JP2967024B2 - Embedded electrode product and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buried electrode and a method of manufacturing the same.

[0002]

2. Description of the Related Art At present, an electrostatic chuck is used for transporting, exposing, forming a film, fine processing, cleaning, dicing, and the like of a semiconductor wafer. As such an electrostatic chuck,
The following are known: (1) A film-shaped electrode is screen-printed on a disk-shaped ceramic green sheet, another disk-shaped ceramic green sheet is placed so as to cover the film-shaped electrode, and press-formed. Sintered ones are known. However, when pressure is applied to the compact, the pressure inevitably becomes nonuniform, and the thickness of the dielectric layer of the electrostatic chuck becomes nonuniform, so that manufacturing is difficult and the yield is poor.

(2) In order to solve this problem, the present applicant has developed an electrostatic chuck 35 as schematically shown in FIG. That is, a disk-shaped dielectric plate 36 made of dense insulating ceramics and a disk-shaped support 37 made of insulating ceramics are prepared. The disc-shaped support 37 has a through hole 39. Then, a circular sheet made of a conductive bonding agent and a columnar terminal 16 are prepared. A circular sheet is sandwiched between the disk-shaped support 37 and the back surface of the dielectric plate 36. The cylindrical terminal 16 is inserted through the through hole 39. In this state, the assembly is subjected to a heat treatment, and as shown in FIG.
The dielectric plate 36 and the disc-shaped support 37 are joined by the conductive joining agent layer 38. Next, the dielectric plate 36 is polished to flatten the wafer suction surface 36a.

[0004]

However, in the case of (1), the thickness of the dielectric layer tends to be non-uniform due to manufacturing restrictions. This point will be supplemented. In a method of forming a printing electrode on a green sheet, laminating the green sheets and performing press molding and firing, variations in the thickness of the dielectric layer and poor adhesion occur inevitably in the press molding and firing steps. . That is, the position of the printing electrode inside the fired body has changed. Therefore, it is difficult to make the thickness of the dielectric layer uniform, no matter how precisely the surface of the dielectric layer is flattened after integral sintering. Further, in such a normal pressure sintering method, especially when the size becomes large, the denseness of the dielectric layer is reduced by 1%.
Therefore, it is difficult to secure the voltage of 00%, and the reliability from the viewpoint of preventing dielectric breakdown is reduced. Furthermore, since the electrodes are formed by a screen printing method, the resistance of the electrodes is relatively large. Therefore, it is difficult to improve the rising speed during the operation of the electrostatic chuck.

On the other hand, in the case of (2), the disk-shaped support 3
After molding and firing both of the dielectric plate 7 and the dielectric plate 36, the surfaces of the dielectric plate 36 and the dielectric plate 36 need to be ground by a grinding machine. is there. Moreover, it is necessary to join the two by sandwiching a circular sheet made of silver brazing or the like between them and performing a heat treatment. Therefore, grinding and adjustment of the thickness of the disk-shaped support 37 and the dielectric plate 36, and particularly a troublesome brazing process are required. Moreover, when the disc-shaped support 37 and the dielectric plate 36 are joined with a conductive joining agent such as silver solder, a joining surface always remains along the conductive joining agent layer 38. However, under conditions such as high vacuum, this joint surface causes dielectric breakdown.

SUMMARY OF THE INVENTION It is an object of the present invention to improve reliability in terms of preventing dielectric breakdown and short-circuit in an electrode embedded product, reduce the resistance value of the electrode, and improve the strength of the substrate, especially around the electrode. It is to improve.

[0007]

An embedded electrode product according to the present invention is an embedded electrode product comprising a base made of dense ceramics and an electrode embedded in the base. It is composed of a plate-like body provided with a large number of holes made of a planar metal bulk body, and a base body surrounding the electrode,
It is characterized by being an integral sintered product without a joining surface.

The present invention also relates to a method for manufacturing an electrode-embedded article comprising a base made of dense ceramics and an electrode embedded in the base, wherein the electrode is a planar metal bulk. The ceramic body and the electrode embedded in the ceramic body are subjected to hot press sintering while applying pressure in the thickness direction of the electrode. By tying, the base is made into an integrally sintered product without a joining surface, electrodes are embedded in the base, and ceramics are filled in the holes.

