Wafer placement table

Abstract

The wafer mounting table 10 includes a ceramic plate 20 having a wafer mounting surface 22 on its upper surface, a circular first RF electrode 30 embedded in the ceramic plate 20, a first RF terminal 32 electrically connected to the first RF electrode 30, a ring-shaped second RF electrode 40 embedded in the ceramic plate 20 at a depth different from that of the first RF electrode 30 and positioned outside the first RF electrode 30 in a plan view, a second RF terminal 42 electrically connected to the second RF electrode 40, and a connection circuit 50 connecting the second RF terminal 42 and the second RF electrode 40. The connection circuit 50 is formed of mesh-like or radial conductive wires, and the width of the conductive wires increases from the second RF electrode 40 toward the second RF terminal 42.

Description

[Technical field]

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

[0002] Conventionally, a wafer mounting table having two RF electrodes embedded at different depths in a ceramic plate is known. For example, Patent Document 1 discloses a wafer mounting table having two RF electrodes, a circular first RF electrode and an annular second RF electrode located outside the first RF electrode in a plan view. The second RF electrode is connected to an external terminal provided near the center of the ceramic plate via a connection circuit formed of radial conductive wires. Patent Document 2 uses a conductive plate having a plurality of holes with hexagonal or triangular openings as the connection circuit. The parts of the conductive plate surrounding the holes correspond to the conductive wires. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-89694 A [Patent Document 2] Patent No. 5583877 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Documents 1 and 2, the width of the conductive lines is constant, which causes problems such as a large temperature difference within the wafer-mounting surface and an inability to efficiently generate plasma above the wafer-mounting surface.

[0005] The present invention has been made to solve the above-mentioned problems, and has as its main object to efficiently generate plasma while reducing the temperature difference within the wafer-mounting surface. [Means for solving the problem]

[0006] [1] The wafer mounting table of the present invention comprises: a ceramic plate having a wafer mounting surface on an upper surface thereof; a circular first RF electrode embedded in the ceramic plate; a first RF terminal electrically connected to the first RF electrode; a ring-shaped second RF electrode that is embedded in the ceramic plate at a depth different from that of the first RF electrode and is positioned outside the first RF electrode in a plan view; a second RF terminal electrically connected to the second RF electrode; a connection circuit that connects the second RF terminal and the second RF electrode; Equipped with the connection circuit is formed of mesh-like or radial conductive lines, The width of the conductive line increases from the second RF electrode to the second RF terminal. It is something.

[0007] In this wafer mounting table, the connection circuit connecting the second RF terminal and the second RF electrode is formed of mesh-like or radial conductive wires, and the width of the conductive wires becomes wider from the second RF electrode to the second RF terminal. That is, the width of the conductive wires is narrow at the connection portion with the second RF electrode and wide at the connection portion with the second RF terminal. Therefore, compared to the case where the width of the conductive wires is constant at a narrow value, heat generation of the conductive wires forming the connection circuit can be suppressed. As a result, the temperature difference in the wafer mounting surface can be reduced. Also, compared to the case where the width of the conductive wires is constant at a wide value, the overlapping area between the first RF electrode and the connection circuit is smaller, and plasma coupling between the first RF electrode and the connection circuit is reduced. As a result, plasma can be efficiently generated above the wafer mounting surface.

[0008] In this specification, the present invention may be described using terms such as up / down, left / right, front / back, etc., but these terms are merely relative positional relationships. Therefore, when the orientation of the wafer placement table is changed, up / down may become left / right, or left / right may become up / down, but such cases are also included in the technical scope of the present invention. In addition, the width of the conductive line may be gradually or stepwise wider from the second RF electrode to the second RF terminal.

[0009] [2] In the wafer stage of the present invention (the wafer stage described in [1] above), the second RF terminal may be provided at the center of the ceramic plate. This makes it easier to arrange conductive lines forming a connection circuit in a well-balanced manner.

