JPH0870036A - Electrostatic chuck - Google Patents

Abstract

PURPOSE: To improve heat transfer characteristics and durability by fusing and joining the plates of an insulator and a dielectric by the layer of a joint metal which is laid out in electrode shape metallurgically. CONSTITUTION: An attraction mechanism part 1 of an electrostatic chuck consists of a three-layer structure where the plate of a dielectric ceramic 2 is joined and formed in one piece on the plate of an insulator ceramic while holding the layer of an electrode metal 4. Then, the plates of an insulator 3 and the dielectric 2 are melted and joined metallurgically by a layer 4 of a joint metal which is laid out in electrode shape. Also, the attraction mechanism part 1 of the electrostatic chuck is brazed on a pedestal 5 consisting of carbon material or the compound material of carbon. Further, in a structure where the attraction mechanism part 1 is applied to the pedestal 5, the electrode side surface of the mechanism part 1 and the exposed surface of the pedestal are coated with ceramic insulation covering 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck, and more particularly, to a structure of an electrostatic chuck that can be used in a wide temperature range from low temperature to high temperature and to prevent plasma discharge from wrapping around the electrostatic chuck. It is related to the structure that can be made.

[0002]

2. Description of the Related Art Electrostatic chucks are often used for adsorption and fixation when plasma processing semiconductor substrates. A dielectric ceramic disk is attached on a pedestal (typically aluminum) that is structurally excellent in heat conduction, and the back surface of the pedestal is water-cooled or heated to a constant temperature unless otherwise specified. ing. The required characteristics are that the adsorbability is not affected by temperature and the responsiveness and erasability of the adsorbing force, that is, the adsorbing force is generated quickly in response to the application of a voltage and disappears promptly when the voltage is cut off. To be done. These dielectric properties are very sensitive to temperature, so temperature changes in the dielectric part are not desirable. It is necessary to maintain a constant temperature at all times. In the current electrostatic chuck, since the pedestal metal and the dielectric ceramic are adhered with an adhesive, heat transfer is hindered at the adhesion part, and it is difficult to control the temperature. In addition, there is a problem that the adhesive part peels off during use. In addition, there is also a problem that this adhesion type electrostatic chuck cannot be used because the temperature of the substrate to be processed becomes considerably high especially in the plasma CVD process among the plasma processes. On the other hand, there is also a problem in that during plasma processing, plasma discharge reaches the side surface of the electrostatic chuck and the surface is damaged.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a new structure of an electrostatic chuck which has excellent heat transfer properties and durability and can be used from low temperatures to high temperatures. At the same time, the present invention aims to provide a new structure of an electrostatic chuck capable of preventing damage due to plasma wraparound.

[0004]

The above problems can be solved by the following means. That is, 1. The adsorption mechanism of the electrostatic chuck has a three-layer structure in which a dielectric ceramic plate is joined and integrated onto an insulating ceramic plate with an electrode metal layer sandwiched between the insulating ceramic plate and the dielectric ceramic plate. An electrostatic chuck, characterized in that the plates are metallurgically fused and bonded by a layer of bonding metal arranged in the shape of an electrode. 2. An electrostatic chuck characterized in that an adsorption mechanism portion of the electrostatic chuck has a structure brazed onto a pedestal made of a carbon material or a carbon composite material. 3. An electrostatic chuck having a structure in which an adsorption mechanism section is attached on a pedestal, characterized in that the side surface of the electrode of the mechanism section and the conductor portion of the exposed surface of the pedestal are covered with a ceramic insulating coating. Electrostatic chuck. 4. In an electrostatic chuck having a structure in which an adsorption mechanism is attached on a pedestal, an electrically insulating shell made of a ceramic material is fitted on the conductor of the electrode side surface of the mechanism and the exposed surface of the pedestal. Electrostatic chuck. 5. The adsorption mechanism portion of the electrostatic chuck is fitted into the concave portion of the concave insulator to seal the side surface of the electrode of the adsorption portion, and the insulator is attached in such a size as to seal the surface of the pedestal. An electrostatic chuck characterized in that

[0005]

