Electrostatic chuck apparatus

Abstract

Disclosed is an electrostatic chuck apparatus which is configured of: an electrostatic chuck section; an annular focus ring section provided to surround the electrostatic chuck section; and a cooling base section which cools the electrostatic chuck section and the focus ring section. The focus ring section is provided with an annular focus ring, an annular heat conducting sheet, an annular ceramic ring, a nonmagnetic heater, and an electrode section that supplies power to the heater.

Claims

1. An electrostatic chuck apparatus comprising: an electrostatic chuck section, one main surface of which is a placing surface for placing a specimen, and which is equipped with an internal electrode for electrostatic adsorption; an annular focus ring section which is provided so as to surround the electrostatic chuck section; a cooling base section which is provided on the other main surface side of the electrode chuck section to cool the electrostatic chuck section and the focus ring section, the focus ring section includes an annular focus ring, an annular ceramic plate which is adhered to a lower surface of the focus ring, a sheet-like heater portion which is provided between the annular ceramic plate and the cooling base section, and is formed from a non-magnetic metal, and an electrode section which supplies electricity to a heater section, the heater section is fixed to the annular ceramic plate by a first insulating adhesive layer, is fixed to the cooling base section by a second insulating adhesive layer, and is insulated by the first insulating adhesive layer and the second insulating adhesive layer, and a cooling medium gas is circulated between the annular focus ring section and the annular ceramic plate.

2. The electrostatic chuck apparatus according to claim 1, wherein the annular ceramic plate is constituted by a plurality of annular ceramic pieces which is formed by dividing the annular ceramic plate in a radial direction.

3. The electrostatic chuck apparatus according to claim 1, wherein an insulating ceramic membrane or an insulating organic film is provided between the cooling base section and the heater section.

4. The electrostatic chuck apparatus according to claim 1, wherein temperature measuring means is provided in the focus ring section.

5. The electrostatic chuck apparatus according to claim 1, wherein the heater section has an electrical conductivity of 0.5×10.sup.6 S/m or more and 20×10.sup.6 S/m or less, and a coefficient of thermal expansion of 0.1×10.sup.−6/K or more and 100×10.sup.−6/K or less.

6. The electrostatic chuck apparatus according to claim 1, wherein the heater section is formed from titanium or titanium alloy.

7. The electrostatic chuck apparatus according to claim 1, wherein the ceramic plate has insulating properties and has thermal conductivity of 1 W/mK or more.

8. The electrostatic chuck apparatus according to claim 1, wherein the second insulating adhesive layer contains a filler.

9. The electrostatic chuck apparatus according to claim 1, wherein the coefficient of heat transfer between the heater section and the cooling base section is 400 W/m.sup.2K or more and 10,000 W/m.sup.2K or less.

10. An electrostatic chuck apparatus comprising: an electrostatic chuck section, one main surface of which is a placing surface for electrostatic adsorption of a plate-like specimen, and which is equipped with an internal electrode for electrostatic adsorption; an annular focus ring section which is provided so as to surround the electrostatic chuck section; and a cooling base section which is provided on the other main surface side of the electrode chuck section to cool the electrostatic chuck section and the focus ring section, wherein the focus ring section includes a focus ring, a ceramic plate which is provided between the focus ring and the cooling base section, a heater section which is provided between the ceramic plate and the cooling base section and is formed from a non-magnetic body, and an electrode section which supplies electricity to the heater section; the cooling base section is divided into two parts: one part being a first cooling base section which supports the electrostatic chuck section, and cools the electrostatic chuck section by a flow path through which a cooling medium is circulated, and the other part being a second cooling base section which is present outside of the first cooling base section for supporting the annular focus ring section, and cools the annular focus ring by another flow path through which a cooling medium is circulated.

11. The electrostatic chuck apparatus according to claim 10, wherein the ceramic plate is constituted by a plurality of annular ceramic pieces which is formed by dividing the annular ceramic plate in a radial direction.

12. The electrostatic chuck apparatus according to claim 10, wherein an insulating ceramic membrane or an insulating organic film is provided between the second cooling base section and the heater section.

13. The electrostatic chuck apparatus according to claim 10, wherein temperature measuring means is provided in the focus ring section.

