Ceramic Heater

Abstract

The ceramic heater includes a ceramic plate 20 having a wafer mounting surface on its upper surface, a plurality of zones Z1 to Z6 provided on the wafer mounting surface, zone heaters embedded in the ceramic plate 20 corresponding to each of the plurality of zones Z1 to Z6, a single temperature measuring member passage 30 provided in the ceramic plate 20, and a single temperature measuring member (multi-TC 40) disposed in the temperature measuring member passage 30. The temperature measuring member passage 30 is provided so as to pass through each of the plurality of zones Z1 to Z6 from an inlet 32 ​​provided on the lower surface of the ceramic plate 20. The multi-TC 40 has a plurality of temperature measuring units 41m to 46m. The plurality of temperature measuring units 41m to 46m are disposed at measurement positions P1 to P6 corresponding to each of the plurality of zones Z1 to Z6.

Description

[Technical field]

[0001] The present invention relates to a ceramic heater. [Background technology]

[0002] In semiconductor manufacturing equipment, ceramic heaters are used to heat wafers. As such ceramic heaters, so-called multi-zone heaters are known. As disclosed in Patent Document 1, this type of multi-zone heater includes a ceramic plate having heating elements capable of partially heating each of a plurality of zones, and temperature sensors disposed in close proximity to each of the heating elements. The temperature sensors transmit temperature feedback information to an external controller. The controller uses the temperature feedback information to control the power applied to the heating elements of each zone. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-55790 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the multi-zone heater of Patent Document 1, it is necessary to provide a plurality of holes in the ceramic plate in order to pass the wiring of each of the plurality of temperature sensors.

[0005] The present invention has been made to solve such problems, and has as its main object to simplify the structure of the ceramic plate in a ceramic heater capable of measuring the temperature of each of a plurality of zones. [Means for solving the problem]

[0006] [1] The ceramic heater of the present invention is a ceramic plate having a wafer mounting surface on an upper surface thereof; A plurality of zones provided on the wafer mounting surface; a zone heater embedded in the ceramic plate corresponding to each of the plurality of zones; A single temperature measuring member passage provided in the ceramic plate; A single temperature measuring member disposed in the temperature measuring member passage; Equipped with the temperature measuring member passage is provided from an inlet provided on the lower surface of the ceramic plate to pass through each of the plurality of zones; The temperature measuring member has a plurality of temperature measuring parts, and the plurality of temperature measuring parts are arranged at measurement positions corresponding to the plurality of zones, respectively. It is something.

[0007] In the ceramic heater of the present invention, the temperature measuring member passage is provided so as to pass through each of the multiple zones from an inlet provided on the underside of the ceramic plate. Also, a single temperature measuring member has multiple temperature measuring parts, and the multiple temperature measuring parts are arranged at measurement positions corresponding to each of the multiple zones. Therefore, it is not necessary to provide holes in the ceramic plate 20 corresponding to each of the multiple temperature sensors as in the conventional case, and the structure of the ceramic plate 20 can be simplified.

[0008] [2] The ceramic heater of the present invention (the ceramic heater described in [1] above) may further comprise a hollow shaft provided on the underside of the ceramic plate, and an inner-shaft region on the underside of the ceramic plate surrounded by the hollow shaft, and the inlet of the temperature measuring member passage may be provided in the inner-shaft region. In a ceramic heater with a hollow shaft, various components (such as power supply members for each zone heater) are arranged in the relatively narrow inner-shaft region on the underside of the ceramic plate, but since there is no need to provide holes in the inner-shaft region corresponding to each of the numerous temperature sensors, the inner-shaft region can be used effectively.

[0009] [3] In the ceramic heater of the present invention (the ceramic heater described in [1] or [2] above), the temperature measuring member passage may be curved. In this way, when inserting the temperature measuring member into the temperature measuring member passage, the temperature measuring member can be inserted smoothly because the temperature measuring member passage is curved.

[0010] [4] In the ceramic heater of the present invention (the ceramic heater according to any one of [1] to [3] above), the multiple zones may have a circular center zone smaller than the diameter of the ceramic plate, and a plurality of divided outer zones obtained by dividing the outermost outer zone into a ring shape having an outer diameter equal to the diameter of the ceramic plate and an inner diameter equal to or larger than the diameter of the center zone, and the temperature measuring member passage may be provided in a spiral shape so that it passes from the inlet through a measurement position corresponding to the center zone and then passes through each measurement position of the multiple divided outer zones in sequence. In this way, since the shape of the temperature measuring member passage is spiral rather than serpentine, the length of the temperature measuring member passage can be made relatively short.

