Ceramic heater

Abstract

To improve thermal uniformity of a ceramic plate by suppressing excessive heat generation (hot spot) in the vicinity of an embedded member in a ceramic heater having the embedded member such as a mounting part in the ceramic plate.SOLUTION: The ceramic heater includes a ceramic plate having a first surface and a second surface, a heater circuit embedded in the ceramic plate, and one or more embedded members for attaching the ceramic plate to an external device or an external member, which are embedded on the second surface side in the ceramic plate to a depth not in contact with the heater circuit. In a plan view of the ceramic plate, the heater circuit overlaps at least one of the embedded members to form an overlapping region. The heater circuit includes a heater main portion arranged to be able to heat a region other than the overlapping region and including a resistance heating element such as a coil, and a heater wire portion arranged in the overlapping region and constituted of a wire-shaped resistance heating element that is not in a coil shape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to ceramic heaters. [Background technology]

[0002] In film deposition equipment for semiconductor manufacturing processes, ceramic heaters are used as support stages to uniformly control the temperature of wafers. A widely used ceramic heater includes a ceramic plate on which the wafer is placed. Multi-zone ceramic heaters with multiple heating zones are also known as ceramic heaters.

[0003] Patent Document 1 (Japanese Patent No. 7030143) discloses an electrostatic chuck assembly including a pack including an electrically insulating upper back plate and a lower back plate, a cooling plate, conductive paths in the lower back plate, and a conductive gasket between the lower back plate and the cooling plate. The electrically insulating upper back plate includes one or more heating elements and one or more electrodes for electrostatically fixing a substrate. The lower back plate is joined to the upper back plate by metal bonding. The lower back plate also includes multiple structures distributed on the lower back plate at multiple different distances from the center of the lower back plate, each of which houses one of multiple fasteners. This document cites screw fasteners as an example of the fasteners and discloses fastening the lower back plate and the cooling plate with bolts.

[0004] Patent Document 2 (Japanese Patent No. 6637184) discloses a wafer mounting table including a ceramic plate, a metal plate, a threaded terminal, and a screw member. The ceramic plate incorporates at least one of an electrostatic electrode and a heater electrode and has a wafer mounting surface. The metal plate is disposed on the surface of the ceramic plate opposite the wafer mounting surface. The threaded terminal is made of a metal with a low thermal expansion coefficient and is bonded to a recess provided on the surface of the ceramic plate opposite the wafer mounting surface by a bonding layer containing ceramic fine particles and a hard brazing material. The screw member is inserted into a through-hole penetrating the metal plate and threadedly engaged with the threaded terminal to fasten the ceramic plate and the metal plate together. This document discloses an example of fastening using the threaded terminal, in which a female threaded terminal is brazed to a recess in an electrostatic chuck (ceramic plate). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7030143 [Patent Document 2] Patent No. 6637184 Summary of the Invention

[0006] Ceramic heaters are required to have a small temperature difference within the surface on which the wafer is placed (i.e., thermal uniformity). In particular, with the recent trend toward finer process miniaturization and higher integration, ceramic heaters are required to have even greater thermal uniformity. From this perspective, it is desirable to minimize the temperature difference between areas where a resistance heating element is present and areas where it is not. To achieve this, it is preferable to distribute the resistance heating element throughout the entire area of ​​the ceramic heater. Meanwhile, in recent years, heater designs in which mounting parts are disposed within the ceramic plate have been proposed to improve mountability (e.g., Patent Documents 1 and 2). However, depending on the material of the mounting parts, a temperature difference may occur between the base of the ceramic plate and the mounting parts. As a result, the area of ​​the ceramic plate near the mounting parts, combined with the heat generated by the resistance heating element, becomes a hot spot, resulting in a problem of poor thermal uniformity of the ceramic heater.

[0007] The present inventors have now focused on the overlapping region where the heater circuit overlaps with the embedded member when viewed in a plane in a ceramic heater having an embedded member such as an attachment part within the ceramic plate, and have discovered that by configuring the heater circuit arranged in the overlapping region with a wire-shaped resistance heating element (rather than a coil-shaped), it is possible to suppress excessive heat generation (hot spots) near the embedded member and improve the thermal uniformity of the ceramic plate.

[0008] Therefore, an object of the present invention is to improve the thermal uniformity of the ceramic plate by suppressing excessive heat generation (hot spots) near the embedded member in a ceramic heater having an embedded member such as an attachment part in the ceramic plate.

