JP2012138440A - Electrostatic chuck and method of manufacturing the same - Google Patents

Abstract

An electrostatic chuck that can be used in a specific environment and can be easily attached to and detached from a fixing base by improving an adsorption method.
An electrostatic chuck in which a suction electrode made of a conductive material is embedded in a plate-like insulating material, wherein the suction electrode is provided on the front side and the back side of the plate-like insulating material. Preferably, the adsorption electrode on the front side has a bipolar structure, and the adsorption electrode on the back side has a monopolar structure, more preferably, the static electrode With respect to the main surface direction of the back surface of the electric chuck, it is arranged in a range that occupies 5% or more and 40% or less of the total surface area of the back surface of the electrostatic chuck from the center of the back surface toward the outer periphery of the back surface.
[Selection] Figure 1

Description

The present invention relates to an electrostatic chuck used for, for example, a semiconductor manufacturing apparatus for electrostatically adsorbing an object to be adsorbed in a plate shape or other various shapes.

In a process for processing an insulating material such as a patterning mask or LED for a semiconductor manufacturing apparatus, as a means for fixing these insulating materials, for example, a gradient generated when a non-uniform electric field is formed on the adsorption surface ( There is an electrostatic chuck that uses a (Gradient) force.

As an example, the electrostatic chuck has a structure in which a base material portion, an electrode that generates an adsorption force thereon, and a dielectric layer that holds an adsorbate thereon are integrated. The electrostatic chuck main body is fixed to a base made of metal or the like by an appropriate method according to the use environment or purpose.

For example, Patent Document 1 discloses a technique in which a screw hole is formed in a base material portion of an electrostatic chuck and is fixed to a base with a bolt.

Patent Document 2 discloses that a substrate is placed in a substrate processing apparatus for processing a substrate, a base member, an electrostatic chuck for attracting a substrate provided thereon, the base member, and the electrostatic chuck. A method of reusing a substrate mounting member having an organic adhesive layer to be bonded, wherein the substrate mounting member is removed from the substrate processing apparatus when the substrate mounting member is replaced with a new substrate mounting member. Removing the adhesive layer, separating the base member and the electrostatic chuck, and reusing the base member and / or the electrostatic chuck; There is disclosed a technique for fixing an electrostatic chuck to a base with various adhesives.

Further, Patent Document 3 discloses an electrostatic chuck that includes a chuck electrode covered with an insulating layer therein and electrostatically attracts an object to be adsorbed to the surface by applying a voltage to the chuck electrode. The surface opposite to the surface to be electrostatically attracted is configured to be electrostatically attractable, and the electrostatic chuck that is detachable by electrostatic attraction and the electrostatic chuck are held on a holding base that holds the electrostatic chuck A technique of a thin plate holding device including a holding base is disclosed.

JP 2006-279057 A JP 2004-055815 A JP-A-9-162272

The technique of Patent Document 1 can firmly and reliably fix the electrostatic chuck, and can easily remove and replace the electrostatic chuck due to problems and maintenance. However, with this method, it is difficult to form a screw hole, particularly when the base portion of the electrostatic chuck is made of a quartz material. Therefore, for example, a structure such as cutting a screw groove by interposing a metal material in the screw hole is required, and the structure of the electrostatic chuck becomes complicated. In addition, there is a concern that the design range of the electrostatic chuck is limited or that the durability of the screw hole portion remains uneasy.

In the technique of Patent Document 2, an adhesive is used to fix the electrostatic chuck, so that the electrostatic chuck itself does not require complicated processing, and attachment and removal are relatively easy. However, this method requires a work for removing the residual adhesive, a work for applying a new adhesive, and the like for the peeling work when the electrostatic chuck is removed from the base member, and it still remains complicated. Further, depending on the use environment of the electrostatic chuck, the adhesive may not be applied.

The technique of Patent Document 3 is to fix the electrostatic chuck body itself to the holding table by using a gradient force or a Coulomb force generated by an electrode. For this reason, it can be said that it is suitable in that it can be used in a wide range of temperature environments, can be easily detached from the holding base, and can be adjusted in position.

