Ceramic heater

Abstract

To provide a ceramic heater with a shaft that can significantly improve the uniform heating of a ceramic plate.SOLUTION: A ceramic heater includes a ceramic plate having a first surface and a second surface and having a heater electrode embedded therein, a ceramic shaft attached to the second surface of the ceramic plate, a shaft hole formed through a side wall constituting the ceramic shaft, a vacuum suction groove formed in the second surface of the ceramic plate and / or the upper end surface of the ceramic shaft so as to extend circumferentially and forming a vacuum suction path together with the upper end surface and / or the second surface and communicating with the shaft hole, and a through hole formed through the ceramic plate in the thickness direction, communicating with the shaft hole and / or the vacuum suction groove and reaching the first surface. In a plan view, the area of the vacuum suction groove accounts for 60 to 96% of the total area of the joint between the ceramic shaft and the second surface and the vacuum suction groove.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 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.

[0003] Patent Document 1 (Japanese Patent No. 7352765) discloses a ceramic heater including a ceramic heater plate in which a heating element is embedded, a shaft connected to the underside of the heater plate, and continuous or intermittent air pockets provided along the joint surface between the heater plate and the shaft. The air pockets include grooves, which are formed in the heater plate along the joint surface at the bent portion of the upper end of the shaft that joins to the heater plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7352765 Summary of the Invention

[0005] To ensure high-quality film formation, ceramic heaters are required to have small temperature differences 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. However, as shown schematically in FIG. 17 , in a conventional shaft-equipped ceramic heater 110, in addition to heat transfer from the entire ceramic plate 112 due to radiation and convection (see arrow B), heat also transfers from the ceramic shaft 114 attached to the back surface of the ceramic plate 112 to the equipment side due to thermal conduction (see arrow A). As a result, heat transfer from the shaft portion of the ceramic heater 110 is increased, and the temperature of the center of the ceramic plate 112 tends to be lower than that of other portions, resulting in a loss of thermal uniformity.

[0006] The inventors have now discovered that by providing vacuum suction grooves at a predetermined area ratio along the joint surface of the ceramic plate and the ceramic shaft to enable vacuum suction, heat dissipation through the ceramic shaft (particularly from the lower end of the shaft) can be effectively suppressed, thereby significantly improving the thermal uniformity of the ceramic plate.

[0007] Therefore, an object of the present invention is to provide a ceramic heater with a shaft that can effectively suppress heat radiation through the ceramic shaft (particularly from the lower end of the shaft), thereby significantly improving the thermal uniformity of the ceramic plate.

