JP2003086663A - Holder of article being processed, processing unit and ceramic susceptor for semiconductor manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable holder of an article being processed, a processing unit and a ceramic susceptor for semiconductor manufacturing device. SOLUTION: The holder 12 of an article being processed comprises a ceramic basic body 13 having electric circuits 3a, 3b, 14 and 15 and provided with screw holes, anchor members 22 and 25 screwed fixedly into the screw holes of the ceramic basic body 13, and power supply conductive members 4, 17 and 18 connected electrically with the electric circuits 3a, 3b, 14 and 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a workpiece holder, a processing apparatus, and a ceramics susceptor for a semiconductor manufacturing apparatus, and more specifically, a workpiece holder having high reliability and the workpiece holder. The present invention relates to a processing apparatus using a body and a ceramic susceptor for semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device manufacturing process, a film forming process or an etching process is performed on a semiconductor substrate which is an object to be processed. In a processing apparatus for processing such a substrate, a susceptor, which is a substrate holding structure for holding a semiconductor substrate during processing, is installed.

An example of such a conventional susceptor is disclosed in, for example, Japanese Patent Laid-Open No. 10-273371.
The above-mentioned Japanese Patent Laid-Open No. 10-273371 discloses a susceptor including a ceramic member in which a conductive member corresponding to a heater circuit for heating is embedded. In Japanese Patent Laid-Open No. 10-273371, an opening is formed in the ceramic member, and a metal member for supplying electric power to the conductive member is arranged inside the opening. The conductive member and the metal member are joined by using an active metal brazing material (hereinafter, also referred to as brazing material).
In Japanese Patent Laid-Open No. 10-273371, it is stated that a predetermined joining strength can be obtained by controlling the "flowability" of the brazing material with respect to the metal member.

As another example, Japanese Patent Laid-Open No. 11-120
No. 53, a susceptor including a ceramic member in which a conductive member corresponding to a heater circuit or the like is embedded is formed, and an opening is formed in the ceramic member, and the susceptor is made of metal for supplying electric power to the conductive member. It is disclosed that the member is arranged inside this opening. A conductive terminal is arranged on the bottom surface of the opening, and the conductive member and the metal member are electrically connected via this terminal. The metal member is fixed in the opening using a brazing material and is connected to the terminal. Also, in order to protect the metal member located inside the opening and containing molybdenum (Mo) or molybdenum alloy from the atmosphere (oxidizing atmosphere such as air), surround the metal member inside the opening. Atmosphere protector is placed in. JP-A-11-120
According to Japanese Patent Laid-Open No. 53-53, the metal member can be protected from the atmosphere by disposing such an atmosphere protector.

[0005]

However, the above-mentioned conventional susceptor has the following problems. That is, in the susceptor disclosed in Japanese Unexamined Patent Publication No. 10-273371, when a "lump" of brazing material occurs between the metal member and the surface of the ceramic member inside the opening, the brazing material and the ceramic member Due to the difference in the coefficient of thermal expansion with the ceramic (aluminum nitride) that constitutes the above, cracks occur in the ceramic member after brazing or when a heat cycle test is performed on the susceptor. As a result, the joint strength at the joint between the metal member and the ceramic member is significantly reduced. Further, there is a possibility that the susceptor may be broken from this joint portion, and there is a problem that reliability of the susceptor is significantly reduced.

Further, in the susceptor disclosed in Japanese Patent Laid-Open No. 11-12053, the atmosphere protector is joined to the metal member and at the same time the metal member is isolated from the atmosphere, so that brazing is performed at a plurality of locations. ing. However, if brazing is insufficient even at one of the brazed parts, or if cracks or the like occur in the brazed part due to heat history such as a heat cycle, atmospheric gas leaks to the metal member side. Will be done. For this reason, the metal member and the like are deteriorated (oxidized), and the reliability of the susceptor is also significantly reduced.

On the other hand, if the amount of brazing material used is reduced in order to suppress the occurrence of cracks in the brazed portion, there arises a problem that the bonding strength between the metal member and the ceramic member becomes low.

As described above, by suppressing the occurrence of cracks and the like and at the same time achieving sufficient bonding strength at the joint between the metal member and the ceramic member, the susceptor as a workpiece holder having high reliability. It has been difficult to realize the above.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly-reliable workpiece holder, a processing apparatus, and a ceramic susceptor for a semiconductor manufacturing apparatus. Is to provide.

[0010]

The object holder according to one aspect of the present invention is an object holder for holding an object, has an electric circuit, and has a screw hole formed therein. A ceramic base, an anchor member fixed by being screwed into a screw hole of the ceramic base, and a power supply conductive member connected to the anchor member and electrically connected to an electric circuit are provided.

With this configuration, the anchor member can be reliably connected and fixed to the ceramic base without using a brazing material, so that the joint strength at the joint between the anchor member and the ceramic base can be sufficiently increased. Further, by fixing the power feeding conductive member to the anchor member so as to be electrically connected to the electric circuit, it is possible to reliably supply power from the power feeding conductive member to the electric circuit.

Further, since no brazing material is used at the joint between the anchor member and the ceramic base, cracks in the ceramic base at the joint due to the difference in thermal expansion coefficient between the brazing material and the ceramics constituting the ceramic base. It is possible to prevent the occurrence of cracks. As a result, the reliability of the joint between the anchor member and the ceramic substrate can be improved. Therefore, the reliability of the object holder can be improved.

In the object to be treated holder according to the above aspect 1, the electric circuit is preferably a layer formed by a metallizing method utilizing a screen printing method.

In this case, since the screen printing method is used, it is possible to easily form an arbitrary pattern of the circuit pattern of the electric circuit. Therefore, the degree of freedom in selecting the circuit pattern of the electric circuit can be increased.

In the object holder according to the first aspect, the anchor member and the power feeding conductive member may be integrated.

In this case, the number of parts constituting the workpiece holder can be reduced. In the workpiece holder according to the above aspect, the anchor member may be provided with a screw hole for a conductive member, and the conductive member for power supply includes a screw portion that can be screwed into the screw hole for a conductive member. Good. The conductive member for power feeding may be connected to the anchor member by fixing the screw part of the conductive member for power feeding to the screw hole for the conductive member of the anchor member.

