Ceramic heater

Abstract

Provided is a ceramic heater in which damage due to temperature distribution of center cooling is less likely to occur without impairing the function of an RF / ESC electrode. The ceramic heater comprises: a ceramic plate having a first surface on which a wafer is placed and a second surface which faces the first surface; a first RF / ESC electrode which is embedded in the ceramic plate in parallel to the first surface; a second RF / ESC electrode which is electrically connected to the first RF / ESC electrode and is embedded in parallel to the first surface at a depth position, in the ceramic plate, apart further from the first surface as compared to the first RF / ESC electrode; an RF / ESC rod which has one end electrically connected to the second RF / ESC electrode and the other end extending to the outside of the ceramic plate from the second surface; an RF / ESC terminal hole which is a bottomed hole provided from the second surface of the ceramic plate toward the second RF / ESC electrode in the thickness direction and to which the tip portion of the RF / ESC rod is inserted; and a heater circuit which is embedded at a depth position, in the ceramic plate, closer to the second surface as compared to the second RF / ESC electrode. The distance between the center lines of the first RF / ESC electrode and the second RF / ESC electrode is 2-7 mm. The distance from the first surface to the bottom of the RF / ESC terminal hole is 4-9 mm.

Description

Ceramic heater

[0001] The present disclosure relates to ceramic heaters.

[0002] In film deposition and etching apparatuses for semiconductor manufacturing processes, ceramic heaters are used as support stages for uniformly controlling the temperature of wafers. A widely used ceramic heater includes a ceramic plate on which the wafer is placed and a cylindrical ceramic shaft attached to the ceramic plate. The ceramic plate typically has a ceramic base made of aluminum nitride (AlN) or other material with excellent heat and corrosion resistance, with internal electrodes embedded therein, such as RF electrodes and / or electrostatic chuck (ESC) electrodes (hereinafter collectively referred to as RF / ESC electrodes), heater electrodes, and the like.

[0003] Patent Document 1 (Japanese Patent No. 6773917) discloses a wafer support table having an RF electrode and a heater electrode embedded within a disc-shaped ceramic base having a wafer mounting surface. In this wafer mounting table, the RF electrode is composed of multiple RF zone electrodes provided for each zone obtained by dividing the wafer mounting surface into multiple sections, and the multiple RF zone electrodes are provided in at least two stages at different distances from the wafer mounting surface. The multiple RF zone electrodes are each independently connected to multiple RF zone electrode conductors through electrode terminals provided on the back surface of the ceramic base.

[0004] Patent Document 2 (JP 2023-87447 A) discloses a wafer mounting table including a ceramic base having a wafer mounting surface, a first conductive layer and a second conductive layer embedded at different heights within the ceramic base, and a conductive part that electrically connects the first conductive layer and the second conductive layer, and this conductive part is a horizontally placed coil or a perforated cylindrical body.

[0005] Patent Document 3 (Japanese Patent No. 6530878) discloses a wafer mounting table including a ceramic base having a wafer mounting surface, a first electrode and a second electrode embedded at different heights within the ceramic base so as to be parallel to the wafer mounting surface, and a conductive portion that electrically connects the first electrode and the second electrode, the conductive portion being made up of multiple stacked plate-shaped metal meshes that are parallel to the wafer mounting surface.

[0006] Japanese Patent No. 6773917 Japanese Patent Application Laid-Open No. 2023-87447 Japanese Patent No. 6530878

[0007] With the recent trend toward finer processing and higher integration in semiconductor manufacturing processes, the various operating conditions for ceramic heaters are becoming increasingly strict, such as higher process temperatures (e.g., 700°C or higher), increased RF power (e.g., 2 kW or higher), and higher RF frequencies (e.g., 27 MHz or higher). This has led to the need for precise control of wafer temperature (especially the temperature at the wafer's periphery). While efforts have traditionally been made to achieve uniform plasma distribution, the in-plane temperature uniformity required of ceramic heaters is also becoming increasingly strict.

[0008] When semiconductor manufacturing processes are performed, individual tuning is typically performed for each process condition. For example, to increase the temperature of the outer periphery of a wafer, which is prone to temperature drops due to the chamber environment, processes such as film formation are often performed by creating a temperature distribution on the plate surface of a ceramic heater that results in a relatively high temperature at the outer periphery (so-called periphery hot) and, in other words, a relatively low temperature at the center (so-called center cool). Here, due to the structure of a ceramic heater with a ceramic shaft, multiple terminals and terminal holes are concentrated in the center of the ceramic plate on which the wafer is placed. In this case, if the ceramic heater experiences a center cool temperature distribution, excessive tensile stress may be generated in the terminal holes of the ceramic plate. In particular, stress tends to concentrate in the terminal holes for the RF / ESC electrodes (hereinafter referred to as RF / ESC terminal holes), which are formed relatively deeper than the other terminal holes. Therefore, the ceramic heater is prone to breakage near the RF / ESC terminal holes. In this regard, it is possible to form the RF / ESC terminal holes shallower to avoid stress concentration. However, in this case, the depth of the RF / ESC electrode from the wafer-mounting surface of the ceramic plate becomes large, which increases impedance and has a significant adverse effect on plasma control by the RF electrode and reduces the wafer chucking function of the ESC electrode. Therefore, a ceramic heater is desired that is less susceptible to damage caused by temperature distribution in the center cooler, without impairing the function of the RF / ESC electrode (i.e., plasma control function and / or wafer chucking function).

[0009] The present inventors have now discovered that by (i) employing a two-layer RF / ESC electrode structure including a first RF / ESC electrode and a second RF / ESC electrode that are electrically connected to each other and arranged in parallel, (ii) setting the distance between the center lines of the first RF / ESC electrode and the second RF / ESC electrode to 2 to 7 mm, and (iii) setting the distance from the wafer-mounting surface of the ceramic plate to the bottom of the RF / ESC terminal hole to 4 to 9 mm, it is possible to provide a ceramic heater that is less susceptible to damage caused by temperature distribution in the center cool without impairing the function of the RF / ESC electrode.

[0010] Therefore, an object of the present invention is to provide a ceramic heater that is less susceptible to damage caused by temperature distribution in the center cooler without impairing the function of the RF / ESC electrode.

