Wafer mounting table

Abstract

This wafer mounting table 10 is provided, inside a ceramic plate 12 that has a wafer mounting surface 12a on the upper surface, with a sub RF electrode 21 which is a first conductive layer and a jumper 22 which is a second conductive layer, at different heights, and is also provided with a connection part 23 which electrically connects the sub RF electrode 21 and the jumper 22 to each other. The sub RF electrode 21, the jumper 22, and the connection part 23 form a seamless one-piece structure 30.

Description

Wafer mounting table

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

[0002] A conventional wafer mounting table is known that includes, inside a ceramic plate, a disk-shaped main RF electrode, an annular sub-RF electrode provided on the outer periphery of the main RF electrode, a rectangular, planar jumper provided below the sub-RF electrode, and a connecting portion that electrically connects the sub-RF electrode and the jumper. For example, Patent Document 1 discloses such a wafer mounting table that uses a horizontally placed coil as the connecting portion.

[0003] Japanese Patent Application Laid-Open No. 2023-87447

[0004] However, in Patent Document 1, because the coil is used as the connection part, the parts of the sub-RF electrode and the jumper that are in contact with the coil may be deformed by the coil, and the contact resistance between the sub-RF electrode and the coil and the contact resistance between the jumper and the coil may vary from one individual to another, making it difficult to ensure stable electrical connection between the sub-RF electrode, the connection part, and the jumper layer.

[0005] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to ensure stable electrical connection between two conductive layers having different heights.

[0006] [1] The wafer mounting table of the present invention is a wafer mounting table comprising a ceramic plate having a wafer mounting surface on its upper surface, a first conductive layer, a second conductive layer having a different height from the first conductive layer, and a connecting portion electrically connecting the first conductive layer and the second conductive layer, the first conductive layer, the second conductive layer, and the connecting portion being a seamless one-piece structure.

[0007] In this wafer mounting table, the first conductive layer, the second conductive layer, and the connecting portion are a seamless, one-piece structure. This eliminates the risk of disconnection between the first conductive layer and the connecting portion or between the second conductive layer and the connecting portion. This ensures stable electrical connection between the first and second conductive layers, which are at different heights.

[0008] In this specification, "upper" and "lower" do not represent absolute positional relationships, but rather relative positional relationships. Therefore, depending on the orientation of the wafer mounting table, "upper" and "lower" may become "lower" and "upper," "left" and "right," or "front" and "rear." Furthermore, a "seamless one-piece structure" is a structure obtained, for example, by cutting a continuous first conductive layer, a second conductive layer, and a connecting portion from a single sheet of conductive material and then bending the cutout.

[0009] [2] The wafer mounting table of the present invention (the wafer mounting table described in [1]) may include a main RF electrode provided inside the ceramic plate, a sub-RF electrode serving as the first conductive layer provided on the outer periphery of the main RF electrode, a jumper serving as the second conductive layer provided below the sub-RF electrode, a main RF electrode rod electrically connected to the main RF electrode, and a sub-RF electrode rod electrically connected to the jumper. In this wafer mounting table, the sub-RF electrode, the jumper, and the connecting portion form a seamless, one-piece structure. Therefore, there is no risk of disconnection between the sub-RF electrode and the connecting portion or between the jumper and the connecting portion. Therefore, the electrical connection between the sub-RF electrode and the jumper can be stably ensured.

[0010] [3] In the wafer mounting table of the present invention (the wafer mounting table described in [2]), the jumper may include a horizontal conductor provided in the center of the ceramic plate and a plurality of first conductive wires extending horizontally and rotationally symmetrically from the outer edge of the conductor, the connection portion may be a plurality of second conductive wires extending obliquely upward from each of the plurality of first conductive wires, and the sub-RF electrode may be an annular assembly of horizontal conductive arc portions connected to each of the plurality of second conductive wires arranged along the circumferential direction. This allows for relatively easy fabrication of a one-piece structure even when made from a relatively hard conductive material. Furthermore, since the plurality of second conductive wires constituting the connection portion have rotational symmetry, it is possible to suppress variations in plasma density.

[0011] It should be noted that "horizontal" includes not only completely horizontal, but also horizontal within an allowable range (for example, tolerance) (the same applies below).

