Multi-zone ceramic heater

Abstract

Provided is a multi-zone ceramic heater capable of achieving good thermal uniformity while suppressing breakage. This ceramic heater comprises: a ceramic plate including an inner zone and an outer zone; an inner zone heater circuit embedded in the inner zone; an outer zone heater circuit embedded in the outer zone at a different depth position than the inner zone heater circuit; a pair of first power supply terminals for supplying power to the inner zone heater circuit; a pair of second power supply terminals for supplying power to the outer zone heater circuit; and a pair of jumpers that are embedded in the inner zone of the ceramic plate, one of the jumpers connecting one of the second power supply terminals and the outer zone heater circuit at a first connection part, and the other connecting the other of the second power supply terminals and the outer zone heater circuit at a second connection part in a position different than the first connection part. Each of the inner zone heater circuit, the outer zone heater circuit, and the jumpers is composed of a resistive heating element. The thickness of the jumpers is 1.2-3.0 times the thickness of the outer zone heater circuit.

Description

Multi-zone ceramic heater

[0001] The present disclosure relates to a multi-zone ceramic heater.

[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. Multi-zone ceramic heaters, which have multiple heating zones, are also known as ceramic heaters.

[0003] Patent Document 1 (JP 2020-191315 A) discloses a heating device including a first heater electrode disposed in a substantially circular first region and a second heater electrode disposed in a substantially annular second region surrounding the first heater electrode, both of which are disposed within a plate-shaped member. The heating device includes a common driver electrode electrically connected to all of the heater electrodes and to a common power supply terminal, the common driver electrode having a thick portion that is thicker than the thickness of other portions of the common driver electrode. In other words, the disclosure discloses that the thickness of the common driver electrode varies across its surface.

[0004] Patent Document 2 (JP 2015-191837 A) discloses a laminated heating element having an inner heater and an outer heater surrounding the inner heater. This laminated heating element includes a ceramic main body, a heater built into the main body, a terminal attached to one end of the main body in the thickness direction, and a power supply path that supplies power from the terminal to the heater. The power supply path is composed of a combination of multiple conductive layers and multiple through vias provided within the main body. Of the multiple conductive layers, conductive layer X, which is located closer to the terminal than the heater, has a connection portion P with through via α and a connection portion Q with through via β, and includes at least a portion of the path connecting connection portion P and connection portion Q. This conductive layer X has a region AX with a thickness greater than that of its surroundings.

[0005] JP 2020-191315 A JP 2015-191837 A

[0006] Ceramic heaters are required to minimize temperature differences across the wafer-mounted surface (i.e., thermal uniformity). In particular, with the recent trend toward finer process miniaturization and higher integration, ceramic heaters are required to achieve even greater thermal uniformity. From this perspective, it is desirable to minimize the temperature difference between areas where a resistance heating element is present and areas where it is not. To achieve this, it is preferable to distribute the resistance heating element throughout the entire ceramic heater, and a printed resistance heating element is a promising candidate. However, in multi-zone ceramic heaters in which a ceramic shaft is disposed in the center of a ceramic plate with a thin resistance heating element embedded, localized hot spots and cool spots are likely to occur in the electrical connection path (jumper connection) from the center of the plate to the resistance heating element on the periphery of the plate due to heat generation in the electrical connection path itself. This has resulted in a problem of poor thermal uniformity across the entire plate of the multi-zone ceramic heater.

[0007] The present inventors have now discovered that in a multi-zone ceramic heater having an inner zone heater circuit, an outer zone heater circuit, and a jumper, by setting the thickness of the jumper within a range of 1.2 to 3.0 times the thickness of the outer zone heater circuit, it is possible to achieve good thermal uniformity while suppressing breakage during manufacturing, etc.

[0008] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a multi-zone ceramic heater that can achieve good temperature uniformity while suppressing breakage during manufacturing, etc.