[0011] The present disclosure provides the following aspects: [Aspect 1] A ceramic heater comprising: a ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface, a first RF / ESC electrode embedded in the ceramic plate parallel to the first surface, a second RF / ESC electrode electrically connected to the first RF / ESC electrode and embedded in the ceramic plate parallel to the first surface at a depth farther from the first surface than the first RF / ESC electrode, an RF / ESC rod having one end electrically connected to the second RF / ESC electrode and the other end extending from the second surface to the outside of the ceramic plate, an RF / ESC terminal hole that is a bottomed hole provided in the thickness direction from the second surface of the ceramic plate toward the second RF / ESC electrode, and into which a tip portion of the RF / ESC rod is inserted, and a heater circuit embedded in the ceramic plate at a depth closer to the second surface than the second RF / ESC electrode, A ceramic heater, wherein the distance between the center lines of the first RF / ESC electrode and the second RF / ESC electrode is 2 to 7 mm, and the distance from the first surface to the bottom of the RF / ESC terminal hole is 4 to 9 mm. [Aspect 2] The ceramic heater according to Aspect 1, further comprising a connecting member, located between the first RF / ESC electrode and the second RF / ESC electrode in the ceramic plate, for electrically connecting the first RF / ESC electrode and the second RF / ESC electrode. [Aspect 3] The ceramic heater according to Aspect 2, wherein the connecting member is at least one selected from the group consisting of a coil, a metal tablet, and a metal mesh laminate. [Aspect 4] The ceramic heater according to any one of Aspects 1 to 3, wherein the ceramic plate contains aluminum nitride or aluminum oxide. [Aspect 5] The ceramic heater according to any one of Aspects 1 to 4, wherein the first RF / ESC electrode and / or the second RF / ESC electrode 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 6] The ceramic heater according to any one of Aspects 2 to 5, wherein the connecting member 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 7] The ceramic heater according to any one of Aspects 2 to 6, wherein the connecting member is disposed in a position that at least partially overlaps with the RF / ESC terminal hole when the ceramic plate is viewed from above. [Aspect 8] The ceramic heater according to any one of Aspects 2 to 6, wherein the connecting member is disposed in a position that does not overlap with the RF / ESC terminal hole when the ceramic plate is viewed from above. [Aspect 9] The ceramic heater according to any one of Aspects 1 to 8, further comprising a cylindrical ceramic shaft attached to the second surface of the ceramic plate and having an internal space. [Aspect 10] The ceramic heater according to any one of Aspects 1 to 9, wherein, in a plan view, the first RF / ESC electrode is disc-shaped and the second RF / ESC electrode is disc-shaped or a combination of annular and linear portions. [Aspect 11] The ceramic heater according to any one of Aspects 1 to 10, wherein each of the first RF / ESC electrode and the second RF / ESC electrode is in at least one form selected from the group consisting of mesh, punched metal, and printed pattern. [Aspect 12] The ceramic heater according to any one of Aspects 1 to 11, further comprising a heater rod having one end electrically connected to the heater circuit and the other end extending from the second surface to the outside of the ceramic plate. [Aspect 13] The ceramic heater according to any one of Aspects 1 to 12, further comprising an embedded member embedded in the ceramic plate between a bottom of the RF / ESC terminal hole and the second RF / ESC electrode, and electrically connecting the RF / ESC rod and the second RF / ESC electrode.

[0012] FIG. 1 is a perspective top view schematically showing one example of a ceramic heater according to the present invention, corresponding to Example 1. FIG. 2 is a schematic cross-sectional view showing the ceramic heater shown in FIG. 1. FIG. 3 is a schematic cross-sectional view conceptually showing the internal structure of a ceramic plate in the ceramic heater shown in FIG. 1. FIG. 4 is a perspective top view schematically showing another example of a ceramic heater according to the present invention, corresponding to Example 2. FIG. 5 is a schematic cross-sectional view showing the ceramic heater shown in FIG. 4. FIG. 5 is a schematic cross-sectional view conceptually showing the internal structure of a ceramic plate in the ceramic heater shown in FIG. 4. FIG. 6 is a perspective top view schematically showing another example of a ceramic heater according to the present invention, corresponding to Example 3. FIG. 7 is a schematic cross-sectional view conceptually showing the internal structure of a ceramic plate in the ceramic heater shown in FIG. 7. FIG. 7 is a perspective top view conceptually showing another example of a ceramic heater according to the present invention, corresponding to Example 4. FIG. 10 is a schematic cross-sectional view showing the ceramic heater shown in FIG. 10. FIG. 10 is a schematic cross-sectional view conceptually showing the internal structure of a ceramic plate in the ceramic heater shown in FIG. 19 is a schematic cross-sectional view showing the ceramic heater shown in FIG. 13; a schematic cross-sectional view conceptually showing the internal structure of the ceramic plate in the ceramic heater shown in FIG. 13; a schematic cross-sectional view conceptually showing another example of a conventional ceramic heater, corresponding to Example 6 (Comparative Example); a schematic cross-sectional view showing the ceramic heater shown in FIG. 16; a schematic cross-sectional view conceptually showing the internal structure of the ceramic plate in the ceramic heater shown in FIG. 16; a schematic cross-sectional view showing one embodiment of the positional relationship between the connecting member and the RF / ESC terminal hole in the ceramic heater according to the present invention; a schematic cross-sectional view showing the positional relationship between the connecting member and the RF / ESC terminal hole in the embodiment shown in FIG. 19; a schematic cross-sectional view showing the positional relationship between the connecting member and the RF / ESC terminal hole in the embodiment shown in FIG. 19; a schematic cross-sectional view showing another embodiment of the positional relationship between the connecting member and the RF / ESC terminal hole in the ceramic heater according to the present invention; a schematic top view showing an example of the arrangement of the connecting member in the embodiment shown in FIG. 22; The cross section AA of the configuration shown in FIG. 23 corresponds to FIG.24 is a schematic top view showing another example of the arrangement of the connecting members in the embodiment shown in Fig. 22. The A-A cross section of the configuration shown in Fig. 24 corresponds to Fig. 22. 25 is a schematic top view showing another example of the arrangement of the connecting members in the embodiment shown in Fig. 22. The A-A cross section of the configuration shown in Fig. 25 corresponds to Fig. 22.

[0013] The 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 deposition device. Typical examples of film deposition 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.

