JP2008244190A - Electrostatic chuck device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck device having an excellent desorption property with respect to an object to be chucked after the application of a voltage is stopped. <P>SOLUTION: In the electrostatic chuck device 10 in which an uppermost layer 33 has an insulating property and the uppermost layer 33 has a chucking face coming into contact with the object to be chucked, a coefficient of dynamic friction between the uppermost layer 33 and the object to be chucked is ≤1.0. It is preferable that the electrostatic chuck device 10 contain a fluoroplastic in the uppermost layer 33 coming into contact with the object. According to the electrostatic chuck device 10, the excellent desorption property can be exhibited with respect to the object after the application of a voltage is stopped. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrostatic chuck apparatus that holds, for example, a semiconductor wafer or a glass substrate by suction.

In semiconductor manufacturing, it is necessary to fix a semiconductor wafer at a predetermined position of a processing apparatus such as a plasma etching apparatus. In particular, in the production of an integrated circuit in which a fine pattern is drawn on a semiconductor wafer to form a large number of semiconductor elements, it is indispensable to securely fix the semiconductor wafer to a flat surface.
Mechanical, vacuum, and electrical chuck devices are used as means for fixing the semiconductor wafer. Among these, the electric chuck device, that is, the electrostatic chuck device has an advantage that even a non-flat semiconductor wafer can be fixed with good adhesion, is easy to handle, and can be used even in a vacuum.
The electrostatic chuck device applies a voltage to internal electrodes sandwiched between insulators, and adsorbs an object to be attracted using static electricity generated by the voltage.

2. Description of the Related Art Conventionally, for example, an electrostatic chuck device (Patent Document 1) or the like is known in which a dielectric breakdown voltage is improved and a stable adsorption force is obtained by using a polyimide film as an outermost layer in contact with an object to be adsorbed.
An object to be attracted such as a semiconductor wafer is fixed to a predetermined position of a processing apparatus by an electrostatic chuck and needs to be quickly detached from the electrostatic chuck after a predetermined processing step. If the object to be adsorbed does not detach immediately after the voltage application to the electrostatic chuck is stopped, the tact time is increased and the productivity is lowered. Therefore, it is desired that the electrostatic chuck device used for these applications has a quick detachability with respect to the object to be adsorbed as well as a stable adsorbing force with respect to the object to be adsorbed.
JP 2004-235563 A

However, it has been difficult for the conventional electrostatic chuck device to obtain quick detachability of the object to be adsorbed after the voltage application is stopped.
The present invention has been made in view of the above situation, and an object thereof is an electrostatic chuck device that is excellent in the ability to detach an object to be attracted when voltage application is stopped.

(1) In an electrostatic chuck apparatus in which the outermost layer has an insulating property and the outermost layer has an attracting surface in contact with the object to be adsorbed, the dynamic friction coefficient between the outermost layer and the object to be adsorbed is 1.0. An electrostatic chuck device comprising:
(2) The electrostatic chuck device according to (1), wherein the outermost layer in contact with the object to be adsorbed contains a fluororesin.

  ADVANTAGE OF THE INVENTION According to this invention, the electrostatic chuck apparatus excellent in the removal property of the to-be-adsorbed object in the case of a voltage application stop can be provided.

  An embodiment of an electrostatic chuck device according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the electrostatic chuck device of the present embodiment when cut in a direction perpendicular to the extending direction of the internal electrodes. For convenience of explanation, the side that adsorbs the object to be adsorbed is defined as the upper side, and the opposite side is defined as the lower side. For convenience of explanation, each layer is illustrated with a certain interval. In an actual electrostatic chuck, the layers are in close contact.

As shown in FIG. 1, in the electrostatic chuck device 10 of the present embodiment, an insulating layer 31 and an outermost layer 33 are bonded via insulating adhesive layers 22 and 23, and the insulating adhesive layer 22 and The electrode sheet (electrostatic chuck device electrode sheet) 30 in which the band-like internal electrodes 41 and 42 are formed between the electrode sheets 30 and the electrode sheet 30 is attached to the substrate 20 via the adhesive layer 21. This is an electrostatic chuck device. In the present embodiment, the upper surface of the outermost layer 33 is an adsorption surface that adsorbs an object to be adsorbed.
Further, in the electrostatic chuck device 10 of the present invention, the outermost layer 33 has an insulating property, and the upper surface of the outermost layer 33 is an attracting surface in contact with an object to be attracted.

