Ceramic heater

Abstract

A ceramic heater 10 comprises: a ceramic plate 20 having a wafer mounting surface 21 on the upper surface 20a thereof; inner peripheral side and outer peripheral side resistance heating elements 25, 26 that are buried in the ceramic plate 20 and wired in zones Z1, Z2 obtained by dividing the wafer mounting surface 21 into two; a cylindrical shaft 40 supporting the ceramic plate 20 from the lower surface 20b thereof; a thermocouple insertion hole 30 provided in a shaft inner region 27 of the lower surface 20b of the ceramic plate 20; and four resistance heating element terminal holes provided in the shaft inner region 27 so as to respectively correspond to terminals 25a, 25b, 26a, 26b of the inner peripheral side and outer peripheral side resistance heating elements 25, 26. The inner peripheral side resistance heating element 25 is located above the bottom surface 31 of the thermocouple insertion hole 30, and has a portion overlapping the thermocouple insertion hole 30 in plan view.

Description

Ceramic heater

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

[0002] Conventionally, a ceramic heater has been known that includes a ceramic plate having a wafer mounting surface on its upper surface, two resistance heating elements wired for each zone that divides the wafer mounting surface, and a cylindrical shaft that supports the ceramic plate from its underside. For example, Patent Document 1 discloses such a ceramic heater that has a thermocouple insertion hole and four terminal holes in the interior area of ​​the shaft. The thermocouple insertion hole is a hole for inserting a thermocouple that measures the temperature of the center of the ceramic plate. Each resistance heating element is located above the bottom of the thermocouple insertion hole. The four terminal holes are holes for inserting power feed rods that supply power to each resistance heating element, and are provided corresponding to the terminals of the two resistance heating elements.

[0003] Japanese Patent Application Laid-Open No. 2021-125308

[0004] However, in Patent Document 1, because neither of the two resistance heating elements overlaps with the thermocouple insertion hole in a plan view, there is a problem that cool spots tend to occur directly above the thermocouple insertion hole on the wafer mounting surface, which is undesirable because it can deteriorate the temperature uniformity of the wafer mounting surface.

[0005] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to improve the temperature uniformity of the wafer mounting surface.

[0006] [1] A ceramic heater of the present invention comprises: a ceramic plate having a wafer mounting surface on its upper surface; two or more resistance heating elements embedded in the ceramic plate and wired for each of two or more zones obtained by dividing the wafer mounting surface into two or more zones; a cylindrical shaft supporting the ceramic plate from its underside; a thermocouple insertion hole provided in an inner shaft region of the underside of the ceramic plate that is surrounded by the cylindrical shaft; and four or more resistance heating element terminal holes provided in the inner shaft region and corresponding to both end portions of the two or more resistance heating elements, wherein at least one resistance heating element of the two or more resistance heating elements is located above the bottom surface of the thermocouple insertion hole and has a portion that overlaps with the thermocouple insertion hole in a plan view.

[0007] In this ceramic heater, at least one of the two or more resistance heating elements is located above the bottom surface of the thermocouple insertion hole and has a portion that overlaps with the thermocouple insertion hole in a plan view. In other words, at least one resistance heating element is wired directly above the bottom surface of the thermocouple insertion hole. This makes it less likely that a cool spot will occur on the wafer mounting surface directly above the thermocouple insertion hole. This results in good temperature uniformity on the wafer mounting surface.

[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 ceramic heater, "upper" and "lower" may become "lower" and "upper," "left" and "right," or "front" and "rear."

[0009] [2] In the ceramic heater of the present invention (the ceramic heater described in [1] above), it is preferable that the ratio of the depth of the thermocouple insertion hole to the thickness of the ceramic plate from the wafer mounting surface to the underside be 0.055 or more and 0.4 or less. This improves the temperature uniformity of the wafer mounting surface.

[0010] [3] In the ceramic heater of the present invention (the ceramic heater according to [1] or [2] above), the thermocouple insertion hole may be surrounded by the four or more resistance heating element terminal holes in a plan view. This allows the spacing between the resistance heating element terminal holes to be relatively wide.

[0011] [4] In the ceramic heater of the present invention (the ceramic heater according to any one of [1] to [3] above), the depth of the thermocouple insertion hole is preferably 1 mm or more. This increases the reliability of the temperature measurement results obtained by the thermocouple.

