Ceramic heater
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NGK CORP
- Filing Date
- 2025-04-16
- Publication Date
- 2026-08-05
Smart Images
Figure 0007901263000003 
Figure 0007901263000004 
Figure 0007901263000005
Abstract
Description
Technical Field
[0001] The present disclosure relates to a ceramic heater.
Background Art
[0002] In a film forming apparatus for a semiconductor manufacturing process, a ceramic heater is used as a support stage for uniformly controlling the temperature of a wafer. As such a ceramic heater, one including a ceramic plate on which a wafer is placed and a cylindrical ceramic shaft attached to the ceramic plate is widely used. Also, a multi-zone ceramic heater having a plurality of heating zones is known as a ceramic heater.
[0003] Patent Document 1 (Japanese Patent Application Laid-Open No. 2022-48064) discloses a holding device including a plate-like member, an internal electrode (for example, a heater electrode) disposed inside the plate-like member, a via extending in a direction substantially perpendicular to the surface of the plate-like member inside the plate-like member and electrically connected to the internal electrode, a terminal member capable of energizing the internal electrode, and a conductive connecting member for electrically connecting the via and the terminal member. The connecting member has a via-side connecting portion connected to the via and a terminal-side connecting portion connected to the terminal member, and the via-side connecting portion and the terminal-side connecting portion are disposed at different positions in a direction substantially parallel to the surface of the plate-like member.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
[0005] Ceramic heaters require minimal temperature differences across the surface on which the wafer is placed (i.e., uniform heating). In particular, with the miniaturization and high integration of processes in recent years, even greater uniformity is required for ceramic heaters. From this perspective, it is desirable to minimize the temperature difference between areas where resistive heating elements are present and areas where they are not. To achieve this, it is preferable to arrange resistive heating elements as a heater circuit throughout the entire surface of the ceramic heater. Furthermore, heater terminal holes are provided in the ceramic plate in which the resistive heating elements are embedded, in order to electrically connect the power supply rods (heater rods) to the resistive heating elements. From the viewpoint of improving uniformity, it is desirable for the heater terminal holes to be small, but as the process temperature increases, the current value flowing through the resistive heating elements also tends to increase, so there are limits to how small the heater terminal holes can be made. On the other hand, it is desirable to arrange resistive heating elements in a limited space around the heater terminal holes, but if more resistive heating elements are placed in a limited space, there is a problem that the coil-shaped resistive heating elements, the heater coils, are more likely to be exposed in the heater terminal holes. To avoid this problem, if the heater coil is positioned away from the heater terminal holes, then during use in semiconductor manufacturing processes, insufficient heat generation can cause localized low-temperature spots. Localized center-cool temperature distributions accompanied by these cool spots are caused by tensile thermal stress, which can lead to crack formation.
[0006] The present inventors have now found that by employing a heater circuit including a heater coil section composed of a coil-shaped resistance heating element and a heater wire section composed of a wire-shaped resistance heating element, and by arranging the heater wire section at the same depth as or deeper than the lower end of the heater coil section, closer to the back surface of the plate, it is possible to prevent the heater coil section from being exposed to the heater terminal hole and to prevent localized center cooling, while also preventing crack formation during use.
[0007] Therefore, the object of the present invention is to provide a ceramic heater that prevents exposure of the heater coil portion to the heater terminal hole and localized center cooling, while also preventing crack formation during use.
[0008] The following aspects are provided according to this disclosure. [Aspect 1] A ceramic plate having a first surface on which a wafer is placed and a second surface facing the first surface, A heater circuit embedded in the ceramic plate, At least one pair of spherical terminals embedded in the ceramic plate and connected to the heater circuit, The ceramic plate has at least one pair of heater terminal holes formed on its second surface so as to reach each of the spherical terminals, A pair of heater rods for supplying power to the heater circuit, which are inserted into each of the heater terminal holes and electrically connected to each of the spherical terminals, and which extend in a direction away from the first surface, Equipped with, The heater circuit described above, A heater coil section, which is arranged parallel to the first surface and is composed of a coil-shaped resistance heating element, A heater wire portion is made up of a non-coiled, strand-shaped resistance heating element that extends from the heater coil portion and whose tip reaches the inside of the spherical terminal, Includes, A ceramic heater in which, when the ceramic plate is viewed in cross-section, the heater wire portion is positioned at a depth closer to the second surface, at the same depth as or deeper than the lower end of the heater coil portion. [Aspect 2] The ceramic heater according to Embodiment 1, wherein, when the ceramic plate is viewed in cross-section, a line parallel to the first surface passing through the center of a virtual circle identified by the cross-sectional arc of the spherical terminal is defined as the terminal centerline, and the heater wire portion is arranged along the terminal centerline. [Aspect 3] The ceramic heater according to embodiment 1 or 2, wherein the ceramic plate comprises aluminum nitride or aluminum oxide. [Aspect 4] The ceramic heater according to any one of embodiments 1 to 3, wherein the spherical terminal is composed of a resistance heating element having the same composition as the coil-shaped resistance heating element. [Aspect 5] A ceramic heater according to any one of embodiments 1 to 4, wherein the resistance heating element includes at least one selected from the group consisting of tungsten, molybdenum, tungsten-molybdenum alloy, tungsten carbide, tungsten carbide-titanium nitride composite material, tungsten carbide-aluminum oxide composite material, and niobium. [Aspect 6] A ceramic heater according to any one of embodiments 1 to 5, wherein, when the ceramic plate is viewed planarly from the second surface, the heater coil portion does not exist within the region defined by the heater terminal hole. [Aspect 7] A ceramic heater according to any one of embodiments 1 to 6, further comprising a cylindrical ceramic shaft attached to the second surface of the ceramic plate and having an internal space. [Aspect 8] A ceramic heater according to any one of embodiments 1 to 7, wherein the heater wire portion does not penetrate the spherical terminal and extend to the outside thereof, and therefore the heater wire portion terminates within the spherical terminal. [Aspect 9] The ceramic plate includes an inner zone defined as a circular region within a predetermined distance from the center of the ceramic plate when viewed from above, and an outer zone defined as an annular region outside the inner zone. The heater circuit described above, An inner zone heater circuit, which includes the heater coil portion and the heater wire portion, is embedded in the inner zone of the ceramic plate. An outer zone heater circuit, which includes the heater coil portion and the heater wire portion, is embedded in the outer zone of the ceramic plate. Includes, A ceramic heater according to any one of embodiments 1 to 8, wherein the pair of spherical terminals is connected to each of the inner zone heater circuit and the outer zone heater circuit, and the heater rod is connected to each of the pair of spherical terminals. [Aspect 10] The ceramic heater according to embodiment 9, wherein the inner zone heater circuit and the outer zone heater circuit are arranged on different planes when the ceramic plate is viewed in cross-section. [Aspect 11] The ceramic plate includes an inner zone defined as a circular region within a predetermined distance from the center of the ceramic plate when viewed from above, and an outer zone defined as an annular region outside the inner zone. The heater circuit described above, An inner zone heater circuit, which includes the heater coil portion and the heater wire portion, is embedded in the inner zone of the ceramic plate. An outer zone heater circuit, which includes the heater coil portion and the heater wire portion, is embedded in the outer zone of the ceramic plate. A pair of jumpers are provided, which are embedded in the inner zone of the ceramic plate so as not to contact the inner zone heater circuit and which are composed of strand-shaped resistive heating elements extending from the heater strand portion of the outer zone heater circuit. A ceramic heater according to any one of embodiments 1 to 8, comprising the inner zone heater circuit and the jumper, each of which is connected to the pair of spherical terminals, and each of the pair of spherical terminals is connected to the heater rod (however, the jumper does not have to be located at the same depth as or deeper than the lower end of the heater coil portion of the outer zone heater circuit, closer to the second surface). [Aspect 12] The ceramic heater according to embodiment 11, wherein the inner zone heater circuit and the outer zone heater circuit are arranged on the same plane when the ceramic plate is viewed in cross-section. [Aspect 13] The ceramic heater according to aspect 11, wherein the inner zone heater circuit and the outer zone heater circuit are arranged on different planes when the ceramic plate is viewed in cross section.