[0011] [5] In the ceramic heater of the present invention (the ceramic heater according to any one of [1] to [4] above), the temperature measuring member may be a single flexible protective tube containing a plurality of thermocouples of different lengths, the temperature measuring section may be provided at the tip of the thermocouple, and the wires connected to each of the plurality of thermocouples may be gathered into a single wiring assembly at the end of the temperature measuring member. In this way, each temperature measuring section of the temperature measuring member can be easily connected to an external device via the wiring assembly.

[0012] [6] In the ceramic heater of the present invention (the ceramic heater according to any one of the above [1] to [5]), the width and height of the temperature measuring member passage may be 1.5 mm to 3.0 mm. [Brief description of the drawings]

[0013] [Figure 1] FIG. [Diagram 2] Cross section AA of Figure 1. [Diagram 3] 4 is a cross-sectional view of the ceramic plate 20 cut horizontally along the surface on which the center zone heater is formed and viewed from above. FIG. [Figure 4] 3 is a cross-sectional view of the ceramic plate 20 cut horizontally along the temperature measuring member passage 30 and viewed from above. FIG. [Diagram 5] Front view of Multi TC40. [Figure 6] Cross-sectional view taken along line B-B in FIG. 5 . [Figure 7] FIG. 2 is a block diagram showing the connection relationship between a controller 80 and a ceramic heater 10. 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 ceramic heater 10, Fig. 2 is a cross-sectional view taken along the line AA in Fig. 1, Fig. 3 is a cross-sectional view of a ceramic plate 20 cut horizontally along the surface where the center zone heater is formed and viewed from above, Fig. 4 is a cross-sectional view of a ceramic plate 20 cut horizontally along the temperature measuring member passage 30 and viewed from above, Fig. 5 is a front view of a multi-TC 40, Fig. 6 is a cross-sectional view taken along the line BB in Fig. 5, and Fig. 7 is a block diagram showing the connection relationship between a controller 80 and a ceramic heater 10. In Fig. 2, the jumpers 22c, 22d, 25c, and 26c are shown by solid lines for the sake of convenience. In Fig. 3, the hatching representing the cut surface is omitted and a cross section of a cylindrical shaft 50 is shown for the sake of convenience.

[0015] The ceramic heater 10 is used to heat a wafer undergoing processing such as etching or CVD, and is installed in a vacuum chamber (not shown). The ceramic heater 10 includes a disk-shaped ceramic plate 20 having a wafer mounting surface 20a on its upper surface, and a hollow cylindrical shaft 50 joined to the surface (lower surface) 20b of the ceramic plate 20 opposite the wafer mounting surface 20a.

[0016] The ceramic plate 20 is a disk-shaped plate made of ceramics such as aluminum nitride or alumina. The wafer mounting surface 20a of the ceramic plate 20 is divided into a circular center zone Z1, an annular middle zone Z2, and an annular outer zone on the outermost periphery by two imaginary circles concentric with the ceramic plate 20 but with different diameters. The outer zone is divided into four fan-shaped zones (first to fourth divided outer zones Z3 to Z6) by four radial line segments of the ceramic plate 20.

[0017] Zone heaters are embedded in the ceramic plate 20 corresponding to each of the multiple zones Z1 to Z6. Specifically, as shown in FIG. 3, a center zone heater 21 is embedded in the ceramic plate 20 corresponding to the center zone Z1, a middle zone heater 22 is embedded in the ceramic plate 20 corresponding to the middle zone Z2, a first divided outer zone heater 23 is embedded in the ceramic plate 20 corresponding to the first divided outer zone Z3, a second divided outer zone heater 24 is embedded in the ceramic plate 20 corresponding to the second divided outer zone Z4, a third divided outer zone heater 25 is embedded in the ceramic plate 20 corresponding to the third divided outer zone Z5, and a fourth divided outer zone heater 26 is embedded in the ceramic plate 20 corresponding to the fourth divided outer zone Z6. These heaters 21 to 26 are composed of resistance heating elements that generate heat when a current is passed through them. Examples of the resistance heating elements include coils, printed electrodes, and ribbons whose main components are molybdenum, tungsten, or tungsten carbide.

