Electrostatic chuck and substrate fixing device

Abstract

To provide an electrostatic chuck and substrate fixing device that can reduce the occurrence of electrical discharge. [Solution] The electrostatic chuck comprises a base having a first main surface and a second main surface opposite to the first main surface, and a porous body. The base has recesses that are recessed from the second main surface toward the first main surface, and a plurality of through holes that penetrate from the bottom surface of the recesses toward the first main surface. The porous body is filled into the recesses.

Description

Technical Field

[0001] The present disclosure relates to an electrostatic chuck and a substrate fixing device.

Background Art

[0002] Conventionally, a film forming apparatus (e.g., a CVD apparatus, a PVD apparatus, etc.) or a plasma etching apparatus used in manufacturing semiconductor devices such as ICs and LSIs has a stage for accurately holding a wafer in a vacuum processing chamber.

[0003] As such a stage, for example, a substrate fixing device has been proposed that adsorbs and holds a wafer, which is an object to be adsorbed, by an electrostatic chuck mounted on a base plate. As an example of the substrate fixing device, there is a structure provided with a gas supply unit for cooling the wafer. The gas is supplied to the surface of the electrostatic chuck through, for example, a gas flow path inside the base plate and a porous body or through holes of ceramics provided in the electrostatic chuck.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In an electrostatic chuck, discharge may occur in gas holes through which gas flows.

[0006] An object of the present disclosure is to provide an electrostatic chuck and a substrate fixing device that can make it difficult to generate discharge.

Means for Solving the Problems

[0007] According to one embodiment of the present disclosure, an electrostatic chuck is provided, comprising a substrate having a first main surface and a second main surface opposite to the first main surface, and a porous body, wherein the substrate has recesses that are recessed from the second main surface toward the first main surface, and a plurality of through holes that penetrate from the bottom surface of the recesses toward the first main surface, and the porous body is filled in the recesses. [Effects of the Invention]

[0008] According to this disclosure, it is possible to make it difficult to generate discharges. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view illustrating a substrate fixing device according to an embodiment. [Figure 2] This is a cross-sectional view illustrating a substrate fixing device according to an embodiment. [Figure 3] This is a plan view illustrating a gas vent. [Figure 4] This is a cross-sectional view illustrating a gas vent. [Figure 5] This is a diagram illustrating a porous material. [Figure 6] This is a cross-sectional view (part 1) illustrating a method for manufacturing a substrate fixing device according to an embodiment. [Figure 7] This is a cross-sectional view (part 2) illustrating a method for manufacturing a substrate fixing device according to an embodiment. [Figure 8] This is a cross-sectional view illustrating an electrostatic chuck of a substrate fixing device according to a comparative example. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configuration will be denoted by the same reference numerals to avoid redundant descriptions.

[0011] [Structure of Substrate Fixing Device] Embodiments relate to a substrate fixing device. FIG. 1 is a plan view illustrating a substrate fixing device according to an embodiment. FIG. 2 is a cross-sectional view illustrating the substrate fixing device according to the embodiment.

[0012] As shown in FIGS. 1 and 2, the substrate fixing device 1 according to the embodiment includes a base plate 10, an adhesive layer 20, and an electrostatic chuck 30.

[0013] The base plate 10 is a member for mounting the electrostatic chuck 30, and the electrostatic chuck 30 is fixed to the base plate 10. The thickness of the base plate 10 is, for example, about 20 mm to 40 mm. The base plate 10 is formed of, for example, aluminum and can be used as an electrode or the like for controlling plasma. By supplying a predetermined high-frequency power to the base plate 10, the energy for causing ions or the like in the generated plasma state to collide with the wafer adsorbed on the electrostatic chuck 30 can be controlled, and the etching process can be effectively performed.

[0014] Inside the base plate 10, a gas supply unit 11 for supplying a gas for cooling the wafer adsorbed and held by the electrostatic chuck 30 is provided. The gas supply unit 11 includes a gas flow path 111, a gas injection unit 112, and a gas discharge unit 113.

[0015] The gas flow path 111 is, for example, a hole formed annularly inside the base plate 10. The gas injection part 112 is a hole whose one end communicates with the gas flow path 111 and the other end is exposed to the outside from the lower surface 10b of the base plate 10, and an inert gas (for example, He, Ar, etc.) is introduced into the gas flow path 111 from the outside of the substrate fixing device 1. The gas discharge part 113 is a hole whose one end communicates with the gas flow path 111 and the other end is exposed to the outside from the upper surface 10a of the base plate 10 and penetrates the adhesive layer 20, and discharges the inert gas introduced into the gas flow path 111. The gas discharge parts 113 are scattered on the upper surface 10a of the base plate 10 in a plan view. The number of the gas discharge parts 113 can be appropriately determined as needed, but is, for example, about several tens to several hundreds. The gas discharge parts 113 are arranged at equal intervals, for example, on one circle.