Brief Description of the Drawings
[0009] [Figure 1] It is a perspective cross-sectional view schematically showing an example of the ceramic heater according to the present invention, corresponding to Example 1. [Figure 2] It is a perspective top view schematically showing the ceramic heater shown in FIG. 1, corresponding to Examples 1 and 2. [Figure 3] It is a schematic cross-sectional view conceptually showing the internal structure of the ceramic plate in the ceramic heater shown in FIG. 1, corresponding to Examples 1 to 3. [Figure 4] It is a schematic cross-sectional view showing an example of the positional relationship between the spherical terminal and the heater wire portion. [Figure 5] It is a schematic cross-sectional view showing another example of the positional relationship between the spherical terminal and the heater wire portion. [Figure 6] It is a schematic cross-sectional view showing another example of the positional relationship between the spherical terminal and the heater wire portion. [Figure 7] It is a perspective cross-sectional view schematically showing another example of the ceramic heater according to the present invention, corresponding to Example 2. [Figure 8] It is a perspective cross-sectional view schematically showing another example of the ceramic heater according to the present invention, corresponding to Example 3. For convenience of explanation, in order to clearly show the configurations of the inner zone heater circuit 14a and the jumper 14c, which are originally located at the same height, the jumper 14c is drawn at a position slightly lower than its original position. [Figure 9] It is a perspective top view schematically showing the ceramic heater shown in FIG. 8, corresponding to Examples 3 and 4. [Figure 10] It is a plan view schematically showing the arrangement of the heater circuit in the central region of the ceramic plate shown in FIG. 8, corresponding to Example 3. [Figure 11]Figure 8 is a schematic cross-sectional view conceptually showing the internal structure of the ceramic plate in the ceramic heater, and corresponds to Example 3. [Figure 12] This is a schematic perspective cross-sectional view showing another example of the ceramic heater according to the present invention, corresponding to Example 4. [Figure 13] Figure 12 is a schematic cross-sectional view conceptually showing the internal structure of the ceramic plate in the ceramic heater shown, and corresponds to Example 4. [Figure 14] This is a schematic cross-sectional view conceptually showing the internal structure of a ceramic plate in an example of a ceramic heater not according to the present invention, and corresponds to Example 5 (Comparative Example). [Figure 15] This is a schematic cross-sectional view conceptually showing the internal structure of a ceramic plate in another example of a ceramic heater not according to the present invention, and corresponds to Example 6 (Comparative Example). [Modes for carrying out the invention]
[0010] The ceramic heater according to the present invention is a ceramic stand for supporting wafers within semiconductor manufacturing equipment. Typically, the ceramic heater according to the present invention may be a ceramic heater for semiconductor film deposition equipment. Typical examples of film deposition equipment include CVD (chemical vapor deposition) equipment (e.g., thermal CVD equipment, plasma CVD equipment, photoCVD equipment, and MOCVD equipment) and PVD (physical vapor deposition) equipment.
[0011] Figures 1-3 show one embodiment of a ceramic heater. The ceramic heater 10 shown in Figures 1 and 2 comprises a ceramic plate 12, a heater circuit 14, at least one pair of spherical terminals 20, at least one pair of heater terminal holes 22, and at least one pair of heater rods 24. The ceramic plate 12 has a first surface 12a on which a wafer W is placed, and a second surface 12b facing the first surface 12a. The heater circuit 14 is embedded in the ceramic plate 12. The spherical terminals 20 are embedded in the ceramic plate 12 and connected to the heater circuit 14. The heater terminal holes 22 are holes formed so that they can reach each of the spherical terminals 20 from the second surface 12b of the ceramic plate 12. The heater rods 24 are rod-shaped electrode terminals for supplying power to the heater circuit 14. The heater rod 24 is inserted into each of at least one pair of heater terminal holes 22 and electrically connected to each of at least one pair of spherical terminals 20, and extends away from the first surface 12a. The heater circuit 14 includes a heater coil section 16 and a heater wire section 18. The heater coil section 16 is made up of a coiled resistance heating element and is arranged parallel to the first surface 12a. The heater wire section 18 is made up of a wire-shaped resistance heating element that is not wound in a coil, extends from the heater coil section 16, and the tip of the heater wire section 18 reaches inside the spherical terminals 20. When the ceramic plate 12 is viewed in cross-section, the heater wire section 18 is positioned at a depth closer to the second surface 12b, at the same depth as or deeper than the lower end of the heater coil section 16. In this way, a heater circuit 14 is adopted that includes a heater coil section 16 composed of a coil-shaped resistance heating element and a heater wire section 18 composed of a wire-shaped resistance heating element. By arranging the heater wire section 18 at a depth position closer to the second surface 12b, at the same depth as or deeper than the lower end of the heater coil section 16, it is possible to prevent exposure of the heater coil section 16 to the heater terminal hole 22 and the occurrence of localized center cooling, while also preventing crack formation during use.
[0012] As mentioned above, with the miniaturization and high integration of processes in recent years, ceramic heaters are required to have even greater uniformity of heat. To achieve this, it is preferable to arrange resistive heating elements as heater circuits throughout the entire surface of the ceramic heater. Furthermore, from the viewpoint of improving uniformity of heat, it is desirable for the heater terminal holes to be small, but as the process temperature rises, the current value flowing through the resistive heating elements also tends to increase, so there are limits to how small the heater terminal holes can be made. On the other hand, it is desirable to arrange resistive heating elements in a limited space around the heater terminal holes, but if more resistive heating elements are placed in a limited space, there is a problem that the heater coil, which is a coil-shaped resistive heating element, is more likely to be exposed to the heater terminal holes. In this regard, it goes without saying that ceramic heaters should be designed so that the heater coil is not inherently exposed to the heater terminal holes, but exposure of the heater coil can occur unintentionally. In other words, ceramic plates are manufactured by placing heater circuits and other components together with ceramic powder on a compacted ceramic powder, followed by press molding and firing. During this process, the heater circuit, especially the heater coil, may shift or deform from its original position. As a result, when heater terminal holes are drilled in the ceramic plate after firing, the heater coil may be exposed in the heater terminal holes. When the heater coil is exposed in the heater terminal holes, the exposed portion of the material constituting the heater coil (typically molybdenum or tungsten) can rapidly oxidize and disappear when exposed to high temperatures (e.g., 500°C) during use in the semiconductor manufacturing process, potentially leading to the loss of part of the heater circuit (i.e., a break in the heater circuit). To avoid this problem, if the heater coil is positioned further away from the heater terminal holes, then during use in the semiconductor manufacturing process, a cool spot will occur due to insufficient heat generation, resulting in locally low temperatures. For example, as shown in Figure 14, in order to move the heater terminal hole 22 (especially the bottom of the hole) away from the heater coil section 16, the heater wire section 18 needs to be longer. As a result, the coil density in that section decreases relatively, and a cool spot occurs. A localized center cool temperature distribution accompanied by a cool spot is caused by tensile thermal stress, and cracks may occur due to this tensile thermal stress.These problems are successfully solved according to the present invention. Specifically, in the present invention, as shown in Figures 3 and 13, the heater wire portion 18 is positioned at a depth closer to the second surface 12b, which is the same depth as or deeper than the lower end of the heater coil portion 16, thereby moving the heater coil portion 16 away from the heater terminal hole 22 (especially the bottom of the hole) in the direction toward the first surface 12a. As a result, even if deformation occurs during the manufacturing of the ceramic plate 12, the risk of the heater coil portion 16 being exposed to the heater terminal hole 22 is reduced. Since coil exposure can be prevented in this way, the heater coil portion 16 can be brought closer to the spherical terminal 20 in the horizontal direction, increasing the coil density and preventing the occurrence of cool spots. In other words, exposure of the heater coil portion 16 to the heater terminal hole 22 and the occurrence of localized center cool can be prevented simultaneously. Furthermore, since tensile thermal stress is reduced by preventing the occurrence of center cool, the occurrence of cracks caused by tensile thermal stress can also be prevented.
