Wafer placement table

Abstract

A wafer placement table 10 comprises a ceramic substrate 20 and a heat transfer liquid flow path 50. The ceramic substrate 20 has, on the upper surface thereof, a support surface 22 for supporting a wafer W, and recesses 25 recessed from the support surface 22. The heat transfer liquid flow path 50 is provided at least inside the ceramic substrate 20 and serves as a flow path for the heat transfer liquid between the outside of the wafer placement table 10 and the inner side of the recesses 25.

Description

Wafer mounting table

[0001] The present invention relates to a wafer stage.

[0002] Conventionally, there are known mounting tables used in semiconductor manufacturing equipment and the like, on whose upper surface a wafer is mounted. For example, a mounting table described in Patent Document 1 is provided with a backside gas supply pipe for supplying a heat transfer gas (backside gas) between the back surface of the mounted wafer and the mounting surface of the mounting table. The heat transfer gas promotes heat exchange between the mounting table and the wafer. It is described that helium gas or the like is used as the heat transfer gas.

[0003] Patent No. 6203476

[0004] In such a wafer stage, there has been a demand for increasing the thermal conductivity between the wafer and the wafer stage.

[0005] The present invention has been made to solve the above problems, and a main object of the present invention is to provide a wafer stage that can increase the thermal conductivity between the stage and the wafer.

[0006] In order to achieve the above-mentioned main object, the present invention employs the following means.

[0007] [1] The wafer mounting table of the present invention comprises: a ceramic base having, on its upper surface, a support surface for supporting a wafer and a recess recessed from the support surface; and a heat transfer liquid flow path provided at least inside the ceramic base, which serves as a flow path for a heat transfer liquid between the outside and the inside of the recess.

[0008] In this wafer mounting table, a heat transfer liquid can be supplied to the inside of the recess in the upper surface of the ceramic base through the heat transfer liquid flow path. That is, a heat transfer liquid, rather than a heat transfer gas, can be supplied to the space between the wafer placed on the support surface and the inner peripheral surface of the recess. Because liquids generally have higher thermal conductivity than gases, the wafer mounting table having such a recess and heat transfer liquid flow path can increase the thermal conductivity between the wafer and the wafer mounting table.

[0009] [2] In the wafer mounting table described above (the mounting table described in [1] above), the recess may have a reference surface located lower than the support surface and a groove formed in the reference surface, and the groove may be arranged from an opening of the heat transfer liquid flow path to the recess toward the periphery of the opening. In this way, the heat transfer liquid supplied from the opening to the recess through the heat transfer liquid flow path is guided by the groove and easily flows around the opening. This allows the heat transfer liquid to be efficiently distributed inside the recess. In this case, the groove may be provided in plurality.

[0010] [3] In the wafer stage (the stage described in [1] or [2]), a plurality of the heat transfer liquid channels may be provided, each having an opening to the recess. In this case, one or more of the plurality of heat transfer liquid channels can be used as an inlet of the heat transfer liquid channel, and the remaining can be used as an outlet. This allows the heat transfer liquid to be efficiently supplied to and discharged from the recess.

[0011] [4] In the wafer mounting table described in [3] above, the recess may have a reference surface that is lower than the support surface and a groove formed in the reference surface, and the groove may be provided to connect two or more of the openings. In this case, the groove may be provided to connect an opening that serves as an inlet and an opening that serves as an outlet for the heat transfer liquid into the recess, among the plurality of openings.

[0012] [5] The wafer stage (the stage according to any one of [1] to [4] above) may further include the heat transfer liquid placed in the recess.

[0013] [6] In the wafer mounting table described in [5] above, the ceramic base may have a built-in electrostatic electrode, and the heat transfer liquid may be insulating. By applying a voltage to the electrostatic electrode, the wafer can be attracted and fixed to the support surface of the ceramic base by electrostatic attraction. Furthermore, because the heat transfer liquid is insulating, it is less likely to interfere with the attraction and fixation of the wafer by electrostatic attraction.

[0014] [7] In the wafer stage described above (the stage described in [5] or [6] above), the heat transfer liquid may be synthetic oil.

[0015] 1. A plan view of the wafer mounting table 10. A cross-sectional view taken along line A-A in FIG. 1. A partially enlarged cross-sectional view showing the details of the recess 25 and the heat transfer liquid flow path 50. A partially enlarged cross-sectional view showing the state of the recess 25 when the wafer mounting table 10 is in use. A plan view showing the groove 127 and the heat transfer liquid flow path 150. A plan view showing the groove 227 and the heat transfer liquid flow path 250. A plan view showing the groove 327 and the heat transfer liquid flow path 350.

[0016] Next, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a plan view of the wafer mounting table 10, Fig. 2 is a cross-sectional view taken along the line A-A in Fig. 1, and Fig. 3 is a partially enlarged cross-sectional view showing details of the recess 25 and the heat transfer liquid flow path 50. Fig. 3 corresponds to an enlarged view of a portion of the cross-section shown in Fig. 2.

