JP2003077995A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck difficult to produce nonconformity such as peeling of an insulating layer even when a thickness of the insulating layer is 0.1-4.0 mm. SOLUTION: The electrostatic chuck is provided with a chuck body 1 composed of a sintered body including aluminum nitride, and an electrode 2 embedded in the chuck body 1. The electrostatic chuck provided with mutually opposite base layers 11 sandwiching the electrode 2 by the chuck body 1 and the insulating layer 12 whose thickness is 0.1-4.0 mm is made a structure composed of a flat plate-like punching metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck used for attracting and holding a semiconductor wafer, a flat display panel, a flexible substrate or the like.

[0002]

A semiconductor wafer is subjected to a predetermined process in a reduced pressure atmosphere, that is, inside a reduced pressure manufacturing apparatus. An electrostatic chuck is one of the jigs used to hold the adsorbed material. The jig applies a voltage to the electrodes covered with an insulating layer,
The object to be attracted can be electrostatically attracted to the surface of the insulating layer.

By the way, as the material for the insulating layer, resins such as polyimide and ferroelectric ceramics such as CaTiO ₃ are most common. However, the electrostatic chuck whose insulating layer is made of resin has problems in wear resistance and heat resistance. On the other hand, with respect to the electrostatic chuck having the insulating layer made of the above ceramics, such a problem does not pose a problem. However, since the thermal conductivity is low, another problem arises in that the temperature of the object to be adsorbed becomes non-uniform, for example, in the etching process. Furthermore, recently, fluorine-based plasma is often used in the etching process, and in order to cope with this, further improvement in corrosion resistance is required for the electrostatic chuck.

In view of these circumstances, recently, an electrostatic chuck has been developed which uses aluminum nitride, which exhibits high wear resistance and heat resistance, and also has excellent thermal conductivity and corrosion resistance, as a material for an insulating layer. It has been widely used in general. Incidentally, such an electrostatic chuck is often manufactured by a method of arranging a metal plate to be an electrode in aluminum nitride powder (raw material powder) and integrally firing it (especially hot press firing).

Besides this, there is a manufacturing method using an aluminum nitride green sheet. More specifically, in the manufacturing method, first, an aluminum nitride green sheet is coated (screen printed) with a paste containing tungsten or molybdenum as a main component to form a layer to be an electrode. Next, stack and press green sheets,
Further, by baking it, an electrostatic chuck can be obtained. However, when the green sheet laminate is fired, the entire body does not necessarily shrink uniformly, and the electrodes are often distorted. Therefore, this manufacturing method has a poor yield,
It is rarely used in practice.

As is well known, in the electrostatic chuck, if the other conditions are the same, the insulating layer having a smaller thickness is
Exhibits greater adsorption capacity. For this reason, the electrostatic chuck made of aluminum nitride is also required to have a smaller insulating layer thickness.
The target value of this insulating layer thickness is 4.0 mm.
However, if the thickness of the insulating layer is reduced to this extent, peeling of the insulating layer (peeling from the electrode) frequently occurs during processing or use thereof. That is,
The base layer and the insulating layer, which face each other with the electrode sandwiched therebetween and which jointly constitute the chuck body, are relatively easily separated.

Therefore, the problem to be solved by the present invention is to provide an electrostatic chuck which is less likely to cause a failure even when the thickness of the insulating layer is small. Especially when the insulation layer thickness is
An object of the present invention is to provide an electrostatic chuck in which a defect such as peeling of an insulating layer is unlikely to occur even when the thickness is 0.1 to 4.0 mm.

[0008]

As a result of intensive research to solve the above problems, the present inventor has used a porous electrode having a large number of fine openings as an electrode, which is made of aluminum nitride. It has been found that the insulating layer and the base layer may be configured to be in direct contact with each other at many points.
That is, when such a structure is adopted, even if the thickness of the insulating layer is small, even if it is 0.1 to 4.0 mm, it becomes extremely difficult for problems such as peeling of the insulating layer to occur.
Durability and ease of processing of the electrostatic chuck can be dramatically improved.