14. The electrostatic chuck apparatus according to claim 10, wherein the heater section has an electrical conductivity of 0.5×10.sup.6 S/m or more and 20×10.sup.6 S/m or less, and a coefficient of thermal expansion of 0.1×10.sup.−6/K or more and 100×10.sup.−6/K or less.

15. The electrostatic chuck apparatus according to claim 10, wherein the heater section is formed from titanium or titanium alloy.

16. The electrostatic chuck apparatus according to claim 10, wherein the ceramic plate has insulating properties and has thermal conductivity of 1 W/mK or more.

17. The electrostatic chuck apparatus according to claim 10, wherein the coefficient of heat transfer between the heater section and the cooling base section is 400 W/m.sup.2K or more and 10,000 W/m.sup.2K or less.

18. The electrostatic chuck apparatus according to claim 10, wherein the heater section is fixed to the ceramic plate by a first insulating adhesive layer, is fixed to the cooling base section by a second insulating adhesive layer, and is insulated by the first insulating adhesive layer and the second insulating adhesive layer.

19. The electrostatic chuck apparatus according to claim 18, wherein the second insulating adhesive layer contains a filler.

20. The electrostatic chuck apparatus according to claim 10, wherein a cooling medium gas is circulated between the annular focus ring section and the annular ceramic plate.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a cross-sectional view that shows an electronic chuck apparatus of an embodiment of the present invention.

(2) FIG. 2 is a plan view that shows an example of a shape of a ceramic ring of the electronic chuck apparatus of an embodiment of the present invention.

(3) FIG. 3 is a plan view that shows another example of the shape of the ceramic ring of the electrostatic chuck apparatus of an embodiment of the present invention.

(4) FIG. 4 is a plan view that shows still another embodiment of the shape of the ceramic ring of the electrostatic chuck apparatus of an embodiment of the present invention.

(5) FIG. 5 is a cross-sectional view that shows a modified example of the electrostatic chuck apparatus of an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

(6) An embodiment of an electrostatic chuck apparatus of the present invention will be described.

(7) In addition, in the respective embodiments mentioned below will be specifically described in order to better understand the spirit of the present invention, but the present invention is not limited, unless otherwise particularly specified.

(8) FIG. 1 is a cross-sectional view that shows an electrostatic chuck apparatus of an embodiment of the present invention, and the electrostatic chuck apparatus 1 is constituted by an electrostatic chuck section 2, an annular focus ring section 3 provided so as to surround the electrostatic chuck section 2, and a cooling base section 4 which cools the electrostatic chuck section 2 and the focus ring section 3.

(9) The electrostatic chuck section 2 includes a circular dielectric layer 11 in which an upper surface (one major surface) thereof is a placing surface for placing a plate-like specimen W such as a semiconductor wafer, a circular insulating layer 12 which is oppositely arranged on a lower surface (the other major surface) side of the dielectric layer 11 and has the same diameter as that of the dielectric layer 11, an electrostatic adsorption internal electrode 13 of an annular shape which is interposed between the dielectric layer 11 and the insulating layer 12 and has a diameter smaller than those of the dielectric layer 11 and the insulating layer 12, an annular insulating material layer 14 provided on the outer periphery side of the electrostatic adsorption internal electrode 13 so as to surround the same, a power supplying terminal 15 which is connected to a lower surface center portion of the electrostatic adsorption internal electrode 13 to apply the direct current voltage, and a cylindrical insulator 16 which is isolated from the outside by covering the periphery of the power supplying terminal 15.

(10) Preferably, both of the dielectric layer 11 and the insulating layer 12 are ceramics having the heat resistance. As the ceramics, ceramics formed of one kind selected from aluminum nitride (AlN), aluminum oxide (Al2O3), silicon nitride (Si3N4), zirconium oxide (ZrO2), sialon, boron nitride (BN), silicon carbide (SiC), or composite ceramics including two kinds or more are preferably used.

(11) Particularly, in view of the fact that upper surface 11a becomes an electrostatic adsorption surface, the dielectric layer 11 is made from a material which has a particularly high dielectric constant, and does not become impurities with respect to the electrostatically adsorbed plate-like specimen W. For example, silicon carbide-aluminum oxide compound sintered compact is preferably used which contains silicon carbide of 4 weight % or more and 20 weight % or less and the remainders of aluminum oxide.