As a result of diligent research, the present inventors have found that when the dynamic friction coefficient between the outermost layer of the electrostatic chuck device and the object to be adsorbed is 1.0 or less, the detachability of the object to be adsorbed is good when the voltage application is stopped. I found out that Based on this result, the electrostatic chuck device 10 of the present invention is characterized in that the dynamic friction coefficient between the outermost layer 33 and the object to be attracted is 1.0 or less.
The coefficient of friction is a coefficient indicating the magnitude of the frictional force applied when sliding an object. The value of the horizontal force required to slide is divided by the magnitude of the force applied vertically. It is. The coefficient of friction is determined by the material of the contact surfaces of the two substances that are in contact with each other and the state of the contact surfaces.
The friction coefficient includes a dynamic friction coefficient and a static friction coefficient. The dynamic friction coefficient is a value obtained by dividing the magnitude of the friction force acting in the opposite direction of the moving direction of the object by the magnitude of the force applied perpendicularly to the object when the object is moving. When trying to move a stationary object, it is a value obtained by dividing the magnitude of the frictional force acting in the opposite direction of the moving direction of the object by the magnitude of the force applied vertically.

  The electrostatic chuck device 10 of the present invention is preferably used as an electrostatic chuck device for silicon wafers, glass, metal, and resin films. If these adsorbents are used, the coefficient of dynamic friction with the outermost layer 33 tends to be 1.0 or less.

  The material included in the outermost layer 33 is not particularly limited as long as the material can have a coefficient of dynamic friction with the object to be adsorbed of 1.0 or less, and examples thereof include fluororesin and polyimide. Among these, a fluororesin is preferable. If it is the outermost layer 33 containing a fluororesin, the coefficient of dynamic friction with the object to be adsorbed can be kept low by taking advantage of the property of the low frictional force of the fluororesin. Thereby, the electrostatic chuck apparatus excellent in the detachability of the to-be-adsorbed object after the voltage application is stopped can be obtained. Note that the fluororesin has a stable adsorption force equivalent to that of the polyimide resin with respect to the adsorption force when a voltage is applied. Here, the fluororesin refers to a resin containing a fluorine element.

  The content of the fluororesin contained in the outermost layer 33 is preferably 0.025 to 100% by mass. If it is less than 0.025% by mass, the properties of the fluororesin are hardly exhibited, and it is difficult to obtain good detachability of the adsorbed material.

  Examples of the fluororesin contained in the outermost layer 33 include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene- Ethylene Copolymer, Polyvinyl Fluoride, Vinylidene Fluoride Rubber, Tetrafluoroethylene-Propylene Fluoro Rubber, Tetrafluoroethylene-Propylene Rubber, Fluorine-containing Silicon Rubber, Fluorophosphazene Fluoro Rubber, Fluorine-containing Thermoplastic Based fluororubbers.

Examples of the form of the outermost layer 33 containing a fluororesin include a fluororesin film molded into a film shape.
Fluororesin films are commercially available. For example, polytetrafluoroethylene film (trade name: NITOFLON, manufactured by Nitto Denko Corporation), tetrafluoroethylene-hexafluoropropylene copolymer film (trade names: NEOFRON film, Daikin Industries, Ltd.) And tetrafluoroethylene-ethylene copolymer film (trade name: Fluon-ETFE, manufactured by Asahi Glass Co., Ltd.).

  As the form of the fluororesin in the outermost layer 33, the fluororesin may be dispersed in the outermost layer 33 as a filler. The particle diameter of this filler is preferably 0.01 to 10 μm. If the particle diameter of the filler is less than 0.01 μm, the once dispersed filler is liable to cause secondary aggregation, and therefore, the adsorbing surface is uneven, and the adhesion to the object to be adsorbed is lowered. Even when the particle diameter of the filler exceeds 10 μm, the particle diameter is large, so that unevenness tends to occur on the adsorption surface, which is not preferable.

The thickness of the outermost layer 33 is preferably 5 to 150 μm. More preferably, it is 10-50 micrometers. If the thickness is less than 5 μm, the strength of the outermost layer 33 is insufficient. On the other hand, if the thickness exceeds 150 μm, the distance from the internal electrode to the object to be adsorbed becomes long, and it is difficult to obtain a good adsorption force.
The outermost layer 33 preferably has a pencil hardness of 2H or more on the adsorption surface. If the pencil hardness is less than 2H, scratches are likely to occur due to contact with the object to be adsorbed.
The unevenness difference of the surface of the outermost layer 33, that is, the adsorption surface for adsorbing the adsorbed material is preferably 20 μm or less. When the uneven | corrugated difference of the adsorption | suction surface 33 exceeds 20 micrometers, adhesiveness with to-be-adsorbed object will fall, and adsorption | suction power will become inadequate.
Further, the adsorption surface of the outermost layer 33 may be subjected to sandblasting for the purpose of reducing the dynamic friction coefficient.