[0012] [5] In the ceramic heater of the present invention (the ceramic heater according to any one of [1] to [4] above), the inner diameter of the cylindrical shaft is preferably 52 mm or less. In this case, the area of ​​the inner shaft region is small, making it difficult to wire a resistance heating element around the thermocouple insertion hole, and therefore, applying the present invention is highly significant.

[0013] [6] In the ceramic heater of the present invention (the ceramic heater according to any one of [1] to [5] above), the ceramic plate may be an AlN plate. Since AlN has a higher thermal conductivity than alumina, the temperature of the wafer mounting surface tends to be uniform.

[0014] [7] In the ceramic heater of the present invention (the ceramic heater according to any one of [1] to [6] above), the ceramic plate may incorporate a functional electrode separate from the resistance heating element, the shaft inner region may be provided with electrode terminal holes corresponding to the functional electrodes, and the thermocouple insertion hole may be surrounded by the four or more resistance heating element terminal holes and the electrode terminal holes in plan view. In this case, the free space in the shaft inner region becomes small, making it difficult to wire the resistance heating element around the thermocouple insertion hole, and therefore application of the present invention is highly significant.

[0015] A perspective view of the ceramic heater 10. An AA cross-sectional view of FIG. 1. A partially enlarged view of FIG. 2. A BB cross-sectional view of FIG. 1. A partial plan view of the wafer mounting surface 21 of the ceramic heater 10. A longitudinal cross-sectional view of the ceramic heater 110. A partial plan view of the wafer mounting surface 21 of the ceramic heater 110. A partial plan view of the wafer mounting surface 21 of another example.

[0016] 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 line A-A in Fig. 1, Fig. 3 is an enlarged view of a portion of Fig. 2, Fig. 4 is a cross-sectional view taken along line B-B in Fig. 1, and Fig. 5 is a partial plan view of the wafer mounting surface 21 of the ceramic heater 10 (a plan view of the central portion of the wafer mounting surface 21). Note that while the terminals 24a, 25a, 25b, 26a, and 26b are shown in the correct positions in Figs. 4 and 5, they are shown shifted in the left-right direction in Figs. 2 and 3 for convenience.

[0017] The ceramic heater 10 is used to heat a wafer W undergoing processing such as etching or CVD, and is installed in a vacuum chamber (not shown). The ceramic heater 10 includes a ceramic plate 20 having a wafer mounting surface 21 on an upper surface 20a, and a cylindrical shaft 40 joined to a lower surface 20b of the ceramic plate 20.

[0018] The ceramic plate 20 is a disk-shaped plate made of a ceramic material such as aluminum nitride or alumina. The diameter of the ceramic plate 20 is not particularly limited, but is, for example, 300 to 400 mm. The upper surface 20a of the ceramic plate 20 is provided with a circular wafer mounting surface 21, an annular surface 22 that surrounds the wafer mounting surface 21 and is one step higher than the wafer mounting surface 21, and a bank 23 that is an inclined surface between the wafer mounting surface 21 and the annular surface 22. As shown in FIG. 2 , the lower surface 20b of the ceramic plate 20 is provided with a circular shaft inner region 27 surrounded by the cylindrical shaft 40 and an annular reference surface 28 that surrounds the shaft inner region 27. The shaft inner region 27 protrudes downward from the reference surface 28.

[0019] An RF electrode 24, an inner-circumferential resistance heating element 25, and an outer-circumferential resistance heating element 26 are embedded in the ceramic plate 20. The inner-circumferential resistance heating element 25 and the outer-circumferential resistance heating element 26 are embedded below the RF electrode 24 and on approximately the same plane. The ceramic plate 20 is divided into a small circular inner-circumferential zone Z1 and an annular outer-circumferential zone Z2 by an imaginary boundary BL (see FIG. 4) concentric with the ceramic plate 20. The inner-circumferential resistance heating element 25 is embedded in the inner-circumferential zone Z1 of the ceramic plate 20, and the outer-circumferential resistance heating element 26 is embedded in the outer-circumferential zone Z2. The resistance heating elements 25, 26 may be shaped, for example, as a coil, mesh, foil, ribbon (wire), or the like. The resistance heating elements 25, 26 may be formed by printing. The materials for both resistance heating elements 25 and 26 include, for example, Mo, W, Mo / W alloy, Nb, WC-TiN, and WC-Al2O3.