The porous electrode may be made of a metal mesh material, that is, a metal net, or a thin metal plate having a large number of holes formed at predetermined intervals, that is, a flat punching metal. . However, as a result of further research, it was found that the one constituted by using the wire mesh is not preferable as the electrode of the electrostatic chuck according to the present invention. That is, the present inventor found out that the porous electrode is limited to the one made of punching metal. This is for the following reasons.

Since the metal mesh (metal mesh material) is obtained by vertically and horizontally combining metal wire rods, the contact condition between the metal wire rods is not uniform. By the way, if you use a special wire mesh (for example, a tortoise wire mesh or a welded wire mesh), such a problem does not occur. However, the material forming the electrodes, therefore, the metal wire must be composed of refractory metals (to withstand the high temperatures during firing), while refractory metals are very difficult to process. There is a difficult reality. Therefore, as the wire net, it is necessary to use a plain weave wire net in which the contact condition between the metal wires is necessarily nonuniform.

In an electrostatic chuck constructed by using aluminum nitride, it is common to develop the attraction force not by Coulomb force but by Johnson-Rahbek force for various reasons. In order to utilize this Johnson-Rahbek force, the volume resistivity of aluminum nitride at the operating temperature of the electrostatic chuck is 1 × 10 ⁸ to 1 ×.
It must be within the range of 10 ¹² Ω · cm.

By the way, as is well known, the volume resistivity of ceramics such as aluminum nitride decreases as the temperature rises, and as a result, current easily flows through the interior. Therefore, the fact that the Johnson-Rahbek force can be utilized means that the aluminum nitride sintered body is in a state in which a current easily flows. Here, if the metal wires are not securely in contact with each other, that is, if they are separated from each other, electric discharge occurs at that position and the ambient temperature is raised.

When a wire net in which the contact condition between metal wires is non-uniform is used, such a phenomenon occurs frequently everywhere and the temperature unnecessarily increases. However, as described above, the volume resistivity of ceramics whose temperature rises decreases,
As a result, the suction force is further increased. If such a phenomenon becomes severe, for example, a leak current flowing through a semiconductor wafer, which is an object to be adsorbed, exceeds a limit value, and a device formed on the wafer surface is destroyed. Therefore, the wire mesh is not preferable as the electrode material of the electrostatic chuck.

On the other hand, in the electrode made of punching metal, naturally, the above-mentioned problem (temperature rise due to discharge) does not occur at all. Therefore, the temperature of the electrostatic chuck is always kept at a normal value, and therefore troubles such as damage of the object to be attracted do not occur.

In turn, the electrode made of wire mesh is
The reason why the porous electrode is not preferable as a component of the electrostatic chuck according to the present invention and is limited to the one formed of punching metal is as follows.

The electrostatic chuck is also used in a process called temperature cycle. Therefore, the temperature changes abruptly in a fairly wide range. At this time, stress is generated inside the electrostatic chuck due to the difference in thermal expansion coefficient between the aluminum nitride and the metal material forming the electrode. However, when the electrode is made of a wire mesh, the metal wire material forming the electrode is essentially prone to cracks, so that the electrode is easily broken, and as a result, the original function cannot be exerted. That is, adsorption unevenness occurs. In this state, temperature unevenness occurs on the object to be attracted such as a semiconductor wafer held by the electrostatic chuck by suction, which causes warping or undulation of the object to be attracted. When such a phenomenon occurs, needless to say, the quality of the film formed on the surface of the adsorbed material is remarkably deteriorated.

On the other hand, in the electrode made of punching metal as described above, unlike the wire mesh, some cracks do not pose a problem. In other words, since it does not cause a fatal defect such as wire breakage in the wire mesh, even if it is used under severe conditions where the temperature changes abruptly over a wide range, there is a long-term problem that the adsorption capacity decreases. Does not happen over a period of time.

The present invention has been made on the basis of such new knowledge, and the above-mentioned problem is provided with a chuck body made of a sintered body containing aluminum nitride and an electrode embedded in the chuck body. The chuck body is an electrostatic chuck including a base layer facing each other with the electrode interposed therebetween and an insulating layer having a thickness of 0.1 to 4.0 mm, wherein the electrode is a flat plate punching metal. It is solved by an electrostatic chuck characterized in that it is composed of

In the electrostatic chuck of the present invention,
The electrode has a thickness of 0.05 to 2.00 mm, especially
It is preferably 0.05 to 1.00 mm. This is for the following reason.

