Electrostatic chuck and manufacturing method thereof

Abstract

To provide an electrostatic chuck capable of usually obtaining an equivalent suction force when sucking a substrate Sw by expressing the suction force by Johnson-Rahbeck force and a gradient force.SOLUTION: An electrostatic chuck EC for sucking a substrate Sw so as to be provided to a front surface of a base Bp, comprises: a dielectric layer 1 of which a volume resistance ratio is 1012 Ωcm or more; and an electrode layer 2 combined into the dielectric layer. An electrode layer includes: flat-plate first electrode parts 21a and 21b; and a pair of positive and negative second electrode parts 22a and 22b which is arranged close to each other while having a line width narrower than that of each first electrode part. A part of the dielectric layer positioned above each first electrode part is constructed by a low volume resistance ratio layer 1c obtained by locally deteriorating the volume resistance ratio.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrostatic chuck that is provided on a surface of a base and attracts and holds an object to be attracted, and a method for manufacturing the same. [Background technology]

[0002] For example, in the manufacturing process of flat panel displays, various vacuum processes, such as film formation processes using a plasma atmosphere, ion implantation processes, and etching processes, are performed on relatively large substrates made of glass, quartz, or resin. Vacuum processing equipment for performing such vacuum processes generally includes a stage equipped with an electrostatic chuck that positions and holds the substrate within a vacuum chamber in a vacuum atmosphere. During vacuum processing, the substrate, which serves as an object to be attracted to the electrostatic chuck, may be cooled to a predetermined temperature or lower by heat exchange with the stage. To achieve this, it is necessary to attract and hold the substrate in close contact with the electrostatic chuck over its entire surface until the vacuum processing is completed.

[0003] This type of electrostatic chuck is known, for example, from Patent Document 1. This chuck is made of alumina (Al2O3) as its main component and has a volume resistivity of 10 8 Ωcm~10 14 It has a dielectric layer (holding base) made of a ceramic material with a resistance in the Ωcm range, and a pair of positive and negative electrode layers built into it. The dielectric layer is oriented with the substrate adsorption side facing up, and the portion of the dielectric layer above the electrode layer is made thinner, allowing the substrate to be adsorbed by an adsorption force dominated by the Johnsen-Rahbek force. In this case, the electrode layer can be configured so that each electrode exerts a gradient force in addition to the Johnsen-Rahbek force.

[0004] With the above configuration, for example, when a conductive film is formed on the surface of an insulating substrate by a film formation process, the substrate before the start of vacuum processing, which is less prone to polarization, can be attracted by an attraction force dominated by gradient force, and once the conductive film is formed on the substrate surface, the substrate can be maintained in a held state by an attraction force dominated by Johnsen-Rahbek force. However, when attraction forces due to both Johnsen-Rahbek force and gradient force can be generated, if the portion of the dielectric layer located above the electrode layer is made of the same ceramic material, there is a problem in that when an attraction force dominated by either the Johnsen-Rahbek force or the gradient force is generated, the attraction force cannot be effectively strengthened. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4976911 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above points, and an object of the present invention is to provide an electrostatic chuck and a manufacturing method thereof that are capable of always obtaining a uniform attracting force when an attracting force dominated by the Johnsen-Rahbek force or the gradient force is exerted to attract an object to be attracted. [Means for solving the problem]

[0007] In order to solve the above problems, the electrostatic chuck of the present invention is provided on the surface of a base and attracts an object to be attracted. 12The device is characterized in that it comprises a dielectric layer of Ωcm or more and an electrode layer incorporated within the dielectric layer, the electrode layer having a flat first electrode portion and a pair of positive and negative second electrode portions that have a line width narrower than that of the first electrode portion and are arranged close to each other, and the portion of the dielectric layer located above the first electrode portion, with the attracting surface side of the dielectric layer facing up, is composed of a low volume resistivity layer in which the volume resistivity is locally reduced.