[0016] Note that the plan view means viewing the object from the normal direction of the upper surface 10a of the base plate 10, that is, viewing from the normal direction of the mounting surface 31a of the base body 31 described later, and the planar shape means the shape of the object viewed from the normal direction of the upper surface 10a of the base plate 10.

[0017] A cooling mechanism 15 is provided inside the base plate 10. The cooling mechanism 15 includes a refrigerant flow path 151, a refrigerant introduction part 152, and a refrigerant discharge part 153. The refrigerant flow path 151 is, for example, a hole formed annularly inside the base plate 10. The refrigerant introduction part 152 is a hole whose one end communicates with the refrigerant flow path 151 and the other end is exposed to the outside from the lower surface 10b of the base plate 10, and a refrigerant (for example, cooling water, fluorine-based fluid, etc.) is introduced into the refrigerant flow path 151 from the outside of the substrate fixing device 1. The refrigerant discharge part 153 is a hole whose one end communicates with the refrigerant flow path 151 and the other end is exposed to the outside from the lower surface 10b of the base plate 10, and discharges the refrigerant introduced into the refrigerant flow path 151.

[0018] The cooling mechanism 15 is connected to a refrigerant control device (not shown) located outside the substrate fixing device 1. The refrigerant control device (not shown) introduces refrigerant from a refrigerant introduction section 152 into a refrigerant flow path 151 and discharges refrigerant from a refrigerant discharge section 153. By circulating the refrigerant through the cooling mechanism 15 and cooling the base plate 10, the wafer adsorbed on the electrostatic chuck 30 can be cooled.

[0019] The electrostatic chuck 30 is the part that adsorbs and holds the wafer, which is the object to be adsorbed. The planar shape of the electrostatic chuck 30 is, for example, circular. The diameter of the wafer, which is the object to be adsorbed by the electrostatic chuck 30, is, for example, 203.2 mm (8 inches), 304.8 mm (12 inches), or 457.2 mm (18 inches).

[0020] The electrostatic chuck 30 is provided on the upper surface 10a of the base plate 10 via an adhesive layer 20. The adhesive layer 20 is, for example, a silicone-based adhesive. The thickness of the adhesive layer 20 is, for example, about 0.1 mm to 1.0 mm. The adhesive layer 20 not only bonds the base plate 10 and the electrostatic chuck 30, but also has the effect of reducing stress caused by the difference in thermal expansion coefficients between the ceramic electrostatic chuck 30 and the aluminum base plate 10.

[0021] The electrostatic chuck 30 comprises a base body 31, an electrostatic electrode 32, and a porous body 60. The upper surface of the base body 31 is the mounting surface 31a of the object to be adsorbed. The lower surface 31b of the base body 31, which is the opposite surface of the mounting surface 31a, faces the base plate 10. The electrostatic chuck 30 is, for example, a Coulomb force type electrostatic chuck. The mounting surface 31a is an example of a first main surface, and the lower surface 31b is an example of a second main surface.

[0022] The substrate 31 is a dielectric, and as the substrate 31, ceramics such as aluminum oxide (Al2O3) or aluminum nitride (AlN) are used. The substrate 31 may also contain oxides of two or more elements selected from silicon (Si), magnesium (Mg), calcium (Ca), aluminum (Al), and yttrium (Y) as auxiliary agents. The thickness of the substrate 31 is, for example, about 5 mm to 10 mm, and the relative permittivity (1 kHz) of the substrate 31 is, for example, about 9 to 10. The volume resistivity of the substrate 31 is, for example, 1 × 10⁻⁶. 15 It is greater than or equal to Ω·m.

[0023] The electrostatic electrode 32 is a thin-film electrode and is embedded in the substrate 31. The electrostatic electrode 32 is connected to a power supply located outside the substrate fixing device 1, and when a predetermined voltage is applied from the power supply, it generates an electrostatic attraction force between itself and the wafer. This allows the wafer to be attracted and held on the mounting surface 31a of the substrate 31 of the electrostatic chuck 30. The attraction force increases with increasing voltage applied to the electrostatic electrode 32. The electrostatic electrode 32 may be unipolar or bipolar. Examples of materials used for the electrostatic electrode 32 include tungsten and molybdenum.

