Electrostatic Chuck

Abstract

An electrostatic chuck according to the present disclosure includes a plate-like body having an adsorption surface for mounting an object to be adsorbed, a base body, and an electrode film positioned between the plate-like body and the base body. The plate-like body and the substrate are formed of sapphire. The angle formed by the adsorption surface and the c-plane of the sapphire is greater than or equal to 45°.

Description

[Technical field]

[0001] The present disclosure relates to electrostatic chucks. [Background technology]

[0002] In the manufacturing process of semiconductor products, covered Electrostatic chucks are used to attract and hold objects. Sapphire is a transparent insulator and can be used as an electrostatic chuck for applications requiring transparency, such as inspection equipment (Patent Document 1). Sapphire has superior wear resistance and is less susceptible to scratches than glass. Furthermore, sapphire also has excellent corrosion resistance, and can be used in the substrate attraction portion of plasma processing equipment and the like. However, sapphire has anisotropy, and there is a problem in that the attraction force differs depending on the plane orientation, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-291175 Summary of the Invention [Means for solving the problem]

[0004] The electrostatic chuck according to the present disclosure includes a plate-like body having an adsorption surface for placing an object to be adsorbed, a base, and an electrode film located between the plate-like body and the base. The plate-like body and the base are made of sapphire. The angle between the adsorption surface and the c-plane of the sapphire is 45° or more. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is an explanatory diagram illustrating an electrostatic chuck according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is an explanatory diagram showing the crystal structure of sapphire. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] As described above, although sapphire has wear resistance and corrosion resistance, it has anisotropy, and there is a problem in that the adsorptive force varies depending on the plane orientation, etc. Therefore, an electrostatic chuck having excellent adsorptive force is required.

[0007] In the electrostatic chuck according to the present disclosure, a plate-shaped body having an adsorption surface for placing an object to be adsorbed is made of sapphire, and the adsorption surface forms an angle of 45° or more with the c-plane of the sapphire. Therefore, the electrostatic chuck according to the present disclosure has an excellent adsorption force.

[0008] As described above, the electrostatic chuck according to the present disclosure includes a plate-like body having an adsorption surface for placing an object to be adsorbed, a base body, and an electrode film located between the plate-like body and the base body. The electrostatic chuck according to the present disclosure will be described with reference to FIGS. 1 and 2.

[0009] As shown in FIG. 1 , an electrostatic chuck 1 according to one embodiment of the present disclosure includes a plate-like body 11 having an adsorption surface 11a for placing an object to be adsorbed 2 thereon, a base body 13, an electrode film 12 positioned between the plate-like body 11 and the base body 13, and a pedestal 14.

[0010] The plate-like body 11 is made of sapphire, and the shape and size are not limited as long as it is plate-like. The shape and size of the plate-like body 11 are appropriately set, for example, according to the shape and size of the object 2 to be attracted. When viewed from above, the plate-like body 11 may have, for example, a circular shape, an elliptical shape, or a polygonal shape (triangular, rectangular, pentagonal, hexagonal, etc.). The plate-like body 11 has a thickness of, for example, 0.1 mm or more and 0.4 mm or less, and the attracting surface 11a of the plate-like body 11 is, for example, 100 mm or more. 400 It may have a diameter (width) of mm or less.

[0011] The sapphire forming the plate-like body 11 is a single crystal of aluminum oxide (Al2O3). Sapphire is a transparent insulator and has excellent scratch resistance, heat resistance, thermal conductivity, and the like.

[0012] In the electrostatic chuck 1 according to one embodiment, the angle between the adsorption surface 11a of the plate-like body 11 and the c-plane of the sapphire is 45° or more. Here, the crystal planes of sapphire will be described. FIG. 2 shows the crystal structure of sapphire. As shown in FIGS. 2(A) to (D), sapphire has a hexagonal structure, and the representative crystal planes are the c-plane, the m-plane, the a-plane, and the r-plane. The axes perpendicular to these planes are called the c-axis, the m-axis, the a-axis, and the r-axis, respectively.

[0013] "The angle between the adsorption surface 11a and the c-plane of sapphire is 45° or more" means that, for example, when a sapphire ingot is processed to obtain the plate-shaped body 11, the adsorption surface 11a of the plate-shaped body 11 is formed so as to be inclined at 45° or more with respect to the c-plane shown in Fig. 2(A). The maximum angle between the adsorption surface 11a and the c-plane of sapphire is 90°, and when the angle is 90°, the adsorption surface 11a is formed so as to be perpendicular to the c-plane (parallel to the c-axis). In order to further improve the adsorption force, the angle between the adsorption surface 11a and the c-plane of sapphire may be 60° or more, and more preferably 75° or more.

