CERAMIC HEATER AND THERMOCOUPLE GUIDE

Abstract

A ceramic heater includes a ceramic plate having a wafer placement surface, a tubular shaft having one end that is bonded to a rear surface of the ceramic plate on an opposite side to the wafer placement surface, a within-shaft region of the rear surface of the ceramic plate, an elongate hole extending from a start point in an outer peripheral portion of the within-shaft region to a terminal end position in the outer peripheral portion of the ceramic plate, and a thermocouple guide that guides a tip end of an outer-peripheral-side thermocouple to come into the start point of the elongate hole. A portion of the thermocouple guide, the portion extending from the other end (lower end) of the tubular shaft to the start point of the elongate hole, is formed in a shape following an inner wall of the tubular shaft.

Claims

1. A ceramic heater comprising: a ceramic plate having a disk shape and having a wafer placement surface; a tubular shaft having one end that is bonded to a rear surface of the ceramic plate on an opposite side to the wafer placement surface; an inner-peripheral-side resistance heating element that is embedded in an inner peripheral portion of the ceramic plate; an outer-peripheral-side resistance heating element that is embedded in an outer peripheral portion of the ceramic plate; a within-shaft region of the rear surface of the ceramic plate, the within-shaft region locating within the tubular shaft; an elongate hole that extends from a start point in an outer peripheral portion of the within-shaft region to a predetermined terminal end position in the outer peripheral portion of the ceramic plate; associated parts that are disposed in the within-shaft region and that include a pair of terminals of the inner-peripheral-side resistance heating element and a pair of terminals of the outer-peripheral-side resistance heating element; and a thermocouple guide that guides a tip end of a thermocouple to come into the start point of the elongate hole, wherein a portion of the thermocouple guide, the portion extending from the other end of the tubular shaft to the start point of the elongate hole, is formed in a shape following an inner wall of the tubular shaft.

2. The ceramic heater according to claim 1, wherein the thermocouple guide is curved toward the start point of the elongate hole in a shape defining part of a spiral along the inner wall of the tubular shaft.

3. The ceramic heater according to claim 1, wherein the thermocouple guide is curved to gradually change a direction to finally orient in a lengthwise direction of the elongate hole of the ceramic plate while approaching the elongate hole.

4. The ceramic heater according to claim 1, wherein the elongate hole is curved toward the terminal end position from the start point.

5. The ceramic heater according to claim 2, wherein the elongate hole is curved toward the terminal end position from the start point, and a direction in which the elongate hole is curved matches a direction in which the thermocouple guide is curved, when viewing the ceramic heater from the other end side of the tubular shaft.

6. The ceramic heater according to claim 1, further comprising a thermocouple that is arranged to extend from the other end of the tubular shaft, to pass through the elongate hole, and to reach the terminal end position while being guided by the thermocouple guide.

7. A ceramic heater comprising: a ceramic plate having a disk shape and having a wafer placement surface; a tubular shaft having one end that is bonded to a rear surface of the ceramic plate on an opposite side to the wafer placement surface; an inner-peripheral-side resistance heating element that is embedded in an inner peripheral portion of the ceramic plate; an outer-peripheral-side resistance heating element that is embedded in an outer peripheral portion of the ceramic plate; a within-shaft region of the rear surface of the ceramic plate, the within-shaft region locating within the tubular shaft; an elongate hole that extends from a start point in an outer peripheral portion of the within-shaft region to a predetermined terminal end position in the outer peripheral portion of the ceramic plate; associated parts that are disposed in the within-shaft region and that include a pair of terminals of the inner-peripheral-side resistance heating element and a pair of terminals of the outer-peripheral-side resistance heating element; and a thermocouple that is arranged to extend from the other end of the tubular shaft, to pass through the elongate hole, and to reach the terminal end position, wherein a portion of the thermocouple, the portion extending from the other end of the tubular shaft to the start point of the elongate hole, is formed in a shape following an inner wall of the tubular shaft.

8. The ceramic heater according to claim 7, wherein the thermocouple is curved toward the start point of the elongate hole in a shape defining part of a spiral along the inner wall of the tubular shaft.

9. The ceramic heater according to claim 7, wherein the thermocouple is curved to gradually change a direction to finally orient in a lengthwise direction of the elongate hole of the ceramic plate while approaching the elongate hole.