[0020] The cylindrical shaft 40 is made of a ceramic material such as aluminum nitride or alumina, like the ceramic plate 20. The outer diameter of the cylindrical shaft 40 is smaller than the diameter of the ceramic plate 20. The upper end of the cylindrical shaft 40 is diffusion-bonded to the ceramic plate 20. A flange may be provided at the upper end of the cylindrical shaft 40.

[0021] The RF electrode 24 is a circular electrode used to generate plasma above the wafer mounting surface 21 and is formed of, for example, a metal mesh. The diameter of the RF electrode 24 is smaller than the diameter of the ceramic plate 20. As shown in FIGS. 2 and 3 , the RF electrode 24 is provided with an RF electrode terminal 24a. As shown in FIG. 3 , the RF electrode terminal 24a is exposed to the outside through an electrode terminal hole 24c formed in the shaft inner region 27. The RF electrode terminal 24a is joined to a rod-shaped RF rod 44 inserted into the electrode terminal hole 24c. Examples of materials for the RF electrode 24 include Mo, W, MoC, and WC. The RF electrode 24 is an example of a functional electrode of the present invention.

[0022] As shown in Fig. 4, the inner circumference-side resistance heating element 25 is formed so that its end originates from one of a pair of terminals 25a, 25b, is folded back at multiple folding portions in a single stroke, is routed over substantially the entire inner circumference-side zone Z1, and then reaches the other of the pair of terminals 25a, 25b. As shown in Fig. 3, the pair of terminals 25a, 25b of the inner circumference-side resistance heating element 25 are exposed to the outside through resistance heating element terminal holes 25c, 25d, respectively, provided in the shaft inner region 27. The pair of terminals 25a, 25b are joined to rod-shaped power supply rods 45a, 45b inserted into the resistance heating element terminal holes 25c, 25d, respectively.

[0023] As shown in Fig. 4, the outer-periphery-side resistance heating element 26 is formed so that its end originates from one of a pair of terminals 26a, 26b, is folded back at multiple folding portions in a single stroke, is wired over substantially the entire outer-periphery-side zone Z2, and then reaches the other of the pair of terminals 26a, 26b. As shown in Fig. 3, the pair of terminals 26a, 26b of the outer-periphery-side resistance heating element 26 are exposed to the outside through resistance heating element terminal holes 26c, 26d formed in the shaft inner region 27. The pair of terminals 26a, 26b are joined to rod-shaped power feed rods 46a, 46b inserted into the resistance heating element terminal holes 26c, 26d, respectively. The inner-periphery-side and outer-periphery-side resistance heating elements 25, 26 are arranged to bypass the RF rod 44 so as not to come into contact with the RF rod 44.

[0024] As shown in FIG. 2 , power supply rods 45a, 45b are disposed inside the cylindrical shaft 40. These power supply rods 45a, 45b are connected to the pair of terminals 25a, 25b of the inner resistance heating element 25, respectively, and power supply rods 46a, 46b are connected to the pair of terminals 26a, 26b of the outer resistance heating element 26, respectively. The power supply rods 45a, 45b are connected to a heater power supply (not shown) for the inner resistance heating element 25, and the power supply rods 46a, 46b are connected to a heater power supply (not shown) for the outer resistance heating element 26. A thermocouple 32 for measuring the temperature near the center of the ceramic plate 20 is also disposed inside the cylindrical shaft 40. The thermocouple 32 is, for example, a sheathed thermocouple. The thermocouple 32 is inserted into a thermocouple insertion hole 30 provided in the shaft inner region 27 of the ceramic plate 20, and the temperature measuring portion at the tip is in contact with the ceramic plate 20 (the bottom surface 31 of the thermocouple insertion hole 30). The inner and outer resistance heating elements 25, 26 are located above the bottom surface 31 of the thermocouple insertion hole 30. Conversely, the bottom surface 31 of the thermocouple insertion hole 30 is located below the inner and outer resistance heating elements 25, 26. As shown in FIG. 5 , the inner resistance heating element 25 crosses the thermocouple insertion hole 30 in a plan view. That is, the inner resistance heating element 25 is wired directly above the bottom surface 31 of the thermocouple insertion hole 30. In this case, the portion of the inner resistance heating element 25 that crosses the thermocouple insertion hole 30 overlaps with the thermocouple insertion hole 30. Furthermore, in a plan view, the thermocouple insertion hole 30 is surrounded by four resistance heating element terminal holes 25c, 25d, 26c, 26d and the RF electrode terminal hole 24c.