[0009]

According to the electrode-embedded product of the present invention, since the embedded planar electrode is made of a metal bulk, the electrode has a small resistance value. Supplementing this point, the screen-printed electrode has a thickness of at most several tens μm, so that the resistance value is inevitably increased.

In addition, since the substrate surrounding the electrodes is an integrally sintered product having no bonding surface, no discharge or dielectric breakdown can occur from the bonding surface even under conditions such as high vacuum where discharge is easy. Therefore, the reliability of the electrode embedded product is dramatically improved.
Moreover, since the electrode is formed of a plate-like body provided with a large number of holes made of a planar metal bulk body, and the ceramic powder flows around, the bonding strength of the ceramics on both sides of the plate-like body increases, The strength of the substrate is improved.

According to the manufacturing method of the present invention, a ceramic molded body in which a planar electrode made of a metal bulk body is embedded is subjected to hot press sintering while applying pressure in the thickness direction of the electrode. Thus, the embedded electrode product of the present invention can be manufactured. Moreover, since the number of manufacturing steps is small and there is no joining step such as brazing, it is suitable for mass production.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an electrode embedded product according to the present invention, an electric dust collector, an electromagnetic shield, a high-frequency electrode, and an electrostatic chuck are preferable. In particular, when the electrode embedded product is a high-frequency electrode, for example, the electrode is tungsten and the frequency is 13.56M.
In the case of Hz, the thickness of the electrode is desirably 430 μm or more.
However, it is difficult to form an electrode of this thickness by a screen printing method. When the electrode-embedded product is an electrostatic chuck or an electric dust collector, the response speed of the chuck and the dust collection can be improved by forming the electrode as a planar metal bulk body.

When the electrode-embedded article is an electrode-embedded article installed in a semiconductor manufacturing apparatus using a halogen-based corrosive gas, the following effects are obtained. In the electrostatic chuck as shown in FIG. 7, the film-like electrode 38 may be corroded by a halogen-based corrosive gas. Further, the film-like electrode 38
Is made of a wax containing a heavy metal, so that the semiconductor may be contaminated with heavy metal.

In this regard, according to the present invention, since the substrate surrounding the electrode is an integrally sintered product having no joining surface, corrosion of the electrode and contamination in the semiconductor manufacturing apparatus can be prevented. Electrode embedded products installed in a semiconductor manufacturing apparatus using a halogen-based corrosive gas include an electrostatic chuck and a high-frequency electrode.

As the ceramics constituting the substrate, nitride ceramics such as silicon nitride, aluminum nitride, boron nitride and sialon, silicon carbide and alumina-silicon carbide composite material are preferable. According to the study of the present inventors, silicon nitride is particularly preferable from the viewpoint of thermal shock resistance, and aluminum nitride is preferable from the viewpoint of corrosion resistance to halogen-based corrosive gases and the like.

However, aluminum nitride is a material that is particularly difficult to sinter. For this reason, it is difficult to obtain a sintered body having a high relative density particularly by the conventional normal pressure sintering method. Therefore, conventionally, a large amount of sintering aid has been contained in aluminum nitride powder to promote its sintering. However, particularly when installed in a semiconductor manufacturing apparatus, such a sintering aid or the like becomes an impurity and may cause semiconductor contamination.

In this respect, according to the present invention, the aluminum nitride powder is subjected to hot press sintering, so that even when the content of impurities in the aluminum nitride powder is 1% or less, an extremely high relative density exceeding 99% is obtained. Was able to be produced.

When the electrode embedded product is an electrostatic chuck and the electrostatic chuck is used in a semiconductor manufacturing apparatus, there are the following problems. Since ceramics have a characteristic that the volume resistivity decreases as the temperature increases, as the temperature increases, the current flowing through the adsorbed semiconductor wafer increases, and the semiconductor wafer may be damaged.

Accordingly, from the viewpoint of preventing damage to the semiconductor wafer, the volume resistivity of the substrate is 10 ¹¹ Ω · c.
m or more. In this regard, up to 60 more
In the case of a high temperature use of 0 ° C. or more, for example,
Those having a volume resistivity of 10 ¹¹ Ω · cm or more even at a high temperature range of 0 ° C. are preferable. In this regard, alumina,
Beryllia, magnesia, silicon nitride and boron nitride are preferred.