However, in the technique described in Patent Document 3, the following points are concerned. That is, as shown in FIG. 3 of Patent Document 3, when the suction of the adsorbed material and the suction to the holding table are performed with the same electrode, the thickness of the dielectric layer formed on the suction surface of the adsorbed material is particularly 50 to 500 μm. In order to maintain the overall strength of the electrostatic chuck, it is necessary to increase the overall thickness of the electrostatic chuck. Since the attractive force is inversely proportional to the thickness of the dielectric layer, in this case, the attractive force on the holding table side where the dielectric layer thickness becomes very large is remarkably reduced, so that a sufficient attractive force cannot be obtained.

In order to avoid this problem, for example, as shown in FIG. 4 of Patent Document 3, a method in which the suction electrodes on the suction surface side and the holding table side are individually installed can be considered. However, simply placing the electrodes for adsorption on the front and back surfaces of the electrostatic chuck will not always meet the demands for realizing proper adsorption and facilitating the handling and design of the electrostatic chuck. It is hard to say that it can handle enough.

The present invention has been made in view of such problems, and relates to an electrostatic chuck that fixes the electrostatic chuck body itself to a holding table by using a gradient force generated by an electrode or a Coulomb force. The present invention provides an electrostatic chuck capable of facilitating the handling and design of the electrostatic chuck and capable of realizing appropriate suction, and a method for manufacturing the electrostatic chuck.

An electrostatic chuck according to the present invention is an electrostatic chuck in which a suction electrode made of a conductive material is embedded in a plate-like insulating material, and the suction electrode is made of the plate-like insulating material. It is characterized by being formed independently on both the front side and the back side. By adopting such a configuration, it is possible to provide an electrostatic chuck that can be easily handled and designed.

In the electrostatic chuck according to the present invention, it is preferable that the suction electrode on the front side is a bipolar type, and the suction electrode on the back side is a monopolar type.

In the electrostatic chuck according to the present invention, the plate-like insulating material is preferably silica glass.

Furthermore, in the electrostatic chuck according to the present invention, the attracting electrode on the back surface side is arranged on the back surface of the electrostatic chuck from the center of the back surface toward the outer periphery of the back surface with respect to the main surface direction of the back surface of the electrostatic chuck. It is preferable to be disposed within a range that occupies 5% or more and 40% or less of the total area of the main surface.

An electrostatic chuck manufacturing method according to an aspect of the present invention includes a step of forming a plate material for a surface-side dielectric layer by forming an electrode pattern of a conductive material on one main surface of a plate-like silica glass, and the like. Forming a plate material for the back side dielectric layer by forming an electrode pattern made of a conductive material on one main surface of the plate-like silica glass, and forming each plate-like silica glass for the substrate on each main surface And a step of bonding the plate material for the front surface side dielectric layer and the plate material for the back surface side dielectric layer, and a step of fusing by heating and pressurizing under reduced pressure.

According to the present invention, it is possible to provide an electrostatic chuck capable of facilitating handling and design, and capable of realizing appropriate suction, and a manufacturing method thereof.

The detailed contents of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual view of the shape of the periphery of an electrostatic chuck as viewed from a cross-sectional direction according to an embodiment of the present invention.

The conceptual diagram which looked at the shape of the electrostatic chuck and fixing base based on one Embodiment of this invention from the cross-sectional direction. The schematic diagram which looked at the electrode pattern of the electrode for surface side adsorption | suction or the electrode for back surface side adsorption | suction based on one Embodiment of this invention from the one main surface direction. The conceptual diagram which looked at arrangement | positioning of the electrode for back surface side adsorption | suction based on one Embodiment of this invention from the cross-sectional direction. The conceptual diagram which looked at arrangement | positioning of the electrode for back surface side adsorption | suction based on other embodiment of this invention from the cross-sectional direction. The conceptual diagram which looked at the shape of the back side based on other embodiment of this invention from the cross-sectional direction.

An electrostatic chuck according to the present invention is an electrostatic chuck in which a suction electrode made of a conductive material is embedded in a plate-like insulating material, and the suction electrode is made of the plate-like insulating material. They are formed independently on both the front side and the back side.