[0013] The ceramic plate 12 preferably contains aluminum nitride or aluminum oxide in its main parts (i.e., the ceramic substrate) other than embedded components such as the heater circuit 14, spherical terminals 20, and RF electrodes 30, from the viewpoint of excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics close to those of silicon, and more preferably contains aluminum nitride.
[0014] The ceramic plate 12 is disc-shaped. However, the plan view shape of the disc-shaped ceramic plate 12 does not need to be a perfect circle; for example, it may be an imperfect circle with a portion missing, such as an orientation flat. The diameter of the ceramic plate 12 is 220 mm or more, typically 220 to 450 mm, and especially for 300 mm silicon wafers, typically 320 to 380 mm. The thickness of the ceramic plate 12 is typically 10 to 25 mm.
[0015] The heater circuit 14 is embedded in the ceramic plate 12 so as to be approximately parallel to the first surface 12a. Here, the expression "approximately parallel" means that, as shown in Figure 13, the heater coil portion 16, which forms the main part of the heater circuit 14, is parallel to the first surface 12a, and at least a part of the heater wire portion 18 may be either parallel or not parallel to the first surface 12a (see, for example, the heater wire portion 18 which is partially arranged at an angle in Figure 13). Furthermore, "parallel to the first surface 12a" does not mean that it is perfectly parallel to the first surface 12a, but that it is approximately parallel, and specifically, even if the distance from the first surface 12a to the heater coil portion 16 fluctuates within ±20% of the average value of the distance from the first surface 12a to the heater coil portion 16, it will be considered "parallel to the first surface 12a". Note that "the distance from the first surface 12a to the heater coil section 16" refers to the distance from the upper end of the heater coil section 16 on the first surface 12a side (the uppermost point closest to the first surface 12a in the approximately annular cross-section when the heater coil 16 is viewed in cross-section along the coil center axis) to the first surface 12a. Typically, the heater circuit 14 may be a resistive heating element wired in a single continuous line across the entire surface of the ceramic plate 12. The single continuous line configuration can be various known configurations such as alternating forward and backward winding or a spiral. At least one pair of heater terminal holes 22 are formed in the ceramic plate 12 so as to reach each of the spherical terminals 20 from the second surface 12b. A heater rod 24 for supplying power to the heater circuit 14 is inserted into each of the heater terminal holes 22 and electrically connected to each of the spherical terminals 20. The electrical connection between the heater rod 24 and the spherical terminal 20 may be a direct connection, or it may be an indirect connection with other conductive members such as a buffer material 26 and an eyelet 28 interposed between them, as shown in Figure 3, for example. The heater rod 24 extends in a direction away from the first surface 12a. For example, at both ends of the heater circuit 14, the heater rod 24 inserted into the heater terminal hole 22 is connected via the spherical terminal 20 (and optionally a buffer material 26 and an eyelet 28), and the heater rod 24 is electrically connected to a heater power supply (not shown) (via the internal space S of the ceramic shaft 38, if present).When power is supplied from the heater power supply, the heater circuit 14 generates heat and heats the wafer W placed on the first surface 12a.
[0016] The heater circuit 14 includes a heater coil section 16 and a heater wire section 18, as shown in Figure 3. Preferably, the heater coil section 16 and the heater wire section 18 are a continuous, integrated resistive heating element. However, the heater coil section 16 and the heater wire section 18 may be separate resistive heating elements connected to each other via a connection terminal. Using a connection terminal allows for the connection of resistive heating elements of different wire diameters. Preferably, the connection terminal is a conductive member having two through-holes of different diameters, capable of connecting resistive heating elements of different wire diameters. In such a configuration, the electrical connection between the heater coil section 16 and the heater wire section 18 can be ensured by inserting and crimping / / or fixing them into the two through-holes, respectively. The shape of the connection terminal is not particularly limited, but for example, it may be spherical. Note that if the wire diameter of the heater coil section 16 and the wire diameter of the heater wire section 18 are the same, a connection terminal is not necessary.
[0017] The heater coil section 16 is composed of a coil-shaped resistance heating element and is arranged parallel to the first surface 12a. The coil-shaped resistance heating element has a structure in which a resistance heating wire is wound three-dimensionally and can be a heater coil commonly used in ceramic heaters and the like. The winding diameter of the coil is preferably 2.5 to 5.0 mm, more preferably 2.5 to 4.0 mm, and even more preferably 3.0 to 3.5 mm. The wire diameter of the coil is preferably 0.3 to 0.7 mm, more preferably 0.4 to 0.6 mm, and even more preferably 0.4 to 0.5 mm.
[0018] The heater wire portion 18 is composed of a non-coiled, wire-shaped resistance heating element, extends from the heater coil portion 16, and its tip reaches the interior of the spherical terminal 20. When the ceramic plate 12 is viewed in cross-section, the heater wire portion 18 is positioned at the same depth as the lower end of the heater coil portion 16, or at a deeper depth closer to the second surface 12b. In this document, "same" at the above depth position means that a height difference of ±10% or less of the diameter of the spherical terminal 20 is considered "same". The diameter of the spherical terminal 20 is defined as the diameter of a virtual circle C specified by the cross-sectional arc of the spherical terminal 20. That is, the spherical terminal 20 can originally be manufactured in a spherical shape, but when the ceramic plate 12 is processed to form the heater terminal hole 22, a part of the spherical terminal 20 may be shaved off or cut away, resulting in an incomplete spherical shape with a flat portion (hereinafter referred to as "approximately spherical") as shown in Figure 3. The virtual circle C is a circle that is virtually set to fit the arc of the cross-section of this approximately spherical portion. The diameter (wire diameter) of the wire-shaped resistance heating element is preferably 0.3 to 0.7 mm, more preferably 0.4 to 0.6 mm, and even more preferably 0.4 to 0.5 mm.
[0019] The length L1 (see Figures 3 and 13) of the portion of the heater wire portion 18 that is not embedded in the spherical terminal 20 is not particularly limited, but is preferably 2.0 to 3.5 mm, more preferably 2.0 to 3.0 mm, and even more preferably 2.0 to 2.5 mm. The shortest distance L2 (see Figures 3 and 13) between the bottom of the terminal hole 22 and the heater wire portion 18 is not particularly limited, but is preferably 1.0 to 1.5 mm, more preferably 1.0 to 1.3 mm, and even more preferably 1.0 to 1.2 mm.
[0020] In a preferred embodiment of the present invention, the heater wire portion 18 is arranged parallel to the coil centerline Lc of the heater coil portion 16 when the ceramic plate 12 is viewed in cross-section, as shown in Figure 3. This configuration has the advantage of facilitating the formation of the heater circuit 14. Particularly preferred, the heater wire portion 18 is arranged along the terminal centerline Lt of the spherical terminal 20. The terminal centerline Lt is defined as a line parallel to the first surface 12a passing through the center of the circle (i.e., the virtual circle C described above) identified by the cross-sectional arc of the spherical terminal 20 when the ceramic plate 12 is viewed in cross-section.
[0021] In another preferred embodiment of the present invention, the heater wire portion 18 may be provided at an angle or in an arc shape so as to be away from the coil centerline Lc of the heater coil portion 16 when the ceramic plate 12 is viewed in cross-section, as shown in Figure 13. This configuration allows the heater coil portion 16 to be further away from the heater terminal hole 22 (especially the bottom of the hole), further reducing the risk of the heater coil portion 16 being exposed to the heater terminal hole 22 due to deformation during manufacturing, etc. Therefore, the heater coil portion 16 can be brought closer to the spherical terminal 20 in the horizontal direction, further increasing the coil density and more effectively preventing the occurrence of cool spots. The portion of the heater wire portion 18 provided at an angle or in an arc shape is typically located outside the spherical terminal 20, but the portion located inside the spherical terminal 20 may also be provided at an angle or in an arc shape.