[0012] [4] In the wafer mounting table of the present invention (the wafer mounting table described in [2] above), the jumper may be a horizontal conductor provided in the center of the ceramic plate, the connection portion may be a plurality of conductive wires extending obliquely upward and rotationally symmetrically from the outer edge of the conductor, and the sub-RF electrode may be an annular assembly of horizontal conductive arc portions connected to each of the plurality of conductive wires, arranged along the circumferential direction. This arrangement also allows for relatively easy fabrication of a one-piece structure, even when made from a relatively hard conductive material. Furthermore, because the plurality of conductive wires constituting the connection portion have rotational symmetry, it is possible to suppress variations in plasma density.

[0013] [5] In the wafer stage of the present invention (the wafer stage according to any one of [2] to [4] above), the boundary between the jumper and the connection portion may be located inside the main RF electrode in a plan view. This allows the inclination angle of the connection portion to be small.

[0014] [6] In the wafer mounting table of the present invention (the wafer mounting table according to any one of [2] to [5] above), the boundary between the jumper and the connecting portion may be a valley fold line in a plan view, and the boundary between the sub-RF electrode and the connecting portion may be a mountain fold line in a plan view. This makes it possible to relatively easily manufacture a one-piece structure.

[0015] [7] In the wafer mounting table of the present invention (the wafer mounting table according to any one of [2] to [5] above), the boundary between the jumper and the connection portion may be a valley fold line in a plan view, and the boundary between the sub-RF electrode and the connection portion may be a valley fold line in a plan view. This allows the inclination angle of the connection portion to be small.

[0016] [8] The wafer mounting table of the present invention (the wafer mounting table described in any one of [2] to [7] above) may include a cylindrical shaft joined to the lower surface of the ceramic plate, and the main RF electrode rod and the sub-RF electrode rod may be disposed in the internal space of the cylindrical shaft. In a wafer mounting table including a cylindrical shaft, the sub-RF electrode rod needs to be disposed in the internal space of the cylindrical shaft, and therefore, application of the present invention is highly significant.

[0017] [9] In the wafer stage of the present invention (the wafer stage according to any one of [1] to [8] above), the one-piece structure may be formed of a conductive mesh. This allows ceramic powder to easily pass through the one-piece structure in the vertical direction during production of a ceramic plate, making it easier for the ceramic powder to be distributed throughout the entire structure.

[0018]

[10] In the wafer stage of the present invention (the wafer stage described in [3] or [4] above), the conductor of the jumper may have a hole penetrating in the vertical direction. In this case, the area of ​​the jumper is smaller than when the jumper does not have a hole.

[0019] 1A and 1B are a longitudinal sectional view of the wafer mounting table 10 installed in a chamber 52; a plan view of the wafer mounting table 10; an explanatory diagram of a one-piece structure 30; an explanatory diagram of a one-piece structure precursor 32; a manufacturing process diagram of the wafer mounting table 10; a longitudinal sectional view of the wafer mounting table 110; a plan view of the wafer mounting table 110; an explanatory diagram of a one-piece structure 80; an explanatory diagram of a one-piece structure precursor 82; a longitudinal sectional view of a wafer mounting table incorporating a resistance heating element 90; a longitudinal sectional view of a wafer mounting table incorporating a resistance heating element 90.

[0020] [First Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a vertical cross-sectional view of a wafer mounting table 10 installed in a chamber 52, Fig. 2 is a plan view of the wafer mounting table 10, Fig. 3 is an explanatory diagram of a one-piece structure 30 (Fig. 3A is a plan view, Fig. 3B is an A-A cross-sectional view), and Fig. 4 is a plan view of a one-piece structure precursor 32.

[0021] The wafer mounting table 10 is used in semiconductor manufacturing equipment, particularly in semiconductor manufacturing equipment that processes wafers W with plasma, and is installed inside a semiconductor process chamber 52, as shown in Fig. 1. The wafer mounting table 10 includes a ceramic plate 12 and a cylindrical shaft 48 joined to the lower surface 12b of the ceramic plate 12. A main RF electrode 20 and a one-piece structure 30 (sub-RF electrode 21, jumper 22, and connection portion 23) are embedded inside the ceramic plate 12.

[0022] The ceramic plate 12 is a disk-shaped plate made of a ceramic material such as aluminum nitride, silicon carbide, silicon nitride, or aluminum oxide. The ceramic plate 12 has a circular wafer-mounting surface 12a on its upper surface. The wafer-mounting surface 12a is embossed to form a plurality of irregularities (not shown). A heat-conducting gas (e.g., He gas) is supplied from the lower surface 12b of the ceramic plate 12 through a gas supply path (not shown) between the recesses provided in the wafer-mounting surface 12a and the wafer W mounted on the wafer-mounting surface 12a. The diameter of the ceramic plate 12 is, for example, 320 to 380 mm.