[0017] 2, the wafer mounting table 10 includes a ceramic base 20, a conductive plate 30, a conductive bonding layer 40, and a heat transfer liquid flow path 50. The wafer mounting table 10 is also connected to a switching valve 70, a heat transfer liquid supply source 71, a positive pressure supply source 72, and a negative pressure supply source 73.

[0018] The ceramic base 20 is a circular plate (e.g., 300 mm in diameter and 5 mm in thickness) made of ceramic such as sintered alumina or sintered aluminum nitride. The upper surface of the ceramic base 20 serves as a wafer mounting surface 21 on which a wafer W is mounted. The ceramic base 20 has an electrode 29 built therein.

[0019] The wafer mounting surface 21 of the ceramic substrate 20 has a support surface 22 that supports the wafer W and a recess 25 recessed from the support surface 22. As shown in FIG. 1 , an annular seal band 23 is formed along the outer edge of the wafer mounting surface 21, and multiple circular small protrusions 24 are formed on the entire inner surface of the seal band 23. As shown in FIG. 3 , the upper surfaces of the seal band 23 and the circular small protrusions 24 are flush with each other, and the upper surfaces of the seal band 23 and the circular small protrusions 24 form the support surface 22. A recess 25 is formed on the inner side of the seal band 23. As shown in FIG. 1 , the recess 25 is formed as a circular region inside the seal band 23 in a top view (excluding the portion where the support surface 22 is located, i.e., the portion where the circular small protrusions 24 are located). The recess 25 has a reference surface 26 located lower than the support surface 22 and a groove 27 formed in the reference surface 26. Therefore, the bottom surface of the groove 27 is located lower than the reference surface 26. An opening 51 of the heat transfer liquid flow path 50 is opened in the recess 25. In this embodiment, a plurality of (here, two) heat transfer liquid flow paths 50a, 50b are formed as the heat transfer liquid flow path 50, and each of the openings 51a, 51b opens to the recess 25.

[0020] As shown in FIG. 1 , the groove 27 is formed in a single stroke from one end (the end located near the center of the recess 25) to the other end (the end located near the outer periphery of the recess 25) in a top view. More specifically, the groove 27 is formed by being wound around from one end to the other end in a spiral shape. As a result, the groove 27 is wound around almost the entire recess 25. The groove 27 is arranged to avoid the small circular protrusions 24 in a top view. One end of the groove 27 is an opening 51a of the heat transfer liquid flow path 50a, and the other end is an opening 51b of the heat transfer liquid flow path 50b. Therefore, the groove 27 is formed from one end toward the periphery of the opening 51a (moving away from the opening 51a). Similarly, the groove 27 is formed from the other end toward the periphery of the opening 51b (moving away from the opening 51b). The groove 27 is also formed to connect the openings 51a and 51b.

[0021] The seal band 23 and the small circular protrusions 24 have the same height from the reference surface 26, which is, for example, 5 μm to 50 μm. The depth of the grooves 27 (the height from the reference surface 26 to the bottom surface of the grooves 27) is, for example, 30 μm to 100 μm. In this embodiment, the depth of the grooves 27 is greater than the heights of the seal band 23 and the small circular protrusions 24 from the reference surface 26.

[0022] The electrode 29 is a planar mesh electrode used as an electrostatic electrode and is connected to an external DC power supply via a power supply member (not shown). The layer of the ceramic base 20 above the electrode 29 functions as a dielectric layer. A low-pass filter may be disposed midway along the power supply member. The power supply member is electrically insulated from the conductive bonding layer 40 and the conductive plate 30. When a DC voltage is applied to the electrode 29, the wafer W is attracted and fixed to the wafer mounting surface 21 (specifically, the support surface 22) by electrostatic attraction. When the application of the DC voltage is stopped, the wafer W is released from the wafer mounting surface 21. The electrode 29 is not limited to a mesh electrode and may be a flat electrode.

[0023] The conductive plate 30 is a circular plate with good thermal conductivity (a circular plate with a diameter equal to or larger than that of the ceramic substrate 20). A refrigerant flow path 32 through which a refrigerant circulates is formed within the conductive plate 30. The refrigerant flowing through the refrigerant flow path 32 is preferably a liquid, preferably electrically insulating. Examples of electrically insulating liquids include a fluorine-based inert liquid. In a plan view, the refrigerant flow path 32 is formed in a single stroke from one end (inlet) to the other end (outlet) across the entire conductive plate 30. One end and the other end of the refrigerant flow path 32 are connected to a supply port and a recovery port, respectively, of an external refrigerant device (not shown). The refrigerant supplied from the supply port of the external refrigerant device to one end of the refrigerant flow path 32 passes through the refrigerant flow path 32, returns from the other end of the refrigerant flow path 32 to the recovery port of the external refrigerant device, and is temperature-adjusted before being supplied again from the supply port to one end of the refrigerant flow path 32. The conductive plate 30 is connected to a radio frequency (RF) power source and also serves as an RF electrode.