  Furthermore, the outermost layer 33 has an ultraviolet absorber, a near infrared absorber, a light stabilizer, a light scattering agent for the purpose of improving hardness, adhesion, durability, weather resistance, light resistance, water resistance, corrosion resistance, and the like. Various additives such as an antioxidant, an antifoaming agent, a leveling agent, a thixotropy imparting agent, a mold release agent, an ion scavenger, a lubricant, and a coupling agent can be added.

The material of the insulating layer 31 is not particularly limited as long as it has insulating properties, but a resin film having insulating properties is preferably used. Examples of the main component of the insulating resin film include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene, polyimide, polyamide, polyamideimide, polyethersulfone, polyphenylene sulfide, polyetherketone, and polyetherimide. , Triacetyl cellulose, silicon rubber and the like. Of these, polyesters, polyolefins, polyimide, silicone rubber, polyetherimide, polyethersulfone, and the like are preferable because of excellent insulation. Particularly preferred is polyimide. If it is a polyimide, it can show the outstanding dielectric breakdown tolerance also in the high voltage application. The polyimide film is commercially available. For example, trade name Kapton manufactured by Toray DuPont, trade name Upilex manufactured by Ube Industries, and trade name Apical manufactured by Kaneka Chemical Co., Ltd. are preferably used.
Although the thickness of the insulating layer 31 is not specifically limited, 20-150 micrometers is preferable and 25-75 micrometers is more preferable.

The insulating adhesive layers 22 and 23 are not particularly limited as long as the insulating adhesive layers 22 and 23 have insulating properties that do not cause a short circuit between the internal electrodes. However, the insulating adhesive layers 22 and 23 are preferably composed of an adhesive mainly composed of a resin material. As the main component of the resin material, for example, from epoxy resin, phenol resin, polyamide resin, acrylonitrile-butadiene copolymer, polyester resin, polyimide resin, silicon resin, styrene block copolymer, amine compound, bismaleimide compound, etc. From the adhesive which has 1 type or 2 types or more of resin selected as a main component, what satisfy | fills conditions can be selected and used.
Epoxy resins include bisphenol, phenol novolac, cresol novolac, glycidyl ether, glycidyl ester, glycidylamine, trihydroxyphenylmethane, tetraglycidylphenolalkane, naphthalene, diglycidyldiphenylmethane, and diglycidyl. Specific examples include bifunctional or polyfunctional epoxy resins such as biphenyl type. Among these, bisphenol type epoxy resins are preferable, and bisphenol A type epoxy resins are particularly preferable. When epoxy resin is the main component, curing agents for epoxy resins such as imidazoles, tertiary amines, phenols, dicyandiamides, aromatic diamines, organic peroxides, and curing accelerators are used as necessary. An agent may be blended.
Specific examples of the phenol resin include novolak phenol resins such as alkylphenol resins, p-phenylphenol resins, and bisphenol A type phenol resins, resole phenol resins, polyphenylparaphenol resins, and the like.
Examples of the styrene block copolymer include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), Specific examples include styrene-ethylene-propylene-styrene copolymer (SEPS).

  As the adhesive constituting the adhesive layer 21, the same adhesive as the insulating adhesive layers 22 and 23 can be used. However, since the adhesive layer 21 is not in direct contact with the internal electrode, high insulation resistance as required for the insulating adhesive layers 22 and 23 is not necessary.

  The internal electrodes 41 and 42 are not particularly limited as long as they are conductive substances that can exhibit electrostatic attraction when a voltage is applied, but copper, aluminum, gold, silver, platinum, chromium, nickel, tungsten, etc. What patterned the thin film which consists of 1 type, or 2 or more types of metals selected from these alloys is used preferably. Examples of the method for forming a metal thin film include a method of forming a film by vapor deposition, plating, sputtering, etc., a method of forming a film by applying and drying a conductive paste, and a method of attaching a metal foil such as a copper foil. Can be mentioned.

  Although it does not specifically limit as the board | substrate 20 which adheres the electrode sheet 30, For example, an aluminum substrate, a stainless steel substrate, a ceramic substrate etc. are mentioned.