[0009] According to the present disclosure, the following aspects are provided. [Aspect 1] a ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface; a heater circuit embedded in the ceramic plate; one or more embedding members for attaching the ceramic plate to an external device or an external member, the embedding members being embedded in the ceramic plate on a second surface side thereof to a depth not in contact with the heater circuit; Equipped with When the ceramic plate is viewed from above, the heater circuit overlaps with at least one of the embedded members to form an overlapping region, The heater circuit a heater main portion that is arranged to be able to heat an area other than the overlapping area and includes a resistance heating element in at least one form selected from the group consisting of a coil, a linear zigzag structure, a printed pattern, a ribbon, and a mesh; a heater wire portion disposed in the overlapping region and configured as a wire-like resistance heating element rather than a coil; Including, ceramic heater. [Aspect 2] 2. The ceramic heater according to aspect 1, wherein the wire-shaped resistance heating element has a diameter of 0.3 to 0.8 mm. [Aspect 3] 3. The ceramic heater according to aspect 1 or 2, wherein the number of the embedded members is three or more. [Aspect 4] The ceramic heater according to any one of aspects 1 to 3, wherein the heater wire portion is disposed in the ceramic plate at a depth position spaced 5 to 20 mm from the top of the embedded member in the thickness direction. [Aspect 5] 5. The ceramic heater according to any one of aspects 1 to 4, wherein the heater wire portion is arranged to pass through an area within a radius of 15 mm from the center of the embedded member when the ceramic plate is viewed from above. [Aspect 6] A ceramic heater according to any one of aspects 1 to 5, wherein the ceramic plate comprises aluminum nitride or aluminum oxide. [Aspect 7] The ceramic heater according to any one of aspects 1 to 6, wherein the resistance heating element comprises at least one selected from the group consisting of tungsten, molybdenum, a tungsten-molybdenum alloy, tungsten carbide, a tungsten carbide-titanium nitride composite material, a tungsten carbide-aluminum oxide composite material, and niobium. [Aspect 8] A ceramic heater according to any one of aspects 1 to 7, wherein the heater main portion and the heater wire portion are a continuous, integrated resistance heating element. [Aspect 9] A ceramic heater according to any one of aspects 1 to 7, wherein the heater main portion and the heater wire portion are separate resistance heating elements and are connected to each other via a connection terminal. [Aspect 10] 10. The ceramic heater according to claim 9, wherein the connection terminal is a conductive member having two through holes with different diameters to which resistance heating elements with different wire diameters can be connected. [Aspect 11] 11. The ceramic heater according to any one of aspects 1 to 10, wherein the ceramic heater is a multi-zone ceramic heater including two or more heating zones. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing an example of a ceramic heater according to the present invention. [Figure 2] FIG. 2 is a schematic top view showing the ceramic heater shown in FIG. [Figure 3] 2 is an enlarged schematic cross-sectional view showing the vicinity of an embedded member of the ceramic heater shown in FIG. 1. FIG. [Figure 4] FIG. 2 is a plan view schematically illustrating an example of a configuration of a heater circuit including a connection terminal. [Figure 5] FIG. 5 is a plan view schematically showing the connection terminal shown in FIG. 4. [Figure 6] FIG. 1 is a schematic cross-sectional view showing an example of a conventional ceramic heater. DETAILED DESCRIPTION OF THE INVENTION

[0011] The multi-zone ceramic heater according to the present invention is a ceramic platform for supporting a wafer in a semiconductor manufacturing device. Typically, the ceramic heater according to the present invention can be a ceramic heater for a semiconductor film formation device. Typical examples of film formation devices include CVD (chemical vapor deposition) devices (e.g., thermal CVD devices, plasma CVD devices, photo CVD devices, and MOCVD devices) and PVD (physical vapor deposition) devices.