[0024] Examples of materials for the conductive plate 30 include metal materials and composite materials of metal and ceramic. Metal materials include Al, Ti, Mo, and alloys thereof. Metal-ceramic composite materials include metal matrix composites (MMCs) and ceramic matrix composites (CMCs). Specific examples of such composite materials include materials containing Si, SiC, and Ti (also known as SiSiCTi), porous SiC impregnated with Al and / or Si, and composite materials of Al2O3 and TiC. It is preferable to select a material for the conductive plate 30 that has a thermal expansion coefficient close to that of the material for the ceramic substrate 20.

[0025] The conductive bonding layer 40 is, for example, a metal bonding layer, and bonds the lower surface of the ceramic base 20 and the upper surface of the conductive plate 30. The conductive bonding layer 40 is formed, for example, by thermal compression bonding (TCB). TCB is a known method in which a metal bonding material is sandwiched between two members to be joined, and the two members are pressure-bonded while being heated to a temperature equal to or lower than the solidus temperature of the metal bonding material.

[0026] The heat transfer liquid flow path 50 is provided at least inside the ceramic base 20 and functions as a flow path for the heat transfer liquid 75 (see FIG. 4B described later) between the outside of the wafer mounting table 10 and the inside of the recess 25. As described above, in this embodiment, the heat transfer liquid flow path 50 includes a heat transfer liquid flow path 50a and a heat transfer liquid flow path 50b. The heat transfer liquid flow path 50a has a ceramic base through-hole 52, a bonding layer through-hole 54, and a conductive plate through-hole 56. The ceramic base through-hole 52 is provided inside the ceramic base 20 and is a hole that vertically penetrates the ceramic base 20. The bonding layer through-hole 54 is a hole that vertically penetrates the conductive bonding layer 40. The conductive plate through-hole 56 is a hole that vertically penetrates the conductive plate 30. The opening 51a at the upper end of the ceramic base through-hole 52 of the heat transfer liquid flow path 50a opens to the bottom surface of one end of the groove portion 27, as described above. The ceramic base through-portion 52, the bonding layer through-portion 54, and the conductive plate through-portion 56 of the heat transfer liquid flow path 50a are connected in this order, and the heat transfer liquid flow path 50a as a whole is configured as a through-hole that vertically penetrates the wafer mounting table 10. Similarly, the heat transfer liquid flow path 50b has the ceramic base through-portion 52, the bonding layer through-portion 54, and the conductive plate through-portion 56, and is configured as a through-hole that vertically penetrates the wafer mounting table 10 as a whole. The opening 51b at the upper end of the ceramic base through-portion 52 of the heat transfer liquid flow path 50b opens to the bottom surface of the other end of the groove portion 27, as described above. As shown in FIG. 2 , the opening at the lower end of the conductive plate through-portion 56 of the heat transfer liquid flow path 50a opens to the underside of the conductive plate 30, and a heat transfer liquid supply source 71 and a positive pressure supply source 72 are connected to this opening via a switching valve 70. The opening at the lower end of the conductive plate through-hole 56 of the heat transfer liquid flow path 50b opens to the lower surface of the conductive plate 30, and a negative pressure supply source 73 is connected to this opening.

[0027] The heat transfer liquid supply source 71 supplies the heat transfer liquid 75 to the recess 25 via the heat transfer liquid flow path 50a. The negative pressure supply source 73 supplies negative pressure to the inside of the recess 25 via the heat transfer liquid flow path 50b (applies suction to the inside of the recess 25). Therefore, the heat transfer liquid flow path 50a functions as an inlet for the heat transfer liquid 75 to the recess 25, and the heat transfer liquid flow path 50b functions as an outlet for the heat transfer liquid 75 from the recess 25. The positive pressure supply source 72 supplies positive pressure (gas) to the inside of the recess 25 via the heat transfer liquid flow path 50a. The positive pressure supply source 72 may supply positive pressure to the heat transfer liquid flow path 50a by supplying, for example, He gas. The switching valve 70 switches between supplying the heat transfer liquid 75 from the heat transfer liquid supply source 71 to the heat transfer liquid flow path 50a or supplying positive pressure from the positive pressure supply source 72 to the heat transfer liquid flow path 50a.

[0028] Next, an example of how the wafer mounting table 10 configured as described above is described. First, the wafer mounting table 10 is installed in a chamber (not shown), and the heat transfer liquid supply source 71, positive pressure supply source 72, and negative pressure supply source 73 are connected to the wafer mounting table 10. In this state, a wafer W is placed on the support surface 22 of the wafer mounting surface 21 ( FIG. 4A ). As a result, the space inside the recess 25 is surrounded by the underside of the wafer W and the inner circumferential surface of the recess 25, forming a closed space that is not connected to the outside except through the heat transfer liquid flow path 50. Next, the chamber is depressurized using a vacuum pump to adjust the pressure to a predetermined vacuum level, and a DC voltage is applied to the electrode 29 of the ceramic base 20 to generate an electrostatic adsorption force, thereby adsorbing and fixing the wafer W to the support surface 22 of the wafer mounting surface 21. This makes it difficult for the wafer W to separate from the support surface 22, thereby more reliably closing the space between the underside of the wafer W and the inner circumferential surface of the recess 25. Next, the selector valve 70 is switched to connect the heat transfer liquid supply source 71 to the heat transfer liquid flow path 50a, and the heat transfer liquid 75 is supplied from the heat transfer liquid supply source 71 to the heat transfer liquid flow path 50a. As a result, the heat transfer liquid 75 is introduced into the recess 25 through the opening 51a of the heat transfer liquid flow path 50a, and fills and seals the space surrounded by the underside of the wafer W and the inner circumferential surface of the recess 25 ( FIG. 4B ). In other words, the recess 25 is filled with the heat transfer liquid 75. When the heat transfer liquid 75 is supplied from the heat transfer liquid supply source 71, a negative pressure may be supplied from the negative pressure supply source 73. This allows the heat transfer liquid 75 to be supplied into the recess 25 in a shorter time.

