Electricity: electrical systems and devices – Electric charge generating or conducting means – Use of forces of electric charge or field
Reexamination Certificate
1999-07-29
2001-07-03
Fleming, Fritz (Department: 2836)
Electricity: electrical systems and devices
Electric charge generating or conducting means
Use of forces of electric charge or field
C279S128000, C429S208000
Reexamination Certificate
active
06256187
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrostatic chuck device for using electrostatic energy to fix semiconductors or conductors like wafers in place by adsorption.
2. Description of the Related Art
Chuck devices are used for fixing a semiconductor wafer in place at a specific site in the processing equipment during the step in which the semiconductor wafer is worked. Devices employing mechanical, vacuum and electrostatic means are available as chuck devices. Of these, an electrostatic chuck device offers the advantages of enabling adsorption even when the wafer is not flat, easy handling, and applicability in a vacuum.
One example of a conventional electrostatic chuck device is disclosed in Japanese Patent Application, Second Publication No. Hei 5-87177. As shown in
FIG. 4
, in this device, an adhesive layer
2
a
, insulating film layer
4
, adhesive layer
2
b
, electrode
3
b
consisting of a thin metallic plate, adhesive layer
2
c
, and insulating film layer
7
are sequentially laminated onto a metal substrate
1
. Wafer
5
is adsorbed to wafer adsorbing surface, which is the upper surface of insulating film layer
7
. A temperature adjusting means
6
is formed inside metal substrate
1
for adjusting the temperature by passing through constant temperature water or the like.
FIG. 5
shows the electrostatic chuck device disclosed in Japanese Patent Application, First Publication No. Hei 8-148549. This device is designed so that a relatively thick insulating adhesive layer
2
is formed onto metal substrate
1
. An electrode
3
a
formed of a vapor deposited or plated metal coating is adhered to the bottom surface of an insulating film layer
7
, which is adhered on to insulating adhesive layer
2
. Semiconductor wafer
5
is then adsorbed to this insulating film layer
7
.
It is, by the way, desirable that such devices as these have a high coefficient of thermal conductivity while at the same time maintaining electricity insulating properties. When coefficient of thermal conductivity is low, the efficacy of the temperature adjusting means is insufficient, causing the wafer to experience an abnormal increase in temperature during processing.
In recent years, it has been proposed to improve the ability to transfer heat from the wafer to the metal substrate while at the same time maintaining high electricity insulating properties, by disposing a ceramic plate that has excellent electricity insulating properties and thermal conductivity which is superior to that of resins.
Typically, thermosetting adhesives such as epoxy-type adhesives are used as the adhesive for adhering the ceramic plate. However, epoxy-type adhesives have especially high Young's modulus after hardening and experience volume changes to some extent during hardening.
For this reason, the adhesive is not able to absorb stress which is generated due to different coefficients of thermal expansion between the metal substrate and the ceramic plate, and the adhesive separates from the ceramic plate, particularly at the outer periphery thereof, causing a deterioration in thermal conductivity at these areas of separation. As a result, cooling of the outer periphery of the wafer becomes difficult. In addition, because the ceramic plate employed is typically very thin, when stress is applied on the ceramic plate due to volume changes in the adhesive layers, a variety of problems occur as bowing of the ceramic plate so that there is a deterioration in the flatness of the wafer adsorbing surface, a decrease in the wafer adsorbing force, and significant leaking of the helium gas used for cooling which is supplied in small amounts between the wafer adsorbing surface and the wafer.
As in the conventional examples described above, when made of a resin material, wafer adsorbing surface is gradually worn due to repeated contact with the wafer. In addition, damage or deformation may occur in the wafer adsorbing surface due to foreign objects. Accordingly, the durability of such resin wafer adsorbing surface has not been sufficient.
In addition, there are other problems encountered such as gradual exhaustion and deterioration due to subjection to various reactions and dry etching with plasma during wafer processing, a deterioration in the electricity insulating properties of the electrostatic chuck device over a relatively short period of time due to damage imparted during handling or the like, poor durability, and short life.
Moreover, another problem which occurs is that insulation breaks down when microscopic damage occurs to the adsorbing surface.
SUMMARY OF THE INVENTION
The present invention was conceived in consideration of the above described circumstances, and has as its objective the provision of a highly durable electrostatic chuck device which can prevent a deterioration in the degree of flatness of the wafer adsorbing surface, bowing of the ceramic plate and peeling of the adhesive layer from the ceramic plate over a long period of time.
In order to achieve the above-stated objective, the electrostatic chuck device according to the present invention is characterized in that a ceramic layer, forming the adhering surface, is provided on top of a metal substrate via an electricity insulating elastic layer, and an electrode is formed in between the electricity insulating elastic layer and the ceramic layer, the electricity insulating elastic layer consisting of an adhesive that contains a rubber component and a phenol-type antioxidant.
In addition, an insulating film layer can be formed in between the electricity insulating elastic layer and the electrode.
The present invention's electrostatic chuck device is designed so that an insulating adhesive layer is formed to at least one surface of the electricity insulating elastic layer.
Because the adsorbing surface is formed of a ceramic layer in the present invention's electrostatic chuck device, wear and deformation do not readily occur. As a result, durability is extremely high.
Moreover, even if there is stress caused by the different coefficients of thermal expansion during heat treatment, or slight volume changes in the resin material, the electricity insulating elastic layer relieves that stress, and reduces the stress on the ceramic layer. Thus, a reduction in the degree of flatness can be avoided.
By including a phenol-type antioxidant having superior thermal resistance in the electricity insulating elastic layer, radicals generated by the rubber component are efficiently absorbed even at high temperatures, making it possible to prevent oxidative deterioration of the rubber component over a long period of time. As a result, such problems can be prevented over a long period of time as the occurrence of deformations in the ceramic layer, a decline in the ability to cool the adsorbed object due to partial peeling of the joining boundary between the ceramic layer and the adhesive layer, a reduction in the adsorbing force due to a deterioration in the degree of flatness of the adsorbing surface, and the like.
In addition, by providing an insulating adhesive layer in contact with at least the surface of the electricity insulating elastic layer that is on the metal substrate side, and preferably in contact with both surfaces of the electricity insulating elastic layer, it is possible to prevent the occurrence of tacking on the surface, improve operability during manufacture of the electrostatic chuck, and increase productivity.
The first embodiment of the present invention's method for manufacturing an electrostatic chuck device is characterized in the provision of 1) a step for forming an electrode layer on one surface of the insulating film; 2) a step for laminating a ceramic layer on to the electrode layer via an adhesive; 3) a step for laminating an electricity insulating elastic layer containing a rubber component and phenol-type antioxidant to the non-electrode layer surface of the insulating film; and 4) a step for bonding the laminate obtained in 3) to the metal substrate.
A second emb
Kobayashi Masaharu
Matsunaga Tadao
Fleming Fritz
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tomoegawa Paper Co. Ltd.
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