[0025] The ratio of the depth D (see FIGS. 2 and 3) of the thermocouple insertion hole 30 to the thickness T (see FIGS. 2 and 3) from the wafer mounting surface 21 of the ceramic plate 20 to the reference plane 28 of the lower surface 20b is preferably 0.055 or more and 0.4 or less. This reduces the difference between the maximum and minimum temperatures on the wafer mounting surface 21. The depth D is the length from the bottom surface 31 of the thermocouple insertion hole 30 to the reference plane 28 of the lower surface 20b of the ceramic plate 20. The depth D of the thermocouple insertion hole 30 is preferably 1 mm or more. Furthermore, the inner diameter of the cylindrical shaft 40 is preferably 52 mm or less.

[0026] Next, an example of how the ceramic heater 10 is used will be described. First, the ceramic heater 10 is installed in a vacuum chamber (not shown), and a wafer W is placed on the wafer-mounting surface 21 of the ceramic heater 10. An upper electrode for generating plasma is disposed above the wafer-mounting surface 21 in the vacuum chamber. Then, power supplied to the inner circumferential resistance heating element 25 and the outer circumferential resistance heating element 26 is adjusted so that the temperature detected by the thermocouple 32 reaches a predetermined target temperature. This controls the temperature of the wafer W to a desired temperature. The vacuum chamber is then set to a vacuum or reduced-pressure atmosphere, and plasma is generated in the vacuum chamber. The plasma is used to perform CVD film formation or etching on the wafer W. The plasma is generated by grounding one of the upper electrode and the RF electrode 24 and applying a high-frequency voltage to the other.

[0027] According to the ceramic heater 10 described above, the inner circumference resistance heating element 25 is located above the bottom surface 31 of the thermocouple insertion hole 30 and has a portion that overlaps with the thermocouple insertion hole 30 in a plan view. In other words, the inner circumference resistance heating element 25 is wired directly above the bottom surface 31 of the thermocouple insertion hole 30. This makes it difficult for a cool spot to occur on the wafer mounting surface 21 in the portion directly above the thermocouple insertion hole 30. This improves the temperature uniformity of the wafer mounting surface 21.

[0028] Furthermore, the ratio of the depth D of the thermocouple insertion hole 30 to the thickness T of the ceramic plate 20 is preferably 0.055 or more and 0.4 or less, which improves the temperature uniformity of the wafer mounting surface 21. This ratio is more preferably 0.055 or more and 0.3 or less, and even more preferably 0.055 or more and 0.28 or less.

[0029] Furthermore, in plan view, the thermocouple insertion hole 30 is surrounded by the four resistance heating element terminal holes 25c, 25d, 26c, and 26d and the RF electrode terminal hole 24c. This allows the distance between the terminal holes to be relatively wide, resulting in a structure in which short circuits between terminals or rods are less likely to occur.

[0030] Furthermore, it is preferable that the depth D of the thermocouple insertion hole 30 is 1 mm or more. This increases the reliability of the temperature measurement results obtained by the thermocouple 32.

[0031] Furthermore, the inner diameter of the cylindrical shaft 40 is preferably 52 mm or less. In this case, the area of ​​the shaft inner region 27 is small, making it difficult to wire the inner or outer resistance heating elements 25, 26 around the thermocouple insertion hole 30, and therefore, the significance of applying the present invention is great.

[0032] Furthermore, it is preferable that the ceramic plate 20 is an AlN plate. Since AlN has a higher thermal conductivity than alumina, the temperature of the wafer mounting surface 21 tends to be uniform.

[0033] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0034] For example, in the above-described embodiment, the RF electrode 24 is embedded in the ceramic plate 20, but the RF electrode 24 may be omitted. Alternatively, an electrostatic electrode may be embedded in the ceramic plate 20 instead of or in addition to the RF electrode 24. The electrostatic electrode is also an example of a functional electrode of the present invention. The electrostatic electrode is embedded in the ceramic plate 20 at a position closest to the wafer mounting surface 21. An electrostatic electrode terminal is provided on the underside of the electrostatic electrode and exposed to the outside through an electrostatic electrode terminal hole provided in the shaft inner region 27. A rod-shaped power feed rod inserted into the electrostatic electrode terminal hole is then joined to the electrostatic electrode terminal. The electrostatic electrode is provided so as not to come into contact with the inner and outer resistance heating elements 25, 26 or the RF electrode 24. When a DC voltage is applied to the electrostatic electrode via the power feed rod, the wafer W is attracted and fixed to the wafer mounting surface 21.