In the manufacturing method of the present invention, a planar electrode made of a metal bulk is embedded in the ceramic molded body. In this process, the following method can be exemplified. Method (1) A preform is manufactured, and the electrode is placed on the preform. Next, a ceramic powder is filled on the preform and the electrode, and is subjected to uniaxial press molding.

Method (2) Two flat molded bodies are manufactured by cold isostatic pressing, and an electrode is sandwiched between the two flat molded bodies. In this state, the two compacts and the electrode are hot pressed. In this method, the density of the compact is increased in advance by the cold isostatic pressing method, and the variation in the density in the compact is smaller than that in the method (1). Therefore, compared to the case of the method (1), the amount of shrinkage of the compact during hot pressing is small, and the variation after firing is small. As a result, the average withstand voltage of the substrate becomes relatively large.

This effect is extremely important especially when the electrode-embedded product is an electrostatic chuck. Because
For the reasons described above, the average dielectric strength voltage in the dielectric layer of the electrostatic chuck can be further increased, and the reliability thereof can be dramatically improved.

In this sense, the relative density of the compact obtained by the cold isostatic pressing method is 60%
It is most preferable to set the above.

Further, in the method of screen-printing an electrode on the surface of a molded article obtained by the cold isostatic pressing method, it is necessary to carry out a long degreasing step in a non-oxidizing atmosphere after printing. In this respect, the aspect in which the electrode is sandwiched between the compacts obtained by the cold isostatic pressing method is advantageous from the viewpoint of mass production since such a long degreasing step does not exist.

Further, when the electrode-embedded product is an electrostatic chuck, assuming that the electrode film is formed by screen printing, the electrode film is deformed during the hot pressing process, and as a result, the It is considered that a problem occurs in that the thickness of the dielectric layer in the above becomes uneven. In this regard, as in the present invention, by embedding an electrode made of a planar metal bulk body, deformation of the electrode can be prevented by the rigidity of the electrode during hot pressing, so that the thickness of the dielectric layer becomes uneven. Can be prevented. In particular, in the case of an electrostatic chuck, the thickness of this dielectric layer is important because it determines chuck performance. Further, the planar metal bulk body in the present invention may be formed, for example, as an integral planar shape as shown in FIGS. 3 and 6 without arranging a wire or a plate in a spiral or meandering shape. Means what you do.

Since the electrode is hot-pressed in the thickness direction, a plate-shaped electrode is preferable from the viewpoint of preventing distortion during hot pressing. This electrode is preferably formed of a high melting point metal in applications where the temperature rises to a maximum of 600 ° C. or higher. Such applications include electrostatic chucks for semiconductor manufacturing equipment.

Examples of such a high melting point metal include tantalum,
Examples include tungsten, molybdenum, platinum, rhenium, hafnium and alloys thereof. From the viewpoint of preventing semiconductor contamination, tantalum, tungsten, molybdenum,
Platinum and their alloys are preferred.

In particular, when the electrode is made of tungsten and the substrate is made of silicon nitride, since the two have significantly different coefficients of thermal expansion, a conventional method of forming a film by screen printing and sintering under normal pressure is used. In this case, integration was difficult due to mismatch of thermal expansion. In this regard, according to the manufacturing method of the present invention, it is possible to integrate even a combination of the base and the electrode having such a large difference in thermal expansion coefficient. This is because the compact is hot-pressed in the thickness direction of the electrode.

The form of the electrode is a planar electrode composed of a plate-like body having a large number of small holes, and since the ceramic powder flows around these, the bonding strength of the ceramics on both sides of the plate-like body increases. In addition, the strength of the base is improved.

As such a plate-like body, a punching metal or a wire net can be exemplified. However, when the electrode is made of a high melting point metal and is a punching metal, the hardness of the metal is high, so it is difficult to punch a large number of small holes on a plate made of the high melting point metal, and the processing cost is also low. Very high.

In this regard, if the electrode is a wire mesh, a wire made of a high melting point metal can be easily obtained, and if this wire is braided, a wire mesh can be manufactured. Therefore, manufacture of the electrode is easy.

When the form of the electrode is a thin plate,
Due to the difference in the coefficient of thermal expansion between the electrode and the substrate, a particularly large stress is applied to the peripheral portion of the electrode, and the stress may damage the substrate. However, when the electrode is a plate having a large number of small holes, the stress is dispersed by the large number of small holes.

