JPH08316298A - Electrostatic chuck - Google Patents

Abstract

PURPOSE: To resolve problems of a heat transmission check and turn-around of plasma discharge by a method wherein a metal material excellent in heat conductive characteristics is used as a pedestal material and an electrostatic attraction ceramic plate is directly or indirectly connected to this pedestal. CONSTITUTION: Pure aluminum is used in a pedestal 1 and a junction face is performed Ni plating. Alumina ceramic of 93wt.% Al2 O3 is employed in a ceramic cover 2 and an electrostatic attracting ceramic 3, and a portion of the electrostatic ceramic 3 is processed in a diameter 150 and a thickness 0.3mm. A thickness of cover ceramic is unequal and 0.2 to 7mm. 42Ni alloy intermediate layer 4 of a thickness 0.5mm for stress buffering is employed between the electrostatic attracting ceramic 3 and the pedestal metal 1. On a reverse face of the electrostatic attracting ceramic 3, copper-5%Ti is heated at 1200 deg. for 5 minutes and metallized and performed Ni plating. In solder is used for junction. Thus, problems of a heat transmission check and turn-around of plasma discharge can be resolved.

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 an electrostatic chuck using a metal pedestal, which has excellent cooling characteristics for an attracting surface and wraps around plasma discharge to an exposed metal surface of the pedestal. It is related to the structure that can completely prevent.

[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 with electrostatic adsorption properties is attached on a pedestal that is structurally excellent in heat conduction, and the back surface of the pedestal is normally cooled or heated to a constant temperature, except in special cases. Has been done. In many cases, the pedestal is made of a metal material having excellent thermal conductivity, and the pedestal and the ceramic are usually bonded with an organic adhesive. The outside of the ceramic is covered with a cover made of an insulating ceramic called an electrode cover to protect the surface of the pedestal metal exposed to the plasma atmosphere. However, the conventional structure has the following problems. One is the problem that heat transfer is obstructed at the adhesive part, and the other is the problem that plasma discharge wraps around from the gap between the dielectric ceramic disk and the electrode cover. If heat transfer is hindered at the bonding portion, the temperature of the treated substrate adsorbed on the surface of the electrostatic adsorption ceramic becomes high, and it becomes difficult to maintain the temperature at a uniform temperature. As a result, the plasma processing quality deteriorates,
Moreover, the quality is not uniform. Further, when the plasma discharge wraps around, not only the metal surface of the pedestal is damaged but also a DC voltage cannot be applied, which makes electrostatic adsorption difficult.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a static electricity of a new structure which can solve the above-mentioned problems of heat transfer inhibition and plasma discharge wraparound. It is intended to provide a chuck.

[0004]

The above problems can be solved by the following means. That is,

1. The electrostatic chucking ceramic of the electrostatic chuck and the insulating ceramic cover of the pedestal metal exposed to the plasma atmosphere are integrally formed, and the electrostatic chucking ceramic is directly or indirectly bonded to the pedestal metal. Characteristic electrostatic chuck.

2. 2. The electrostatic chuck according to 1, wherein the electrostatic chucking ceramic and the insulating ceramic cover are physically formed of the same kind of ceramic.

3. 2. The electrostatic chuck according to 1, wherein the electrostatic chucking ceramic and the insulating ceramic cover are made of different kinds of ceramics and are joined and integrated at a boundary portion.

4. 4. The electrostatic chuck according to 3, wherein the electrostatic attraction ceramic and the insulating ceramic cover are bonded by an inorganic composition.

5. 4. The electrostatic chuck according to 3, wherein the electrostatic attraction ceramic and the insulating ceramic cover are joined at the same time when the electrostatic attraction ceramic and the insulating ceramic cover are fired.

6. 6. The electrostatic chuck according to any one of 1 to 5, wherein the electrostatic adsorption ceramic and the base metal are joined by brazing.