10. The ceramic heater according to claim 7, wherein the elongate hole is curved toward the terminal end position from the start point.

11. The ceramic heater according to claim 8, wherein the elongate hole is curved toward the terminal end position from the start point, and a direction in which the elongate hole is curved matches a direction in which the thermocouple is curved, when viewing the ceramic heater from the other end side of the tubular shaft.

12. A thermocouple guide in which a region from a tip end portion to a base end portion or a region from the tip end portion to a midway point before reaching the base end portion is curved to define part of a spiral.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a perspective view of a ceramic heater 10.

[0040] FIG. 2 is a sectional view taken along A-A in FIG. 1.

[0041] FIG. 3 is a sectional view taken along B-B in FIG. 1.

[0042] FIG. 4 is an explanatory view illustrating an example of a thermocouple guide 32 in a tubular shaft 40.

[0043] FIG. 5 is an explanatory view illustrating another example of the ceramic heater 10.

[0044] FIG. 6 is an explanatory view illustrating another example of the ceramic heater 10.

[0045] FIG. 7 is an explanatory view illustrating an example of a position of a temperature measurement portion 50a of an outer-peripheral-side thermocouple 50.

[0046] FIG. 8 is an explanatory view of a related-art ceramic heater.

DETAILED DESCRIPTION OF THE INVENTION

[0047] Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a ceramic heater 10, FIG. 2 is a sectional view taken along A-A in FIG. 1, FIG. 3 is a sectional view taken along B-B in FIG. 1, and FIG. 4 is an explanatory view illustrating an example of a thermocouple guide 32 in a tubular shaft 40.

[0048] The ceramic heater 10 is used to heat a wafer W on which processing, such as etching or CVD, is to be performed, and is installed within a vacuum chamber (not illustrated). The ceramic heater 10 includes a disk-shaped ceramic plate 20 having a wafer placement surface 20a, and a tubular shaft 40 that is bonded to a surface (rear surface) 20b of the ceramic plate 20 opposite to the wafer placement surface 20.

[0049] The ceramic plate 20 is a disk-shaped plate made of a ceramic material represented by aluminum nitride or alumina. The diameter of the ceramic plate 20 is not limited to a particular value and may be about 300 mm, for example. The ceramic plate 20 is divided into an inner-peripheral-side zone Z1 of a small circular shape and an outer-peripheral-side zone Z2 of an annular shape by a virtual boundary 20c (see FIG. 3) concentric to the ceramic plate 20. An inner-peripheral-side resistance heating element 22 is embedded in the inner-peripheral-side zone Z1 of the ceramic plate 20, and an outer-peripheral-side resistance heating element 24 is embedded in the outer-peripheral-side zone Z2. The resistance heating elements 22 and 24 are each constituted by a coil containing, as a main component, molybdenum, tungsten, or tungsten carbide, for example. As illustrated in FIG. 2, the ceramic plate 20 is fabricated by surface-bonding an upper plate P1 and a lower plate P2 thinner than the upper plate P1.

[0050] The tubular shaft 40 is made of a ceramic material, such as aluminum nitride or alumina, like the ceramic plate 20. An upper end of the tubular shaft 40 is bonded to the ceramic plate 20 by diffusion bonding.

[0051] As illustrated in FIG. 3, the inner-peripheral-side resistance heating element 22 is formed such that it starts from one of a pair of terminals 22a and 22b and reaches the other of the pair of terminals 22a and 22b after being wired in a one-stroke pattern over substantially the entirety of the inner-peripheral-side zone Z1 while being folded at a plurality of turn-around points. The pair of terminals 22a and 22b are disposed in a region (within-shaft region) 20d of the rear surface 20b of the ceramic plate 20, the region locating within the tubular shaft 40. Power feeder rods 42a and 42b each made of a metal (for example, Ni) are bonded respectively to the pair of terminals 22a and 22b. The power feeder rods 42a and 42b are each inserted through an insulating tube (not illustrated).

[0052] As illustrated in FIG. 3, the outer-peripheral-side resistance heating element 24 is formed such that it starts from one of a pair of terminals 24a and 24b and reaches the other of the pair of terminals 24a and 24b after being wired in a one-stroke pattern over substantially the entirety of the outer-peripheral-side zone Z2 while being folded at a plurality of turn-around points. The pair of terminals 24a and 24b are disposed in the within-shaft region 20d of the rear surface 20b of the ceramic plate 20. Power feeder rods 44a and 44b each made of a metal (for example, Ni) are bonded respectively to the pair of terminals 24a and 24b. The power feeder rods 44a and 44b are each inserted through an insulating tube (not illustrated).