[0012] 1 and 2 show one embodiment of a ceramic heater. The ceramic heater 10 shown in FIGS. 1 and 2 includes a ceramic plate 12, a heater circuit 14, and one or more embedded members 16. The ceramic plate 12 has a first surface 12a on which a wafer is placed and a second surface 12b opposite the first surface 12a. The heater circuit 14 is embedded in the ceramic plate 12. The embedded members 16 are members (e.g., mounting parts) for attaching the ceramic plate 12 to an external device or external member, and are embedded in the ceramic plate 12 on the second surface 12b side to a depth such that they do not come into contact with the heater circuit 14. When the ceramic plate 12 is viewed from above, the heater circuit 14 overlaps with at least one of the embedded members 16, forming an overlap region O. The heater circuit 14 includes a heater main portion 14a and a heater wire portion 14b. The heater main portion 14a is disposed so as to be able to heat the region other than the overlapping region O, and includes a resistance heating element in at least one form selected from the group consisting of a coil, a linear zigzag structure, a print pattern, a ribbon, and a mesh. On the other hand, the heater wire portion 14b is disposed in the overlapping region O and is composed of a wire-like resistance heating element that is not coiled. In this way, in the ceramic heater 10 having an embedded member 16 such as an attachment part in the ceramic plate 12, attention is focused on the overlapping region O where the heater circuit 14 overlaps with the embedded member 16 in a plan view, and the heater circuit 14 disposed in the overlapping region O is composed of a wire-like resistance heating element (i.e., the heater wire portion 14b) (not coiled), thereby suppressing excessive heat generation (hot spots) near the embedded member 16 and improving the thermal uniformity of the ceramic plate 12.

[0013] As mentioned above, with the recent trend toward finer process miniaturization and higher integration, ceramic heaters are required to have even greater thermal uniformity. To achieve this, it is preferable to distribute a resistance heating element throughout the entire ceramic heater. Meanwhile, heater designs in which mounting parts are disposed within the ceramic plate have also been proposed in recent years to improve mountability (e.g., Patent Documents 1 and 2). However, depending on the material of the mounting parts, a temperature difference may occur between the ceramic plate base and the mounting parts. As a result, the area of ​​the ceramic plate near the mounting parts may become a hot spot due to the heat generated by the resistance heating element, resulting in a deterioration of the ceramic heater's thermal uniformity. Specifically, in a conventional ceramic heater 110 shown in FIG. 6 , in which a coil-shaped heater circuit 114 and an embedded member 116 such as a mounting part are embedded within a ceramic plate 112, excessive heat is observed near the embedded member 116, and a hot spot H may occur on the surface of the ceramic plate 112 near the embedded member 116. This is thought to be because the presence of the embedded member 116 makes it difficult for the heat generated by the coil-shaped heater circuit 114 to escape locally. Therefore, in the present invention, as shown in Fig. 1, the heater circuit 14 disposed in the overlapping region O is configured with a wire-shaped (not coil-shaped) resistance heating element (i.e., heater wire portion 14b). This makes it possible to suppress excessive heat generation (hot spots H) near the embedded member 16 and improve the thermal uniformity of the ceramic plate 12. In other words, by using a wire-shaped resistance heating element (a simple, unwound resistance heating wire) with a small heat generation amount as the heater circuit 14 in the area corresponding to the embedded member 16 where localized high temperatures may occur, it is possible to suppress excessive heat generation in that area and the resulting occurrence of hot spots H.

[0014] The ceramic plate 12 preferably contains aluminum nitride or aluminum oxide, more preferably aluminum nitride, in its main portion (i.e., the ceramic substrate) other than the embedded components such as the heater circuit 14 and the embedded member 16, from the viewpoints of excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics similar to those of silicon.

[0015] The ceramic plate 12 is preferably disk-shaped. However, the planar shape of the disk-shaped ceramic plate 12 does not need to be a perfect circle; for example, it may be an incomplete circle with a missing portion, such as an orientation flat. The diameter of the ceramic plate 12 is 220 mm or more, typically 220 to 450 mm, and particularly for 300 mm silicon wafers, typically 320 to 380 mm. The thickness of the ceramic plate 12 is typically 10 to 25 mm.

[0016] The ceramic plate 12 may be a ceramic plate assembly in which an upper ceramic plate 12c providing the first surface 12a and a lower ceramic plate 12d providing the second surface 12b are joined together. In this case, it is preferable that the lower ceramic plate 12d is provided with an embedded member 16, but this is not limiting, and the embedded member 16 may penetrate the lower ceramic plate 12d in the thickness direction and reach the upper ceramic plate 12c.