[0022] The distance L3 (see Figures 3 and 13) between the center line Lc of the heater coil portion 16 and the center line Lt of the spherical terminal 20 is not particularly limited, but is preferably 1.2 to 4.5 mm, more preferably 1.5 to 3.5 mm, and even more preferably 1.8 to 2.8 mm. The shortest distance L4 (see Figures 3 and 13) between the bottom of the heater terminal hole 22 and the heater coil portion 16 is not particularly limited, but is preferably 1.5 to 4.0 mm, more preferably 1.5 to 3.5 mm, and even more preferably 1.5 to 3.0 mm. The shortest distance L4 is defined as the length of the shortest straight line connecting the vertex or inflection point formed by the heater coil portion 16 and the heater wire portion 18 when the ceramic plate 12 is viewed in cross-section, and the bottom of the heater terminal hole 22.
[0023] As shown in Figures 4 and 5, the heater wire portion 18 does not penetrate the spherical terminal 20 and extend to the outside; therefore, it is preferable that the heater wire portion 18 terminates within the spherical terminal 20. If the heater wire portion 18 protrudes from the spherical terminal 20 as shown in Figure 6, the protruding portion of the heater wire portion 18 can become the starting point for cracks, but by configuring the heater wire portion 18 to terminate within the spherical terminal 20, such a risk can be reduced.
[0024] The spherical terminal 20 is embedded in the ceramic plate 12 and connected to the heater circuit 14. Preferably, the spherical terminal 20 is made of a resistance heating element with the same composition as the coil-shaped resistance heating element (i.e., the heater coil portion 16). As mentioned above, the spherical terminal 20 does not need to be a perfect sphere, and can be an imperfect sphere with a flat portion, i.e., approximately spherical, as shown in Figure 3. The diameter of the spherical terminal 20 (i.e., the diameter of the virtual circle C) is preferably 3.0 to 5.0 mm, more preferably 3.5 to 4.5 mm, and even more preferably 3.5 to 4.0 mm.
[0025] As described above, the heater wire portion 18 is positioned at a depth closer to the second surface 12b, which is the same depth as or deeper than the lower end of the heater coil portion 16, and is preferably provided along the terminal centerline Lt of the spherical terminal 20. Therefore, it is preferable to appropriately set the position of the terminal centerline Lt of the spherical terminal 20 in the depth direction in relation to the lower end of the heater coil portion 16. For example, as shown in Figures 3 and 13, the depth position D of the centerline Lt of the spherical terminal 20 with respect to the lower end of the heater coil portion 16 (the lower end closer to the second surface 12b) is preferably 0 to +2.0 mm, more preferably 0 to +1.5 mm, and even more preferably +0.2 to +1.0 mm, when the depth position closer to the second surface 12b than the lower end of the heater coil portion 16 is considered positive (+).
[0026] When the ceramic plate 12 is viewed from the second surface 12b, it is preferable that the heater coil portion 16 is not located within the area defined by the heater terminal hole 22. This effectively reduces the risk of the heater coil portion 16 being exposed to the heater terminal hole 22 due to deformation during manufacturing or other reasons.
[0027] The resistive heating element constituting the heater circuit 14 (i.e., the heater coil section 16, the heater wire section 18, and the jumper 14c if present) and the spherical terminal 20 preferably includes at least one selected from the group consisting of tungsten, molybdenum, tungsten-molybdenum alloy, tungsten carbide, tungsten carbide-titanium nitride composite material, tungsten carbide-aluminum oxide composite material, and niobium.
[0028] The ceramic heater 10 may be a single-zone heater or a multi-zone heater. In the case of a single-zone heater, the heater circuit 14 may be a single continuous heater circuit capable of heating the ceramic plate 12 as a whole, as shown in Figures 1 and 7. On the other hand, in the case of a multi-zone heater (e.g., a two-zone heater), the ceramic plate 12 may include an inner zone Z1 and an outer zone Z2 when viewed from above, as shown in Figures 8, 9 and 12. The inner zone Z1 is defined as a circular region within a predetermined distance from the center of the ceramic plate 12. The outer zone Z2 is defined as an annular region outside the inner zone Z1. The outer zone Z2 may be divided into a plurality of outer subzones (e.g., 2 to 4 divisions). For example, the outer zone Z2 may consist of a plurality of outer subzones partitioned in an arc shape (e.g., 2 to 4 divisions). Alternatively, the outer zone Z2 may have two or more annular regions of different sizes that do not overlap, arranged concentrically. In this case, the outer zone Z2 will have at least a first outer zone adjacent to the inner zone Z1 and a second outer zone located outside the first outer zone. If necessary, a third or more outer zones may exist outside the second outer zone.
[0029] In the case of a multi-zone heater (e.g., a two-zone heater), the heater circuit 14 may include an inner zone heater circuit 14a, an outer zone heater circuit 14b, and optionally a pair of jumpers 14c, as shown in Figures 8 to 12. That is, the heater circuit 14 may be configured without jumpers 14c, as shown in Figure 12, or it may be configured with jumpers 14c, as shown in Figures 8, 10, and 11. Both the inner zone heater circuit 14a and the outer zone heater circuit 14b include a heater coil section 16 and a heater wire section 18, similar to the heater circuit 14. The inner zone heater circuit 14a is embedded in the inner zone Z1 of the ceramic plate 12. However, the inner zone heater circuit 14a may extend not only to the inner zone Z1 but also to the outer zone Z2, as shown in Figure 12, in which case the inner zone heater circuit 14a may be configured to selectively or preferentially heat the inner zone Z1. The outer zone heater circuit 14b is embedded in the outer zone Z2 of the ceramic plate 12. However, as shown in Figure 12, the outer zone heater circuit 14b may extend not only to the outer zone Z2 but also to the inner zone Z1, in which case the outer zone heater circuit 14b should be configured to selectively or preferentially heat the outer zone Z2. Therefore, the inner zone heater circuit 14a and the outer zone heater circuit 14b may overlap when the ceramic plate 12 is viewed from above, as shown in Figure 12. In either embodiment, it is preferable that each of the inner zone heater circuit 14a and the outer zone heater circuit 14b is arranged in a continuous line when viewed from above. The continuous line shape can be various known shapes such as alternating forward and backward movement or a spiral shape.
[0030] In an embodiment in which the heater circuit 14 has a jumper 14c, the jumper 14c is embedded in the inner zone Z1 of the ceramic plate 12 so as not to contact the inner zone heater circuit 14a, as shown in Figures 8, 10, and 11, and is composed of a wire-shaped resistive heating element extending from the heater wire portion 18 of the outer zone heater circuit 14b. The inner zone heater circuit 14a and the outer zone heater circuit 14b may be arranged on the same plane in cross-sectional view, as shown in Figure 8. Alternatively, the inner zone heater circuit 14a and the outer zone heater circuit 14b may be arranged on different planes in cross-sectional view. As shown in Figures 3 and 11, a pair of spherical terminals 20 are connected to each of the inner zone heater circuit 14a and the jumper 14c, and a heater rod 24 is connected to each of the pair of spherical terminals 20. However, the jumper 14c does not need to be positioned at a depth closer to the second surface 12b, at or below the lower end of the heater coil portion 16 of the outer zone heater circuit 14b. This is because the jumper 14c can be used to keep the heater coil portion 16 of the outer zone heater circuit 14b sufficiently far from the heater terminal hole 22 (especially the bottom of the hole), thus reducing the risk of the heater coil portion 16 of the outer zone heater circuit 14b being exposed to the heater terminal hole 22. In Figure 11, the terminal centerlines Lt of the jumper 14c and the spherical terminal 20 generally coincide in cross-sectional view, but the spherical terminal 20 may be positioned so that the terminal centerline Lt is closer to the second surface 12b by tilting or partially curving the jumper 14c in cross-sectional view. This will keep the jumper 14c away from the bottom of the heater terminal hole 22.