[0008] According to the above, for example, when a conductive film is formed on an insulating substrate such as glass as an object to be attracted, after placing the substrate on the electrostatic chuck, applying a DC voltage (e.g., 1 kV to 5 kV) between the positive and negative electrodes of the second electrode unit generates an attracting force dominated by gradient force, and the substrate is attracted to the upper surface of the dielectric layer. Then, once a conductive film is formed on the surface of the substrate, applying a DC voltage (e.g., 10 V to 10,000 V) to the first electrode unit generates an attracting force dominated by Johnsen-Rahbek force, and the substrate is maintained in an attracted state to the upper surface of the dielectric layer. Thus, in the present invention, by adopting a configuration in which the portions of the dielectric layer located above the first and second electrode units have different volume resistivities, a constant attracting force can be obtained even when an attracting force dominated by Johnsen-Rahbek force or gradient force is exerted to attract an object to be attracted. Therefore, the substrate Sw can be attracted and held with a substantially constant attracting force while a conductive film is being formed on the substrate. In this case, when the volume resistivity of the dielectric layer located above the second electrode unit is 10 12 If the resistivity is less than Ωcm, a strong attracting force dominated by gradient force will not be achieved even if the DC voltage applied between the positive and negative electrodes is increased. 6 Ωcm~10 12 Outside the Ωcm range, the strong adsorption force dominated by the Johnsen-Rahbek force does not manifest. The first electrode is usually composed of a pair of electrodes with equal surface area (bipolar type), but a monopolar type may also be used when performing film formation processing using a plasma atmosphere.

[0009] In the present invention, Low volume resistivity layeris formed by doping the dielectric layer with a dopant, and in this case, it is preferable that the dielectric layer and the low volume resistivity layer are formed by thermal spray coating. Here, for example, when forming the dielectric layer from a material mainly composed of Al2O3, it is considered to use a sintering method for its manufacture. However, with such a sintering method, it is difficult to form layers with different volume resistivities with uniform interfaces due to thermal expansion and thermal contraction during sintering, which can lead to problems such as dielectric breakdown. In contrast, if the dielectric layer and the low volume resistivity layer are formed by thermal spray coating, it is advantageous because it is easy to form layers with different volume resistivities with uniform interfaces. Note that when the dielectric layer is mainly composed of Al2O3, if the dopant is at least one selected from TiO2, Cr, Ca, Mg, SiO2, and C, the volume resistivity can be increased to 10 6 Ωcm~10 12 Dielectric layers in the Ωcm range can be easily achieved.

[0010] In order to solve the above problems, the present invention provides a method for manufacturing an electrostatic chuck that is provided on a base surface and attracts and holds an object to be attracted, the method comprising the steps of: forming a base surface having a volume resistivity of 10 12 The method comprises the steps of: a first step of forming a first dielectric layer having a resistivity of Ωcm or more by thermal spraying; a second step of forming a flat first electrode portion and a pair of positive and negative second electrode portions having a line width narrower than that of the first electrode portion and arranged close to each other on the surface of the first dielectric layer portion; and a third step of forming a second dielectric layer portion having a volume resistivity equivalent to that of the first dielectric layer portion so as to cover the second electrode portion, and a third dielectric layer portion having a volume resistivity lower than that of the first dielectric layer portion so as to cover the first electrode portion, on the surface of the first dielectric layer portion by thermal spraying.

[0011] In the present invention, it is preferable to use the same dielectric material as the spray material for the first dielectric layer portion and the second dielectric layer portion, and to use the same dielectric material doped with a dopant at a predetermined weight ratio as the spray material for the third dielectric layer portion. When the dielectric layer is mainly composed of Al2O3, the dopant can be at least one selected from TiO2, Cr, Ca, Mg, SiO2, and C. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic cross-sectional view showing the electrostatic chuck of the present embodiment in a state where a substrate is attracted to the electrostatic chuck; [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 2A to 2D are diagrams showing the manufacturing procedure of the electrostatic chuck shown in FIG. 1. [Figure 4] 10 is a graph showing experimental results illustrating the effects of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, with reference to the drawings, an embodiment of an electrostatic chuck and a manufacturing method thereof according to the present invention will be described, in which an object to be attracted is a glass substrate (hereinafter referred to as "substrate Sw"), and the substrate Sw is attracted to the electrostatic chuck in a vacuum chamber (not shown). In the following, terms indicating directions such as up, down, left, and right are based on FIG.

[0014] 1 and 2, the electrostatic chuck EC of this embodiment includes a dielectric layer 1 provided on the upper surface of a base Bp made of a metal such as titanium or aluminum, which has a rectangular outline corresponding to the substrate Sw and a flat upper surface, and an electrode layer 2 incorporated in the dielectric layer 1. The dielectric layer 1 is 10 12 The thermal spray coating is made of a dielectric material such as Al2O3 (alumina), AlN (aluminum nitride), or SiC (silicon carbide) that has a volume resistivity of Ωcm or more, and is formed by spraying this thermal spray material to a thickness of 50 μm or more. Note that any known thermal spraying device can be used to form the thermal spray coating, so a detailed description will be omitted here.