[0010] [3] In the wafer mounting table of the present invention (the wafer mounting table described in [1] or [2] above), the width of the conductive line may be wider from the second RF electrode to the second RF terminal within a range of 5 mm to 15 mm. This makes it possible to appropriately reduce the overlapping area between the first RF electrode and the connection circuit in a plan view while appropriately suppressing heat generation in the connection circuit.

[0011] [4] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [3] above), the connection circuit may be formed of the mesh-like conductive wires and have a polygonal mesh. This makes it easier to bring the average temperature of the wafer mounting surface closer to the target temperature of the wafer mounting surface. Examples of the polygon include a hexagon, a rectangle, and a triangle.

[0012] [5] In the wafer mounting table of the present invention (the wafer mounting table described in [4] above), the width of the innermost line segment of the conductive line connected to the second RF terminal may be the widest, and the width of the line segment of the conductive line closest to the second RF terminal may be the next widest after the innermost line segment. In this way, it is possible to relatively easily design a connection circuit having a polygonal mesh so that the width increases from the second RF electrode to the second RF terminal. [Brief description of the drawings]

[0013] [Figure 1] FIG. [Diagram 2] Cross section AA of Figure 1. [Diagram 3] 4 is an explanatory diagram of a first RF electrode 30 and a second RF electrode 40 with a connection circuit 50 provided inside, as viewed from above. FIG. [Figure 4] FIG. [Diagram 5] FIG. 1 is a schematic explanatory diagram of a plasma enhanced chemical vapor deposition apparatus 80 in which a wafer stage 10 is installed. [Figure 6] FIG. 4 is an explanatory diagram of a comparative example of a connection circuit 50. [Figure 7] FIG. 4 is an explanatory diagram of a comparative example of a connection circuit 50. [Figure 8] FIG. 2 is an illustration of an embodiment of a connection circuit 150. [Figure 9] FIG. 2 is an illustration of an embodiment of a connection circuit 250. [Figure 10] FIG. 4 is an explanatory diagram of a comparative example of a connection circuit 150. [Figure 11] FIG. 4 is an explanatory diagram of a comparative example of a connection circuit 250. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A preferred embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a perspective view of a wafer mounting table 10, Fig. 2 is a cross-sectional view taken along line AA in Fig. 1, Fig. 3 is an explanatory diagram of a plan view of a first RF electrode 30 and a second RF electrode 40 with a connection circuit 50 provided inside, and Fig. 4 is a partially enlarged view of the connection circuit 50.

[0015] The wafer stage 10 is a element Examples of such components include electrostatic chucks, ceramic heaters, etc. The wafer mounting table 10 includes a ceramic plate 20 and a shaft 70.

[0016] The ceramic plate 20 is a disk-shaped plate made of a ceramic material such as aluminum nitride or alumina, and has a circular wafer mounting surface 22 and an annular protrusion 24 on the upper surface. The ceramic plate 20 has a diameter of, for example, about 330 mm and a thickness of, for example, about 20 mm. The diameter of the wafer mounting surface 22 is, for example, about 300 mm, which is approximately the same as the diameter of the wafer W. The annular protrusion 24 is provided so as to surround the wafer mounting surface 22 and to be one step higher than the wafer mounting surface 22. A first RF electrode 30, a second RF electrode 40, and a heater electrode 60 are embedded in the ceramic plate 20 in this order from the side closest to the wafer mounting surface 22.

[0017] The first RF electrode 30 is a circular metal mesh, typically a Mo mesh or a W mesh. The center of the first RF electrode 30 coincides with the center of the ceramic plate 20. The diameter of the first RF electrode 30 is, for example, about 300 mm. The first RF electrode 30 is electrically connected to a first RF terminal 32 near the center of the ceramic plate 20. The first RF electrode 30 is connected to a first power feed rod 34 via the first RF terminal 32. The first power feed rod 34 penetrates the second RF electrode 40 and the heater electrode 60 in a non-contact state, passes through the inside of the shaft 70, and reaches the outside of the shaft 70.