[0031] In an embodiment in which the heater circuit 14 does not have a jumper 14c, as shown in Figure 12, a pair of spherical terminals 20 may be connected to each of the inner zone heater circuit 14a and the outer zone heater circuit 14b, and a heater rod 24 may be connected to each of the pair of spherical terminals 20. That is, a first heater rod 24a is connected to both ends of the inner zone heater circuit 14a, while a second heater rod 24b is connected to both ends of the outer zone heater circuit 14b. The heater rods 24 (i.e., the first heater rod 24a and the second heater rod 24b) are rod-shaped electrode terminals, and the inner zone heater circuit 14a and the outer zone heater circuit 14b are connected to a heater power supply (not shown) via the first heater rod 24a and the second heater rod 24b, respectively. In this embodiment, it is preferable that the inner zone heater circuit 14a and the outer zone heater circuit 14b are arranged on different planes when the ceramic plate 12 is viewed in cross-section, as shown in Figure 12. In this case, it becomes easier to keep the heater coil section 16 away from the bottom of the heater terminal hole 22 in each zone, thus preventing exposure of the heater coil section 16 and allowing more heater coil sections 16 to be placed, resulting in a more effective elimination of cool spots.
[0032] The inner zone heater circuit 14a may be embedded in at least the inner zone Z1 of the ceramic plate 12, generally parallel to the first surface 12a. The inner zone heater circuit 14a includes a heater coil section 16 and a heater wire section 18. A pair of first heater rods 24a may be provided in the inner zone Z1 of the ceramic plate 12 for supplying power to the inner zone heater circuit 14a. Preferably, the first heater rods 24a are connected to both ends of the inner zone heater circuit 14a. There may be two or more pairs of first heater rods 24a. The first heater rods 24a may be the same as the heater rods 24 used in a single-zone heater, and the inner zone heater circuit 14a is connected to a heater power supply (not shown) via the first heater rods 24a.
[0033] The outer zone heater circuit 14b may be embedded in at least the outer zone Z2 of the ceramic plate 12 at the same or a different depth as the inner zone heater circuit 14a and approximately parallel to the first surface 12a. In a preferred embodiment of the present invention, as shown in Figure 8, the outer zone heater circuit 14b may be embedded in the outer zone Z2 of the ceramic plate 12 at the same depth as the inner zone heater circuit 14a and approximately parallel to the first surface 12a. In this case, it is preferable that the coil centerline Lc of the heater coil portion 16 of the inner zone heater circuit 14a, the coil centerline Lc of the heater coil portion 16 of the outer zone heater circuit 14b, and the jumper 14c, if present, are arranged on approximately the same plane. In another preferred embodiment of the present invention, as shown in Figure 12, the outer zone heater circuit 14b may be embedded in the outer zone Z2 of the ceramic plate 12 at a different depth than the inner zone heater circuit 14a and approximately parallel to the first surface 12a. In Figure 12, the outer zone heater circuit 14b is embedded above the inner zone heater circuit 14a (i.e., at a depth closer to the first surface 12a), but this is not limited to this. Therefore, the outer zone heater circuit 14b may also be embedded below the inner zone heater circuit 14a (i.e., at a depth closer to the second surface 12b).
[0034] In embodiments where the heater circuit 14 has a jumper 14c, a pair of second heater rods 24b are provided in the inner zone Z1 of the ceramic plate 12 (particularly in a different location from the first heater rod 24a in the inner region of the ceramic shaft 38 in a plan view) for supplying power to the outer zone heater circuit 14b via the jumper 14c. That is, since the pair of second heater rods 24b are located away from the outer zone heater circuit 14b, the pair of second heater rods 24b are electrically connected to the outer zone heater circuit 14b via the pair of jumpers 14c. There may be two or more pairs of second heater rods 24b. The second heater rods 24b are rod-shaped electrode terminals, and the outer zone heater circuit 14b is connected to a heater power supply (not shown) via the jumper 14c and the second heater rods 24b.
[0035] The outer zone heater circuit 14b may be either a series circuit or a parallel circuit. That is, the outer zone heater circuit 14b may be configured as a series circuit, starting from one of a pair of jumpers 14c in one direction and reaching the other of the pair of jumpers 14c in a single continuous line. Alternatively, the outer zone heater circuit 14b may be configured as a parallel circuit, starting from one of a pair of jumpers 14c in two directions and reaching the other of the pair of jumpers 14c in a single continuous line for each starting direction.
[0036] A pair of jumpers 14c are embedded in the inner zone Z1 of the ceramic plate 12 so as not to contact the inner zone heater circuit 14a, and are electrically connected to the outer zone heater circuit 14b. The pair of jumpers 14c may be embedded at the same or a different depth as the outer zone heater circuit 14b, and approximately parallel to the first surface 12a. The pair of jumpers 14c are separated from each other, with one jumper 14c electrically connecting one end of the second heater rod 24b to one end of the outer zone heater circuit 14b, and the other jumper 14c electrically connecting the other end of the second heater rod 24b to the other end of the outer zone heater circuit 14b. There may be two or more pairs of jumpers 14c.
[0037] The jumper 14c is composed of a wire-like resistive heating element. The specific form of the wire is not particularly limited, but typical examples include straight lines, curves (e.g., arcs), and combinations of straight lines and curves (e.g., straight lines that are partially bent with curvature).
[0038] Preferably, when viewing the ceramic plate 12 from above, the pair of jumpers 14c and the pair of second heater rods 24b are arranged symmetrically with respect to the perpendicular bisector of the line segment connecting the pair of second heater rods 24b, as shown in Figure 10. With this configuration, the length of the power supply path from the pair of second heater rods 24b through the pair of jumpers 14c to the outer zone heater circuit 14b can be made equal, making it easier to achieve better uniform heating.
[0039] A buffer material 26 may be provided at the bottom of the heater terminal hole 22. The buffer material 26 is a metal member provided as a buffer to mitigate the difference in thermal expansion between the spherical terminal 20 and the heater rod 24, and is provided between the spherical terminal 20 and the heater rod 24. A preferred example of the metal constituting the buffer material 26 is an alloy such as Kovar (registered trademark) (Fe-Ni-Co alloy).
[0040] The eyelet 28 is a cylindrical metal member that is housed in or fitted into the heater terminal hole 22. The eyelet 28 serves to guide the smooth insertion of the heater rod 24 into the heater terminal hole 22. The eyelet 28 may be threaded. In this case, the heater rod 24 can also be threaded so that it can be inserted into the eyelet 28 while being screwed in. The metal that makes up the eyelet 28 is not particularly limited, but preferred examples include Ni, W, Mo, W-Mo alloy, etc., with Ni being preferred. The outer circumference of the eyelet 28 may also be threaded. By providing a threaded portion, the heater rod 24 and the eyelet 28 can be screwed together.
[0041] When using cushioning material 26 and / or eyelets 28, it is preferable to braze the spherical terminal 20, heater rod 24, cushioning material 26 and / or eyelets 28 together.
[0042] The ceramic plate 12 may further include an RF electrode 30 and / or an ESC electrode. In this case, the RF electrode 30 and / or ESC electrode are preferably embedded in the ceramic plate 12 at a depth closer to the first surface 12a than the heater circuit 14. The RF electrode 30 enables film deposition by a plasma CVD process when high frequency is applied. The ESC electrode is an abbreviation for electrostatic chuck (ESC) electrode and is also called an electrostatic electrode. When a voltage is applied by an external power supply, the ESC electrode chucking the wafer placed on the surface of the ceramic plate 12 by Johnson-Larbek force. The ESC electrode is preferably a thin, circular electrode with a diameter slightly smaller than the ceramic plate 12, and can be, for example, a mesh electrode made by weaving thin metal wires into a mesh to form a sheet. The ESC electrode may also be used as a plasma electrode. That is, by applying high frequency to the ESC electrode, the ESC electrode can also be used as an RF electrode, and film deposition by a plasma CVD process can be performed. An RF rod 32 or ESC rod for power supply is connected to the RF electrode 30 or ESC electrode. The RF rod 32 or ESC rod is a rod-shaped electrode terminal, and the RF electrode 30 or ESC electrode is connected to an external power supply (not shown) via the RF rod 32 or ESC rod.