The mesh shape and wire diameter of the wire net are not particularly limited. However, wire diameter φ0.03mm, 150 mesh ~
With a wire diameter of 0.5 mm and 6 mesh, it could be used without any problem. In addition, the cross-sectional shape in the width direction of the wire constituting the wire net may be various rolled shapes such as an elliptical shape and a rectangular shape in addition to the circular shape.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view schematically showing an electrostatic chuck. FIG. 2 is a perspective view showing a part of the electrostatic chuck shown in FIG. FIG. 3 is a perspective view showing the wire mesh 3. FIG. 4A is a schematic cross-sectional view for explaining a forming step in a uniaxial press die, and FIG.
FIG. 4 is a cross-sectional view showing a compact 15, and FIG. 4C is a cross-sectional view schematically showing an electrostatic chuck. FIG. 5 is a cross-sectional view showing a compact formed by the cold isostatic pressing method.

To manufacture the electrostatic chuck of this embodiment,
First, a press molding machine as shown in FIG. 4A is prepared.
The mold 10 is fitted to the lower mold 14 of the press molding machine. The ceramic powder is filled in the internal space 11 of the mold 10 and is uniaxially press-molded by the lower mold 14 and an upper mold (not shown) to produce a preform 12A. Preform 12
The wire net 3 is set on A. The wire net 3 is circular as shown in FIG.

Next, the ceramic powder 1 is placed on the wire mesh 3.
3 and the wire net 3 is buried. The powder 13 is uniaxially press-molded with an upper mold (not shown) to form a compact 15 shown in FIG. In the molded body 15, the preformed body 1
The wire mesh 3 is buried between 2A and the preform 12B. Next, the compact 15 is subjected to hot press sintering and a predetermined grinding process to obtain an electrostatic chuck main body shown in FIG.

In FIG. 4C, a ring-shaped flange 1c is provided on the side peripheral surface 1d of the substantially disk-shaped base 1, and an electrode 9 made of the wire mesh 3 is embedded inside the base 1. I have. A dielectric layer 4 having a predetermined thickness is formed on the installation surface 1a side of an object to be fixed such as a semiconductor wafer. A terminal 16 is buried on the support portion 8 side, and the terminal 16 is connected to the electrode 9. The end face of the terminal 16 is exposed on the back surface 1 b of the base 1.

In another method, ceramic powder 1
3 by a cold isostatic press, and flat plate-shaped moldings 17A and 17B as shown in FIG.
And manufacture. Next, the wire mesh 3 is sandwiched between the compacts 17A and 17B, and in this state, the compacts 17A and 17B are subjected to hot press sintering.

The electrostatic chuck shown in FIGS. 1 and 2 was manufactured by the method described above. First, as the ceramic powder 13, an aluminum nitride powder containing 5% by weight of yttria was used. Molding was performed by applying a pressure of 7 tons / cm ² by a cold isostatic press to produce two molded bodies 17A and 17B. The bulk density of each compact was 2.51 g / cm ³ .

A wire mesh 3 made of metallic molybdenum was prepared. The mesh of the wire mesh 3 is a rolled product having a diameter of 0.18 mm. This is sandwiched between the compacts 17A and 17B,
Hot press sintering was performed at 0 ° C. and 200 kg / cm ² .
Thereafter, the thickness of the dielectric layer is averaged 300 by machining.
It was set to μm. In the actual measurement, the thickness of the dielectric layer was 306
± 50 μm. Thereafter, a hole was made in the base from the back side by ultrasonic processing, and the terminal 16 was joined. Holes 2 for passing pins for elevating and lowering the semiconductor wafer were formed in four places on the base 1.

An operation test of this electrostatic chuck was performed. The electric wire 5 was connected to the terminal 16, the stainless steel weight 6 was installed on the installation surface 1 a, and the electric wire (ground wire) 5 was brought into contact with the stainless steel weight 6. These electric wires 5 were connected to a DC power supply 7. The stainless steel weight 6 was connected to a load cell 40 for load measurement. A voltage of 1 KV was applied, and the stainless steel weight 6 connected to the load cell 40 was pulled up in the direction of arrow A by the stepping motor 41. The attraction force was obtained by (load at the time when the load cell was peeled-weight of weight) / (cross-sectional area of the attraction surface of the weight). As a result, an adsorption force of 50 g / cm ² was obtained.

The relative density of the substrate 1 was 99.9% or more, and the minimum dielectric strength was 10 KV / mm in the plane of φ146 mm, and the average was 28 KV / mm.