First, if the thickness of the electrode is less than 0.05 mm, it cannot be sometimes ignored when it is embedded in aluminum nitride powder and a large pressure is applied, especially when hot-press firing treatment is performed. Problems such as disconnection may occur. On the other hand, when the thickness of the electrode exceeds 2.00 mm, even if the sintered body (chuck body) in which the electrode is embedded is not cracked, the insulating layer during processing is likely to be rapidly peeled off.

The punching metal forming the electrodes is formed by laser treatment or etching treatment on the metal plate.
Alternatively, it can be obtained by punching and forming a myriad of openings or holes, but the thickness of this metal plate is 2.
If it exceeds 00 mm, it becomes difficult to process by any method, and the time and cost required for it become significantly large. Therefore, considering workability and cost,
After all, the thickness of the electrode is 2.00 mm or less, especially 1.00 m
It is preferably m or less.

The hole shape of punching metal and the arrangement thereof (hereinafter, both are collectively referred to as "pattern") are as follows: round hole staggered 45 degrees, round hole staggered 60 degrees, round hole series. 90 °, square hole in series, square hole in zigzag, long hole in zigzag, long hole in series, etc. are common (the main ones are illustrated and explained later). However, since the electrostatic chuck is usually manufactured by integrally firing using a hot press firing method, there is a non-negligible difference in residual strain accumulation between the outer periphery and the inside. Therefore, it is conceivable that cracking or peeling may occur from the electrode as a starting point during processing.

Therefore, a pattern different from that of other portions can be adopted for the portion where the residual strain is likely to be accumulated. Specifically, it is conceivable to change the hole shape and its arrangement, mix holes of different shapes, and further change the hole interval (use of unequal pitch). In addition to the electrostatic chuck,
Various holes such as push-up pin holes and helium holes are often formed. Therefore, for the same reason as above, the pattern of the punching metal around the hole may be changed to a suitable pattern different from the other portions.

By the way, the technique of the present invention has a thickness of 0.1 to
As described above, the reason why the electrostatic chuck provided with the insulating layer having a thickness of 4.0 mm is that the smaller the thickness of the insulating layer is, the larger the adsorption capability is exerted under the other conditions. Is. Here, this point will be explained in more detail.

Generally, in electrostatic chucks, the smaller the thickness of the insulating layer, the better the adsorption capacity thereof, and
The electrical response, that is, the time characteristic of the adsorption action when a voltage is applied and the time characteristic of the desorption action when the voltage application is stopped are also excellent. Now, if the thickness of the insulating layer is less than 0.1 mm, the adsorption force will certainly be stronger, but on the other hand, the insulating layer may peel off during processing, or during use (the temperature changes rapidly during use). The problem that the insulating layer peels frequently occurs.

On the other hand, the thickness of the insulating layer is 4.0 mm.
When it exceeds, the electric response is suddenly deteriorated, and as a result, the time required to adsorb the object to be adsorbed and the time required to desorb it become very long. The insulating layer may be embossed or may have irregularities such as helium grooves. However, even in this case, the insulating layer is configured such that the thickest part has a thickness of 4.0 mm or less and the thinnest part has a thickness of 0.1 mm or more.

Furthermore, the technique of the present invention can be applied to both a monopolar type having only one electrode and a bipolar type having two electrodes. Further, the shape (planar shape) of the electrodes is arbitrary, but in the case of a bipolar type in particular, it is common to adopt comb-like shapes that mesh with each other.

In the electrostatic chuck according to the present invention, the punching metal forming the electrode has an opening ratio of 3.1.
.About.81.0%, particularly preferably 3.1 to 70.0%. This is for the following reasons.