[0043] A temperature sensing hole 34 may be provided on the second surface 12b of the ceramic plate 12. The temperature sensing hole 34 can be a thermocouple hole for temperature measurement, which is commonly used in ceramic heaters. Therefore, the temperature of the ceramic plate 12 can be measured by inserting a thermocouple 36 or a resistance thermometer into the temperature sensing hole 34. The temperature sensing hole 34 can be a vertical hole, a horizontal hole, or a combination thereof, and should be formed to suit the area to be measured.
[0044] Optionally, the ceramic shaft 38 may be attached to the second surface 12b of the ceramic plate 12. The ceramic shaft 38 is a cylindrical member having an internal space S, and may have a similar configuration to ceramic shafts used in known ceramic susceptors or ceramic heaters. The internal space S is configured through which heater rods 24, RF rods 32, thermocouples 36, etc., pass. The ceramic shaft 38 is preferably made of the same ceramic material as the ceramic plate 12. Therefore, the ceramic shaft 38 preferably contains aluminum nitride or aluminum oxide, and more preferably aluminum nitride. The upper end surface of the ceramic shaft 38 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 38 is not particularly limited, but is preferably 40 to 60 mm. The inner diameter of the ceramic shaft 38 (diameter of the internal space S) is also not particularly limited, but is preferably 33 to 55 mm. [Examples]
[0045] The present invention will be further described in detail by the following examples. However, the present invention is not limited to the following examples.
[0046] Example 1 (1) Fabrication of ceramic heater Using the components shown below, a ceramic heater 10 was manufactured using known procedures, except for the firing conditions, having the structure of a single-zone heater as shown in Figures 1 and 2 and the terminal connection structure as shown in Figure 3, and satisfying the conditions shown in Tables 1 and 2.
[0047] <Components and their specifications> • Ceramic plate 12: A disc-shaped sintered aluminum nitride body (diameter: 330 mm, thickness: 20 mm) (with a heater circuit 14, spherical terminals 20, and RF electrodes 30 embedded inside) • Heater circuit 14: A circuit consisting of a heater coil section 16 (material: molybdenum, winding diameter: 3.5 mm, wire diameter: 0.5 mm) made of a three-dimensional coil-shaped resistive heating element and a heater wire section 18 made of a non-coil-shaped resistive heating element (material: molybdenum, wire diameter: 0.5 mm), which are embedded at a depth of 10 mm from the first surface 12a according to a predetermined circuit pattern. • Spherical terminal 20: A spherical member made of molybdenum (diameter: 4.0 mm), with a through hole formed along the terminal center line Lt for insertion and connection of the heater wire portion 18. • RF terminal hole: 7mm (M7) nominal diameter, blind hole • Heater terminal hole 22: 7mm (M7) nominal diameter, blind hole • Heater rod 24: Two nickel terminal rods • Cushioning material 26: Metal parts made of Kovar (registered trademark) (Fe-Ni-Co alloy) • Eyelet 28: Nickel cylindrical member • RF electrode 30: A 320 mm diameter disc-shaped molybdenum electrode embedded at a depth of 1.0 mm from the first surface 12a of the ceramic plate 12. • RF Rod 32: Nickel terminal rod • Ceramic shaft 38: Cylindrical aluminum nitride sintered body (height: 172mm, outer diameter: 42mm, inner diameter: 36mm)
[0048] The ceramic plate 12, in which the heater circuit 14, spherical terminal 20, and RF electrode 30 described above are embedded, was manufactured by the following procedure. First, aluminum nitride powder was press-molded to obtain a first aluminum nitride compact. On the obtained first aluminum nitride compact, aluminum nitride powder, the heater circuit 14, and the spherical terminal 20 were arranged according to a predetermined circuit pattern and press-molded to obtain a second aluminum nitride compact in which the heater circuit 14 and spherical terminal 20 were embedded. At this time, the arrangement of the heater circuit 14 and the spherical terminal 20 was carried out by first manufacturing a wiring assembly consisting of the heater circuit 14 and the spherical terminal 20 by inserting and connecting the ends of the heater wire portions 18 into the through holes of the spherical terminal 20, and then placing this wiring assembly on the first aluminum nitride compact. On the obtained second aluminum nitride compact, aluminum nitride powder and the RF electrode 30 were arranged and press-molded to obtain a third aluminum nitride compact in which the RF electrode 30 was further embedded. Thus, a press-molded body made of aluminum nitride powder with a heater circuit 14, spherical terminals 20, and RF electrodes 30 embedded in it was obtained, as shown in Figure 1. The obtained press-molded body (laminated body) was fired under the following conditions in a nitrogen atmosphere: ·Maximum temperature: 1810℃ • Holding time at maximum temperature: 5 hours • Heating rate: Adjustable within the range of 10-120°C / min (a temperature range encompassing the individual heating rates in multiple heating stages) • Firing pressure: 90 kg / cm² 2 By firing, a ceramic plate 12 was obtained in which a heater circuit 14, a spherical terminal 20, and an RF electrode 30 were embedded inside.
[0049] (2) Evaluation Various evaluations were performed on the resulting ceramic heaters.
[0050] <Maximum temperature difference within the surface> A ceramic heater 10 was installed inside the chamber of the film deposition apparatus. The chamber was evacuated and N2 gas was introduced, setting the N2 gas pressure inside the chamber to 5 Torr. By supplying power to the heater circuit 14 via the heater rod 24, the ceramic heater 10 was heated to a set temperature of 550°C. 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 highest and lowest temperatures (i.e., the maximum in-plane temperature difference) was determined as an indicator of uniformity. The results are shown in Table 2.
[0051] <Cool Spot> Based on the temperature distribution map obtained above, we checked for the presence of a localized cool spot in the central region of the ceramic plate 12, with a radius of 30 mm (i.e., a diameter of 60 mm) from the center. As shown in Table 2, no cool spots were observed in this example.
[0052] <Cracks occurring during operation> A ceramic heater 10 was installed inside the chamber of the film deposition apparatus. The chamber was evacuated and N2 gas was introduced, setting the N2 gas pressure inside the chamber to 5 Torr. By supplying power to the heater circuit 14 via the heater rod 24, the ceramic heater 10 was heated from room temperature (20°C) to a set temperature of 550°C at a heating rate of 20°C / min. After maintaining the temperature at 550°C for 10 minutes, the power supply was stopped and it was allowed to cool to room temperature (20°C). This cycle of heating from 20°C to 550°C and then cooling to 20°C was performed a total of 100 times. Subsequently, the presence or absence of cracks in the ceramic plate 12 was examined using an ultrasonic flaw detection device. As shown in Table 2, it was confirmed that no cracks had occurred in this example.
[0053] <Coil exposure during manufacturing> When a heater terminal hole 22 was drilled by grinding in a ceramic plate 12 in which a heater circuit 14, spherical terminal 20, and RF electrode 30 are embedded, so as to reach a part of the spherical terminal 20 from the second surface 12b, we investigated whether there were any cases in which the heater coil portion 16 was exposed in the heater terminal hole 22. As a result, as shown in Table 2, in this example, there were no cases in which the heater coil portion 16 was exposed in the heater terminal hole 22.
[0054] Example 2 The ceramic heater 10 was fabricated in the same manner as in Example 1, except that it had a structure without a ceramic shaft 38 as shown in Figure 7, and that it satisfied the conditions shown in Tables 1 and 2. Therefore, the ceramic heater 10 in this example has a structure corresponding to Figures 2, 3, and 7. The results are shown in Table 2.
[0055] Example 3 (1) Fabrication of ceramic heater Using the components shown below, a ceramic heater 10 was manufactured using a method appropriately modified from Example 1, having the structure of a planar two-zone heater as shown in Figures 8 and 9, the terminal connection structure as shown in Figures 3, 10, and 11, and satisfying the conditions shown in Tables 1 and 2.