[0008] According to the present disclosure, the following aspects are provided. [Aspect 1] a circular ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface, and having a heater electrode embedded therein; a cylindrical ceramic shaft attached to a second surface of the ceramic plate; a shaft hole formed in a side wall of the ceramic shaft, the shaft hole penetrating from one end to the other end of the ceramic shaft; a vacuum suction groove provided on the second surface of the ceramic plate and / or the upper end surface of the ceramic shaft so as to extend in a circumferential direction, the vacuum suction groove forming a vacuum suction path communicating with the shaft hole together with the upper end surface and / or the second surface; a through hole penetrating the ceramic plate in a thickness direction, the through hole communicating with the shaft hole and / or the vacuum suction groove and provided to reach the first surface; A ceramic heater comprising: the ceramic heater is configured so that, when the shaft hole is vacuum-suctioned, the first surface of the ceramic plate can be vacuum-suctioned through the shaft hole, the vacuum suction groove, and the through-hole; A ceramic heater, wherein, when viewed in a plan view in the central axis direction of the ceramic shaft, the ratio of the area of ​​the vacuum suction groove to the total area of ​​the joint portion between the ceramic shaft and the second surface and the vacuum suction groove is 60 to 96%. [Aspect 2] 2. The ceramic heater according to aspect 1, wherein the ratio of the area of ​​the vacuum suction groove to the total area of ​​the joint portion between the ceramic shaft and the second surface and the vacuum suction groove is 65 to 85%. [Aspect 3] 3. The ceramic heater according to aspect 1 or 2, wherein the shaft hole and the through hole are arranged to overlap each other when viewed in a plan view in the direction of the central axis of the ceramic shaft. [Aspect 4] 4. The ceramic heater according to any one of aspects 1 to 3, wherein the vacuum suction groove has a depth of 0.5 to 30 mm. [Aspect 5] 5. The ceramic heater according to any one of aspects 1 to 4, wherein the width of each of the joints between the ceramic shaft and the second surface is 0.5 to 3.0 mm. [Aspect 6] The ceramic heater according to any one of aspects 1 to 5, wherein the ceramic heater includes a plurality of the through holes, the plurality of through holes being arranged in rotational symmetry with respect to the central axis of the ceramic shaft. [Aspect 7] 7. The ceramic heater according to claim 6, wherein the number of the through holes is two or three. [Aspect 8] The vacuum suction groove is provided in a plurality, The through-hole is located at an end in the longitudinal direction of each of the plurality of vacuum suction grooves, A ceramic heater according to aspect 6 or 7, wherein the plurality of vacuum suction grooves are spaced apart from one another in the circumferential direction. [Aspect 9] A ceramic heater according to any one of aspects 1 to 8, wherein the number of the vacuum suction grooves is two or three. [Aspect 10] 10. The ceramic heater according to any one of aspects 1 to 9, wherein the vacuum suction groove is provided in an annular or arcuate shape. [Aspect 11] 11. The ceramic heater according to any one of aspects 1 to 10, wherein the vacuum suction groove is provided so as to extend in a circumferential direction while meandering. [Aspect 12] 12. The ceramic heater according to any one of aspects 1 to 11, wherein the vacuum suction grooves are formed in a pattern including circumferentially advancing, turning back, and circumferentially advancing backward. [Aspect 13] 13. The ceramic heater according to any one of aspects 1 to 12, wherein the cross-sectional shape of the vacuum suction groove is at least one selected from the group consisting of a rectangle, a trapezoid, a semicircle, and a diamond. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing an example of a ceramic heater according to the present invention. [Figure 2] 2 is a schematic cross-sectional view showing an example of the shape of a vacuum suction groove and a through hole in a plan view, and corresponds to a cross-sectional view taken along line AA in FIG. 1. FIG. [Figure 3] FIG. 10 is a schematic cross-sectional view showing another example of the shape of the vacuum suction groove and the through hole in a plan view. [Figure 4] FIG. 10 is a schematic cross-sectional view showing another example of the shape of the vacuum suction groove and the through hole in a plan view. [Figure 5]FIG. 10 is a schematic cross-sectional view showing another example of the shape of the vacuum suction groove and the through hole in a plan view. [Figure 6] FIG. 10 is a schematic cross-sectional view showing another example of the shape of the vacuum suction groove and the through hole in a plan view. [Figure 7] 5A and 5B are schematic cross-sectional views showing examples of cross-sectional shapes of vacuum suction grooves and through holes. [Figure 8] 10A and 10B are schematic cross-sectional views showing other examples of the cross-sectional shapes of the vacuum suction grooves and the through holes. [Figure 9] 10A and 10B are schematic cross-sectional views showing other examples of the cross-sectional shapes of the vacuum suction grooves and the through holes. [Figure 10] 10A and 10B are schematic cross-sectional views showing other examples of the cross-sectional shapes of the vacuum suction grooves and the through holes. [Figure 11] FIG. 1 is a schematic cross-sectional view showing a ceramic heater produced in Example 1 (Comparative Example). [Figure 12] FIG. 1 is a schematic cross-sectional view showing the ceramic heaters produced in Examples 2 to 13. [Figure 13] 1 is a graph showing the improvement rate of thermal uniformity measured for the ceramic heaters produced in Examples 1 to 6 in relation to the width of the bonded portion. [Figure 14] 1 is a graph showing the rate of decrease in shaft end heat radiation amount and the rate of decrease in shaft end temperature measured for the ceramic heaters produced in Examples 1 to 6, in relation to the width of the bonded portion. [Figure 15] 1 is a graph showing the percentage improvement in thermal uniformity measured for the ceramic heaters produced in Examples 1, 7, 3, 8 and 9 as a function of the width of the bonded portion. [Figure 16] 1 is a graph showing the rate of decrease in shaft end heat radiation amount and the rate of decrease in shaft end temperature measured for the ceramic heaters produced in Examples 1, 7, 3, 8 and 9, in relation to the width of the joint portion. [Figure 17] FIG. 1 is a schematic cross-sectional view showing an example of a conventional ceramic heater. DETAILED DESCRIPTION OF THE INVENTION

[0010] The ceramic heater according to the present invention is a ceramic pedestal for supporting a wafer in a semiconductor manufacturing apparatus while controlling its temperature. Typically, the ceramic heater according to the present invention can be a ceramic heater for a semiconductor film formation apparatus. Typical examples of film formation apparatuses include CVD (chemical vapor deposition) apparatuses (e.g., thermal CVD apparatuses, plasma CVD apparatuses, photo CVD apparatuses, and MOCVD apparatuses) and PVD (physical vapor deposition) apparatuses.