[0014] 1 to 3 show one embodiment of a ceramic heater. The ceramic heater 10 shown in FIGS. 1 and 2 includes a ceramic plate 12, a first RF / ESC electrode 14, a second RF / ESC electrode 16, RF / ESC rods 20, RF / ESC terminal holes 22, and a heater circuit 30. The ceramic plate 12 has a first surface 12a on which a wafer W is placed and a second surface 12b opposite the first surface 12a. The first RF / ESC electrode 14 is embedded in the ceramic plate 12 parallel to the first surface 12a. The second RF / ESC electrode 16 is electrically connected to the first RF / ESC electrode 14 and is embedded parallel to the first surface 12a at a depth farther from the first surface 12a of the ceramic plate 12 than the first RF / ESC electrode 14. One end of the RF / ESC rod 20 is electrically connected to the second RF / ESC electrode 16, and the other end extends from the second surface 12b to the outside of the ceramic plate 12. The RF / ESC terminal hole 22 is a bottomed hole provided in the thickness direction from the second surface 12b of the ceramic plate 12 toward the second RF / ESC electrode 16, and the tip portion of the RF / ESC rod 20 is inserted into the RF / ESC terminal hole 22. The heater circuit 30 is embedded in the ceramic plate 12 at a depth closer to the second surface 12b than the second RF / ESC electrode 16. The distance between the center lines of the first RF / ESC electrode 14 and the second RF / ESC electrode 16 is 2 to 7 mm. The distance from the first surface 12a to the bottom 22a of the RF / ESC terminal hole 22 is 4 to 9 mm. In this way, by (i) adopting a two-layer RF / ESC electrode structure including a first RF / ESC electrode 14 and a second RF / ESC electrode 16 that are electrically connected to each other and arranged in parallel, (ii) setting the distance between the center lines of the first RF / ESC electrode 14 and the second RF / ESC electrode 16 to 2 to 7 mm, and (iii) setting the distance from the first surface 12 a of the ceramic plate 12 to the hole bottom 22 a of the RF / ESC terminal hole 22 to 4 to 9 mm, it is possible to provide a ceramic heater 10 that is less susceptible to damage caused by temperature distribution in the center cool without impairing the function of the RF / ESC electrode 14.

[0015] That is, as mentioned above, when multiple terminals and terminal holes are concentrated in the center of the ceramic plate on which the wafer is placed, excessive tensile stress may be generated in the terminal holes of the ceramic plate if the ceramic heater experiences a center-cooled temperature distribution. In particular, stress tends to concentrate in RF / ESC terminal holes that are formed relatively deeper than the other terminal holes, which makes the ceramic heater more susceptible to damage near the RF / ESC terminal holes. That is, in the case of a peripheral hot or center-cooled temperature distribution, the thermal expansion of the plate's periphery is relatively greater than that of the plate's center, generating radial tensile stress as the plate's periphery pulls on the plate's center, and this tensile stress is applied to the RF / ESC terminal holes located in the plate's center. As is generally known, the deeper the hole, the greater the stress concentration factor, so stress tends to concentrate in deep RF / ESC terminal holes. In this regard, it is possible to reduce the RF / ESC terminal holes to avoid stress concentration. However, in this case, the depth of the RF / ESC electrodes from the wafer-mounting surface of the ceramic plate increases (e.g., from 1 mm to 3 mm), which increases impedance and significantly adversely affects plasma control by the RF electrodes and reduces the wafer chucking function of the ESC electrodes. These problems are successfully solved by the present invention. Specifically, the present invention employs a two-layer RF / ESC electrode structure including a first RF / ESC electrode 14 and a second RF / ESC electrode 16 arranged parallel to and spaced apart from each other. In this two-layer structure, the first RF / ESC electrode 14 can be positioned at a shallow position near the first surface 12 a, as in conventional RF / ESC electrodes, while the second RF / ESC electrode 16 (electrically connected to the first RF / ESC electrode 14) can be positioned at a deeper position (based on the first surface 12 a) than the first RF / ESC electrode 14, thereby ensuring electrical connection with the RF / ESC rods 20.In other words, while the desired RF / ESC electrode function can be ensured by the first RF / ESC electrode 14 in the same manner as in the conventional case, the second RF / ESC electrode 16 for electrical connection is disposed at a deeper position, so that the RF / ESC terminal hole 22 can be made shallower than in the conventional case (i.e., the bottom 22a of the RF / ESC terminal hole 22 can be brought closer to the second surface 12b). Since stress is less likely to concentrate in the shallowly formed RF / ESC terminal hole 22, the ceramic heater 10 is less likely to break near the RF / ESC terminal hole 22.

[0016] 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 various embedded components such as the first RF / ESC electrode 14, the second RF / ESC electrode 16, the connecting member 18, and the heater circuit 30, from the viewpoints of excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics similar to those of silicon.

[0017] 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 size of the ceramic plate 12 is not particularly limited and can be determined appropriately depending on the diameter of the wafer to be used. However, if the ceramic plate 12 is circular, the diameter is typically 150 to 450 mm, and particularly for 300 mm silicon wafers, the diameter is typically 320 to 380 mm. The thickness of the ceramic plate 12 is typically 10 to 25 mm.

[0018] The first RF / ESC electrode 14 is defined as an RF electrode and / or ESC electrode embedded in the ceramic plate 12 at a depth closer to the first surface 12a than the second RF / ESC electrode 16 and parallel to the first surface 12a. The first RF / ESC electrode 14 is preferably provided so as to encompass, in a plan view, the main area of ​​the ceramic plate 12 on which the wafer W is placed. The RF electrode enables film formation by a plasma CVD process when high frequency is applied. The ESC electrode is an abbreviation for electrostatic chuck (ESC) electrode and is also referred to as an electrostatic electrode. When a voltage is applied from an external power source, the ESC electrode chucks the wafer W 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, and may be, for example, 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 a high frequency to the ESC electrode, the ESC electrode can also be used as an RF electrode, and film formation can also be performed by a plasma CVD process. From the viewpoint of fully exhibiting the function as an RF / ESC electrode, the distance from the first surface 12a to the first RF / ESC electrode 14 is preferably 0.8 to 2.5 mm, more preferably 0.9 to 2.0 mm, and even more preferably 1.0 to 1.5 mm.