(12) As the electrostatic adsorption internal electrode 13, a flat plate ceramic having a thickness of about 10 μm to 50 μm and conductivity is used. A volume resistivity value of the electrostatic adsorption internal electrode 13 under the working temperature of the electrostatic chuck apparatus 1 is preferably equal to or less than 1.0×106 Ω.Math.cm, and more preferably, is equal to or less than 1.0×104 Ω.Math.cm.

(13) As the conductive ceramics constituting the electrostatic adsorption internal electrode 13, silicon carbide (SiC)—aluminum oxide (Al2O3) compound sintered compact, tantalum nitride (TaN)—tantalum oxide (Al2O3) compound sintered compact, tantalum carbide (TaC)—aluminum oxide (Al2O3) compound sintered compact, molybdenum carbide (Mo2C)—aluminum oxide (Al2O3) compound sintered compound or the like are adopted.

(14) The insulating material layer 14 joins the dielectric layer 11 and the insulating layer 12 to integrate them, and protects the electrostatic adsorption internal electrode 13 from the plasma. As a material constituting the insulating material layer 14, an insulating material having the same main component as those of the dielectric layer 11 and the insulating layer 12 is preferably used. For example, when the dielectric layer 11 and the insulating layer 12 are formed by silicon carbide-aluminum oxide compound sintered compact, aluminum oxide (Al2O3) is preferably used.

(15) The focus ring section 3 includes a focus ring 21 formed from an annular plate material which has an inner diameter slightly larger than a diameter of the electrostatic chuck section 2 and an outer diameter slightly larger than an outer diameter of the cooling base section 4; an annular thermal conducting sheet 22 which is adhered to a lower surface of the focus ring 21 and has an inner diameter identical to the inner diameter of the focus ring 21 and an outer diameter smaller than the outer diameter of the focus ring 21; an annular ceramic ring (a ceramic plate) 23 which is adhered to a lower surface of the thermal conducting sheet 22 and has an inner diameter and an outer diameter substantially identical to those of the thermal conducting sheet 22; a heater 25 which is adhered to the lower surface of the ceramic ring 23 via a sheet-like (first) insulating adhesive layer 24 and is formed from a non-magnetic body; a heater electrode 26 which is bonded to the lower surface of the heater 25 to supply electricity to the heater 25; and a cylindrical heater insulator 27 which is isolated from the outside by covering the periphery of the heater electrode 26.

(16) The focus ring section 3 is bonded and fixed to the cooling base section 4 via a (second) insulating adhesive layer 28.

(17) The focus ring 21 is controlled so as to be the same temperature as that of the plate-like specimen W by a processing step such as a plasma etching. As the material thereof, for example, in a case of being used in oxide film etching, polycrystalline silicon, silicon carbide or the like are suitably used.

(18) The thermal conducting sheet 22 transmits heat from the ceramic ring 23 subjected to the temperature control to the focus ring 21, and a sheet-like material having high thermal conductivity or the like is suitably used.

(19) In order that the thermal conducting sheet 22 continues to favorably hold the thermal conduction between the focus ring 21 and the ceramic ring 23, it is necessary that the coefficient of heat transfer in the case of interposing the thermal conducting sheet 22 between the focus ring 21 and the ceramic ring 23 be equal to or greater than 500 W/m2K.

(20) Herein, in a case where the coefficient of heat transfer is less than 500 W/m2K, an influence of the temperature rising of the focus ring 21 is increased when high frequency is applied, it is impossible to control the temperature of the focus ring 21 due to the heater 25 and the cooling base section 4, and the case is not preferable.

(21) The ceramic ring 23 is, for example, an annular ceramic plate having insulating properties formed from aluminum oxide (Al2O3), quartz or the like, and the thermal conductivity thereof is equal to or greater than 1 W/mK.

(22) When the thermal conductivity is less than 1 W/mK, heat from the heater 25 cannot be rapidly transmitted to the focus ring 21 via the thermal conducting sheet 22, a temperature difference is generated between the surface temperature of the focus ring 21 and the surface temperature of the electrostatic chuck section 2, and thus, the surface temperature of the plate-like specimen W placed on the electrostatic chuck section 2 is not stable. As a consequence, it is impossible to equalize the in-plane characteristics of the plate-like specimen W subjected to various processes, and the case is not preferable.