In FIG. 1, there is a plate-like insulating material in which a front-side dielectric layer 11, a back-side dielectric layer 12, and a base material layer 13 positioned between these dielectric layers are integrated. In this plate-like insulating material, an adsorption electrode made of a conductive material, in which the front-side adsorption electrode 31 and the back-side adsorption electrode 32 are independently arranged, is embedded. And the electrostatic chuck 1 is comprised by these. The electrostatic chuck 1 is placed and fixed on a fixing base 4.

As the plate-like insulating material, various known materials that can be used for electrostatic chucks can be applied. Examples thereof include aluminum nitride, alumina, silicon nitride, and boron nitride, and silica glass is preferably used. Usually, the same material is applied to the front-side dielectric layer 11 and the back-side dielectric layer 12, but different materials may be used. In particular, when silica glass is applied, an appropriate amount of various additives may be added to change the physical properties so as to correspond to the physical properties required for the front and back surfaces.

The front-side attracting electrode 31 and the back-side attracting electrode 32 are formed to generate a Coulomb force, a Johnson-Rahbek force, or a gradient force as an attracting force with respect to the electrostatic chuck. These are made of a strip-like or foil-like conductive material having a predetermined width with respect to the main surface direction of the front surface side adsorption surface 21 or the back surface side adsorption surface 22 and a predetermined thickness with respect to the depth direction. . And these electrodes are various pattern shapes arrange | positioned by the fixed space | interval with respect to the plane direction, and an adsorbate can be strongly adsorbed and hold | maintained in a wide area.

About the front surface side adsorption electrode 31 and the back surface side adsorption electrode 32, the width | variety, thickness, and space | interval of the electrode can be designed timely according to the specification of the required electrostatic chuck. Moreover, although an example of an electrode pattern shape is shown in FIG. 2, this can also be designed arbitrarily. Furthermore, the front-side adsorption electrode 31 and the back-side adsorption electrode 32 do not have to have the same specifications, and can be arbitrarily designed.

A known conductive material applicable to an electrostatic chuck is used as the material of the front side adsorption electrode 31 or the back side adsorption electrode 32. As an example, it is a single material made of any one of Ni, Mo, W, Pt and Ti, or a single material made of an alloy of two or more of these. Furthermore, the composite structure which consists of these 2 or more types of metals may be sufficient. The shape of the electrode may also be a shape other than a strip shape or a foil shape, for example, a thread shape or a net shape.

The thicknesses of the front-side dielectric layer 11 and the back-side dielectric layer 12 are also set appropriately according to the specifications required for the electrostatic chuck to be designed. The thicknesses of the front-side dielectric layer 11 and the back-side dielectric layer 12 are assumed to be a plane including the entire pattern of the front-side adsorption electrode 31 or the back-side adsorption electrode 32, and the surface on the adsorption surface side of this plane. The average distance from the surface to the adsorption surface is shown. Although an average space | interval is not specifically limited, As an example, it can show by the average value of 5 points in a plane which consists of a center part and 4 points inside 10 mm of outer periphery.

In the electrostatic chuck according to the present invention, the attracting electrodes are independently formed on both the front side and the back side of the plate-like insulating material. That is, a dielectric layer is formed on the surface side adsorption electrode 31 or the back side adsorption electrode 32 in the vicinity of the surface to be adsorbed.

Usually, the electrostatic chuck 1 is fixed on the fixing base 4 at a predetermined location in the apparatus by means such as a bolt or an adhesive. In the present invention, the electrostatic chuck 1 and the fixing base 4 are electrostatically attracted by a Coulomb force, a Johnson-Rahbek force, or a gradient force as an attracting force. Thereby, the electrostatic chuck 1 has the characteristics that it can be arbitrarily fixed and removed, and it is not necessary to add special processing and auxiliary members to the main body of the electrostatic chuck 1.

Further, in the electrostatic chuck according to the present invention, it is preferable that the front surface side adsorption electrode 31 is a bipolar type and the back side adsorption electrode 32 is a monopolar type. In the present invention, the electrode can be designed arbitrarily. However, if the back surface side adsorption electrode 32 is a monopolar type, it is structurally easy to arrange the ground with respect to the fixing base 4, and the static The degree of freedom in designing the entire periphery including the electric chuck 1 and the fixing base 4 can be increased. Further, when the rear surface side adsorption electrode 32 is a monopolar type and the front side adsorption electrode 31 is a bipolar type combination, the number of power supply devices for applying a voltage to the electrodes can be reduced, thereby saving energy and saving space. From the viewpoint of the above, it can be said that it is more preferable.