[0023] The main RF electrode 20 is a circular electrode concentric with the ceramic plate 12 and is disposed facing the wafer mounting surface 12a and parallel to it. "Parallel" includes not only perfect parallelism but also parallelism within an allowable range (e.g., tolerance) (the same applies below). The main RF electrode 20 is an electrode primarily composed of Mo, Nb, W, Ta, carbides thereof, or a high-melting-point composite metal containing two or more of these elements. The main RF electrode is formed of a metal mesh or punched metal, with a metal mesh being preferred. The wire diameter of the metal mesh is preferably 0.1 mm or more (e.g., 0.1 to 2 mm). The "main component" refers to the component with the highest content (the same applies below). An RF voltage is applied between the main RF electrode 20 and an upper electrode (a showerhead 53, described later) when generating plasma in the space above the central region of the wafer W mounted on the wafer mounting surface 12a. The main RF electrode 20 is electrically connected to a main RF electrode rod 40 inserted into the lower surface 12b of the ceramic plate 12. The main RF electrode rod 40 is arranged so as not to come into contact with the jumper 22. The diameter of the main RF electrode 20 is, for example, about 300 mm.

[0024] The auxiliary RF electrode 21 , the jumper 22 and the connection portion 23 are a seamless one-piece structure 30 .

[0025] As shown in FIG. 1 , the sub-RF electrode 21 is embedded inside the ceramic plate 12 at a position higher than the main RF electrode 20. The sub-RF electrode 21 is disposed on the outer circumferential side of the main RF electrode 20. As shown in FIGS. 2 and 3 , the sub-RF electrode 21 is an annular assembly of multiple horizontal conductive arc portions 21 a arranged along the circumferential direction. Adjacent conductive arc portions 21 a of the sub-RF electrode 21 are disposed with a slight gap between them. However, adjacent conductive arc portions 21 a may be disposed so as to overlap each other. As shown in FIG. 2 , the inner diameter of the annular sub-RF electrode 21 is larger than the outer diameter of the main RF electrode 20 and smaller than the diameter of the ceramic plate 12. The width of the sub-RF electrode 21 is preferably 5 to 40 mm.

[0026] As shown in Fig. 1, the jumper 22 is embedded inside the ceramic plate 12 below the main RF electrode 20 and the sub-RF electrode 21. The jumper 22 is electrically connected to a sub-RF electrode rod 41 inserted into the lower surface 12b of the ceramic plate 12. The heightwise distance between the jumper 22 and the sub-RF electrode 21 is preferably 2 to 20 mm. As shown in Figs. 2 and 3, the jumper 22 has a horizontal circular conductor 22a provided in the center of the ceramic plate 12 (Fig. 2) and a plurality of first conductive wires 22b extending horizontally and rotationally symmetrically from the circular conductor 22a. The circular conductor 22a may have a plurality of holes penetrating in the vertical direction.

[0027] As shown in FIG. 1 , the connection portion 23 electrically connects the sub-RF electrode 21 and the jumper 22. As shown in FIGS. 2 and 3 , the connection portion 23 is an assembly of multiple second conductive wires 23a. The multiple second conductive wires 23a extend obliquely upward from each of the multiple first conductive wires 22b constituting the jumper 22 and are connected to each of the multiple conductive arc portions 21a constituting the sub-RF electrode 21. The first conductive wires 22b and the second conductive wire 23a are formed by bending a single horizontal conductive wire 26 ( FIG. 4 ), as described below. A boundary 24 between the first conductive wire 22b and the second conductive wire 23a is a valley fold line in plan view. The boundary 24 is located inside the main RF electrode 20 in plan view. A boundary 25 between the conductive arc portion 21a and the second conductive wire 23a is a mountain fold line in plan view. The boundary 25 is provided on the inner edge side of the sub-RF electrode 21. If the width of the first conductive wire 22b and the second conductive wire 23a is too wide, they will be difficult to bend, and if the width is too narrow, the electrical resistance will increase. Therefore, taking into consideration the balance between these two, it is preferable to set the width of the first conductive wire 22b and the second conductive wire 23a to 5 to 40 mm.