(23) In addition to the annular shape shown in FIG. 2, the ceramic ring 23 may be an arc-shaped ceramic piece in which the annular ceramic plate is divided into a plurality of parts in a circumferential direction, for example, the arc-shaped ceramic pieces 23a to 23d shown in FIG. 3 may be combined with each other in an annular shape, an annular ceramic pieces may be used in which the annular ceramic piece is divided into a plurality of parts in a radial direction, for example, annular ceramic pieces 23e to 23f shown in FIG. 4 may be concentrically combined with each other.

(24) As the insulating adhesive layers 24 and 28, the adhesive having the heat resistance in the temperature range of −20° C. to 150° C. is suitably used. For example, silicon resin, silicon resin containing a filler such as alumina and aluminum nitride, acryl resin, epoxy resin or the like are preferable. Particularly, in the case of using the oxygen-based plasma, silicon resin having an excellent plasma resistance with respect to the oxygen-based plasma is preferable.

(25) The insulating adhesive layers 24 and 28 may be the same material and may be materials different from each other. Furthermore, the shapes thereof may be the sheet-like adhesive, and a liquid adhesive or the like may be adopted which is cured by heat and an ultraviolet irradiation. In brief, the insulating adhesive layers may be suitably selected and used according to the material composition and the shape of a member to be bonded.

(26) Specifically, for example, the insulating adhesive layer 24 is preferably the sheet-like epoxy resin, and the insulating adhesive layer 28 is preferably the silicon resin.

(27) The heater 25 controls the temperature of the focus ring 21 to the same temperature as that of the plate-like specimen W, by heating the temperature of the focus ring 21 to a predetermined temperature at a certain temperature rising rate via the ceramic ring 23. In order to sufficiently demonstrate the function as the heater 25, electrical conductivity thereof is preferably 0.5×106 S/m or more and 20×106 S/m or less, and, more preferably, 0.9×106 S/m or more and 5×106 S/m or less.

(28) Furthermore, even in a case where the heating and the cooling are repeated, it is necessary that the heater 25 does not peel off from the ceramic ring 23 and the cooling base section 4. Thus, coefficient of thermal expansion thereof is preferably 0.1×10-6/K or more and 100×10-6/K or less, more preferably, 0.1×10-6/K or more and 20×10-6/K or less, and, still more preferably, 4×10-6/K or more and 10×10-6/K or less.

(29) Since the heater itself avoids the self-heating by the high frequency (RF) when the high frequency (RF) is applied in a case of being applied to a plasma processing apparatus using the high frequency (RF), the heater 25 needs to be a non-magnetic material, and a conductor formed from the sheet-like non-magnetic material is suitably used. As such a conductor, for example, a titanium foil, titanium alloy foil or the like are adopted.

(30) The thickness of the heater 25 is, preferably, equal to or less than 200 μm, and, more preferably, equal to or less than 120 μm.

(31) By making the thickness of the heater 25 equal to or less than 200 μm, when bonding and fixing the heater 25 to the cooling base section 4 via the insulating adhesive layer 28, the thickness of the insulating adhesive layer 28 from the ceramic ring 23 to the cooling base section 4 can be reduced, and thus, it is possible to reduce an area to be exposed to the plasma in an exposed cross-section of the insulating adhesive layer 28. As a consequence, it is possible to reduce the damage to the insulating adhesive layer 28 due to the plasma when irradiating the plasma.

(32) The heater 25 is bonded to the lower surface of the ceramic ring 23 via the insulating adhesive layer 24, and is bonded and fixed to the cooling base section 4 via the insulating adhesive layer 28. In addition, the heater 25 is held while favorably keeping an interval between them, without coming into contact with the cooling base section 4, and the insulating adhesive is filled in the gap, and thus, the insulating properties between the ceramic ring 23 and the cooling base section 4 can be favorably maintained, whereby it is possible to reduce the thermal stress of the heater 25 by the insulating adhesive layers 24 and 28.