[0017] 1, the heater circuit 14 includes a heater main portion 14a disposed so as to be able to heat the area other than the overlapping area O, and a heater wire portion 14b disposed in the overlapping area O. The heater circuit 14, as a whole including the heater main portion 14a and the heater wire portion 14b, is preferably disposed so as to be able to heat the entire area of ​​the ceramic plate 12.

[0018] The heater main portion 14a includes a resistance heating element having at least one form selected from the group consisting of a coil, a linear zigzag structure, a printed pattern, a ribbon, and a mesh. A coil has a configuration in which a resistance heating wire is wound three-dimensionally, while a linear zigzag structure has a configuration in which a resistance heating wire is alternately folded two-dimensionally within a plane. The printed pattern is not particularly limited, but typically has a pattern in which strip-shaped lines of the resistance heating element layer alternate between straight and bent (e.g., zigzag).

[0019] The heater wire portion 14b is composed of a wire-shaped resistance heating element that is not coiled (i.e., not wound). The diameter of the wire-shaped resistance heating element is preferably 0.3 to 0.8 mm, more preferably 0.3 to 0.5 mm. As shown in FIG. 3, the heater wire portion 14b is disposed in the ceramic plate 12 at a depth of preferably 5 to 20 mm, more preferably 10 to 20 mm, from the top of the embedding member 16 in the thickness direction, from the viewpoint of ensuring a certain distance from the embedding member 16 and uniformly distributing locally high temperatures. Furthermore, the heater wire portion 14b can be disposed so as to pass through an area preferably within a radius of 15 mm, more preferably within a radius of 10 mm, from the center of the embedding member 16 when viewed from above. Therefore, by using the heater wire portion 14b, the heater circuit 14 can be distributed throughout the ceramic plate 12 regardless of the position of the embedding member 16, which facilitates improving the thermal uniformity of the ceramic plate 12.

[0020] The heater main portion 14a and the heater wire portion 14b may be a continuous, integrated resistance heating element. Alternatively, the heater main portion 14a and the heater wire portion 14b may be separate resistance heating elements connected to each other via a connection terminal 15, as shown in FIGS. 4 and 5. In this case, the connection terminal 15 is preferably disposed on or near the outer periphery of the overlapping region O. Therefore, the connection terminal 15 can be used to connect resistance heating elements with different wire diameters. In other words, this embodiment is advantageous when the wire diameter of the heater main portion 14a and the wire diameter of the heater wire portion 14b are different. As shown in FIG. 5, the connection terminal 15 is preferably a conductive member having two through holes 15a with different diameters that can connect resistance heating elements with different wire diameters. In this configuration, the heater main part 14a and the heater wire part 14b are inserted into the two through holes 15a and crimped and / or fixed, respectively, thereby ensuring electrical connection between the heater main part 14a and the heater wire part 14b. The shape of the connection terminal 15 is not particularly limited, but may be, for example, spherical. Note that if the wire diameter of the heater main part 14a (e.g., coil) and the wire diameter of the heater wire part 14b are the same, the connection terminal 15 is not necessary.

[0021] The resistance heating element constituting the heater circuit 14 (i.e., the heater main portion 14a, the heater wire portion 14b, and optionally the connection terminal 15) preferably contains at least one material selected from the group consisting of tungsten, molybdenum, a tungsten-molybdenum alloy, tungsten carbide, a tungsten carbide-titanium nitride composite material, a tungsten carbide-aluminum oxide composite material, and niobium.

[0022] The heater circuit 14 may be provided with a pair of heater terminals for supplying power to the heater circuit 14. Preferably, the heater terminals are connected to both ends of the heater circuit 14. There may be two or more pairs of heater terminals. The heater terminals are rod-shaped, and the heater circuit 14 may be connected to a heater power supply via the rod-shaped heater terminals.