7. The base metal has an electrostatic adsorption surface side and a plasma atmosphere exposed surface covered with a continuous insulating ceramic cover, and a ceramic layer having electrostatic adsorption properties is integrally formed on the surface of a portion corresponding to the electrostatic adsorption surface of the ceramic cover. And the back surface of the part is directly or indirectly bonded to the electrostatic attraction surface side of the entire base.

8. 8. The electrostatic chuck according to 7, wherein the ceramic cover and the base metal are joined by brazing.

[0013]

In the present invention, a metal material having excellent heat conduction characteristics is used as a base material, and the electrostatic chucking ceramic plate is intended for an electrostatic chuck of a type directly or indirectly bonded to the base.

The electrostatic adsorption ceramic and the insulating ceramic cover of the present invention have a continuous and integrated structure without any gap,
In this continuous body, both the electrostatic attraction ceramics and the insulating ceramic cover ceramics are made of the same ceramic material, and the electrostatic attraction ceramics and the insulating ceramic cover ceramics are made of different ceramic materials. When the ceramics are joined together without a gap at the boundary, and both the electrostatic adsorption surface side of the pedestal metal and the plasma atmosphere exposed surface are covered with a continuous insulating ceramic cover, the area corresponding to the electrostatic adsorption surface of the ceramic cover. When a ceramic layer having an electrostatic adsorption property is integrally formed on the surface of, there are three types.

When both the electrostatically attracting ceramic and the ceramic of the insulating ceramic cover are made of the same ceramic material The insulating ceramic cover is not only a material that is harmless to the semiconductor, but also has a high electrical insulating property. Required. On the other hand, electrostatic adsorption ceramics are literally required to have electrostatic adsorption properties, and it is often difficult to satisfy both characteristics with a single material at the same time. If it is thinned to the front and back, electrostatic adsorption will be exhibited. In other words, by making it thin, it is possible to bring out the characteristics of both electrical insulation and electrostatic adsorption with a single material. At this time, the electrically insulating portion may have the same thickness as the electrostatic adsorption portion, but it is more preferable to make it thicker. That is, it is more preferable to thicken the portion requiring high electric insulation and thin the portion requiring electrostatic attraction. As the material of the ceramic, alumina ceramic, sapphire, aluminum nitride ceramic, or a ceramic sintered body obtained by mixing alumina and aluminum nitride with other components can be preferably used. In this case, at least the portion of the electrostatic attraction surface is thinned to a thickness of about 0.1 to 0.4 mm. In the case of this example, there is an advantage that the whole can be formed of the same single material, but it is not necessarily limited to the formation of a single material, and the electric insulating portion and the electrostatic adsorption portion are formed of the same material. You may make it separately and join this without a gap. As for the joining, after firing each, an inorganic composition or an organic adhesive may be sandwiched between them to perform adhesive joining, or before firing, the boundaries may be overlapped in a raw state and integrally fired simultaneously. . The inorganic composition sandwiched between
Any composition can be used as long as it does not contain components harmful to semiconductors, that is, metal components such as alkali metals and alkaline earth metals. Among them, alumina sol, colloidal silica, Si alkoxide solution, metal component is S
Inorganic polymer solutions of i and AL can be preferably used. These solutions can be joined by applying the solution alone or in a mixture with the ceramic aggregate to the joint, and then firing the joints by stacking them together. The bonding temperature varies depending on the type of solution, but is generally 400
It may be in the range of up to 900 ° C. As the organic adhesive, an adhesive composed of a component that is not harmful to the semiconductor, such as a polyimide adhesive, is effective.