(33) The cooling base section 4 is provided on the lower sides of the electrostatic chuck section 2 and the focus ring section 3 to control the temperatures of the electrostatic chuck section 2 and the focus ring section 3 to desired temperatures, combines a high frequency generating electrode, and is formed by a metal having good thermal conductivity such as aluminum. An inner portion thereof is formed with a flow path 31 through which a cooling medium such as water and organic solvent is circulated. The cooling base section 4 is able to maintain the temperature of the plate-like specimen W placed on the upper surface 11a of the dielectric layer 11 to a desired temperature.

(34) The heater electrode 26 and the heater insulator 27 are fixed to a through hole 32 formed on the underside of the heater 25 of the cooling base section 4, the power supplying terminal 15 and the insulator 16 are fixed to a through hole 33 formed in the center portion of the cooling base section 4, and an optical thermometer (temperature measuring means) 35 for directly measuring the temperature of the ceramic ring 23 by receiving light emitted from the ceramic ring 23 is fixed to a through hole 34 of an opposite side of the though hole 32 to the center axis of the cooling base section 4.

(35) The optical thermometer 35 may have a configuration that directly measures the temperature of the heater 25, and may have a configuration that directly measures the temperature of the focus ring 21.

(36) A temperature controller 36 and a heater power source 37 are connected to the optical thermometer 35 in series, and the heater power source 37 is connected to the heater electrode 26.

(37) Herein, if one wants to know the temperature of the ceramic ring 23, when the optical thermometer 35 detects light emitted from the ceramic ring 23, it is possible to directly know the temperature of the ceramic ring 23 from a wavelength band of the light.

(38) Herein, the optical thermometer 35 converts the value of the temperature corresponding to the light into an electrical signal and outputs the signal to the temperature controller 36. In the temperature controller 36, the control signal, which controls the electrical power applied to the heater 25 based on the electrical signal from the optical thermometer 35, is output to the heater power source 37. In the heater power source 37, the controlled electrical power is output to the heater 25 based on the control signal which is output from the temperature controller 36, and an amount of heat emitted from the heater 25 is controlled.

(39) Thus, the focus ring 21 can be heated up to a predetermined temperature at a certain temperature rising rate via the ceramic ring 23 by using the heater 25, and the temperature can be held. Furthermore, in a case where the temperature of the focus ring 21 is increased by the plasma, the temperature rising of the focus ring section 3 is suppressed by adjusting the output of the heater 25, and thus, the temperature of the focus ring section 3 can be constantly maintained.

(40) An interval between the cooling base section 4 and the ceramic ring 23 is a sum of thickness the insulating adhesive layer 24, the heater 25 and the insulating adhesive layer 28, that is, 100 μm to 500 μm.

(41) In this manner, by interposing the insulating adhesive layer 24, the heater 25 and the insulating adhesive layer 28 in a layer shape, the interval between the cooling base section 4 and the ceramic ring 23 can be extremely narrowed, and thus, the temperature of the focus ring 21 can be accurately controlled to a predetermined temperature via the ceramic ring 23.

(42) The coefficient of heat transfer between the cooling base section 4 and the heater 25 is preferably 400 W/m2K or more and 10,000 W/m2K or less, and more preferably, 1,000 W/m2K or more and 4,000 W/m2K or less. By setting the coefficient of heat transfer between the cooling base section 4 and the heater 25 to the range mentioned above, it is possible to substantially match the temperature rising rate and the cooling rate of the ceramic ring 23 with the temperature rising rate and the cooling rate of the electrostatic chuck section 2 when causing a predetermined current to flow in the heater 25. Thus, it is possible to substantially match the temperature rising rate and the cooling rate of the focus ring 21 with the temperature rising rate and the cooling rate of the electrostatic chuck section 2.

(43) From the above, the temperature of the focus ring 21 can be adjusted by using the heater 26, and the temperature of the focus ring 21 being processing can be constantly maintained. Thus, the temperature of the outer periphery portion of the plate-like specimen W such as the silicon wafer can be stabilized, and thus, the etching characteristics in the plane of the plate-like specimen W can be equalized.

(44) Furthermore, since the surface temperature of the focus ring 21 can be accurately adjusted, it is possible to alleviate the temperature difference between the surface temperature of the focus ring 21 and the surface temperature of the plate-like specimen W placed on the electrostatic chuck section 2, and thus, it is possible to prevent the deposits from being deposited on the focus ring 21.