In the electrostatic chuck, the electrode is always formed on the back surface of the dielectric ceramic regardless of whether it is a monopolar system or a bipolar system. The expression "adsorption mechanism part" used in the present invention means a part having a two-layer structure in which an electrode is formed on the back surface of a dielectric ceramic, or a part having a three-layer structure in which an insulating ceramic is further placed under the electrode. Is a general term. In the electrostatic chuck, the adsorption mechanism is usually attached to a pedestal made of a material such as AL with an adhesive. That is, the expression "suction mechanism section" in the present invention is a generic term for the portion above the pedestal. The present invention has a structure in which the suction mechanism section is brazed onto the pedestal regardless of whether it is a monopolar system or a bipolar system. In particular, a carbon material or a carbon composite material is used as this pedestal material. The adsorption mechanism is a ceramic structure, and the difference in thermal expansion becomes a problem when brazing this with the pedestal material. When AL is used as the pedestal material, thermal stress between the ceramic structure of the adsorption mechanism and the AL becomes a problem, and the ceramic is often destroyed. Also, since AL has a low melting point, the maximum operating temperature is 45
The limit is about 0 to 500 ° C. On the other hand, carbon materials, especially graphite, have excellent thermal conductivity and also excellent stress absorption, and the coefficient of thermal expansion can be changed within the range of 3 to 7 × 10 ^−6. The coefficient of thermal expansion can be matched. The heat resistance limit that can be used is 1000 ° C. or higher in a plasma treatment atmosphere. The carbon material, particularly graphite, is used as the pedestal material in the present invention in order to obtain a crack-free joint by utilizing the above-mentioned properties of graphite. In the range of silicon nitride, silicon carbide, aluminum nitride to alumina, it is possible to directly bond with graphite without using an intermediate layer, but if necessary, a soft metal intermediate layer for stress absorption, or for expansion coefficient relaxation The intermediate layer may be sandwiched. Further, in order to completely match the expansion coefficients, carbon may be mixed with metal or ceramic and used as a composite material. In the brazing of the adsorption mechanism portion and the pedestal material, the joint portion may be metallized in advance and then brazed, or the ceramic fusion-bonding brazing material may be directly brazed. The electrode of a normal electrostatic chuck is usually formed by a method such as sputtering, paste baking, and telefunken method, and this portion is adhered to the mating material with an adhesive. The metallization layer formed by the method (particularly the sputtering and telefunken method) may be used for brazing with the mating material, or the dielectric ceramic and the mating material may be directly brazed to form the brazing metal at this time. The portions may be electrodes.
That is, first, in the case of the bipolar method, the electrode needs to be insulated from the pedestal, so the electrode cannot be directly joined to the pedestal. In this case, the electrode and the pedestal are joined by sandwiching an insulating material. In other words, dielectric ceramics, electrodes, insulators,
This two-layer structure will be joined to the pedestal. There is also a structure in which a dielectric ceramic, an electrode, an insulator, and this three-layer structure are formed at the same time when the ceramic is sintered. In this case, the non-suction surface of this simultaneous sintered body is brazed to the pedestal. Just do it. The brazing may be performed by metallizing in advance, or may be performed directly. Note that the above-mentioned co-sintered body has a structure in which metallized metal (metal such as tungsten and molybdenum) powder is printed on a ceramic green sheet, and the printed surface is further covered with a green sheet for integral sintering. The post metallized metal is encapsulated in ceramic. On the other hand, in the case where the electrode is formed of the brazing metal, the dielectric ceramic is brazed to the insulating ceramic in the pattern of the electrode. This brazing may be performed by previously metallizing the dielectric ceramic and the insulating ceramic in the pattern of the electrode, and then brazing, or by directly brazing the pattern of the electrode with a ceramic fusible brazing material. . The brazing filler metal component of direct brazing is determined by the upper limit of the temperature used. 300-600 ℃,
Or when using at higher temperature, Cu, A
It is preferable to use a metal or alloy such as g, Ni, AL, or Si containing a trace amount to several percent of active metal. As the active metal, Ti, Zr, Nb, Ta, V, and other Ti group and V group elements, Cr, Mn, Y, AL, and the like, all of which are commonly used for this purpose, can be used. Cu, Ag, N
In addition to elements such as i, AL, and Si, In, Sn, Zn, Pb, Cd or other elements can be appropriately added for the purpose of melting point, hardness, elongation, corrosion resistance and the like. For applications below 300 ° C., so-called soft metals such as Sn, In and Al, or alloys thereof containing the above-mentioned active metals are preferable.
Here, the material of the insulating ceramics is preferably a material having a linear expansion coefficient similar to or equal to that of the dielectric ceramics. The same ceramic is used for the co-firing type. Next, in the case of the monopolar method, the two-layer structure body of the dielectric ceramic and the electrode is joined to the pedestal.
The joining may be performed by brazing to the pedestal after metallizing into an electrode shape by a conventional metallizing method. When forming an electrode with a brazing metal, the dielectric ceramic is brazed to the pedestal in the pattern of the electrode using a ceramic fusion-bonding brazing material. In the case of joining to the pedestal, as in the bipolar method, an intermediate layer may be inserted between the electrode metal and the pedestal and joined as necessary. The intermediate layer may be metal or ceramic. This ceramic may be an electrically insulating ceramic. As the carbon material used for the pedestal, a graphite material is preferable, and an isotropic carbon material is particularly preferable. Further, the pedestal is usually heated by water cooling or a heater for temperature control, but in the carbonaceous pedestal of the present invention,
In the case of water cooling, a water cooling groove may be formed in the pedestal to allow water to pass therethrough. In this case, in order to prevent water from penetrating into the pedestal, it is effective to coat (metallize) the side surface of the groove with metal. Alternatively, it is also effective to attach a metal foil to the side surface of the groove. Alternatively, it is also effective to embed a metal pipe for water cooling in the groove and braze it to the pedestal. Alternatively, another circulation cooling mechanism may be attached to the pedestal for cooling. Alternatively, the bottom surface of the pedestal may be brought into contact with the cooling mechanism for cooling. For heating, a heater may be embedded in the pedestal. In this case, it is effective to fill the gap with an inorganic material. Further, the pedestal may be attached to another heating mechanism. Also,
The bottom surface of the pedestal may be brought into contact with the heating mechanism for heating.

