Wafer mounting stage

Abstract

A wafer mounting stage 10 comprising: a ceramic plate 20 that has a wafer mounting surface 21 on an upper surface thereof; a gas path 52 that a gas can pass through in a vertical direction of the ceramic plate 20; a conductive base plate 30 that is joined to a lower surface of the ceramic plate 20 and used as a plasma generation electrode; a gas supply passage 34 that is provided to the inside of the base plate 30 and that communicates with the gas path 52; and a first shield member 61 that is provided surrounding the gas path 52 and that is electrically connected to the base plate 30.

Description

Wafer mounting table

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

[0002] Conventionally, wafer mounting tables are used in semiconductor manufacturing equipment. For example, the wafer mounting table disclosed in Patent Document 1 includes a ceramic plate having a wafer mounting surface on its upper surface, a gas passage through which gas can pass vertically through the ceramic plate, a conductive base plate bonded to the lower surface of the ceramic plate, and a gas supply passage provided within the base plate. The gas passage is configured with a porous plug disposed in a through-hole formed in the ceramic plate. In this wafer mounting table, a high-frequency voltage is applied between the base plate and an upper electrode provided above the wafer to generate plasma above the wafer, and the wafer is processed using the plasma. During this process, helium gas is introduced from the outside into the gas supply passage. The helium gas is then supplied from the gas supply passage through the gas passage to the underside of the wafer, improving thermal conduction between the wafer and the ceramic plate. Because the helium gas passes through the pores of the porous plug, arc discharge on the underside of the wafer can be suppressed compared to when the porous plug is not present. Without the porous plug, arcing would occur when electrons generated by ionization of helium accelerate and collide with other helium particles. However, with the porous plug, arcing is suppressed because the electrons strike the porous plug before colliding with other helium particles. Arcing on the underside of the wafer is undesirable because it alters the wafer and makes it unusable as a device.

[0003] Japanese Patent Application Laid-Open No. 2019-29384

[0004] However, there has been a demand for the development of a new structure for suppressing discharge in the gas passages of such wafer mounting tables.

[0005] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to provide a new structure for suppressing discharge in a gas passage.

[0006] [1] The wafer mounting table of the present invention comprises: a ceramic plate having a wafer mounting surface on its upper surface; a gas passage through which gas can pass in the vertical direction of the ceramic plate; a conductive base plate joined to the lower surface of the ceramic plate and used as a plasma generating electrode; a gas supply passage provided inside the base plate and communicating with the gas passage; and a shielding member provided to surround the gas passage and electrically connected to the base plate.

[0007] This wafer stage is provided with a shield member electrically connected to the conductive base plate, which prevents equipotential lines from entering the lower part of the gas passage when plasma is generated, making it easier to suppress discharge in the gas passage than when no shield member is provided.

[0008] Although the present invention is sometimes described using terms such as up / down, left / right, front / back, etc., these terms merely refer to relative positional relationships. Therefore, when the orientation of the wafer table is changed, up / down may become left / right, or left / right may become up / down, and such cases are also within the technical scope of the present invention.

[0009] [2] In the wafer mounting table described above (the wafer mounting table described in [1] above), the shield member may be provided at a position at least close to the wafer mounting surface. This makes it easier to suppress discharge in the gas passage. Note that "a position close to the wafer mounting surface" refers to a position above half the thickness of the ceramic plate from the wafer mounting surface.

[0010] [3] In the wafer stage described above (the wafer stage described in [1] or [2]), the ceramic plate may have at least one electrode, the gas passage may be provided to pass through an electrode through-hole provided in each of the at least one electrode so that each of the at least one electrode is not exposed to the inner surface of the gas passage, and the shield member may be provided corresponding to each of the at least one electrode and electrically insulated from each of the at least one electrode. This configuration can also prevent equipotential lines generated by the electrodes in the ceramic plate from entering the gas passage.

[0011] [4] In the wafer stage described above (the wafer stage described in any one of [1] to [3] above), the ceramic plate may have a ceramic plate through-hole that passes through the ceramic plate in the vertical direction, and the gas passage may be provided in a plug disposed in the ceramic plate through-hole. This may make it easier to form the gas passage compared to providing the gas passage directly in the ceramic plate itself.