In this case, the conductive member for power feeding can be joined to the anchor member by the screw structure without using the brazing material. Therefore, it is possible to prevent the thermal stress from being generated due to the presence of the brazing material at the joint between the anchor member and the power supply conductive member. As a result, the reliability of the object holder can be further improved.

In the workpiece holder according to the first aspect, the anchor member and the power supply conductive member may be connected by brazing.

In this case, since the contact area between the anchor member and the power feeding conductive member can be increased, the contact resistance at the joint between the anchor member and the power feeding conductive member can be reduced.

In the object holder according to the first aspect, the electric circuit may include a part extending to the periphery of the screw hole of the ceramic substrate. The workpiece holder in the above aspect 1 may include a conductive connecting member arranged so as to be in contact with a part of the electric circuit,
The power supply conductive member may have a convex portion that comes into contact with the connection member when connected to the anchor member.

In this case, by adjusting the size and shape of the connecting member, the contact area between the connecting member and a part of the electric circuit and the contact area between the connecting member and the convex portion of the power supply conductive member can be made sufficiently large. It will be possible. As a result, it is possible to reduce the contact resistance of the path from the power supply conductive member to a part of the electric circuit. When supplying a current to an electric circuit, if the contact resistance of the above path is large, heat is generated at the connection portion. Then, such heat generation causes disturbance of the uniform heat distribution of the object-to-be-treated holder. However, according to the present invention, since the contact resistance can be reduced as described above, it is possible to suppress the above-mentioned disturbance of the heat uniformity.

In the workpiece holder according to the first aspect, the electric circuit may include an extending portion that comes into contact with the anchor member.

Here, the extending portion can be formed by, for example, applying a tungsten (W) paste to a predetermined region and then performing a metallizing method. In this case, it is not necessary to separately prepare the above connecting member. For this reason,
The structure of the workpiece holder can be simplified.

In the workpiece holder according to the above aspect, the electric circuit may include at least one selected from the group consisting of tungsten, molybdenum and alloys thereof.

Here, the above tungsten (W), molybdenum (Mo) and their alloys are all materials having a relatively small difference in coefficient of thermal expansion from the ceramic constituting the ceramic substrate. Therefore, if an electric circuit is formed from these materials (if the electric circuit is baked),
It is possible to suppress the occurrence of defects such as the warp of the ceramic substrate due to the presence of this electric circuit.

In the workpiece holder according to the above aspect, the anchor member is made of tungsten, molybdenum, or an alloy thereof, Kovar, copper-tungsten alloy, copper-.
It may contain at least one selected from the group consisting of molybdenum alloys and copper-nickel-iron-tungsten alloys.

Here, when tungsten (W) or molybdenum (Mo) and their alloys are used as the material of the anchor member, the electric circuit and the anchor are also formed by using these tungsten or molybdenum as the material constituting the electric circuit. The member and the member can be made of the same material (that is, materials having substantially equal coefficients of thermal expansion). Then, when the electric circuit and the anchor member come into contact with each other (for example, when electric power is supplied from the conductive member for power feeding to the electric circuit through the anchor member), at the joint between the electric circuit and the anchor member, Generation of thermal stress due to the difference in thermal expansion coefficient can be suppressed.

When at least one of Kovar, copper-tungsten alloy, copper-molybdenum alloy and copper-nickel-iron-tungsten alloy is used as the material of the anchor member, the anchor member and the electric circuit are joined. The step of performing can be performed at a relatively low temperature. Further, the coefficient of thermal expansion of each of these materials is close to that of ceramics. Therefore, when the temperature of the workpiece holder changes (for example, when the temperature of the workpiece holder rises and falls by using a heater circuit as an electric circuit), the anchor member and the ceramic substrate are separated from each other. The thermal stress generated in the contact portion can be reduced.

In the workpiece holder according to the above aspect, the power-supplying conductive member is made of tungsten, molybdenum, alloys thereof, Kovar, copper-tungsten alloy, copper-molybdenum alloy, copper-nickel-iron-tungsten alloy. It may contain at least one selected from the group consisting of

In this case, the power supply conductive member can be made of the same material as the anchor member. Further, the power supply conductive member is connected to the anchor member. Then, by selecting the same material as the material of the anchor member (relatively close in coefficient of thermal expansion) as the material of the conductive member for power supply, it is generated at the connecting portion between the conductive member for power supply and the anchor member. Thermal stress can be reduced.

In the object holder according to the first aspect, the ceramic substrate is aluminum nitride, silicon nitride,
It may contain at least one selected from the group consisting of aluminum oxide and silicon carbide.

Here, aluminum nitride (AlN) has sufficient durability against a corrosive atmosphere. In addition, the ceramic substrate using aluminum nitride has a lower probability of generation of particles as impurities than other materials. Therefore, if the object holder using aluminum nitride is used for the processing of the silicon wafer, the generation of particles inside the processing chamber is extremely small, and the reactive gas (corrosive gas) used for the processing is used. As a result, the object holder is not damaged, so that the silicon wafer can be stably processed. Further, since aluminum nitride has a high thermal conductivity, it is possible to realize a workpiece holder having excellent thermal uniformity.

Further, since silicon carbide also has a high thermal conductivity, it is possible to realize an object-to-be-processed holder having an excellent thermal uniformity like aluminum nitride.

Further, since aluminum oxide (Al ₂ O ₃ ) is relatively inexpensive as compared with other ceramics, its manufacturing cost can be reduced if it is applied to a workpiece holder.

Further, since silicon nitride (Si ₃ N ₄ ) has a high strength, by applying this silicon nitride to the object holder, it is possible to obtain an object holder having excellent heat cycle resistance.

In the object holder according to the above aspect, the electric circuit preferably includes at least one selected from the group consisting of a heater, an electrostatic attraction electrode, and a plasma forming electrode. Further, the electric circuit is a heater,
It may include at least two or more selected from the group consisting of an electrostatic attraction electrode and a plasma formation electrode.

A processing apparatus according to another aspect of the present invention is
The workpiece holder according to the above aspect 1 is provided.

As described above, by applying the workpiece holder having high reliability, it is possible to realize a processing apparatus capable of stably performing processing on an object to be processed such as a semiconductor substrate.

A ceramic susceptor for a semiconductor manufacturing apparatus according to another aspect of the present invention has the object-to-be-treated holding body according to the above-described aspect.