[0009] According to the present disclosure, the following aspects are provided: [Aspect 1] A disc-shaped ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface, the ceramic plate including, in a plan view of the ceramic plate, an inner zone defined as a circular region within a predetermined distance from the center of the ceramic plate and an outer zone defined as an annular region outside the inner zone, an inner zone heater circuit embedded in the inner zone of the ceramic plate parallel to the first surface, an outer zone heater circuit embedded in the outer zone of the ceramic plate parallel to the first surface at a depth different from that of the inner zone heater circuit, a pair of first power supply terminals provided in a center of the inner zone of the ceramic plate for supplying power to the inner zone heater circuit, and a pair of second power supply terminals provided in a center of the inner zone of the ceramic plate for supplying power to the outer zone heater circuit. a pair of jumpers separated from each other and embedded in the inner zone of the ceramic plate at the same depth as the outer zone heater circuit and parallel to the first surface, one of the pair of jumpers electrically connecting one of the second power supply terminals to the outer zone heater circuit at a first connection portion, and the other of the pair of jumpers electrically connecting the other of the second power supply terminals to the outer zone heater circuit at a second connection portion located at a position different from the first connection portion; wherein the inner zone heater circuit, the outer zone heater circuit, and the jumpers are each a thin element made of a resistance heating element selected from the group consisting of a printed pattern, a foil, a punched metal, and a mesh, and the thickness of the jumpers is 1.2 to 3.0 times the thickness of the outer zone heater circuit.[Aspect 2] The multi-zone ceramic heater according to Aspect 1, wherein the outer zone is composed of a plurality of outer subzones partitioned into arc-shaped sections, and linear boundary regions, which are not crossed by the outer zone heater circuit, exist between adjacent outer subzones in the circumferential direction in the radial direction of the ceramic plate so as not to completely divide the outer zone, and the outer zone heater circuit starts from the first connecting portion in one or two directions, and in each starting direction, in a unicursal manner, passes through substantially the entire area of ​​each of the plurality of outer subzones, meandering while alternately progressing in the circumferential direction and turning back just before the boundary region, before reaching the second connecting portion. [Aspect 3] The multi-zone ceramic heater according to Aspect 2, wherein, in a plan view of the ceramic plate, the boundary region and the second connection region are spaced apart from each other such that, for each of the first and second connection regions, an angle formed between a line passing through the circumferential center of the boundary region closest to the connection region and the center of the ceramic plate and a line passing through the circumferential center of the connection region and the center of the ceramic plate is 20° or greater. [Aspect 4] The multi-zone ceramic heater according to any one of Aspects 1 to 3, wherein, when each of the first and second connection regions is considered to be an arc constituting the outer circumferential circle of the inner zone, the central angle of each of the arcs is within the range of 6.0 to 10.0°. [Aspect 5] The multi-zone ceramic heater according to any one of Aspects 1 to 4, wherein the outer zone heater circuit is arranged to form a series circuit, starting in one direction from the first connection region and reaching the second connection region in a unicursal manner. [Aspect 6] The multi-zone ceramic heater according to any one of Aspects 1 to 4, wherein the outer zone heater circuits are arranged so as to form parallel circuits, starting from the first connection portion in two directions and reaching the second connection portion in a unicursal manner in each starting direction. [Aspect 7] The multi-zone ceramic heater according to any one of Aspects 1 to 6, wherein, when the ceramic plate is viewed from above, the pair of jumpers and the pair of second power supply terminals are arranged symmetrically with respect to a perpendicular bisector of a line segment connecting the pair of second power supply terminals.[Aspect 8] The multi-zone ceramic heater according to any one of Aspects 1 to 7, wherein the inner zone heater circuit, the outer zone heater circuit, and the jumper are each in the form of a printed pattern. [Aspect 9] The multi-zone ceramic heater according to any one of Aspects 1 to 8, wherein the outer zone heater circuit has a constant thickness in an in-plane direction, and the jumper has a constant thickness in an in-plane direction. [Aspect 10] The multi-zone ceramic heater according to any one of Aspects 1 to 9, further comprising an RF electrode and / or an ESC electrode embedded in the ceramic plate at a depth closer to the first surface than the inner zone heater circuit and the jumper. [Aspect 11] The multi-zone ceramic heater according to any one of Aspects 1 to 10, wherein the ceramic plate comprises aluminum nitride or aluminum oxide. [Aspect 12] The multi-zone ceramic heater according to any one of Aspects 1 to 11, further comprising a cylindrical ceramic shaft with an internal space, concentrically attached to the second surface of the ceramic plate. [Aspect 13] The multi-zone ceramic heater of any one of Aspects 1 to 12, wherein the resistance heating element comprises at least one selected from the group consisting of tungsten, molybdenum, a tungsten-molybdenum alloy, tungsten carbide, a tungsten carbide-titanium nitride composite, and a tungsten carbide-aluminum oxide composite. [Aspect 14] The multi-zone ceramic heater of any one of Aspects 1 to 13, wherein the jumper has a thickness that is 1.8 to 3.0 times the thickness of the outer zone heater circuits.