[0023] The embedded member 16 is a member (e.g., a mounting part) for mounting the ceramic plate 12 to an external device or member. The embedded member 16 may be made of a material different from that of the ceramic substrate of the ceramic plate 12. Preferably, the embedded member 16 is made of the same material as the resistance heating element. Therefore, the embedded member 16 preferably includes at least one selected from the group consisting of tungsten, molybdenum, a tungsten-molybdenum alloy, tungsten carbide, a tungsten carbide-titanium nitride composite material, a tungsten carbide-aluminum oxide composite material, and niobium. The embedded member 16 may have any shape that can function as a mounting part. For example, as shown in FIGS. 1 and 3, the embedded member 16 may include a large-diameter upper portion 16a having a relatively large diameter and a small-diameter lower portion 16b having a relatively small diameter. In this case, it is preferable that the large-diameter upper portion 16a is disposed in the center of the ceramic plate 12 in the thickness direction, and the small-diameter lower portion 16b is disposed on the second surface 12b side of the ceramic plate 12, in order to prevent the embedded member 16 from being detached from the ceramic plate 12. It is also preferable that the embedded member 16 includes a female-threaded portion 16c (e.g., a nut) having a female threaded shape. In this way, a fastening member 18 such as a bolt having a male threaded shape for attaching the embedded member 16 to an external device or member can be screwed into the female-threaded portion 16c of the embedded member 16 to fix it.

[0024] The number of embedded members 16 is preferably three or more, more preferably six or more. With such a number, the ceramic plate 12 can be securely fixed to an external device or member. The number of embedded members 16 is preferably 25 or less, more preferably 20 or less. With such a number, the number of embedded members 16 reduces the number of locations where thermal uniformity is locally reduced, making it easier to achieve a good yield in the semiconductor manufacturing process. When there are multiple embedded members 16, they are preferably evenly arranged around the circumference of the ceramic plate 12, as shown in FIG. 2 . For example, the multiple embedded members 16 are preferably arranged rotationally symmetrically with respect to the central axis of the ceramic plate 12.

[0025] The ceramic heater 10 may be a multi-zone ceramic heater including two or more heating zones. In the case of a multi-zone heater (e.g., a two-zone heater), the ceramic plate 12 may include an inner zone and an outer zone when viewed from above. The inner zone is defined as a circular region within a predetermined distance from the center of the ceramic plate 12. A central region is located at the center of the inner zone. The outer zone is defined as an annular region outside the inner zone. The outer zone may be divided into multiple outer subzones (e.g., two to four). For example, the outer zone may be composed of multiple outer subzones divided into arcs (e.g., two to four). Alternatively, the outer zone may have two or more concentric annular regions of different sizes that do not overlap each other. In this case, the outer zone will have at least a first outer zone adjacent to the inner zone and a second outer zone located outside the first outer zone. If necessary, a third or more outer zones may be present outside the second outer zone. However, the ceramic heater 10 of the present invention may also be a one-zone heater.

[0026] In the case of a multi-zone heater (e.g., a two-zone heater), the heater circuit 14 preferably includes an inner zone heater circuit, an outer zone heater circuit, and a pair of jumpers. The inner zone heater circuit is embedded in the inner zone of the ceramic plate 12. However, the inner zone heater circuit may extend not only to the inner zone but also to the outer zone. The outer zone heater circuit is embedded in the outer zone of the ceramic plate 12. However, the outer zone heater circuit may extend not only to the outer zone but also to the inner zone. Therefore, the inner zone heater circuit and the outer zone heater circuit may overlap each other when viewed from above. The pair of jumpers are embedded in the inner zone of the ceramic plate 12 so as not to contact the inner zone heater circuit and are electrically connected to the outer zone heater circuit. The inner zone heater circuit and the outer zone heater circuit may be arranged on the same plane in a cross-sectional view, or the inner zone heater circuit and the outer zone heater circuit may be arranged on different planes in a cross-sectional view. Each of the inner and outer zone heater circuits is preferably arranged in a single-stroke configuration when viewed from above, which may take various known forms such as a spiral or alternating forward and backward stroke.

[0027] The ceramic plate 12 may further include an RF electrode and / or an ESC electrode therein. In this case, the RF electrode and / or the ESC electrode are preferably embedded in the ceramic plate 12 at a depth closer to the first surface 12a than the heater circuit 14. The RF electrode enables film formation by a plasma CVD process when high frequency is applied to it. The ESC electrode is an abbreviation for electrostatic chuck (ESC) electrode and is also called an electrostatic electrode. When a voltage is applied to the ESC electrode from an external power supply, it chucks a wafer placed on the surface of the ceramic plate 12 by the Johnsen-Rahbek force. The ESC electrode is preferably a circular thin-layer electrode with a diameter slightly smaller than that of the ceramic plate 12. For example, it may be a mesh electrode formed by weaving thin metal wires into a net shape into a sheet. The ESC electrode may also be used as a plasma electrode. That is, by applying high frequency to the ESC electrode, the ESC electrode can also be used as an RF electrode, allowing film formation by a plasma CVD process. An RF terminal or an ESC terminal for power supply is connected to the RF electrode or the ESC electrode. The RF terminal or the ESC terminal has a rod shape, and the RF electrode or the ESC electrode can be connected to an external power supply via the rod-shaped RF terminal or the ESC terminal.