In the electrostatic chuck according to the present invention, the front-side dielectric layer 11, the back-side dielectric layer 12, and the base material layer 13 are all preferably made of silica glass. Silica glass is highly pure and excellent in workability, so that it can be suitably used particularly by a semiconductor manufacturing apparatus. Depending on the purpose of use, various metal elements may be added to silica glass at appropriate times.

Further, the back surface side adsorption electrode 32 of the electrostatic chuck according to the present invention has a main surface on the back surface of the electrostatic chuck from the center of the back surface toward the outer periphery of the back surface with respect to the main surface direction of the back surface of the electrostatic chuck. It is preferable to arrange within a range that occupies 5% or more and 40% or less of the total area.

In a state where the attracting force is applied to the entire back side, for example, when the electrostatic chuck 1 is heated and used, the entire electrostatic chuck 1 is warped. Therefore, the stress inside the electrostatic chuck 1 increases, and the load on the electrostatic chuck 1 increases. This state is not always preferable depending on the environment used. Therefore, in this case, the stress inside the electrostatic chuck 1 can be reduced by arranging the electrodes so that the adsorption force is generated only in the vicinity of the center of the back surface instead of using the entire back surface side as the adsorption surface.

Even if the front-side dielectric layer 11 and the back-side dielectric layer 12 expand and contract at the same rate, the back-side dielectric layer 12 side is in contact with the fixing base 4 and the weight of the electrostatic chuck 1 is applied. Therefore, the stress from the fixing base 4 is affected. Further, the warpage of the entire electrostatic chuck 1 tends to increase due to the difference in the heat dissipation rate.

Here, the stress in the vicinity of the back surface side dielectric layer 12 is not fixed by adopting a structure in which an attracting force is not generated in the vicinity of the outer periphery of the back surface side attracting surface 22 instead of the entire back surface side attracting surface 22. Dispersed in the direction of the contact surface with the base 4. When this contact surface is fixed by an attracting force, there is no escape field of stress, and it remains inside the electrostatic chuck 1, resulting in an increase in warpage.

FIG. 3 is a conceptual view of the arrangement of the back side adsorption electrode according to the embodiment of the present invention, as viewed from the cross-sectional direction. The entire electrostatic chuck back surface range 51 corresponds to the area of the entire back surface of the electrostatic chuck 1, and the back surface side suction electrode forming range 52 includes the back surface side suction electrode 32 and generates an attracting force. The range is shown.

Usually, unless there is a particular reason, if the shape of the main surface of the electrostatic chuck 1 is circular, the back surface side adsorption electrode formation range 52 is also designed to be the same type of circle. However, it is not always necessary to make the shapes completely the same, and modifications such as an elliptical shape and a substantially polygonal shape are possible.

And with respect to the main surface direction of the electrostatic chuck back surface, it is arranged in a range that occupies 5% or more and 40% or less of the total surface area of the back surface of the electrostatic chuck from the center of the back surface toward the outer periphery of the back surface. The back side adsorption electrode 32 is formed in a range of 5% or more and 40% or less in terms of the area of the main surface of the back surface of the electrostatic chuck with the center line 53 in the cross section of the electrostatic chuck as the center. It has been shown.

As an example, when the electrostatic chuck 1 is configured with a perfect circle, the back side attracting electrode 32 has an electrode pattern formed within a true circle having a center at the center line 53 in the cross section of the electrostatic chuck. Yes. Note that the electrode patterns of the front surface side adsorption electrode 31 and the back surface side adsorption electrode 32 may not be the same shape.

Here, the back surface side attracting electrode 32 is formed in the vicinity of the center line 53 in the cross section of the electrostatic chuck. In other words, it can be said that the vicinity of the outer periphery of the back surface of the electrostatic chuck 1 is not attracted. Therefore, the form in which the outer peripheral part is adsorbed and the vicinity of the center is not adsorbed does not fall into a preferable form of the present invention.

It is not preferable that the back surface side attracting electrode 32 of the electrostatic chuck is less than 5% of the main surface area of the back surface of the electrostatic chuck because the attracting force necessary for fixing the electrostatic chuck 1 is insufficient. On the other hand, if it exceeds 40%, as described above, the stress escape field on the contact surface decreases, and the stress remaining in the electrostatic chuck 1 increases, which is also not preferable.