[0029] Next, the chamber is filled with a reactive gas atmosphere at a predetermined pressure (e.g., from over 0.1 Pa to several hundred Pa). In this state, an RF voltage is applied between an upper electrode (not shown) provided on the ceiling of the chamber and the conductive plate 30 of the wafer mounting table 10 to generate plasma. The surface of the wafer W is processed by the generated plasma. At this time, the presence of a heat transfer liquid 75 in the space surrounded by the underside of the wafer W and the inner circumferential surface of the recess 25 efficiently conducts heat between the wafer W and the ceramic substrate 20. A coolant is circulated through the coolant flow path 32 of the conductive plate 30. It is sufficient that the heat transfer liquid 75 is sealed inside the recess 25 while the surface of the wafer W is being processed. However, the supply of the heat transfer liquid 75 from the heat transfer liquid supply source 71 may be continued to replace or circulate the heat transfer liquid 75 inside the recess 25.

[0030] When processing of the wafer W is completed, the heat transfer liquid 75 is removed from the space surrounded by the underside of the wafer W and the inner circumferential surface of the recess 25. For example, by supplying negative pressure from the negative pressure supply source 73 to the heat transfer liquid flow path 50b or by supplying positive pressure from the positive pressure supply source 72 to the heat transfer liquid flow path 50a, the heat transfer liquid 75 is discharged to the outside of the wafer mounting table 10 through the heat transfer liquid flow path 50b. This returns the state to that shown in FIG. 4A . Thereafter, the application of the DC voltage to the electrode 29 is stopped, and the wafer W is moved from the support surface 22.

[0031] As described above, in the wafer mounting table 10 of this embodiment, when processing the wafer W, a heat transfer liquid 75 (backside liquid) is supplied between the underside of the wafer W and the wafer mounting surface 21, rather than a heat transfer gas (backside gas). Because liquids generally have higher thermal conductivity than gases, using the heat transfer liquid 75 instead of a heat transfer gas (e.g., He gas) can increase the thermal conductivity between the wafer W and the wafer mounting table 10 (particularly the ceramic base 20). The heat transfer liquid 75 is preferably an insulating liquid. The insulating properties of the heat transfer liquid 75 make it less likely to interfere with the electrostatic attraction and fixation of the wafer W. The heat transfer liquid 75 preferably has a high dielectric constant. Because the heat transfer liquid 75 in the recess 25 is located between the electrode 29 and the wafer W, a higher dielectric constant of the heat transfer liquid 75 can increase the electrostatic attraction force of the wafer W by the electrode 29, or can achieve the required electrostatic attraction force even with a low DC voltage. The heat transfer liquid 75 is preferably a substance that remains liquid within a pressure range from a predetermined pressure during wafer W processing to atmospheric pressure (e.g., greater than 0.1 Pa and equal to or less than atmospheric pressure) and becomes gaseous at a pressure lower than the lower limit of the pressure during wafer W processing (e.g., equal to or less than 0.1 Pa). This allows the heat transfer liquid 75 to be efficiently removed from the recess 25 after wafer W processing. For example, when performing the process of discharging the heat transfer liquid 75 to the outside of the wafer mounting table 10 through the heat transfer liquid flow path 50b as described above, the wafer W can be moved from the support surface 22 to open the upper portion of the recess 25, and the pressure in the chamber can be further reduced (e.g., to equal to or less than 0.1 Pa). This allows the heat transfer liquid 75 remaining in the recess 25 without being discharged through the heat transfer liquid flow path 50b to be vaporized and removed. Examples of substances that can be used for the heat transfer liquid 75 include synthetic oils. Examples of synthetic oils include silicone oils, fluorine-based fluids, polyglycol oils, ester oils, and hydrocarbon oils. The heat transfer liquid 75 may be any of the substances listed as specific examples of synthetic oil. All of these substances have a higher thermal conductivity than He gas in liquid form. For example, at 100 Torr, the thermal conductivity of He gas is 0.05 W / mK, while the thermal conductivity of silicone oil is 0.1 to 0.25 W / mK. Furthermore, all of these substances are insulating and become gases at pressures of 0.1 Pa or less.Furthermore, all of these substances become liquid at a pressure equal to or higher than a predetermined pressure that is greater than 0.1 Pa and equal to or lower than atmospheric pressure.