[0018] The second RF electrode 40 is embedded in the ceramic plate 20 at a different depth from the first RF electrode 30. The second RF electrode 40 is an annular metal mesh, typically a Mo mesh or a W mesh. The center of the second RF electrode 40 coincides with the center of the ceramic plate 20. The inner diameter of the second RF electrode 40 is equal to or slightly larger than the diameter of the first RF electrode 30, and the outer diameter is, for example, about 315 mm. The second RF electrode 40 is electrically connected to a second RF terminal 42 provided at the center of the ceramic plate 20 via a connection circuit 50. The second RF electrode 40 is connected to a second power feed rod 44 via the second RF terminal 42. The second power feed rod 44 penetrates the heater electrode 60 in a non-contact state, passes through the inside of the shaft 70, and reaches the outside of the shaft 70.

[0019] The connection circuit 50 is provided at the same depth as the second RF electrode 40 in the ceramic plate 20. The connection circuit 50 is provided inside the second RF electrode 40. The connection circuit 50 is formed of a mesh-like conductive wire 52, and has a hexagonal mesh 54. The center of the connection circuit 50 coincides with the center of the ceramic plate 20, and the second RF terminal 42 is electrically connected to it. The material of the conductive wire 52 is preferably a high-melting point conductive material such as Mo, W, or Nb. The connection circuit 50 can be formed by printing a paste containing such a high-melting point conductive material.

[0020] The width of the conductive wires 52 increases from the annular second RF electrode 40 toward the second RF terminal 42. In this embodiment, the width of the conductive wires 52 is determined as follows. That is, an imaginary small circle C1 and an imaginary large circle C2 are drawn concentrically with the ceramic plate 20 in a plan view. The radius of the imaginary small circle C1 is approximately equal to the length of the sides of the hexagon forming the mesh 54, and the radius of the imaginary large circle C2 is approximately equal to the length of the diagonal line (a diagonal line that does not pass through the center) of the hexagon forming the mesh 54. In this case, the width w1 of the conductive wires 52 located inside the imaginary small circle C1 (three conductive wires 52a) is the largest, the width w2 of the conductive wires 52 located outside the imaginary small circle C1 and inside the imaginary large circle C2 (six conductive wires 52b) is the next largest, and the width w3 of the conductive wires 52 located outside the imaginary small circle C1 (other conductive wires 52c) is the smallest. Expressed as a formula, w1>w2>w3. In other words, the width w1 of the innermost line segment (conductive line 52a) of conductive line 52 that is connected to the second RF terminal 42 is the widest, the width w2 of the line segment (conductive line 52b) of conductive line 52 that is next closest to the second RF terminal 42 after the innermost line segment is the next widest, and the width of the remaining conductive line 52c is the narrowest. In this way, the width of conductive line 52 becomes wider in stages from the annular second RF electrode 40 toward the second RF terminal 42.

[0021] It is preferable that the width of the conductive wire 52 becomes wider within a range of 5 mm to 15 mm from the second RF electrode 40 toward the second RF terminal 42. For example, w3=5 mm, w2=10 mm, and w1=15 mm may be satisfied, or w3=6 mm, w2=8 mm, and w1=10 mm may be satisfied, or w3=6 mm, w2=7 mm, and w1=8 mm may be satisfied.

[0022] The heater electrode 60 is formed so that one end is disposed near the center of the ceramic plate 20, and is wired in a single stroke across almost the entire area of ​​the ceramic plate 20 in a plan view, and then reaches the other end disposed near the center. The heater electrode 60 is preferably made of a high melting point conductive material such as Mo, W, or Nb. Although not shown, a power supply rod is connected to each of one end and the other end of the heater electrode 60, and each power supply rod passes through the inside of the shaft 70 and is connected to a heater power source. The heater electrodes 60 may be provided in multiple stages, vertically.

[0023] The shaft 70 is a cylindrical member made of the same material as the ceramic plate 20. The upper end of the shaft 70 is joined to the lower surface of the ceramic plate 20 (the surface opposite to the wafer mounting surface 22).

[0024] Such a wafer mounting table 10 can be manufactured in accordance with the manufacturing example described in Patent Document 2, for example.