[0011] FIG. 1 shows one embodiment of a ceramic heater. The ceramic heater 10 shown in FIG. 1 includes a ceramic plate 12, a ceramic shaft 14, a shaft hole 16, a vacuum suction groove 18, and a through-hole 20. The ceramic plate 12 is disk-shaped and has a first surface 12a on which a wafer is placed and a second surface 12b opposite the first surface 12a. A heater electrode 22 is embedded within the ceramic plate 12. A cylindrical ceramic shaft 14 is attached to the second surface 12b of the ceramic plate 12. The shaft hole 16 is provided in the side wall constituting the ceramic shaft 14, penetrating from one end of the ceramic shaft 14 to the other. The vacuum suction groove 18 is provided in the second surface 12b of the ceramic plate 12 and / or the upper end surface 14a of the ceramic shaft 14, extending circumferentially. The vacuum suction groove 18, together with the upper end surface 14a and / or the second surface 12b, forms a vacuum suction path communicating with the shaft hole 16. The through-holes 20 are holes that penetrate the ceramic plate 12 in the thickness direction, communicate with the shaft holes 16 and / or the vacuum suction grooves 18, and are provided so as to reach the first surface 12a. As a result, when the shaft holes 16 are vacuum-suctioned, the ceramic heater 10 is configured so that the first surface 12a of the ceramic plate 12 can be vacuum-suctioned via the shaft holes 16, the vacuum suction grooves 18, and the through-holes 20. When viewed from above in the direction of the central axis of the ceramic shaft 14, the area of ​​the vacuum suction grooves 18 accounts for 60 to 96% of the total area of ​​the joint between the ceramic shaft 14 and the second surface 12b and the vacuum suction grooves 18. By providing the vacuum suction grooves 18 with a predetermined area ratio along the joint surface between the ceramic plate 12 and the ceramic shaft 14 and configuring them to be vacuum-suctionable, heat radiation via the ceramic shaft 14 (particularly from the shaft lower end 14b) can be effectively suppressed, thereby significantly improving the thermal uniformity of the ceramic plate 12.

[0012] As mentioned above, ceramic heaters are required to have even better thermal uniformity. However, in a conventional shaft-equipped ceramic heater 110 as shown schematically in FIG. 17, heat transfer occurs by thermal conduction from the ceramic shaft 114 attached to the back surface of the ceramic plate 112 to the equipment side (see arrow A). As a result, heat transfer in the shaft portion of the ceramic heater 110 is increased, and the temperature at the center of the ceramic plate 112 tends to be lower than in other portions, resulting in poor thermal uniformity. Furthermore, a temperature drop near the center of the ceramic plate 112 generates tensile stress in the ceramic plate 112 toward the center of the plate, increasing the potential risk of damage to the ceramic heater 10. These problems are successfully solved by the present invention. The advantages of the present invention, including these, are explained as follows. First, the ceramic heater 10 of the present invention is configured so that, when the shaft hole 16 is vacuum-suctioned, the first surface 12a of the ceramic plate 12 can be vacuum-suctioned via the shaft hole 16, the vacuum suction groove 18, and the through-hole 20. This allows a wafer (not shown) placed on the first surface 12a of the ceramic plate 12 to be fixed to the first surface 12a by vacuum suction during the semiconductor device manufacturing process. This prevents the wafer placed on the first surface 12a from moving during the semiconductor device manufacturing process. While maintaining the basic function of the vacuum suction holes, the thermally resistant vacuum space formed in the vacuum suction grooves 18 when vacuum suction is applied can function as a thermal resistance layer along the bonding surfaces of the ceramic plate 12 and the ceramic shaft 14. This is because there is no gas convection in the vacuum space, and therefore no heat transfer occurs using gas as a heat transfer medium. The vacuum suction grooves 18 as a thermal resistance layer effectively suppress heat transfer or diffusion from the ceramic shaft 14 to the equipment side due to thermal conduction, thereby significantly improving the thermal uniformity of the ceramic plate 12. This means that uniform heat dissipation from the ceramic plate 12 satisfies the high thermal uniformity required of the ceramic heater 10. Furthermore, suppressing thermal conduction also reduces the power consumption of the ceramic heater 10.

[0013] From the above viewpoint, when viewed in a plane in the central axis direction of the ceramic shaft 14, the ratio of the area Sv of the vacuum suction grooves 18 to the total area of ​​the area Sb of the joint portion between the ceramic shaft 14 and the second surface 12b and the area Sv of the vacuum suction grooves 18 (i.e., 100×Sv / (Sb+Sb)) is 60 to 96%, and preferably 65 to 85%.

[0014] The ceramic plate 12 is not particularly limited except for the configuration of the vacuum suction grooves 18 and the through holes 20, and may have the same configuration as ceramic plates used in known ceramic heaters.

[0015] The main portion of the ceramic plate 12 other than the vacuum suction grooves 18, the through holes 20, and the heater electrodes 22 (i.e., the ceramic substrate) preferably contains aluminum nitride or aluminum oxide, more preferably aluminum nitride, from the viewpoints of excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics similar to those of silicon.

[0016] The ceramic plate 12 is 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 it is circular, the diameter is typically 150 to 450 mm, and particularly for 300 mm silicon wafers, it is typically 320 to 380 mm. The thickness of the ceramic plate 12 is typically 10 to 25 mm.

[0017] As shown in FIG. 1 , a heater electrode 22 is embedded in the ceramic plate 12. The heater electrode 22 is not particularly limited, but may be, for example, a conductive coil wired in a single stroke across the entire surface of the ceramic plate 12. The single stroke shape may be any of various known shapes, such as a repeated alternating forward and reverse stroke or a spiral shape. Heater rods 24 are connected to both ends of the heater electrode 22 for power supply, and the heater rods 24 are connected to a heater power supply (not shown) via the internal space S of the ceramic shaft 14. When power is supplied from the heater power supply, the heater electrode 22 generates heat and heats the wafer placed on the first surface 12 a. The heater electrode 22 is not limited to a coil, but may be, for example, a ribbon (a thin, elongated plate) or a mesh.