(45) As described above, according to the electrostatic chuck apparatus of the present embodiment, since the heater 25 is provided between the ceramic ring 23 and the cooling base section 4, it is possible to alleviate the stress to the ceramic ring 23 when the heater 25 generates heat. Furthermore, since a configuration is used in which the heater 25 is not embedded in ceramics, the manufacturing step can be simplified, and the manufacturing cost can also be reduced.

(46) Since the heater 25 is the non-magnetic body, even in a case where the high frequency is applied to the heater 25, there is no fear of generation of heat due to the high frequency. Thus, even when the high frequency is applied, the self generation of heat can be avoided.

(47) Since the heater 25 is fixed to the ceramic ring 23 and the cooling base section 4 via the insulating adhesive layers 24 and 28, by interposing the insulating adhesive layers 24 and 28 between the ceramic ring 23 and the cooling base section 4, the thermal stress due to the thermal expansion of the heater 25 can be alleviated, and the thermal stress due to the thermal expansion of the ceramic ring 23 and the cooling base section 4 can also be alleviated.

(48) In addition, since the optical thermometer 35 for directly measuring the temperature of the ceramic ring 23 is fixed to the through hole 34 of the cooling base section 4, it is possible to prevent the heat of the ceramic ring 23 escaping to the cooling base section 4 via the optical thermometer 35.

(49) Furthermore, since the temperature of the ceramic ring 23 is directly measured by the optical thermometer 35, there is no fear of an influence of the generation of heat from the heater 25, and the temperature of the ceramic ring 23 itself can be accurately measured.

(50) In addition, in order to increase insulating properties between the cooling base section 4 and the heater 25, an insulating ceramic membrane or an insulating organic film may be provided between the cooling base section 4 and the heater 25.

(51) Furthermore, the thermal conducting sheet 22 is provided between the focus ring 21 and the ceramic ring 23, but a configuration may be adopted in which helium gas or the like flows, instead of the thermal conducting sheet 22.

(52) Furthermore, as a target that directly measures the temperature using the optical thermometer 35, the temperature of the focus ring 21 or the thermal conducting sheet 22 may be directly measured, without being limited to the ceramic ring 23.

(53) FIG. 5 is a cross-sectional view that shows a modified example of the electrostatic chuck apparatus of the present embodiment. The electrostatic chuck apparatus 41 is different from the electrostatic chuck apparatus 1 in that the cooling base section is divided into a disk-shaped thick cooling base section 42 for cooling the electrostatic chuck section 2 and an annular thick cooling base section 43 provided so as to surround the cooling base section 42 for cooling the focus ring section 3. In other respects, the electrostatic chuck apparatus 41 is exactly the same as the electrostatic chuck apparatus 1 mentioned above.

(54) According to the electrostatic chuck apparatus 41, since the thick cooling base section 42 for cooling the electrostatic chuck section 2 and the cooling base section 43 for cooling the focus ring section 3 are provided, the electrostatic chuck section 2 can be cooled by the cooling base section 42, and the focus ring section 3 can be cooled by the cooling base section 43, respectively and independently, whereby it is possible to enhance the temperature controllability of each of the electrostatic chuck section 2 and the focus ring section 3.

REFERENCE SIGNS LIST

(55) 1: electrostatic chuck apparatus

(56) 2: electrostatic chuck section

(57) 3: focus ring section

(58) 4: cooling base section

(59) 11: dielectric layer

(60) 11a: upper surface

(61) 12: insulating layer

(62) 13: electrostatic adsorption internal electrode

(63) 14: insulating material layer

(64) 15: power supplying terminal

(65) 16: insulator

(66) 21: focus ring

(67) 22: thermal conducting sheet

(68) 23: ceramic ring (ceramic plate)

(69) 24: (first) insulating adhesive layer

(70) 25: heater

(71) 26: heater electrode

(72) 27: heater insulator

(73) 28: (second) insulating adhesive layer

(74) 31: flow path

(75) 32 to 34: through hole

(76) 35: optical thermometer (temperature measuring means)

(77) 36: temperature controller

(78) 37: heater power source

(79) 41: electrostatic chuck apparatus

(80) 42, 43: cooling base section