[0019] The second RF / ESC electrode 16 is defined as an RF electrode and / or ESC electrode electrically connected to the first RF / ESC electrode 14 and embedded in the ceramic plate 12 parallel to the first surface 12a at a depth farther from the first surface 12a than the first RF / ESC electrode 14. The second RF / ESC electrode 16 is preferably provided so as to overlap or be encompassed by the first RF / ESC electrode 14 in a plan view. Because the first RF / ESC electrode 14 primarily functions as an RF / ESC electrode in the two-layer RF / ESC electrode structure, the second RF / ESC electrode 16 is not expected to function as an RF / ESC electrode itself. Rather, it can be said that the second RF / ESC electrode 16 serves as a conductive member for ensuring electrical connection with the RF / ESC rods 20 at a position deeper than the first RF / ESC electrode 14 and supplying power to the first RF / ESC electrode 14. Therefore, an RF / ESC rod 20 for feeding power is electrically connected to the second RF / ESC electrode 16 (via an embedding member 24 and / or a buffer material 26 and / or an eyelet 28, as desired). The second RF / ESC electrode 16 is connected to an external power supply (not shown) via the RF / ESC rod 20. The metal constituting the RF / ESC rod 20 is not particularly limited, but preferred examples include Ni, W, Mo, and a joint structure of Ni and W, and more preferably W or Mo, which are paramagnetic materials with relatively low impedance.

[0020] Incidentally, a secondary effect of adopting a two-layer RF / ESC electrode structure is that the two RF / ESC electrodes 14, 16 increase the RF capture rate, thereby reducing the transmission of high-frequency RF waves and reducing RF noise in the heater circuit 30. In other words, the effect of reducing the RF current flowing into the heater circuit 30 is also achieved. Higher RF frequencies are expected to be the future trend, and the higher the frequency, the more easily the waves tend to pass through the RF electrodes. In this regard, the addition of the second RF / ESC electrode 16 is expected to have the effect of reducing the RF current in the heater circuit 30 by reducing RF noise.

[0021] The first RF / ESC electrode 14 and the second RF / ESC electrode 16 may be the same or different in terms of material, form, shape, size, etc. The first RF / ESC electrode 14 and / or the second RF / ESC electrode 16 preferably contain 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. Preferred examples of the form of the first RF / ESC electrode 14 and the second RF / ESC electrode 16 include mesh, punched metal, printed patterns, and combinations thereof. The first RF / ESC electrode 14 is preferably disk-shaped when viewed in a plan view. On the other hand, the second RF / ESC electrode 16 may be disk-shaped when viewed in a plan view, or may be a combination of annular and linear portions. In the combination of an annular portion and a linear portion, the linear portion is electrically connected to the RF / ESC rod 20, and the annular portion connected to the linear portion can supply power to the first RF / ESC electrode 14 (optionally via a connecting member 18), thereby achieving a space-efficient configuration. It is preferable that the first RF / ESC electrode 14 and the second RF / ESC electrode 16 have the same size or diameter when viewed from above, as shown in FIGS. 5 and 8 . However, as shown in FIGS. 2 and 11 , the size or diameter of the second RF / ESC electrode 16 may be smaller than that of the first RF / ESC electrode 14, or the size or diameter of the second RF / ESC electrode 16 may be larger than that of the first RF / ESC electrode 14. In other words, because the function as an RF / ESC electrode can basically be ensured by the first RF / ESC electrode 14, the size of the second RF / ESC electrode 16 is not particularly limited as long as the desired power supply function is ensured.

[0022] The distance between the center lines of the first RF / ESC electrode 14 and the second RF / ESC electrode 16 is 2 to 7 mm, preferably 3 to 6 mm, and more preferably 4 to 5 mm. Within this range, the second RF / ESC electrode 16 is positioned at a position sufficiently deeper than the first RF / ESC electrode 14, allowing the RF / ESC terminal hole 22 to be shallower (i.e., the hole bottom 22a to be closer to the second surface 12b). As described above, this reduces stress concentration in the RF / ESC terminal hole 22, making the ceramic heater 10 less susceptible to damage. Here, the distance between the center lines of the first RF / ESC electrode 14 and the second RF / ESC electrode 16 refers to the distance between the center line parallel to the first surface 12a and passing through the center of the first RF / ESC electrode 14 in the thickness direction, and the center line parallel to the first surface 12a and passing through the center of the second RF / ESC electrode 16 in the thickness direction, when the ceramic plate 12 is viewed in cross section.

[0023] A connecting member 18 that electrically connects the first RF / ESC electrode 14 and the second RF / ESC electrode 16 is preferably provided between the first RF / ESC electrode 14 and the second RF / ESC electrode 16. Use of the connecting member 18 makes it possible to simply and reliably ensure electrical connection between the first RF / ESC electrode 14 and the second RF / ESC electrode 16, which are buried at different depths. The connecting member 18 is not particularly limited as long as it can ensure electrical connection between the first RF / ESC electrode 14 and the second RF / ESC electrode 16. Preferably, the connecting member 18 is at least one member selected from the group consisting of a coil, a metal tablet, and a metal mesh laminate. When the connecting member 18 is a coil, as shown in FIGS. 1 to 6 and 10 to 12, the coil is preferably arranged horizontally so that the longitudinal direction of the coil follows the outer periphery of the second RF / ESC electrode 16, since this increases the number of contact points between the first RF / ESC electrode 14 and the second RF / ESC electrode 16. However, multiple coils may be arranged vertically. When the connecting member 18 is a metal tablet and / or a metal mesh laminate, it is preferable to arrange a plurality of metal tablets and / or metal mesh laminates so as to be located on the outer periphery of the second RF / ESC electrode 16, as shown in Figures 7 to 9. The metal tablet is a mass of metal, and the metal mesh laminate is a stack of a plurality of metal meshes. More preferably, the plurality of metal tablets and / or metal mesh laminates are arranged at equal intervals in the circumferential direction (e.g., rotationally symmetrical about the central axis of the ceramic plate 12). In either embodiment, the connecting member 18 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, a tungsten carbide-aluminum oxide composite, and niobium.

[0024] In a preferred embodiment of the present disclosure, as shown in FIGS. 19 to 21 , the connecting member 18 can be positioned so as to at least partially (i.e., partially or entirely) overlap the RF / ESC terminal hole 22 when the ceramic plate 12 is viewed from above. In this embodiment, as shown in FIG. 19 , the connecting member 18 is positioned above the RF / ESC terminal hole 22, which has the advantage of reducing the area occupied by the second RF / ESC electrode 16 and resulting in a compact and simple configuration suitable for space saving. The connecting member 18 may be positioned in any manner as long as it can electrically connect the first RF / ESC electrode 14 and the second RF / ESC electrode 16. For example, as shown in FIG. 20 , when the ceramic plate 12 is viewed from above, a coil serving as the connecting member 18 may be positioned in a direction that crosses the RF / ESC terminal hole 22 or the embedded member 24 (e.g., in the direction of their diameter). Alternatively, as shown in FIG. 21 , a coil serving as the connecting member 18 may be arranged such that the central axis of the coil is aligned along the outer periphery of the RF / ESC terminal hole 22 or the embedded member 24 (for example, in the circumferential direction).