The ceramic susceptor for semiconductor manufacturing equipment is used under harsh conditions such as temperature rise and fall that require heat cycles. Then, by applying the object holder according to the present invention, it is possible to realize a ceramic susceptor for a semiconductor manufacturing apparatus having high reliability even under such a severe use condition.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts will be denoted by the same reference numerals and the description thereof will not be repeated.

(Embodiment 1) FIG. 1 is a schematic partial sectional view showing a processing apparatus using a holder according to the present invention. Figure 2
FIG. 2 is a partially enlarged schematic sectional view showing a joint between a heater circuit and an electrode wire in the holder shown in FIG. 1. Embodiment 1 of the holder according to the present invention will be described with reference to FIGS. 1 and 2.

With reference to FIGS. 1 and 2, a holder 12 as an object holder according to the present invention, which is arranged inside a chamber of a processing apparatus, is connected to a ceramic base 13 and a back surface side of the ceramic base 13. And a tubular member 16 that is formed. The holding body 12 is connected to a wall surface (not shown) of the chamber at a lower portion of the tubular member 16. Examples of the processing device include an etching device and a film forming device which are semiconductor manufacturing devices. In this case, the holder 12 has a function as a ceramic susceptor for semiconductor manufacturing equipment.

The ceramic base 13 includes a base 1 made of ceramics, an electrostatic attraction electrode 14 as an electric circuit embedded inside the base 1, a plasma electrode 15 and heater circuits 3a and 3b. . As the electric circuit, at least one or two or more of the electrostatic attraction electrode 14, the plasma electrode 15, and the heater circuits 3a and 3b may be formed. Openings 19 and 21 are formed on the back surface side of the ceramic base 13. A screw hole 5 is formed at the bottom of the opening 19, and a metal anchor 2 as an anchor member is screwed into the screw hole 5 to be fixed. It should be noted that in FIG.
9 is not shown.

A screw hole is also formed in the bottom of the opening 21, and a metal anchor 22 as an anchor member is screwed into the screw hole to be fixed. Further, another opening is formed at the center of the back surface of the ceramic substrate 13 so as to reach the back surface of the electrostatic attraction electrode 14. The anchor 25 is fixed to the other opening by being screwed. The upper surface of the anchor 25 is in contact with the electrostatic attraction electrode 14. Anchors 2, 2
Electrode wires 4, 17, and 18 as power supply conductive members are connected to 2 and 25, respectively, as described later. As a result, the electrode lines 1 are respectively attached to the electrostatic attraction electrode 14, the plasma electrode 15 and the heater circuit 3 as described later.
7, 18, and 4 are electrically connected. These electrode wires 4, 17, and 18 are arranged on the inner peripheral side of the tubular member 16.

As shown in FIG. 2, heater circuits 3a and 3b.
The electrode wire 4 and the electrode wire 4 are electrically connected via a metal anchor 2. That is, an opening 19 (see FIG. 1) is formed in the base 1 that constitutes the ceramic base 13, and a screw hole 5 for inserting and fixing the anchor 2 is formed in the bottom of the opening 19. A threaded portion 6 is formed on the side surface of the anchor 2 so as to be inserted into the screw hole 5. The anchor 2 is screwed and fixed in the screw hole 5 as described above.

An inner peripheral screw hole 7 for inserting and fixing the electrode end 8 of the electrode wire 4 is formed on the upper surface of the anchor 2. Then, the electrode end portion 8 of the electrode wire 4 is inserted and fixed in the screw hole 7 on the inner peripheral side of the anchor 2. A threaded portion having a threaded groove is formed on the side surface of the electrode end portion 8 so as to be inserted into the inner peripheral side screw hole 7.

A heater circuit 3b is formed so as to extend from the surface of the substrate base 1 to the upper surface of the anchor 2 so as to come into contact with the upper surface of the anchor 2 inserted and fixed in the screw hole 5. There is. As a result, the heater circuits 3a and 3b are electrically connected to the electrode 4 via the anchor 2 and the electrode end portion 8.

Further, as shown in FIG. 1, a screw hole is formed in the bottom of the opening 21 formed in the bottom surface of the ceramic base 13, and a metal anchor 22 is screwed into the screw hole to be fixed. ing. The anchor 22 is
Basically, it has the same structure as the anchor 2. The upper surface 24 of the anchor 22 inserted and fixed in the screw hole is in contact with the lower surface 23 of the plasma electrode 15. And anchor 2
An inner peripheral side screw hole is formed on a surface of the second member opposite to the upper surface 24. The electrode wire 17 is inserted into the screw hole on the inner peripheral side.
The end of is fixed by screwing. The ends of the electrode wires 17 have the same shape as the electrode ends 8 of the electrode wires 4. As a result, the plasma electrode 15 is electrically connected to the electrode wire 17 via the anchor 22 that contacts the lower surface 23 of the plasma electrode 15.

The other opening formed in the center of the back surface of the ceramic base 13 is a screw hole having a thread groove formed on the side surface thereof, and the metal anchor 25 is formed in the other opening (screw hole). Is fixed by screwing.
The anchor 25 has basically the same structure as the anchor 2. The upper surface of the anchor 25 inserted and fixed in the screw hole is in contact with the lower surface of the electrostatic attraction electrode 14. An inner peripheral threaded hole is formed on the surface of the anchor 25 opposite to the upper surface. The end of the electrode wire 18 is screwed into and fixed to the inner peripheral side screw hole. Electrode wire 18
The end portion of is the same shape as the electrode end portion 8 of the electrode wire 4. As a result, the electrostatic attraction electrode 14 is electrically connected to the electrode wire 18 via the anchor 25 that contacts the lower surface thereof.

Next, a method for manufacturing the holder 12 shown in FIGS. 1 and 2 will be briefly described. First, the ceramic substrate 13 on which the heater circuit 3a and the like are formed is prepared by using a conventional general method. After forming the opening 19 in a predetermined region of the base 1 that constitutes the ceramic base 13, the screw hole 5 for inserting and fixing the anchor 2 is formed in the bottom of the opening 19. Then, the metal anchor 2 whose outer peripheral portion is threaded is screwed into the screw hole 5 to be fixed. As a material of the anchor 2, tungsten (W), molybdenum (Mo), or the like can be used. In addition, in this anchor 2,
The inner peripheral side screw hole 7 is formed in the central portion as already described.

