JPH08279550A - Electrostatic chuck - Google Patents

Abstract

PURPOSE: To make the surface of a dielectric ceramic board superior in cooling characteristics and at the same time, to prevent the plasma discharge from expanding to the periphery of the surface of a plasma discharge electrode. CONSTITUTION: An electrostatic chuck is a structure, wherein a dielectric ceramic board 1 and an electrically insulative base 2 are bonded together and are integrally constituted holding an electrode metal layer between the board 1 and the base 2 and the electrode metal layer consists of a brazing metal layer 3 arranged into an electrode form and is fused between the board 1 and the base 2 to constitute the electrostatic chuck.

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 which is excellent in cooling characteristics of a dielectric ceramic surface and can prevent plasma discharge from wrapping around the electrode surface. is there.

[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 adhered on a pedestal that is structurally excellent in heat conduction, and the back surface of the pedestal is usually cooled or heated to a constant temperature, except in special cases. The pedestal is made of a material with excellent heat conduction such as aluminum or aluminum nitride, and the pedestal and the ceramic are usually bonded together with an organic adhesive. It is difficult to keep the treated substrate adsorbed on the body ceramic surface at a uniform temperature. In addition, there is a problem that the joint part peels off during use. Further, there is a problem that the adhesive type cannot be used for a substrate whose plasma CVD process or the like has a considerably high temperature. On the other hand, during operation, there is also a problem that plasma discharge wraps around the exposed portion of the brazing material in the brazing part.

[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, it is another object of the present invention to provide a new structure of an electrostatic chuck that can solve the problem of plasma discharge wraparound.

[0004]

The above problems can be solved by the following means. That is, 1. An electrode metal layer is sandwiched and integrated between a dielectric ceramic plate and an electrically insulating pedestal, and the electrode metal layer is made of a brazing material arranged in an electrode shape. An electrostatic chuck characterized by being fused to a body ceramic plate and an electrically insulating pedestal. 2. 2. The electrostatic chuck according to claim 1, wherein an exposed portion of a side surface of the electrode metal layer sandwiched between the dielectric ceramic plate and an electrically insulating pedestal is covered with an insulating material. 3. An electrode metal layer is sandwiched between a dielectric ceramic plate and an insulating ceramic plate to be joined and integrated, and
The insulating ceramic plate is joined to a base metal, the electrode metal layer is made of a brazing material arranged in an electrode shape, and is fused to the dielectric ceramic plate and the insulating ceramic plate. An electrostatic chuck characterized by: 4. The electrostatic chuck according to claim 3, wherein an exposed portion of a side surface of the electrode metal layer sandwiched between the dielectric ceramic plate and the insulating ceramic plate is covered with an insulating material.

[0005]

In the electrostatic chuck, the electrode metal layer is always formed on the back surface of the dielectric ceramic regardless of whether it is a monopolar type or a bipolar type. In the bipolar system, the two electrodes are separated by a few millimeters and isolated from each other. When the pedestal material is an insulating material, even if the bipolar electrode is directly bonded to the pedestal, the insulation between the electrodes is not destroyed. However, when the pedestal is made of a metal material, it cannot be directly joined to the pedestal. It is once joined to the insulating ceramic and then joined to the pedestal metal through this insulating ceramic.

The bipolar electrode is formed by processing a foil of a metal brazing material fused to any one of a dielectric ceramic, a pedestal ceramic or an insulating ceramic sandwiched between the electrodes into a shape of an electrode, and then forming the dielectric ceramic or the pedestal ceramic. It can be formed by heating and fusing by sandwiching between them or between a dielectric ceramic and an insulating ceramic. Alternatively, it can be formed by printing or applying the powder of the above metal brazing material on one or both of the joint surfaces, superposing them, heating and melting and fusing. Raw material components are Ag, Cu, Ni, Co, Si, Al, S
Metals and alloys mainly composed of elements such as n and In are added to Ti and Z.
An alloy to which an active metal such as r, Nb, Ta, V, Y, Ca, Mg, Mn or Cr is added is preferable. The amount of active metal is preferably in the range of 0.3 to 15%. If it is less than the lower limit, strong fusion bonding is not sufficient. If it exceeds the upper limit, it becomes brittle, which is not preferable.