[0025] In another preferred embodiment of the present disclosure, as shown in FIGS. 22 to 25 , the connecting member 18 can be positioned so as not to overlap the RF / ESC terminal hole 22 (i.e., positioned away from the RF / ESC terminal hole 22) when the ceramic plate 12 is viewed from above. In this embodiment, as shown in FIG. 22 , the connecting member 18 is not positioned above the RF / ESC terminal hole 22, which has the advantage of making it easier to ensure the integrity of the ceramic base above and around the RF / ESC terminal hole 22, where stress is likely to concentrate and cause breakage, and thus making it possible to achieve a more robust configuration. The connecting member 18 may be positioned in any manner as long as it can electrically connect the first RF / ESC electrode 14 and the second RF / ESC electrode 16. For example, as shown in FIGS. 23 and 24 , multiple coils serving as the connecting member 18 may be arranged in a polygonal shape surrounding the RF / ESC terminal hole 22 when the ceramic plate 12 is viewed from above. In this case, the multiple coils arranged on the polygon may be spaced apart without touching each other, as shown in FIG. 23 , or may be connected to each other at their ends, as shown in FIG. 24 . That is, as can be seen from FIG. 22 , the connecting member 18 ensures electrical connection between the first RF / ESC electrode 14 and the second RF / ESC electrode 16 in the thickness direction of the ceramic plate 12, so there is no problem even if the multiple coils are spaced apart when the ceramic plate 12 is viewed from above. The polygon formed by the multiple coils is not limited to the triangle shown in the illustration, but may be any polygon, such as a square or pentagon. Alternatively, as shown in FIG. 25 , when the ceramic plate 12 is viewed from above, the multiple coils serving as the connecting member 18 may be arranged parallel to each other so that the RF / ESC terminal holes 22 are located between them. In this case, the number of coils is not limited to two as shown in the illustration, but may be any number, such as three or four.

[0026] The RF / ESC terminal hole 22 is a bottomed hole into which the tip portion of the RF / ESC rod 20 is inserted, and is provided in the thickness direction from the second surface 12b of the ceramic plate 12 toward the second RF / ESC electrode 16. The RF / ESC terminal hole 22 does not need to reach the RF / ESC rod 20 as long as electrical connection between the RF / ESC rod 20 and the second RF / ESC electrode 16 is ensured. Preferably, an embedded member 24 is embedded in the ceramic plate 12 between a hole bottom 22a of the RF / ESC terminal hole 22 and the second RF / ESC electrode 16, and the embedded member 24 electrically connects the RF / ESC rod 20 and the second RF / ESC electrode 16. In this case, the RF / ESC terminal hole 22 is preferably provided so as to reach the embedded member 24 from the second surface 12b.

[0027] The distance from the first surface 12a to the bottom 22a of the RF / ESC terminal hole 22 is 4 to 9 mm, preferably 5 to 9 mm, and more preferably 6 to 9 mm. Within this range, the RF / ESC terminal hole 22 becomes shallow (i.e., the bottom 22a of the hole is closer to the second surface 12b). As described above, this reduces the stress concentration on the RF / ESC terminal hole 22, making the ceramic heater 10 less likely to break. The depth of the RF / ESC terminal hole 22 (the distance from the second surface 12b to the bottom 22a) is not particularly limited, but is typically 6 to 16 mm, more typically 8 to 13 mm, and even more typically 8 to 11 mm or 11 to 13 mm.

[0028] The embedded member 24 is preferably a massive metal member (configured in, for example, a mesh shape) for easily ensuring electrical connection with the second RF / ESC electrode 16, and can be provided in contact with the second RF / ESC electrode 16. This ensures a sufficient contact area for brazing the RF / ESC rod 20 or the buffer material 26 (described later). Preferred examples of the metal constituting the embedded member 24 include Mo, W, and a W-Mo alloy, with Mo being preferred.

[0029] A buffer material 26 may be provided between the hole bottom 22a of the RF / ESC terminal hole 22 and the second RF / ESC electrode 16 or the embedded member 24. The buffer material 26 is a metal member provided as a buffer for alleviating the difference in thermal expansion between the embedded member 24 and the RF / ESC rod 20, and is provided between the embedded member 24 and the RF / ESC rod 20. A preferred example of the metal constituting the buffer material 26 is an alloy such as Kovar (registered trademark) (Fe—Ni—Co alloy).

[0030] The eyelet 28 is a metallic cylindrical member that is housed in or fitted into the RF / ESC terminal hole 22. The eyelet 28 serves to guide the RF / ESC rod 20 for smooth insertion into the RF / ESC terminal hole 22. The eyelet 28 may be threaded. In this case, by threading the RF / ESC rod 20 as well, the RF / ESC rod 20 can be inserted while threaded into the eyelet 28. The metal constituting the eyelet 28 is not particularly limited, but preferred examples include Ni, W, Mo, and W-Mo alloys, with Ni being preferred. The eyelet 28 may also have a male thread on its outer periphery. Providing a threaded portion allows the RF / ESC terminal hole 22 and the eyelet 28 to be threadedly engaged.

[0031] When at least one selected from the embedding member 24, the buffer material 26, and the eyelet 28 is used, it is preferable to braze the RF / ESC rod 20, the embedding member 24, the buffer material 26, and / or the eyelet 28 to each other.