First, in the case of using a punching metal having an excessively small total opening area such that the open area ratio is less than 3.1%,
The area in which the base layer and the insulating layer that face each other with the electrode interposed therebetween are in direct contact with each other is equal to or less than a preferable value. As a result, there is rarely a problem that the insulating layer peels off from the electrode during processing or use. On the other hand, the open area ratio is 8
If a punching metal with an excessive total opening area of more than 1.0% is used, a phenomenon similar to wire breakage will occur relatively easily and, in addition, sufficient suction force will be obtained. Sometimes you can't get it. Furthermore, in fact, when the porosity exceeds 70.0, even if the porosity value is the same, the adsorption performance slightly varies depending on the pattern. For reference, the open area ratio α (%) is calculated by the following formula. α = (A / S) × 100 Here, A is the total opening area (total area of the holes), and S is the electrode area including the area of the hole portion.

By the way, when an electrostatic chuck is constructed by using two kinds of punching metals having different hole shapes and arrangements, that is, patterns having the same opening ratio as electrodes, specifically speaking, for example, Square hole with one side length of 3.0 mm, center distance (pitch) of 6.0 mm
Perforated metal (25% open area)
And a square hole with a side length of 20.0 mm and a center distance of 4
When two types of electrostatic chucks are configured using punching metal (perforation rate 25%) arranged so as to have a thickness of 0.0 mm, the one using punching metal having a large number of small holes has uneven suction force. Is less, and generally exhibits desirable characteristics.

However, which one is preferable cannot be easily determined because it actually depends on the property of the substance to be adsorbed. For example, when used in a work of heating a silicon wafer or the like and then performing a dry etching process, there is no problem even if an electrostatic chuck using punching metal in which large holes are formed at large intervals is used as an electrode. .

However, when the flexible substrate formed by sandwiching a copper foil with a polyimide sheet is used for dry etching, etc., if the hole of the punching metal is large, the suction force will be extremely reduced only in this portion, so that it is flexible. The part of the substrate corresponding to that position is in a state of being raised. In this case, the raised portion may burn during the dry etching process. Therefore, when used for such a treatment, it can be said that the electrostatic chuck using the punching metal provided with a large number of small holes as an electrode is preferable.

Further, the silicon wafer is heated, and thereafter,
This is the case when it is used in the work of applying a CVD process, but the electrostatic chuck used in such a process has a built-in heater,
In many cases, the object to be adsorbed can be heated. Therefore, even in this case, an object to be adsorbed can be favorably adsorbed and a uniform temperature distribution can be obtained. Therefore, an electrostatic chuck using punching metal having a large number of small holes as an electrode is preferable.

In the electrostatic chuck according to the present invention, the punching metal forming the electrode is preferably made of a metal material containing tungsten or molybdenum, and particularly preferably a metal material containing them as a main component.
That is, the punching metal forming the electrode needs to be formed of a high melting point metal having a melting point higher than 2000 ° C., but not all high melting point metals have the same thermal expansion coefficient. Since the electrostatic chuck according to the present invention has aluminum nitride as a main component, the metal material forming the electrode also has a thermal expansion coefficient (relatively small thermal expansion coefficient) equivalent to that of aluminum nitride. It is desirable to have. Therefore, the electrode is preferably composed of tungsten or molybdenum which is a refractory metal satisfying these conditions.

For reference, the manufacturing method of the electrostatic chuck according to the present invention is roughly classified into the following two. The first is to place a punching metal to serve as an electrode on the surface of the compact (base layer) of the raw material powder containing aluminum nitride, cover it with the raw material powder containing aluminum nitride, and then perform hot press firing. Is the way to do it. The second is a method in which a punching metal serving as an electrode is placed on the surface of a sintered body containing aluminum nitride (a portion serving as a base layer), a raw material powder containing aluminum nitride is covered on the punching metal, and then hot press firing is performed. is there.

A sintering aid such as an oxide of a rare earth element may be added to the aluminum nitride powder used here. Further, various additives may be added in order to change the electrical characteristics, mechanical characteristics, color tone and the like. However, it is desirable that the amount of these added be such that the change in the thermal expansion coefficient can be suppressed to a negligible level. This is because, if the coefficient of thermal expansion changes significantly due to the additive, the part mainly made of aluminum nitride (chuck body) may be cracked when the punching metal to be the electrode is embedded and hot press firing is performed. is there.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, referring to FIG. 1 and FIG.
One embodiment of the present invention will be specifically described. 1 is a sectional view of the electrostatic chuck according to the present embodiment, and FIG. 2 is a partial plan view of the electrode.