[0010] 1 is a schematic top view showing an example of a multi-zone ceramic heater according to the present invention; FIG. 2 is a schematic cross-sectional view showing the multi-zone ceramic heater shown in FIG. 1; FIG. 3 is a schematic top view of a simplified multi-zone ceramic heater for conceptually explaining a series circuit; FIG. 4 is a schematic top view of a simplified multi-zone ceramic heater for conceptually explaining a parallel circuit; FIG. 5 is a schematic top view of another example of a multi-zone ceramic heater, corresponding to Example 1; FIG. 6 is a schematic top view of another example of a multi-zone ceramic heater, corresponding to Examples 2 and 10; FIG. 7 is a schematic top view of another example of a multi-zone ceramic heater, corresponding to Examples 3 and 5; FIG. 8 is a schematic top view of another example of a multi-zone ceramic heater, corresponding to Examples 4, 7 and 8; FIG. 9 is a schematic top view of another example of a multi-zone ceramic heater, corresponding to Example 6; FIG. 10 is a schematic cross-sectional view of the multi-zone ceramic heater shown in FIG. 11, corresponding to Example 9 (Comparative Example);

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

[0012] 1 and 2 show one embodiment of a multi-zone ceramic heater. The multi-zone ceramic heater 10 shown in FIGS. 1 and 2 includes a ceramic plate 12, an inner zone heater circuit 14, an outer zone heater circuit 16, a pair of first power supply terminals 18, a pair of second power supply terminals 20, and a pair of jumpers 22. The ceramic plate 12 is disk-shaped and has a first surface 12a on which a wafer W is placed and a second surface 12b opposite the first surface 12a. When viewed in a plan view, the ceramic plate 12 includes an inner zone Z1 defined as a circular region within a predetermined distance from the center of the ceramic plate 12, and an outer zone Z2 defined as an annular region outside the inner zone Z1. An inner zone heater circuit 14 is embedded in the inner zone Z1 of the ceramic plate 12 parallel to the first surface 12a, while an outer zone heater circuit 16 is embedded in the outer zone Z2 of the ceramic plate 12 parallel to the first surface 12a at a different depth from the inner zone heater circuit 14. A pair of first power supply terminals 18 are terminals for supplying power to the inner zone heater circuit 14 and are provided in the center of the inner zone Z1 of the ceramic plate 12. A pair of second power supply terminals 20 are terminals for supplying power to the outer zone heater circuit 16 and are provided in the center of the inner zone Z1 of the ceramic plate 12. A pair of jumpers 22 are separated from each other and embedded in the inner zone Z1 of the ceramic plate 12 parallel to the first surface 12a at the same depth as the outer zone heater circuit 16. One of the pair of jumpers 22 electrically connects one of the second power supply terminals 20 to the outer zone heater circuit 16 at a first connection portion 24, while the other of the pair of jumpers 22 electrically connects the other of the second power supply terminals 20 to the outer zone heater circuit 16 at a second connection portion 26 located at a position different from the first connection portion 24. Each of the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22 is a thin element made of a resistance heating element selected from the group consisting of a printed pattern, a foil, a punched metal, and a mesh. The thickness of the jumper 22 is 1.2 to 3.0 times the thickness of the outer zone heater circuit 16.In this way, in the multi-zone ceramic heater 10 having the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22, by setting the thickness of the jumper 22 within the range of 1.2 to 3.0 times the thickness of the outer zone heater circuit 16, it is possible to achieve good thermal uniformity while suppressing breakage during manufacturing, etc.