[0018] The center zone heater 21 is provided on a center zone heater forming surface (a surface parallel to the wafer mounting surface 20a) inside the ceramic plate 20. The center zone heater 21 is formed so as to be wired from a terminal 21a provided near the center of the ceramic plate 20 in a single stroke across almost the entire area of ​​the center zone Z1, and then to a terminal 21b.

[0019] The middle zone heater 22 is provided on a middle zone heater forming surface (a surface parallel to the wafer mounting surface 20a) different from the center zone heater forming surface. The middle zone heater 22 is wired in a single line across almost the entire area of ​​the middle zone Z2. Both ends of the middle zone heater 22 are connected to jumpers 22c and 22d provided on the middle zone heater forming surface. The jumpers 22c and 22d are connected to terminals 22a and 22b provided near the center of the ceramic plate 20.

[0020] The first to fourth divided outer zone heaters 23-26 are provided on an outer zone heater forming surface (parallel to the wafer mounting surface 20a) different from the center zone heater forming surface and the middle zone heater forming surface. The first divided outer zone heater 23 is wired in a single stroke over almost the entire area of ​​the first divided outer zone Z3. Both ends of the first divided outer zone heater 23 are connected to jumpers 23c and 23d provided on the outer zone heater forming surface. The jumpers 23c and 23d are connected to terminals 23a and 23b provided near the center of the ceramic plate 20.

[0021] The second divided outer zone heater 24 is wired in a single line across almost the entire area of ​​the second divided outer zone Z4. Both ends of the second divided outer zone heater 24 are connected to jumpers 24c and 24d provided on the outer zone heater forming surface. The jumpers 24c and 24d are connected to terminals 24a and 24b provided near the center of the ceramic plate 20.

[0022] The third divided outer zone heater 25 is wired in a single line across almost the entire area of ​​the third divided outer zone Z5. Both ends of the third divided outer zone heater 25 are connected to jumpers 25c and 25d provided on the outer zone heater forming surface. The jumpers 25c and 25d are connected to terminals 25a and 25b provided near the center of the ceramic plate 20.

[0023] The fourth divided outer zone heater 26 is wired in a single line across almost the entire area of ​​the fourth divided outer zone Z6. Both ends of the fourth divided outer zone heater 26 are connected to jumpers 26c and 26d provided on the outer zone heater forming surface. The jumpers 26c and 26d are connected to terminals 26a and 26b provided near the center of the ceramic plate 20.

[0024] As shown in FIG. 4, inside the ceramic plate 20, a single temperature measuring member passage 30 is provided in a plane parallel to the wafer mounting surface 20a (for example, a plane below the heater formation surface). The temperature measuring member passage 30 is provided so as to pass through each of the multiple zones Z1 to Z6 from an inlet 32 ​​extending in the vertical direction formed in the shaft inner region 20c (see FIG. 2) surrounded by the cylindrical shaft 50 on the lower surface 20b of the ceramic plate 20. The inlet 32 ​​is provided so as to curve from the vertical direction to the horizontal direction. Specifically, the temperature measuring member passage 30 passes from the inlet 32 ​​through the center zone Z1, the middle zone Z2, the first divided outer zone Z3, the second divided outer zone Z4, the third divided outer zone Z5, and the fourth divided outer zone Z6 in this order. The width of the temperature measuring member passage 30 is, for example, 1.5 to 3.0 mm in the direction parallel to the wafer mounting surface 20a. The height of the temperature measurement member passage 30 is, for example, 1.5 to 3.0 mm in a direction perpendicular to the wafer mounting surface 20a. The temperature measurement member passage 30 is formed in a spiral shape (a type of curved shape) along the horizontal direction. The temperature measurement member passage 30 is provided with measurement positions P1 to P6 corresponding to the multiple zones Z1 to Z6, respectively. In Fig. 4, the measurement positions P1 to P6 are indicated by dotted star shapes.