The electrostatic chuck according to the present embodiment (hereinafter referred to as the present electrostatic chuck) is a semiconductor wafer, a flat display panel, a flexible substrate, or the like in a depressurized atmosphere, that is, in a depressurized manufacturing apparatus. It is used for temporarily adsorbing and holding an article (adsorbed object) when it is subjected to a predetermined process.

As shown in FIG. 1, this electrostatic chuck comprises a chuck body 1 and a flat plate-shaped electrode 2 embedded in the chuck body 1. Of these, the chuck body 1 is made of a sintered body containing aluminum nitride as a main component. More specifically, the chuck body 1
Is obtained by first forming a raw material powder containing aluminum nitride as a main component into a predetermined shape, and then hot-pressing it. In this embodiment, the chuck body 1 has a disk shape having a diameter significantly larger than the thickness, but the outer shape may be any shape.

The chuck body 1 comprises a base layer 11 and an insulating layer 12 which face each other with the electrode 2 interposed therebetween. In other words, the electrostatic chuck has a state in which the base layer 11, the electrode 2, and the insulating layer 12 are sequentially stacked. However, it goes without saying that the base layer 11 and the insulating layer 12 are integrated.
In addition, the thickness of the insulating layer 12 in contact with the object to be adsorbed (T in FIG. 1)
₁ ) is 0.1-4.0 mm.

In the present embodiment, the electrode 2 is made of flat plate punching metal. The punching metal forming the electrode 2 is made of a metal material whose main component is tungsten, which is a refractory metal having a thermal expansion coefficient substantially equal to that of aluminum nitride. However, instead of tungsten, a metal material whose main component is molybdenum, which is a refractory metal having a thermal expansion coefficient substantially equal to that of aluminum nitride, may be adopted.

The thickness of the electrode 2 (indicated by T ₂ in FIG. 1) is
0.05-2.00 mm, especially 0.05-1.00 mm
Is. Further, the punching metal forming the electrode 2 is
The porosity is 3.1 to 81.0%, particularly 3.1 to 7
It is 0.0%.

Furthermore, the punching metal used as the electrode material in this embodiment is obtained by forming a large number of circular holes 21 in a thin metal plate by punching, for example, as shown in FIG. In addition, in the figure, all the intervals (distance between centers) between the holes 21 shown by P are the same.
The angle θ ₁ formed by the two line segments L ₁ and L ₂ connecting the centers of the holes 21 closest to each other is 90 degrees. Therefore, the line segment _{L 1,} the angle theta ₂ between the line segment _{L 3} to make a right angle isosceles triangle with which the line segment _{L 2} becomes 45 degrees. The punching process is used to form holes in such a manner, and such a pattern is generally called “staggered punching”. In particular, in this case, since the hole is circular and the angle θ ₂ formed by the line segments L ₁ and L ₃ is 45 degrees, the pattern is called “round hole staggered 45 degrees”.

The electrostatic chuck further comprises a power supply terminal 3 for applying a voltage to the electrode 2. This terminal 3
Are inserted into through holes formed in the base layer 11 by post-processing and are connected to the electrodes 2. By applying a predetermined voltage to the electrode 2 by using this, the electrostatic chuck can electrostatically adsorb an object to be adsorbed on the surface of the insulating layer 12. That is, a state in which the object to be attracted is held and fixed by the electrostatic chuck can be obtained. Although not shown in the drawing, a heater is embedded inside the base layer 11 if necessary.

As described above, in the present embodiment, the electrode 2 embedded in the chuck body 1 made of aluminum nitride is used.
As for, use one made of punching metal,
The base layer 11 and the insulating layer 12 forming the chuck body 1 are
It was configured to be in direct contact with many points. For this reason, even if the thickness of the insulating layer 12 is small, in particular, it is 0.1-4.
Even if the thickness is 0 mm, the insulating layer 1 may be formed during processing or use.
No problems such as peeling of No. 2 occur. That is, this electrostatic chuck is excellent in workability and durability.