[0012] [5] In the wafer stage described above (the wafer stage described in [4] above), the shielding member may be embedded in the plug. In this way, the shielding member can be built in when the plug is manufactured.

[0013] [6] In the wafer stage described above (the wafer stage described in any one of [1] to [4] above), the shielding member may be embedded in the ceramic plate. In this way, the shielding member can be built in when the ceramic plate is manufactured.

[0014] [7] In the wafer stage described above (the wafer stage described in any one of [1] to [6] above), the gas passage may have a porous body at least in the upper part of the gas passage, through which gas can pass in the vertical direction. Because equipotential lines penetrate the upper part of the gas passage, providing a porous body at least in the upper part of the gas passage can suppress the occurrence of discharge in the upper part of the gas passage. The porous body may be provided only in the upper part of the gas passage (the part of the gas passage where the equipotential lines penetrate), or it may be provided throughout the entire gas passage. In the former case, the gas flow rate can be increased compared to the latter case.

[0015] [8] In the wafer stage described above (the wafer stage described in any one of [1] to [6] above), the gas passage may have a spiral or zigzag portion at least in the upper portion of the gas passage. Because equipotential lines penetrate the upper portion of the gas passage, providing a spiral or zigzag portion at least in the upper portion of the gas passage can suppress the occurrence of discharge in the upper portion of the gas passage. The spiral or zigzag portion may be provided only in the upper portion of the gas passage (the portion of the gas passage where the equipotential lines penetrate), or it may be provided throughout the entire gas passage. In the former case, the gas flow rate can be increased compared to the latter case. The vertical length of the interior of the spiral or zigzag portion is preferably set to a predetermined length (e.g., 0.5 mm, preferably 0.2 mm) or less to suppress discharge therein.

[0016] [9] In the wafer mounting table described above (the wafer mounting table described in any one of [1] to [8] above), the shield member may be a ring-shaped member whose central axis is perpendicular to the wafer mounting surface. This allows the shield member to more easily exhibit its shielding effect. Note that "the central axis is perpendicular to the wafer mounting surface" includes not only the case where the central axis is completely perpendicular to the wafer mounting surface, but also the case where the central axis is nearly perpendicular to the wafer mounting surface (for example, perpendicular within an allowable range such as a tolerance) (the same applies hereinafter).

[0017]

[10] In the wafer mounting table described above (the wafer mounting table described in any one of [1] to [8] above), the shielding member may be a cylindrical member whose central axis is perpendicular to the wafer mounting surface. This makes it easier for the shielding member to exert its shielding effect.

[0018]

[11] In the wafer stage described in

[10] above, a flange may be provided at the upper end of the cylindrical member, which can prevent the electric field strength at the upper end of the cylindrical member from becoming too strong.

[0019] A plan view of the wafer mounting table 10. A cross-sectional view taken along line A-A in FIG. 1. A partially enlarged view of FIG. 2. A partially enlarged cross-sectional view of a comparative embodiment. A manufacturing process diagram of a ceramic plate 20. A partially enlarged cross-sectional view of another embodiment. A partially enlarged cross-sectional view of another embodiment. A partially enlarged cross-sectional view of another embodiment. A partially enlarged cross-sectional view of another embodiment. A partially enlarged cross-sectional view of another embodiment. A partially enlarged cross-sectional view of another embodiment. A partially enlarged cross-sectional view of another embodiment.

[0020] A preferred embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a plan view of a wafer mounting table 10, Fig. 2 is a cross-sectional view taken along the line A-A in Fig. 1, and Fig. 3 is an enlarged view of a portion of Fig. 2. For convenience, the seal band 21a, small circular protrusions 21b, and reference surface 21c of the wafer mounting surface 21 are omitted in Figs. 2 and 3.

[0021] The wafer stage 10 includes a ceramic plate 20 , a gas passage 52 , a base plate 30 , a metal bonding layer 40 , and first and second shield members 61 and 62 .