[0014] In particular, it is preferable that the adsorption surface 11a is the r-plane of sapphire shown in Fig. 2(D). The r-plane of sapphire is inclined at about 57.6° with respect to the c-plane of sapphire. The r-plane of sapphire has good plasma resistance and is therefore unlikely to be damaged by, for example, plasma etching. Furthermore, the r-plane of sapphire is a cleavage plane, which is excellent in processability and productivity, and can easily produce a mirror surface.

[0015] If the angle between the adsorption surface 11a and the c-plane of sapphire is 45° or more, an excellent adsorption force can be exhibited based on the following relational formula (I). Adsorption force F=(S / 2)×ε0×εr×(V / d) 2 (I) S: electrostatic electrode area ε0: Dielectric constant of vacuum εr: relative dielectric constant of the insulator V: Applied voltage d: thickness of the insulating layer

[0016] That is, if εr (relative dielectric constant of an insulator) is large, the adsorption force F becomes large, so the dielectric constant of the adsorption surface 11a should be made large. In sapphire, the relative dielectric constant of the c-plane (plane perpendicular to the c-axis) is the smallest, and the relative dielectric constant of a plane parallel to the c-axis such as the a-plane and m-plane is the largest. In other words, a plane that forms a larger angle with the c-plane (inclination from the c-plane) has a larger dielectric constant. Therefore, in the electrostatic chuck 1 according to one embodiment, the angle formed by the adsorption surface 11a and the c-plane of sapphire is specified to be 45° or more.

[0017] The base 13 is a member for fixing the plate-like body 11, and is made of sapphire. As sapphire has been described above, a detailed description will be omitted. In the electrostatic chuck 1 according to one embodiment, the plate-like body 11 and the base 13 are made of transparent sapphire, and have excellent light transmittance. Since the base 13 does not contribute to electrostatic adsorption, sapphire with a crystal orientation that has a relatively large relative dielectric constant may be used. For example, the c-plane has no anisotropy of the refractive index (birefringence) and has no in-plane thermal expansion. rate Since it has no anisotropy, it is suitable for the substrate 13. No birefringence occurs in the planes perpendicular to the c plane, such as the a-plane and m-plane. Furthermore, the a-plane has high mechanical strength (bending strength).

[0018] The shape and size of the base 13 are not limited, and are appropriately set according to the shape and size of the plate-like body 11, for example. The base 13 may have, for example, a circular shape, an elliptical shape, or a polygonal shape (such as a triangular shape, a rectangular shape, a pentagonal shape, or a hexagonal shape) when viewed in a plane. The base 13 may have a thickness of, for example, 1 mm or more and 50 mm or less, and may have a thickness greater than that of the plate-like body 11, for example. The surface of the base 13 facing the plate-like body 11 has approximately the same shape and area as the surface of the plate-like body 11 facing the base 13, and may have a diameter (width) of, for example, 100 mm or more and 400 mm or less. As shown in the relational formula (I), the smaller the thickness of the plate-like body 11, the greater the adsorption force of the electrostatic chuck 1. Conversely, the greater the thickness of the base 13, the greater the mechanical strength of the electrostatic chuck 1. If the base 13 has a thickness greater than that of the plate-like body, an electrostatic chuck 1 with high adsorption force and mechanical strength can be provided.

[0019] Sapphire also has anisotropy in thermal expansion coefficient, and the thermal expansion coefficient is maximum in a direction parallel to the c-axis, increases in a direction closer to the c-axis, and decreases in a direction farther from the c-axis. In the electrostatic chuck 1 according to one embodiment, the plate-like body 11 and the base body 13 are preferably provided to face each other so that the c-axis of the sapphire forming the plate-like body 11 and the c-axis of the sapphire forming the base body 13 are non-parallel. By providing the plate-like body 11 and the base body 13 in this manner, deformation caused by the anisotropy of the thermal expansion coefficient of the plate-like body 11 is further reduced (cancelled).