[0018] The ceramic plate 12 may have an internal electrode other than the heater electrode 22 embedded therein. Examples of such internal electrodes include an RF electrode and an ESC electrode. When a high frequency is applied to an RF electrode, film formation by a plasma CVD process is possible. The ESC electrode is an abbreviation for an 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, the ESC electrode chucks a wafer placed on the first surface 12a 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 a high frequency to the ESC electrode, the ESC electrode can also be used as an RF electrode, and film formation by a plasma CVD process can also be performed. Terminal rods, such as an RF rod or an ESC rod, for power supply are connected to the RF electrode or ESC electrode, and the terminal rods can be connected to an external power supply (not shown).

[0019] The ceramic shaft 14 is a cylindrical shaft attached to the second surface 12b of the ceramic plate 12 and may have a configuration similar to that of ceramic shafts used in known ceramic susceptors or ceramic heaters. The internal space S is configured so that a terminal rod such as a heater rod 24 passes therethrough. The ceramic shaft 14 is preferably made of the same ceramic material as the ceramic plate 12. Therefore, the ceramic shaft 14 preferably contains aluminum nitride or aluminum oxide, more preferably aluminum nitride. The upper end surface 14a of the ceramic shaft 14 (i.e., the portion other than the vacuum suction grooves 18) is preferably bonded to the second surface 12b of the ceramic plate 12 by solid-state bonding or diffusion bonding. The outer diameter of the ceramic shaft 14 is not particularly limited, but is preferably 40 to 60 mm. The inner diameter of the ceramic shaft 14 (the diameter of the internal space S) is also not particularly limited, but is preferably 33 to 55 mm.

[0020] The shaft hole 16 is provided in the side wall constituting the ceramic shaft 14, penetrating from one end (e.g., the lower end 14b) to the other end (e.g., the upper end surface 14a) of the ceramic shaft 14. Typically, the shaft hole 16 is provided parallel to the central axis of the ceramic shaft 14. The planar shape of the shaft hole 16 may be any shape, such as circular or polygonal, but is preferably circular. The diameter of the shaft hole 16 is not particularly limited, but is preferably 3.0 to 8.0 mm, more preferably 4.5 to 5.5 mm, and even more preferably 4.8 to 5.2 mm. Here, in the case of a polygonal shape, the diameter refers to the diameter of a circle circumscribing the polygon. The number of shaft holes 16 provided in the ceramic shaft 14 may be one or more. In the latter case, the number of shaft holes 16 is preferably two or three. A vacuum pump (not shown) can be connected to the lower end of the shaft hole 16. This allows the vacuum suction path formed by the shaft hole 16, the vacuum suction groove 18 and the through hole 20 to be vacuum suctioned.

[0021] The through holes 20 are holes that penetrate the ceramic plate 12 in the thickness direction, communicate with the shaft holes 16 and / or the vacuum suction grooves 18, and are provided so as to reach the first surface 12a. Because the through holes 20 function as vacuum suction holes, a wafer (not shown) placed on the first surface 12a of the ceramic plate 12 can be adsorbed and fixed to the first surface 12a by vacuum suction during the semiconductor device manufacturing process. From the viewpoint of vacuum suction efficiency, it is preferable that the through holes 20 be positioned so that the shaft holes 16 and the through holes 20 overlap each other when viewed in a plan view in the central axis direction of the ceramic shaft 14. However, the present invention is not limited to this, and the shaft holes 16 and the through holes 20 may be positioned at different positions when viewed in a plan view.

[0022] The number of through holes 20 provided in the ceramic plate 12 may be one, but a plurality of through holes 20 is preferred in that it makes it easier to suction-fix the wafer to the first surface 12a. In particular, it is more preferred that the plurality of through holes 20 be arranged at positions rotationally symmetrical to one another about the central axis of the ceramic shaft 14, as shown in Figures 2 to 6, in that it makes it possible to evenly suction-fix the wafer to the first surface 12a. From the above viewpoint, the number of through holes 20 is preferably two or three.

[0023] The vacuum suction groove 18 is a groove that forms a vacuum suction path communicating with the shaft hole 16 together with the upper end surface 14a of the ceramic shaft 14 and / or the second surface 12b of the ceramic plate 12, and is provided so as to extend circumferentially on the second surface 12b of the ceramic plate 12 and / or the upper end surface 14a of the ceramic shaft 14.