[0025] Next, an example of using the wafer mounting table 10 will be described. FIG. 5 is a schematic explanatory diagram of a plasma-enhanced chemical vapor deposition apparatus 80 in which the wafer mounting table 10 is installed. The wafer mounting table 10, on which the wafer W is mounted on the wafer mounting surface 22, is installed inside a chamber 82 of the plasma-enhanced chemical vapor deposition apparatus 80. Specifically, the lower end of the shaft 70 is installed on the floor surface of the chamber 82 so as to be airtight. As a result, the inside of the shaft 70 is isolated from the inside of the chamber 82. A counter electrode 84 is provided on the ceiling of the chamber 82 at a position facing the wafer mounting table 10. Then, power is supplied to the heater electrode 60 so that the wafer W mounted on the wafer mounting table 10 is heated to a predetermined temperature. Also, the inside of the chamber 82 is depressurized to a predetermined vacuum level by a vacuum pump connected to a gas exhaust port 82a of the chamber 82. Then, a raw material gas for producing a desired film is introduced from a gas inlet 82b of the chamber 82, and the internal pressure of the chamber 82 is adjusted to a predetermined pressure. Then, different radio frequency powers are supplied between the first RF electrode 30 and the counter electrode 84, and between the second RF electrode 40 and the counter electrode 84. Then, plasma is generated between the counter electrode 84 and the wafer mounting table 10, and a desired thin film is formed on the surface of the wafer W.

[0026] In the wafer mounting table 10 described above, the connection circuit 50 connecting the second RF terminal 42 and the second RF electrode 40 is formed of mesh-like conductive wires 52 (52a to 52c), and the width of the conductive wires 52 increases from the second RF electrode 40 toward the second RF terminal 42. That is, the width of the conductive wires 52 is narrow at the connection portion with the second RF electrode 40 and wide at the connection portion with the second RF terminal 42. Therefore, compared to a case where the width of the conductive wires 52 of the connection circuit 50 is constant at a narrow value (for example, the width of the conductive wires 52 is constant at w3 as shown in FIG. 6), heat generation of the conductive wires 52 forming the connection circuit 50 can be suppressed. As a result, the temperature difference within the wafer mounting surface 22 can be reduced. Furthermore, compared to when the width of the conductive line 52 of the connection circuit 50 is constant at a wide value (for example, the width of the conductive line 52 is constant at w1 as shown in FIG. 7), the overlapping area between the first RF electrode 30 and the connection circuit 50 in a plan view is smaller, and plasma coupling between the first RF electrode 30 and the connection circuit 50 is reduced. As a result, plasma can be efficiently generated above the wafer mounting surface 22.

[0027] In addition, the second RF terminal 42 is provided at the center of the ceramic plate 20. This makes it easy to arrange the conductive lines 52 that form the connection circuit 50 in a well-balanced manner. Specifically, the connection circuit 50 is easy to form so as to be substantially rotationally symmetric with the center of the ceramic plate 20 as an axis.

[0028] Furthermore, it is preferable that the width of the conductive lines 52 (52a to 52c) becomes wider within a range of 5 mm to 15 mm from the second RF electrode 40 toward the second RF terminal 42. This makes it possible to appropriately reduce the overlapping area between the first RF electrode 30 and the connection circuit 50 in a plan view while appropriately suppressing heat generation in the connection circuit 50.

[0029] Furthermore, the connection circuit 50 has a polygonal (hexagonal) mesh 54. This makes it easier to bring the average temperature of the wafer mounting surface 22 closer to the target temperature of the wafer mounting surface 22. This point will be described in the following embodiment.

[0030] Furthermore, the width w1 of the innermost line segment (conductive line 52a) of conductive line 52 that is connected to second RF terminal 42 is the widest, and the width w2 of the line segment (conductive line 52b) of conductive line 52 that is next closest to second RF terminal 42 after the innermost line segment is the next widest. Therefore, connection circuit 50 having hexagonal mesh 54 can be designed relatively easily so that the width increases from second RF electrode 40 toward second RF terminal 42.

[0031] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms within the technical scope of the present invention.