Furthermore, this electrostatic chuck does not have the problem as in the case where the electrodes are made of wire mesh. That is, in the wire net, since the contact condition between the metal wire rods forming the wire net is not uniform, the wire net locally causes an internal discharge, which unnecessarily raises the temperature. By the way, this lowers the volume resistivity and increases the adsorption force more than necessary, but if such a phenomenon becomes serious, the leakage current flowing to the object to be adsorbed, for example, the semiconductor wafer will exceed the limit value, and Problems such as destruction of the formed device occur.

However, when the electrode made of punching metal is used as described above, there is no increase in temperature due to internal discharge. Therefore, the temperature of the electrostatic chuck is always kept at a normal value, and therefore no trouble such as damage of the object to be attracted occurs.

During use, the temperature of the electrostatic chuck suddenly changes in a fairly wide range. At this time, due to the difference in coefficient of thermal expansion between aluminum nitride and the metal material forming the electrode, Generates stress. However, when the electrode is made of a wire mesh, the metal wire material forming the electrode is easily cracked, so that the electrode is easily broken. As a result, the electrostatic chuck using the wire mesh as an electrode cannot exhibit its original performance at an early stage, resulting in uneven adsorption. Then, the adsorption unevenness causes temperature unevenness on the adsorbed material, and significantly deteriorates the quality of the film formed on the surface of the adsorbed material.

On the other hand, in the electrostatic chuck using the electrodes made of punching metal as in the present embodiment, some cracks in the electrodes do not pose a problem. In other words, some cracks do not cause fatal defects such as wire breaks in the wire mesh, so even if the electrostatic chuck is used for a long period of time under conditions where the temperature changes rapidly over a wide range, There is no problem that the adsorption capacity decreases.

By the way, to be exact, as the electrode, as the punching metal used as the material of this electrode, those shown in FIGS.

The punching metal part of which is shown in FIG. 3 is also obtained by forming a large number of circular holes 31 in a thin metal plate, for example, by punching. In the figure,
The intervals (distance between centers) between the round holes 31 shown by P are all the same. The angle θ formed by the two line segments L ₁ and L ₂ connecting the centers of the adjacent circular holes 31 is 60 degrees. Such a pattern is particularly referred to as "round staggered 60 degrees".

FIG. 4 shows "90 degrees without circular holes in series".
One of punching metal that adopted a pattern called
And the space between the round holes 41 shown by P in the figure (center
The distances between them) are all the same. Also, the adjacent round holes 41 are the same.
Two line segments L that connect the center of the warrior ₁, L_TwoThe angle θ formed by
Needless to say, it is 90 degrees.

The one shown in FIG. 5 is called "square hole series removal".
Is part of the punching metal used
In the figure, the distance between the square holes 51 indicated by P (distance between centers)
Distance) is all the same. Also, between the adjacent square holes 51
Two line segments connecting the heart L₁, L _TwoThe angle θ formed by is 90 degrees
is there. The square holes are arranged as shown in Fig. 2 and Fig. 3.
The turn is especially called "Squard Staggered Hole". Furthermore, true
Oval holes or oval holes were used instead of circular holes.
In some cases, such patterns can be
It is called “staggered” or “long hole series without”.

[0054]

Example An electrostatic chuck according to the above embodiment was manufactured as follows. First, aluminum nitride powder and yttria (yttrium oxide) powder, which are raw materials, were prepared. Then, a mixture of 97% by mass of aluminum nitride powder and 3% by mass of yttria was formed, and the mixture was filled in a mold to obtain 9.8 MPa (about 100 kgf / c).
Uniaxial pressure treatment was performed at a pressure of m ² ). by this,
A disc-shaped molded body (portion to be a base layer) having a diameter of 200 mm and a thickness of 10 mm was formed.

Next, a circular thin metal plate having a diameter of 190 mm to serve as an electrode was placed on the disk-shaped compact. However, this thin metal plate is obtained by cutting a flat punching metal into a circular shape. Then, the raw material mixture formed previously was further filled in a predetermined thickness on the circular metal thin plate. Then, hot press firing was performed at 1900 ° C. for 2 hours while applying a pressure of 9.8 MPa (about 100 kgf / cm ² ) again to form a sintered body.