[0015] The electrode layer 2 has a pair of positive and negative first electrode portions 21a, 21b provided on both sides of the dielectric layer 1 in the longitudinal direction (left-right direction in FIG. 1), and a pair of positive and negative second electrode portions 22a, 22b provided in a central region between the first electrode portions 21a, 21b. The first electrode portions 21a, 21b, each having the same area, are each made of a metal film having a thickness of 1 μm or more, which is formed into a flat plate shape by vacuum deposition or sputtering using a high-melting-point material with relatively high electrical conductivity, such as tungsten or molybdenum. The area of ​​the first electrode portions 21a, 21b (line width: width in the left-right direction in FIG. 1) is set appropriately taking into consideration the area of ​​the substrate Sw, the chucking force required to chucking the substrate Sw, the thickness and volume resistivity of the low-volume resistivity layer described below, and the like. The second electrode portions 22a and 22b are also made of a metal film having a thickness of 1 μm or more, which is formed in a predetermined pattern by vacuum deposition, sputtering, or CVD using a high-melting-point material with relatively high electrical conductivity, such as tungsten or molybdenum. In this embodiment, the positive second electrode portion 22a and the negative second electrode portion 22b are formed in a pattern in which they are alternately arranged at a narrow interval so as to extend linearly and face each other with a line width narrower (thinner) than the first electrode portions 21a and 21b, so that an electric field is efficiently generated when a voltage is applied. In this case, the line length is preferably 5 cm / cm. 2 The pattern of the positive second electrode portion 22a and the negative second electrode portion 22a is not limited to this, and may be curved, comb-like, or circumferential, as long as it can increase the length of the opposing surfaces.

[0016] The thickness of the dielectric layer 1 located above the first electrode portions 21a, 21b and the second electrode portions 22a, 22b is set to 50 μm or more, taking into consideration that the attraction force dominated by the Johnsen-Rahbek force varies with the square of the distance between the substrate Sw and the first electrode portions 21a, 21b. In addition, the portion of the dielectric layer 1 located above the first electrode portions 21a, 21b is made up of a low volume resistivity layer (third dielectric layer portion 1c described below) with locally reduced volume resistivity. The volume resistivity of the low volume resistivity layer 1c is set to 10 μm or more in order to effectively strengthen the attraction force when the attraction force dominated by the Johnsen-Rahbek force is exerted. 6 Ωcm~10 12The resistance is set to the range of Ωcm. When a predetermined voltage (e.g., 10 V to 10,000 V) is applied between the pair of positive and negative first electrodes 21a and 21b by the DC power supply E1, an attractive force dominated by the Johnsen-Rahbek force is generated. On the other hand, when a predetermined voltage (e.g., 1 kV to 5 kV) is applied between the pair of positive and negative second electrodes 22a and 22b by the DC power supply E2, an attractive force dominated by the gradient force is generated.

[0017] Here, the volume resistivity of the dielectric layer 1 (specifically, the portion located above the region where the second electrode portions 22a and 22b are formed) is 10 12 If the volume resistivity of the low volume resistivity layer is less than 10 Ωcm, even if the DC voltage applied to the second electrode portions 22a and 22b is increased, it is not possible to effectively exert an attractive force in which the gradient force is dominant. 6 Ωcm~10 12 If the resistance is outside the Ωcm range, the Johnsen-Rahbek force will not be the dominant adsorption force. Low volume resistivity layer 1c can be formed by, for example, doping (adding) a predetermined dopant to the dielectric material to form a spray material, and then spraying this. When the dielectric material is mainly composed of Al2O3, at least one dopant selected from TiO2, Cr, Ca, Mg, SiO2, and C can be used. Low volume resistivity layer The method for forming 1c is not limited to this, and for example, a dopant material can be doped (injected) using an ion implantation device. Hereinafter, an example of a method for manufacturing the electrostatic chuck EC of this embodiment will be described with reference to FIG.

[0018] A dielectric material mainly composed of Al2O3 (alumina) was used as the spray material, and as shown in Figure 3(a), a known spraying device was used to spray the entire upper surface of the base Bp, resulting in a volume resistivity of 10 12A dielectric layer (referred to as the first dielectric layer 1a) having a resistivity of Ωcm or more is formed to a predetermined thickness (first step). Next, a metal material containing molybdenum as a main component is used as a sputtering target, and a known sputtering device is used to simultaneously pattern and form a pair of positive and negative first electrodes 21a, 21b and a pair of positive and negative second electrodes 22a, 22b on the upper surface of the first dielectric layer 1a, as shown in FIG. 3(b) (second step). A mask plate having openings corresponding to the first electrodes 21a, 21b and the second electrodes 22a, 22b may be used for the patterning.