In the present invention, since the side surface (thickness portion) of the electrode metal of the adsorption mechanism is exposed to the outside air, this portion is exposed to the plasma atmosphere during the plasma processing and is damaged by the wraparound of the plasma. Sometimes. Also,
Even in the electrostatic chuck of the conventional structure, the side surface (thickness portion) of the electrode metal may be exposed to the outside air, and the pedestal is exposed to the outside air. Because of this, the exposed portions of the conductor are damaged by the plasma. To prevent damage, it is effective to coat the exposed portion with a ceramic insulating coating. It is also effective to fit an electrically insulating shell made of a ceramic material. In addition, the adsorption mechanism of the electrostatic chuck is fitted into the concave portion of the concave insulator to seal the side surface of the electrode of the adsorption mechanism, and the insulator is attached to the pedestal with a size that seals the surface of the pedestal. It is also effective to do. The above-described mechanism for preventing plasma damage is not limited to the electrostatic chuck having the structure of the present invention described above, and it is needless to say that it is effective for the conventional structure. As the ceramic insulating coating, it is effective to apply a powder of an electrically insulating ceramic such as aluminum nitride or alumina with an inorganic binder and cure it. As the inorganic binder, a usual inorganic binder can be used, but among them, those which generate alumina, silica, aluminum nitride and silicon nitride by heating are particularly preferable. Examples thereof include alumina sol, silica sol, colloidal silica, ethyl silicate, aluminum alkoxide, silicon alkoxide, metal polymer and the like. The electrically insulating shell made of a ceramic material covers the surface to be protected and protects this portion, and is formed and fired according to the shape of the surface to be protected. The material is most preferably alumina, silica, aluminum nitride, etc., and may be densely sintered or a pre-sintered body. In addition, the above-mentioned inorganic binder and powder are impregnated into the temporary sintered body and heated,
It may be cured and coated. The concave insulator is a ceramic sintered body having a concave portion, in which the adsorption mechanism of the electrostatic chuck is fitted to the concave portion to seal the exposed portion of the electrode metal, and the bottom surface of the concave portion corresponds to the width of the pedestal surface. The exposed surface of the pedestal is sealed by contact. In this case, the insulator is most preferably a ceramic sintered body such as alumina, silica, or aluminum nitride, a pre-sintered body, and the like. In the case of a calcined body, the above-mentioned inorganic binder and powder are impregnated and heated and cured. But it's okay. Through the above, there are no particular restrictions on the material of the ceramic insulator, but ceramics such as alumina, silica and aluminum nitride are the most preferable materials.