[0022] The ceramic plate 20 is a circular ceramic plate (e.g., 300 mm in diameter and 5 mm in thickness) made of alumina sintered body, aluminum nitride sintered body, or the like. The upper surface of the ceramic plate 20 serves as a wafer mounting surface 21. The ceramic plate 20 incorporates an electrostatic electrode 22 and a bias electrode 23. The electrostatic electrode 22 is located close to the wafer mounting surface 21 (e.g., 0.3 to 0.6 mm from the wafer mounting surface 21), while the bias electrode 23 is located far from the wafer mounting surface 21. As shown in FIG. 1 , the wafer mounting surface 21 of the ceramic plate 20 is formed with a seal band 21a along its outer edge and with a plurality of small circular protrusions 21b formed all over its surface. The seal band 21a and the small circular protrusions 21b have the same height, e.g., several μm to several tens of μm. The electrostatic electrode 22 is, for example, a planar mesh electrode to which a DC voltage can be applied. When a DC voltage is applied to the electrostatic electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 (specifically, the upper surfaces of the seal bands 21a and the small circular protrusions 21b) by electrostatic attraction, and when the application of the DC voltage is stopped, the wafer W is released from the attraction and fixation to the wafer mounting surface 21. Note that the portion of the wafer mounting surface 21 on which the seal bands 21a and the small circular protrusions 21b are not provided is referred to as the reference surface 21c. The bias electrode 23 is, for example, a planar mesh electrode, and a high frequency bias voltage is applied to attract ions to the wafer W. The bias electrode 23 is a type of plasma generating electrode (RF electrode).

[0023] The gas passage 52 is a passage through which gas can pass in the vertical direction of the ceramic plate 20. Here, the gas passage 52 is provided inside the plug 50 fixed in the plug arrangement hole 24. The plug arrangement hole 24 penetrates the ceramic plate 20 in the vertical direction and is provided so as to communicate with the gas supply path 34 of the base plate 30. The plug arrangement hole 24 penetrates the electrostatic electrode 22 and the bias electrode 23 in the vertical direction, but the electrostatic electrode 22 and the bias electrode 23 are not exposed at the inner circumferential surface of the plug arrangement hole 24. The plug arrangement hole 24 is a tapered hole having an inverted truncated cone space in which the area of ​​the upper opening is larger than the area of ​​the lower opening. The plug arrangement hole 24 is provided at multiple locations on the ceramic plate 20 (e.g., multiple locations equally spaced circumferentially) in a plan view. The plug 50 is a dense ceramic (e.g., made of the same material as the ceramic plate 20) in the shape of an inverted truncated cone and is disposed in the plug arrangement hole 24. The plug 50 is provided with a gas passage 52 extending from the lower surface to the upper surface of the plug 50. The gas passage 52 has a straight portion 52a extending vertically at the bottom of the gas passage 52 and a spiral portion 52b at the top of the gas passage 52. The spiral portion 52b extends from the upper end of the gas passage 52 to at least the position where the equipotential lines EL (see FIG. 3) intersect. The vertical length L (see FIG. 3) of the spiral portion 52b is preferably set to 0.5 mm or less, more preferably 0.2 mm or less, to suppress arc discharge. Arc discharge occurs when electrons generated by ionization of a gas (e.g., helium gas) in the gas passage 52 accelerate in the direction of the electric field lines (a direction perpendicular to the equipotential lines EL) and collide with other helium gas. Such arc discharge can be suppressed by setting the vertical length of the gas passage 52 to 0.5 mm or less (more preferably 0.2 mm or less). Considering the need to ensure sufficient gas flow, it is preferable to set the vertical length of the spiral portion 52b as long as possible within the range that does not cause arc discharge (e.g., 0.1 mm or more).

[0024] The base plate 30 is a conductive circular plate (having the same diameter as or larger than the ceramic plate 20) with good thermal conductivity. A coolant flow path 32 through which a coolant (e.g., an electrically insulating liquid such as a fluorine-based inert liquid) circulates and a gas supply path 34 through which gas is supplied to the gas passage 52 are formed within the base plate 30. The coolant flow path 32 is formed in a single line from the inlet to the outlet across the entire surface of the base plate 30 in a plan view. Examples of materials for the base plate 30 include metals and composite materials. Examples of metals include Mo. Examples of composite materials include composite materials of metals and ceramics. Examples of composite materials of metals and ceramics include metal matrix composites (MMCs) and ceramic matrix composites (CMCs). Specific examples of such composite materials include materials containing Si, SiC, and Ti, and materials in which porous SiC is impregnated with Al and / or Si. A material containing Si, SiC, and Ti is called SiSiCTi, a material in which a porous SiC body is impregnated with Al is called AlSiC, and a material in which a porous SiC body is impregnated with Si is called SiSiC. It is preferable to select a material for the base plate 30 that has a thermal expansion coefficient close to that of the material for the ceramic plate 20. The base plate 30 is used as a source electrode (a type of plasma generating electrode (RF electrode)) to which a source high frequency is applied to generate plasma. For example, the bias high frequency is several hundred kHz, and the source high frequency is several tens to several hundred MHz.