[0024] A heating element may be provided inside the base 31, which generates heat when a voltage is applied from outside the substrate fixing device 1, thereby heating the mounting surface 31a of the base 31 to a predetermined temperature.

[0025] Gas holes 33 are provided at positions corresponding to each gas discharge section 113 of the base body 31, penetrating the base body 31 and exposing the other end of the gas discharge section 113. Gas is supplied from the gas supply section 11 to the mounting surface 31a through the gas holes 33. As shown in Figure 1, for example, multiple gas holes 33 are arranged at equal intervals on a single circle 70.

[0026] Here, we will describe the gas vent 33. Figure 3 is a plan view illustrating the gas vent 33. Figure 4 is a cross-sectional view illustrating the gas vent 33. Figure 4 corresponds to a cross-sectional view along line IV-IV in Figure 3.

[0027] As shown in Figures 2, 3, and 4, each gas hole 33 has a recess 331 that is recessed from the lower surface 31b of the base 31 toward the mounting surface 31a, and a plurality of through holes 332 that penetrate from the bottom surface 331a of the recess 331 to the mounting surface 31a. The recess 331 and the through holes 332 are in communication with each other. In a plan view, the size of the through holes 332 is smaller than the size of the recess 331. The number of through holes 332 for each gas hole 33 is, for example, 10 to 200, preferably 50 to 150, and more preferably 75 to 125. When a plurality of gas holes 33 are arranged at equal intervals on a circle 70, the plurality of recesses 331 are also arranged at equal intervals on a circle 70.

[0028] As shown in Figure 3, the multiple through holes 332 are arranged on multiple concentric circles, for example, in a plan view. In one example, the multiple through holes 332 are arranged on four concentric circles 81, 82, 83, and 84. Preferably, the spacing between the multiple through holes 332 arranged on each of the circles 81, 82, 83, and 84 is constant for each circle.

[0029] The planar shape of the recess 331 and the through hole 332 is, for example, circular. Hereafter, an example will be given where the planar shape of the recess 331 and the through hole 332 is circular. The inner diameter of the through hole 332 is smaller than the inner diameter of the recess 331. The inner diameter of the recess 331 is, for example, about 1 mm to 5 mm. The inner diameter of the through hole 332 is, for example, about 1 μm to 50 μm, preferably 20 μm to 40 μm, and more preferably 25 μm to 35 μm. An example of a combination of the inner diameters of the recess 331 and the through hole 332 is that the inner diameter of the recess 331 is 2 mm and the inner diameter of the through hole 332 is 30 μm. The depth of the recess 331 is, for example, about 4 mm to 8 mm. The depth of the through hole 332 is, for example, about 0.1 mm to 1 mm, preferably 0.2 mm to 0.8 mm, and more preferably 0.3 mm to 0.7 mm.

[0030] Now, let's describe the porous body 60. Figure 5 is an example of the porous body 60. Figure 5 is a magnified view of part A in Figure 4.

[0031] As shown in Figure 4, the porous body 60 fills the entire area within the recess 331. The through-hole 332 is not filled with the porous body 60. As shown in Figure 5, the porous body 60 contains a plurality of spherical oxide ceramic particles 601 and a mixed oxide 602 that binds and integrates the plurality of spherical oxide ceramic particles 601.

[0032] The diameter of the spherical oxide ceramic particles 601 is, for example, about 30 μm to 1000 μm. A preferred example of the spherical oxide ceramic particles 601 is spherical aluminum oxide particles. Furthermore, it is preferable that the spherical oxide ceramic particles 601 are contained in the porous body 60 in a mass ratio of 80% by mass or more (97% by mass or less).

[0033] The mixed oxide 602 adheres to and supports a portion of the outer surface (spherical surface) of multiple spherical oxide ceramic particles 601. The mixed oxide 602 is formed from oxides of two or more elements selected from, for example, silicon (Si), magnesium (Mg), calcium (Ca), aluminum (Al), and yttrium (Y).

[0034] Multiple pores P are formed inside the porous body 60. The pores P communicate with the outside so that gas can flow from the bottom to the top of the porous body 60. Preferably, the porosity of the pores P formed inside the porous body 60 is about 20% to 50% of the total volume of the porous body 60. On the inner surface of the pores P, a portion of the outer surface of the spherical oxide ceramic particles 601 and the mixed oxide 602 are exposed.