[0056] <Components and their specifications> • Ceramic plate 12: A disc-shaped sintered aluminum nitride body (diameter: 330 mm, thickness: 20 mm) (with an inner zone heater circuit 14a, an outer zone heater circuit 14b, a jumper 14c, a spherical terminal 20, and an RF electrode 30 embedded inside) • Inner Zone Z1: A circular area with a diameter of 216 mm located in the center of ceramic plate 12. • Outer zone Z2: The annular region outside the inner zone Z1 in the ceramic plate 12. • Inner zone heater circuit 14a: A circuit consisting of a heater coil section 16 (material: molybdenum, winding diameter: 3.5 mm, wire diameter: 0.5 mm) made of a three-dimensional coil-shaped resistive heating element and a heater wire section 18 made of a non-coil-shaped resistive heating element (material: molybdenum, wire diameter: 0.5 mm), which are embedded in the inner zone Z1 at a depth of 6.5 mm from the first surface 12a according to a predetermined circuit pattern. • Outer zone heater circuit 14b: A circuit consisting of a heater coil section 16 (material: molybdenum, winding diameter: 3.5 mm, wire diameter: 0.5 mm) made of a three-dimensional coil-shaped resistive heating element and a heater wire section 18 made of a non-coil-shaped resistive heating element (material: molybdenum, wire diameter: 0.5 mm), which are embedded in the outer zone Z2 at a depth of 6.5 mm from the first surface 12a according to a predetermined circuit pattern. • Jumper 14c: A pair of roughly linear, symmetrical resistive heating wires (material: molybdenum, wire diameter: 0.5 mm) embedded in the circuit pattern shown in Figure 10, at a depth of 6.5 mm from the first surface 12a of the inner zone Z1. • Spherical terminal 20: A spherical member made of molybdenum (diameter: 4.0 mm), with a through hole formed along the terminal center line Lt for insertion and connection of the heater wire portion 18. • RF terminal hole: 7mm (M7) nominal diameter, blind hole • Heater terminal hole 22: 7mm (M7) nominal diameter, blind hole • First heater rod 24a: Two nickel terminal rods • Second heater rod 24b: Two nickel terminal rods • Cushioning material 26: Metal parts made of Kovar (registered trademark) (Fe-Ni-Co alloy) • Eyelet 28: Nickel cylindrical member • RF electrode 30: A 320 mm diameter disc-shaped molybdenum electrode embedded at a depth of 1.0 mm from the first surface 12a of the ceramic plate 12. • RF Rod 32: Nickel terminal rod • Ceramic shaft 38: Cylindrical aluminum nitride sintered body (height: 172mm, outer diameter: 42mm, inner diameter: 36mm)
[0057] (2) Evaluation The obtained ceramic heaters were evaluated in the same manner as in Example 1. The results are shown in Table 2.
[0058] Example 4 (1) Fabrication of ceramic heater Using the components shown below, a ceramic heater 10 was manufactured using a method appropriately modified from Example 1, having the structure of a stacked two-zone heater as shown in Figures 9 and 12, the terminal connection structure as shown in Figure 13, and satisfying the conditions shown in Tables 1 and 2.
[0059] <Components and their specifications> • Ceramic plate 12: A disc-shaped sintered aluminum nitride body (diameter: 330 mm, thickness: 20 mm) (with an inner zone heater circuit 14a, an outer zone heater circuit 14b, a jumper 14c, a spherical terminal 20, and an RF electrode 30 embedded inside) • Inner Zone Z1: A circular area with a diameter of 216 mm located in the center of ceramic plate 12. • Outer zone Z2: The annular region outside the inner zone Z1 in the ceramic plate 12. • Inner zone heater circuit 14a: A circuit consisting of a heater coil section 16 (material: molybdenum, winding diameter: 3.5 mm, wire diameter: 0.5 mm) made of a three-dimensional coil-shaped resistance heating element and a heater wire section 18 made of a non-coil-shaped resistance heating element (material: molybdenum, wire diameter: 0.5 mm), which are embedded in the ceramic plate 12 at a depth of 11.5 mm from the first surface 12a of the inner zone Z1 and outer zone Z2 (area with a diameter of 320 mm) according to a predetermined circuit pattern. (However, the heater coil section 16 is arranged such that the coil pitch becomes shorter (the coils become denser) as it approaches the center of the ceramic plate 12, so that the inner zone Z1 can be heated selectively or preferentially.) • Outer zone heater circuit 14b: A circuit consisting of a heater coil section 16 (material: molybdenum, winding diameter: 3.5 mm, wire diameter: 0.5 mm) made of a three-dimensional coil-shaped resistance heating element and a heater wire section 18 made of a non-coil-shaped resistance heating element (material: molybdenum, wire diameter: 0.5 mm), embedded in the ceramic plate 12 at a depth of 6.5 mm from the first surface 12a of the inner zone Z1 and outer zone Z2 (area with a diameter of 320 mm) according to a predetermined circuit pattern (however, the heater coil section 16 is arranged such that the coil pitch becomes shorter (the coils become denser) as it approaches the outer circumference of the ceramic plate 12, so that the outer zone Z2 can be heated selectively or preferentially.) • Spherical terminal 20: A spherical member made of molybdenum (diameter: 4.5 mm), with a through hole formed along the terminal center line Lt for insertion and connection of the heater wire portion 18. • RF terminal hole: 7mm (M7) nominal diameter, blind hole • Heater terminal hole 22: 7mm (M7) nominal diameter, blind hole • First heater rod 24a: Two nickel terminal rods • Second heater rod 24b: Two nickel terminal rods • Cushioning material 26: Metal parts made of Kovar (registered trademark) (Fe-Ni-Co alloy) • Eyelet 28: Nickel cylindrical member • RF electrode 30: A 320 mm diameter disc-shaped molybdenum electrode embedded at a depth of 1.0 mm from the first surface 12a of the ceramic plate 12. • RF Rod 32: Nickel terminal rod • Ceramic shaft 38: Cylindrical aluminum nitride sintered body (height: 172mm, outer diameter: 42mm, inner diameter: 36mm)
[0060] The ceramic plate 12, in which the inner zone heater circuit 14a, outer zone heater circuit 14b, spherical terminal 20, and RF electrode 30 described above are embedded, was manufactured by the following procedure. First, aluminum nitride powder was press-molded to obtain a first aluminum nitride compact. On the obtained first aluminum nitride compact, aluminum nitride powder, the inner zone heater circuit 14a, and the spherical terminal 20 were arranged according to a predetermined circuit pattern and press-molded to obtain a second aluminum nitride compact in which the inner zone heater circuit 14a and the spherical terminal 20 were embedded. At this time, the arrangement of the inner zone heater circuit 14a and the spherical terminal 20 was carried out by first manufacturing a wiring assembly consisting of the inner zone heater circuit 14a and the spherical terminal 20 by inserting and connecting the ends of the heater wire portions 18 into the through holes of the spherical terminal 20, and then placing this wiring assembly on the first aluminum nitride compact. A third aluminum nitride compact was obtained by placing aluminum nitride powder, an outer zone heater circuit 14b, and a spherical terminal 20 on the obtained second aluminum nitride compact and press molding it, thereby further embedding the outer zone heater circuit 14b inside. At this time, the placement of the outer zone heater circuit 14b and the spherical terminal 20 was carried out by first fabricating a wiring assembly consisting of the outer zone heater circuit 14b and the spherical terminal 20 by inserting and connecting the ends of the heater wire portions 18 into the through holes of the spherical terminal 20, and then placing this wiring assembly on the second aluminum nitride compact. A fourth aluminum nitride compact was obtained by placing aluminum nitride powder and an RF electrode 30 on the obtained third aluminum nitride compact and press molding it, thereby further embedding the RF electrode 30 inside. Thus, a press-molded body consisting of an aluminum nitride compact in which the inner zone heater circuit 14a, outer zone heater circuit 14b, spherical terminal 20, and RF electrode 30 are embedded was obtained as shown in Figure 12. The resulting press-molded body (laminated body) is fired under the following conditions in a nitrogen atmosphere: ·Maximum temperature: 1810℃ • Holding time at maximum temperature: 5 hours • Heating rate: Adjustable within the range of 10-120°C / min (a temperature range encompassing the individual heating rates in multiple heating stages) • Firing pressure: 100 kg / cm² 2 By firing, a ceramic plate 12 was obtained in which a heater circuit 14, a spherical terminal 20, and an RF electrode 30 were embedded inside.