As described above, after the anchor 2 is screwed and fixed in the screw hole 5 of the base body 1, the screen printing method is used to electrically connect the heater circuit 3a and the metal anchor 2 to each other. Then, a tungsten (W) paste is applied on the area where the heater circuit 3b is to be formed. Then, the heater circuit 3b is formed by firing in a nitrogen atmosphere at a heating temperature of 1600 ° C. (using a so-called metallizing method). Although not shown, the heater circuit 3b is in a state of being electrically connected to another heater circuit 3a. As a result, the anchor 2 and the heater circuits 3a and 3b can be electrically connected. Thereafter, the electrode end portion 8 of the electrode wire 4 is screwed into the screw hole 7 on the inner peripheral side of the anchor 2 to be fixed, thereby obtaining the structure shown in FIG.

The connecting portion between the plasma electrode 15 and the electrode wire 17 is formed as follows. That is, the opening 21 is formed in a predetermined region of the base body 1 that constitutes the ceramic base body 13. A screw hole for inserting and fixing the anchor 22 is formed at the bottom of the opening 21. At this time, the screw holes are formed on the lower surface 23 of the plasma electrode 15.
Is formed so as to expose. And in this screw hole,
A metal anchor 22 having a threaded outer periphery is screwed in and fixed. At this time, the upper surface 24 of the anchor 22 is brought into contact with the lower surface 23 of the plasma electrode 15. As a material for the anchor 22, tungsten (W), molybdenum (Mo), or the like can be used. In this anchor 22, the inner peripheral side screw hole is formed in the central portion as already described. Then, the end portion of the electrode wire 17 is screwed into and fixed to the screw hole on the inner peripheral side to obtain the structure as shown in FIG.

The method of manufacturing the connection between the electrostatic attraction electrode 14 and the electrode wire 18 is basically the same as the method of manufacturing the connection between the plasma electrode 15 and the electrode wire 17 described above.
Further, the structure of the connecting portion between the plasma electrode 15 and the electrode wire 17 described above may be applied to the connecting portion between the electrostatic attraction electrode 14 and the electrode wire 18.

As the material for the anchors 2, 22, 25, Kovar, Cu-W alloy, Cu-Mo alloy, copper-nickel-iron-tungsten alloy, etc. can be used. When the above-mentioned conductor is used as the material of the anchor 2, the heater circuit 3a formed on the base body 1 and the anchor 2 are electrically connected to each other.
After the silver paste is placed on the region where b is to be formed by the screen printing method, the heating temperature is 90
Heat treatment is performed under the condition of 0 ° C. In this way, the heater circuits 3a and 3b and the anchor 2 can be electrically connected.

As described above, in the holder 12 shown in FIGS. 1 and 2, since the anchor 2 can be securely connected and fixed to the ceramic base 13 without using a brazing material, the anchor 2 and the ceramic base 13 can be connected to each other. The joint strength of the joint portion (also referred to as a connection portion) can be sufficiently increased. Further, by fixing the electrode wire 4 serving as a power supply conductive member to the anchor 2 so as to be electrically connected to the heater circuits 3a and 3b serving as electric circuits, the electrode wire 4 moves to the heater circuits 3a and 3b. And the power can be reliably supplied.

Further, the anchor 2 and the ceramic base 13
Since a brazing material is not used in the joint portion with the, it is possible to prevent the occurrence of cracks or breaks in the ceramic substrate 13 at the joint portion due to the difference in the thermal expansion coefficient between the brazing material and the ceramics constituting the ceramic substrate 13. As a result, the reliability of the joint between the anchor 2 and the ceramic base 13 can be improved.

In the holder 12 shown in FIGS. 1 and 2, the heater circuits 3a and 3b as electric circuits, the electrostatic attraction electrode 14 and the plasma electrode 15 are formed by the screen printing method in the step of forming the ceramic substrate 13. It is preferably formed by the metallization method described above. In this case, since the screen printing method is used, the heater circuit 3
a, 3b, electrostatic attraction electrode 14 and plasma electrode 1
An arbitrary pattern can be easily formed for the circuit pattern of No. 5. Therefore, the degree of freedom in selecting the circuit patterns of the heater circuits 3a and 3b, the electrostatic attraction electrode 14, and the plasma electrode 15 can be increased.

Further, in the holder 12 shown in FIGS. 1 and 2, the anchor 2 is formed with the inner peripheral side screw hole 7 as the screw hole for the conductive member, as described above. The electrode wire 4 also includes an electrode end portion 8 as a screw portion that can be screwed into the inner peripheral side screw hole 7. Then, the electrode wire 4 is connected to the anchor 2 by fixing the electrode end portion 8 of the electrode wire 4 to the inner peripheral side screw hole 7 of the anchor 2.

Therefore, the electrode wire 4 can be joined to the anchor 2 by a screw structure without using a brazing material. Therefore, it is possible to prevent thermal stress from being generated due to the presence of the brazing material at the joint between the anchor 2 and the electrode wire 4. As a result, the reliability of the holder 12 can be improved.

Further, in the holder 12 shown in FIGS. 1 and 2, the heater circuits 3a and 3b include the heater circuit 3b as an extending portion which comes into contact with the anchor 2. Therefore, since the electrode wire 4 and the heater circuits 3a and 3b can be electrically connected by the anchor 2, a member other than the anchor 2 (a connecting member for electrically connecting the electrode wire 4 and the heater circuits 3a and 3b). ) Need not be prepared separately. Therefore, the structure of the holder 12 can be simplified.

(Embodiment 2) FIG. 3 is an enlarged schematic partial cross-sectional view for explaining Embodiment 2 of the holding body according to the present invention. FIG. 3 corresponds to FIG. Embodiment 2 of the holder according to the present invention will be described with reference to FIG.

Referring to FIG. 3, the holder is basically the same as in FIG.
The holder has the same structure as that of the holders 2 and 2, but the structure of the connecting portion between the heater circuits 3a and 3b and the electrode wire 4 is different. That is, the opening 19 of the base body 1 (see FIG. 1)
Anchor 2 screwed into the screw hole 5 formed in the bottom of the
An opening portion 20 (counterbore portion) is formed in the central portion of the. The anchor 2 and the electrode wire 4 are electrically connected by the brazing material 9.

