Heater unit and electrostatic chuck

Abstract

Provided are a heater unit and an electrostatic chuck capable of improving temperature uniformity. This heater unit comprises: a heating layer (10) that is provided with a heating surface (13) on one main surface (10a) and that heats an object to be heated; a heat-generating layer (14) that is provided inside the heating layer (10); and a lower layer (21) that is disposed on the opposite side of the heating layer (10) from the heating surface (13). The lower layer (21) is provided with a heat dissipation surface (22) on the opposite side from the heating layer (10). The thermal resistance value between the heat-generating layer (14) and the heating surface (13) is smaller than the thermal resistance value between the heat-generating layer (14) and the heat dissipation surface (22).

Description

Heater unit and electrostatic chuck

[0001] This invention relates to a heater unit and an electrostatic chuck.

[0002] When performing processes such as substrate processing and film deposition on substrates using semiconductor wafers, glass substrates, insulating substrates, etc., an electrostatic chuck is used to hold the substrate in a predetermined position (see, for example, Patent Documents 1-2).

[0003] Japanese Patent Publication No. 2019-505092, Japanese Patent Publication No. 2002-64134

[0004] Electrostatic chucks are equipped with heater units to regulate the processing temperature. However, if localized areas of high or low temperature occur, the processing temperature of the substrate becomes uneven, which may lead to problems such as deterioration of the processing state of the substrate (object being processed) and deterioration of the electrostatic chuck (processing device).

[0005] The object of this invention is to provide a heater unit and an electrostatic chuck with excellent temperature characteristics.

[0006] The present invention includes the following embodiments: [1] A heater unit comprising a heating layer having a heating surface on one main surface for heating an object to be heated, a heat-generating layer provided inside the heating layer, and a lower layer disposed on the side of the heating layer opposite to the heating surface, wherein the lower layer has a heat-dissipating surface on the side opposite to the heating layer, and the thermal resistance value between the heat-generating layer and the heating surface is smaller than the thermal resistance value between the heat-generating layer and the heat-dissipating surface. [2] The heater unit according to [1], wherein the thermal conductivity of the material of the heating layer is smaller than the thermal conductivity of the material of the lower layer. [3] The heater unit according to [1] or [2], wherein the length between the heat-generating layer and the heating surface is 50 μm or more and less than 3000 μm. [4] The heat capacity per unit area of ​​the lower layer is 0.05 to 5 J / (K・cm) ２[1] to [3] A heater unit according to any one of the following items, characterized in that the lower layer does not contain voids. [2] A heater unit according to any one of the following items, characterized in that the lower layer contains an inorganic material. [3] A heater unit according to any one of the following items, characterized in that a heat transfer adjustment layer is provided between the heating surface and the heating layer. [4] A heater unit according to any one of the following items, characterized in that the heating layer and the lower layer are joined via an adhesive layer. [5] A heater unit according to any one of the following items, characterized in that the thickness of the lower layer is 0.5 mm or more and less than 10 mm. [6] An electrostatic chuck comprising the heater unit according to any one of the following items, characterized in that the lower layer contains an adsorption electrode layer provided inside the heater unit and a base on which the heater unit is placed, wherein the heating surface is a mounting surface on which an object to be placed is placed.

[11] The electrostatic chuck according to

[10] , wherein the side surface of the electrostatic chuck is covered with a resin layer.

[0007] According to the present invention, the temperature characteristics of the heater unit and the electrostatic chuck can be improved.

[0008] This is a cross-sectional view showing an example of a heater unit. This is a cross-sectional view showing an example of an electrostatic chuck.

[0009] The present invention will be described below based on preferred embodiments. Note that the dimensional ratios of the components in the drawings may not necessarily be the same as those in reality.

[0010] <Heater Unit> Figure 1 is a cross-sectional view illustrating a heater unit according to an embodiment. The illustrated heater unit 20 includes a heating layer 10 having a heating surface 13, a heat-generating layer 14 provided inside the heating layer 10, and a lower layer 21 positioned on the side of the heating layer 10 opposite to the heating surface 13. The lower layer 21 also has a heat-dissipating surface 22 on the side opposite to the heating layer 10. The heater-mounted device 30 comprises a base 31 and the heater unit 20.

[0011] The heater unit 20 has a laminated structure in which at least a heating layer 10, a heat-generating layer 14, and a lower layer 21 are stacked between the heating surface 13 and the heat-dissipating surface 22. In this laminated structure, the stacking direction Z (vertical direction in Figure 1) of each layer is the thickness direction of each layer, as well as the height direction with respect to the base 31, and the depth direction with respect to the heating surface 13.

[0012] The heating layer 10 has main surfaces 10a and 10b on both sides in the stacking direction Z. The heating surface 13 is located on one of the main surfaces 10a of the heating layer 10. The other main surface 10b of the heating layer 10 is located on the side facing the lower layer 21.

[0013] The lower layer 21 has main surfaces 21a and 21b on both sides in the stacking direction Z. The heat dissipation surface 22 is located on one of the main surfaces 21a of the lower layer 21. The other main surface 21b of the lower layer 21 is located on the side facing the heating layer 10.

[0014] The heating layer 10 can heat an object to be heated (not shown) on the heating surface 13 by including a heat-generating layer 14 inside. The heating surface 13 may also be a mounting surface on which an object to be heated is placed. The heat-generating layer 14 is preferably an electric heating type that generates heat by receiving power from an external source, although it is not specifically shown in the figures. Examples include resistance heating, induction heating, dielectric heating, etc.

[0015] The material of the heating layer 14 is not particularly limited, but examples include conductive materials such as metals and carbon. From the viewpoint of durability, it is preferable that the heating layer 14 contains a metal such as stainless steel (SUS). The thickness of the heating layer 14 is not particularly limited, but for example, 1 to 500 μm is preferred, and 1 to 300 μm is more preferred.

[0016] Specific examples of conductive materials used in the heating layer 14 include metals such as iron (Fe), chromium (Cr), nickel (Ni), tungsten (W), molybdenum (Mo), stainless steel (SUS), aluminum (Al), zinc (Zn), titanium (Ti), tin (Sn), gold (Au), silver (Ag), copper (Cu), and platinum (Pt), and carbon such as graphite. The heating layer 14 may also be a material in which these conductive materials (metals, etc.) are mixed with other materials (ceramics, etc.).