[0028] The one-piece structure 30 is obtained by cutting the continuous auxiliary RF electrode 21, jumper 22, and connector 23 from a single sheet of metal mesh material and then bending the cutout. The metal mesh material may be, for example, Mo, Nb, W, Ta, a carbide thereof, or a high-melting-point composite metal containing two or more of these elements. To fabricate the one-piece structure 30, a planar one-piece structure precursor 32 is first cut out from a single sheet of planar metal mesh material, from which the continuous auxiliary RF electrode 21, jumper 22, and connector 23 are cut out. As shown in FIG. 4 , the one-piece structure precursor 32 includes a circular conductor 22a, a plurality of horizontal conductive wires 26 extending horizontally and rotationally symmetrically from the outer edge of the circular conductor 22a, and a plurality of conductive arc portions 21a connected to each of the horizontal conductive wires 26. Next, each horizontal conductive wire 26 of the one-piece structure precursor 32 is bent in a valley fold along line segment L1 (corresponding to boundary 24). The conductive arc portion 21a is also bent in a mountain fold at a line segment L2 (corresponding to the boundary 25) between the conductive arc portion 21a and the horizontal conductive wire 26. As a result, the gaps between adjacent conductive arc portions 21a narrow, forming the sub-RF electrode 21. The horizontal conductive wire 26 is also bent at line segments L1 and L2, thereby becoming the first conductive wire 22b and the second conductive wire 23a, and the sub-RF electrode 21 and the jumper 22 are at different heights. This results in a one-piece structure 30.

[0029] The cylindrical shaft 48 is made of the same ceramic material as the ceramic plate 12. The cylindrical shaft 48 is joined to the center of the lower surface 12b of the ceramic plate 12 to support the ceramic plate 12. The outer diameter of the cylindrical shaft 48 is smaller than the diameter of the ceramic plate 12. The upper end of the cylindrical shaft 48 is diffusion-bonded to the ceramic plate 12. A main RF electrode rod 40 and a sub-RF electrode rod 41 are arranged in the internal space of the cylindrical shaft 48.

[0030] Next, a manufacturing example of the ceramic plate 12 will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram showing the manufacturing process of the ceramic plate 12. In Fig. 5, the orientation of the ceramic plate 12 is upside down compared to the ceramic plate 12 in Fig. 1.

[0031] First, a first ceramic compact 121 is fabricated using ceramic powder with an average particle size of several microns to several tens of microns ( FIG. 5A ). The first ceramic compact 121 has a shape in which a truncated cone with a smaller diameter than the disc is stacked on top of the disc. It is obtained, for example, by compressing the ceramic powder. Next, a circular metal mesh main RF electrode 20 is placed on the top surface (top surface of the truncated cone) of the first ceramic compact 121 ( FIG. 5B ). Next, ceramic powder is placed on the main RF electrode 20 and compressed to form a disk-shaped second ceramic compact 122 on the main RF electrode 20 ( FIG. 5C ). The diameter of the second ceramic compact 122 is smaller than the diameter of the top surface of the first ceramic compact 121. At this time, the ceramic powder penetrates into the mesh openings of the main RF electrode 20. Next, a one-piece metal mesh structure 30 is placed on top of the second ceramic compact 122, with the jumper 22 facing up ( FIG. 5D ). At this time, the sub-RF electrode 21 contacts the stepped surface of the first ceramic compact 121. The diameter of the jumper 22 is slightly larger than that of the second ceramic compact 122. Next, ceramic powder is placed on the upper surface (exposed surface) of the first ceramic compact 121 and the upper surface of the second ceramic compact 122, and then compressed to form a third ceramic compact 123 ( FIG. 5E ). At this time, the ceramic powder penetrates the mesh openings of the one-piece structure 30 and the main RF electrode 20. This results in a disk-shaped ceramic laminate 124, in which the first to third ceramic compacts 121 to 123 are integrated. The diameter of the ceramic laminate 124 is the same as that of the first ceramic compact 121. The ceramic laminate 124 is then hot-press fired to obtain a ceramic plate 12 ( FIG. 5F ). ​​The diameter of the resulting ceramic plate 12 is the same as that of the ceramic laminate 124, and the thickness of the ceramic plate 12 is approximately half the thickness of the ceramic laminate 124.

[0032] Next, an example of how the wafer stage 10 is used will be described with reference to FIG.

