JPH05206254A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To accurately process the entire surface of a wafer and to dissipating heat generated at the time of processing by forming the top surface of a platelike element made of a dielectric material in an attractive surface and forming a conductive adhesive layer disposed on the bottom surface of the element as an inner electrode. CONSTITUTION:An electrostatic chuck comprises a platelike element 1 made of a dielectric material, a metal base 3 and a conductive adhesive 2 interposed between the both. The adhesive layer 2 is a means for connecting the element 1 to the base 3 and simultaneously serves as an inner electrode. That is, when a voltage is applied between the layer 2 and a material H to be attracted through the base 3, the material H to be attracted can be fixed to the attractive surface 1a of the upper surface of the element 1 as a single pole type electrostatic chuck 7. In this case, since the layer 2 exists over the entire lower surface of the element 1, the material H to be attracted can be completely fixed even to the periphery of the surface 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck used for fixing, straightening and carrying a wafer such as silicon in a semiconductor processing apparatus.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing apparatus, an electrostatic chuck has been used for fixing, straightening and carrying a wafer such as silicon. Especially, an EB drawing device, a dry etching device, and a CV for processing a wafer in a vacuum processing chamber.
In D device and PVD device, fixed by vacuum chuck,
The use of an electrostatic chuck is effective because it is difficult to straighten and convey.

As shown in FIG. 4, the structure of this electrostatic chuck is such that an internal electrode 12 is embedded in a plate-like body 11 made of a dielectric material and is fixed to a base 13. Then, a voltage is applied between the internal electrode 12 and the object H to be adsorbed such as a silicon wafer by the power supply 15 to cause dielectric polarization in the plate-like body 11, and the electrostatic force of the dielectric polarization causes the object to be adsorbed on the adsorption surface 11a. The H is adsorbed and fixed. Although FIG. 4 shows a monopolar electrostatic chuck, there is also a bipolar electrostatic chuck in which a plurality of internal electrodes 12 are provided and a voltage is applied between the internal electrodes 12. ..

Although a resin has been used as a dielectric material for forming the plate-like body 11, it has recently been proposed to use ceramics having excellent heat resistance and corrosion resistance (Japanese Patent Laid-Open No. 62-264638). See the bulletin etc.). Also,
The present applicant has already proposed that, of these ceramics, particularly ferroelectric ceramics having a dielectric constant ε _r of 50 or more can be used to enhance the adsorption force (Japanese Patent Application No. 2-339325).
No.).

[0005]

However, the internal electrode 12 in such a conventional electrostatic chuck is embedded in the plate-shaped body 11 made of a dielectric material, and thus the plate-shaped body 1 is used.
Since it is smaller than the suction surface 11a of No. 1, there is a problem that an electrodeless portion is generated around the suction surface 11a.

Therefore, when an object to be adsorbed H such as a silicon wafer is fixed, there is no fixed adsorbing force in the peripheral portion, and for example, in an EB drawing apparatus that processes with an electron beam, the peripheral portion that cannot be adsorbed is exposed. In a dry etching device that becomes inaccurate or uses a magnetron for processing, an electrostatic chuck is used in order to release the heat generated during the processing, but since the wafer is not fixed and attracted at the electrodeless part, There is a problem that the contact area between the electrostatic chuck and the wafer is small and the heat does not escape sufficiently.

In the conventional electrostatic chuck, the plate-shaped body 1
Since the internal electrode 12 is embedded in the No. 1, there is also a problem that the manufacturing process is complicated.

[0008]

SUMMARY OF THE INVENTION Therefore, according to the present invention, the upper surface of a plate-shaped body made of a dielectric material is used as an adsorption surface, and the lower surface of the plate-shaped body is fixed to a base with a conductive adhesive layer interposed. In addition, an electrostatic chuck is provided with an energizing means so that the conductive adhesive layer serves as an internal electrode.