[0017] The heat generated in the heat generating layer 14 can be conducted and diffused along the stacking direction Z to both the heating surface 13 side and the heat radiating surface 22 side. On the heat radiating surface 22 side, in order to suppress the accumulation of heat inside the heater unit 20, it is preferable to provide a cooling member capable of releasing heat to the outside. The cooling member may recover heat by flowing a refrigerant such as water or gas inside, or may release heat to the outside using a heat sink, a heat pipe, or the like. When the heat radiating surface 22 side of the heater unit 20 is placed on the base 31, a cooling member may be provided on the base 31.

[0018] In the heater unit 20 of the present embodiment, the thermal resistance value between the heat generating layer 14 and the heating surface 13 is smaller than the thermal resistance value between the heat generating layer 14 and the heat radiating surface 22. By adopting such a configuration, the amount of heat directed from the heat generating layer 14 to the heat radiating surface 22 can be suppressed compared to the amount of heat directed from the heat generating layer 14 to the heating surface 13. It is possible to suppress the loss due to the heat energy generated in the heat generating layer 14 being recovered by the cooling mechanism of the base 31, suppress local heat unevenness on the heating surface 13, and improve the temperature uniformity (heat uniformity). On the other hand, conversely, when the thermal resistance value between the heat generating layer 14 and the heating surface 13 is larger than the thermal resistance value between the heat generating layer 14 and the heat radiating surface 22, the heat energy generated in the heat generating layer 14 is likely to be recovered by the cooling mechanism of the base 31. As a result, the temperature adjustment (heating) of the heating surface 13 is suppressed, and there is a risk of local heat unevenness (decrease in heat uniformity) occurring on the heating surface 13.

[0019] When two or more layers are stacked in the heat transfer direction, the thermal resistance R of the entire stacked structure total is obtained as the sum of the thermal resistances R １ , R ２ , R ３ ,... as R total = R １ + R ２ + R ３ +... and so on. The thermal resistance R (unit: K / W) of each layer is determined from the thickness L (unit: m) in the heat transfer direction, the thermal conductivity λ (unit: W / (m·K)) of the material of each layer, and the cross-sectional area A (unit: m ２ ) by R = L / (λ·A).

[0020] In order to make the thermal resistance value between the heating layer 14 and the heating surface 13 smaller than the thermal resistance value between the heating layer 14 and the heat dissipation surface 22, this can be achieved by adjusting the thermal conductivity, thickness, etc. of each layer. When the thermal conductivity of the layer is small, the thermal resistance value of the layer becomes large, and when the thermal conductivity of the layer is large, the thermal resistance value of the layer becomes small. On the other hand, when the thickness of the layer is thin, the thermal resistance value of the layer becomes small, and when the thickness of the layer is thick, the thermal resistance value of the layer becomes large. Therefore, in the laminated structure, when the thermal conductivity of the material of the heating layer 10 constituting this is smaller than the thermal conductivity of the material of the lower layer 21 also constituting the laminated structure, by increasing the thickness of the lower layer 21, it is possible to adjust so that the thermal resistance value between the heating layer 14 in the laminated structure and the heat dissipation surface 22 of the lower layer 21 becomes large. By such adjustment, while maintaining the thermal resistance value in the lower layer 21 at a desired value, the heat capacity in the lower layer 21 can be set to a desired value preferable for heat dissipation, so that heat transfer from the heating layer 14 toward the heat dissipation surface 22 in the laminated structure can also be efficiently performed. Alternatively, instead of adjusting the thermal conductivity and thickness of each layer, between the heating layer 14 and the heating surface 13 and between the heating layer 14 and the heat dissipation surface 22, by providing a layer having a thermal function such as a heat insulation layer, a heat transfer layer, a heat diffusion layer, etc., the thermal resistance can also be adjusted. From the viewpoint of increasing the thermal resistance value, a heat insulation layer is preferable, from the viewpoint of decreasing the thermal resistance value, a heat transfer layer is preferable, and from the viewpoint of the heat uniformity of the heating surface 13 or the heat dissipation surface 22, a heat diffusion layer is preferable.

[0021] The length between the heating layer 14 and the heating surface 13 (the length along the lamination direction Z) is preferably 50 μm or more and less than 3000 μm. When the length is greater than the lower limit value, it is suitable for securing the distance between the heating layer 14 and the object to be heated, suppressing temperature unevenness, and improving heat uniformity. When the length is smaller than the upper limit value, it becomes easier to design to make the thermal resistance value between the heating layer 14 and the heating surface 13 small. The length between the heating layer 14 and the heating surface 13 is more preferably 150 to 900 μm.

[0022] The heating layer 10 may include, for example, a first region 11 between the heating layer 14 and one main surface 10a (heating surface 13), and a second region 12 between the heating layer 14 and the other main surface 10b. The first region 11 and the second region 12 can each be formed of an electrically insulating material layer. In the case where the present embodiment is an electrostatic chuck, the first region 11 and the second region 12 are each dielectric layers formed of an electrically insulating material.

[0023] Examples of the dielectric (electrically insulating material) used for the material of the heating layer 10 (for example, the first region 11 and the second region 12) include organic materials such as resins and inorganic materials such as ceramics. An inorganic material such as ceramics may be mixed with an organic material such as a resin as a filler. The resin containing the filler can improve the thermal conductivity compared to the resin itself. For example, the thermal conductivity can be adjusted according to the required temperature characteristics according to the application such as a heater unit. Regarding the layers made of these dielectrics (electrically insulating materials), the first region 11 and the second region 12 may each be a single layer, or the first region 11 or the second region 12 may be a laminate of two or more layers.

[0024] Specific examples of the resin used for the material of the heating layer 10 include polyimide, polyether ether ketone, polyphenylene sulfide, polyamideimide, liquid crystal polymer, fluoropolymer, polyester resin, polystyrene resin, etc. Examples of the fluoropolymer include polytetrafluoroethylene. Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc. These resin materials may be used alone or in combination of two or more.

[0025] Examples of the ceramics used for the material of the heating layer 10 include oxide-based ceramics and non-oxide-based ceramics. These ceramic materials may be used alone or in combination of two or more.