[0025] In the temperature measuring member passage 30, a multi-TC 40 is disposed as a single temperature measuring member. TC stands for thermocouple. The multi-TC 40 has a plurality of temperature measuring parts 41m to 46m. As shown in Figs. 5 and 6, the multi-TC 40 includes a plurality of sheaths TC41 to 46 of different lengths inside a single flexible protective tube 47. The material of the protective tube 47 is, for example, a metal (such as SUS316), the thickness of the protective tube 47 is, for example, 0.1 to 0.3 mm, and the tube diameter of the protective tube 47 is, for example, about 1.0 mm. The material of the sheaths in the sheaths TC41 to 46 is, for example, a metal (such as SUS316), and the thickness of the sheath is, for example, 0.1 to 0.3 mm. The inside of the sheath is filled with an insulating material (such as MgO), and the TC main body is embedded therein. The inside of the protective tube 47 is not filled with an insulating material. The temperature measuring units 41m-46m are the tips of the sheaths TC41-46 (the tips of the TC main bodies in the sheaths TC41-46). The ends of the sheaths TC41-46 are fixed to a sleeve 48 provided at the end of a protective tube 47. The wires connected to each of the multiple sheaths TC41-46 are bundled into a flat cable 49, which is a wire assembly attached to the sleeve 48. The sleeve 48 is placed on a support stand 60 attached to the lower end of a cylindrical shaft 50 as shown in FIG. 2.

[0026] The multi-TC 40 inserts the protective tube 47 from the inlet 32 ​​of the ceramic plate 20 into the temperature measuring member passage 30, and when the tip of the protective tube 47 reaches the end of the temperature measuring member passage 30, the temperature measuring parts 41m to 46m of the six sheaths TC41 to 46 built into the protective tube 47 of the multi-TC 40 are each positioned at a predetermined measurement position. Specifically, the temperature measuring part 41m of the sheath TC41 is positioned at a measurement position P1 corresponding to the center zone Z1. The temperature measuring part 42m of the sheath TC42 is positioned at a measurement position P2 corresponding to the middle zone Z2. The temperature measuring part 43m of the sheath TC43 is positioned at a measurement position P3 corresponding to the first divided outer zone Z3. The temperature measuring part 44m of the sheath TC44 is positioned at a measurement position P4 corresponding to the second divided outer zone Z4. The temperature measuring part 45m of the sheath TC45 is positioned at a measurement position P5 corresponding to the third divided outer zone Z5. The temperature measuring portion 46m of the sheath TC46 is disposed at a measurement position P6 corresponding to the fourth divided outer zone Z6.

[0027] The cylindrical shaft 50 is formed of ceramics such as aluminum nitride and alumina, like the ceramic plate 20. As shown in Fig. 2, the upper end of the cylindrical shaft 50 is joined to the ceramic plate 20, and the lower end is airtightly connected to a support base 60 via an O-ring 62. Inside the cylindrical shaft 50, there are arranged power feed rods 51a and 51b connected to the pair of terminals 21a and 21b of the center zone heater 21, power feed rods connected to the pair of terminals 22a and 22b of the middle zone heater 22, power feed rods connected to the pair of terminals 23a and 23b of the first divided outer zone heater 23, power feed rods connected to the pair of terminals 24a and 24b of the second divided outer zone heater 24, power feed rods connected to the pair of terminals 25a and 25b of the third divided outer zone heater 25, and power feed rods connected to the pair of terminals 26a and 26b of the fourth divided outer zone heater 26. These power supply rods pass through the support base 60 in the vertical direction. The multi-TC 40 is also disposed inside the cylindrical shaft 50. The multi-TC 40 has a sleeve 48 supported by the support base 60. A protective tube 47 and a plurality of sheaths TC41 to 46extends vertically inside the cylindrical shaft 50, but extends horizontally inside the temperature measuring member passage 30.

[0028] As shown in Fig. 7, the controller 80 is configured as a microprocessor centered on a CPU, and includes a memory for storing various processing programs and various data. The controller 80 is connected to the flat cable 49 (i.e., the signal lines of the sheaths TCs 41-46) of the multi-TC 40, and can input temperature signals from these. The controller 80 is connected to a center zone power supply 81 connected to the center zone heater 21, a middle zone power supply 82 connected to the middle zone heater 22, and first to fourth divided outer zone power supplies 83-86 connected to the first to fourth divided outer zone heaters 23-26, and can output control signals to these. The controller 80 performs feedback control by inputting the temperature signals of the sheaths TCs 41-46 and outputting control signals to the power supplies 81-86 so that the temperatures of the zones Z1-Z6 become preset target temperatures.