[0035] In the above-described embodiment, the thermocouple insertion hole 30 is arranged so as to be surrounded by the four resistance heating element terminal holes 25c, 25d, 26c, and 26d and the RF electrode terminal hole 24c in a plan view, but is not limited to this. For example, the thermocouple insertion hole 30 may be arranged outside the area surrounded by the four resistance heating element terminal holes 25c, 25d, 26c, and 26d and the RF electrode terminal hole 24c.

[0036] In the above-described embodiment, the inner peripheral resistance heating element 25 crosses the thermocouple insertion hole 30 in a plan view, but the outer peripheral resistance heating element 26 may cross the thermocouple insertion hole 30 in a plan view. Alternatively, as shown in FIG. 8 , the edge of the thermocouple insertion hole 30 may pass within the width of the inner peripheral resistance heating element 25 in a plan view. In the case of FIG. 8 , the shaded portion of the inner peripheral resistance heating element 25 overlaps with the thermocouple insertion hole 30. Although the temperature uniformity of the wafer mounting surface 21 is improved even in the case of FIG. 8 , the above-described embodiment is even better.

[0037] In the above-described embodiment, a so-called two-zone heater is exemplified, but the heater is not limited to a two-zone heater and may have two or more resistance heating elements. For example, the inner circumferential zone Z1 may be divided into a plurality of inner circumferential small zones, and a resistance heating element may be routed in each of the inner circumferential small zones in a unicursal pattern. Also, the outer circumferential zone Z2 may be divided into a plurality of outer circumferential small zones, and a resistance heating element may be routed in each of the outer circumferential small zones in a unicursal pattern.

[0038] In the above-described embodiment, the shaft inner region 27 of the lower surface 20b of the ceramic plate 20 protrudes downward from the surrounding reference surface 28, but the shaft inner region 27 may also be at the same height as the reference surface 28.

[0039] [Experimental Examples 1 to 8] In Experimental Examples 1 to 8, the ceramic heater 10 shown in Figs. 1 to 5 was fabricated. Specifically, a plate made of sintered aluminum nitride and having a diameter φ of 330 mm was used as the ceramic plate 20. A shaft made of sintered aluminum nitride and having a wall thickness of 3 mm was used as the cylindrical shaft 40. Mo was used as the material for the inner and outer peripheral resistance heating elements 25, 26. Table 1 shows the depth D of the thermocouple insertion hole (TC hole) 30, the thickness T of the ceramic plate 20, the ratio D / T, the presence or absence of a heating element above the TC hole 30, and the inner diameter of the cylindrical shaft 40.

[0040] The temperature uniformity evaluation for Experimental Examples 1 to 8 was carried out as follows. The central temperature of the wafer W placed on the wafer placement surface 21 without plasma processing was set to a target temperature (550°C in this case), the inside of the vacuum chamber was set to a nitrogen atmosphere of 5 torr, the entire surface temperature of the wafer W was measured with an infrared camera, and the difference between the maximum and minimum temperatures was taken as the temperature uniformity value. The results are shown in Table 1.

[0041] [Experimental Examples 9-12] In Experimental Examples 9-12, the ceramic heater 110 shown in FIGS. 6 and 7 was fabricated. In FIGS. 6 and 7, the same components as those in the above-described embodiment are designated by the same reference numerals. In the ceramic heater 110, the inner and outer resistance heating elements 25, 26 were positioned below the bottom surface 31 of the thermocouple insertion hole 30, and the wiring was routed around the thermocouple insertion hole 30 rather than across it in a plan view. Other than that, the ceramic heater 110 was identical to the ceramic heater 10. In Experimental Examples 9-12, a plate made of sintered aluminum nitride with a diameter φ of 330 mm was used as the ceramic plate 20. A shaft made of sintered aluminum nitride with a wall thickness of 3 mm was used as the cylindrical shaft 40. The inner and outer resistance heating elements 25, 26 were made of Mo. Table 1 shows the depth D of the TC hole 30, the thickness T of the ceramic plate 20, the ratio D / T, the presence or absence of a heating element above the TC hole 30, and the inner diameter of the cylindrical shaft 40.

[0042] The temperature uniformity of Experimental Examples 9 to 12 was evaluated in the same manner as Experimental Examples 1 to 8. The results are shown in Table 1.