[0035] Furthermore, when the substrate 31 is formed from aluminum oxide, it is preferable that the substrate 31 contains oxides of two or more elements selected from silicon, magnesium, calcium, and yttrium as other components. It is preferable that the composition ratio of oxides of two or more elements selected from silicon, magnesium, calcium, and yttrium in the substrate 31 is the same as the composition ratio of oxides of two or more elements selected from silicon, magnesium, calcium, and yttrium in the mixed oxide 602 of the porous body 60.

[0036] In this way, by making the oxide composition ratio the same between the substrate 31 and the mixed oxide 602 of the porous body 60, mass transfer does not occur between them when the porous body 60 is sintered, thus ensuring the flatness of the interface between the substrate 31 and the porous body 60.

[0037] [Manufacturing method for substrate fixing device] Next, the manufacturing method of the substrate fixing device 1 will be described. Figures 6 and 7 are cross-sectional views illustrating the manufacturing method of the substrate fixing device 1 according to the embodiment. Figures 6 and 7 show cross-sections corresponding to Figure 4. Here, referring to Figures 6 and 7, the process of forming gas holes 33 in the electrostatic chuck 30 will be described, focusing on the steps involved.

[0038] First, a substrate 31 containing an electrostatic electrode 32 is manufactured by a well-known manufacturing method that includes steps such as processing a green sheet with vias, filling the vias with conductive paste, forming a pattern to become an electrostatic electrode, laminating and firing other green sheets, and flattening the surface.

[0039] Next, as shown in Figure 6(a), recesses 331 are formed in the lower surface 31b of the base body 31 toward the mounting surface 31a. As mentioned above, the recesses 331 are, for example, circular in shape, with an inner diameter of about 1 mm to 5 mm and a depth of about 4 mm to 8 mm. The recesses 331 are formed, for example, by drilling, at positions corresponding to the gas discharge sections 113 of the base plate 10, in a number corresponding to the gas discharge sections 113.

[0040] Next, as shown in Figure 6(b), a plurality of through holes 332 are formed that penetrate from the bottom surface 331a of the recess 331 to the mounting surface 31a. As mentioned above, the through holes 332 are, for example, circular in shape, with an inner diameter of about 1 μm to 50 μm and a depth of about 0.1 mm to 1 mm. The through holes 332 are formed on a plurality of concentric circles by laser processing using, for example, a short-pulse deep ultraviolet (DUV) laser (see Figure 3).

[0041] Next, as shown in Figure 7, a porous body 60 is formed in the recess 331. The porous body 60 can be formed by filling the recess 331 with a paste that will serve as a precursor to the porous body 60 using a squeegee or the like, and then sintering it. If a part of the porous body 60 protrudes from the lower surface 31b of the base body 31, grinding or the like is performed so that the end face of the porous body 60 becomes substantially flush with the lower surface 31b of the base body 31. Here, the through holes 332 are necessary as escape routes for air when filling the recess 331 with the paste that will serve as a precursor to the porous body 60, and play a role in promoting the filling of the paste. A part of the porous body 60 may enter into the through holes 332, but if the inner diameter of the through holes 332 is large, the paste will flow out, so it is preferable to make the inner diameter of the through holes 332 appropriately small.

[0042] The paste that serves as a precursor for the porous body 60 contains, for example, spherical aluminum oxide particles in a predetermined mass ratio. The remainder of the paste contains oxides of two or more elements selected from, for example, silicon, magnesium, calcium, aluminum, and yttrium, and further contains an organic binder and a solvent. For example, polyvinyl butyral can be used as the organic binder. For example, alcohol can be used as the solvent.

[0043] Next, a base plate 10 with a pre-formed cooling mechanism 15 etc. is prepared, and an adhesive layer 20 (uncured) is formed on the base plate 10. Then, the structure shown in Figure 7 is placed on the base plate 10 via the adhesive layer 20, and the adhesive layer 20 is cured.

[0044] In this way, the substrate fixing device 1 can be manufactured.

[0045] Here, the effects of the substrate fixing device 1 will be explained with reference to comparative examples. Figure 8 is a cross-sectional view illustrating the electrostatic chuck of the substrate fixing device according to the comparative example. As shown in Figure 8, the electrostatic chuck 30X of the substrate fixing device according to the comparative example differs from the electrostatic chuck 30 of the substrate fixing device 1 (see Figures 1 to 4) in that the gas holes 33 are replaced with gas holes 33X.