FIG. 4 is a conceptual diagram of the arrangement of the back surface side adsorption electrode 32 according to another embodiment of the present invention as seen from the cross-sectional direction. As described above, it is not essential that the range in which the back side suction electrode 32 is formed includes the center line 53 in the cross section of the electrostatic chuck, and suction force is generated in the outer peripheral portion of the back side suction surface 22. Otherwise, such a variation is possible.

In addition, the cross-sectional shape of the front surface and the back surface of the electrostatic chuck 1 according to the present invention is not limited to that shown in FIG. 1, and may be, for example, a shape as shown in FIG. In particular, when viewed as a whole of the electrostatic chuck 1, the warpage can be mitigated more effectively by combining the effect of reducing the warpage due to the cross-sectional shape with the effect of optimizing the arrangement of the back side suction electrode according to the present invention.

One embodiment of the method for producing an electrostatic chuck according to the present invention includes a step of forming a plate material for a surface-side dielectric layer by forming an electrode pattern made of a conductive material on one main surface of a plate-like silica glass, and the like. Forming a plate material for the back side dielectric layer by forming an electrode pattern made of a conductive material on one main surface of the plate-like silica glass, and forming each plate-like silica glass for the substrate on each main surface And a step of bonding the plate material for the front surface side dielectric layer and the plate material for the back surface side dielectric layer, and a step of fusing by subsequently heating and pressurizing under reduced pressure.

Each process itself does not require any special method, and widely known methods can be applied depending on the material to be used and the purpose of use. Although not shown, the method of attaching the power supply terminal for supplying current to the front surface side attracting electrode 31 and the back surface side attracting electrode 32 is an appropriate method according to the design specifications of the entire electrostatic chuck 1. Made. For example, the power supply terminals of the surface-side adsorption electrode 31 and the surface-side adsorption electrode 32 may be arranged with appropriate holes formed on the main surface side of the fixing base 4, or from the side surface side of the electrostatic chuck 1. May be handled.

Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG. 1, but the present invention is not limited to this example.

(Experiment 1)
As the dielectric layer 11 and the dielectric layer 12, a silica glass plate having a diameter of 150 mm and an average thickness of 5 mm is prepared, and a Mo metal film is used for the range of a diameter of 148 mm on the upper surface, and a bipolar comb pattern with a circular comb pattern is used. The electrode 3 was formed by vacuum deposition. A view of the pattern of the electrode 3 as seen from above is shown in FIG. The film thickness of the electrode 3 is 0.3 μm on average, the width of the electrode 3 is 2 mm on average, and the distance between the electrodes is 0.5 mm on average. Next, a silica glass plate having a diameter of 150 mm and an average thickness of 5 mm was prepared as the base material layer 13. Then, on the base material layer 13 and the dielectric layer 12, perfect terminal holes with a diameter of 5.1 mm were formed at two locations corresponding to the outermost electrode portions of the electrode pattern.

Next, the dielectric layer 11 and the dielectric layer 12 on which the electrode pattern was formed were superposed on the base material layer 13, respectively. In this state, pressure fusion was performed under reduced pressure of 10 Pa at 1300 ° C. for 60 minutes under a pressure of 20 MPa, and integrated to obtain an electrostatic chuck base with electrodes embedded therein. Then, the surface layer was ground and polished so that the average thickness of the base dielectric layer 11 was 150 μm and the average thickness of the dielectric layer 12 was 150 μm. Then, a power feeding terminal made of Mo having a diameter of 5 mm and a length of 5 mm processed according to the shape of the terminal hole is prepared, and Dortite D-753 ( After applying the conductive paste (Fujikura Kasei), the feeding terminal was inserted and fixed. Thus, the electrostatic chuck of Example 1 was obtained.

As Comparative Example 1, a silica glass plate corresponding to the dielectric layer 12 of Example 1 was prepared, and an electrode was not formed here. The other configuration conformed to that of Example 1.