[0025] The gas supply path 34 includes a ring portion 34b that is concentric with the base plate 30 in a plan view, and an inlet portion 34a that introduces gas into the ring portion 34b from the underside of the base plate 30. The ring portion 34b communicates with the gas passages 52 via through holes 42 in the metal bonding layer 40. The number of inlet portions 34a may be, for example, one. The gas introduced into the inlet portion 34a passes through the ring portion 34b and is distributed to each gas passage 52.

[0026] The metal bonding layer 40 bonds the lower surface of the ceramic plate 20 to the upper surface of the base plate 30. The metal bonding layer 40 is formed, for example, by TCB (thermal compression bonding). TCB is a known method in which a metal bonding material is sandwiched between two components to be bonded and the two components are pressure-bonded while heated to a temperature below the solidus temperature of the metal bonding material. The metal bonding layer 40 may be a layer formed of solder or a metal brazing material. The metal bonding layer 40 has a through hole 42. The through hole 42 is provided at a position that connects the gas passage 52 and the gas supply path 34.

[0027] The first and second shield members 61, 62 are ring-shaped members whose central axes are perpendicular to the wafer mounting surface 21 and are arranged to surround the gas passage 52 (here, to surround the plug 50). The width W (FIG. 3) of the ring shape is larger than the diameters of the first and second vias 61a, 62a. The first shield member 61 is arranged to correspond to the electrostatic electrode 22 and be flush with the electrostatic electrode 22. The second shield member 62 is arranged to correspond to the bias electrode 23 and be flush with the bias electrode 23. In other words, the first shield member 61 is arranged close to the wafer mounting surface 21, and the second shield member 62 is arranged in a portion between the position of the first shield member 61 (close to the wafer mounting surface 21) and the lower surface of the ceramic plate 20. The electrostatic electrode 22 has an electrostatic electrode through-hole 22a facing the plug 50. The bias electrode 23 has a bias electrode through-hole 23a facing the plug 50. The first shield member 61 is embedded in the ceramic plate 20 inside the electrostatic electrode through-hole 22a while being electrically insulated from the electrostatic electrode 22. The second shield member 62 is embedded in the ceramic plate 20 inside the bias electrode through-hole 23a while being electrically insulated from the bias electrode 23. The first shield member 61 and the second shield member 62 are electrically connected by a first via 61a extending in the vertical direction, and the second shield member 62 and the metal bonding layer 40 are electrically connected by a second via 62a extending in the vertical direction. At least one first via 61a is required, and at least one second via 62a is also required. Because the metal bonding layer 40 is electrically connected to the base plate 30, the first and second shield members 61, 62 are also electrically connected to the base plate 30. Therefore, the first and second shield members 61, 62 have the same potential as the base plate 30.

[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 a wafer W is placed on the wafer mounting surface 21. The chamber is then depressurized using a vacuum pump to a predetermined vacuum level, and a DC voltage is applied to the electrostatic electrode 22 of the ceramic plate 20 to generate an electrostatic attraction force, thereby attracting and fixing the wafer W to the wafer mounting surface 21 (specifically, the upper surface of the seal band 21a or the upper surface of the small circular protrusions 21b). Next, the chamber is filled with a reactive gas atmosphere at a predetermined pressure (e.g., several tens to several hundreds of Pa). In this state, a source high-frequency voltage is applied between an upper electrode (not shown) installed on the ceiling of the chamber and the base plate 30, and a bias high-frequency voltage is applied between the upper electrode and the bias electrode 23, thereby generating plasma. The surface of the wafer W is processed by the generated plasma. A coolant is circulated through the coolant flow path 32 of the base plate 30. A backside gas is introduced into the gas supply path 34 from a gas cylinder (not shown). A thermally conductive gas (e.g., helium) is used as the backside gas. The backside gas is supplied and sealed in the space between the back surface of the wafer W and the reference surface 21c of the wafer mounting surface 21 through the gas supply path 34, the through-hole 42, and the gas passage 52. The presence of this backside gas ensures efficient thermal conduction between the wafer W and the ceramic plate 20.