[0020] The electrode film 12 is located between the plate-like body 11 and the base 13, and is electrically connected to an external power source 3. The shape and thickness of the electrode film 12 are not limited and are appropriately set according to the shapes and sizes of the plate-like body 11 and the base 13. The electrode film 12 is preferably light-transmitting, and examples of the electrode film include an ITO (indium tin oxide) film, a tin oxide film, and a zinc oxide film.

[0021] The base 14 is a member for supporting the laminated plate-like bodies 11, the electrode film 12, and the base 13, and is provided so that the base 13 is in contact with the base 14. The shape and size of the base 14 are not limited as long as it can support the laminated plate-like bodies 11, the electrode film 12, and the base 13. The base 14 is formed of, for example, a metal, a resin, a ceramic, or the like.

[0022] 1, electrode lead-out portions 13a, 14a are formed on the base 13 and the pedestal 14, and the electrode film 12 and the external power source 3 are electrically connected via these electrode lead-out portions 13a, 14a. The electrode lead-out portions 13a, 14a are formed by providing through holes in the base 13 and the pedestal 14. A conductor for connecting the electrode film 12 and the power source 3 passes through the through holes (electrode lead-out portions 13a, 14a), and the electrode film 12 and the power source 3 are electrically connected.

[0023] There is no limitation on the method for bonding the plate-like body 11 and the base body 13. Examples of the bonding method include a method of bonding using a UV-curable adhesive, and a method of directly bonding them by diffusion bonding or the like.

[0024] The electrostatic chuck 1 according to an embodiment is provided in, for example, an inspection device. Examples of the inspection device include an appearance inspection device. The appearance inspection device includes a light source, a mounting unit, and an imaging unit, and inspects the appearance shape of an inspection object placed on the mounting unit. If a mounting unit that is transparent to the light from the light source is used, the light source, the inspection object, and the imaging unit can be arranged on the same straight line, so that the inspection accuracy can be improved with a simple configuration. In such an inspection device, the electrostatic chuck 1 attracts and holds the inspection object (attached object 2), and the inspection object is inspected. Examples of the inspection object (attached object 2) include a substrate and an element made of a semiconductor, metal, ceramic, resin, single crystal, etc.

[0025] A method for attracting the object 2 to the electrostatic chuck 1 according to one embodiment is, for example, as follows. When a voltage is applied between the electrode film 12 and the object 2 by the power source 3, the plate-like body 11 made of sapphire is dielectrically polarized. As a result, the object 2 can be attracted to the attracting surface 11a of the plate-like body 11 by Coulomb force. Both the positive electrode and the negative electrode may be formed as the electrode film 12 between the plate-like body 11 and the base body 13.

[0026] In the electrostatic chuck 1 according to the embodiment, the angle between the attracting surface 11a of the plate-like body 11 and the c-plane of the sapphire is 45° or more. Therefore, the electrostatic chuck 1 according to the embodiment can attract the object 2 to be attracted with a strong attracting force.

[0027] The electrostatic chuck according to the present disclosure is not limited to the electrostatic chuck 1 according to the embodiment described above. In the electrostatic chuck 1 according to the embodiment, the pedestal 14 is provided as described above and supports the laminated plate-like body 11, the electrode film 12, and the base body 13. However, in the electrostatic chuck according to the present disclosure, the pedestal is not an essential member, and the pedestal may not be provided.

[0028] The electrostatic chuck 1 according to one embodiment is a monopolar electrostatic chuck including one electrode film 12. However, the electrostatic chuck according to the present disclosure may be a bipolar electrostatic chuck including a plurality of electrode films. [Explanation of symbols]

[0029] 1. Electrostatic chuck 11 Plate-shaped body 11a Adsorption surface 12 Electrode membrane 13 Base 13a Electrode extraction part 14 Pedestal 14a Electrode extraction part 2 Adsorbed object 3 Power supply

Claims

1. a plate-like body having an adsorption surface on which an object to be adsorbed is placed; A substrate; an electrode film located between the plate-like body and the base; Including, the plate-like body and the base are made of sapphire, the plate-like body and the substrate are provided so as to face each other such that a c-axis of the sapphire forming the plate-like body and a c-axis of the sapphire forming the substrate are non-parallel to each other; the angle between the adsorption surface and the c-plane of the sapphire is 45° or more; Electrostatic chuck.

2. The electrostatic chuck according to claim 1 , wherein the base body has a thickness greater than that of the plate-like body.

3. The electrostatic chuck according to claim 1 , wherein the electrode film is light-transmitting.

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