[0026] The oxide-based ceramics are not particularly limited, but aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ２), yttrium oxide (Y ２ O ３ ), talc (hydrated magnesium silicate, Mg ３ Si ４ O １０ (OH) １０ ), hematite (iron(III) oxide Fe ２ O ３ ), chromium(III) oxide (Cr ２ O ３ ), titanium(IV)(TiO) ２ ), magnesium oxide (MgO), silicon dioxide (SiO ２ ), calcium oxide (CaO), cerium(IV) oxide (CeO) ２ ), steatite (magnesium metasilicate, MgO・SiO ２ ), cordierite (2MgO・2Al ２ O ３ 5SiO ２ ), mullite (3Al ２ O ３ ・2SiO ２ ), ferrite (MnFe ２ O ４ (etc.), zircon (ZrSiO ４ ), barium titanate (BaTiO ３ ), lead titanate (PbTiO ３ ), forsterite (Mg ２ SiO ４ Examples include phosphorus-doped tin oxide (PTO) and antimond-doped tin oxide (ATO).

[0027] Non-oxide ceramics are not particularly limited, but examples include nitride ceramics, silicate compound ceramics, and phosphate compounds. Examples of nitride ceramics include boron nitride (BN), titanium nitride (TiN), and silicon nitride (Si ３ N ４Examples of silicate compounds include gallium nitride (GaN) and aluminum nitride (AlN). Examples of silicate compounds include zirconium oxide silicate, hafnium oxide silicate, titanium oxide silicate, lanthanum oxide silicate, yttrium oxide silicate, tantalum oxide silicate, and tantalum oxynitride silicate. Examples of phosphorus compounds include hydroxyapatite and calcium phosphate.

[0028] The thermal conductivity of the material included in the first region 11 is preferably 0.01 to 30 W / (m·K), more preferably 0.1 to 15 W / (m·K), and even more preferably 0.1 to 5 W / (m·K). By using a material having a thermal conductivity within this range, the thermal responsiveness of the heating surface 13 by the heating layer 14 is adjusted. If the thermal conductivity of the material constituting the first region 11 is less than 0.01 W / (m·K), the thermal responsiveness of the heating surface 13 by the heating layer 14 will decrease. On the other hand, if the thermal conductivity of the material included in the first region 11 exceeds 30 W / (m·K), the thermal response of the heating surface 13 by the heating layer 14 will become hypersensitive, and localized heat unevenness may occur on the heating surface 13. The thickness of the first region 11 corresponds to the length between the heating layer 14 and the heating surface 13. The thickness of the first region 11 is more preferably 20 to 2000 μm, and even more preferably 50 to 100 μm. The thermal responsiveness of the heating surface 13 by the heating layer 14 is adjusted by the thickness of the first region having such a range. If the thickness of the first region 11 is less than 20 μm, the thermal responsiveness of the heating surface 13 by the heating layer 14 becomes hypersensitive, and localized heat unevenness may occur on the heating surface 13. If the thickness of the first region 11 exceeds 2000 μm, the thermal responsiveness of the heating surface 13 by the heating layer 14 decreases.

[0029] The thermal conductivity of the material included in the second region 12 is preferably 0.01 to 30 W / (m·K), and more preferably 0.1 to 5 W / (m·K). By using a material having a thermal conductivity within this range, the influence of the heat dissipation surface 22 on the thermal response of the heating surface 13 by the heating layer 14 is reduced, and the heat dissipation performance of the heater unit 20 by the heat dissipation surface 22 is maintained. If the thermal conductivity of the material included in the second region 12 is less than 0.01 W / (m·K), the heat dissipation performance of the heater unit 20 by the heat dissipation surface 22 will decrease, and there is a risk that the heater unit 20 will not be able to be cooled. If the thermal conductivity of the material included in the second region 12 exceeds 30 W / (m·K), the influence of the heat dissipation surface 22 on the thermal response of the first region 11 or the heating surface 13 by the heating layer 14 will increase, and as a result, there is a risk that localized heat unevenness and a decrease in thermal response will occur on the heating surface 13. The thickness of the second region 12 is preferably 10 to 1000 μm, and more preferably 20 to 1000 μm. Having the second region with a thickness in this range reduces the influence of the heat dissipation surface 22 on the thermal response of the first region 11 or the heating surface 13 by the heating layer 14, and also maintains the heat dissipation performance of the heater unit 20 by the heat dissipation surface 22. If the thickness of the second region 12 is less than 20 μm, the influence of the heat dissipation surface 22 on the thermal response of the first region 11 or the heating surface 13 by the heating layer 14 becomes larger, which may result in localized heat unevenness and a decrease in thermal response on the heating surface 13. If the thickness of the first region 11 exceeds 2000 μm, the heat dissipation performance of the heater unit 20 by the heat dissipation surface 22 decreases, which may prevent the heater unit 20 from being cooled.

[0030] The lower layer 21 preferably contains an inorganic material. Inorganic materials such as stainless steel (SUS) and aluminum oxide (alumina) have high specific heat and can increase heat capacity. By ensuring the specific heat or heat capacity of the lower layer 21, the temperature of the lower layer 21 becomes less prone to fluctuations over time, and the temperature becomes more stable. Examples of inorganic materials include the various dielectrics mentioned above and metals such as stainless steel (SUS). The thermal conductivity of the material contained in the lower layer 21 is preferably 0.2 to 500 W / (m·K), and more preferably 5 to 400 W / (m·K).

[0031] In this invention, the thermal resistance between the heating layer 14 and the heating surface 13 of the heating layer 10 is smaller than the thermal resistance between the heating layer 14 and the heat dissipation surface 22 of the lower layer 21. Therefore, the lower layer 21 functions as a substantial insulating layer in the laminated structure. As a result, the influence of the heat dissipation surface 22 on the thermal response of the first region 11 or the heating surface 13 by the heating layer 14 is reduced.

[0032] The lower layer 21 may contain a dielectric (electrically insulating material) similar to that of the heating layer 10, or it may contain a conductor similar to that of the heat-generating layer 14. Examples of dielectric (electrically insulating material) used in the lower layer 21 include organic materials such as resins and inorganic materials such as ceramics. Inorganic materials such as ceramics may be mixed with organic materials such as resins as fillers. Resins containing fillers can have improved thermal conductivity compared to resins alone. Examples of conductors used in the lower layer 21 include metals such as SUS and carbon.