[0032] In the above-described embodiment, the connection circuit 50 has a hexagonal mesh 54, but the mesh may be a polygon other than a hexagon. FIG. 8 shows an example of a connection circuit 150 having a triangular mesh 154. The connection circuit 150 is a circuit that connects the second RF terminal 42 and the second RF electrode 40, and overlaps with the first RF electrode 30 in a plan view. The width of the conductive lines 152 forming the connection circuit 150 increases from the annular second RF electrode 40 toward the second RF terminal 42. Specifically, the width of the innermost line segment (conductive line 152a) of the conductive line 152 that is connected to the second RF terminal 42 is the widest, the width of the line segment (conductive line 152b) of the conductive line 152 that is closest to the second RF terminal 42 after the innermost line segment is the next widest, and the width of the other conductive lines 152c is the narrowest.

[0033] In the above-described embodiment, the connection circuit 50 is formed of mesh-like conductive wires 52, but may be formed of radial conductive wires. FIG. 9 shows an example of a connection circuit 250 formed of radial conductive wires 252. The connection circuit 250 is a circuit that connects the second RF terminal 42 and the second RF electrode 40, and overlaps with the first RF electrode 30 in a plan view. The width of the four conductive wires 252 forming the connection circuit 250 increases from the annular second RF electrode 40 toward the second RF terminal 42. Here, the width of the conductive wires 252 increases gradually, not stepwise. The number of radial conductive wires 252 is not limited to four, and may be three, five or more.

[0034] In the above-described embodiment, the width of the conductive line 52 of the connection circuit 50 is set to three stages (w1, w2, w3), but this is not particularly limited to this and may be set to, for example, two stages or four or more stages.

[0035] In the above-described embodiment, a circular electrode is used as the first RF electrode 30, but the present invention is not limited to this. For example, the first RF electrode 30 may be a pair of semicircular electrodes arranged with a gap therebetween to form a substantially circular shape. In this case, the pair of semicircular electrodes are configured to have the same potential when high-frequency power is supplied thereto.

[0036] In the above-described embodiment, the electrostatic electrode is not embedded inside the ceramic plate 20, but the electrostatic electrode may be embedded inside the ceramic plate 20. In this case, the wafer W can be attracted to the wafer mounting surface 22 by applying a DC voltage to the electrostatic electrode. EXAMPLES

[0037] Examples and comparative examples are described below, but the present invention is not limited to the following examples in any way.

[0038] [Example 1] In Example 1, the wafer mounting table 10 (FIGS. 1 to 4) of the above-described embodiment was set to have w1=8 mm, w2=7 mm, and w3=6 mm. The second RF terminal 42 was connected to ground, and the difference between the maximum and minimum temperatures (hereinafter referred to as temperature difference) in the wafer mounting surface 22 was obtained when 2000 W of power was input to the second RF electrode 40. No power was supplied to the first RF electrode 30 or the heater electrode 60. The temperature was measured at 18 predetermined points on the wafer mounting surface 22. As a result, the temperature difference was 44.3°C.

[0039] Separately from this, the target temperature of the wafer mounting surface 22 was set to 300°C, and the power supply to the heater electrode 60 was controlled so that the temperature of the wafer mounting surface 22 would reach the target temperature. At the same time, the second RF terminal 42 was connected to ground, and 2000 W of power was input to the second RF electrode 40. No power was supplied to the first RF electrode 30. The average temperature of the wafer mounting surface 22 at this time was obtained. The temperature was measured at the same points as before. As a result, the average temperature was 306.6°C.

[0040] [Comparative Example 1] In Comparative Example 1, the connection circuit 50 shown in FIG. 6 was used, and the width w3 of the conductive line 52 was fixed at 6 mm, but other than that, the wafer mounting table 10 was the same as that of Example 1. The temperature difference and average temperature were determined in the same manner as in Example 1. As a result, the temperature difference was 58.0°C, and the average temperature was 307.4°C.

[0041] [Example 2] In Example 2, the connection circuit 150 of FIG. 8 was used in place of the connection circuit 50 in the wafer mounting table 10 of the above embodiment, and the width of the conductive line 152a was set to 8 mm, the width of the conductive line 152b to 7 mm, and the width of the conductive line 152c to 6 mm. The temperature difference and average temperature were then calculated in the same manner as in Example 1. As a result, the temperature difference was 20.4°C, and the average temperature was 310.6°C.