When the pedestal is made of metal, the dielectric ceramic is once joined to the insulator ceramic and then joined to the pedestal. The joining of the insulator ceramic and the pedestal metal is similar to the case of the dielectric ceramic. On the pedestal metal,
A brazing material to be fused to both of the insulating ceramics may be sandwiched between the two to heat and fuse them, or the bonding surface of the insulating ceramics may be metallized and the metallized surface and the pedestal may be brazed. For example, when the pedestal metal is a material such as Mo, W, or Cr, the pedestal and the insulating ceramic are A as described above.
Metals and alloys containing g, Cu, Ni, Co, Si, Al, Sn and In as main components, Ti, Zr, Nb and T
A foil, a powder of an alloy to which an active metal such as a, V, Y, Ca, Mg, Mn, or Cr is added is sandwiched in between to heat, melt, and join. On the other hand, when the pedestal metal is a metal such as AL, Ni, Co, Fe, etc., especially a metal having a low melting point such as AL,
It is better to metalize the joint surface of the insulator ceramic and braze it to the pedestal. To braze the pedestal, it is naturally necessary to select a brazing material having a melting point lower than the melting point of the pedestal. Therefore, for the AL pedestal, Zn, Cd, Sn, In, Pb, etc. are the basic components. It is necessary to join with brazing material. In addition to the above-mentioned Zn, Cd, Sn, In, Pb, etc., Ag, Cu,
A brazing material containing a metal component such as Ni, Co, or Al as a main component can be appropriately used. When the pedestal is made of ceramic, the brazing filler metal used can of course be selected from a high melting point to a low melting point regardless of the melting point.

The atmosphere for heating and melting the alloy containing the active metal is preferably a vacuum, non-oxidizing or inert atmosphere, and particularly preferably a high vacuum of 10 ⁻⁴ Torr or more.

It is necessary that the distance between the electrodes is 3 to 4 mm, and the pattern of the electrodes is divided into two parts by dividing the disk into two parts, and it is 3 to the left and right.
The pattern illustrated in FIG. 1 has more uniform adsorptivity than the shape having a distance of 4 mm.

There is at least a gap corresponding to the thickness of the brazing material in the brazed portion sandwiched between the dielectric ceramic and the pedestal, or between the dielectric ceramic and the insulating ceramic plate, and between the insulating ceramic plate and the pedestal. Is exposed to the outside, where plasma discharges may wrap around.
To prevent the wraparound, it is effective to fill the exposed portion of the brazing material with an inorganic adhesive, or a silicone resin, a fluorine resin, or a polyimide resin. The inorganic adhesive is preferably a mixture of a ceramic aggregate that is electrically insulating and harmless to a semiconductor, and an inorganic binder. High-purity silica as aggregate,
High-purity alumina, aluminum nitride, etc. can be used as the binder, and alumina sol, silica sol, alkoxides that generate alumina, silica, silicon nitride, aluminum nitride, etc. by heating, inorganic polymers, etc. can be used.

There are no special restrictions on the material of the dielectric ceramics, which are commonly used alumina, silicon carbide,
Alternatively, sapphire, aluminum nitride, or any other ceramic material can be used.

As the material of the insulating ceramic, any ceramic can be used as long as it has high thermal conductivity, electrical insulation, and is harmless to the semiconductor. Ceramics such as alumina, silicon carbide, and aluminum nitride.

The material of the ceramic pedestal is basically the same as the material of the insulating ceramic, and any ceramic can be used as long as it has high thermal conductivity, electrical insulation, and is harmless to the semiconductor. Ceramics such as alumina, silicon carbide, and aluminum nitride.