[0033] The thickness of the lower layer 21 is preferably 0.5 mm or more and less than 10 mm. A thickness of the lower layer 21 greater than the lower limit makes it easier to design a structure that increases the thermal resistance between the heating layer 14 and the heat dissipation surface 22. A thickness of the lower layer 21 smaller than the upper limit is suitable for suppressing the amount of material used for the lower layer 21 and ensuring heat dissipation from the heat dissipation surface 22. The thickness of the lower layer 21 is preferably 500 to 10000 μm, and more preferably 500 to 5000 μm. A thickness of the lower layer 21 within this range reduces the influence of the heat dissipation surface 22 on the thermal response of the first region 11 or the heating surface 13 by the heating layer 14, and also maintains the heat dissipation of the heater unit 20 by the heat dissipation surface 22.

[0034] The length between the heat-generating layer 14 and the heat-dissipating surface 22 (length along the stacking direction Z) can be, for example, the sum of the thickness of the second region 12 and the thickness of the lower layer 21. Furthermore, the length between the heat-generating layer 14 and the heat-dissipating surface 22 is preferably 60 to 11,000 μm, and more preferably 400 to 5,000 μm. Within this range, the influence of the heat-dissipating surface 22 on the thermal response of the first region 11 or the heating surface 13 by the heat-generating layer 14 is reduced, and the heat dissipation performance of the heater unit 20 by the heat-dissipating surface 22 is also maintained.

[0035] The lower layer 21 preferably does not contain voids. The voids may include through-holes that allow gas, rod-shaped pins, wiring, etc., to pass through locally, but it is preferable that it does not contain porous voids such as glass wool or vacuum double walls. By laminating a material having a predetermined thermal conductivity in the lamination direction Z, it is possible to ensure a predetermined thermal resistance (insulation) while also ensuring heat conduction (heat dissipation) from the heat-generating layer 14 to the heat-dissipating surface 22. By suppressing fast heat transfer while allowing slow heat transfer, temperature changes can be suppressed.

[0036] The heat capacity per unit area of ​​the lower layer 21 is 0.05 to 5 J / (K·cm²). ２ It is preferable that the heat capacity (unit J / K) is the product of the specific heat (unit J / (kg·K)) and the mass. The unit of area is cm ２ Therefore, by using a material with a high specific heat, the heat capacity can be increased. By ensuring the specific heat or heat capacity of the lower layer 21, the temperature of the lower layer 21 becomes less prone to fluctuations over time, and the temperature becomes more stable.

[0037] It is preferable that the heating layer 10 and the lower layer 21 are joined via an adhesive layer 23. The adhesive layer 23 is not particularly limited, but for example, an adhesive containing a thermosetting resin and having a heat resistance of about 100 to 250°C is preferred.

[0038] <Heater-equipped equipment, electrostatic chuck> The heater unit 20 of this embodiment can be used, for example, in an electrostatic chuck as an example of the heater-equipped equipment 30 described above. The heater-equipped equipment 30 has a heating surface 13 on which an object to be heated is placed. The heating surface 13 may have irregularities (not shown) to secure a space between it and the object to be heated. Gas may be supplied to at least some of the recesses of the irregularities for purposes such as processing and cooling. When cooling gas is supplied, the uniformity of heating and the thermal responsiveness of the heating surface 13 and the object to be heated can be further improved by adjusting conditions such as the temperature and flow rate of the cooling gas. When supplying gas to the recesses of the heating surface 13, a gas flow path (not shown) extending in the stacking direction Z from the base 31 side may be provided. The gas flow path may be surrounded by a tubular member such as ceramics as needed, and a porous member that allows gas to permeate may be placed inside the gas flow path. Furthermore, each part positioned between the base 31 and the heating surface 13, for example, the heating layer 10, the heat-generating layer 14, and the lower layer 21, may be provided with notches (not shown), such as through holes, for the purpose of accommodating a gas flow path or for any other desired purpose.

[0039] The material of the object to be heated is not particularly limited, but examples include semiconductors such as silicon (Si), glass, ceramics, and insulating materials. The object to be processed may also be a semiconductor wafer, a glass panel, etc.

[0040] The material of the base 31 is not particularly limited, but it can be formed from the oxide ceramics, non-oxide ceramics, metals and alloys such as aluminum and stainless steel mentioned above. Examples of ceramics used for the base 31 include aluminum nitride (AlN) and silicon carbide (SiC) among the non-oxide ceramics mentioned above.

[0041] Figure 2 shows an example of an electrostatic chuck. The electrostatic chuck 30A has a heater unit 20A on a base 31. Inside the heater unit 20A is an electrode layer 15 for adsorption. In the illustrated example of the heater unit 20A, the electrode layer 15 is located between the heating layer 14 and the heating surface 13. The purpose of the electrode layer 15 used in heater-equipped equipment is not particularly limited, but an example of the electrode layer 15 in the electrostatic chuck 30A is an adsorption electrode layer.

[0042] In the illustrated example, the dielectric layer (electrical insulating material layer) contained between the heat-generating layer 14 and the heating surface 13 in the heating layer 10A included in the heater unit 20A has a structure in which first regions 11A1 and 11A2 are laminated on both sides of the electrode layer 15, respectively. Of these, the first region 11A1 is located between the heating surface 13 and the electrode layer 15, and the first region 11A2 is located between the heat-generating layer 14 and the electrode layer 15.

[0043] Although not specifically shown in the figures, if two or more electrode layers 15 are laminated between the heating layer 14 and the heating surface 13, the number of dielectric layers (electrical insulating material layers) included between the heating layer 14 and the heating surface 13 can also be appropriately changed. It is preferable that dielectric layers (electrical insulating material layers) are provided between the heating layer 14, each electrode layer 15, and the heating surface 13.

[0044] The dielectric (electrically insulating material) used in the materials of the first regions 11A1, 11A2 and the second region 12 can be an organic material such as a resin or an inorganic material such as a ceramic, similar to the first region 11 and the second region 12 described above. An inorganic material such as a ceramic may be mixed with an organic material such as a resin as a filler. Regarding the layer structure of the first regions 11A1 and 11A2, the first region 11A1 and the first region 11A2 may each consist of one layer, or the first region 11A1 or the first region 11A2 may consist of two or more layers stacked together.

[0045] The thermal conductivity of the material contained in the first region 11A1 on the heating surface 13 side is preferably 0.1 to 15 W / (m·K), and more preferably 0.1 to 5 W / (m·K). The thickness of the first region 11A1 is preferably 10 to 1000 μm, and more preferably 25 to 500 μm.