Even in this case, the same effect as the first embodiment of the holder according to the present invention can be obtained.

Further, since the anchor 2 and the electrode wire 4 are connected by brazing, the brazing material 9 is arranged between the anchor 2 and the electrode wire 4. As a result, the contact area between the anchor 2 and the electrode wire 4 increases, so that the contact resistance at the joint between the anchor 2 and the electrode wire 4 can be reduced.

The method of manufacturing the holder shown in FIG.
This is basically the same as the method for manufacturing the holding body shown in FIGS. That is, a ceramic substrate on which the heater circuit 3a and the like are formed is prepared by using a conventional general method. After forming an opening in a predetermined region in the base 1 that constitutes this ceramic base, a screw hole 5 for inserting and fixing the anchor 2 is formed in the bottom of this opening. Then, the metal anchor 2 having the screw portion 6 formed on the outer peripheral portion thereof is screwed into and fixed to the screw hole 5. In this anchor 2, the opening portion 20 is formed in advance in the central portion as already described.

Thereafter, a heater circuit 3b for electrically connecting the heater circuit 3a and the metal anchor 2 was formed by the same method as the holder shown in FIGS. Although not shown, the heater circuit 3b is in a state of being electrically connected to another heater circuit 3a.
After this, the ends of the electrode wires 4 are inserted into the openings 20 of the anchor 2. Then, the brazing material 9 causes the electrode wire 4 to open the opening 2
By being fixed inside 0, a structure as shown in FIG. 3 is obtained.

(Third Embodiment) FIG. 4 is an enlarged schematic partial cross-sectional view for explaining a third embodiment of the holder according to the present invention. FIG. 4 corresponds to FIG. A third embodiment of the holder according to the present invention will be described with reference to FIG.

Referring to FIG. 4, the holder basically has the same structure as the holder shown in FIGS. 1 and 2, but the structure of the connecting portion between electrode wire 4 and heater circuits 3a and 3b is different. ing. That is, as shown in FIG. 4, the anchor 2 having the same structure as the anchor 2 shown in FIG. 2 is screwed and fixed in the screw hole 5 formed in the base body 1. next,
A washer 11 made of a conductive material is arranged so as to surround the upper portion of the screw hole 5 and come into contact with the heater circuit 3b. The washer 11 is made of metal and has a donut-shaped appearance in which an opening having a substantially circular planar shape is formed in the central portion.

Then, the electrode wire 4 has an electrode end portion 8 having a threaded portion which can be screwed into the inner peripheral side screw hole 7 of the anchor 2, and the washer 11 located on the electrode end portion 8.
And a flange portion 10 capable of pressing. The electrode end portion 8 of the electrode wire 4 is screwed into the inner peripheral side screw hole 7 and fixed. At this time, the flange portion 10 presses the upper surface of the washer 11. As a result, the electrode wire 4 and the heater circuits 3a and 3b are electrically connected via the flange portion 10 and the washer 11. Even in this case, the same effect as that of the first embodiment of the holder according to the present invention can be obtained.

Further, in the holder 12 shown in FIG. 4, the heater circuits 3a and 3b as electric circuits are part of the heater circuit 3a, 3b extending to the periphery of the screw hole 6 of the base body 1 constituting the ceramic base body 13. 3b is included. Further, a washer 11 as a conductive connecting member is arranged so as to come into contact with the heater circuit 3b. Further, the electrode wire 4 is formed with a flange portion 10 as a convex portion that comes into contact with the washer 11 when connected to the anchor 2.

Therefore, by adjusting the size and shape of the washer 11, the washer 11 and the heater circuit 3 can be adjusted.
It is possible to sufficiently increase the contact area with b and the contact area between the washer 11 and the flange portion 10 of the electrode wire 4. As a result, from the electrode wire 4 to the heater circuit 3b
The contact resistance of the route to can be reduced. Heater circuit 3a,
When the current is supplied to 3b, if the contact resistance of the path is large, heat is generated at the contact portion. Then, such heat generation causes a disturbance in the thermal uniformity of the holder 12. However, in the holder 12 according to the present invention shown in FIG. 4, since the contact resistance can be reduced as described above, such a disturbance of the heat uniformity can be suppressed.

(Fourth Embodiment) FIG. 5 is an enlarged schematic partial cross-sectional view for explaining a fourth embodiment of the holder according to the present invention. FIG. 5 corresponds to FIG. A fourth embodiment of the holder according to the present invention will be described with reference to FIG.

Referring to FIG. 5, the holder is basically the same as in FIG.
The holder has the same structure as that shown in FIGS. 2 and 3, but the structure of the connecting portion between the electrode wire 4 and the heater circuits 3a and 3b is different. That is, the screw holes 5 formed in the base body 1
The anchor 2 formed as the same component as the electrode wire 4 is screwed in and fixed. The electrode wire 4 and the anchor 2 are integrally formed as one component. As the material of the anchor 2, tungsten or molybdenum can be used. The holder shown in FIG. 5 can also achieve the same effect as the holder according to the first embodiment of the present invention.

Further, since the anchor 2 and the electrode wire 4 are integrated, the number of parts constituting the holder 12 can be reduced.

The method of manufacturing the holder shown in FIG. 5 is basically the same as the method of manufacturing the holder shown in FIGS. That is, a ceramic substrate on which the heater circuit 3a and the like are formed is prepared by using a conventional general method. In the base 1 that constitutes this ceramic base,
After forming an opening in a predetermined area, a screw hole 5 for inserting and fixing the anchor 2 is formed in the bottom of this opening.
Then, the metal anchor 2 having the screw portion 6 formed on the outer peripheral portion thereof is screwed into and fixed to the screw hole 5. The anchor 2 is the same part as the electrode wire 4.

After that, the heater circuit 3b for electrically connecting the heater circuit 3a and the metal anchor 2 was formed by the same method as the holder shown in FIGS. As a result, the electrode wire 4 integrated with the anchor 2 and the heater circuits 3a and 3b can be electrically connected. In this way, the holder shown in FIG. 5 is obtained.

(Fifth Embodiment) FIG. 6 is an enlarged schematic partial cross-sectional view showing a fifth embodiment of a holder according to the present invention.
FIG. 5 corresponds to FIG. A fifth embodiment of the holder according to the present invention will be described with reference to FIG.