[0029] Next, an example of using the ceramic heater 10 will be described. First, the ceramic heater 10 is installed in a vacuum chamber (not shown), and a wafer is placed on the wafer placement surface 20a of the ceramic heater 10. Then, the zone power supplies 81-86 are controlled so that the temperatures detected by the sheaths TC41-46 become the predetermined target temperatures of the respective zones. This controls the temperature of the wafer to a desired temperature. Then, the inside of the vacuum chamber is set to a vacuum atmosphere or a reduced pressure atmosphere, plasma is generated in the vacuum chamber, and the plasma is used to perform CVD film formation or etching on the wafer.

[0030] In the ceramic heater 10 of the present embodiment described above, the temperature measuring member passage 30 is provided so as to pass through each of the multiple zones Z1 to Z6 from the inlet 32 ​​provided on the lower surface of the ceramic plate 20. Also, the multi-TC 40 as a single temperature measuring member has multiple temperature measuring parts 41m to 46m, and the multiple temperature measuring parts 41m to 46m are arranged at measurement positions P1 to P6 corresponding to the multiple zones Z1 to Z6, respectively. Therefore, it is not necessary to provide holes corresponding to each of the multiple temperature sensors in the ceramic plate 20 as in the conventional case, and the configuration of the ceramic plate 20 can be simplified.

[0031] Furthermore, in the ceramic heater 10 having a hollow cylindrical shaft 50, various components (e.g., power supply members for each zone heater 21-26 and the multi-TC 40) are arranged in a relatively narrow inner-shaft region 20c on the underside of the ceramic plate 20, but since there is no need to provide holes in the inner-shaft region 20c corresponding to each of the numerous temperature sensors, the inner-shaft region 20c can be used effectively.

[0032] Furthermore, the temperature measuring member passage 30 is provided in a curved shape. Therefore, the multi-TC 40 can be smoothly inserted into the temperature measuring member passage 30.

[0033] Furthermore, the multiple zones Z1 to Z6 include a circular center zone Z1 that is smaller than the diameter of the ceramic plate 20, a middle zone Z2 having an annular shape provided outside the center zone Z1; The outer diameter is the same as the diameter of the ceramic plate 20, and the inner diameter is larger than the diameter of the center zone Z1. (Here the inner diameter is the same as the outer diameter of the middle zone Z2) The annular region is divided into multiple regions, 4 Divided outer zone and Z 3~ Z The temperature measuring member passage 30 has an inlet 32, a central zone Z1, and a Go through the middle zone Z2, Multiple 1st to 5th 4 The temperature measuring member passage 30 is provided in a spiral shape so as to pass through each of the divided outer zones Z3 to Z6 in sequence. Since the temperature measuring member passage 30 has a spiral shape rather than a meandering shape, the length of the temperature measuring member passage 30 can be made relatively short.

[0034] Furthermore, the multi-TC 40 includes a plurality of sheaths TC41-46 of different lengths inside a single flexible protective tube 47, and temperature measuring units 41m-46m are provided at the tips of the sheaths TC41-46. Wiring connected to each of the plurality of sheaths TC41-46 is collected into a single flat cable 49 at the end of the multi-TC 40. Therefore, each of the temperature measuring units 41m-46m of the multi-TC 40 can be easily connected to an external device (controller 80) via the flat cable 49.

[0035] 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.

[0036] For example, in the above-described embodiment, six zones, namely, a center zone Z1, a middle zone Z2, and first to fourth divided outer zones Z3 to Z6, are provided on the wafer mounting surface 20a, but the shape of the zones is not limited thereto, and the number of zones may be two or more. For example, the wafer mounting surface 20a may be divided into two or more zones (a circular zone and one or more annular zones) by circles of different diameters concentric with the ceramic plate 20. Alternatively, the wafer mounting surface 20a of the ceramic plate 20 may be divided into two or more zones by radial lines.

[0037] In the above-described embodiment, the multiple zone heaters (center zone heater 21, middle zone heater 22, and first to fourth divided outer zone heaters 23-26) embedded in the ceramic plate 20 are formed on heater forming surfaces at different heights from the wafer mounting surface 20a, but this is not particularly limited. For example, the multiple zone heaters may be formed on heater forming surfaces at the same height from the wafer mounting surface 20a, or some of the zone heaters may be formed on heater forming surfaces at the same height and the rest may be formed on heater forming surfaces at different heights.