[0019] 3(c), a mask plate Mp1 having an area equivalent to that of the upper surface of the first dielectric layer portion 1a and provided with openings Mo that vertically coincide with the regions where the second electrode portions 22a, 22b are formed is placed on the first dielectric layer portion 1a on which the first electrode portions 21a, 21b and the second electrode portions 22a, 22b are formed. In this state, a dielectric material of the same quality as that used in the first step is used as the spray material, and a known spraying device is used to spray the upper surface of the first dielectric layer portion 1a so as to cover the regions where the second electrode portions 22a, 22b are formed, thereby forming a dielectric film having a volume resistivity of 10 12 A dielectric layer (referred to as the second dielectric layer 1b) having a resistance of Ωcm or more is formed to a predetermined thickness. At this time, the sprayed material is also filled between the first electrode portions 21a, 21b and the second electrode portions 22a, 22b that are adjacent to each other (in the left-right direction in FIG. 1).

[0020] Next, as shown in Fig. 3(d), a plate Mp2 having an area matching the upper surface of the second dielectric layer portion 1b is placed on the second dielectric layer portion 1b. In this state, the conductive material used in the first step to which a dopant is added at a predetermined weight ratio is used as the thermal spray material, and a known thermal spraying device is used to thermally spray the upper surface of the first dielectric layer portion 1a so as to cover the area where the first electrode portions 21a and 21b are formed. 6 Ωcm~10 12A dielectric layer (referred to as the third dielectric layer portion 1c) is formed with a predetermined thickness as a low resistivity layer in the Ωcm range (third step). At least one dopant selected from TiO2, Cr, Ca, Mg, SiO2, and C is added in a predetermined weight ratio. Finally, the upper surfaces of the second dielectric layer portion 1b and the third dielectric layer portion 1c are machined to be flat.

[0021] According to the above embodiment, when a conductive film is formed on the substrate Sw, after the substrate is placed on the electrostatic chuck Ec, a DC voltage is applied between the pair of positive and negative second electrodes 22a, 22b by the first power supply E1, and an attracting force dominated by the gradient force is generated, and the substrate Sw is attracted to the upper surface of the dielectric layer 1. Then, once a conductive film is formed on the surface of the substrate Sw, a DC voltage is applied between the first electrodes 21a, 21b, and an attracting force dominated by the Johnsen-Rahbek force is generated, and the attracted state of the substrate Sw to the upper surface of the dielectric layer 1 is maintained. As described above, in the electrostatic chuck EC of this embodiment, the portions of the dielectric layer located above the first electrode portions 21 a, 21 b and the second electrode portions 22 a, 22 b are made up of the second dielectric layer portion 1 b and the third dielectric layer portion 1 c having different volume resistivities. This makes it possible to constantly obtain an equivalent attracting force, even when an attracting force dominated by the Johnsen-Rahbek force or the gradient force is exerted to attract the substrate Sw. As a result, the substrate Sw can be attracted and held with a substantially constant attracting force while a conductive film is being formed on the substrate Sw. Furthermore, since the second dielectric layer 1 b and the third dielectric layer 1 c are formed by thermal spraying, the second dielectric layer 1 b and the third dielectric layer 1 c having different volume resistivities and a uniform interface in the vertical direction are formed, and therefore problems such as dielectric breakdown do not occur. Note that the interface between the second dielectric layer 1 c and the third dielectric layer 1 b is preferably located along a vertical line passing through substantially the midpoint between the first electrode portions 21 a, 21 b and the second electrode portions 22 a, 22 b, which are adjacent to each other.

[0022] Next, to confirm the effectiveness of the present invention, the electrostatic chuck (invention product) manufactured by the above-described manufacturing method was used. The dielectric material was primarily composed of Al2O3, and the dielectric material constituting the low volume resistivity layer was the same as that used in the first step, with TiO2 added at a predetermined weight ratio. The clamping force was measured when clamping a substrate Sw. As a comparison product, a dielectric layer was formed integrally over the entire surface of the first dielectric layer 1c using a known thermal spraying device, using the same dielectric material as used in the first step as the spraying material in the third step. As shown in Figure 4, the comparative product had a clamping force of approximately 500 Pa when a voltage of 3 V was applied to the first electrodes 21a and 21b by the DC power supply E1. In contrast, the clamping force of the invention product increased as the voltage applied to the first electrodes 21a and 21b by the DC power supply E1 increased, and a strong clamping force of approximately 2000 Pa was obtained at a voltage of 3 V.