Prepared a fixing base made of aluminum in which a hollow having a diameter of 20 mm and a depth of 1 mm is formed, which is 1 mm larger than the diameter of the electrostatic chuck 150 mm, and the electrostatic chucks of Example 1 and Comparative Example 1 were inserted respectively. did. And in Example 1, the wiring which applies an electric current to the electric power feeding terminal was given using the predetermined jig.

The electrostatic chuck of Example 1 was fixed to the fixing base 4 by applying 2000V. The electrostatic chuck of Comparative Example 1 was fixed by applying a resin adhesive to the entire back surface 22 corresponding to the dielectric layer 12.

A fixed base made of aluminum is fixed so that it does not float even when a lifting load is applied in the vertical direction, and a metal handle is attached to the surface of each electrostatic chuck with an adhesive. The vertical adhesive force was evaluated by applying a load little by little in the range and applying a pulling load to the electrostatic chuck.

As a result, in both the electrostatic chucks of Example 1 and Comparative Example 1, the fixing base did not come off. From this, it was confirmed that the electrostatic chuck of Example 1 has a practically sufficient adhesive force as in the case of fixing the electrostatic chuck with an adhesive. Of course, the electrostatic chuck of Example 1 is superior to the electrostatic chuck of Comparative Example 1 in that it can be arbitrarily removed from the fixing base if the supply of current is stopped.

(Experiment 2)
The shape of the electrode pattern of the back surface side electrode 32 is not changed, and the electrode pattern outermost radius is changed in the ratio of Table 1 with respect to the diameter of 150 mm. did. With respect to these electrostatic chucks, with the silica glass disk having a thickness of 1 mm and a diameter of 150 mm adsorbed as an adsorbate, the entire electrostatic chuck was heated to 120 ° C. with a heater from the outside. Warpage was evaluated. The evaluation method of warpage is to measure the warpage of the silica glass disk with respect to the adsorbate from above the adsorbate using a laser displacement meter, and calculate the difference from the warp of the silica glass disk before adsorption, A comparison method was adopted.

From the results of Table 1, it can be said that the electrostatic chuck in a more preferable implementation range of the present invention is more excellent in that the warpage of the electrostatic chuck is reduced when it is used by heating.

As described above, the electrostatic chuck according to the present invention can be easily handled and designed, and can realize proper adsorption.

The electrostatic chuck according to the present invention is suitably used for, for example, a semiconductor manufacturing apparatus for electrostatic adsorption of various electrically insulating substrates.

DESCRIPTION OF SYMBOLS 1 ... Electrostatic chuck, 11 ... Surface side dielectric layer, 12 ... Back surface side dielectric layer, 13 ... Base material layer, 21 ... Surface side adsorption surface, 22 ... Back surface side adsorption surface, 31 ... Surface side adsorption electrode, 32 ... Electrode for back side adsorption, 4 ... Fixing base, 51 ... Full range of back side of electrostatic chuck, 52 ... Range of electrode formation for back side suction, 53 ... Center line in cross section of electrostatic chuck.

Claims (5)

An electrostatic chuck in which a suction electrode made of a conductive material is embedded in a plate-like insulating material, wherein the suction electrode is on both the front side and the back side of the plate-like insulating material, An electrostatic chuck characterized by being formed independently. 2. The electrostatic chuck according to claim 1, wherein the front-side attracting electrode is bipolar, and the back-side attracting electrode is monopolar. 3. The electrostatic chuck according to claim 1, wherein the plate-like insulating material is silica glass. The suction electrode on the back surface side is 5% or more and 40% or less of the main surface area of the back surface of the electrostatic chuck from the center of the back surface toward the outer periphery of the back surface with respect to the main surface direction of the back surface of the electrostatic chuck. The electrostatic chuck according to claim 3, wherein the electrostatic chuck is disposed within a range that occupies the area. Forming an electrode pattern with a conductive material on one main surface of a plate-like silica glass to produce a plate material for a surface-side dielectric layer; and a conductive material on one main surface of another plate-like silica glass Forming a plate material for the back-side dielectric layer by forming an electrode pattern according to the above, and a plate material for the front-side dielectric layer and the back-side dielectric layer on each main surface of the plate-like silica glass for the substrate 5. The production of an electrostatic chuck according to claim 3, comprising: a step of bonding a plate material for use, and a step of fusing by subsequently heating and pressurizing under reduced pressure. Method.