When the electrostatic attraction ceramics and the ceramics of the insulating ceramic cover are made of different kinds of ceramic materials, and the different types of ceramics are joined together without a gap at the boundary, the electrostatic attraction ceramics and the insulating ceramic cover are made of different ceramics. Created, the boundaries are joined together without any gaps. At this time, it is preferable to select a ceramic having substantially the same thermal expansion characteristics as the electrostatic adsorption ceramic and the ceramic of the insulating cover. The most preferable combination is a combination of ceramics whose main components are almost the same, such that if the ceramic of the insulating cover is an alumina type, the electrostatic adsorption ceramic is also an alumina type. For example, the insulating material is a combination of alumina, the electrostatic adsorption ceramic is sapphire, the insulating material is alumina, and the electrostatic adsorption ceramic is a combination of ceramics containing a small amount of a dielectric ceramic component such as alumina titanate in the alumina main component. A combination of different main components is a combination of silicon carbide and aluminum nitride. As the ceramic material to be used, as the electrostatic adsorption ceramic, any of the commonly used types such as alumina type, silicon carbide type, sapphire and aluminum nitride can be used. Similarly, materials such as alumina, silicon carbide, sapphire, aluminum nitride, and silicon nitride can be used for the insulating cover material.

The electrostatic adsorption ceramics and the insulating cover ceramics may be bonded to each other after firing by sandwiching an inorganic composition or an organic adhesive therebetween, or may be bonded before firing. In the state, the boundaries may be overlapped and integrally fired simultaneously. As the inorganic composition to be sandwiched, any composition can be used as long as it does not contain components harmful to semiconductors, that is, metal components such as alkali metals and alkaline earth metals. Among them, alumina sol, colloidal silica, Si alkoxide solution, metal component is Si,
An inorganic polymer solution of AL can be preferably used. These solutions can be joined by applying the solution alone or in a mixture with the ceramic aggregate to the joint, and then firing the joints by stacking them together.
The bonding temperature varies depending on the type of solution, but is generally 400-9
It may be in the range of 00 ° C. As the organic adhesive, an adhesive composed of a component that is not harmful to the semiconductor, such as a polyimide adhesive, is effective.

Both the electrostatic adsorption surface side of the pedestal metal and the plasma atmosphere exposed surface are covered with a continuous insulating ceramic cover, and a ceramic having electrostatic adsorption characteristics on the surface of the portion corresponding to the electrostatic adsorption surface of the ceramic cover. When the layers are formed integrally The entire pedestal metal is once covered with the insulating ceramic cover, and the ceramic layer having the electrostatic adsorption property is integrally bonded to the surface of the portion corresponding to the electrostatic adsorption surface of the ceramic cover. This is the case. It suffices that the ceramic cover is continuous without at least a gap, and is not necessarily formed of one ceramic. It may be formed separately and joined seamlessly. The seams are the same as above
After firing each, an inorganic composition may be sandwiched between them for adhesive bonding, or before firing, the boundaries may be overlapped in a raw state and integrally fired simultaneously. The same inorganic composition is suitable. As the material of the ceramic, as described in, a material such as an alumina-based material, a silicon carbide-based material, sapphire, aluminum nitride, or silicon nitride can be appropriately used.

A layer of a ceramic material having an electrostatic attraction property is integrally bonded to the surface of a portion corresponding to the electrostatic attraction surface of the ceramic cover. Here, as the ceramic material having the electrostatic adsorption property, the ceramics described in can be appropriately used. These ceramics are in the state of a thin plate of fired ceramic or a thin plate of single crystal ceramic, or on the surface of the ceramic cover. They are bonded together in the form of a coated ceramic membrane.

To integrally bond the fired ceramic thin plate or the single crystal ceramic thin plate to the surface of the ceramic cover, the fired ceramic thin plate or the single crystal ceramic thin plate is formed in the same manner as described above. It may be fired and bonded using an inorganic composition. Alternatively, both the ceramic cover and the electrostatic adsorption ceramic may be superposed in a raw state and co-fired to be combined. When connecting the ceramic cover and the electrostatic chucking ceramic, a film of a metal electrode may be formed on the back side of the electrostatic chucking ceramic in advance, and the film may be bonded to the ceramic cover in this state. In this case, in order to measure electrical conduction between the electrode film and the pedestal metal, a conduction hole may be bored in the ceramic cover, and conduction between the pedestal and the electrode film may be measured through this hole. The electrode film should not be formed on the entire back surface of the electrostatic adsorption ceramic, but should be kept inside a little, and the periphery of the electrostatic adsorption ceramic should be bonded to the ceramic cover without any gap so that the end of the electrode surface is not exposed. .