[0033] First, the wafer mounting table 10 is placed inside the chamber 52. The main RF electrode rod 40 is connected to ground via a matcher 50, and the sub-RF electrode rod 41 is connected to ground via a matcher 51. A showerhead 53 is installed in the chamber 52 at a position facing the wafer mounting table 10. A disk-shaped wafer W is placed on the wafer mounting surface 12a of the wafer mounting table 10. In this state, the interior of the chamber 52 is set to a predetermined vacuum atmosphere (or reduced-pressure atmosphere), and plasma is generated in the space above the wafer W while a process gas is supplied from the showerhead 53. Specifically, a high-frequency voltage from a radio-frequency (RF) power supply 54 is applied to the showerhead 53. At the same time, the impedances of the matchers 50 and 51 are independently controlled. Generally, the plasma density in the space above the main RF electrode 20 tends to be higher than the plasma density in the space above the sub-RF electrode 21. Therefore, the impedance of the matcher 50 is set high, and the impedance of the matcher 51 is set low. This allows current to flow more easily through the sub-RF electrode 21 than through the main RF electrode 20, making it possible to make the plasma density in the space above the main RF electrode 20 approximately the same as the plasma density in the space above the sub-RF electrode 21. Then, this plasma is used to perform CVD film formation or etching on the wafer W.

[0034] Here, the correspondence between the components of this embodiment and the components of the present invention will be clarified. The ceramic plate 12 of this embodiment corresponds to the ceramic plate of the present invention, the sub-RF electrode 21 corresponds to the first conductive layer, the jumper 22 corresponds to the second conductive layer, and the connection portion 23 corresponds to the connection portion.

[0035] In the wafer mounting table 10 described above, the sub-RF electrode 21, the jumper 22, and the connecting portion 23 form a seamless one-piece structure 30. Therefore, there is no risk of disconnection between the sub-RF electrode 21 and the connecting portion 23 or between the jumper 22 and the connecting portion 23. Therefore, the electrical connection between the sub-RF electrode 21 and the jumper 22 can be stably ensured.

[0036] The jumper 22 includes a horizontal circular conductor 22a provided in the center of the ceramic plate 12 and multiple first conductive wires 22b extending horizontally and rotationally symmetrically from the outer edge of the circular conductor 22a. The connecting portion 23 includes multiple second conductive wires 23a extending obliquely upward from each of the multiple first conductive wires 22b. The sub-RF electrode 21 is an annular assembly of horizontal conductive arc portions 21a connected to each of the multiple second conductive wires 23a, arranged along the circumferential direction. Therefore, the one-piece structure 30 can be relatively easily fabricated even when made of a relatively hard conductive material (e.g., W or Mo). Furthermore, because the multiple second conductive wires 23a constituting the connecting portion 23 have rotational symmetry, variations in plasma density can be suppressed.

[0037] Furthermore, the boundary 24 between the jumper 22 and the connection portion 23 is located inside the main RF electrode 20 in a plan view. Therefore, the inclination angle θ ( FIG. 3B ) of the connection portion 23 can be made small (i.e., gentle). If the inclination angle θ is small, it is possible to suppress the occurrence of defects around the connection portion 23 during hot-press firing in the manufacturing process of the ceramic plate 12.

[0038] Furthermore, the boundary 24 between the jumper 22 and the connection portion 23 is a valley fold line in plan view, and the boundary between the sub-RF electrode 21 and the connection portion 23 is a mountain fold line in plan view. Therefore, the one-piece structure 30 can be manufactured relatively easily.

[0039] The wafer mounting table 10 also includes a cylindrical shaft 48 joined to the lower surface of the ceramic plate 12, and the main RF electrode rod 40 and the sub-RF electrode rod 41 are disposed in the internal space of the cylindrical shaft 48. In such a wafer mounting table 10, it is necessary to dispose the sub-RF electrode rod 41 in the internal space of the cylindrical shaft 48, and therefore, application of the present invention is highly significant.

[0040] Furthermore, the one-piece structure 30 is formed of a metal mesh (conductive mesh), so that when the ceramic plate 12 is manufactured, the ceramic powder easily passes through the one-piece structure 30 in the vertical direction, and the ceramic powder easily spreads throughout the one-piece structure 30.

[0041] Second Embodiment A wafer mounting table 110 of the second embodiment is the same as the wafer mounting table 10 of the first embodiment, except that a one-piece structure 80 is used instead of the one-piece structure 30. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and their description will be omitted. Fig. 6 is a vertical cross-sectional view of the wafer mounting table 110, Fig. 7 is a plan view of the wafer mounting table 110, Fig. 8 is an explanatory diagram of the one-piece structure 80 (Fig. 8A is a plan view, and Fig. 8B is a B-B cross-sectional view), and Fig. 9 is a plan view of a one-piece structure precursor 82.