Here, the surface of this sintered body was observed and it was confirmed that no cracks were generated. In addition, the internal state of the soft X-ray apparatus was observed, and it was confirmed that the embedded electrode did not have a disconnection-like defect. After this, the sintered body was ground so that the thickness of the insulating layer was 1.0 mm. Finally, a hole having a diameter of 4 mm was formed in the base layer portion of the sintered body to expose the embedded electrode. Then, the terminals for power supply were connected to the electrodes thus exposed to obtain the final product, that is, the electrostatic chuck (sample) according to the above-described embodiment.

Since 14 kinds of punching metals having different patterns and materials were used, naturally, there were 14 kinds of electrostatic chucks as samples. Below, these are called Examples 1-14. Details of the punching metal used as the electrode in each example are shown in Table 1 below.

On the other hand, instead of the circular metal thin plate made of punching metal, a circular metal sheet made of wire mesh was arranged to manufacture an electrostatic chuck for comparison, apart from Examples 1 to 14. However, other conditions are the same as above. Since three kinds of wire nets having different wire rod diameters and mesh fineness (hereinafter referred to as patterns) were used, there are also three kinds of electrostatic chucks for comparison as samples. Below,
These are referred to as Comparative Examples 1 to 3. Table 1 also shows the details of the wire mesh used in each comparative example.

[0059]                                   Table 1   Specimen pattern Porosity Thickness Material Example 1 Round 90 1.0 / 5.0 3.1 0.05 Mo Example 2 Round 90 3.0 / 10.0 7.1 1.00 Mo Example 3 Square 90 6.3 / 12.0 27.6 1.50 Mo Example 4 Circle 60 8.0 / 12.0 40.2 2.00 W Example 5 Square 90 2.5 / 3.2 61.0 0.05 W Example 6 Round 90 4.0 / 10.0 / 12.0 63.2 1.50 Mo Example 7 Round 60 4.5 / 5.0 73.4 2.00 W Example 8 Square 90 4.5 / 5.0 81.0 1.00 W Example 9 Round 90 1.2 / 10.0 1.1 0.05 W Example 10 Square 90 7.5 / 8.0 87.9 2.00 W Example 11 Square 90 6.3 / 12.0 27.6 0.02 Mo Example 12 Round 60 4.5 / 5.0 73.4 2.50 W Example 13 Round 90 3.0 / 10.0 7.1 0.10 Ta Example 14 Round 60 4.5 / 5.0 73.4 1.00 Nb Comparative Example 1 0.03 / 150 plain weave W Comparative Example 2 0.05 / 100 plain weave Mo Comparative Example 3 0.10 / 100 plain weave W

Here, the "circle" in the pattern column is
The hole of the punching metal means that it is a round hole, while the "corner" in the same column means that it is a square hole. The two-digit numerical value located next to the "circle" or "corner" means the angle (in degrees) formed by the line segments connecting the centers of the adjacent holes. That is, the 90 degree one is the punching metal which is adopted the series punching.
Degree one is punching metal which adopted staggering.

The next set of numerical values "M / N" is
The size and spacing (pitch) of the holes are shown. More specifically, the numerical value corresponding to “M” is the diameter of the hole (when the hole is a round hole / unit is mm) or the length of one side of the hole (when the hole is a square hole / unit is mm). Indicates. However, in Example 6, since the punching metal in which two kinds of round holes having different diameters were formed was used, the numerical values showing the diameters were separated by the midpoint and are described side by side.

Next, regarding the numerical value corresponding to "N", this means the distance (unit: mm) between the center of a hole and the center of another hole closest to it. More specifically, the unit of porosity is% and the unit of thickness is mm. In addition, "Mo" in the column of material is molybdenum,
"W" means tungsten, "Ta" means tantalum, and "Nb" means niobium.

On the other hand, regarding the set of numerical values "X / Y" described in the pattern column of Comparative Examples 1 to 3, the numerical value corresponding to "X" is the wire diameter (unit: mm) of the metal wire material constituting the wire mesh. On the other hand, the numerical value corresponding to "Y" indicates the mesh size (unit is mesh).