[0046] The thermal conductivity of the material contained in the first region 11A2 on the heating layer 14 side is preferably 0.01 to 30 W / (m·K), and more preferably 0.1 to 5 W / (m·K). The thickness of the first region 11A2 is more preferably 10 to 1000 μm, and even more preferably 20 to 500 μm.

[0047] Although not specifically shown in the figures, the electrode layer 15 may be included in the second region 12 between the heating layer 14 and the other main surface 10b. In this case, the second region 12 of the heating layer 10 may include the region between the heating layer 14 and the electrode layer 15, and the region between the electrode layer 15 and the other main surface 10b.

[0048] The material of the electrode layer 15 is not particularly limited, but examples include conductors such as metals and carbon. From the viewpoint of durability, it is preferable that the electrode layer 15 contains a metal such as copper, nickel, or stainless steel (SUS). The thickness of the electrode layer 15 is not particularly limited, but for example, 1 to 500 μm is preferred, and 1 to 300 μm is more preferred.

[0049] Specific examples of conductive materials used in the electrode layer 15 include metals such as iron (Fe), chromium (Cr), nickel (Ni), tungsten (W), molybdenum (Mo), stainless steel (SUS), aluminum (Al), zinc (Zn), titanium (Ti), tin (Sn), gold (Au), silver (Ag), copper (Cu), and platinum (Pt), and carbon such as graphite. The electrode layer 15 may also be a material in which these conductive materials (metals, etc.) are mixed with other materials (ceramics, etc.).

[0050] The heating layer 14 and electrode layer 15 of the heater unit 20A in this embodiment are connected to a power supply via a connecting circuit (not shown). The material used for the connecting circuit can be the conductive material described above, but the resistivity of the connecting circuit connected to the heating layer 14 is preferably smaller than the resistivity of the heating layer 14, and is 2.0 × 10⁻⁶. －８ Ω・cm or more 1.0×10 －４It is more preferable that the resistivity is Ω·cm or less. This suppresses heating in the connection circuit and efficiently heats the heating layer 14, thereby improving the temperature characteristics of the heater unit 20A. For example, when the heating layer 14 or the connection circuit is made of stainless steel (SUS316) foil, the resistivity is 7.2 × 10⁻⁶. －５ It is Ω·cm.

[0051] (Method for measuring electrical resistance) The method for measuring electrical resistance is not particularly limited, but examples include the four-terminal method and the four-probe method. For example, the heating layer 14, the electrode layer 15, or the connecting circuit can be cut to a predetermined size and measured using the four-terminal method with a resistivity meter (for example, Loresta® GP manufactured by Nitto Seiko Analytech Co., Ltd.).

[0052] It is preferable that the sides of the heater unit 20A are covered with the resin layer 32. By covering the sides of the heating layer 14 and electrode layer 15 with the resin layer 32, heat insulation against the surrounding atmosphere can be ensured, and as a result, temperature control becomes easier. Furthermore, it is preferable that the sides of the base 31 are also covered with the resin layer 32. By covering the sides of the base 31 with the resin layer 32, heat insulation against the surrounding atmosphere can be ensured. In the illustrated example of the electrostatic chuck 30A, the sides of the heater unit 20A and the sides of the base 31 are covered with the same resin layer 32.

[0053] Although not specifically shown in the figures, a heat transfer adjustment layer may be provided between the heating surface 13 and the heat generating layer 14 in the heater units 20 and 20A. As shown in Figure 2, in the heater unit 20A which includes an electrode layer 15 between the heating surface 13 and the heat generating layer 14, at least one heat transfer adjustment layer may be provided between the heating surface 13 and the electrode layer 15 and / or between the electrode layer 15 and the heat generating layer 14.

[0054] Examples of heat transfer adjustment layers include anisotropic heat transfer layers that exhibit anisotropy in heat transfer in the stacking direction Z and in the planar direction perpendicular to the stacking direction Z. Among these, a heat diffusion layer is preferred in which the thermal conductivity in the planar direction is greater than the thermal conductivity in the stacking direction and which can diffuse heat in the planar direction. This improves the uniformity of heating on the heated surface 13. Examples of heat diffusion layers include metal layers (including metal sheets, metal foils, coatings, metal plating, etc.), graphite sheets, and heat conductive resin layers (including heat conductive resin sheets, heat conductive resin coatings, etc.).

[0055] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. Modifications include adding, substituting, omitting, or otherwise changing the components in each embodiment.

[0056] The present invention will be specifically described below with reference to examples.

[0057] As shown in Figure 2, a heater unit 20A was constructed by stacking a lower layer 21, a second region 12, a heating layer 14, a first region 11A2, an electrode layer 15, and a first region 11A1 on a base 31. A resin layer 32 was provided on the side surface of the electrostatic chuck 30A, which includes the base 31 and the heater unit 20A.

[0058] (Example 1) An electrostatic chuck 30A of Example 1 shown in Table 1 was fabricated. Specifically, two sheets of thermoplastic polyimide film-1 (manufactured by UBE, UPIREX® 50VT, diameter: 300 mm, thickness: 50 μm), one sheet of stainless steel foil-1 (material: SUS316, diameter: 290 mm, thickness: 30 μm), two sheets of thermoplastic polyimide film-1, one sheet of thermoplastic polyimide film-2 (manufactured by UBE, UPIREX® 25VT, diameter: 300 mm, thickness: 25 μm), and one sheet of thermoplastic polyimide film-3 (manufactured by UBE, UPIREX® 20VT, diameter: 300 mm, thickness: 20 μm) were stacked from bottom to top in the order described above, and the layers were heated and pressed together under conditions of a temperature of 300°C and a vacuum of 2.6 kPa to produce layer A. Similarly, two thermoplastic polyimide films-1, three thermoplastic polyimide films-3, one stainless steel foil-1, and two thermoplastic polyimide films-1 were laminated from bottom to top in the order described above, and then heated and pressed under the conditions described above to produce layer B. Subsequently, layer B and layer A were laminated in this order on one side of the stainless steel plate-1 (SUS316, 300 mm in diameter, 3.8 mm thick) used for the bottom layer 21, and then heated and pressed under the conditions described above to obtain an electrostatic chuck 30A. Next, thermosetting polyimide varnish (Fine Chemical Japan Co., Ltd., FC-114) was applied to the side surface of the electrostatic chuck 30A (the side surface of stainless steel plate 1, layer A, and layer B) using a spray method so that the thickness after drying and curing would be 10 μm, and the chuck was placed in a high-temperature circulating dryer set to 250°C for 24 hours to obtain an electrostatic chuck 30A with a resin layer (polyimide layer) formed on the side surface. Furthermore, layer A includes an electrode layer 15, and layer B includes a heating layer 14.