[0028] A cooling plate may be provided on the second surface 12b of the ceramic plate 12. The cooling plate may have a cooling plate configuration generally used for ceramic heaters and electrostatic chucks. The cooling plate may be made of a metal such as aluminum or an aluminum alloy, or may be made of a metal matrix composite (MMC) such as SiSiCTi (a composite material containing Si, SiC, and Ti). A typical cooling plate is disk-shaped and may have channels inside through which a coolant can circulate. [Example]

[0029] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0030] Example 1 (1) Fabrication of ceramic heater Using the components shown below, a ceramic heater 10 having a cross-sectional structure as shown in FIG. 1 was fabricated by a known procedure. <Component parts and their specifications> Ceramic plate 12: a circular aluminum nitride sintered body (diameter: 330 mm, thickness: 20 mm) (with heater circuit 14 and embedded member 16 embedded inside) Heater circuit 14: A circuit in which heater main portion 14a (material: molybdenum, winding diameter: 3.5 mm, wire diameter: 0.5 mm) consisting of a three-dimensional coil-shaped resistance heating element embedded in a predetermined circuit pattern at a depth of 10 mm from first surface 12a, and heater wire portion 14b consisting of a simple resistance heating wire (material: molybdenum, wire diameter: 0.4 mm, disposed in an overlapping region O with embedded member 16 in ceramic plate 12) that is not in a coil shape, are connected by connection terminals 15 (see Figure 4). The heater wire portion 14b is located at a depth of 5 mm from the top of the embedded member 16 in the thickness direction, and is arranged so as to pass through an area within a radius of 9 mm from the center of the embedded member 16 when the ceramic plate 12 is viewed from above. Buried member 16: Three metal mounting parts with a large-diameter upper portion 16a and a small-diameter lower portion 16b (material: molybdenum, diameter of large-diameter upper portion 16a: 25 mm, diameter of small-diameter lower portion 16b: 10 mm, height of buried member 16: 15 mm) Heater terminals: Two nickel terminal rods connected to both ends of the heater circuit 14

[0031] (2) Evaluation The resulting ceramic heater was evaluated as follows.

[0032] <Heat uniformity> The ceramic heater 10 was placed in the chamber of a film forming apparatus. The chamber was evacuated and N2 gas was introduced, setting the N2 gas pressure in the chamber to 5 Torr. The ceramic heater 10 was heated to a set temperature of 650°C by supplying power to the heater circuit 14 via the heater terminals. At this set temperature, the temperature distribution on the first surface 12a of the ceramic plate 12 was measured using an infrared camera. Based on the obtained temperature distribution map, the difference between the maximum and minimum temperatures within a 300 mm diameter area (i.e., the maximum in-plane temperature difference) was calculated as an index of thermal uniformity. The results are shown in Table 1, and excessive heat generation (hot spots) near the embedded material was suppressed.

[0033] <Evaluation of uniform heating distribution> As mentioned above, the embedded member 16 reduces the number of locations where thermal uniformity is locally reduced, making it easier to achieve a good yield in the semiconductor manufacturing process. That is, the region of the ceramic plate 12 located above the embedded member 16 has locally poor thermal uniformity, resulting in variations in thermal uniformity (thermal uniformity distribution) within the first surface 12a. This thermal uniformity distribution satisfies the preferred range (for example, 10°C or less) for the maximum temperature difference within the surface in thermal uniformity evaluation, but suggests a state in which there are points within the surface where the temperature varies slightly. To evaluate this thermal uniformity distribution, the total area of ​​the upper surface of the embedded member 16 is calculated as the projected area, and this projected area is multiplied by the area of ​​the wafer-mounting surface with a diameter of 300 mm (70650 mm 2 ) and calculate the percentage based on the following criteria: Rating A: Projected area of ​​buried materials is 15% or less Rating B: Projected area of ​​buried materials exceeds 15% The evaluation was conducted according to the following criteria. Evaluation A means that it is easier to achieve a good yield in the semiconductor manufacturing process than evaluation B.