[0023] Although the above describes an embodiment of the present invention, various modifications are possible without departing from the scope of the technical concept of the present invention. In the above embodiment, the first electrodes 21a, 21b are described as being bipolar. However, when applied to a device that performs a film formation process using a plasma atmosphere, they can also be configured as being monopolar. Furthermore, in the above embodiment, the second electrodes 22a, 22b are arranged in the center, with the first electrodes 21a, 21b on either side. However, this is not limited to this. The electrode arrangement can be appropriately changed depending on the size and shape of the substrate Sw to be attracted by exerting an attraction force dominated by Johnsen-Rahbek force or gradient force. Furthermore, the method of forming the first and second electrodes 21a, 21b, 22a, 22b is not limited to the above examples; they can also be formed by thermal spraying or plating. [Explanation of symbols]

[0024] EC...electrostatic chuck, 1...dielectric layer, 1a...first dielectric layer portion (constituent element of dielectric layer), 1b...second dielectric layer portion (constituent element of dielectric layer), 1c...third dielectric layer portion (low volume resistivity layer: constituent element of dielectric layer), 2...electrode layer, 21a, 21b...first electrode portion, 22a, 22b...second electrode portion, Bp...base, Sw...substrate.

Claims

1. An electrostatic chuck provided on a surface of a base placed in a vacuum chamber in which a conductive film is formed on the surface of an insulating object to be attracted, and which attracts the object to be attracted, Volume resistivity is 10 １２ A capacitor comprising a dielectric layer having a resistance of Ωcm or more and an electrode layer embedded in the dielectric layer, the electrode layer having a flat first electrode portion and a pair of positive and negative second electrode portions having a line width narrower than that of the first electrode portion and arranged close to each other, a portion of the dielectric layer located above the first electrode portion, with the attracting surface of the dielectric layer facing upward, comprising a low volume resistivity layer having locally reduced volume resistivity; an electrostatic chuck configured such that application of a DC voltage between the positive and negative electrodes of a second electrode unit generates an attractive force dominated by a gradient force, thereby attracting the object to the upper surface of the dielectric layer; and when application of a DC voltage to the first electrode unit causes a conductive film to be formed on the surface of the object, application of a Johnsen-Rahbek force dominantly generates an attractive force, thereby attracting the object to the upper surface of the dielectric layer.

2. The volume resistivity of the low volume resistivity layer is 10 ６ Ωcm to 10 １２ 2. The electrostatic chuck of claim 1, wherein the resistance is set in the range of Ωcm.

3. 2. The electrostatic chuck of claim 1, wherein the low volume resistivity layer is formed by doping the dielectric layer with a dopant.

4. 4. The electrostatic chuck according to claim 3, wherein the dielectric layer and the low volume resistivity layer are formed by thermal spraying.

5. 5. The electrostatic chuck of claim 4, wherein the dielectric layer is Al. ２ O ３ In the composition containing the above as a main component, the dopant is TiO ２ , Cr, Ca, Mg, SiO ２ and C.

6. The method for manufacturing an electrostatic chuck according to any one of claims 1 to 5, The dielectric layer is composed of a first dielectric layer portion, a second dielectric layer portion, and a third dielectric layer portion, and a dielectric film having a volume resistivity of 10 １２ a first step of forming the first dielectric layer portion having a resistivity of Ωcm or more by thermal spraying; a second step of forming the first electrode portion in a flat plate shape and a pair of positive and negative second electrode portions having a line width narrower than that of the first electrode portion and arranged close to each other on the surface of the first dielectric layer portion; and a third step of forming, by thermal spraying, on a surface of the first dielectric layer portion, the second dielectric layer portion having a volume resistivity equivalent to that of the first dielectric layer portion so as to cover the second electrode portion, and a third dielectric layer portion as the low volume resistivity layer having a volume resistivity lower than that of the first dielectric layer portion so as to cover the first electrode portion.

7. 7. The method for manufacturing an electrostatic chuck according to claim 6, wherein the same dielectric material is used as the spray material for the first dielectric layer portion and the second dielectric layer portion, and the same dielectric material doped with a dopant at a predetermined weight ratio is used as the spray material for the third dielectric layer portion.

8. 8. The method for manufacturing an electrostatic chuck according to claim 7, wherein the third dielectric layer portion is Al. ２ O ３ In the composition containing the above as a main component, the dopant is TiO ２ , Cr, Ca, Mg, SiO ２ and C.

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