[0024] The number of vacuum suction grooves 18 may be one as shown in FIG. 2 or multiple as shown in FIGS. 3 to 6. In the latter case, the number of vacuum suction grooves 18 is preferably two or three. For example, as shown in FIGS. 3 to 6, it is preferable to provide multiple vacuum suction grooves 18 in communication with each of the multiple shaft holes 16 (or through holes 20). In this case, the number of vacuum suction grooves 18 is the same as the number of shaft holes 16 (or through holes 20). However, as shown in FIG. 2, one vacuum suction groove 18 may be provided in communication with multiple shaft holes 16 (or through holes 20). Providing multiple vacuum suction grooves 18 has the advantage of increasing the number of bonding points between the ceramic shaft 14 and the ceramic plate 12, thereby firmly maintaining the bond between the ceramic plate 12 and the ceramic shaft 14, while still adequately ensuring the function of the thermal resistance layer. From this perspective, it is preferable that the multiple vacuum suction grooves 18 be spaced apart from one another in the circumferential direction. Furthermore, when there are multiple vacuum suction grooves 18, the shaft hole 16 (or through hole 20) may be located at the longitudinal end of each of the multiple vacuum suction grooves 18 as shown in Figures 3 to 6, or may be located in the longitudinal middle.

[0025] The diameter of the shaft hole 16, the diameter of the through hole 20, and the width of the vacuum suction groove 18 may be the same as or different from one another. For example, as shown in Figures 1 to 6, the diameter of the shaft hole 16 and the diameter of the through hole 20 may be larger than the width of the vacuum suction groove 18, or as shown in Figures 7 to 10, the diameter of the shaft hole 16 and the diameter of the through hole 20 may be narrower than the width of the vacuum suction groove 18.

[0026] In a preferred embodiment of the present invention, the vacuum suction grooves 18 are provided in an annular shape, as shown in Fig. 2. This embodiment has the advantage that providing the grooves in an annular or concentric shape makes it possible to make the thermal resistance uniform in the circumferential direction.

[0027] In another preferred embodiment of the present invention, the vacuum suction grooves 18 are formed in an arc shape, as shown in Figures 3 and 4. According to this embodiment, bonding portions are also formed at the circumferentially spaced apart portions of the arcs, which has the advantage of increasing the number of bonding points between the ceramic shaft 14 and the ceramic plate 12, thereby enabling the ceramic plate 12 and the ceramic shaft 14 to be firmly bonded to each other.

[0028] In another preferred embodiment of the present invention, the vacuum suction groove 18 is provided so as to extend in a serpentine manner in the circumferential direction, as shown in Fig. 5. According to this embodiment, by providing a serpentine portion, it is possible to partially increase the bonded portion with the ceramic shaft 14, which has the advantage of enabling local adjustment of the bond strength.

[0029] In another preferred embodiment of the present invention, the vacuum suction grooves 18 are formed in a pattern that includes circumferential advance, return, and circumferential retreat, as shown in Fig. 6. This embodiment has the advantage that a joint is formed in the radial center as well, thereby increasing the number of joints between the ceramic shaft 14 and the ceramic plate 12 and firmly maintaining the joint between the ceramic plate 12 and the ceramic shaft 14. Another advantage is that the thermal conductivity can be adjusted in the circumferential direction by adjusting the groove width and groove length.

[0030] The cross-sectional shape of the vacuum suction groove 18 (i.e., the cross-sectional shape perpendicular to the groove direction) is not particularly limited, and can be a rectangle as shown in FIG. 7, a trapezoid as shown in FIG. 8, a semicircle as shown in FIG. 9, a diamond as shown in FIG. 10, or a combination thereof.

[0031] The depth Y of the vacuum suction groove 18 is preferably 0.5 to 30 mm, more preferably 0.5 to 15 mm, and even more preferably 0.5 to 3.0 mm. Within this range, the vacuum suction groove 18 can effectively function as a heat resistance layer.

[0032] The width W of the vacuum suction groove 18 is determined by the thickness of the sidewalls at the upper end surface 14a of the ceramic shaft 14 and the width X of each of the joint portions between the ceramic shaft 14 and the second surface 12b. That is, the width W of the vacuum suction groove 18 is the thickness of the sidewalls of the ceramic shaft 14 minus the total width X of the joint portions (in other words, the total width of the width X1 of the joint portion on the outer periphery side and the width X2 of the joint portion on the inner periphery side). The width X of each of the joint portions between the ceramic shaft 14 and the second surface 12b is preferably 0.5 to 3.0 mm, and more preferably 0.5 to 1.5 mm. Within this range, the joint between the ceramic plate 12 and the ceramic shaft 14 is firmly maintained while the vacuum suction groove 18 can effectively function as a heat resistance layer. [Example]

[0033] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0034] Example 1 (comparison) (1) Fabrication of ceramic heater Using the components shown below, a ceramic heater 10 having no vacuum suction grooves or through holes as shown in FIG. 11 was fabricated by a known procedure. <Component parts and their specifications> Ceramic plate 12: a circular aluminum nitride sintered body (diameter: 350 mm, thickness: 15 mm) (with heater electrode 22 embedded inside) Heater electrode 22: A coil-shaped resistance heating element embedded in the ceramic plate 12 according to a predetermined circuit pattern. Ceramic shaft 14: Cylindrical aluminum nitride sintered body (height: 150 mm, maximum outer diameter: 80 mm, minimum outer diameter: 60 mm, inner diameter: 50 mm) Heater rods 24: Two terminal rods made of nickel, connected to the heater electrodes 22

[0035] (2) Evaluation The ceramic heaters produced in each example were evaluated as follows.