When an electrostatic adsorption ceramic layer is formed on the surface of the ceramic cover in the form of a ceramic film, a ceramic such as alumina or aluminum nitride is sputtered, and CV is used.
It can be formed by the D method. In this case, a thin electrode metal film may be formed in advance on the ceramic cover, and then the ceramic film may be formed thereon. In another method, powder for firing the electrostatic adsorption ceramic may be mixed with an inorganic binder that is harmless to the semiconductor and sintered. Inorganic metal polymer solutions of AL, Si alkoxide, AL, Si and the like can be preferably used.

The ceramic cover or the electrostatic adsorption ceramic and the pedestal metal may be basically joined by using an organic or inorganic adhesive, but metallurgical joining is most preferable. Metallurgical bonding is extremely effective in improving the heat transfer of the joint. The base metal is copper with excellent thermal conductivity,
Aluminum is used, and the coefficient of expansion of ceramic covers, electrostatically attracted ceramics, and pedestal metals differ significantly. Therefore, the ceramic may be cracked by thermal stress after joining. In this case, if the brazing material is a low melting point solder material, cracking can be avoided. It is also effective to sandwich a stress buffering intermediate layer in the joint. Mo, W, Ti, 4 in the middle layer
2 alloy, 42-6 alloy, Ni or WC-Co,
TiC-Ni cermet etc. can be used conveniently. At the time of joining, the ceramic and the intermediate layer and the intermediate layer and the pedestal are brazed. As the brazing alloy, silver braze, aluminum braze, solder, or active metal braze can be appropriately used.

[0023]

【Example】

Example 1 (integrated with the same material) The electrode was a monopolar pedestal: pure aluminum was used and processed into the shape shown in FIG. The joint surface was plated with Ni. The cover ceramic and the electrostatic adsorption ceramic were the same alumina-based ceramics and were manufactured in the shape shown in FIG. The electrostatic adsorption ceramic part was processed to a thickness of 150 mm x 0.3 mm. The thickness of the cover portion is unequal as shown in the figure, but is 0.2 mm at the thinnest portion and 7 mm at the thickest portion. The composition (wt%) of the ceramic was such that AL ₂ O ₃ : 93TiO ₂ : 1.2 SiO ₂ : 5.8 ceramic and the base metal were sandwiched with a stress buffering intermediate layer interposed therebetween. 42N of φ150 × 0.5mm for the middle layer
A plate of i alloy was used. For the bonding, first, Cu-5% Ti alloy powder was applied to the back surface of the electrostatic attraction portion of the ceramic and heated in vacuum (2 × 10 ⁻⁵ Torr) at 1200 ° C. for 5 minutes to perform metallization. Metallized thickness is about 10 microns. The metallized surface was further plated with Ni (20 μm). The ceramic and the 42Ni alloy plate, the 42Ni alloy plate and the pedestal were both brazed with In solder. In FIG. 1, 1 is a pedestal, 2 is a cover ceramic, 3 is an electrostatic attraction unit, 4 is 4
2Ni alloy plate. The base 1 is a cover ceramic 2
The surface is covered with and is brazed with the intermediate layer in between. <Results> No cracking or peeling was observed at the joint. Status of use It was possible to apply a DC voltage directly to the pedestal to electrostatically adsorb the silicon wafer. Actually used for etching process of silicon wafer and tested for a total of 3000 hours,
Neither the trouble that electrostatic attraction became impossible due to the invasion of plasma nor the surface damage was observed at all. In addition, this structure is much better cooled than the structure in which the electrostatic adsorption ceramic and the pedestal are bonded with an adhesive, and under the same operating conditions, a temperature drop of about 50-80 ° C is observed. Was given.