[0013] As mentioned above, with the recent trend toward finer process miniaturization and higher integration, ceramic heaters are required to have even greater thermal uniformity (e.g., a maximum temperature difference of 1°C or less across the surface). Therefore, it is preferable to distribute resistance heating elements throughout the entire ceramic heater, and printed resistance heating elements are a promising candidate for this purpose. However, in multi-zone ceramic heaters in which a ceramic shaft is disposed in the center of a ceramic plate in which thin resistance heating elements (e.g., thickness of 100 μm or less) are embedded, localized hot spots and cool spots are likely to occur in the electrical connection path (jumper connection) from the center of the plate to the resistance heating elements on the periphery of the plate due to heat generated by the electrical connection path itself. This has resulted in a problem of poor thermal uniformity throughout the plate portion of the multi-zone ceramic heater. In this regard, according to the present invention, such thermal uniformity can be improved by making the thickness of the jumper 22 at least 1.2 times the thickness of the outer zone heater circuit 16. This is because making the jumper 22 thicker than the outer zone heater circuit 16 reduces the resistance of the jumper 22, which, like the inner zone heater circuit 14 and the outer zone heater circuit 16, is composed of a resistive heating element. As a result, the amount of heat generated in the jumper 22 can be kept low, leading to the reduction of localized hot spots. However, it is undesirable for the jumper 22 to be too thick compared to the outer zone heater circuit 16. For example, if the thickness of the jumper 22 is more than three times (e.g., four times or more) the thickness of the outer zone heater circuit 16, a large step will be created at the connection between the jumper 22 and the outer zone heater circuit 16 (i.e., the first connection portion 24 and the second connection portion 26) where the thickness of the resistive heating element changes. Stress will concentrate at this step, potentially causing damage. This stress concentration at the step and resulting damage are likely to occur during the manufacture of the ceramic heater (particularly when firing the ceramic plate or joining the ceramic shaft to the ceramic plate). Damage is also anticipated during use of the ceramic heater (i.e., during operation of the semiconductor manufacturing equipment). For example, in the former case, stress generated in the ceramic plate molding process is amplified in the ceramic plate firing process, and stress tends to concentrate in the stepped portion.In the latter case, the ceramic plate is exposed to high temperatures during operation of the semiconductor manufacturing equipment, and thermal expansion of the ceramic plate tends to cause stress to concentrate at the stepped portion. In this regard, by making the thickness of the jumper 22 3.0 times or less the thickness of the outer zone heater circuit 16, damage caused by such stress concentration can be effectively suppressed. For the reasons described above, the thickness of the jumper 22 is 1.2 to 3.0 times the thickness of the outer zone heater circuit 16, preferably 1.3 to 2.8 times, more preferably 1.4 to 2.5 times, and even more preferably 1.5 to 2.0 times.