[0032] The ceramic base 20 of the wafer mounting table 10 can be manufactured, for example, as follows. First, a disk-shaped ceramic sintered body, which is the basis for the ceramic base 20, is produced by hot-pressing and firing a ceramic powder compact. The ceramic sintered body incorporates electrodes 29. Next, the outer periphery of the ceramic sintered body is cut to form a step. Next, a mask for forming the seal band 23 and the small circular protrusions 24 is attached to the upper surface of the ceramic sintered body, and blasting is performed by spraying blasting media. As a result, a reference surface 26 is formed on the blasted portion of the upper surface of the ceramic sintered body, and the seal band 23 and the small circular protrusions 24 are formed on the masked portion. Next, a mask is attached to the upper surface of the ceramic sintered body except for the portion where the groove 27 is to be formed, and blasting is performed. The mask is then removed. As a result, the groove 27 is formed on the blasted portion of the upper surface of the ceramic sintered body, and the masked portion remains as the seal band 23, the small circular protrusions 24, and the reference surface 26. Thereafter, through holes are formed in the ceramic sintered body to form the heat transfer liquid flow paths 50. As a result, the ceramic sintered body becomes the ceramic base 20 having the seal band 23, the small circular protrusions 24, the recesses 25 (including the reference surface 26 and the grooves 27), and the heat transfer liquid flow paths 50. In parallel with the process of manufacturing the ceramic base 20, the conductive plate 30 is fabricated by a known method, and the conductive plate 30 is bonded to the ceramic base 20 via the conductive bonding layer 40, thereby obtaining the wafer mounting table 10.

[0033] The blasting process for forming the seal band 23, small circular protrusions 24, reference surface 26, and grooves 27 on the ceramic sintered body may be performed as follows: First, a mask is attached to the upper surface of the ceramic sintered body except for the portion where the grooves 27 are to be formed, and blasting is performed to form grooves of the same depth (height) as the depth (height) from the reference surface 26 to the bottom of the grooves 27, and then the mask is removed. Next, a mask for forming the seal band 23 and small circular protrusions 24 is attached to the upper surface of the ceramic sintered body, and blasting is performed by spraying blasting media. As a result, the reference surface 26 is formed in the portion where only the second blasting process was performed, the grooves 27 are formed in the portion where the first and second blasting processes were performed, and the seal band 23 and small circular protrusions 24 are formed in the portion where the blasting process was not performed. Furthermore, the seal band 23, small circular protrusions 24, reference surface 26, and grooves 27 may be formed on the upper surface of the ceramic sintered body by, for example, laser processing, instead of blasting.

[0034] The wafer mounting table 10 described above includes a support surface 22 for supporting a wafer W, a ceramic base 20 having a recess 25 recessed from the support surface 22 on its upper surface, and a heat transfer liquid flow path 50 provided at least inside the ceramic base 20 and serving as a flow path for a heat transfer liquid 75 between the outside and the inside of the recess 25. This allows the heat transfer liquid 75 to be supplied to the inside of the recess 25 on the upper surface (wafer mounting surface 21) of the ceramic base 20 via the heat transfer liquid flow path 50. In other words, the heat transfer liquid 75, rather than a heat transfer gas, can be supplied to the space between the wafer W mounted on the support surface 22 and the inner circumferential surface of the recess 25. Because liquids generally have higher thermal conductivity than gases, the wafer mounting table 10 having such a recess 25 and heat transfer liquid flow path 50 can increase the thermal conductivity between the wafer W and the wafer mounting table 10. This makes it possible, for example, to maintain a lower temperature during processing of the wafer W compared to when a heat transfer gas is used instead of the heat transfer liquid 75, or to increase the RF voltage for generating plasma while maintaining the same temperature during processing of the wafer W.

[0035] The recess 25 also has a reference surface 26 located lower than the support surface 22 and a groove 27 formed in the reference surface 26. The groove 27 is disposed from an opening 51 of the heat transfer liquid flow path 50 leading to the recess 25 toward the periphery of the opening 51. This allows the heat transfer liquid 75 supplied from the opening 51 to the recess 25 via the heat transfer liquid flow path 50 to be guided by the groove 27 and to easily flow around the opening 51. For example, in this embodiment, the heat transfer liquid 75 is supplied to the recess 25 from the opening 51a, and therefore the heat transfer liquid 75 supplied from the opening 51a to the recess 25 is guided by the groove 27 and easily flows from one end of the groove 27 along the groove 27 to the periphery of the opening 51a. This allows the heat transfer liquid 75 to be efficiently distributed inside the recess 25. The reason for this is that the height to the support surface 22 of the space inside the recess 25 is greater in the area where the groove portion 27 exists than in the area where the reference surface 26 exists, and therefore the fluid resistance is lower in the area where the groove portion 27 exists.