[0053] Inside the ceramic plate 20, as illustrated in FIG. 2, an elongate hole 26 into which an outer-peripheral-side thermocouple 50 is to be inserted is formed parallel to the wafer placement surface 20a. As illustrated in FIG. 3, the elongate hole 26 extends from a start point S in the within-shaft region 20d of the rear surface 20b of the ceramic plate 20 to a terminal end position E in an outer peripheral portion of the ceramic plate 20. The elongate hole 26 extends linearly from the start point S to the terminal end position E.

[0054] As illustrated in FIG. 4, the thermocouple guide 32 is a tubular member made of a metal (for example, stainless) and having a guide hole 32a. The thermocouple guide 32 includes a tip end portion 32b positioned at an upper end of the tubular shaft 40, a base end portion 32c positioned at a lower end of the tubular shaft 40, and a guide portion 32d disposed in a shape extending along an inner wall of the tubular shaft 40 over a region from the lower end of the tubular shaft 40 to the start point S. A curved portion 32e given as part of the guide portion 32d, the part extending up to a location just before the start point S, is curved to extend over about a ¼ circle in a circumferential direction (namely, to define part of a spiral) along the inner wall of the tubular shaft 40.

[0055] The outer-peripheral-side thermocouple 50 is inserted through the guide hole 32a. As illustrated in FIG. 3, the tip end portion 32b is arranged at the start point S of the elongate hole 26. The base end portion 32c is positioned below the lower end of the tubular shaft 40. The guide portion 32d guides the outer-peripheral-side thermocouple 50, having been inserted into the guide hole 32a, to be smoothly moved from the base end portion 32c to the tip end portion 32b of the thermocouple 50. The curved portion 32e is formed such that the tip end portion 32b gradually changes its direction to finally orient in a lengthwise direction of the elongate hole 26 while approaching the elongate hole 26. The thermocouple guide 32 may be formed of an electrically insulating material such as ceramic.

[0056] Inside the tubular shaft 40, as illustrated in FIG. 2, there are arranged the power feeder rods 42a and 42b connected respectively to the pair of terminals 22a and 22b of the inner-peripheral-side resistance heating element 22, and the power feeder rods 44a and 44b connected respectively to the pair of terminals 24a and 24b of the outer-peripheral-side resistance heating element 24. In addition, an inner-peripheral-side thermocouple 48 for measuring a temperature near the center of the ceramic plate 20 and the outer-peripheral-side thermocouple 50 for measuring a temperature near the outer periphery of the ceramic plate 20 are also arranged inside the tubular shaft 40. The inner-peripheral-side thermocouple 48 is inserted into a recess 49 formed in the rear surface 20b of the ceramic plate 20, and a temperature measurement portion 48a at a tip end of the inner-peripheral-side thermocouple 48 is held in contact with the ceramic plate 20. The recess 49 is formed at a position not interfering with the terminals 22a, 22b, 24a and 24b. The outer-peripheral-side thermocouple 50 is a sheathed thermocouple and is arranged to pass through the guide hole 32a of the thermocouple guide 32 and the elongate hole 26, and a temperature measurement portion 50a at a tip end of the thermocouple 50 reaches the terminal end position E of the elongate hole 26.

[0057] An example of manufacturing of the ceramic heater 10 will be described below. The power feeder rods 42a, 42b, 44a and 44b are bonded respectively to the terminals 22a, 22b, 24a and 24b that are exposed at the rear surface 20b of the ceramic plate 20, and the ceramic plate 20 and the tubular shaft 40 are bonded to each other. Then, the thermocouple guide 32 is inserted into the tubular shaft 40, and the tip end portion 32b is fixed to the start point S of the elongate hole 26. At that time, since the thermocouple guide 32 has the shape following the inner wall of the tubular shaft 40, the thermocouple guide 32 can be set inside the tubular shaft 40 without interfering with the power feeder rods 42a, 42b, 44a and 44b and the inner-peripheral-side thermocouple 48. Thereafter, the outer-peripheral-side thermocouple 50 is inserted through the guide hole 32a of the thermocouple guide 32 such that the temperature measurement portion 50a reaches the terminal end position E of the elongate hole 26.