[0009]

According to the electrostatic chuck of the present invention, since the conductive adhesive layer interposed on the lower surface of the plate-shaped body can be used as the internal electrode, the internal electrode can be formed up to the same area as the attracting surface. it can. Therefore, since it becomes possible to adsorb and fix an object to be adsorbed such as a silicon wafer over almost the entire surface, the wafer can be processed with high accuracy over the entire surface, and the contact area between the wafer and the electrostatic chuck is small. Since it becomes wider, heat generated during processing can be sufficiently dissipated.

[0010]

EXAMPLES Examples of the present invention will be described below.

As shown in FIG. 1, the structure of the electrostatic chuck of the present invention comprises a plate-like body 1 made of a dielectric material, a base 3 made of metal such as aluminum, and a conductive adhesive layer interposed therebetween. It consists of 2. In this embodiment, the metal base 3 itself serves as a means for energizing the conductive adhesive layer 2, and a power source 5 is provided to apply a voltage between the base 3 and the object H to be adsorbed. The exposed surface of the base 3 other than the contact portion with the conductive adhesive layer 2 has an insulating layer 3a formed by alumite treatment or coating, and the exposed portion of the conductive adhesive layer 2 is covered with an insulating member 4. ing.

In this electrostatic chuck, the conductive adhesive layer 2 is a means for joining the plate-like body 1 and the base 3, and at the same time,
Acts as an internal electrode. That is, when a voltage is applied between the conductive adhesive layer 2 and the object H to be attracted through the base 3,
As a single-pole type electrostatic chuck, the attraction surface 1 on the upper surface of the plate-shaped body 1
The object H to be adsorbed can be fixed to a.

At this time, since the conductive adhesive layer 2 exists on the entire lower surface of the plate-shaped body 1, the attracting surface 1
The adsorbent H can be completely fixed even in the peripheral portion of a. Further, even when used in the glow discharge region, the exposed surfaces of the conductive adhesive layer 2 and the base 3 are covered with the insulating member 4 and the insulating layer 3a, so that there is no fear of discharging from this portion. Furthermore, in the electrostatic chuck of the present invention, since it is not necessary to embed the internal electrodes in the plate-shaped body 1, the manufacturing is extremely easy.

Next, another embodiment of the present invention will be described.

In the electrostatic chuck shown in FIG. 2, a plate-like body 1 made of a dielectric material is provided with a conductive adhesive layer 2 as in the embodiment shown in FIG.
It is fixed to the base 3 with the interposition of. And
The base 3 is made of an insulating material such as ceramics or a metal material having an insulating layer formed on the surface thereof, and the power supply metal fitting 6 is used as a means for energizing the conductive adhesive layer 2.
The structure is provided inside. Therefore, although not shown, if a voltage is applied between the power supply fitting 6 and the object to be attracted, the object to be attracted can be fixed to the attraction surface 1a.

In another embodiment, as shown in FIG. 3, as a means for energizing the conductive adhesive layer 2, a conductive adhesive 7 is filled in the through hole formed in the base 3 to form a lead wire. You can also connect. In addition, although not shown, a lead wire may be directly attached to the conductive adhesive layer 2 itself, or a conductive member may be attached by a mechanical means.

The material for forming the plate-like body 1 may be resin or the like, but it is desirable to use ceramics having excellent heat resistance and corrosion resistance. As ceramics, alumina (Al ₂ O ₃ ) and calcium titanate (C
aTiO ₃ ), barium titanate (BaTiO ₃ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ) and the like can be used as main components, but calcium titanate and barium titanate are mainly used. As an ingredient,
It is preferable to use a ferroelectric ceramic having a dielectric constant ε _r of 50 or more because the adsorption force can be increased. And
The plate-shaped body 1 can be easily manufactured by firing a molded body obtained by press-molding, tape-molding, or stacking thinly tape-molded ceramics.

The conductive adhesive layer 2 is made of a resin such as epoxy or silicone containing a conductive substance such as silver, nickel or carbon so as to have conductivity. Since the conductive adhesive layer 2 acts as an internal electrode, it is necessary to set the volume resistivity to 10 ⁻² Ω · cm or less. For that purpose, the content of the conductive substance is 2 to 5
It may be 0% by weight.