[0007]

【Example】

Example 1 Adsorption mechanism: SiC-based dielectric ceramic (φ150 ×
2t) is used. The electrodes are bipolar. Print the alloy powder of 76Ag-21Cu-3Ti on the back surface of the dielectric ceramic in a pattern of 20 μm on the electrode, and then φ150 × 2 on this surface.
The electrically insulating SiC ceramic plates of t were overlapped and heated in a vacuum (2 × 10 ⁻⁵ Torr) at 850 ° C. for 10 minutes to be bonded. The electrodes were taken out by inserting lead wires into two holes formed in the SiC plate and electrically connecting them. Pedestal: An isotropic graphite material having a thermal expansion coefficient of 4.5 × 10 ⁻⁶ was used and processed into a shape shown in FIG. In FIG. 1, 1
Is an adsorption mechanism part, 2 is a ceramic dielectric, 3 is an insulator ceramic, 4 is an electrode (a brazing metal), and 5 is a pedestal. <Joining of adsorption mechanism part and pedestal> 74Ag-18Cu is attached between the joint surface of the insulating ceramic of the adsorption mechanism part and the pedestal of graphite.
A 50 μm foil having a composition of −3Ti-5In was sandwiched and heated in a vacuum (2 × 10 ⁻⁵ Torr) at 830 ° C. for 10 minutes for bonding. <Results> No cracking or peeling was observed at the joint. Usage status An aluminum water cooling plate was brought into contact with the bottom surface of the pedestal to cool the pedestal. The plasma CVD process was used for a total of 1000 hours. The surface temperature of the dielectric ceramic during processing is about 4 at maximum.
The temperature rose to 00 ° C, but the joint (SiC ceramic mutual,
No peeling or cracking was observed between the adsorption mechanism and the pedestal). Example 2 Adsorption mechanism part: ALN ceramic is used as a dielectric ceramic (φ150 × 1t). The electrode is a single pole type. Pedestal: An isotropic graphite material having a thermal expansion coefficient of 4.5 × 10 ⁶ was used and processed into a shape shown in FIG. A groove for water cooling was formed on the bottom surface of the pedestal, and the surface of the groove was plated with Ni to 100 μm. During the groove processing, fins having the structure shown in FIG. 3 were formed in the flow direction to widen the heat transfer area. Figure 2
Here, 1 is an adsorption mechanism part, 2 is a ceramic dielectric, 4 is an electrode (metal of brazing material), 5 is a pedestal, and 6 is an insulating ceramic coating. In FIG. 3, 7 is a groove and 8 is a fin. <Joining the adsorption mechanism and the pedestal> Metal Si-on the joint surface of the pedestal
Powder of 10% Ti alloy is applied to a thickness of 300 μm, ALN ceramics are laid on top of this, and vacuum (5
X 10 ^-4 Torr), and heated at 1450 ° C for 10 minutes. There was no crack at the joint. <Polishing of ALN ceramic> When any insulator is thinned, electrostatic attraction is generated. In this example, the surface of the ALN ceramic was ground to a thickness of 100 microns for this purpose. <Formation of insulating coating> 1.2 parts by weight of alumina sol and ALN on the side surface of the brazing part of the ceramic and the pedestal and on the surface of the pedestal
About 100 μm of a paste prepared by mixing 2 parts by weight of the powder was applied, dried and then baked at 650 ° C. in an argon atmosphere for 3 hours to coat an ALN-AL ₂ O ₃ film. <Cooling of the pedestal> The water cooling groove was covered with an aluminum lid and sealed with an O-ring. <Results> Water was cooled by flowing water through the water-cooled groove of the pedestal. Example 1
As in the above, a total of 1000 hours was used for the plasma CVD process. The surface temperature of the dielectric ceramic during processing is about 400 at maximum.
Although the temperature rose to 0 ° C, no peeling or cracking was observed at the joint (the joint between ALN and the pedestal carbon). Moreover, no crack was observed in the ceramic portion. Moreover, the side surface of the electrode and the surface of the pedestal were prevented from being damaged by the plasma wraparound by the ceramic insulating film. Example 3 Adsorption mechanism part: Sapphire (φ150 × 0.2t). The electrode is a single pole type. Electrodes under sapphire, φ15 under electrodes
Three-layer structure of 0x0.2t alumina (high-purity alumina). Pedestal: An isotropic graphite material having a thermal expansion coefficient of 6.5 × 10 ⁻⁶ was used and processed into a shape shown in FIG. In FIG. 4, 1
Is an adsorption mechanism part, 2 is sapphire, 3 is alumina, 4 is an electrode (metal of brazing material), and 5 is a pedestal. <Bonding operation> The adsorption mechanism and the pedestal are joined in a single operation, and 50 μm of Sn-5Ag-5Ti powder is applied to the sapphire / alumina and alumina / pedestal joints, and the mixture is placed in a vacuum ( 2 × 10 ⁻⁵ Torr), 800
It joined by heating at 10 degreeC for 10 minutes. <Sapphire polishing> After bonding, a sapphire having a thickness of 0.2 mm was polished to 0.1 mm. <Results> No cracking or peeling was observed at the joint. Usage status An aluminum water cooling plate was brought into contact with the bottom surface of the pedestal to cool the pedestal. A total of 1000 hours was used for the dry etching treatment. During the treatment, the surface temperature of the dielectric ceramic rose to a maximum of about 100 ° C., but no peeling or cracking of the joint was observed. No cracks were observed on sapphire.