[0032] The heater circuit 30 is embedded in the ceramic plate 12 at a depth closer to the second surface 12b than the second RF / ESC electrode 16. The heater circuit 30 is not particularly limited, but may be, for example, a conductive coil wired in a single stroke across the entire ceramic plate 12. The single-stroke shape may be various known shapes, such as alternating forward and backward movements or a spiral shape. Heater rods 32 are connected to both ends of the heater circuit 30 (optionally via an embedded member 36 and / or a buffer material 38 and / or an eyelet 40) for power supply, and are inserted into heater terminal holes 34. The heater rods 32 are connected to a heater power supply (not shown) through an internal space S of the ceramic shaft 46. One end of each heater rod 32 is electrically connected to the heater circuit 30, and the other end may be configured to extend from the second surface 12b. When power is supplied from the heater power supply, the heater circuit 30 generates heat to heat the wafer W placed on the first surface 12a. The heater circuit 30 is not limited to a coil, and may be, for example, a ribbon (a thin, elongated plate) or a mesh. The heater rod 32, the embedding member 36, the buffer material 38, and the eyelet 40 may be similar to the RF / ESC rod 20, the embedding member 24, the buffer material 26, and the eyelet 28. When at least one selected from the embedding member 36, the buffer material 38, and the eyelet 40 is used, it is preferable to braze the heater rod 32, the embedding member 36, the buffer material 38, and / or the eyelet 40 to each other.

[0033] 11 to 13 , the ceramic plate 12 may be provided with a third RF / ESC electrode 54 in addition to the RF / ESC electrode structure including the first RF / ESC electrode 14 and the second RF / ESC electrode 16. The RF / ESC electrode structure including the first RF / ESC electrode 14 and the second RF / ESC electrode 16 can cover the region of the ceramic plate 12 where the wafer W is placed (hereinafter referred to as the main region), but it is difficult to cover the outer periphery of the ceramic plate 12 (particularly the raised portion on the first surface 12 a). Therefore, by separately providing the third RF / ESC electrode 54 on the outer periphery of the ceramic plate 12 (particularly the raised portion on the first surface 12 a), it is possible to achieve the desired RF and / or ESC functions even in the outer periphery (particularly the raised portion). In this embodiment, a peripheral RF / ESC electrode structure can be configured in a manner similar to the main region RF / ESC electrode structure. For example, the peripheral RF / ESC electrode structure may be composed of a third RF / ESC electrode 54, a jumper 56, and a connecting member 58. The third RF / ESC electrode 54 has an annular shape in plan view and is embedded in the peripheral portion of the ceramic plate 12 (particularly, in the raised portion on the first surface 12 a). The jumper 56 may be linear in plan view, or may be a combination of an annular portion and a linear portion. The connecting member 58 electrically connects the third RF / ESC electrode 54 and the jumper 56. As shown in FIG. 12 , an RF / ESC rod 60 may be inserted into an RF / ESC terminal hole 62, and the linear jumper 56 a electrically connected to the RF / ESC rod 60 (optionally via an embedding member 64 and / or a buffer material 66 and / or an eyelet 68) may extend in the peripheral direction and connect to the annular jumper 56 b, and the annular jumper 56 b and the third RF / ESC electrode 54 may be electrically connected via the connecting member 58.

[0034] Like the first RF / ESC electrode 14 and the second RF / ESC electrode 16, the third RF / ESC electrode 54 and / or the jumper 56 (e.g., the linear jumper 56a and the annular jumper 56b) preferably contain at least one material selected from the group consisting of tungsten, molybdenum, a tungsten-molybdenum alloy, tungsten carbide, a tungsten carbide-titanium nitride composite, a tungsten carbide-aluminum oxide composite, and niobium. Like the connecting member 18, the connecting member 58 is not particularly limited as long as it is a material capable of ensuring electrical connection between the third RF / ESC electrode 54 and the jumper 56, but is preferably at least one material selected from the group consisting of a coil, a metal tablet, and a metal mesh laminate. Like the connecting member 18, the connecting member 58 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, a tungsten carbide-aluminum oxide composite, and niobium. Furthermore, the RF / ESC rod 60, the embedded member 64, the buffer material 66, and the eyelet 68 can have the same configuration as the above-described RF / ESC rod 20, the embedded member 24, the buffer material 26, and the eyelet 28. When at least one selected from the embedded member 64, the buffer material 66, and the eyelet 68 is used, it is preferable to braze the RF / ESC rod 60, the embedded member 64, the buffer material 66, and / or the eyelet 68 to one another.

[0035] The second surface 12b of the ceramic plate 12 may be provided with a temperature measurement hole 42. The temperature measurement hole 42 may be a thermocouple hole for temperature measurement, which is commonly used in ceramic heaters. Therefore, by inserting a thermocouple 44 or a resistance thermometer into the temperature measurement hole 42, the temperature of the ceramic plate 12 can be measured. The temperature measurement hole 42 may be a vertical hole, a horizontal hole, or a combination thereof, and may be formed to fit the area whose temperature is to be measured.

[0036] Optionally, a ceramic shaft 46 may be attached to the second surface 12b of the ceramic plate 12. The ceramic shaft 46 is a cylindrical member with an internal space S and may have a configuration similar to that of ceramic shafts used in known ceramic heaters. The internal space S is configured to allow elongated components such as the RF / ESC rod 20, heater rod 32, and thermocouple 44 to pass therethrough. The ceramic shaft 46 is preferably made of the same ceramic material as the ceramic plate 12. Therefore, the ceramic shaft 46 preferably contains aluminum nitride or aluminum oxide, more preferably aluminum nitride. The upper end surface of the ceramic shaft 46 is preferably joined to the second surface 12b of the ceramic plate 12 by solid-state bonding or diffusion bonding. The outer diameter of the ceramic shaft 46 is not particularly limited, but is preferably 40 to 60 mm. The inner diameter of the ceramic shaft 46 (the diameter of the internal space S) is also not particularly limited, but is preferably 33 to 55 mm.

[0037] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0038] Example 1 (1) Fabrication of Ceramic Heater Using the components shown below, a ceramic heater 10 having the structure shown in FIGS. 1 to 3 and satisfying the conditions shown in Table 1 was fabricated by a known procedure.