[0014] When the ceramic plate 12 is viewed from above, the area of ​​the jumper 22 is preferably 30 to 80% of the area of ​​the inner zone Z1, more preferably 35 to 80%, and even more preferably 40 to 80%. A jumper 22 with such a large area reduces resistance, thereby reducing the amount of heat generated by the jumper 22 and contributing to improved thermal uniformity. Generally, if a step exists in the electrical connection path surface including the large-area jumper 22, this step itself becomes a source of stress and is likely to cause damage. In this regard, in the present invention, as described above, by making the thickness of the jumper 22 3.0 times or less the thickness of the outer zone heater circuit 16, damage caused by such stress can be effectively suppressed.

[0015] The main portion of the ceramic plate 12 (i.e., the ceramic substrate) other than the embedded members such as the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22 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, and may be an incomplete circle with a portion missing, such as an orientation flat. The size of the ceramic plate 12 may be determined appropriately depending on the diameter of the wafer to be used, and is not particularly limited. However, when the ceramic plate 12 is circular, the diameter is typically 150 to 450 mm, for example, about 300 mm.

[0017] The ceramic plate 12 includes an inner zone Z1 and an outer zone Z2 when viewed from above. 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 is preferably composed of multiple outer subzones Z2a, Z2b, Z2c, and Z2d defined in an arc shape, which facilitates the outer zone heater circuit 16 to be uniformly disposed throughout the entire outer zone Z2. The outer zone Z2 may have two or more non-overlapping annular regions of different sizes arranged concentrically. In this case, the outer zone Z2 has 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 be present outside the second outer zone.

[0018] The inner zone heater circuit 14 is embedded in the inner zone Z1 of the ceramic plate 12 parallel to the first surface 12a. A pair of first power supply terminals 18 for supplying power to the inner zone heater circuit 14 is provided in the center of the inner zone Z1 of the ceramic plate 12. Preferably, the first power supply terminals 18 are connected to both ends of the inner zone heater circuit 14, respectively. There may be two or more pairs of first power supply terminals 18. The first power supply terminals 18 are rod-shaped, and the inner zone heater circuit 14 is connected to a heater power supply (not shown) via the rod-shaped first power supply terminals 18.

[0019] The outer zone heater circuit 16 is embedded in the outer zone Z2 of the ceramic plate 12 at a different depth from the inner zone heater circuit 14 and parallel to the first surface 12a. In FIG. 2 , the inner zone heater circuit 14 is embedded higher than the outer zone heater circuit 16 (i.e., at a depth closer to the first surface 12a), but this is not limiting. Therefore, the inner zone heater circuit 14 may be embedded lower than the outer zone heater circuit 16 (i.e., at a depth closer to the second surface 12b). A pair of second power supply terminals 20 for supplying power to the outer zone heater circuit 16 is provided in the center of the inner zone Z1 of the ceramic plate 12 (but at a different position from the first power supply terminals 18). Because the pair of second power supply terminals 20 is located away from the outer zone heater circuit 16, the pair of second power supply terminals 20 are electrically connected to the outer zone heater circuit 16 via a pair of jumpers 22. Two or more pairs of second power supply terminals 20 may be provided. The second power supply terminal 20 is rod-shaped, and the outer zone heater circuit 16 is connected to a heater power supply (not shown) via a jumper 22 and the rod-shaped second power supply terminal 20 .

[0020] The outer zone heater circuit 16 may be either a series circuit or a parallel circuit. That is, as conceptually shown in FIG. 3 with arrows indicating the current direction, the outer zone heater circuit 16 may be provided so as to start in one direction from the first connection 24 and reach the second connection 26 in a single stroke, forming a series circuit. In this case, it is preferable that the first connection 24 and the second connection 26 are located at both ends of the outer zone heater circuit 16. Alternatively, as conceptually shown in FIG. 4 with arrows indicating the current direction, the outer zone heater circuit 16 may be provided so as to start in two directions from the first connection 24 and reach the second connection 26 in a single stroke, forming a parallel circuit. In this case, it is preferable that the first connection 24 and the second connection 26 are located at the start and end points of the outer zone heater circuit 16. The outer zone heater circuit 16 shown in FIG. 1 corresponds to this parallel circuit. From the viewpoint of uniform heating, both series and parallel circuits are equivalent, but from the viewpoint of preventing an increase in resistance, a parallel circuit is preferred for the outer zone heater circuit 16. A parallel circuit can achieve a resistance value close to that of the coil-shaped resistance heating element used in existing ceramic heaters.