The insulation resistance between the electrodes is 3 to 4 between the electrodes.
In mm, it is usually necessary to have 13 MΩ or more. In the present invention, the electrode layer (the brazing material layer) is separated by 3 to 4 mm, and in most cases, 15
A resistance of MΩ or more can be obtained, but 2-3 out of 100 cases, 1
It may be less than 3 MΩ. In such a case, the electric resistance is restored by heating to 300 ° C. or higher, most preferably 400 ° C. or higher in an oxidizing atmosphere after joining. This phenomenon is 13 MΩ
All of the above have a recovery phenomenon as a whole, 5-10M
Ω Resistance increases. There is almost no recovery below 300 ° C. Since the recovery effect does not change even if it exceeds 600 ° C,
It is economical below 600 ° C.

【Example】

Example 1 Dielectric ceramic: SiC-based dielectric ceramic (φ150 × 2t) having the shape shown in FIG. 2 was used. Sn-1% Ti cut out on the back surface of the dielectric ceramic in the electrode shape of FIG.
A 100 micron foil of alloy was applied. Pedestal: Aluminum nitride ceramic with the shape shown in Fig. 2 is used. In a vacuum (2 × 10 ⁻⁵ To) by stacking with a dielectric ceramic to which a foil of Sn-1% Ti alloy is attached.
rr), heated at 800 ° C. for 10 minutes and brazed. After the bonding, the electrical resistance between the electrodes was measured, and this was heat-treated at 400 ° C. for 1 hour in the atmosphere. After heating, silicone resin was filled in the gaps in the brazing portion, and the side surfaces were also covered. In FIG. 2, 1
Is a dielectric ceramic, 2 is a pedestal ceramic, 3 is a brazing layer, and 4 is a filling and coating layer of silicon resin. <Results> As a result of non-destructive inspection with ultrasonic waves, cracks were found in the joints,
No defective welding was observed, and 100% was bonded to the pattern shape of the electrode. The resistance between the electrodes was 15 MΩ immediately after joining, but increased to 18 MΩ after heating to 400 ° C. Usage status A DC voltage was applied between the electrodes to electrostatically adsorb the silicon wafer. The bottom surface of the pedestal was brought into contact with a water cooling plate to cool it with water. The plasma CVD process was used for a total of 1000 hours. During the treatment, the surface temperature of the dielectric ceramic reached 400 ° C., but no peeling or cracking of the joint was observed. The temperature of the brazed part was 90 to 95 ° C. By the way, the conventional organic adhesive type cannot be used in the plasma CVD process and naturally peels off at the joint. The direct brazing improved heat transfer and made the surface temperature uniform, resulting in uniform plasma treatment. Improved quality and yield of processed substrates. In addition, plasma did not wrap around during this treatment.

[0012]

As described above in detail, the present invention has the characteristic that the surface of the electrostatic chuck can be uniformly and strongly cooled, and at the same time, it can completely prevent the plasma from wrapping around.
It can greatly contribute to the improvement of the quality and yield of the semiconductor plasma processed substrate.

[Brief description of drawings]

FIG. 1 is a diagram showing a shape of an electrode.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dielectric ceramic 2 ... Pedestal 3 ... Brazing material layer 4 ... Silicon resin filling layer

Claims (4)

[Claims] 1. A structure in which an electrode metal layer is sandwiched and integrated between a dielectric ceramic plate and an electrically insulating pedestal, and the electrode metal layer is an electrode-shaped brazing material. An electrostatic chuck comprising the dielectric ceramic plate and an electrically insulating pedestal fused together. 2. The electrostatic chuck according to claim 1, wherein an exposed portion of a side surface of the electrode metal layer sandwiched between the dielectric ceramic plate and an electrically insulating pedestal is covered with an insulating material. . 3. A structure in which an electrode metal layer is sandwiched and integrated between a dielectric ceramic plate and an insulating ceramic plate, and the insulating ceramic plate is bonded to a base metal. The electrostatic chuck is characterized in that the electrode metal layer is made of a brazing material arranged in the shape of an electrode, and is fused to the dielectric ceramic plate and the insulating ceramic plate. 4. The electrostatic capacitor according to claim 3, wherein the exposed portion of the side surface of the entire electrode layer sandwiched between the dielectric ceramic plate and the insulating ceramic plate is covered with an insulating material. Chuck.