upper insulating layer forming region.

Incidentally, in this embodiment, the length of the overhang portion (indicated by L in FIG. 4) is 1 to 2 mm, the thickness (indicated in FIG. 4 by W) is 1 to 3 mm, and the height of the bottom surface of the overhang portion, that is, The gap width (indicated by H in FIG. 4) was 1 to 3 mm. The overlap amount (indicated by U in FIG. 3) between the overhanging portion and the upper insulating layer was set to be 0.3 to 1.0 mm. Needless to say, the frame-shaped masking jig used in this manufacturing method is not limited to that shown in FIG. 4, and various other shapes are used as necessary.

Now, if the frame-shaped masking jig is arranged so as to surround the periphery of the base, in that state, plasma spraying is performed to cover the electrode layer with alumina containing a small amount of titanium oxide, thereby forming the upper insulating layer. . Finally, the electrostatic chuck having a cross section as shown in FIG. 2 is completed by sequentially subjecting the surface of the upper insulating layer 4 to sealing, grinding, and lapping.

In addition, as a substance used for the sealing treatment, that is, a substance filled in the pores, colloidal slurry such as silica sol, alumina sol, magnesia sol, or metal alkoxide such as SiO ₂ , Al ₂ O ₃ , TiO _2, etc. Polymers and those containing various resins such as melamine resin, acrylic resin, phenol resin, fluororesin, and silicon resin in addition to these polymers can be mentioned. Filling the pores with such a substance (impregnation into the insulating layer) is performed by setting a semi-finished electrostatic chuck in a vacuum desiccator and vacuuming it. As a result, the slurry permeates into the inside from the surface of the insulating layer. The slurry filled in the pores in this way is dried in consideration of its characteristics, and then the above-described grinding process is performed.

Example 1
As a base material, 70 parts by weight of # 180 (average particle size 66 μm) commercially available SiC powder as a reinforcing material, and 30 weights of # 500 (average particle size 25 μm) commercially available SiC powder as a reinforcing material are used. Part, an appropriate amount of colloidal silica liquid as a binder (amount of silica solid content of 2 parts by weight), 0.2 parts by weight of Formaster VL (manufactured by San Nopco) as an antifoaming material, and ion-exchanged water 24 parts by weight were prepared, and these were mixed using a pot mill for 12 hours. Subsequently, the slurry thus obtained was poured into a metal mold with a mesh (that can obtain a rectangular flat plate-shaped body), subjected to filter press, and after demolding, was fired at 1000 ° C. to form a preform.

  Subsequently, an aluminum alloy (Al-12Si-3Mg-2Cu-3Ti) is infiltrated into the preform under non-pressurization at 825 ° C. for 60 hours in a nitrogen stream, and then cooled. In this way, a base (length 209 mm, width 157 mm, thickness 10 mm) made of a metal-ceramic composite material with a SiC powder content of 65 vol% was produced.

Next, in order to improve the adhesion, the base surface is blasted until the surface roughness is at least 5 μm or more in Rmax. Then, an Al ₂ O ₃ layer having a thickness of 700 μm, that is, a lower insulating layer is formed on the upper surface by plasma spraying. Thereafter, a Ni electrode layer having a thickness of 50 μm is formed on a specific region surrounded by a masking tape on the lower insulating layer by plasma spraying.

When the electrode layer is thus provided, the masking tape is peeled off and the edge thereof is polished into a taper shape using a diamond tool. Further, a frame-shaped masking jig was installed, and an Al ₂ O ₃ layer having a thickness of 800 μm, that is, an upper insulating layer was formed on the upper surface by plasma spraying so as to cover the electrode layer. In this way, an electrostatic chuck in which the edge of the upper insulating layer is tapered is obtained. Finally, a sealing process is performed using SiO2 metal alkoxide in vacuum, followed by grinding and lapping in this order. The upper insulating layer has a thickness of 650 μm and a surface roughness Ra of 0.2 μm. An electrostatic chuck according to an embodiment of the invention was produced.
Here, the main dimension values of the used frame-shaped masking jig are as follows.
Overhang length L: 2mm
Overhang thickness W: 2mm
Height of bottom surface of overhang (gap width) H: 2 mm
Overlap amount of overhang and electrode layer formation region U: 1mm

(Comparative example)
An electrostatic chuck for a comparative example was produced in the same manner as in the example except that the frame-shaped masking jig was not used during the thermal spraying of the upper insulating layer.

(Evaluation results)
First, an overview inspection of the electrostatic chuck after thermal spraying was performed, and the presence or absence of peeling of the thermal spray coating was confirmed. Thereafter, with respect to healthy samples, a withstand voltage test was performed by applying a DC voltage up to 5 KV with a glass substrate having an ITO film placed on the upper surface of the electrostatic chuck.
The electrostatic chucks of the examples were in a healthy state with no occurrence of peeling of the thermal spray coating serving as the upper insulating layer, and cleared the withstand voltage test with an applied voltage of 5 KV. On the other hand, it was confirmed that the electrostatic chuck of the comparative example was unable to exhibit the electrostatic chuck function because the thermal spray coating was peeled off after the upper insulating layer was sprayed.

It is a top view of the electrostatic chuck which concerns on this invention. It is a principal part expanded sectional view of the electrostatic chuck which concerns on this invention. It is the schematic which shows the procedure of the manufacturing method of the electrostatic chuck which concerns on this invention. 1 is a partially broken perspective view and an enlarged cross-sectional view of a main part of a frame-shaped masking jig according to the present invention.

Explanation of symbols

1; base 2; lower insulating layer 3; electrode layer 4; upper insulating layer (dielectric layer)
5; Masking tape 6: Frame-shaped masking jig 7; Jig mounting table

Claims (2)

The base,
A lower thermal spray insulating layer formed on the upper surface of the base;
A thermal spray electrode layer having a thickness of 30 to 100 μm formed on the lower thermal spray insulating layer;
An upper thermal spray insulating layer having a thickness of 100 to 800 μm formed on the lower thermal spray insulating layer so as to cover the thermal spray electrode layer;
An electrostatic chuck comprising:
An electrostatic chuck characterized in that an edge portion of the upper thermal spray insulating layer formed on the lower thermal spray insulating layer on which the thermal spray electrode layer is not formed is formed in a taper shape. A base, a lower sprayed insulating layer formed on the upper surface of the base, and the sprayed electrode layer formed on the lower sprayed insulating layer, on the lower sprayed insulating layer so as to cover the sprayed electrode layer A method of manufacturing an electrostatic chuck comprising: an upper sprayed insulating layer formed on
A first step of spraying a material to be the lower thermal spray insulating layer on the upper surface of the base;
A second step of spraying the material to be the sprayed electrode layer except the edge of the lower sprayed insulating layer obtained in the first step;
Wherein the frame-shaped masking jig having a projecting portion which projects above the upper sprayed insulating layer formation region so that the gap is formed between the upper sprayed insulating layer formation region of the edge surface of the lower spray insulation layer A third step of spraying a material to be the upper thermal spray insulation layer so as to cover the edge surface of the lower thermal spray insulation layer and the thermal spray electrode layer in a state of being arranged so as to surround the peripheral edge of the base;
The method of manufacturing an electrostatic chuck according to claim 1, comprising:

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