[0038] In the above embodiment, the jumpers 22c and 22d that connect the middle zone heater 22 to the terminals 22a and 22b are provided on the middle zone heater forming surface, but this is not particularly limited. For example, the heater forming surface and the jumper forming surface may be different surfaces. This also applies to the jumpers 23c, 23d, 24c, 24d, 25c, 25d, 26c, and 26d.

[0039] In the above embodiment, the longest sheath TC46 is arranged along the central axis of the protective tube 47, and the other sheaths TC41 to 45 are arranged around it as the multi-TC 40. However, the present invention is not limited to this. For example, the sheaths TC41 to 46 may be arranged randomly inside the protective tube 47.

[0040] In the above-described embodiment, an electrostatic electrode may be built into the ceramic plate 20. In this case, after placing a wafer on the wafer mounting surface 20a, a voltage is applied to the electrostatic electrode, so that the wafer can be electrostatically attracted to the wafer mounting surface 20a. Alternatively, an RF electrode may be built into the ceramic plate 20. In this case, a shower head (not shown) is disposed above the wafer mounting surface 20a with a space therebetween, and high-frequency power is supplied between parallel plate electrodes consisting of the shower head and the RF electrode. In this way, plasma is generated, and the plasma can be used to perform CVD film formation or etching on the wafer. The electrostatic electrode may also serve as the RF electrode. [Industrial Applicability]

[0041] The present invention can be used in semiconductor manufacturing equipment that processes wafers. [Explanation of symbols]

[0042] 10 ceramic heater, 20 ceramic plate, 20a wafer mounting surface, 20b lower surface, 20c shaft inner area, 21 center zone heater, 22 middle zone heater, 23-26 first to fourth divided outer zone heaters, 21a, 21b, 22a, 22b, 23a, 23b, 24a, 24b, 25a, 25b, 26a, 26b terminals, 22c, 22d, 23c, 23d, 24c, 24d, 25c, 25d, 26c, 26d jumper, 30 temperature measuring member passage, 32 inlet, 40 multi-TC, 41-46 sheath TC, 41m-46m temperature measuring section, 47 protective tube, 48 sleeve, 49 flat cable, 50 cylindrical shaft, 51a, 52b power supply rod, 60 Support stand, 62 O-ring, 80 controller, 81 center zone power supply, 82 middle zone power supply, 83 to 86 first to fourth divided outer zone power supplies, P1 to P6 measurement positions, Z1 center zone, Z2 middle zone, Z3 to Z6 first to fourth divided outer zones.

Claims

1. a ceramic plate having a wafer mounting surface on an upper surface thereof; A plurality of zones provided on the wafer mounting surface; a zone heater embedded in the ceramic plate corresponding to each of the plurality of zones; A single temperature measuring member passage provided in the ceramic plate; A single temperature measuring member disposed in the temperature measuring member passage; Equipped with the temperature measuring member passage is provided from an inlet provided on the lower surface of the ceramic plate to pass through each of the plurality of zones; The temperature measuring member has a plurality of temperature measuring parts, and the plurality of temperature measuring parts are arranged at measurement positions corresponding to the plurality of zones, respectively; The temperature measuring member is a single flexible protective tube having a plurality of thermocouples of different lengths provided therein, the temperature measuring section is provided at the tip of the thermocouple, and the wiring connected to each of the plurality of thermocouples is gathered into one wiring assembly at the end of the temperature measuring member. Ceramic heater.

2. 2. The ceramic heater according to claim 1, a hollow shaft provided on the lower surface of the ceramic plate; a shaft inner region of a lower surface of the ceramic plate that is surrounded by the hollow shaft; Equipped with The inlet of the temperature measuring member passage is provided in the shaft inner area. Ceramic heater.

3. The temperature measuring member passage is provided in a curved shape.

3. The ceramic heater according to claim 1 or 2.

4. the plurality of zones include a circular center zone smaller than a diameter of the ceramic plate, and a plurality of divided outer zones obtained by dividing the outermost outer zone, the outer diameter of which is the same as the diameter of the ceramic plate and the inner diameter of which is the same as or larger than the diameter of the center zone; the temperature measuring member passage is provided in a spiral shape so as to pass from the inlet through a measurement position corresponding to the center zone and then pass through respective measurement positions of the plurality of divided outer zones in sequence; 3. The ceramic heater according to claim 1 or 2.

5. The width and height of the temperature measuring member passage are 1.5 mm to 3.0 mm; 3. The ceramic heater according to claim 1 or 2.

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