Referring to FIG. 6, the holder is basically the same as in FIG.
Although it has the same structure as the holder shown in FIG. 3, the structure of the connecting portion between the electrode wire 4 and the heater circuits 3a and 3b is different. That is, after forming the screw hole 5 in the base body 1, the metal washer 11 is arranged so as to come into contact with the heater circuit 3b arranged around the screw hole 5. The metal washer 11 has a donut-shaped appearance with an opening formed in the center. And this washer 1
The anchor 2 is inserted and fixed in the screw hole 5 through the opening in the central portion of 1. The anchor 2 is configured as the same part as the electrode wire 4. A flange portion 10 is formed on the upper portion of the anchor 2. This flange part 10
Are formed so that the washer 11 can be pressed. When a component in which the electrode wire 4 and the anchor 2 having such a shape are integrated is used, the anchor 2 is screwed into the screw hole 5.
By being screwed in, the flange portion 10 presses the washer 11. Therefore, the electrode wire 4 and the heater circuits 3a and 3b are electrically connected via the flange portion 10 and the washer 11. As a result, the same effect as the holding body shown in FIG. 4 can be obtained. Moreover, since the electrode wire 4 and the anchor 2 are integrated, the number of parts constituting the holder 12 can be reduced.

In the first to fifth embodiments of the present invention, the heater circuits 3a and 3b as electric circuits, the electrostatic attraction electrode 14 and the plasma electrode 15 are selected from the group consisting of tungsten, molybdenum and alloys thereof. It is preferable to include at least one of

Here, the above tungsten (W), molybdenum (Mo) and their alloys are all materials having a relatively small difference in thermal expansion coefficient from the ceramics constituting the ceramic base 13. Therefore, if the electric circuit is formed of these materials, it is possible to suppress the occurrence of defects such as the warp of the ceramic substrate 13 due to the existence of the electric circuit.

In the first to fifth embodiments of the present invention, the anchor 2 is made of tungsten, molybdenum, alloys thereof, Kovar, copper-tungsten alloy, copper-molybdenum alloy, copper-nickel-iron-tungsten alloy. It may contain at least one selected from the group consisting of

When tungsten (W) or molybdenum (Mo) and their alloys are used as the material of the anchor 2, the heater circuits 3a and 3b are also formed of these tungsten or molybdenum, thereby forming the heater circuits 3a and 3b. The anchor 2 can be made of a material having a substantially equal thermal expansion coefficient. When the heater circuit 3b and the anchor 2 are in contact with each other as in the first, second, and fourth embodiments of the present invention, due to the difference in the coefficient of thermal expansion at the joint between the heater circuit 3b and the anchor 2. It is possible to suppress the occurrence of thermal stress.

When at least one of Kovar, copper-tungsten alloy, copper-molybdenum alloy and copper-nickel-iron-tungsten alloy is used as the material of the anchor 2, the anchor 2 and the heater circuit 3a,
The step of joining with 3b can be performed at a relatively low temperature. Further, the coefficient of thermal expansion of each of these materials is close to that of ceramics. Therefore, when the temperature of the holding body 12 changes, the thermal stress generated in the contact portion between the anchor 2 and the ceramic base 13 can be reduced.

Further, in the first to fifth embodiments of the present invention, the electrode wire 4 is made of tungsten, molybdenum, and alloys thereof, Kovar, copper-tungsten alloy, copper-molybdenum alloy, copper-nickel-iron-tungsten alloy. It may include at least one selected from the group consisting of:

In this case, the electrode wire 4 can be made of the same material as the anchor 2. Therefore, the thermal stress generated at the connection between the electrode wire 4 and the anchor 2 can be reduced.

Further, in the first to fifth embodiments of the present invention, base body 1 constituting ceramics base 13 contains at least one selected from the group consisting of aluminum nitride, silicon nitride, aluminum oxide and silicon carbide. You can leave.

Aluminum nitride has sufficient durability against a corrosive atmosphere. Further, the ceramic base 13 using aluminum nitride has a lower probability of generation of particles as impurities than other materials. Therefore, the holder 12 using aluminum nitride for processing the silicon wafer
By using, the generation of particles inside the chamber for processing is extremely small, and the holding body 12 is not damaged by the reactive gas used for processing. Therefore, it is possible to stably process the silicon wafer. Further, since aluminum nitride has a high thermal conductivity, it is possible to realize the holding body 12 having excellent thermal uniformity. Further, since silicon carbide also has a high thermal conductivity, it is possible to realize the holding body 12 having excellent thermal uniformity as with aluminum nitride.

Further, since aluminum oxide is relatively inexpensive as compared with other ceramics, if it is applied to the holder 12, its manufacturing cost can be reduced. Further, since silicon nitride has high strength, by applying this silicon nitride to the holder 12, the holder 12 having excellent heat cycle resistance can be obtained.

[0090]

EXAMPLES In order to confirm the effects of the present invention, samples of the holder according to the present invention will be prepared below, and the adhesion strength of the connection between the heater circuit as an electric circuit and the electrode wire will be measured for each sample. At the same time, the durability was investigated by conducting a heat cycle test. The test method and the result will be described below.

First, raw material powders having the compositions shown in Table 1 below were prepared.

[0092]

[Table 1]

A slurry was prepared by adding a binder and a solvent to each of the raw material powders shown in Compositions 1 to 4 in Table 1 above and mixing them using a ball mill. A green sheet (also referred to as a sheet) was produced by forming four types of slurries composed of the raw material powders of Compositions 1 to 4 into a sheet shape using a doctor blade method.
Next, the produced green sheet was cut so that the dimension after sintering was a circle having a diameter of 350 mm. On the surface of the cut sheet, a tungsten paste to be a heater circuit was formed by a screen printing method so as to have a predetermined pattern. Next, a plurality of sheets were further laminated and arranged on the sheet coated with the tungsten paste to serve as the heater circuit.

Then, as another sheet, a sheet on which a tungsten paste to be a plasma electrode is applied by a screen printing method to have a predetermined pattern and a tungsten paste to be an electrostatic attraction electrode are screen printing method. A sheet coated so as to have a predetermined pattern was prepared. These other sheets were further laminated on the sheet coated with the tungsten paste to be the above-mentioned heater circuit. In this way
A laminated body of four types of sheets made of the respective raw materials of composition-1 to 4 was obtained. The laminated body was subjected to a degreasing treatment by heat treatment in a nitrogen atmosphere at a heating temperature of 700 ° C.