Further, among these conductive adhesives, particularly, silicone resin is used to contain silver to obtain a volume resistivity of 10
^{The one with -4} Ω · m was the best. Here, the silicone resin is a siloxane bond (Si-O-Si).
It is a semi-inorganic or semi-organic bond-containing silicon compound polymer having, and can be represented, for example, by the chemical formulas below.

[0020]

[Chemical 1]

[0021]

[Chemical 2]

Such a silicone resin is excellent in heat resistance and elasticity, and can absorb the difference in thermal expansion between the plate-shaped body 1 and the base 3 even at high temperatures. The thickness of the conductive adhesive layer 2 is 5 to 40 μm, preferably 10 to 15 μm.
It is good, and by setting it within this range, it is possible to increase the accuracy of attaching the plate-shaped body 1 to the base 3.

Further, as the base 3, a metal material such as aluminum or ceramics such as alumina is used as described above. In the case of the base 3 made of a metal material, the insulating layer 3a may be formed on the exposed surface by alumite treatment or coating.

Experimental Example Here, as an example of the present invention, an electrostatic chuck shown in FIG. 1 was prototyped. The plate-shaped body 1 was provided with an orientation flat, had a diameter of 4 inches, a thickness of 1 mm, and was formed of ceramics containing calcium titanate (CaTiO ₃ ) or barium titanate (BaTiO ₃ ) as a main component. This plate-like body 1 is fixed to a base 3 made of aluminum with a conductive adhesive layer 2 made of a silicone resin containing silver interposed therebetween, and power is supplied from the base 3. The exposed surface of the base 3 was anodized to form an insulating layer 3a, and the exposed portion of the conductive adhesive layer 2 was covered with an insulating member 4 made of an insulating silicone resin.

The electrostatic chuck of the present invention thus obtained has an adsorption property of 100 g / cm ² when 600 V is applied at a vacuum degree of 10 ^-2 Torr. further,
Since it is possible to interpose the internal electrodes on the entire surface of the adsorption surface 1a, a silicon wafer having an overall flatness of 20 μm can be formed into
By electrostatically fixing with V, the flatness could be 3 μm or more.

In the conventional electrostatic chuck, the attracting surface 1
Width of about 2 mm in the peripheral part of a (about 8% in area)
Since there is an electrodeless part in the silicon wafer, if the silicon wafer is in this range even if it is in this range even a little, the electrostatic chuck of the present invention is accurate over the entire surface of the silicon wafer. It was possible to perform various EB exposure and dry etching processes.

[0027]

As described above, according to the present invention, the upper surface of the plate-shaped body made of the dielectric material is used as the adsorption surface, and the lower surface of the plate-shaped body is fixed to the base with the conductive adhesive layer interposed. In addition, by configuring the electrostatic chuck by providing a current-carrying means so that the conductive adhesive layer serves as an internal electrode, the conductive adhesive layer can be interposed on the entire lower surface of the plate-like body, and the suction surface The electrodes can be formed over the entire surface of. Therefore, an object to be adsorbed such as a silicon wafer can be completely fixed and corrected up to the peripheral portion, and precise processing can be performed without lowering the yield when performing EB exposure, dry etching, or the like. In addition, the electrostatic chuck of the present invention does not need to embed electrodes and has a simple structure, so that it is possible to provide an electrostatic chuck having various characteristics such as easy manufacture.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an electrostatic chuck of the present invention.

FIG. 2 is a vertical sectional view showing another embodiment of the present invention.

FIG. 3 is a vertical sectional view showing another embodiment of the present invention.

FIG. 4 is a vertical sectional view showing a conventional electrostatic chuck.

[Explanation of symbols]

 1: Plate-like body 2: Conductive adhesive layer 3: Base 4: Insulating member 5: Power supply 6: Power feeding member

Claims (1)

[Claims] 1. A plate-shaped body made of a dielectric material, the upper surface of which is a suction surface, and the lower surface of which is fixed to a base with a conductive adhesive layer interposed therebetween.
An electrostatic chuck provided with an energizing means so that the conductive adhesive layer serves as an internal electrode.