[0029] The wafer mounting table 10 includes the first and second shield members 61 and 62 electrically connected to the conductive base plate 30, which can prevent the equipotential lines EL from penetrating into the lower portion of the gas passage 52 (a position farther from the wafer mounting surface 21) during plasma generation. Therefore, discharge in the gas passage 52 is more easily prevented than when the first and second shield members 61 and 62 are not provided. An example of the equipotential lines EL in this embodiment is shown in FIG. 3 , and an example of the equipotential lines EL in a comparative embodiment without the first and second shield members 61 and 62 is shown in FIG. 4 . In the comparative embodiment, as shown in FIG. 4 , horizontal equipotential lines EL exist throughout the entire vertical length of the gas passage 52. In contrast, in this embodiment, as shown in FIG. 3 , although the equipotential lines EL curve and penetrate into the upper portion of the gas passage 52, the equipotential lines EL are prevented from penetrating into the lower portion of the gas passage 52. Therefore, in this embodiment, even if the lower portion of the gas passage 52 has a straight portion 52a extending in the vertical direction, discharge at the straight portion 52a can be prevented.

[0030] Next, a manufacturing example of the wafer mounting table 10 will be described. Since the base plate 30 can be fabricated by a known method, a manufacturing example of the ceramic plate 20 will be described here. FIG. 5 is a manufacturing process diagram of the ceramic plate 20. First, three ceramic green sheets 81, 82, and 83 are prepared, each of which has a shape that roughly matches the shape of the ceramic plate 20 cut horizontally at the surfaces of the electrostatic electrode 22 and the bias electrode 23 ( FIG. 5A ). The first ceramic green sheet 81 is provided with a hole 81a penetrating vertically at the position of the second via 62a, and the second ceramic green sheet 82 is provided with a hole 82a penetrating vertically at the position of the first via 61a ( FIG. 5B ). A pattern of the same shape as the electrostatic electrode 22 and the first shield member 61 is printed on the top surface of the first ceramic green sheet 81 using conductive paste, and the hole 81a is filled with the conductive paste. A pattern identical to the bias electrode 23 and second shield member 62 is printed on the top surface of the second ceramic green sheet 82 using conductive paste, and the holes 82a are filled with the conductive paste ( FIG. 5C ). The second ceramic green sheet 82 is then stacked on the first ceramic green sheet 81, and a third ceramic green sheet 83 is then stacked on top of that. The resulting stack is then hot-press fired to obtain a fired ceramic body 90 ( FIG. 5D ). In addition to the electrostatic electrode 22 and bias electrode 23, the fired ceramic body 90 also contains first and second shield members 61 and 62 and first and second vias 61a and 62b. A plug placement hole 24 is then formed in the fired ceramic body 90 ( FIG. 5E ). A separately fabricated plug 50 is then placed in the plug placement hole 24 and fixed with adhesive to obtain a ceramic plate 20 ( FIG. 5F ).

[0031] The wafer mounting table 10 described above includes the first and second shield members 61, 62 electrically connected to the conductive base plate 30, thereby preventing the equipotential lines EL from entering the lower portion of the gas passage 52 (a position far from the wafer mounting surface 21) during plasma generation. Therefore, discharge in the gas passage 52 is more easily prevented than in a case where the first and second shield members 61, 62 are not provided. As a result, the design flexibility of the lower portion of the gas passage 52 is increased. For example, unlike the wafer mounting table 10 described above, the discharge countermeasure (spiral shape) at the lower portion of the gas passage 52 can be omitted and the straight portion 52a can be used.

[0032] The ceramic plate 20 also has an electrostatic electrode 22 and a bias electrode 23. The gas passage 52 passes through an electrostatic electrode through-hole 22a so that the electrostatic electrode 22 is not exposed to the inner surface of the gas passage 52, and the bias electrode 23 passes through a bias electrode through-hole 23a so that the bias electrode 23 is not exposed to the inner surface of the gas passage 52. A first shield member 61 is provided corresponding to the electrostatic electrode 22 and electrically insulated from the electrostatic electrode 22, and a second shield member 62 is provided corresponding to the bias electrode 23 and electrically insulated from the bias electrode 23. This makes it possible to prevent equipotential lines generated by the electrostatic electrode 22 and the bias electrode 23 in the ceramic plate 20 from entering the gas passage 52.