[0061] (2) Evaluation The obtained ceramic heaters were evaluated in the same manner as in Example 1. The results are shown in Table 2.
[0062] Example 5 (comparison) A ceramic heater 10 was manufactured in the same manner as in Example 1, except that the depth position of the heater wire portion 18 was changed to coincide with the center line Lc of the heater coil portion 16 so as to satisfy the conditions shown in Figure 14 and Tables 1 and 2. Therefore, the ceramic heater 10 in this example has a structure corresponding to Figures 1, 2 and 14. As shown in Table 2, the result was poor temperature uniformity, and cool spots and resulting cracks occurred.
[0063] Example 6 (comparison) A ceramic heater 10 was manufactured in the same manner as in Example 1, except that the depth position of the heater wire portion 18 was changed to be above the lower end of the heater coil portion 16 and below the center line Lc of the heater coil portion 16, so as shown in Figure 15 and satisfying the conditions shown in Tables 1 and 2. Therefore, the ceramic heater 10 in this example has a structure corresponding to Figures 1, 2 and 15. As a result, as shown in Table 2, temperature uniformity was poor and cool spots occurred, and in some cases the heater coil portion 16 was exposed to the heater terminal hole 22 during manufacturing.
[0064] [Table 1]
[0065] [Table 2] [Explanation of Symbols]
[0066] 10: Ceramic heater, 12: Ceramic plate, 12a: First surface, 12b: Second surface, 14: Heater circuit, 14a: Inner zone heater circuit, 14b: Outer zone heater circuit, 14c: Jumper, 16: Heater coil section, 18: Heater wire section, 20: Spherical terminal, 22: Heater terminal hole, 24: Heater rod, 24a: First heater rod, 24b: Second heater rod, 26: Cushioning material, 28: Eyelet, 30: RF electrode, 32: RF rod, 34: Temperature sensing hole, 36: Thermocouple, 38: Ceramic shaft, W: Wafer, D: Depth position, C: Virtual circle, Lt: Terminal centerline, Lc: Coil centerline, Z1: Inner zone, Z2: Outer zone, S: Internal space
Claims
1. A ceramic plate having a first surface on which a wafer is placed and a second surface facing the first surface, A heater circuit embedded in the ceramic plate, At least one pair of spherical terminals embedded in the ceramic plate and connected to the heater circuit, The ceramic plate has at least one pair of heater terminal holes formed on its second surface so as to reach each of the spherical terminals, A pair of heater rods for supplying power to the heater circuit, which are inserted into each of the heater terminal holes and electrically connected to each of the spherical terminals, and which extend in a direction away from the first surface, Equipped with, The heater circuit described above, A heater coil section, which is arranged parallel to the first surface and is composed of a coil-shaped resistance heating element, A heater wire portion is made up of a non-coiled, strand-shaped resistance heating element that extends from the heater coil portion and whose tip reaches the inside of the spherical terminal, Includes, When the ceramic plate is viewed in cross-section, the heater wire portion is positioned at a depth closer to the second surface, at the same depth as or deeper than the lower end of the heater coil portion. A ceramic heater in which the length L1 of the portion of the heater wire that is not embedded in the spherical terminal is 2.0 to 3.5 mm.
2. A ceramic plate having a first surface on which a wafer is placed and a second surface facing the first surface, A heater circuit embedded in the ceramic plate, At least one pair of spherical terminals embedded in the ceramic plate and connected to the heater circuit, The ceramic plate has at least one pair of heater terminal holes formed on its second surface so as to reach each of the spherical terminals, A pair of heater rods for supplying power to the heater circuit, which are inserted into each of the heater terminal holes and electrically connected to each of the spherical terminals, and which extend in a direction away from the first surface, Equipped with, The heater circuit described above, A heater coil section, which is arranged parallel to the first surface and is composed of a coil-shaped resistance heating element, A heater wire portion is made up of a non-coiled, strand-shaped resistance heating element that extends from the heater coil portion and whose tip reaches the inside of the spherical terminal, Includes, When the ceramic plate is viewed in cross-section, the heater wire portion is positioned at a depth closer to the second surface, at the same depth as or deeper than the lower end of the heater coil portion. A ceramic heater in which the shortest distance L4 between the bottom of the heater terminal hole and the heater coil portion is 1.5 to 4.0 mm, and the shortest distance L4 is defined as the length of the shortest straight line connecting the vertex or inflection point formed by the heater coil portion and the heater wire portion to the bottom of the heater terminal hole when the ceramic plate is viewed in cross-section.
3. The ceramic heater according to claim 1 or 2, wherein, when the ceramic plate is viewed in cross-section, a line parallel to the first surface passing through the center of a virtual circle identified by the cross-sectional arc of the spherical terminal is defined as the terminal centerline, and the heater wire portion is arranged along the terminal centerline.
4. The ceramic heater according to claim 1 or 2, wherein the ceramic plate comprises aluminum nitride or aluminum oxide.
5. The ceramic heater according to claim 1 or 2, wherein the spherical terminal is composed of a resistance heating element having the same composition as the coil-shaped resistance heating element.
6. The ceramic heater according to claim 1 or 2, wherein the resistive heating element includes at least one selected from the group consisting of tungsten, molybdenum, tungsten-molybdenum alloy, tungsten carbide, tungsten carbide-titanium nitride composite material, tungsten carbide-aluminum oxide composite material, and niobium.
7. The ceramic heater according to claim 1 or 2, wherein when the ceramic plate is viewed from the second surface in plan view, the heater coil portion is not located within the region defined by the heater terminal hole.
8. The ceramic heater according to claim 1 or 2, further comprising a cylindrical ceramic shaft attached to the second surface of the ceramic plate and having an internal space.
9. The ceramic heater according to claim 1 or 2, wherein the heater wire portion does not penetrate the spherical terminal and extend to the outside thereof, and therefore the heater wire portion terminates within the spherical terminal.
10. The ceramic plate includes an inner zone defined as a circular region within a predetermined distance from the center of the ceramic plate when viewed from above, and an outer zone defined as an annular region outside the inner zone. The heater circuit described above, An inner zone heater circuit, which includes the heater coil portion and the heater wire portion, is embedded in the inner zone of the ceramic plate. An outer zone heater circuit, which includes the heater coil portion and the heater wire portion, is embedded in the outer zone of the ceramic plate. Includes, The ceramic heater according to claim 1 or 2, wherein the pair of spherical terminals are connected to each of the inner zone heater circuit and the outer zone heater circuit, and the heater rod is connected to each of the pair of spherical terminals.
11. The ceramic heater according to claim 10, wherein the inner zone heater circuit and the outer zone heater circuit are arranged on different planes when the ceramic plate is viewed in cross-section.
12. The ceramic plate includes an inner zone defined as a circular region within a predetermined distance from the center of the ceramic plate when viewed from above, and an outer zone defined as an annular region outside the inner zone. The heater circuit described above, An inner zone heater circuit, which includes the heater coil portion and the heater wire portion, is embedded in the inner zone of the ceramic plate. An outer zone heater circuit, which includes the heater coil portion and the heater wire portion, is embedded in the outer zone of the ceramic plate. A pair of jumpers are embedded in the inner zone of the ceramic plate so as not to contact the inner zone heater circuit, and each jumper is composed of a strand-shaped resistive heating element extending from the heater strand portion of the outer zone heater circuit. A ceramic heater according to claim 1 or 2, comprising the inner zone heater circuit and the jumper, each of which is connected to the pair of spherical terminals, and each of the pair of spherical terminals is connected to the heater rod (however, the jumper does not have to be located at the same depth as or deeper than the lower end of the heater coil portion of the outer zone heater circuit, closer to the second surface).
13. The ceramic heater according to claim 12, wherein the inner zone heater circuit and the outer zone heater circuit are arranged on the same plane when the ceramic plate is viewed in cross-section.
14. The ceramic heater according to claim 12, wherein the inner zone heater circuit and the outer zone heater circuit are arranged on different planes when the ceramic plate is viewed in cross-section.