[0046] Each gas hole 33X consists of a recess 331 and a through hole 332X that penetrates from the bottom surface 331a of the recess 331 to the mounting surface 31a. The recess 331 and the through hole 332X are, for example, concentrically arranged and in communication with each other. In a plan view, the size of the through hole 332X is smaller than the size of the recess 331. For example, the inner diameter of the recess 331 is 2 mm, and the inner diameter of the through hole 332X is 300 μm.

[0047] If the substrate fixing device 1 has 100 through-holes 332 for each gas hole 33 and an inner diameter of 30 μm, then in a plan view, the total area of ​​the through-holes 332 for each gas hole 33 of the substrate fixing device 1 is (π × (15 μm)). 2 (×100) is the area of ​​the through-hole 332X of the gas hole 33X in the substrate fixing device according to the comparative example (π × (150 μm) 2 ) is equal to ). Therefore, when the flow rate of gas supplied from the gas supply unit 11 is equal, the flow rate of gas supplied to the mounting surface 31a through the gas holes 33 is equal to the flow rate of gas supplied to the mounting surface 31a through the gas holes 33X. On the other hand, the flow rate of gas flowing through each of the through holes 332 is 1 / 100 of the flow rate of gas flowing through the through hole 332X, so discharge is less likely to occur in the through hole 332 than in the through hole 332X. Thus, according to this embodiment, it is possible to reduce the occurrence of discharge while avoiding a decrease in cooling efficiency.

[0048] Furthermore, in a plan view, when multiple through holes 332 are arranged on multiple concentric circles 81-84, the isotropy of the gas flow around each gas hole 33 is high, and good uniformity in cooling efficiency can be obtained. In particular, if the spacing between multiple through holes 332 arranged on the same circle is constant, even better uniformity in cooling efficiency can be obtained. Moreover, in a plan view, when multiple recesses 331 are arranged at equal intervals on a single circle 70, the isotropy of the gas flow is high across the entire mounting surface 31a, and good uniformity in cooling efficiency can be obtained.

[0049] Although preferred embodiments have been described in detail above, this disclosure is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims. [Explanation of symbols]

[0050] 1 Board fixing device 10 base plate 11. Gas Supply Department 15 Cooling mechanism 20 Adhesive layer 30 Electrostatic Chuck 31 Base 31a Mounting surface 31b Bottom side 32 electrostatic electrodes 33 Gas holes 60 Porous material 70, 81, 82, 83, 84 yen 331 Recess 331a Bottom 332 Through hole

Claims

1. A substrate having a first principal surface and a second principal surface opposite to the first principal surface, Porous material and It has, The substrate, A recess extending from the second main surface toward the first main surface, Multiple through holes extending from the bottom surface of the recess to the first main surface, Formed, The porous material is filled in the recess and is an electrostatic chuck.

2. In a plan view, the plurality of through holes are arranged on a plurality of concentric circles, as described in claim 1 of the electrostatic chuck.

3. The electrostatic chuck according to claim 2, wherein the spacing between the plurality of through holes arranged on the same circle is constant.

4. The volume resistivity of the substrate is 1 × 10 １５ An electrostatic chuck according to any one of claims 1 to 3, wherein the ohm is Ω·m or greater.

5. The porous body has a plurality of interconnected pores, The electrostatic chuck according to any one of claims 1 to 3, wherein gas flows from the second main surface to the first main surface through the plurality of communicating pores.

6. The electrostatic chuck according to any one of claims 1 to 3, wherein the substrate and the porous body are made of the same oxide ceramic.

7. The electrostatic chuck according to claim 6, wherein the oxide ceramic is aluminum oxide.

8. The substrate and the porous body contain oxides of two or more identical elements. The electrostatic chuck according to any one of claims 1 to 3, wherein the composition ratio of the oxide in the substrate is the same as the composition ratio of the oxide in the porous body.

9. The electrostatic chuck according to claim 8, wherein the two or more elements are selected from silicon, magnesium, calcium, and yttrium.

10. The electrostatic chuck according to any one of claims 1 to 3, wherein, in a plan view, a plurality of the recesses are arranged at equal intervals on a single circle.

11. A base plate equipped with a gas supply unit inside, An electrostatic chuck according to any one of claims 1 to 3, fixed to the base plate, It has, The second main surface faces the base plate, A substrate fixing device in which gas is supplied from the gas supply unit toward the recess.

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