[0033] Furthermore, the ceramic plate 20 has a plug placement hole 24 (ceramic plate through-hole) that passes through the ceramic plate 20 in the vertical direction, and the gas passage 52 is provided in the plug 50 that is placed in the plug placement hole 24. Therefore, it may be easier to form the gas passage 52 than when the gas passage 52 is provided directly in the ceramic plate 20 itself.

[0034] Furthermore, the first and second shielding members 61, 62 are embedded in the ceramic plate 20. Therefore, as shown in FIG. 5, the first and second shielding members 61, 62 can be built in when manufacturing the ceramic plate 20.

[0035] Furthermore, the gas passage 52 has a straight portion 52a and a spiral portion 52b at the bottom of the gas passage 52. As shown in Fig. 3, the equipotential line EL enters the upper portion of the gas passage 52. Therefore, by providing the spiral portion 52b at the upper portion of the gas passage 52, it is possible to suppress the occurrence of discharge at the upper portion of the gas passage 52.

[0036] Furthermore, the first and second shield members 61 and 62 are ring-shaped members whose central axes are perpendicular to the wafer mounting surface 21. Therefore, the first and second shield members 61 and 62 can easily exhibit a shielding effect.

[0037] 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.

[0038] In the above-described embodiment, the gas passage 52 has a straight portion 52a at the bottom and a spiral portion 52b at the top. However, the gas passage 52 may be replaced with a gas passage 152 shown in FIG. 6 . In FIG. 6 , the same components as those in the above-described embodiment are denoted by the same reference numerals. The gas passage 152 is a spiral passage extending from the bottom surface of the plug 50 to the top surface. This configuration also achieves the same effects as the above-described embodiment. However, the gas passage 52 has fewer spiral portions than the gas passage 152, allowing for easier gas flow and thus increasing the gas flow rate. Therefore, when the gas passages 52 are employed, the number of gas passages can be reduced compared to the case where the gas passages 152 are employed. This reduces manufacturing costs. Furthermore, the gas passages 52 become temperature singularities on the wafer W. Reducing the number of gas passages 52 reduces the temperature singularities and improves thermal uniformity. The spiral portion 52b of the gas passage 52 may be replaced with a zigzag portion, or the spiral shape of the gas passage 152 may be replaced with a zigzag passage.

[0039] In the above-described embodiment, a dense plug 50 having a gas passage 52 therein is employed. However, a plug 250 shown in FIG. 7 may be employed instead of the plug 50. In FIG. 7, the same components as those in the above-described embodiment are denoted by the same reference numerals. The plug 250 is a plug (porous plug) made of a porous material. The plug 250 is provided in the upper portion of the plug placement hole 24 (e.g., the section from the upper end of the plug placement hole 24 to the position where the equipotential line EL enters). Gas can pass vertically through the fine pores in the porous material of the plug 250. Therefore, the fine pores in the porous material serve as gas passages. This configuration also achieves the same effects as the above-described embodiment. The plug 250 may be provided throughout the entire plug placement hole 24. However, providing the plug 250 only in the upper portion of the plug placement hole 24 facilitates gas flow compared to providing the plug 250 throughout the entire hole. This increases the gas flow rate, thereby reducing the number of plugs 250. This reduces manufacturing costs. Furthermore, the plugs 250 become temperature singularities of the wafer W, but by reducing the number of plugs 250, the temperature singularities are reduced and the temperature uniformity is improved.

[0040] In the above-described embodiment, the first and second shielding members 61, 62 and the first and second vias 61 a, 62 b are embedded in the ceramic plate 20, but as shown in Fig. 8 , they may be embedded in the plug 50. In this way, the first and second shielding members 61, 62 and the first and second vias 61 a, 62 b can be fabricated when manufacturing the plug 50. Such a plug 50 can be manufactured using, for example, a 3D printer.