[0036] Furthermore, a plurality of heat transfer liquid flow paths 50 (here, two, heat transfer liquid flow path 50a and heat transfer liquid flow path 50b) are provided, each having an opening 51 (51a, 51b) to the recess 25. This allows one or more of the plurality of heat transfer liquid flow paths 50 (50a, 50b) to be used as an inlet of the heat transfer liquid flow path 50, and the remaining as an outlet. Similarly, one or more of the plurality of heat transfer liquid flow paths 50 (50a, 50b) can be used as an outlet of the heat transfer liquid flow path 50, and the remaining as an inlet. This allows the heat transfer liquid 75 to be efficiently supplied to and discharged from the recess 25.

[0037] Furthermore, groove 27 is provided to connect two or more of the multiple openings 51 (here, two, openings 51a and 51b). More specifically, groove 27 is provided to connect opening 51a, which serves as the inlet and outlet of heat transfer liquid 75 into recess 25, among the multiple openings 51. This allows heat transfer liquid 75 supplied from opening 51a of heat transfer liquid flow path 50a to be guided along groove 27 and easily flow toward opening 51b. In this embodiment, groove 27 is routed around substantially the entire recess 25 in a spiral manner from one end to the other. Therefore, groove 27 guides heat transfer liquid 75 supplied from opening 51a toward opening 51b while efficiently spreading the heat transfer liquid throughout the entire recess 25. This allows heat transfer liquid 75 to be filled in a short time into the space surrounded by the underside of wafer W and the inner circumferential surface of recess 25.

[0038] The ceramic base 20 incorporates the electrode 29, which is an electrostatic electrode, and the heat transfer liquid 75 has insulating properties. This allows the wafer W to be attracted and fixed to the support surface 22 of the ceramic base 20 by electrostatic attraction force when a voltage is applied to the electrode 29. Furthermore, because the heat transfer liquid 75 has insulating properties, it is unlikely to interfere with the attraction and fixation of the wafer W by electrostatic attraction force.

[0039] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0040] For example, in the above-described embodiment, the groove portion 27 is configured as a single continuous groove. However, this is not limiting and multiple grooves may be formed in the recess 25. For example, the groove portion 127 shown in FIG. 5 includes a groove portion 127a and a groove portion 127b. The heat transfer liquid flow path 150 includes heat transfer liquid flow paths 150a to 150d. Each of the heat transfer liquid flow paths 150a to 150d has an opening 151 (openings 151a to 151d). The groove portions 127a and 127b are each formed to extend in a spiral shape from one end to the other. As a result, the groove portion 127 (127a, 127b) extends throughout almost the entire recess 25. The groove portion 127a is provided in a region near the center of the recess 25 when viewed from above, and the groove portion 127b is provided in a region near the outer periphery of the recess 25 when viewed from above. One end of groove 127a is open to opening 151a of heat transfer liquid flow path 150a, and the other end is open to opening 151b of heat transfer liquid flow path 150b. One end of groove 127b is open to opening 151c of heat transfer liquid flow path 150c, and the other end is open to opening 151d of heat transfer liquid flow path 150d. Therefore, groove 127a is formed from one end toward the periphery of opening 151a (moving away from opening 151a), and groove 127a is formed from the other end toward the periphery of opening 151b (moving away from opening 151b). Furthermore, groove 127a is provided to connect openings 151a and 151b. Groove 127b is formed from one end toward the periphery of opening 151c (moving away from opening 151c), and groove 127b is formed from the other end toward the periphery of opening 151d (moving away from opening 151d). Groove 127b is also provided to connect openings 151c and 151d. As a result, for example, when heat transfer liquid 75 is supplied from opening 151a of heat transfer liquid flow path 150a, the supplied heat transfer liquid 75 is guided along groove 127a and easily flows toward opening 151b. Similarly, when heat transfer liquid 75 is supplied from opening 151c of heat transfer liquid flow path 150c, the supplied heat transfer liquid 75 is guided along groove 127b and easily flows toward opening 151d.Furthermore, because grooves 127a and 127b are routed around almost the entire recess 25, heat transfer liquid 75 supplied from openings 151a and 151c can be guided by grooves 127a and 127b to efficiently spread throughout the entire recess 25 and toward openings 151b and 151d. This allows heat transfer liquid 75 to be filled in a short time into the space surrounded by the underside of the wafer W and the inner circumferential surface of recess 25. Note that, when multiple grooves 127 are present, each of grooves 127 (127a and 127b) preferably has an opening 151 serving as an inlet and an opening 151 serving as an outlet for heat transfer liquid 75. That is, each of grooves 127a and 127b is preferably provided so as to connect, among the multiple openings 151, an opening 151 serving as an inlet and an opening 151 serving as an outlet for heat transfer liquid 75 into recess 25. Also, for example, either the opening 151a or the opening 151b may be the inlet side, or either the opening 151c or the opening 151d may be the inlet side.