[0036] <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 1 to 20 Torr. The ceramic heater 10 was heated to a set temperature of 550°C by supplying power to the heater electrode 22 via two heater rods 24. 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 the surface (i.e., the maximum temperature difference within the surface) was determined as an index of thermal uniformity, and this was used as a standard for relatively evaluating thermal uniformity in the following Example 2 and subsequent examples.

[0037] <Heat dissipation at shaft end> The heat dissipation amount (W) from the lower end 14b of the ceramic shaft 14 (the end farthest from the ceramic plate 12) in the above-mentioned thermal uniformity measurement (hereinafter referred to as shaft end heat dissipation amount) was calculated from the results of the temperature measurement, and was adopted as a standard for relatively evaluating the shaft end heat dissipation amount in the subsequent Example 2 and onwards.

[0038] <Shaft end temperature> In the above-mentioned thermal uniformity measurement, the temperature (°C) (hereinafter referred to as the shaft end temperature) of the lower end 14b of the ceramic shaft 14 (the end farthest from the ceramic plate 12) was measured and used as a standard for relatively evaluating the shaft end temperature in the subsequent Example 2 and thereafter.

[0039] Examples 2 to 6 Ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1, except that, as shown in FIG. 12, two through-holes were formed in ceramic plate 12 and ceramic shaft 14, and a vacuum suction groove having a groove depth Y of 1.0 mm and a joint width X of 0.5 mm (Example 2), 1.0 mm (Example 3), 1.5 mm (Example 4), 2.0 mm (Example 5), or 2.5 mm (Example 6) was formed at the upper end of ceramic shaft 14, as shown in Tables 1 to 4. The shape of the vacuum suction groove in a planar view was annular as shown in FIG. 2, and the cross-sectional shape of the vacuum suction groove was rectangular as shown in FIG. 7. The ratio of the area of ​​the vacuum suction groove to the total area of ​​the joint between the ceramic shaft and ceramic plate and the vacuum suction groove, when viewed in a planar view along the central axis of the ceramic shaft, was as shown in Table 1. In Examples 2 to 6 and Examples 7 to 13 described later, the width X of the inner circumferential bonding portion and the width X of the outer circumferential bonding portion are the same value, but it goes without saying that in the present invention, the width X of the inner circumferential bonding portion and the width X of the outer circumferential bonding portion may have different values.

[0040] <Heat uniformity> As an evaluation result of the thermal uniformity, the improvement rate (%) of the thermal uniformity compared to Example 1 (Comparative Example) was calculated. Specifically, the relative value R of the maximum in-plane temperature difference of each example, when the maximum in-plane temperature difference of Example 1 was set to 100%, was calculated as follows: ΔT (%) and subtract R from 100% ΔT (%) (i.e., 100-R ΔT ) was calculated as the improvement rate of thermal uniformity. Therefore, the improvement rate of thermal uniformity for the reference example 1 was 0%, and the larger the improvement rate of thermal uniformity in each example, the smaller the maximum in-plane temperature difference, i.e., the better the thermal uniformity. The results are shown in Table 2 and Figure 13, and Figure 13 also shows the results for Example 1. From the results shown in Table 2 and Figure 13, it can be seen that thermal uniformity is further improved by fixing the depth Y of the vacuum suction groove at 1.0 mm and decreasing the width X of the joint (i.e., increasing the groove width).

[0041] <Heat dissipation at shaft end> As an evaluation result of the shaft end heat dissipation amount, the reduction rate (%) of the shaft end heat dissipation amount relative to Example 1 (Comparative Example) was calculated. Specifically, when the shaft heat dissipation amount in Example 1 was set to 100%, the relative value R of the shaft end heat dissipation amount in each example was calculated. Q (%) and subtract (100-R Q ) (%) was calculated as the percentage reduction in shaft end heat dissipation. Therefore, the percentage reduction in shaft end heat dissipation for the reference example 1 was 0%, and the larger the percentage reduction in shaft end heat dissipation for each example, the smaller the shaft heat dissipation, i.e., the more effectively heat dissipation from the shaft end can be suppressed. The results are shown in Table 3 and FIG. 14, and FIG. 14 also shows the results for Example 1. From the results shown in Table 3 and FIG. 14, it can be seen that by fixing the depth Y of the vacuum suction groove to 1.0 mm and decreasing the width X of the joint portion (i.e., increasing the groove width), the percentage reduction in shaft end heat dissipation increases, i.e., heat dissipation from the shaft end can be further suppressed.