[0058] An example of use of the ceramic heater 10 will be described below. First, the ceramic heater 10 is installed within a vacuum chamber (not illustrated), and the wafer W is placed on the wafer placement surface 20a of the ceramic heater 10. Then, electric power supplied to the inner-peripheral-side resistance heating element 22 is adjusted such that the temperature detected by the inner-peripheral-side thermocouple 48 is kept at a predetermined inner-peripheral-side target temperature. Furthermore, electric power supplied to the outer-peripheral-side resistance heating element 24 is adjusted such that the temperature detected by the outer-peripheral-side thermocouple 50 is kept at a predetermined outer-peripheral-side target temperature. Thus the temperature of the wafer W is controlled to be kept at a desired temperature. Thereafter, the interior of the vacuum chamber is evacuated to create a vacuum atmosphere or a pressure reduced atmosphere, plasma is generated inside the vacuum chamber, and CVD film formation or etching is performed on the wafer W by utilizing the generated plasma.

[0059] In the above-described ceramic heater 10 according to this embodiment, the part of the thermocouple guide 32 from the lower end of the tubular shaft 40 to the start point S of the elongate hole 26 is formed in the shape following the inner wall of the tubular shaft 40. Thus, with the thermocouple guide 32 and the outer-peripheral-side thermocouple 50 disposed along the inner wall of the tubular shaft 40, even when the terminals 22a, 22b, 24a and 24b (associated parts) are disposed near the center of the within-shaft region 20d and the power feeder rods 42a, 42b, 44a and 44b connected respectively to the terminals 22a, 22b, 24a and 24b are arranged in an inner space of the tubular shaft 40, those components are less likely to interfere with the thermocouple guide 32 and the outer-peripheral-side thermocouple 50. Accordingly, a degree of freedom in arrangement of the associated parts can be increased in the ceramic heater 10 that is a multi-zone heater.

[0060] Furthermore, with the ceramic heater 10 according to this embodiment, the curved portion 32e is curved toward the start point S of the elongate hole 26 in the shape defining part of a spiral along the inner wall of the tubular shaft 40, it is easier to dispose the thermocouple guide 32 and the outer-peripheral-side thermocouple 50 so as to follow the inner wall of the tubular shaft 40.

[0061] In addition, since the guide portion 32d of the thermocouple guide 32 is curved to gradually change its direction to finally orient in the lengthwise direction of the elongate hole 26 of the ceramic plate 20 while approaching the elongate hole 26, the outer-peripheral-side thermocouple 50 can easily be inserted into the elongate hole 26.

[0062] Note that it is apparent that the present invention is in no way limited to the embodiments described above, and the present invention can be carried out in a variety of ways within the technical scope of the present invention.

[0063] While, in the above-described embodiment, the elongate hole 26 extends linearly from the start point S to the terminal end position E, the present invention is not limited to such a case. For example, as illustrated in FIG. 5, the elongate hole 26 may be formed in a curved shape from the start point S to the terminal end position E. With this modification, when an obstacle, such as a through-hole, is present in the ceramic plate 20, the outer-peripheral-side thermocouple 50 can be arranged while avoiding the obstacle.

[0064] Furthermore, as illustrated in FIG. 6, a direction in which the elongate hole 26 is curved when viewing the ceramic heater 10 from a lower end side of the tubular shaft 40 may match with a direction in which the curved portion 32e is curved. In FIG. 6, when viewing the ceramic heater 10 from the lower end side of the tubular shaft 40, the curved portion 32e is curved to the right (clockwise) toward the start point S, and the elongate hole 26 is also curved to the right (clockwise) from the start point S toward the terminal end position E. If the curved portion 32e is curved to the left (counterclockwise) toward the start point S when viewing the ceramic heater 10 from the lower end side of the tubular shaft 40, the elongate hole 26 is also curved to the left (counterclockwise) from the start point S toward the terminal end position E. In this case, it is possible not only to, when an obstacle, such as a through-hole, is present in the ceramic plate 20, arrange the outer-peripheral-side thermocouple 50 while avoiding the obstacle, but also to smoothly insert the outer-peripheral-side thermocouple 50. Signs in FIGS. 5 and 6 are the same as those used in the above-described embodiment.