[0041] As an example of a configuration in which multiple grooves are formed in the recess 25, the groove portion 227 shown in FIG. 6 may be employed. The groove portion 227 includes groove portions 227a to 227f. Two heat transfer liquid flow paths 250 (and openings 251) are provided for each of the groove portions 227a to 227f (a total of 12). One of the 12 heat transfer liquid flow paths 250 is provided at one end and the other end of each of the groove portions 227a to 227f. Each of the groove portions 227a to 227f is formed in an arc shape rather than a spiral shape when viewed from above. The groove portions 227a to 227c are formed to form concentric arcs with each other. Similarly, the groove portions 227d to 227f are formed to form concentric arcs with each other. The groove portions 227a to 227c and the groove portions 227d to 227f are formed to be line-symmetrical with each other when viewed from above. 6, the grooves 227 can also guide the heat transfer liquid 75, allowing the heat transfer liquid 75 supplied from the openings 251 to be efficiently distributed throughout the entire recess 25. In the embodiment of FIG. 6, as in the embodiment of FIG. 5, it is preferable that each of the grooves 227 (227a to 227f) has an opening 251 serving as an inlet and an opening 251 serving as an outlet for the heat transfer liquid 75. That is, it is preferable that each of the grooves 227a to 227f is provided so as to connect, among the multiple openings 251, the opening 251 serving as the inlet and the opening 251 serving as the outlet for the heat transfer liquid 75 into the recess 25. Also, as in the embodiment of FIG. 5, either of the openings 251 provided at both ends of each of the grooves 227a to 227f may be the inlet side.

[0042] 5 and 6, any shape of groove 27 may be adopted. For example, although grooves 27, 127, and 227 described above are all provided to connect two openings via a path other than the shortest path, the groove may be provided to connect two openings via the shortest path (a straight path). Furthermore, regardless of the positions of the openings, the groove may be curved or straight in top view.

[0043] As an example of a groove having a linear path formed in the recess 25, a groove portion 327 shown in FIG. 7 may be employed. The groove portion 327 shown in FIG. 7 includes a groove portion 327a and a groove portion 327b. The heat transfer liquid flow path 350 includes one heat transfer liquid flow path 350a and multiple (here, 12) heat transfer liquid flow paths 350b. The heat transfer liquid flow path 350a and the multiple heat transfer liquid flow paths 350b each include one opening 351 (opening 351a and multiple openings 351b). The groove portion 327a is a substantially circular region provided in the center of the recess 25 in a top view. The opening 351a of the heat transfer liquid flow path 350a opens at the center of the groove portion 327a, i.e., the center of the recess 25, in a top view. The plurality of grooves 327b are each connected to the groove 327a and are formed in a straight line extending from the groove 327a toward a region close to the outer periphery of the recess 25 in a top view. As a result, the plurality of grooves 327b are provided so as to extend radially from an opening 351a at the center of the recess 25 toward the outer periphery of the recess 25 in a top view. One end of each of the plurality of grooves 327b (the end close to the center of the recess 25) is connected to the groove 327a, and the grooves 327a and 327b are formed as a single groove as a whole. The other end of each of the plurality of grooves 327b (the end close to the outer periphery of the recess 25) is open to an opening 351b of the heat transfer liquid flow path 350b. Each of the plurality of grooves 327b is formed so as to extend from one end toward the periphery of the opening 351a (moving away from the opening 351a) and from the other end toward the periphery of the opening 351b (moving away from the opening 351b). The grooves 327a and 327b are arranged to connect the opening 351a and each of the plurality of openings 351b via the shortest path. The grooves 327 (grooves 327a and 327b) are formed to be rotationally symmetric (here, 12-fold symmetric) about the center of the recess 25. With such grooves 327, for example, when the opening 351a is the inlet side and the plurality of openings 351b are the outlet sides, and heat transfer liquid 75 is supplied to the recess 25 through the opening 351a, the supplied heat transfer liquid 75 is guided along the grooves 327a and 327b and tends to flow radially from the opening 351a at the center of the recess 25 toward each of the plurality of openings 351b near the outer periphery of the recess 25.Therefore, the heat transfer liquid 75 supplied from the opening 351a can be guided by the grooves 327a and 327b to be efficiently distributed throughout the entire recess 25 and directed toward the plurality of openings 351b. This allows the heat transfer liquid 75 to be filled in the space surrounded by the lower surface of the wafer W and the inner circumferential surface of the recess 25 in a short time. Alternatively, each of the plurality of openings 351b may serve as an inlet for the heat transfer liquid 75, and the opening 351a may serve as an outlet for the heat transfer liquid 75. Unlike the grooves 27, 127, and 227 described above, the groove 327 branches from the groove 327a to the plurality of grooves 327b. In this way, the grooves formed in the recess 25, not limited to the groove 327, may have branches.

[0044] In the above-described embodiment, the groove 27 is formed on the reference surface 26. However, the small circular protrusions 24 and the reference surface 26 may not exist, and the entire recess 25 may be formed as a flow path like the groove 27. That is, the entire portion of the wafer mounting surface 21 other than the groove 27 may serve as the support surface 22. However, because the heat transfer liquid 75 flows less easily than the heat transfer gas, if the reference surface 26 does not exist and the entire recess 25 is formed as the groove 27, there is a concern that it will take a long time to fill the inside of the recess 25 (groove 27) with the heat transfer liquid 75. Therefore, it is preferable to provide the reference surface 26 at a position lower than the support surface 22 as in the above-described embodiment, thereby ensuring a spatial volume inside the recess 25, and then provide the groove 27 on the reference surface 26.