[0042] The auxiliary RF electrode 71 , jumper 72 and connection portion 73 are a seamless one-piece structure 80 .

[0043] As shown in FIG. 6 , the sub-RF electrode 71 is embedded inside the ceramic plate 12 at a position higher than the main RF electrode 20. The sub-RF electrode 71 is disposed on the outer circumferential side of the main RF electrode 20. As shown in FIGS. 7 and 8 , the sub-RF electrode 71 is an annular assembly of multiple horizontal conductive arc portions 71 a arranged along the circumferential direction. Adjacent conductive arc portions 71 a of the sub-RF electrode 71 are disposed with a slight gap between them. However, adjacent conductive arc portions 71 a may be disposed so as to overlap each other. As shown in FIG. 7 , the inner diameter of the annular sub-RF electrode 71 is larger than the outer diameter of the main RF electrode 20, and the outer diameter of the annular sub-RF electrode 71 is smaller than the diameter of the ceramic plate 12. The width of the sub-RF electrode 71 is preferably 5 to 40 mm.

[0044] As shown in FIG. 6 , the jumper 72 is embedded inside the ceramic plate 12 below the main RF electrode 20 and the sub-RF electrode 71. The jumper 72 is electrically connected to the sub-RF electrode rod 41 inserted into the lower surface 12 b of the ceramic plate 12. The heightwise distance between the jumper 72 and the sub-RF electrode 71 is preferably 2 to 20 mm. As shown in FIGS. 7 and 8 , the jumper 72 is a horizontal circular conductor provided in the center of the ceramic plate 12 ( FIG. 7 ). The jumper 72 has a plurality of holes 72 c penetrating in the vertical direction. Therefore, the area of ​​the jumper 72 is smaller than if the jumper 72 did not have the holes 72 c.

[0045] As shown in FIG. 6 , the connection portion 73 electrically connects the sub-RF electrode 71 and the jumper 72. As shown in FIGS. 7 and 8 , the connection portion 73 is an assembly of multiple conductive wires 73a. The multiple conductive wires 73a extend obliquely upward from the outer edge of the jumper 72 in a rotationally symmetrical manner and are connected to the multiple conductive arc portions 71a that constitute the sub-RF electrode 71. A boundary 74 between the jumper 72 and the conductive wires 73a is a valley fold line in plan view. The boundary 74 is located inside the main RF electrode 20 in plan view. A boundary 75 between the conductive arc portion 71a and the conductive wires 73a is also a valley fold line in plan view. The boundary 75 is located on the outer edge side of the sub-RF electrode 71. If the width of the conductive wires 73a is too wide, they will be difficult to bend, and if the width is too narrow, electrical resistance will increase. Therefore, taking into account the balance between these two, it is preferable to set the width of the conductive wires 73a to 5 to 40 mm.

[0046] The one-piece structure 80 is obtained by cutting the continuous auxiliary RF electrode 71, jumper 72, and connector 73 from a single sheet of metal mesh material and then bending the cutout. The metal mesh material may be, for example, Mo, Nb, W, Ta, a carbide thereof, or a high-melting-point composite metal containing two or more of these elements. To fabricate the one-piece structure 80, a planar one-piece structure precursor 82 is first cut out from a single sheet of planar metal mesh material, from which the continuous auxiliary RF electrode 71, jumper 72, and connector 73 are cut out. As shown in FIG. 9 , the one-piece structure precursor 82 includes the jumper 72, which is a circular conductor, a plurality of conductive wires 73a extending horizontally and rotationally symmetrically from the outer edge of the jumper 72, and a plurality of conductive arc portions 71a connected to each of the conductive wires 73a. Next, each conductive wire 73a of the one-piece structure precursor 82 is bent in a valley fold along line segment L3 (corresponding to boundary 74). The conductive arc portion 71a is also bent in a valley fold at line segment L4 (corresponding to boundary 75) between the conductive arc portion 71a and the conductive wire 73a. As a result, the multiple conductive arc portions 71a are turned upside down, narrowing the gap between adjacent conductive arc portions 71a and forming the sub-RF electrode 71. Furthermore, by bending both ends of the conductive wire 73a at line segments L3 and L4, the sub-RF electrode 71 and the jumper 72 are at different heights. In this way, a one-piece structure 80 is obtained.