[0043]

[0044] As can be seen from Table 1, in Experimental Examples 1 to 8, in which the inner resistance heating element 25 crosses the TC hole 30 in a planar view, the temperature uniformity values ​​were smaller (better temperature uniformity) than in Experimental Examples 9 to 12, in which the inner and outer resistance heating elements 25, 26 do not cross the TC hole 30 in a planar view. In Experimental Examples 1 to 12, a cylindrical shaft 40 with an inner diameter of 52 mm or less was used. In the ceramic heater 110 structures of Experimental Examples 9 to 12 ( FIGS. 6 and 7 ), when a cylindrical shaft 40 with an inner diameter of 52 mm or less was used, the area of ​​the shaft inner region 27 was small, making it difficult to wire the resistance heating element around the TC hole 30, resulting in a higher temperature uniformity value. Specifically, the temperature in the approximately circular region centered on the TC hole 30 (the shaded region in FIG. 7 ) was lower.

[0045] Furthermore, in Experimental Examples 1 to 7, the ratio D / T was within the range of 0.055 or more and 0.4 or less, and therefore the temperature uniformity value was even smaller than in Experimental Example 8, in which the ratio D / T was 0.033. Furthermore, in Experimental Examples 1 to 7, the depth D of the TC hole 30 was 1 mm or more, and therefore temperature measurement by the thermocouple 32 was more stable than in Experimental Example 8, in which the depth D of the TC hole 30 was 0.5 mm.

[0046] In addition, the thickness T of the ceramic plate 20 is preferably set at an upper limit of 25 mm in order to prevent breakage during firing.

[0047] Experimental Examples 1 to 8 correspond to examples of the present invention, and Experimental Examples 9 to 12 correspond to comparative examples, but it goes without saying that these examples do not limit the present invention in any way.

[0048] The present invention can be used for components used in semiconductor manufacturing equipment, such as electrostatic chuck heaters, electrostatic chucks, and ceramic heaters.

[0049] 10, 110 ceramic heater, 20 ceramic plate, 20a upper surface, 20b lower surface, 21 wafer mounting surface, 22 annular surface, 23 bank, 24 RF electrode, 24a RF electrode terminal, 24c RF electrode terminal hole, 25 inner peripheral resistance heating element, 25a, 25b terminal, 25c, 25d resistance heating element terminal hole, 26 outer peripheral resistance heating element, 26a, 26b terminal, 26c, 26d resistance heating element terminal hole, 27 shaft inner region, 28 reference surface, 30 thermocouple insertion hole, 31 bottom surface, 32 thermocouple, 40 cylindrical shaft, 44 RF rod, 45a, 45b, 46a, 46b power supply rod, W wafer, Z1 inner peripheral zone, Z2 outer peripheral zone.

Claims

1. A ceramic heater comprising: a ceramic plate having a wafer placement surface thereon; two or more resistance heating elements embedded in the ceramic plate and wired for each zone in which the wafer placement surface is divided into two or more parts; a cylindrical shaft that supports the ceramic plate from the lower surface of the ceramic plate; a thermocouple insertion hole provided in a shaft inner region surrounded by the cylindrical shaft in the lower surface of the ceramic plate; and four or more resistance heating element terminal holes provided in the shaft inner region and corresponding to both ends of each of the two or more resistance heating elements, wherein at least one of the two or more resistance heating elements is located above the bottom surface of the thermocouple insertion hole and has a portion overlapping the thermocouple insertion hole in plan view.

2. The ceramic heater according to claim 1, wherein a ratio of a depth of the thermocouple insertion hole to a thickness from the wafer placement surface to the lower surface of the ceramic plate is 0.055 or more and 0.4 or less.

3. The ceramic heater according to claim 1 or 2, wherein in plan view, the thermocouple insertion hole is surrounded by the four or more resistance heating element terminal holes.

4. The ceramic heater according to claim 1 or 2, wherein the depth of the thermocouple insertion hole is 1 mm or more.

5. The ceramic heater according to claim 1 or 2, wherein an inner diameter of the cylindrical shaft is 52 mm or less.

6. The ceramic heater according to claim 1 or 2, wherein the ceramic plate is an AlN plate.

7. The ceramic heater according to claim 1 or 2, wherein the ceramic plate incorporates a functional electrode different from the resistance heating element, electrode terminal holes corresponding to the functional electrode are provided in the shaft inner region, and in plan view, the thermocouple insertion hole is surrounded by the four or more resistance heating element terminal holes and the electrode terminal holes.

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