Example 2 (Joining of dissimilar materials) Electrode is a single pole type pedestal: Pure copper was used to form the shape shown in FIG. Electrostatically attracting ceramic: φ100 mm with the shape shown in FIG.
× Alumina-based dielectric ceramic with a thickness of 2 mm is used. A φ100 × 0.5 mm Mo plate was used for buffering the stress, and was directly brazed to the electrostatic adsorption ceramic. As the brazing material, a brazing material of Ag-22% Cu-5% Ti alloy was used, which was heated in a vacuum (1 × 10 ⁻⁵ Torr) at 850 ° C. for 5 minutes for bonding. Joining of pedestal and Mo plate: Ni plate (1
0 micron), and an In—Ag alloy solder was used as the brazing material and joined to the pedestal. Ceramic cover: A high-purity alumina ceramic was used to finish the shape shown in FIG. As shown in FIG. 2, the seam between the electrostatic adsorption ceramic and the ceramic cover has a stepped shape and is fitted into the seam, and they are joined with a polyimide adhesive. In FIG. 2, 1 is a pedestal, 2 is a cover ceramic, 3 is an electrostatic adsorption ceramic, and 5 is a Mo plate. <Results> Cracks on the brazed part and the polyimide adhesive part,
No peeling was observed. Status of use It was possible to apply a DC voltage directly to the pedestal to electrostatically adsorb the silicon wafer. Although it is actually used for etching processing of silicon wafers and tested for a total of 1000 hours,
Neither the trouble that electrostatic attraction was impossible due to the plasma invasion nor the surface damage was observed at all. In addition, this structure is much better cooled than the conventional structure in which the pedestal is adhered to the dielectric ceramic with an adhesive,
It was confirmed that the temperature of the ceramic surface decreased by about 70 ° C.

Example 3 (laminated type) The electrode was a unipolar type pedestal: pure aluminum was used and processed into the shape shown in FIG. The joint surface was plated with Ni. The cover ceramic covering the entire surface of the pedestal was made of alumina ceramic and formed into the shape shown in FIG. Thickness of cover ceramic: The portion (φ100 mm) to which the electrostatic adsorption ceramic is coupled has a thickness of 1 mm. The electrostatic adsorption ceramic was φ100 mm × 1 mm, and was made of the same composition as in Example 1. The cover ceramic and the electrostatic adsorption ceramic were bonded using alumina sol. That is, a mixture of alumina sol and alumina powder was applied to the joint portion and heated at 1000 ° C. for 1 hour for adhesion. The cover ceramic and the pedestal are joined by electroless Ni plating (15 micron) on the joint surface and φ100 in the intermediate layer.
It was joined to the pedestal using a plate of 42 Ni alloy of 1 mm. In-Sn solder was used for joining. In FIG. 3, 1 is a pedestal, 2 is a cover ceramic, 3 is an electrostatic adsorption ceramic,
4 is a 42Ni alloy plate. <Results> No cracking or peeling was observed at the joint. Status of use It was possible to apply a DC voltage directly to the pedestal to electrostatically adsorb the silicon wafer. Although it is actually used for etching processing of silicon wafers and tested for a total of 1000 hours,
Electrostatic adsorption was continued continuously, and no troubles due to plasma intrusion were observed. In addition, this structure is cooled much better than the structure in which the electrostatic adsorption ceramic and the pedestal are bonded with an adhesive, and the temperature drop of the ceramic surface is recognized by about 30 to 50 ° C under the same use condition. Was given.