  The electrostatic chuck device 10 of the present invention is not necessarily limited to the layer structure of FIG. 1 because the dynamic friction coefficient of the outermost layer 33 and the object to be adsorbed should be 1.0 or less. Insulating layers and adhesive layers can be added or omitted. The electrostatic chuck device 10 of the present invention may be the electrode sheet 30 itself without the adhesive layer 21 and the substrate 20.

  If the electrostatic chuck device 10 of the present embodiment is used, the dynamic friction coefficient between the outermost layer 33 and the object to be adsorbed is 1.0 or less, so that the object to be adsorbed after the voltage application is stopped is excellent. Since the detachability is excellent, the tact time in the production of semiconductor wafers can be reduced, and the productivity can be improved.

EXAMPLES Next, although this invention is demonstrated in more detail using an Example, this invention is not limited to these Examples.
<Production of electrostatic chuck device>
Example 1
A method for producing the electrostatic chuck device 10 of Example 1 will be described with reference to FIG.
First, a polyimide film having a thickness of 50 μm corresponding to the insulating layer 31 (trade name: Kapton 200H, manufactured by Toray DuPont Co., Ltd.) is disposed on an adhesive film having a thickness of 20 μm corresponding to the insulating adhesive layer 22. Then, a 12 μm-thick copper foil (trade name: TQ-VLP, manufactured by Mitsui Kinzoku Mining Co., Ltd.) for forming the internal electrodes 41 and 42 was laminated.
Next, the copper foil surface was etched to form internal electrodes 41 and 42 having the shape of comb electrodes. The comb-shaped electrode was a comb-shaped internal electrode in which conductive portions having a width of 5 mm and insulating portions having a width of 5 mm were alternately arranged in an area of 90 × 90 mm.
Next, a polytetrafluoroethylene film having a thickness of 50 μm corresponding to the outermost layer 33 is placed on the internal electrodes 41 and 42 via an adhesive film having a thickness of 20 μm corresponding to the insulating adhesive layer 23 (trade name). : Nitoflon, manufactured by Nitto Denko Corporation) was laminated to obtain an electrode sheet 30.
After cutting the obtained electrode sheet 30 into a predetermined dimension, a 5 × 100 × 100 mm aluminum substrate corresponding to the substrate 20 is laminated through an adhesive film having a thickness of 20 μm corresponding to the adhesive layer 21, The electrostatic chuck apparatus 10 of Example 1 was produced.

The adhesive film was obtained by the following materials and processes. First, a resol phenol resin (trade name: Shonor CKM-908A, manufactured by Showa Polymer Co., Ltd.) and NBR (trade name: Nipol 1001, manufactured by Nippon Zeon Co., Ltd.) are mixed at a mass ratio of 1: 1, and an adhesive composition is prepared. It was a thing. This adhesive composition was dissolved in methyl ethyl ketone to prepare an adhesive solution having a solid content of 30% by mass. Next, this adhesive solution was applied to one side of a releasable polyethylene terephthalate film (thickness 38 μm) and then dried by heating at 150 ° C. for 3 minutes to obtain an adhesive film having a thickness of 20 μm.
For adhesion of the laminates via the adhesive film, high temperature continuous lamination at 150 ° C. was used, and the laminates were stuck together by heat melting of the adhesive film. Moreover, in the adhesion of the electrode sheet 30 and the aluminum substrate 20 through the adhesive sheet corresponding to the adhesive layer 21, first, vacuum pressing is performed at 150 ° C./30 minutes, and then, 150 ° C. in a ventilation oven. A heat treatment of / 12 hours was performed to accelerate the thermosetting of the adhesive, and the laminates were stuck together.

(Example 2)
An electrostatic chuck apparatus 10 was produced in the same manner as in Example 1 except that a polyimide film (Kapton 200H, manufactured by Toray DuPont) having a thickness of 50 μm was used instead of the polytetrafluoroethylene film of the outermost layer 33. .
(Example 3)
An electrostatic chuck apparatus similar to Example 1 except that a 50 μm thick polyimide film (Kapton 200H, manufactured by Toray DuPont) was used instead of the polytetrafluoroethylene film of the outermost layer 33. 10 was produced. In the sand blasting treatment, silica sand having a particle diameter of 0.1 mm was used as an abrasive, and the blasting amount for the polyimide film was 0.5 kg / min.

(Comparative Example 1)
An electrostatic chuck device was produced in the same manner as in Example 1 except that silicon rubber (trade name: DY32-1000U, thickness: 500 μm, manufactured by Toray Dow Corning Co., Ltd.) was used as the outermost layer 33.