[0059] (Example 2) An electrostatic chuck 30A of Example 2 shown in Table 1 was fabricated. Except for the method of fabricating layer A, it was fabricated in the same manner as in Example 1. Specifically, one sheet of thermoplastic polyimide film-1, one sheet of graphite sheet-1 (manufactured by NeoGraf, TG-828CR, 30 μm thick), one sheet of thermoplastic polyimide film-3, one sheet of stainless steel foil-1, two sheets of thermoplastic polyimide film-1, one sheet of thermoplastic polyimide film-2, and one sheet of thermoplastic polyimide film-3 were stacked from bottom to top in the order described above, and then heated and pressed together under the conditions described above to fabricate layer A.

[0060] (Examples 3 and 4) Electrostatic chucks 30A of Examples 3 and 4 shown in Table 1 were prepared. They were prepared in the same manner as in Example 1, except that thermal conductive sheets 1, 2, and 3 were used in Example 3 instead of thermoplastic polyimide films 1, 2, and 3, and thermal conductive sheets 4, 5, and 6 were used in Example 4. For thermal conductive sheet 1 in Example 3, 100 parts by weight of polyimide, 270 parts by weight of alumina filler 1 (manufactured by Sumitomo Chemical, AA-18, average particle size 20 μm), 135 parts by weight of alumina filler 2 (manufactured by Sumitomo Chemical, AA-3, average particle size 3.5 μm), and 45 parts by weight of alumina filler 3 (manufactured by Sumitomo Chemical, AA-04, average particle size 0.5 μm) were added to 230 parts by weight of N-methylpyrrolidone (NMP), stirred, and then alumina fillers 1, 2, and 3 were dispersed using a bead mill to prepare slurry solution 1. This slurry solution-1 was applied to a sheet with a thickness of 50 μm after drying, and then placed in a constant temperature circulating dryer set to 220°C and dried for 10 minutes to produce thermal conductive sheet-1. Similarly, thermal conductive sheet-2 (thickness 25 μm) and thermal conductive sheet-3 (thickness 20 μm) were produced. Thermal conductive sheets-4, 5, and 6 in Example 4 were produced in the same manner as thermal conductive sheets-1, 2, and 3, except that slurry solution-2 was used. Slurry solution-2 was prepared by adding 100 parts by weight of polyimide, 540 parts by weight of alumina filler-1 (manufactured by Sumitomo Chemical Co., Ltd., AA-18, average particle size 20 μm), 270 parts by weight of alumina filler-2 (manufactured by Sumitomo Chemical Co., Ltd., AA-3, average particle size 3.5 μm), and 90 parts by weight of alumina filler-3 (manufactured by Sumitomo Chemical Co., Ltd., AA-04, average particle size 0.5 μm) to 450 parts by weight of N-methylpyrrolidone (NMP), stirring, and then dispersing alumina fillers-1, 2, and 3 using a bead mill.

[0061] (Examples 5 and 6) Electrostatic chucks 30A of Examples 5 and 6 shown in Table 2 were fabricated. They were fabricated in the same manner as in Example 1, except that Example 5 used a laminated thermal conductive sheet-1 as the lower layer, and Example 6 used a laminated sheet-4 as the lower layer. In Example 5, 76 sheets of thermal conductive sheet-1 were laminated and heated and pressed together under conditions of 300°C and a vacuum of 2.6 kPa to create the lower layer. In Example 6, 76 sheets of thermal conductive sheet-4 were laminated and heated and pressed together under conditions of 300°C and a vacuum of 2.6 kPa to create the lower layer.

[0062] (Example 7) An electrostatic chuck 30A of Example 7 shown in Table 2 was fabricated. It was fabricated in the same manner as in Example 1, except that the combination of thermoplastic polyimide films used for layers A and B was different. Specifically, layer A was fabricated by laminating two thermoplastic polyimide films-1, one stainless steel foil-1, and two thermoplastic polyimide films-3 in the order described above from the bottom. Layer B was fabricated by laminating four thermoplastic polyimide films-1, three thermoplastic polyimide films-3, one stainless steel foil-1, and two thermoplastic polyimide films-1 in the order described above from the bottom.

[0063] (Example 8) An electrostatic chuck 30A of Example 8 shown in Table 2 was fabricated. It was fabricated in the same manner as in Example 1, except that the combination of thermoplastic polyimide films used for layers A and B was different. Specifically, layer A was fabricated by laminating two sheets of thermoplastic polyimide film-1, one sheet of stainless steel foil-1, one sheet of thermoplastic polyimide film-2, and two sheets of thermoplastic polyimide film-3 in the order described above from the bottom. Layer B was fabricated by laminating three sheets of thermoplastic polyimide film-1, four sheets of thermoplastic polyimide film-3, one sheet of stainless steel foil-1, and two sheets of thermoplastic polyimide film-1 in the order described above from the bottom.

[0064] (Examples 9-10) Each electrostatic chuck 30A of Examples 9-10 shown in Table 3 was fabricated. Except for the different combinations of thermoplastic polyimide films used for layers A and B, the fabrication method was the same as in Example 1. Specifically, for layers A of Examples 9-10, one sheet of thermoplastic polyimide film-3, one sheet of stainless steel foil-1, two sheets of thermoplastic polyimide film-1, one sheet of thermoplastic polyimide film-2, and one sheet of thermoplastic polyimide film-3 were laminated from bottom to top in the order described above. For layer B of Example 9, two sheets of thermoplastic polyimide film-1, three sheets of thermoplastic polyimide film-3, and one sheet of stainless steel foil-1 were laminated from bottom to top in the order described above. For layer B of Example 10, two sheets of thermoplastic polyimide film-1, three sheets of thermoplastic polyimide film-3, one sheet of stainless steel foil-1, and one sheet of thermoplastic polyimide film-1 were laminated from bottom to top in the order described above.