[0047] The manufacturing process of the ceramic plate 12 of the second embodiment is the same as the manufacturing process of the ceramic plate 12 of the first embodiment, except that a one-piece structure 80 is used instead of the one-piece structure 30 .

[0048] In the wafer mounting table 110 described above, the sub-RF electrode 71, the jumper 72, and the connecting portion 73 form a seamless one-piece structure 80. Therefore, there is no risk of disconnection between the sub-RF electrode 71 and the connecting portion 73 or between the jumper 72 and the connecting portion 73. Therefore, the electrical connection between the sub-RF electrode 71 and the jumper 72 can be stably ensured.

[0049] The jumper 72 is a horizontal circular conductor provided in the center of the ceramic plate 12. The connection portion 73 is a plurality of conductive wires 73a extending obliquely upward and rotationally symmetrically from the outer edge of the jumper 72, which is a circular conductor. The sub-RF electrode 71 is an annular assembly in which horizontal conductive arc portions 71a connected to each of the plurality of conductive wires 73a are arranged along the circumferential direction. Therefore, even when the one-piece structure 80 is made of a relatively hard conductive material (e.g., W or Mo), it can be relatively easily manufactured. Furthermore, because the plurality of conductive wires 73a constituting the connection portion 73 are rotationally symmetrical, it is possible to suppress variations in plasma density.

[0050] Furthermore, the boundary 74 between the jumper 72 and the connection portion 73 is located inside the main RF electrode 20 in a plan view. Therefore, the inclination angle θ ( FIG. 8B ) of the connection portion 73 can be made small (i.e., gentle). If the inclination angle θ is small, it is possible to suppress the occurrence of defects around the connection portion 73 during hot-press firing in the manufacturing process of the ceramic plate 12.

[0051] Furthermore, the boundary 74 between the jumper 72 and the connection portion 73 is a valley fold line in plan view, and the boundary between the sub-RF electrode 71 and the connection portion 73 is also a valley fold line in plan view. Therefore, compared to the first embodiment, the inclination angle θ of the connection portion 73 can be made smaller, and a sufficient distance can be secured between the connection portion 73 and the main RF electrode 20.

[0052] The wafer mounting table 110 also includes a cylindrical shaft 48 joined to the lower surface of the ceramic plate 12, and the main RF electrode rod 40 and the sub-RF electrode rod 41 are disposed in the internal space of the cylindrical shaft 48. In such a wafer mounting table 110, it is necessary to dispose the sub-RF electrode rod 41 in the internal space of the cylindrical shaft 48, and therefore, application of the present invention is highly significant.

[0053] Furthermore, the one-piece structure 80 is formed of a metal mesh (conductive mesh), so that when the ceramic plate 12 is manufactured, the ceramic powder can easily pass through the one-piece structure 80 in the vertical direction, and the ceramic powder can easily be distributed throughout the one-piece structure 80.

[0054] [Other Embodiments] It goes without saying that the present invention is not limited to the above-described embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0055] For example, in the first embodiment described above, a resistance heating element (heater electrode) 90 may be embedded inside the ceramic plate 12 as shown in FIGS. 10 and 11 . The resistance heating element 90 is embedded below the main RF electrode 20. FIG. 10 shows an example in which the resistance heating element 90 is embedded below the main RF electrode 20 and the jumper 22, while FIG. 11 shows an example in which the resistance heating element 90 is embedded below the main RF electrode 20 and above the jumper 22. In FIGS. 10 and 11 , the same components as those in the first embodiment are denoted by the same reference numerals. The resistance heating element 90 is provided so as to be wired from one of a pair of terminals across the entire surface of the wafer mounting surface 12 a in a plan view and then to the other of the pair of terminals. Power feed rods 91 are electrically connected to the pair of terminals of the resistance heating element 90, respectively. The power feed rods 91 are connected to a heater power supply (not shown). Note that in FIG. 11 , the power feed rods 91 are provided so as not to come into contact with the jumper 22. The resistance heating element 90 generates heat by receiving power from a heater power supply via a power supply rod 91, thereby heating the wafer W. The resistance heating element 90 may have a shape such as a coil or a ribbon, which is the same as in the second embodiment.

[0056] In the first embodiment described above, the eight first conductive wires 22b are arranged at equal angular intervals (45° intervals) from the outer edge of the circular conductor 22a to have rotational symmetry, but this is not particularly limited. For example, n first conductive wires may be arranged at equal angular intervals ((360 / n)° intervals) from the outer edge of the circular conductor (n is an integer of 2 or greater). This also applies to the second embodiment.