Next, the laminated body made of the raw material powder shown in the composition-1 of Table 1 was subjected to a sintering process in a nitrogen atmosphere at a heating temperature of 1800 ° C. Further, the sintering process was performed on the laminated body composed of the raw material powder shown in Composition-2 in Table 1 under the condition that the heating temperature was 1700 ° C. in the nitrogen atmosphere. The composition in Table 1-
The laminated body using the raw material powder shown in No. 3 was subjected to a sintering step in a nitrogen atmosphere at a heating temperature of 1600 ° C. Further, with respect to the laminated body using the raw material represented by the composition-4 shown in Table 1, the sintering step was performed under the condition that the heating temperature was 2000 ° C. in the nitrogen atmosphere. In this way, a ceramic substrate (susceptor) composed of each composition 1 to 4 was produced.

Next, openings were formed in the heater circuit, the electrostatic attraction electrode, and the plasma electrode constituting the electric circuit, at the power supply portions (connection portions with the electrode wires). A screw hole was formed by screwing the bottom of the opening.

Next, as shown below, a cylindrical member arranged on the back surface side of the ceramic substrate was prepared. First, each of the slurries having the compositions 1 to 4 shown in Table 1 was granulated by a spray drying method. Next, using this granular raw material, a cylindrical molded body was formed by a dry pressing method. This cylindrical molded body was subjected to a degreasing treatment in a nitrogen stream at a heating temperature of 700 ° C. Next, after performing degreasing treatment, a sintering process is performed on each of the molded bodies using the raw materials of Compositions 1 to 4 under the same conditions as the sintering process for producing a ceramic substrate. did.

After the sintering step, the finished cylindrical sintered body is machined so that the inner diameter is 50 mm, the outer diameter is 60 mm, and the axial length is 200 mm.
That is, a tubular member was manufactured.

Next, on one end face of this tubular member, Al
₂ O ₃ -Y ₂ O ₃ -AlN of the slurry was applied. And
The end surface coated with this slurry was brought into close contact with the back surface of the ceramic substrate. Then, heat treatment for joining the tubular member and the ceramic substrate is carried out under the same conditions as in the sintering step for producing each of the ceramic substrates having compositions-1 to 4. In this way, a joined body of the tubular member and the ceramic substrate is obtained. It should be noted that the heater circuit as an electric circuit, the electrode for electrostatic adsorption and the electrode for plasma, and the connection portion of the electrode wire for supplying electric power to these electric circuits from outside are all arranged on the inner peripheral side of the tubular member. It

Next, in the joined body of the cylindrical member and the ceramic substrate manufactured as described above, a predetermined process such as screwing a metal anchor into a screw hole formed in the ceramic substrate is carried out. , The electrode wire was connected to a heater circuit forming an electric circuit. As this connection method, Embodiments 1 to 1 of the present invention shown in FIGS.
The method shown in 5 was carried out. In this way, samples having the connection structures shown in the first to fifth embodiments of the present invention were produced. As the anchor, for example, the diameter is 6 mm, the height is 6 mm, and the pitch of the screw (outer peripheral screw) formed on the outer peripheral side wall is coarse, and the inner peripheral side screw hole (electrode) formed in the central portion of the anchor. A metal anchor having a diameter of 3 mm and a depth of 4 mm and a screw pitch of coarse thread can be used for the screw hole for fixing the wire.

Materials for the metal anchor include tungsten, molybdenum, kovar, Cu-W alloy, and Cu-.
Materials such as Mo alloy and Cu-Ni-Fe-W alloy were used. In addition, as a material of the electrode wire, tungsten, molybdenum, kovar, Cu-W alloy, Cu-Mo alloy, Cu
A -Ni-Fe-W alloy or the like was used. In this way
As shown in Tables 2 and 3, 48 kinds of samples were prepared.
Hereinafter, specific configurations of each sample are shown in Tables 2 and 3.

[0102]

[Table 2]

[0103]

[Table 3]

Referring to Tables 2 and 3, W, Mo, Cu-W, Cu- in the columns of anchor material and electrode material
Descriptions of Mo are tungsten, molybdenum, and
It means a copper-tungsten alloy and a copper-molybdenum alloy. Further, the description of “screw” in the column of the anchor / electrode connection structure indicates that the anchor 2 and the electrode wire 4 are connected by the screw structure as shown in the first or third embodiment. Further, the description “silver brazing” indicates that the anchor 2 and the electrode wire 4 are connected by brazing using the silver brazing material as shown in the second embodiment. Further, the description of “integrated structure” refers to a structure in which the anchor 2 and the electrode wire 4 are integrated as in the fourth or fifth embodiment of the present application.

Further, the description of "W paste" in the column of the anchor / electrical circuit connection structure is based on the metallizing method using the tungsten (W) paste as shown in the first, second or fourth embodiment of the present application. Shows a structure in which a heater circuit 3b as an electric circuit is formed so as to come into contact with the surface of the anchor 2. In addition, "W washer", "Au
The expressions "washer" and "Mo washer" indicate the structure using the washer 11 as shown in the third or fifth embodiment of the present application. The W washer indicates that a tungsten washer is used. Au washer and Mo washer are gold (Au) respectively
Indicates that a washer made of molybdenum or a washer made of molybdenum (Mo) is used.

Tables 2 and 3 show the measurement results of the adhesion strength of the power supply section and the results of the heat cycle test for each sample. The following method was used to measure the adhesion strength.

First, the ceramic substrate of each sample is fixed. Then, in this state, by pulling the electrode wire in the direction away from the ceramic substrate at a speed of 0.5 mm / sec, how much load can the connection portion between the electrode wire and the heater circuit of the ceramic substrate withstand? Was measured.

Further, the test conditions for the heat cycle test are as follows: after raising the temperature from room temperature to 800 ° C. in a nitrogen stream,
A test in which a cycle of cooling was repeated was performed. The rate of temperature increase during the test was 20 ° C./min, and the temperature was 8
The holding time in the state of 00 ° C (high temperature state) and the holding time in the state of being cooled to room temperature (room temperature state) are both 3
It was set to 0 minutes. Then, after repeating this heat cycle 1000 times for each sample, it was confirmed whether or not a crack was generated in the sample.