[0039] <Constituent members and their specifications> Ceramic plate 12: disc-shaped sintered aluminum nitride (diameter: 330 mm, thickness: 20 mm (including 1 mm height of raised portion)) (first RF / ESC electrode 14, second RF / ESC electrode 16, connecting member 18, embedded members 24, 36, heater circuit 30, etc. are embedded inside) First RF / ESC electrode 14: disc-shaped molybdenum electrode with a diameter of 320 mm, embedded at a position 1.0 mm deep from the first surface 12 a of the ceramic plate 12 Second RF / ESC electrode 16: plate-shaped molybdenum electrode with a diameter of 95 mm, embedded at a position 5.0 mm deep from the first surface 12 a of the ceramic plate 12 Connecting member 18: molybdenum coil arranged laterally so that the longitudinal direction of the coil follows the outer periphery of the second RF / ESC electrode 16 RF / ESC rod 20: nickel terminal rod RF / ESC terminal hole 22: a bottomed hole having a nominal diameter of 7 mm (M7) and a depth of 13 mm (distance from first surface 12 a to hole bottom 22 a: 6 mm) Embedded member 24: a metal tablet made of molybdenum Cushioning materials 26, 38: metal parts made of Kovar (registered trademark) (Fe—Ni—Co alloy) Eyelets 28, 40: cylindrical members made of nickel Heater circuit 30: a coil-shaped resistance heating element made of molybdenum embedded at a position 10 mm deep from first surface 12 a according to a predetermined circuit pattern that can achieve a temperature distribution of outer periphery hot and center cool Heater rod 32: two terminal rods made of nickel Heater terminal hole 34: a bottomed hole having a nominal diameter of 7 mm (M7) and a depth of 7 mm Embedded member 36: a spherical member made of molybdenum Ceramic shaft 46: a cylindrical sintered aluminum nitride body (height: 172 mm, outer diameter: 42 mm, inner diameter: 36 mm)

[0040] (2) Evaluation Various evaluations were carried out on the obtained ceramic heater.

[0041] <Cycle Test> The ceramic heater 10 was installed in the chamber of a film forming apparatus. The chamber was evacuated and N ２ Introduce N gas into the chamber. ２The gas pressure was 5 Torr. The ceramic heater 10 was heated from room temperature (20°C) to a set temperature of 550°C by supplying power to the heater circuit 30 via the heater rod 32, buffer material 38, and embedded member 36. At this set temperature, the temperature distribution on the first surface 12a of the ceramic plate 12 was measured using an infrared camera. The power supplied to the heater circuit 30 was then adjusted so that the temperature at the periphery of the wafer placement area was at most 25°C higher than the center (hereinafter referred to as a 25°C center-cooled state). The power supply was then stopped and the ceramic heater 10 was allowed to cool to room temperature (20°C). The temperature increase rate was increased and a heat-reflecting ring was placed around the periphery of the ceramic heater 10 to facilitate achieving a 25°C center-cooled state. This cycle of increasing the temperature from 20°C to 550°C and then cooling to 20°C was repeated a total of 100 times. Thereafter, the presence or absence of cracks in the ceramic plate 12 was examined using an ultrasonic flaw detector, and as shown in Table 1, it was confirmed that no cracks due to center cooling or temperature rise and fall had occurred.

[0042] <Stress Analysis> A center-cooled state of the ceramic heater 10 at 25°C with a set temperature of 550°C was reproduced by computer simulation using commercially available analysis software Ansys (manufactured by Ansys Inc.), and thermal stress analysis was performed. The thermal stress in the vicinity of the RF / ESC terminal hole 22 obtained by the analysis was as shown in Table 1.

[0043] Example 2 A ceramic heater 10 was fabricated in the same manner as in Example 1 using a known procedure, except that it had the structure shown in FIGS. 4 to 6 and satisfied the conditions shown in Table 1. That is, a ceramic heater 10 having the same structure as in Example 1 was fabricated except that (i) a disk-shaped molybdenum electrode having the same diameter as the first RF / ESC electrode 14 was used as the second RF / ESC electrode 16 and embedded at a depth of 3.0 mm from the first surface 12 a of the ceramic plate 12, and (ii) a bottomed hole with a nominal diameter of 7 mm (M7) and a depth of 15 mm (distance from the first surface 12 a to the hole bottom 22 a: 4 mm) was formed as the RF / ESC terminal hole 22. The fabricated ceramic heater 10 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0044] Example 3 A ceramic heater 10 was fabricated in the same manner as in Example 1 using a known procedure, except that it had a structure as shown in FIGS. 7 to 9 and satisfied the conditions shown in Table 1. That is, a ceramic heater 10 having the same structure as in Example 1 was fabricated except that (i) a disk-shaped molybdenum electrode having the same diameter as the first RF / ESC electrode 14 was used as the second RF / ESC electrode 16 and embedded at a depth of 8.0 mm from the first surface 12 a of the ceramic plate 12, (ii) a bottomed hole with a nominal diameter of 7 mm (M7) and a depth of 10 mm (the distance from the first surface 12 a to the hole bottom 22 a: 9 mm) was formed as the RF / ESC terminal hole 22, and (iii) instead of a coil, four laminates each made of multiple layers of molybdenum mesh were arranged equidistantly and rotationally symmetrically around the outer periphery of the second RF / ESC electrode 16. The fabricated ceramic heater 10 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0045] Example 4 A ceramic heater 10 was produced in the same manner as in Example 1 by a known procedure, except that the ceramic heater 10 had a structure as shown in FIGS. 10 to 12, satisfied the conditions shown in Table 1, and had a thickness of 21 mm (including a height of 2 mm for the raised portion). That is, a ceramic heater 10 having the same structure as in Example 1 was fabricated, except that (i) the thickness of the ceramic plate 12 was 21 mm, (ii) a disk-shaped molybdenum electrode having a diameter of 80 mm was used as the second RF / ESC electrode 16 and was embedded in the ceramic plate 12 at a position 6.0 mm deep from the first surface 12 a, (iii) a bottomed hole having a nominal diameter of 7 mm (M7) and a depth of 12 mm (distance from the first surface 12 a to the hole bottom 22 a: 7 mm) was formed as the RF / ESC terminal hole 22, and (iv) an outer periphery RF / ESC electrode structure consisting of a circular third RF / ESC electrode 54, a jumper 56, and a connecting member 58 was embedded so that the third RF / ESC electrode 54 was positioned within a raised portion on the outer periphery of the ceramic plate 12, and an RF / ESC terminal hole 62, an embedded member 64, an RF / ESC rod 60, a buffer material 66, and an eyelet 68 were additionally provided.