On the other hand, the conventional electrostatic chuck made of normal pressure sintered aluminum nitride has the highest bulk density,
It was 9.0%. Further, in the plane of φ150 mm, the minimum withstand voltage is 3 KV / mm, and the average is 15 KV.
/ Mm.

FIG. 6 is a perspective view showing the punching metal 21.

The punching metal 21 is circular.
A large number of circular holes 21b are formed in a grid pattern in a circular flat plate 21a.

[0046]

As described above, according to the electrode-embedded product of the present invention, since the embedded electrode is formed of a sheet-like integrated metal bulk, the wire or plate is formed in a spiral shape. The resistance value of the electrode is smaller than that in the case of the meandering arrangement.

Moreover, since the substrate surrounding the electrodes is an integrally sintered product having no joint surface, no discharge or dielectric breakdown from the joint surface can occur even under conditions such as high vacuum where discharge is easy. Therefore, the reliability of the electrode embedded product is dramatically improved.

Further, since the electrode is formed of a plate-like body provided with a large number of holes made of a planar metal bulk body and the ceramic powder flows around, the bonding strength of the ceramics on both sides of the plate-like body is reduced. And the strength of the substrate is improved.

According to the manufacturing method of the present invention, a ceramic molded body in which an electrode made of a planar metal bulk is embedded is subjected to hot press sintering while applying pressure in the thickness direction of the electrode. Thus, the embedded electrode product of the present invention can be manufactured. Moreover, since the number of manufacturing steps is small and there is no joining step such as brazing, it is suitable for mass production.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an electrostatic chuck and a mechanism for measuring its chucking force.

FIG. 2 is a perspective view showing a part of the electrostatic chuck shown in FIG.

FIG. 3 is a perspective view showing a wire net 3;
9

FIG. 4A is a schematic cross-sectional view for explaining a forming step in a uniaxial press die, and FIG.
FIG. 5 is a cross-sectional view showing No. 5, and (c) is a cross-sectional view schematically showing an electrostatic chuck.

FIG. 5 is a cross-sectional view showing a compact formed by a cold isostatic pressing method.

FIG. 6 is a perspective view showing a punching metal 21.

FIG. 7 is a sectional view schematically showing an example of a conventional electrostatic chuck.

[Description of Signs] 1, 31 Base 1a, 31a Installation surface 3 Wire mesh 4 Dielectric layer 9 Electrode 12A, 12B
Molded body by uniaxial pressing 13 Ceramic powder
15 Molded body in which wire mesh 3 is embedded 16 Terminal 17
A, 17B Molded product by cold isostatic pressing 21 Punched metal

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-199755 (JP, A) JP-A-5-283513 (JP, A) JP-A-5-275434 (JP, A) JP-A-3-1997 108737 (JP, A) JP-A-63-194345 (JP, A) JP-A-64-460 (JP, A)

Claims (6)

(57) [Claims] An electrode-embedded product comprising a base made of dense ceramics and an electrode embedded in the base, wherein the electrode has a large number of holes made of a planar metal bulk. An electrode-embedded product comprising a plate-like body provided, wherein the substrate surrounding the electrode is an integral sintered product without a joining surface. 2. The method according to claim 2, wherein the electrode is a wire mesh.
The electrode embedded product according to claim 1. 3. The electrode embedded product according to claim 1, wherein said electrode is a punched metal. 4. The method according to claim 1, wherein said electrode-embedded product is selected from the group consisting of an electrostatic precipitator, an electromagnetic shield, a high-frequency electrode, and an electrostatic chuck. Electrode buried product as described. 5. The electrode embedded product according to claim 1, wherein said electrode embedded product is an electrode embedded product to be installed in a semiconductor manufacturing apparatus using a halogen-based corrosive gas. Item embedded electrode according to the item. 6. A method for manufacturing an electrode-embedded article comprising a base made of dense ceramics and an electrode embedded in the base, wherein the electrode is made of a planar metal bulk body. Hot press sintering is performed by applying pressure in the thickness direction of the electrode to a ceramic molded body and the electrode embedded in the ceramic molded body, which is formed of a plate having a large number of holes. A method for producing an electrode-embedded product, wherein the substrate is made into an integrally sintered product having no joining surface, the electrode is embedded in the substrate, and ceramic is filled in the hole.