Example 4 (Layered type) The electrode was a unipolar type pedestal: pure aluminum was used and processed into the shape shown in FIG. A cover ceramic having a shape covering the entire surface of the pedestal was made of alumina ceramic in the shape shown in FIG. Thickness of cover ceramic: The portion (φ100 mm) to which the electrostatic adsorption ceramic is coupled has a thickness of 1 mm. The electrostatic adsorption ceramic is φ100mm × 0.3mm,
Made with sapphire. An electrode film having a diameter of 90 mm was formed on the back surface of sapphire. For the electrode film, chromium was sputtered by 0.5 μm. The cover ceramic and sapphire were bonded using alumina sol. That is, a mixture of alumina sol and alumina powder is applied to the joint portion to obtain 900
It adhered by heating at 0 degreeC for 1 hour. The cover ceramic and the pedestal were bonded together with an epoxy adhesive, and the chrome electrode film and the pedestal were electrically connected to each other by filling a conductive hole formed in the cover ceramic 2 with a conductive epoxy adhesive. In FIG. 4, 1 is a pedestal, 2 is a cover ceramic, and 3 is an electrostatic adsorption ceramic (sapphire). <Results> No cracking or peeling was observed at the joint. Status of use It was possible to apply a DC voltage directly to the pedestal to electrostatically adsorb the silicon wafer. Although it is actually used for etching processing of silicon wafers and tested for a total of 1000 hours,
Electrostatic adsorption was continued continuously, and no troubles due to plasma intrusion were observed.

[0027]

As described above in detail, according to the present invention, it is possible to prevent the trouble of electrostatic adsorption and the damage of the pedestal metal due to the invasion of plasma, and at the same time, the ceramic surface is cooled very effectively and the etching characteristics The film forming characteristics have extremely excellent characteristics and make a great contribution to the improvement of the quality of semiconductor substrate processing.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a structure of an embodiment when the same ceramic material is used.

FIG. 2 is a diagram illustrating a structure of an embodiment in which different kinds of ceramics are integrally bonded and used.

FIG. 3 is a diagram illustrating a structure of an embodiment when different kinds of ceramics are laminated and integrated.

FIG. 4 is a diagram illustrating a structure of an embodiment in which different kinds of ceramics are laminated and integrated.

[Explanation of symbols]

 1 ... Pedestal 2 ... Ceramic cover 3 ... Electrostatic adsorption ceramic 4 ... 42 Ni alloy plate 5 ... Mo plate

Claims (8)

[Claims] 1. An electrostatic chuck ceramic of an electrostatic chuck and an insulating ceramic cover on a surface of a pedestal metal exposed to a plasma atmosphere are integrally formed, and the electrostatic chuck ceramic is directly or indirectly bonded to the pedestal metal. An electrostatic chuck characterized by being formed. 2. The electrostatic chuck according to claim 1, wherein the electrostatic chucking ceramic and the insulating ceramic cover are integrally formed of the same kind of ceramic. 3. The electrostatic chuck according to claim 1, wherein the electrostatic chucking ceramic and the insulating ceramic cover are made of different kinds of ceramics and are joined and integrated at a boundary portion. 4. The electrostatic chuck according to claim 3, wherein the electrostatic chucking ceramic and the insulating ceramic cover are bonded by an inorganic composition. 5. The electrostatic attraction ceramic and the insulating ceramic cover are joined at the same time when the electrostatic attraction ceramic and the insulating ceramic cover are fired.
The electrostatic chuck described in. 6. The electrostatic chuck according to claim 1, wherein the electrostatic chucking ceramic and the base metal are joined by brazing. 7. A base metal is provided with a continuous insulating ceramic cover on the electrostatic adsorption surface side and the plasma atmosphere exposed surface, and the surface of a portion corresponding to the electrostatic adsorption surface of the ceramic cover has electrostatic adsorption characteristics. An electrostatic chuck, wherein a ceramic layer is integrally formed, and a back surface of the portion is directly or indirectly bonded to an electrostatic attraction surface side of a pedestal metal. 8. The electrostatic chuck according to claim 7, wherein the ceramic cover and the base metal are joined by brazing.