[0046] At this time, the ceramic heater 10 was configured so that the linear jumper 56a, which was electrically connected to the RF / ESC rod 60 inserted into the RF / ESC terminal hole 62 via an embedded member 64 and a buffer material 66, extended in the outer circumferential direction and connected to the annular jumper 56b, and the annular jumper 56b and the third RF / ESC electrode 54 were electrically connected via a connecting member 58. The specifications of the components added in this example are as follows:

[0047] <Additional components and their specifications> Third RF / ESC electrode 54: an annular molybdenum electrode embedded in the raised portion of the ceramic plate 12 at a depth of 1.0 mm from the first surface 12 a. Linear jumper 56 a: a linear molybdenum layer embedded in the ceramic plate 12 at a depth of 6.0 mm from the first surface 12 a. Annular jumper 56 b: an annular molybdenum layer embedded in the ceramic plate 12 at a depth of 6.0 mm from the first surface 12 a and connected to the linear jumper 56 a. Connection member 58: a molybdenum coil disposed laterally so that the longitudinal direction of the coil follows the outer periphery of the annular jumper 56 b. RF / ESC rod 60: a nickel terminal rod. RF / ESC terminal hole 62: nominal diameter 7 mm (M7), depth 12 mm (distance from the first surface 12 a to the hole bottom 62 a: 7 mm) Embedded member 64: a metal tablet made of molybdenum. Cushioning material 66: a metal part made of Kovar (registered trademark) (Fe—Ni—Co alloy). Eyelet 68: a cylindrical member made of nickel.

[0048] The produced ceramic heater 10 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0049] Example 5 (Comparison) A conventional ceramic heater 110 was fabricated in the same manner as in Example 1 using known procedures, except that it had the structure shown in Figures 13 and 14 and satisfied the conditions shown in Table 1. That is, a ceramic heater 10 was fabricated having the same structure as in Example 1, except that (i) the second RF / ESC electrode 16 and the connecting member 18 were eliminated, and (ii) a bottomed hole with a nominal diameter of 7 mm (M7) and a depth of 17 mm (distance from the first surface 12a to the hole bottom 22a: 2 mm) was formed as the RF / ESC terminal hole 22. The fabricated conventional ceramic heater 110 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0050] 15 to 18 , and satisfying the conditions shown in Table 1, the ceramic plate 12 had a thickness of 20 mm (including the height of the raised portion of 1 mm). That is, a ceramic heater 10 having a structure similar to that of Example 4 was fabricated by a known procedure. The ceramic heater 10 had a structure similar to that of Example 4, except that (i) the thickness of the ceramic plate 12 was 20 mm, (ii) the second RF / ESC electrode 16 and the connecting member 18 were eliminated, (iii) the RF / ESC terminal hole 22 was formed as a bottomed hole with a nominal diameter of 7 mm (M7) and a depth of 17 mm (the distance from the first surface 12 a to the hole bottom 22 a: 2 mm), and (iv) the jumper 56 consisted only of a strip-shaped linear jumper 56 a, which linearly extended from the embedded member 64 in two opposite directions and was electrically connected to the third RF / ESC electrode 54 via the connecting member 58. The conventional ceramic heater 110 thus produced was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0051]

[0052] REFERENCE SIGNS LIST 10 Ceramic heater 12 Ceramic plate 12a First surface 12b Second surface 14 First RF / ESC electrode 16 Second RF / ESC electrode 18, 58 Connecting member 20, 60 RF / ESC rod 22, 62 RF / ESC terminal hole 22a, 62a Hole bottom 24, 36, 64 Buried member 26, 38, 66 Cushioning material 28, 40, 68 Eyelet 30 Heater circuit 32 Heater rod 34 Heater terminal hole 42 Temperature measurement hole 44 Thermocouple 46 Ceramic shaft 54 ​​Third RF / ESC electrode 56 Jumper 56a Linear jumper 56b Ring-shaped jumper W Wafer S Internal space

Claims

1. A ceramic heater comprising: a ceramic plate having a first surface on which a wafer is placed and a second surface opposite the first surface; a first RF / ESC electrode embedded in the ceramic plate parallel to the first surface; a second RF / ESC electrode electrically connected to the first RF / ESC electrode and embedded in the ceramic plate parallel to the first surface at a depth farther from the first surface than the first RF / ESC electrode; an RF / ESC rod having one end electrically connected to the second RF / ESC electrode and the other end extending from the second surface to the outside of the ceramic plate; an RF / ESC terminal hole which is a bottomed hole provided in the thickness direction from the second surface of the ceramic plate toward the second RF / ESC electrode, and into which a tip portion of the RF / ESC rod is inserted; and a heater circuit embedded in the ceramic plate at a depth closer to the second surface than the second RF / ESC electrode, a distance between center lines of the first RF / ESC electrode and the second RF / ESC electrode of 2 to 7 mm; and a distance from the first surface to a bottom of the RF / ESC terminal hole of 4 to 9 mm.

2. The ceramic heater according to claim 1, further comprising a connecting member located between the first RF / ESC electrode and the second RF / ESC electrode within the ceramic plate, for electrically connecting the first RF / ESC electrode and the second RF / ESC electrode.

3. The ceramic heater according to claim 2, wherein the connecting member is at least one selected from the group consisting of a coil, a metal tablet, and a metal mesh laminate.

4. A ceramic heater according to any one of claims 1 to 3, wherein the ceramic plate comprises aluminum nitride or aluminum oxide.

5. The ceramic heater according to any one of claims 1 to 3, wherein the first RF / ESC electrode and / or the second RF / ESC electrode 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.

6. The ceramic heater according to claim 2 or 3, wherein the connecting member 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.

7. A ceramic heater according to claim 2 or 3, wherein the connecting member is arranged at a position that at least partially overlaps the RF / ESC terminal hole when the ceramic plate is viewed from above.

8. A ceramic heater according to claim 2 or 3, wherein the connecting member is disposed at a position that does not overlap with the RF / ESC terminal hole when the ceramic plate is viewed from above.

9. A ceramic heater according to any one of claims 1 to 3, further comprising a cylindrical ceramic shaft attached to the second surface of the ceramic plate and having an internal space.

10. A ceramic heater according to any one of claims 1 to 3, wherein, when viewed in plan, the first RF / ESC electrode is disc-shaped, and the second RF / ESC electrode is either disc-shaped or a combination of an annular portion and a linear portion.

11. A ceramic heater according to any one of claims 1 to 3, wherein each of the first RF / ESC electrode and the second RF / ESC electrode is in at least one form selected from the group consisting of a mesh, a punched metal, and a printed pattern.

12. The ceramic heater according to any one of claims 1 to 3, further comprising a heater rod having one end electrically connected to the heater circuit and the other end extending from the second surface to the outside of the ceramic plate.

13. A ceramic heater according to any one of claims 1 to 3, further comprising an embedded member embedded in the ceramic plate between the bottom of the RF / ESC terminal hole and the second RF / ESC electrode, electrically connecting the RF / ESC rod and the second RF / ESC electrode.

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