[0065] (Examples 11 and 12) Electrostatic chucks 30A of Examples 11 and 12 shown in Table 3 were manufactured. They were manufactured in the same manner as in Example 1, except for the stainless steel plate used for the lower layer 21. In Example 11, stainless steel plate-2 (SUS316, diameter 300 mm, thickness 5.0 mm) was used. In Example 12, stainless steel plate-3 (SUS316, diameter 300 mm, thickness 8.0 mm) was used.

[0066] The thickness of each layer is shown in Tables 1 to 3. The "heating surface / electrode layer region" in Tables 1 to 3 represents the first region 11A1 in Figure 2, the "electrode layer / heating layer region" in Tables 1 to 3 represents the first region 11A2 in Figure 2, and the "heating layer / lower layer region" in Tables 1 to 3 represents the second region 12 in Figure 2.

[0067] In Tables 1 to 3, the length labeled "upper side" represents the length between the heating layer 14 and the heating surface 13, and corresponds to the sum of the thicknesses of the first regions 11A1, 11A2 and the electrode layer 15. Similarly, the thermal resistance labeled "upper side" in Tables 1 to 3 represents the thermal resistance between the heating layer 14 and the heating surface 13, and the heat capacity labeled "upper side" in Tables 1 to 3 represents the heat capacity per unit area between the heating layer 14 and the heating surface 13.

[0068] In Tables 1 to 3, the length labeled "lower side" represents the length between the heat-generating layer 14 and the heat-dissipating surface 22, and corresponds to the sum of the thicknesses of the second region 12 and the lower layer 21. Similarly, the thermal resistance labeled "lower side" in Tables 1 to 3 represents the thermal resistance between the heat-generating layer 14 and the heat-dissipating surface 22, and the heat capacity labeled "lower side" in Tables 1 to 3 represents the heat capacity per unit area between the heat-generating layer 14 and the heat-dissipating surface 22.

[0069] (Method for measuring thermal conductivity) For Examples 1 to 12, the thermal conductivity in the stacking direction Z was measured. Specifically, in each example, the upper and lower parts shown in Tables 1 to 3 were cut into cylindrical shapes (38.1 mmφ) along the stacking direction Z to prepare test specimens. The thermal conductivity (n=3) of these test specimens was measured using a thermal conductivity measuring device (NETZSCH, TCT716Lambda), and the average values ​​obtained were taken as the thermal conductivity of the upper part and the thermal conductivity of the lower part, respectively.

[0070] (Method for Calculating Thermal Resistance) For Examples 1 to 12, the thermal resistance in the stacking direction Z was calculated. Specifically, in each example, the thermal resistance of each layer was calculated using the above-mentioned thickness and thermal conductivity of the upper layer, the thickness and thermal conductivity of the lower layer, the area (the same as the area of ​​the circle with the above-mentioned diameter), and the following formula: Thermal Resistance = 1 / (Thermal Conductivity of Upper or Lower Layer × (Area / Thickness))

[0071] (Method for measuring heat capacity) For Examples 1 to 12, the heat capacity of each layer was measured. Specifically, in each example, each layer shown in Tables 1 to 3 was cut into a cylindrical shape (38.1 mmφ) along the stacking direction Z to prepare a test specimen, and the specific heat capacity (n=3) of this test specimen was measured using a thermal conductivity measuring device (NETZSCH, TCT716Lambda). The heat capacity of each layer was calculated using this specific heat capacity value, the area of ​​each layer in the electrostatic chuck 30A, and the following formula: Heat capacity = (Specific heat capacity × Mass) / Area

[0072] (Evaluation of Temperature Rise) For Examples 1 to 12, the rate of temperature rise on the heating surface 13 was evaluated. Specifically, the electrostatic chuck 30A of each example was placed on a cooling stand set to 10°C. Next, an AC power supply was connected to the heating layer 14, and the heating layer 14 was heated using a 5000W heater at 200V. Here, observation and measurement were performed using an infrared thermography camera (InfReC® R450Pro, manufactured by Avionics Japan Co., Ltd.), and the time it took for the maximum temperature of the heating surface 13 to reach 80°C was read and used to evaluate the temperature rise. These evaluations were performed under conditions of 25°C, 65% RH humidity, and atmospheric pressure. The evaluation criteria for the time it takes for the heating surface 13 to reach a maximum temperature of 80°C are as follows: less than 30 seconds is "A++ (Excellent)", 30 seconds or more but less than 60 seconds is "A+ (Very Excellent)", 60 seconds or more but less than 120 seconds is "A (Good)", 120 seconds or more but less than 240 seconds is "B (Good)", 240 seconds or more but less than 360 seconds is "C (Acceptable)", and 360 seconds or more is "D (Unacceptable)". In Tables 1 to 3, the evaluation of "temperature rise rate" is an evaluation of the rate at which the heating surface 13 heats up, and is related to the length (thickness) between the heating layer 14 and the heating surface 13, the thermal conductivity between the heating layer 14 and the heating surface 13, the thickness of the lower layer 21, the heat capacity of the lower layer 21, and the thermal conductivity of the lower layer 21. The evaluation was divided into six levels, from highest to lowest: A++ (10 points), A+ (8 points), A (6 points), B (1 point), C (0 points), and D (Fail).

[0073] (Evaluation of Temperature Decrease Performance) For Examples 1 to 12, the rate of temperature decrease on the heating surface 13 was evaluated. Specifically, the electrostatic chuck 30A of each example was placed on a cooling stand set to 10°C. Next, an AC power supply was connected to the heating layer 14, and the heating layer 14 was heated using a 5000W heater at 200V. Here, measurements were taken with an infrared thermography camera (InfReC® R450Pro, manufactured by Avionics Japan Co., Ltd.), and the AC power supply was turned off when the maximum temperature of the heating surface 13 reached 80°C. After this, the time required for the maximum temperature of the heating surface 13 to decrease to 30°C was read and used to evaluate the temperature decrease performance. These evaluations were performed under conditions of 25°C, 65% RH humidity, and atmospheric pressure. The evaluation criteria for the time it takes for the heating surface 13 to reach a maximum temperature of 30°C is as follows: less than 30 seconds is rated "A++ (Excellent)", 30 seconds or more but less than 60 seconds is rated "A+ (Very Excellent)", 60 seconds or more but less than 120 seconds is rated "A (Good)", 120 seconds or more but less than 240 seconds is rated "B (Good)", 240 seconds or more but less than 360 seconds is rated "C (Acceptable)", and 360 seconds or more is rated "D (Unacceptable)". In Tables 1 to 3, the "Temperature Decrease Performance" evaluation is an evaluation of the rate at which the temperature of the heating surface 13 decreases, and is related to the thickness of the lower layer 21, the heat capacity of the lower layer 21, and the thermal conductivity of the lower layer 21. The judgment was made in six stages, from highest to lowest evaluation: A++ (10 points), A+ (8 points), A (6 points), B (1 point), C (0 points), and D (Unacceptable).