(Comparative Example 2)
As the outermost layer 33, the surface of the polyimide film of Example 2 (trade name: Kapton 200H, thickness 50 μm, manufactured by Toray DuPont Co., Ltd.) is thickened with a silicone resin (KR-112, solid content 30%, manufactured by Shin-Etsu Chemical Co., Ltd.). An electrostatic chuck device was produced in the same manner as in Example 1 except that the outermost layer was formed of silicon resin by coating at 10 μm and drying at 120 ° C. for 30 minutes.

<Evaluation>
Using the electrostatic chuck devices obtained in Examples 1 to 3 and Comparative Examples 1 and 2, the adsorption force, the detachability, and the dynamic friction coefficient were tested by the following methods. The results are shown in Table 1.
(Adsorption power)
A voltage with a potential difference of 5 kV was applied to the internal electrode of the electrostatic chuck device to adsorb the object to be adsorbed, and fixed and held for 1 minute, and then the voltage application was stopped. The peel strength of the object to be adsorbed was measured once during the fixed holding, 0 times after stopping the voltage application, and 30 times after stopping the applied voltage for a total of 3 times, and the adsorptive power was evaluated.
Note that non-alkali glass having a size of 0.3 × 80 × 80 mm was used as the object to be adsorbed. For measuring the peel strength, Tensilon (model number: RTC-1150A, manufactured by Orientec Co., Ltd.) was used, and the peel strength when the glass was peeled in the vertical direction at a speed of 50 mm / min was measured. The measurement environment was 25 ° C. and relative humidity 55%.
(Withdrawal)
Based on the measurement of the adsorptive power, the detachability was evaluated according to the following criteria.
○ = less than 1 gf / cm ² immediately after application stop Δ = less than 1 gf / cm ² after 30 seconds of application stop × = more than 1 gf / cm ² after 30 seconds of application stop (dynamic friction coefficient)
The dynamic friction coefficient was measured by the following method based on JISK7125.
First, the electrostatic chuck device was fixed to a table. Next, an alkali glass having a size of 0.7 × 80 × 50 mm was prepared as an object to be adsorbed, and a reinforcing plate was adhered to the alkali glass, which was then placed on the electrostatic chuck. Furthermore, a weight (diameter 2.54 cm) having a weight of 200 g was arranged at the center on the object to be adsorbed.
A tensile tester equipped with a jig that can be pulled at an angle of 90 degrees is fixed to the reinforcing plate portion of the object to be adsorbed arranged in this way, and pulled at a speed of 100 mm / min for 1 minute to move a distance of 100 mm. Thus, the frictional force generated between the alkali glass and the suction surface of the electrostatic chuck device at that time was measured.
The value of the horizontal part after the maximum value of the measured friction force was averaged, and this was defined as the dynamic friction force. Then, the dynamic friction coefficient was determined by dividing this dynamic friction force by the weight of the weight of 200 g.

As shown in Table 1, Examples 1 to 3 not only have good adsorption power when applying voltage to an object to be adsorbed, but also have excellent detachability when voltage application is stopped. Was confirmed. On the other hand, it was confirmed that Comparative Examples 1 and 2 were inferior in releasability because they had an adsorptive power even after 30 seconds had elapsed after the voltage application was stopped.
In Examples 1 and 3, the dynamic friction coefficient was a particularly low value of 0.4. As a reason for this, in Example 1, it was speculated that the use of a polytetrafluoroethylene film mainly composed of a fluororesin for the outermost layer 33 contributed to the reduction of the dynamic friction coefficient. Moreover, in Example 3, it was speculated that the polyimide film used for the outermost layer 33 was subjected to the sand blast treatment for reducing the frictional force, which contributed to the reduction of the dynamic friction coefficient.

  As described above in detail, according to the present invention, it is possible to provide an electrostatic chuck device that is excellent in the ability to detach an object to be attracted when voltage application is stopped.

Sectional drawing which shows the embodiment of the electrostatic chuck apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electrostatic chuck apparatus 20 Board | substrate 21 Adhesive layer 22, 23 Insulating adhesive layer 30 Electrode sheet 31 Insulating layer 33 Outermost layer 41, 42 Internal electrode

Claims (2)

  In the electrostatic chuck device in which the outermost layer has an insulating property and the outermost layer has an attracting surface in contact with the object to be adsorbed, the dynamic friction coefficient between the outermost layer and the object to be adsorbed is 1.0 or less. An electrostatic chuck device characterized by that. The electrostatic chuck apparatus according to claim 1, wherein the outermost layer in contact with the object to be adsorbed contains a fluororesin.

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