[0042] <Shaft end temperature> As an evaluation result of the shaft end temperature, the reduction rate (%) of the shaft end temperature relative to Example 1 (Comparative Example) was calculated. Specifically, the relative value R of the shaft end temperature of each example, where the shaft end temperature in Example 1 is set to 100%, was calculated as follows: T (%) and subtract (100-R T ) (%) was calculated as the percentage reduction in shaft end temperature. Therefore, the percentage reduction in shaft end temperature for the reference Example 1 was 0%, and the larger the percentage reduction in shaft end temperature for each Example, the lower the shaft end temperature, meaning that the increase in shaft end temperature can be more effectively suppressed. The results are shown in Table 4 and Figure 14, which also shows the results for Example 1. The results shown in Table 4 and Figure 14 show that by fixing the depth Y of the vacuum suction groove to 1.0 mm and decreasing the width X of the joint (i.e., increasing the groove width), the percentage reduction in shaft end temperature increases, meaning that heat dissipation from the shaft end can be further suppressed.

[0043] Examples 7-9 Ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1, except that, as shown in FIG. 12, two through-holes were formed in ceramic plate 12 and ceramic shaft 14, and a vacuum suction groove was formed at the upper end of ceramic shaft 14, with a joint width X of 1.0 mm and a groove depth Y of 0.5 mm (Example 7), 1.5 mm (Example 8), or 2.0 mm (Example 9), as shown in Tables 1 to 3. The shape of the vacuum suction groove in a plan view was annular as shown in FIG. 2, and the cross-sectional shape of the vacuum suction groove was rectangular as shown in FIG. 7. The ratio of the area of ​​the vacuum suction groove to the total area of ​​the joint between the ceramic shaft and ceramic plate and the vacuum suction groove, when viewed in a plan view in the direction of the central axis of the ceramic shaft, was as shown in Table 1.

[0044] <Heat uniformity> As an evaluation result of thermal uniformity, the improvement rate (%) of thermal uniformity relative to Example 1 (Comparative Example) was calculated in the same manner as in Examples 2 to 6. The results are shown in Table 2 and Fig. 15, which also shows the results of Example 1 (Comparative Example) and Example 3 (wherein the width X of the joint portion was 1.0 mm and the groove depth Y was 1.0 mm). From the results shown in Table 2 and Fig. 15, it can be seen that the thermal uniformity is further improved by increasing the groove depth Y while fixing the width X of the joint portion at 1.0 mm.

[0045] <Heat dissipation at shaft end> As an evaluation result of the shaft end heat dissipation amount, the reduction rate (%) of the shaft end heat dissipation amount relative to Example 1 (Comparative Example) was calculated in the same manner as in Examples 2 to 6. The results are shown in Table 3 and Fig. 16, which also shows the results of Example 1 (Comparative Example) and Example 3 (wherein the width X of the joint portion was 1.0 mm and the groove depth Y was 1.0 mm). The results shown in Table 3 and Fig. 16 show that by fixing the width X of the joint portion at 1.0 mm and increasing the groove depth Y, the reduction rate of the shaft end heat dissipation amount increases, that is, heat dissipation from the shaft end can be further suppressed.

[0046] <Shaft end temperature> As an evaluation result of the shaft end temperature, the reduction rate (%) of the shaft end temperature relative to Example 1 (Comparative Example) was calculated in the same manner as in Examples 2 to 6. The results are shown in Table 4 and Fig. 16, which also shows the results of Example 1 (Comparative Example) and Example 3 (wherein the width X of the joint portion was 1.0 mm and the groove depth Y was 1.0 mm). From the results shown in Table 4 and Fig. 16, it can be seen that by fixing the width X of the joint portion to 1.0 mm and increasing the groove depth Y, the reduction rate of the shaft end temperature increases, that is, heat dissipation from the shaft end can be further suppressed.

[0047] Examples 10-13 12, two through-holes were provided in the ceramic plate 12 and the ceramic shaft 14, and a vacuum suction groove was formed at the upper end of the ceramic shaft 14, with the joining portion having a width X of 0.5 mm and a groove depth Y of 0.5 mm (Example 10), a joining portion having a width X of 2.5 mm and a groove depth Y of 0.5 mm (Example 11), a joining portion having a width X of 2.0 mm and a groove depth Y of 0.5 mm (Example 12), or a joining portion having a width X of 2.5 mm and a groove depth Y of 2.0 mm (Example 13), as shown in Tables 2 to 4. The ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1, except that the planar shape of the vacuum suction groove was annular as shown in FIG. 2, and the cross-sectional shape of the vacuum suction groove was rectangular as shown in FIG. 7. In addition, when viewed in a plane in the direction of the central axis of the ceramic shaft, the ratio of the area of ​​the vacuum suction groove to the total area of ​​the joint between the ceramic shaft and the ceramic plate and the vacuum suction groove was as shown in Table 1.

[0048] <Heat uniformity> As an evaluation result of thermal uniformity, the improvement rate (%) of thermal uniformity relative to Example 1 (Comparative Example) was calculated in the same manner as in Examples 2 to 6. The results are shown in Table 2, and it can be seen that the thermal uniformity is further improved by reducing the width X of the joint portion (i.e., increasing the groove width) and increasing the groove depth Y.