[0045] In the above-described embodiment, the openings 51 of the heat transfer liquid flow paths 50 open to the bottom surface of the groove 27, but this is not limited thereto. For example, at least one of the openings 51a and 51b may open to a position other than the bottom surface of the groove 27. For example, the opening 51a may open to the reference surface 26 near one end of the groove 27. Even in this case, once the heat transfer liquid 75 supplied from the opening 51a to the recess 25 reaches one end of the groove 27, the heat transfer liquid 75 is guided along the groove 27. Alternatively, at least one opening 51 may be provided at a position separated from the groove 27 (a position that is not near the end of the groove 27). However, it is preferable that the openings 51 of the heat transfer liquid flow paths 50 open to the bottom surface of the groove 27, as in the above-described embodiment.

[0046] In the above-described embodiment, the groove 27 may be omitted. That is, the entire bottom surface of the recess 25 may be the reference surface 26. In this case, the opening 51 may be open to the reference surface 26.

[0047] In the above-described embodiment, a plurality of heat transfer liquid flow paths 50 are provided, but the present invention is not limited to this, and the wafer stage 10 may be provided with only one heat transfer liquid flow path 50 .

[0048] In the above-described embodiment, after processing of the wafer W is completed, the heat transfer liquid 75 is removed from the space surrounded by the lower surface of the wafer W and the inner peripheral surface of the recess 25, and then the wafer W is moved from the support surface 22. However, this is not limited to this. For example, the wafer W may be moved from the support surface 22 without removing the heat transfer liquid 75. In this case, the next wafer W to be processed may be placed on the support surface 22 and fixed by suction while the heat transfer liquid 75 remains inside the recess 25, and the wafer W may be processed. In this case, the heat transfer liquid 75 may be replaced with the next wafer W to be processed under a pressure that prevents the heat transfer liquid 75 from evaporating.

[0049] In the above-described embodiment, the ceramic base 20 and the conductive plate 30 are bonded together by the conductive bonding layer 40. However, a non-conductive bonding layer such as a resin bonding layer may be used instead of the conductive bonding layer 40. In this case, the conductive plate 30 can be made of a metal such as Al or Ti.

[0050] In the above-described embodiment, the ceramic base 20 has an electrostatic electrode built in as the electrode 29. However, instead of or in addition to this, a heater electrode (resistance heating element) or an RF electrode may be built in. The wafer mounting table 10 may have two or more of an electrostatic electrode, a heater electrode, and an RF electrode built in the ceramic base 20.

[0051] The present invention can be used in, for example, an apparatus for processing wafers.

[0052] 10 wafer mounting table, 20 ceramic base, 21 wafer mounting surface, 22 support surface, 23 seal band, 24 small circular protrusion, 25 recess, 26 reference surface, 27 groove, 29 electrode, 30 conductive plate, 32 coolant flow path, 40 conductive bonding layer, 50, 50a, 50b heat transfer liquid flow path, 51, 51a, 51b opening, 52 ceramic base penetration, 54 bonding layer penetration, 56 conductive plate penetration, 70 switching valve, 71 heat transfer liquid supply source, 72 positive pressure supply source, 73 negative pressure supply source, 75 heat transfer liquid, 127, 127a, 127b, 227, 227a to 227f, 327, 327a, 327b Groove portion, 150, 150a to 150d, 250, 350, 350a, 350b: heat transfer liquid flow path, 151, 151a to 151d, 251, 351, 351a, 351b: opening, W: wafer.

Claims

1. A wafer mounting table comprising: a ceramic base having, on its upper surface, a support surface for supporting a wafer and a recess recessed from the support surface; and a heat transfer liquid flow path provided at least inside the ceramic base, providing a flow path for heat transfer liquid between the outside and the inside of the recess.

2. The wafer mounting table according to claim 1, wherein the recess has a reference surface that is located lower than the support surface, and a groove portion formed in the reference surface, and the groove portion is disposed from an opening of the heat transfer liquid flow path to the recess toward the periphery of the opening.

3. The wafer stage according to claim 1 or 2, wherein a plurality of the heat transfer liquid flow paths are provided, each having an opening into the recess.

4. The wafer mounting table according to claim 3, wherein the recess has a reference surface located lower than the support surface and a groove formed in the reference surface, the groove being provided so as to connect two or more of the plurality of openings.

5. A wafer mounting table according to claim 1 or 2, comprising: the heat transfer liquid placed in the recess.

6. The wafer stage according to claim 5, wherein the ceramic base has an electrostatic electrode built therein, and the heat transfer liquid has insulating properties.

7. The wafer stage according to claim 5, wherein the heat transfer liquid is a synthetic oil.

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