[0021] A pair of jumpers 22 are embedded in the inner zone Z1 of the ceramic plate 12 parallel to the first surface 12a at the same depth as the outer zone heater circuit 16. The pair of jumpers 22 are separated from each other, with one jumper 22 electrically connecting one of the second power supply terminals 20 to the outer zone heater circuit 16 at a first connection portion 24, and the other jumper 22 electrically connecting the other of the second power supply terminals 20 to the outer zone heater circuit 16 at a second connection portion 26 located at a position different from the first connection portion 24. Two or more pairs of jumpers 22 may be provided. Preferably, the first connection portion 24 and the second connection portion 26 are located at both ends of the outer zone heater circuit 16, respectively.

[0022] When the ceramic plate 12 is viewed from above, the pair of jumpers 22 and the pair of second power supply terminals 20 are preferably arranged symmetrically with respect to the perpendicular bisector of the line segment connecting the pair of second power supply terminals 20. With this configuration, the lengths of the power supply paths from the pair of second power supply terminals 20 through the pair of jumpers 22 to the outer zone heater circuit 16 can be made equal, making it easier to achieve good temperature uniformity.

[0023] As described above, each of the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22 is a thin element made of a resistance heating element. The thin element has a form selected from the group consisting of a printed pattern, foil, punched metal, and mesh, and is particularly preferably in the form of a printed pattern. In the case of a thin element in the form of a printed pattern, the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22 can be efficiently manufactured by printing while controlling their thickness. The thickness of the thin element made of a resistance heating element is preferably 100 μm or less, more preferably 10 to 100 μm, and even more preferably 10 to 60 μm. A thickness of 10 μm or more reduces thickness variations when forming the thin element by printing or the like. The resistance heating element constituting the thin element is not particularly limited, and may be a resistance heating element commonly used in ceramic heaters. Examples of suitable resistive heating elements include tungsten, molybdenum, tungsten-molybdenum alloys, tungsten carbide, tungsten carbide-titanium nitride composites, tungsten carbide-aluminum oxide composites, and combinations thereof.

[0024] Preferably, the thickness of the outer zone heater circuit 16 is constant in the in-plane direction, and the thickness of the jumper 22 is constant in the in-plane direction. In this specification, the phrase "constant thickness in the in-plane direction" of the outer zone heater circuit 16 or the jumper 22 means that the thickness of the outer zone heater circuit 16 or the jumper 22 is not intentionally varied in parts. Therefore, a completely constant thickness in the in-plane direction is not required. A substantially constant thickness (e.g., thickness variation of 5% or less) that is deemed not to be intentionally varied can be considered "constant thickness in the in-plane direction." Here, the thickness variation is calculated as the difference between the maximum and minimum thickness values ​​divided by the average thickness and multiplied by 100. By making the thickness of the resistance heating element in each of the outer zone heater circuit 16 and the jumper 22 constant in the in-plane direction, uneven resistance due to thickness variation can be eliminated, achieving good thermal uniformity. As a result, the effects (i.e., damage prevention and good heat uniformity) obtained by making the thickness of the jumper 22 1.2 to 3.0 times the thickness of the outer zone heater circuit 16 can be more effectively realized. In this sense, it is preferable that the thickness of the inner zone heater circuit 14 is also constant in the in-plane direction. In this regard, since each of the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22 is a thin element made of a resistance heating element such as a printed pattern, it can be said that it is suitable to make the thickness of each of them constant in the in-plane direction.