As can be seen from Table 2, in Samples 1 to 48, which are working examples of the holder according to the present invention, the adhesion strength of the power feeding portion (the load that the connecting portion could withstand) was 20 kg or more. From the above, it can be seen that all the samples of the examples of the present invention exhibit sufficient strength. Further, regarding the results of the heat cycle test, the sample which is an example of the holder according to the present invention showed sufficient cracking resistance even after the heat cycle as described above was repeated 1000 times and no sufficient cracking was observed. You can see that it has.

On the other hand, as comparative examples, the above-mentioned compositions-1 to 4 were used.
Using the slurry of No. 3, a ceramic substrate was prepared by the same method as the method of preparing the sample described above. However,
This ceramic substrate was simply drilled without forming a screw hole by screwing. Then, a cylindrical tungsten anchor was inserted inside the hole. Then, the side wall of the hole and the side wall of the anchor, and the side wall of the anchor and the heater circuit of the ceramic base were bonded by using the tungsten metallizing method. An electrode wire was joined to the anchor by brazing. In this way, a sample as a comparative example was prepared.

Then, the above-mentioned measurement of the adhesion strength and the heat cycle test were carried out on the sample as the comparative example. As a result, the adhesion strength (the load that the connecting portion was able to withstand) of the sample as the comparative example was 8 kg, which was lower than the adhesion strength of the sample of the holder according to the present invention. Also, in the heat cycle test,
Occurrence of cracks was observed in the sample of the comparative example.

The embodiments and examples disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiments and examples but by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

[0113]

As described above, according to the present invention, the brazing material is not used in the connection portion between the electric circuit and the electrode wire formed on the ceramic substrate constituting the workpiece holder,
Since the anchor having the screw structure is used, the strength of the connection portion can be sufficiently increased, and at the same time, the occurrence of defects such as cracks can be suppressed even when subjected to a heat cycle. For this reason, it is possible to obtain an object holder having high reliability. Further, by applying the workpiece holder according to the present invention, it is possible to realize a highly reliable processing apparatus and a ceramic susceptor for a semiconductor manufacturing apparatus.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view showing a processing apparatus using a holder according to the present invention.

FIG. 2 is a partially enlarged schematic cross-sectional view showing a joint between a heater circuit and an electrode wire in the holder shown in FIG.

FIG. 3 is an enlarged schematic partial cross-sectional view for explaining a second embodiment of the holding body according to the present invention.

FIG. 4 is an enlarged partial cross-sectional schematic view for explaining a third embodiment of a holder according to the present invention.

FIG. 5 is a partially enlarged schematic view for explaining a fourth embodiment of a holder according to the present invention.

FIG. 6 is an enlarged schematic partial cross-sectional view showing a fifth embodiment of a holding body according to the present invention.

[Explanation of symbols]

1 substrate base, 2,22,25 anchors, 3a, 3
b heater circuit, 4, 17, 18 electrode wire, 5 screw hole, 6 screw portion, 7 inner peripheral side screw hole, 8 electrode end portion, 9
Brazing material, 10 flange part, 11 washer, 12
Holding body, 13 ceramics base, 14 electrostatic attraction electrode, 15 plasma electrode, 16 tubular member, 20, 2
1 Opening, 23 Lower surface, 24 Upper surface.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kei Hiiragi             Sumitomo, 1-1 1-1 Koyokita, Itami City, Hyogo Prefecture             Electric Industry Co., Ltd. Itami Works F-term (reference) 5F004 AA16 BA00 BB18 BB22 BB26                       BB29                 5F031 HA02 HA03 HA17 HA18                 5F045 BB20 EB02 EB03 EK09 EM02                       EM05

Claims (13)

[Claims] 1. A workpiece holder for holding a workpiece, the ceramic substrate having an electric circuit and having screw holes, and a ceramic substrate fixed by being screwed into the screw holes of the ceramic substrate. An object-holding body, comprising: an anchor member; and a power-supplying conductive member that is connected to the anchor member and that is electrically connected to the electric circuit. 2. The electric circuit is a layer formed by a metallizing method using a screen printing method.
The object holder according to item 1. 3. The workpiece holder according to claim 1, wherein the anchor member and the power feeding conductive member are integrated. 4. A screw hole for a conductive member is formed in the anchor member, the conductive member for power feeding includes a screw portion that can be screwed into the screw hole for the conductive member, and the screw portion of the conductive member for power feeding. 2. The power-supplying conductive member is connected to the anchor member by fixing a wire to the screw hole for the conductive member of the anchor member.
Alternatively, the object holder according to item 2. 5. The workpiece holder according to claim 1, wherein the anchor member and the power feeding conductive member are connected by brazing. 6. The electric circuit includes a portion extending to the periphery of the screw hole of the ceramic base, and a conductive connecting member arranged to be in contact with a portion of the electric circuit. The conductive member for use has a convex portion that comes into contact with the connecting member when connected to the anchor member.
The object holder according to any one of 1. 7. The workpiece holder according to claim 1, wherein the electric circuit includes an extending portion that comes into contact with the anchor member. 8. The workpiece holder according to claim 1, wherein the electric circuit contains at least one selected from the group consisting of tungsten, molybdenum, and alloys thereof. 9. The anchor member comprises tungsten, molybdenum, and alloys thereof, Kovar, copper-tungsten alloy, copper-molybdenum alloy, copper-nickel-iron-.
The workpiece holder according to any one of claims 1 to 8, comprising at least one selected from the group consisting of tungsten alloys. 10. The conductive member for power supply is made of tungsten, molybdenum, alloys thereof, Kovar, or copper.
The workpiece holder according to any one of claims 1 to 9, comprising at least one selected from the group consisting of a tungsten alloy, a copper-molybdenum alloy, and a copper-nickel-iron-tungsten alloy. 11. The object to be treated according to claim 1, wherein the ceramic substrate contains at least one selected from the group consisting of aluminum nitride, silicon nitride, aluminum oxide and silicon carbide. Holding body. 12. A processing apparatus comprising the workpiece holder according to any one of claims 1 to 11. 13. A ceramic susceptor for a semiconductor manufacturing apparatus, which has the workpiece holder according to claim 1.