[0041] In FIG. 8 , the first and second shield members 61 and 62 and the first and second vias 61 a and 62 b are embedded in the plug 50. However, instead of these, a shield member 361 shown in FIG. 9 may be employed. The shield member 361 is a cylindrical member whose central axis is perpendicular to the wafer mounting surface 21. The lower end of the shield member 361 is electrically connected to the metal bonding layer 40. Therefore, the shield member 361 is electrically connected to the base plate 30 via the metal bonding layer 40. The upper end of the shield member 361 is located near the wafer mounting surface 21 (here, the same position as the electrostatic electrode 22). In other words, the shield member 361 is located not only near the wafer mounting surface 21 but also over the entire area between that position and the lower surface of the ceramic plate 20. In this case, the entire shield member 361 is at the same potential as the base plate 30. Because the shield member 361 is a cylindrical member, it is easy to exhibit a shielding effect. Such a cylindrical shield member 361 may be embedded in the ceramic plate 20 instead of the plug 50, but it is easier to manufacture it by embedding it in the plug 50. The plug 50 in Fig. 9 can be manufactured using, for example, a 3D printer.

[0042] 9, the cylindrical shield member 361 is embedded in the plug 50, but as shown in FIG. 10, an outward flange portion 361f may be provided at the upper end of the shield member 361. In this case, the entire shield member 361 including the flange portion 361f has the same potential as the base plate 30. This makes it possible to prevent the electric field strength at the upper end of the cylindrical shield member 361 from becoming too strong.

[0043] In FIG. 9 , the cylindrical shielding member 361 is electrically connected to the base plate 30 via the metal bonding layer 40. However, as shown in FIG. 11 , the shielding member 361 may be electrically connected to the base plate 30 via a metal spring 370. The metal spring 370 is disposed in the gas supply path 34 and the through-hole 42 of the metal bonding layer 40. The metal spring 370 is disposed in a compressed state between the lower end of the shielding member 361 and the bottom surface of the gas supply path 34 (ring portion 34b) of the base plate 30. While FIG. 11 illustrates the metal spring 370, any conductive elastic member that allows gas to pass in the vertical direction is not limited to the metal spring 370. For example, a metal mesh or a mass of metal fibers that can expand and contract in the vertical direction may also be used. This structure is particularly useful when a resin adhesive layer is used instead of the metal bonding layer 40.

[0044] 11 , a conductive film 372 may be provided, which covers the underside of the plug 50 and also covers a portion of the underside of the ceramic plate 20 (around the plug placement hole 24), as shown in FIG. 12 . In FIG. 12 , the same components as those in the above-described embodiment are denoted by the same reference numerals. The conductive film 372 is formed, for example, by sputtering. A through-hole 372 a is provided in the conductive film 372 at a position facing the gas passage 52. Therefore, the conductive film 372 maintains communication between the gas supply path 34 and the gas passage 52. The shield member 361 is electrically connected to the base plate 30 via the conductive film 372 and the metal bonding layer 40.

[0045] In the above-described embodiment, the electrostatic electrode 22 and the bias electrode 23 are embedded in the ceramic plate 20. However, at least one of the electrostatic electrode 22, the bias electrode 23, and the heater electrode capable of heating the wafer W may be embedded in the ceramic plate 20. Alternatively, these electrodes may not be embedded in the ceramic plate 20. For example, when only the electrostatic electrode 22 is embedded in the ceramic plate 20, the first shield member 61 may be left and the second shield member 62 may be omitted, as shown in FIG. 13, and the first shield member 61 may be electrically connected to the base plate 30 via an internal via 461a in the ceramic plate 20. Furthermore, when no electrodes are embedded in the ceramic plate 20, the first shield member 61 may be left and the second shield member 62 may be omitted, as shown in FIG. 13, and the first shield member 61 may be electrically connected to the base plate 30 via an internal via 461a in the ceramic plate 20. While at least one shield member is effective in suppressing discharge, the use of multiple shield members can more effectively suppress discharge. Furthermore, the shielding member does not need to be provided at the same height as each electrode (electrostatic electrode 22 and bias electrode 23), but may be provided at a different height.

[0046] In the above-described embodiment, the first shield member 61 is provided at a position close to the wafer mounting surface 21 (a position above half the thickness of the ceramic plate 20 from the wafer mounting surface 21), but this is not particularly limited. For example, the first shield member 61 may be provided at any position. However, from the viewpoint of suppressing discharge in the gas passage, it is preferable to provide the first shield member 61 at a position above two-thirds the thickness of the ceramic plate 20 from the wafer mounting surface 21, and it is more preferable to provide the first shield member 61 at a position above half the thickness of the ceramic plate 20 from the wafer mounting surface 21.