[0042] [Comparative Example 2] In Comparative Example 2, the connection circuit 150 shown in FIG. 10 was used, and the width of the conductive wire 152 was fixed at 6 mm, but other than that, the wafer mounting table 10 was the same as that of Example 2. The temperature difference and average temperature were obtained in the same manner as in Example 1. As a result, the temperature difference was 30.7°C, and the average temperature was 311.9°C.

[0043] [Example 3] In Example 3, the connection circuit 250 of Fig. 9 was used in place of the connection circuit 50 in the wafer mounting table 10 of the above embodiment, and the width of the conductive line 252 was set to 6 mm at the connection portion with the second RF electrode 40 and 8 mm at the connection portion with the second RF terminal 42. Then, the temperature difference and average temperature were obtained in the same manner as in Example 1. As a result, the temperature difference was 18.7°C, and the average temperature was 321.9°C.

[0044] [Comparative Example 3] In Comparative Example 3, the connection circuit 250 shown in FIG. 11 was used, and the width of the conductive wire 252 was fixed at 6 mm, but other than that, the wafer mounting table 10 was the same as that of Example 3. The temperature difference and average temperature were obtained in the same manner as in Example 1. As a result, the temperature difference was 22.1°C, and the average temperature was 324.2°C.

[0045] [evaluation] The temperature difference was smaller in Examples 1 to 3 than in the corresponding Comparative Examples 1 to 3. That is, the temperature difference could be reduced when the width of the conductive wire constituting the connection circuit was wider from the second RF electrode to the second RF terminal than when the width was constant at a narrow value. Also, the average temperature could be closer to the target temperature (300°C) when the connection circuit was formed of mesh-like conductive wires as in Examples 1 and 2 than when the connection circuit was formed of radial conductive wires as in Example 3. [Industrial Applicability]

[0046] The present invention relates to a semiconductor element It can be used as a part for manufacturing equipment. [Explanation of symbols]

[0047] 10 wafer mounting table, 20 ceramic plate, 22 wafer mounting surface, 24 protrusion, 30 first RF electrode, 32 first RF terminal, 34 first power feed rod, 40 second RF electrode, 42 second RF terminal, 44 second power feed rod, 50 connection circuit, 52, 52a, 52b, 52c conductive wire, 54 mesh, 60 heater electrode, 70 shaft, 80 plasma enhanced chemical vapor deposition apparatus, 82 chamber, 82a gas exhaust port, 82b gas inlet port, 84 counter electrode, 150 connection circuit, 152, 152a, 152b, 152c conductive wire, 250 connection circuit, 252 conductive wire, C1 imaginary small circle, C2 imaginary large circle, W wafer, w1, w2, w3 width.

Claims

1. a ceramic plate having a wafer mounting surface on an upper surface thereof; a circular first RF electrode embedded in the ceramic plate; a first RF terminal electrically connected to the first RF electrode; a ring-shaped second RF electrode that is embedded in the ceramic plate at a depth different from that of the first RF electrode and is positioned outside the first RF electrode in a plan view; a second RF terminal electrically connected to the second RF electrode; a connection circuit that connects the second RF terminal and the second RF electrode; Equipped with the connection circuit is formed of mesh-like or radial conductive lines, the width of the conductive line increases from the second RF electrode to the second RF terminal; Wafer placement stage.

2. The second RF terminal is provided at the center of the ceramic plate. The wafer stage according to claim 1 .

3. the width of the conductive line is increased from the second RF electrode to the second RF terminal within a range of 5 mm to 15 mm; The wafer stage according to claim 1 .

4. the connection circuit is formed of the mesh-like conductive wires and has a polygonal mesh; The wafer stage according to claim 1 .

5. an innermost line segment of the conductive line connected to the second RF terminal has a largest width, and a line segment of the conductive line that is next closest to the second RF terminal after the innermost line segment has a second largest width; The wafer stage according to claim 4 .