[0074] (Evaluation of Heat Uniformity) For Examples 1 to 12, the heat uniformity of the heating surface 13 was evaluated. Specifically, the electrostatic chuck 30A of each example was placed on a cooling stand set to 10°C. Next, an AC power supply was connected to the heating layer 14, and the heating layer 14 was heated for 1 minute at 200V using a 5000W heater. Here, observation and measurement were performed using an infrared thermography camera (InfReC® R450Pro, manufactured by Avionics Japan Co., Ltd.), and the temperature difference between the highest and lowest temperatures on the heating surface 13 was read and used to evaluate the heat uniformity. These evaluations were performed under conditions of 25°C, 65% RH humidity, and atmospheric pressure. The evaluation criteria were as follows: "A++ (Excellent)" if the difference between the highest and lowest temperatures of the heating surface 13 was less than 1.0°C, "A+ (Very Excellent)" if it was 1.0°C or more but less than 10.0°C, "A (Good)" if it was 10.0°C or more but less than 20.0°C, "B (Good)" if it was 20.0°C or more but less than 30.0°C, "C (Acceptable)" if it was 30.0°C or more but less than 40.0°C, and "D (Unacceptable)" if it was 40.0°C or more. However, if the difference between the highest and lowest temperatures was equal (the overall temperature difference was below the detection limit), the difference was considered to be 0°C, and the difference was not considered to be negative. The evaluation was divided into six levels, from highest to lowest: A++ (10 points), A+ (8 points), A (6 points), B (1 point), C (0 points), and D (Unacceptable).

[0075] (Evaluation of Adsorption Force) For Examples 1 to 12, the adsorption force on the heated surface 13 was evaluated. Specifically, an aluminum plate (outer diameter 300 mm x thickness 1.0 mm) was placed on the heated surface 13 of each electrostatic chuck 30A so as to be in the same position as the heated surface 13 when viewed from the stacking direction Z. Then, the probe of an LCR meter (HIOKI IM3536) was connected to the electrode layer 15 and the aluminum plate with cables. Subsequently, the capacitance was measured five times at 2-second intervals under a frequency of 1 kHz. This measurement was repeated five times, and the average value was used to evaluate the adsorption force (average capacitance). These evaluations were performed under conditions of a temperature of 25°C and a humidity of 65% RH. The evaluation criteria were as follows: an average capacitance (in nF) of 20 or more was rated "A++ (Excellent)", 10 or more but less than 20 was rated "A+ (Good)", 7.5 or more but less than 10 was rated "A (Good)", 5 or more but less than 7.5 was rated "B (Good)", less than 5 was rated "C (Acceptable)", and measurement was not possible was rated "D (Unacceptable)". The judgment was made in six stages, from highest to lowest evaluation: A++ (10 points), A+ (8 points), A (6 points), B (1 point), C (0 points), and D (Unacceptable).

[0076] In Tables 1-3, the overall evaluation was calculated by summing the scores for the four items: "temperature rise," "temperature fall," "uniform heating," and "adsorption capacity," assuming that there were no "fail" ratings in any of the four items.

[0077]

[0078]

[0079]

[0080] Based on the evaluation results shown in Tables 1 to 3, the heater units 20A of Examples 1 to 12 had no failures (evaluation D) in any of the following items: the rate of temperature rise of the heating surface 13, the rate of temperature decrease of the heating surface 13, the uniformity of the heating surface 13, and the adsorption performance of the electrostatic chuck 30A, indicating that they had sufficient performance.

[0081] According to the present invention, the temperature characteristics of the heater unit and the electrostatic chuck can be improved.

[0082] 10, 10A...heating layer, 10a...one main surface, 10b...the other main surface, 11...first region, 12...second region, 13...heating surface, 14...heating layer, 15...electrode layer, 20, 20A...heater unit, 21...lower layer, 22...heat dissipation surface, 23...adhesive layer, 30...heater mounted equipment, 30A...electrostatic chuck, 31...base, 32...resin layer.

Claims

1. A heater unit comprising: a heating layer having a heating surface on one main surface for heating an object to be heated; a heat-generating layer provided inside the heating layer; and a lower layer disposed on the side of the heating layer opposite to the heating surface, wherein the lower layer has a heat-dissipating surface on the side opposite to the heating layer, and the thermal resistance value between the heat-generating layer and the heating surface is smaller than the thermal resistance value between the heat-generating layer and the heat-dissipating surface.

2. The heater unit according to claim 1, characterized in that the thermal conductivity of the material in the heating layer is less than the thermal conductivity of the material in the lower layer.

3. The heater unit according to claim 1, characterized in that the length between the heating layer and the heating surface is 50 μm or more and less than 3000 μm.

4. The heat capacity per unit area of ​​the lower layer is 0.05 to 5 J / (K·cm²). ２ The heater unit according to claim 1, characterized in that it is the same as the one described in claim 1.

5. The heater unit according to claim 4, characterized in that the lower layer does not contain voids.

6. The heater unit according to claim 1, characterized in that the lower layer includes an inorganic material.

7. The heater unit according to claim 1, characterized in that a heat transfer adjustment layer is provided between the heating surface and the heating layer.

8. The heater unit according to claim 1, characterized in that the heating layer and the lower layer are joined via an adhesive layer.

9. The heater unit according to claim 1, characterized in that the thickness of the lower layer is 0.5 mm or more and less than 10 mm.

10. An electrostatic chuck comprising a heater unit according to any one of claims 1 to 9, an adsorption electrode layer provided inside the heater unit, and a base on which the heater unit is placed, wherein the heating surface is a mounting surface on which an object to be mounted is placed.

11. The electrostatic chuck according to claim 10, wherein the side surface of the electrostatic chuck is covered with a resin layer.

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