[0047] In the above-described embodiment, the ceramic plate 20 and the base plate 30 are joined by the metal joining layer 40, but a resin adhesive layer may be used instead of the metal joining layer 40. In this case, the electrical connection between the second via 62a and the base plate 30 may be made by using the metal spring 370 shown in FIG. 11 or by using a conductive wire that passes through the resin adhesive layer in the vertical direction.

[0048] In the above-described embodiment, the gas supply path 34 includes the inlet portion 34 a and the ring portion 34 b, but is not limited to this. For example, the gas supply path may be a base plate through-hole that vertically penetrates the base plate 30 and communicates with the gas passage 52.

[0049] In the above-described embodiment, the internal space of the plug placement hole 24 is an inverted truncated cone space, but it may be a cylindrical space. In this case, the plug 50 is also cylindrical.

[0050] In the above-described embodiment, the plug 50 is disposed in the plug disposing hole 24, but the plug 50 does not have to be disposed in the plug disposing hole 24. In this case, the plug disposing hole 24 serves as a gas passage.

[0051] The present invention can be used for wafer mounting tables used in semiconductor manufacturing equipment, such as ceramic heaters, electrostatic chuck heaters, and electrostatic chucks.

[0052] 10 wafer mounting table, 20 ceramic plate, 21 wafer mounting surface, 21a seal band, 21b small circular protrusion, 21c reference surface, 22 electrostatic electrode, 22a electrostatic electrode through-hole, 23 bias electrode, 23a bias electrode through-hole, 24 plug placement hole, 30 base plate, 32 coolant flow path, 34 gas supply path, 34a introduction portion, 34b ring portion, 40 metal bonding layer, 42 through-hole, 50 plug, 52 gas passage, 52a straight portion, 52b spiral portion, 61 first shielding member, 61a first via, 62 second shielding member, 62a second via, 81, 82, 83 ceramic green sheet, 81a, 82a hole, 90 ceramic sintered body, 152 gas passage, 250 plug, 361 shielding member, 361f flange portion, 370 Metal spring, 372...conductive film, 372a...through hole, 461a internal via.

Claims

1. A wafer mounting table comprising: a ceramic plate having a wafer mounting surface on its upper surface; a gas passage that allows gas to pass through the ceramic plate in the vertical direction; a conductive base plate that is bonded to the lower surface of the ceramic plate and is used as a plasma generating electrode; a gas supply passage that is provided inside the base plate and communicates with the gas passage; and a shielding member that is provided to surround the gas passage and is electrically connected to the base plate.

2. The wafer mounting table according to claim 1, wherein the shield member is provided at a position at least close to the wafer mounting surface.

3. The wafer stage according to claim 1 or 2, wherein the ceramic plate has at least one electrode, the gas passage is provided to pass through an electrode through-hole provided in each of the at least one electrode so that each of the at least one electrode is not exposed to the inner surface of the gas passage, and the shielding member is provided corresponding to each of the at least one electrode and is electrically insulated from each of the at least one electrode.

4. The wafer stage according to claim 1 or 2, wherein the ceramic plate has a ceramic plate through-hole that passes through the ceramic plate in the vertical direction, and the gas passage is provided in a plug disposed in the ceramic plate through-hole.

5. The wafer stage according to claim 4, wherein the shielding member is embedded in the plug.

6. The wafer stage according to claim 1 or 2, wherein the shielding member is embedded in the ceramic plate.

7. The wafer stage according to claim 1 or 2, wherein the gas passage has a porous body at least in an upper portion of the gas passage, through which gas can pass in the vertical direction.

8. The wafer stage according to claim 1 or 2, wherein the gas passage has a spiral portion or a zigzag portion at least in an upper portion of the gas passage.

9. The wafer mounting table according to claim 1 or 2, wherein the shield member is a doughnut-shaped member whose central axis is in a direction perpendicular to the wafer mounting surface.

10. The wafer mounting table according to claim 1 or 2, wherein the shield member is a cylindrical member whose central axis is perpendicular to the wafer mounting surface.

11. The wafer stage according to claim 10, wherein a flange portion is provided at the upper end of the cylindrical member.

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