[0034] Examples 2-6 A ceramic heater was produced and evaluated in the same manner as in Example 1, except that the number of embedded members and the depth positions of the heater wire portions were set as shown in Table 1. The results are shown in Table 1, and excessive heat generation (hot spots) near the embedded members was suppressed.

[0035] Example 7 (comparison) A ceramic heater was fabricated and evaluated in the same manner as in Example 1, except that, in the overlapping region O in the ceramic plate 12 as shown in Figure 6, the above-mentioned three-dimensional coil-shaped resistance heating element was used instead of the heater wire portion 14b (i.e., the heater circuit 14 was composed of only the heater main portion 14a). The results are shown in Table 1, and as shown in Figure 6, a hot spot H occurred in the location corresponding to the overlapping region O. In this example, since the heating uniformity was poor, it was determined that there was no need to evaluate the heating uniformity distribution, and this is shown as a blank (-) in Table 1.

[0036] [Table 1]

[0037] As shown in Table 1, Examples 1 to 6, in which the heater circuit 14 in the overlapping region O was configured with a wire-shaped resistance heating element (i.e., the heater wire portion 14b), showed a significantly smaller maximum in-plane temperature difference than Example 7 (Comparative Example), in which the heater circuit 14 in the overlapping region O was configured with a three-dimensional coil-shaped heater main portion 14a. Therefore, it can be seen that by adopting the configuration of the present invention, excessive heat generation (hot spots) near the embedded member can be suppressed, and the thermal uniformity of the ceramic plate can be improved. [Explanation of symbols]

[0038] 10,110 Ceramic heater 12,112 ceramic plates 12a Front page 12b Second side 12c Upper ceramic plate 12d Lower ceramic plate 14,114 Heater Circuit 14a Main part of heater 14b Heater wire part 15 Connection terminal 15a through hole 16,116 Buried materials 16a Large diameter upper part 16b Small diameter lower part 16c female thread 18 Fastening members O overlap area H Hotspot

Claims

1. a ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface; a heater circuit embedded in the ceramic plate; one or more embedding members for attaching the ceramic plate to an external device or an external member, the embedding members being embedded in the ceramic plate on a second surface side thereof to a depth not in contact with the heater circuit; Equipped with When the ceramic plate is viewed from above, the heater circuit overlaps with at least one of the embedded members to form an overlapping region, The heater circuit a heater main portion that is disposed so as to be able to heat an area other than the overlapping area, and that includes a resistance heating element in at least one form selected from the group consisting of a coil, a linear zigzag structure, a printed pattern, a ribbon, and a mesh; a heater wire portion disposed in the overlapping region and configured as a wire-like resistance heating element rather than a coil; Including, ceramic heater.

2. 2. The ceramic heater according to claim 1, wherein the wire-shaped resistance heating element has a diameter of 0.3 to 0.8 mm.

3. 3. The ceramic heater according to claim 1, wherein the number of the embedded members is three or more.

4. 3. The ceramic heater according to claim 1, wherein the heater wire portion is disposed in the ceramic plate at a depth position spaced 5 to 20 mm from the top of the embedded member in the thickness direction.

5. 3. The ceramic heater according to claim 1, wherein the heater wire portion is disposed so as to pass through an area within a radius of 15 mm from the center of the embedding member when the ceramic plate is viewed from above.

6. The ceramic heater according to claim 1 or 2, wherein the ceramic plate comprises aluminum nitride or aluminum oxide.

7. 3. The ceramic heater according to claim 1, wherein the resistance heating element contains at least one selected from the group consisting of tungsten, molybdenum, a tungsten-molybdenum alloy, tungsten carbide, a tungsten carbide-titanium nitride composite material, a tungsten carbide-aluminum oxide composite material, and niobium.

8. 3. The ceramic heater according to claim 1, wherein the heater main portion and the heater wire portion are a continuous, integrated resistance heating element.

9. 3. The ceramic heater according to claim 1, wherein the heater main portion and the heater wire portion are separate resistance heating elements and are connected to each other via connection terminals.

10. 10. The ceramic heater according to claim 9, wherein the connection terminal is a conductive member having two through holes with different diameters to which resistance heating elements with different wire diameters can be connected.

11. 3. The ceramic heater according to claim 1, wherein the ceramic heater is a multi-zone ceramic heater including two or more heating zones.

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