All the electrostatic chucks obtained as described above (Examples 1 to 14 and Comparative Examples 1 to 3) were repeatedly subjected to a temperature cycle of 20 to 550 ° C. 100 times in total, and then the adsorption force was obtained. Was measured. The measuring method is as follows.

First, the volume resistivity of aluminum nitride is
Heat the electrostatic chuck until it reaches 1 × 10 ¹⁰ Ω · m,
After that, the diameter 30
A mm silicon wafer was adsorbed. However, the applied voltage is 1 kV. In addition, the position where the silicon wafer is attracted is located at the center of the electrostatic chuck, on a concentric circle with a diameter of 90 mm.
There are four points (every 90 degrees) and four points (every 90 degrees) on a concentric circle having a diameter of 180 mm.

Electrostatic adsorption at each point in such a situation
Measure the force (unit is N) and carry out based on the data
For each of Examples 1 to 14 and Comparative Examples 1 to 3,
The degree of uniformity of the electroadsorption force (unit:%) was calculated. Conclusion
The results are shown in Table 2 below. Note that this uniform
The degree of sex K is calculated by the following equation. K = (3δ / 2x_avg) X 100 δ = [Σ (x_i-X_avg)^Two/ N]^1/2 x_avg= (Σx_i) / N Where x_iIs the magnitude of electrostatic attraction at the i-th point,
n is the total number of points where measurements are performed (here, n = 9)
It

[0067]                                   Table 2 Degree of sample homogeneity Degree of sample homogeneity Example 1 1.3 Example 10 2.5 Example 2 1.1 Example 11 2.8 Example 3 1.0 Example 12 1.9 Example 4 0.9 Example 13 2.1 Example 5 1.2 Example 14 2.8 Example 6 1.2 Comparative Example 1 7.1 Example 7 1.3 Comparative Example 2 6.5 Example 8 1.5 Comparative Example 3 5.6 Example 9 2.2

[Evaluation] In any of the electrostatic chucks according to the embodiments of the present invention, as compared with Comparative Examples,
It shows a good degree of uniformity. Therefore, it can be seen that the adsorption ability is not biased and the object to be adsorbed can be adsorbed and held extremely uniformly. In particular, from Table 2, there is shown an electrostatic chuck using punching metal in a preferable mode as an electrode,
It can be seen that it has outstanding properties.

[0069]

According to the present invention, it is possible to obtain an electrostatic chuck which is less likely to cause defects even if the thickness of the insulating layer is small. In particular, even if the thickness of the insulating layer is 0.1 to 4.0 mm, an electrostatic chuck in which problems such as peeling of the insulating layer are unlikely to occur can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an electrostatic chuck according to an embodiment of the present invention.

FIG. 2 is a partial plan view of electrodes forming an electrostatic chuck according to an embodiment of the present invention.

FIG. 3 is a partial plan view showing another mode of the electrode.

FIG. 4 is a partial plan view showing another mode of the electrode.

FIG. 5 is a partial plan view showing another mode of the electrode.

[Explanation of symbols]

1 chuck body 2 electrodes 3 terminals 11 base layer 12 Insulation layer 21 holes

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tatsuya Shiogai             2-4-2 Daisaku Sakura City, Chiba Prefecture Pacific Semé             Central Research Institute F-term (reference) 5F004 BB22 BB29                 5F031 CA02 CA04 CA09 HA02 HA03                       HA18 HA37 MA30 NA05 PA11                       PA30

Claims (4)

[Claims] 1. A chuck body composed of a sintered body containing aluminum nitride, and an electrode embedded in the chuck body, wherein the chuck body has a base layer and a thickness which face each other with the electrode interposed therebetween. Is an electrostatic chuck having an insulating layer of 0.1 to 4.0 mm, wherein the electrodes are made of a flat plate punching metal. 2. The thickness of the electrode is 0.05 to 2.00 mm.
The electrostatic chuck according to claim 1, wherein: 3. The electrostatic chuck according to claim 1, wherein the punching metal forming the electrode has an opening ratio of 3.1 to 81.0%. 4. The electrostatic chuck according to claim 1, wherein the punching metal forming the electrode is made of a metal material containing tungsten or molybdenum.