[0049] <Heat dissipation at shaft end> As an evaluation result of the shaft end heat dissipation amount, the reduction rate (%) of the shaft end heat dissipation amount relative to Example 1 (Comparative Example) was calculated in the same manner as in Examples 2 to 6. The results are shown in Table 3, and it can be seen that by reducing the width X of the joint portion (i.e., increasing the groove width) and increasing the groove depth Y, the reduction rate of the shaft end heat dissipation amount becomes larger, that is, heat dissipation from the shaft end can be further suppressed.

[0050] <Shaft end temperature> As an evaluation result of the shaft end temperature, the reduction rate (%) of the shaft end temperature relative to Example 1 (Comparative Example) was calculated in the same manner as in Examples 2 to 6. The results are shown in Table 4, and it can be seen that by reducing the width X of the joint portion (i.e., increasing the groove width) and increasing the groove depth Y, the reduction rate of the shaft end temperature becomes larger, that is, heat radiation from the shaft end can be further suppressed.

[0051] [Table 1]

[0052] [Table 2]

[0053] [Table 3]

[0054] [Table 4]

[0055] In all of the results shown in Tables 2 to 4, it can be seen that the further down to the left in each table, i.e., the smaller the width X of the joint portion (i.e., the larger the groove width) and the larger the groove depth Y, the more advantageous it is in terms of heat uniformity and suppression of heat dissipation from the shaft end. [Explanation of symbols]

[0056] 10,110 Ceramic heater 12,112 ceramic plates 12a Front page 12b Second side 14,114 Ceramic shaft 14a Top surface 14b Lower end of shaft 16 shaft holes 18 Vacuum suction groove 20 through holes 22 heater electrode 24 Heater rod X Joint width Y Vacuum suction groove depth W Vacuum suction groove width S interior space

Claims

1. a circular ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface, and having a heater electrode embedded therein; a cylindrical ceramic shaft attached to a second surface of the ceramic plate; a shaft hole formed in a side wall of the ceramic shaft, the shaft hole penetrating from one end to the other end of the ceramic shaft; a vacuum suction groove provided on the second surface of the ceramic plate and / or the upper end surface of the ceramic shaft so as to extend in a circumferential direction, the vacuum suction groove forming a vacuum suction path communicating with the shaft hole together with the upper end surface and / or the second surface; a through hole penetrating the ceramic plate in a thickness direction, the through hole communicating with the shaft hole and / or the vacuum suction groove and provided to reach the first surface; A ceramic heater comprising: the ceramic heater is configured so that, when the shaft hole is vacuum-suctioned, the first surface of the ceramic plate can be vacuum-suctioned through the shaft hole, the vacuum suction groove, and the through-hole; a ceramic heater, wherein, when viewed in a plan view in the central axis direction of the ceramic shaft, a ratio of an area of ​​the vacuum suction groove to a total area of ​​a joint portion between the ceramic shaft and the second surface and the vacuum suction groove is 60 to 96%.

2. 2. The ceramic heater according to claim 1, wherein the ratio of the area of ​​the vacuum suction groove to the total area of ​​the joining portion between the ceramic shaft and the second surface and the vacuum suction groove is 65 to 85%.

3. 3. The ceramic heater according to claim 1, wherein the shaft hole and the through hole are arranged so as to overlap each other when viewed in a plan view in the direction of the central axis of the ceramic shaft.

4. 3. The ceramic heater according to claim 1, wherein the vacuum suction groove has a depth of 0.5 to 30 mm.

5. 3. The ceramic heater according to claim 1, wherein the width of each of the joints between the ceramic shaft and the second surface is 0.5 to 3.0 mm.

6. 3. The ceramic heater according to claim 1, wherein a plurality of the through holes are provided, and the plurality of through holes are arranged at positions rotationally symmetrical to one another with respect to the central axis of the ceramic shaft.

7. The ceramic heater according to claim 6, wherein the number of the through holes is two or three.

8. The vacuum suction groove is provided in a plurality, The through-hole is located at an end in the longitudinal direction of each of the plurality of vacuum suction grooves, 7. The ceramic heater according to claim 6, wherein said plurality of vacuum suction grooves are arranged spaced apart from one another in the circumferential direction.

9. 3. The ceramic heater according to claim 1, wherein the number of said vacuum suction grooves is two or three.

10. 3. The ceramic heater according to claim 1, wherein the vacuum suction groove is formed in a circular or arc shape.

11. 3. The ceramic heater according to claim 1, wherein the vacuum suction grooves are provided so as to extend in a circumferential direction in a meandering manner.

12. 3. The ceramic heater according to claim 1, wherein the vacuum suction grooves are formed in a pattern including a circumferential progression, a circumferential return, and a circumferential regression.

13. 3. The ceramic heater according to claim 1, wherein the cross-sectional shape of the vacuum suction groove is at least one selected from the group consisting of a rectangle, a trapezoid, a semicircle, and a rhombus.

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