[0065] While, in the above-described embodiment, the curved portion 32e is formed to extend over about a ¼ circle in the circumferential direction along the inner wall of the tubular shaft 40, the present invention is not limited to such a case. For example, the curved portion 32e may be formed to extend over a ½ circle or one circle or more in the circumferential direction along the inner wall of the tubular shaft 40.

[0066] While, in the above-described embodiment, the resistance heating elements 22 and 24 are each in the form of a coil, the shape of the resistance heating element is not always limited to the coil. In another example, the resistance heating element may be a print pattern or may have a ribbon-like or mesh-like shape.

[0067] In the above-described embodiment, the temperature measurement portion 50a of the outer-peripheral-side thermocouple 50 in the elongate hole 26 may be arranged, as illustrated in FIG. 7, to position within a width of the outer-peripheral-side resistance heating element 24 (namely, a width w of the coil) when viewed from the rear surface 20b. When the outer-peripheral-side resistance heating element 24 has the ribbon-like shape (shape of an elongate flat plate) instead of the coil-like shape, the temperature measurement portion 50a may be arranged to position within a width of the ribbon. With such an arrangement, a temperature change of the outer-peripheral-side resistance heating element 24 can be detected by the temperature measurement portion 50a of the outer-peripheral-side thermocouple 50 with a good response.

[0068] In the above-described embodiment, the ceramic plate 20 may incorporate an electrostatic electrode and/or an RF electrode in addition to the resistance heating elements 22 and 24.

[0069] In the above-described embodiment, one or more annular regions may be formed between the inner-peripheral-side resistance heating element 22 and the outer-peripheral-side resistance heating element 24, and an additional resistance heating element may be arranged in each annular region.

[0070] While, in the above-described embodiment, the length of the thermocouple guide 32 in a vertical direction is almost equal to the height of the tubular shaft 40, it may be set shorter or longer than the height of the tubular shaft 40.

[0071] In the above-described embodiment, the inner-peripheral-side zone Z1 may be divided into a plurality of inner-peripheral-side small zones, and the resistance heating element may be wired in a one-stroke pattern for each of the inner-peripheral-side small zones. Furthermore, the outer-peripheral-side zone Z2 may be divided into a plurality of outer-peripheral-side small zones, and the resistance heating element may be wired in a one-stroke pattern for each of the outer-peripheral-side small zones. Although the number of terminals increases depending on the number of small zones, the terminals do not interfere with the thermocouple guide 32. Accordingly, despite an increase in the number of terminals, the terminals can be relatively easily arranged near the center of the within-shaft region 20d.

[0072] The above embodiment has been described, by way of example, in connection with the assembly procedure of bonding the power feeder rods 42a, 42b, 44a and 44b to the terminals 22a, 22b, 24a and 24b of the ceramic plate 20, respectively, bonding the tubular shaft 40 to the rear surface 20b of the ceramic plate 20, and then attaching the thermocouple guide 32. However, the assembly procedure is not limited to such a case. For example, the power feeder rods 42a, 42b, 44a and 44b may be bonded to the terminals 22a, 22b, 24a and 24b of the ceramic plate 20, respectively, after bonding the tubular shaft 40 to the rear surface 20b of the ceramic plate 20 and attaching the thermocouple guide 32. Alternatively, the thermocouple guide 32 may be fixed to the start point S of the elongate hole 26 in advance, and the tubular shaft 40 may be bonded to the rear surface 20b of the ceramic plate 20 after bonding the power feeder rods 42a, 42b, 44a and 44b to the terminals 22a, 22b, 24a and 24b of the ceramic plate 20, respectively.

[0073] In the above-described embodiment, the thermocouple guide 32 remains placed inside the tubular shaft 40 even after the outer-peripheral-side thermocouple 50 has been inserted through the guide hole 32a of the thermocouple guide 32 and the temperature measurement portion 50a has reached the terminal end position E of the elongate hole 26.

[0074] However, the present invention is not limited to such a case. For example, the thermocouple guide 32 may be removed after inserting the outer-peripheral-side thermocouple 50 through the guide hole 32a of the thermocouple guide 32.

[0075] The application claims priority to Japanese Patent Application No. 2020-016113 filed in the Japan Patent Office on Feb. 3, 2020, the entire contents of which are incorporated herein by reference.