[0008]

EFFECT OF THE INVENTION 1. Can be used up to high temperatures. 2. The thermal stress of the ceramic joint is small and cracks do not occur. 3. Excellent heat transfer at the joint and uniform temperature distribution. 4. The adsorption part does not overheat.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a structure of an embodiment.

FIG. 2 is a diagram illustrating the structure of another embodiment.

FIG. 3 is a diagram illustrating a structure of a groove portion of FIG.

FIG. 4 is a diagram for explaining the structure of another embodiment.

[Explanation of symbols]

In FIGS. 1 to 3, 1 ... Adsorption mechanism 2 ... Ceramic dielectric 3 ... Insulator ceramic 4 ... Electrode (raw material metal) 5 ... Pedestal 6 ... Insulation ceramic coating 7 ... Groove 8 ... Fin In FIG. Mechanical part 2 ... Sapphire 3 ... Alumina 4 ... Electrode (raw material metal) 5 ... Pedestal

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01J 37/317 B 9508-2G H01L 21/265 21/027

Claims (5)

[Claims] 1. An electrostatic chuck chucking mechanism has a three-layer structure in which a dielectric ceramic plate is joined and integrated on an insulating ceramic plate with an electrode metal layer interposed therebetween. An electrostatic chuck characterized in that a body and a dielectric plate are metallurgically fused and bonded by a layer of a bonding metal arranged in an electrode shape. 2. An electrostatic chuck in which an adsorption mechanism portion of the electrostatic chuck has a structure brazed on a pedestal made of a carbon material or a carbon composite material. 3. An electrostatic chuck having a structure in which an adsorption mechanism section is attached to a pedestal, wherein an electrode side surface of the mechanism section and a conductor portion on an exposed surface of the pedestal are covered with a ceramic insulating film. An electrostatic chuck characterized in that 4. An electrostatic chuck having a structure in which an adsorption mechanism is attached on a pedestal, wherein an electrically insulating shell made of a ceramic material is provided on an electrode side surface of the mechanism and an electrically conductive portion on an exposed surface of the pedestal. An electrostatic chuck characterized by being fitted. 5. An electrostatic chuck having an adsorption mechanism portion fitted in a concave portion of a concave insulator to seal a side surface of an electrode of the adsorption mechanism portion, and a width at which the insulator seals a surface of a pedestal. An electrostatic chuck characterized by being attached by.