[0057] In the above-described first embodiment, an example has been shown in which the sub-RF electrode 21 is provided above the main RF electrode 20, but this is not particularly limited. For example, the sub-RF electrode 21 may be provided below the main RF electrode 20, or the sub-RF electrode 71 may be provided at the same height as the main RF electrode 20. This also applies to the second embodiment.

[0058] The wafer stage of the present invention is used in, for example, semiconductor manufacturing equipment.

[0059] 10 wafer mounting table, 12 ceramic plate, 12a wafer mounting surface, 12b lower surface, 20 main RF electrode, 21 auxiliary RF electrode, 21a conductive arc portion, 22 jumper, 22a circular conductor, 22b first conductive line, 23 connection portion, 23a second conductive line, 24 boundary, 25 boundary, 26 horizontal conductive line, 30 one-piece structure, 32 one-piece structure precursor, 40 main RF electrode rod, 41 auxiliary RF electrode rod, 48 cylindrical shaft, 50 matching box, 51 matching box, 52 chamber, 53 shower head, 54 high frequency power source, 71 auxiliary RF electrode, 71a conductive arc portion, 72 jumper, 72c hole, 73 connection portion, 73a conductive line, 74 boundary, 75 boundary, 80 one-piece structure, 82 one-piece structure precursor, 90 resistance heating element, 91 Power supply rod, 110 wafer mounting table, 121 first ceramic molded body, 122 second ceramic molded body, 123 third ceramic molded body, 124 ceramic laminate, L1, L2, L3, L4 line segment, W wafer.

Claims

1. A wafer mounting table provided inside a ceramic plate having a wafer mounting surface on top, the wafer mounting table comprising a first conductive layer, a second conductive layer having a height different from that of the first conductive layer, and a connection portion for electrically connecting the first conductive layer and the second conductive layer, wherein the first conductive layer, the second conductive layer, and the connection portion are a seamless one-piece structure, the wafer mounting table.

2. The wafer mounting table according to claim 1, further comprising a main RF electrode provided inside the ceramic plate, a sub-RF electrode as the first conductive layer provided on the outer peripheral side of the main RF electrode, a jumper as the second conductive layer provided below the sub-RF electrode, a rod for the main RF electrode electrically connected to the main RF electrode, and a rod for the sub-RF electrode electrically connected to the jumper.

3. The jumper includes a horizontal conductor provided at the central portion of the ceramic plate and a plurality of first conductive lines extending horizontally and having rotational symmetry from the outer edge of the conductor. The connection portion is a plurality of second conductive lines extending obliquely upward from each of the plurality of first conductive lines. The sub-RF electrode is an annular aggregate in which horizontal conductive arc portions connected to each of the plurality of second conductive lines are arranged along the circumferential direction. The wafer mounting table according to claim 2.

4. The jumper is a horizontal conductor provided at the central portion of the ceramic plate. The connection portion is a plurality of conductive lines extending obliquely upward and having rotational symmetry from the outer edge of the conductor. The sub-RF electrode is an annular aggregate in which horizontal conductive arc portions connected to each of the plurality of conductive lines are arranged along the circumferential direction. The wafer mounting table according to claim 2.

5. The boundary between the jumper and the connection portion is located inside the main RF electrode in a plan view. The wafer mounting table according to any one of claims 2 to 4.

6. The boundary between the jumper and the connection portion is a valley fold line in a plan view, and the boundary between the sub-RF electrode and the connection portion is a mountain fold line in a plan view. The wafer mounting table according to any one of claims 2 to 4.

7. The boundary between the jumper and the connection portion is a valley fold line in a plan view, and the boundary between the sub-RF electrode and the connection portion is a valley fold line in a plan view. The wafer mounting table according to any one of claims 2 to 4.

8. The wafer mounting table according to any one of claims 2 to 4, comprising a cylindrical shaft joined to the lower surface of the ceramic plate, wherein the main RF electrode rod and the sub-RF electrode rod are disposed in the internal space of the cylindrical shaft.

9. The wafer mounting table according to any one of claims 1 to 4, wherein the one-piece structure is formed of a conductive mesh.

10. The wafer mounting table according to claim 3 or 4, wherein the conductor of the jumper has a hole penetrating in the vertical direction.

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