[0025] The outer zone Z2 is preferably composed of a plurality of outer subzones Z2a, Z2b, Z2c, and Z2d defined in an arc. In this case, linear boundary regions B, which are not crossed by the outer zone heater circuit 16, preferably exist between adjacent outer subzones Z2a, Z2b, Z2c, and Z2d in the radial direction of the ceramic plate 12 so as not to completely divide the outer zone Z2. The outer zone heater circuit 16 preferably starts from the first connecting portion 24 in one or two directions, and in each direction, snakes around the outer subzones Z2a, Z2b, Z2c, and Z2d in a single stroke, passing through substantially the entire area of ​​each of the outer subzones Z2a, Z2b, Z2c, and Z2d, alternately moving in the circumferential direction and turning back just before the boundary region B, before reaching the second connecting portion 26. In this way, the outer zone heater circuit 16 can be distributed throughout the outer zone Z2. That is, the outer zone heater circuit 16 can be disposed thoroughly in each of the outer subzones Z2a, Z2b, Z2c, and Z2d, and can also be disposed in portions not blocked by the boundary regions B between the outer subzones Z2a, Z2b, Z2c, and Z2d, so that the outer zone heater circuit 16 can be disposed thoroughly over the entire surface of the ceramic plate 12 in each of the outer subzones Z2a, Z2b, Z2c, and Z2d as continuous wiring extending from the first connecting portion 24 to the second connecting portion 26. In this embodiment, the outer zone heater circuit 16 can be either a series circuit or a parallel circuit as described above, but is preferably a parallel circuit, which allows the electrical resistance of the outer zone heater circuit 16 to be smaller than that of a series circuit.

[0026] In the above embodiment having the outer subzones Z2a, Z2b, Z2c, and Z2d, it is preferable that the circumferential positions of the first connecting portion 24 and the second connecting portion 26 do not coincide with the circumferential position of the boundary region B. This makes it possible to prevent local hot spots from occurring and achieve better thermal uniformity. Specifically, as shown in FIG. 1 , when the ceramic plate 12 is viewed from above, for each of the first connecting portion 24 and the second connecting portion 26, a line L passing through the circumferential center of the boundary region B closest to the connecting portion 24 or 26 and the center of the ceramic plate 12 is １and a straight line L passing through the circumferential center of the connecting portion 24 or 26 and the center of the ceramic plate. ２ The angle θ １ (Hereinafter, the deviation angle θ １ It is preferable that the boundary region B and the connecting portion 24 or 26 are disposed apart from each other so that the angle between the straight line L and the connecting portion 24 or 26 is 20° or more. １ and / or straight line L ２ If there are multiple candidates for the deviation angle θ １ A line L is given １ and the line L ２ The deviation angle θ １ is 20° or more, preferably 30° or more, more preferably 40° or more, even more preferably 45° or more, and particularly preferably 45 to 90°. １ is the angle of deviation of the circumferential center of the connecting portion 24 or 26 from the center line of the boundary region B extending in the radial direction.

[0027] When the first connecting portion 24 and the second connecting portion 26 are regarded as arcs that constitute the outer circumferential circle of the inner zone Z1, the central angle θ ２ is preferably in the range of 6.0 to 10.0°, and more preferably 6.0 to 8.0°. １ In this case, it is possible to ensure that the circumferential positions of the first connecting portion 24 and the second connecting portion 26 do not coincide with the circumferential position of the boundary region B, thereby more effectively achieving better thermal uniformity.

[0028] 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 the ESC electrode are preferably embedded in the ceramic plate 12 at a depth closer to the first surface 12a than the inner zone heater circuit 14 and the jumper 22. The RF electrode enables film formation by a plasma CVD process when high frequency is applied to it. The ESC electrode is an abbreviation for electrostatic chuck (ESC) electrode and is also called an electrostatic electrode. When a voltage is applied to the ESC electrode from an external power source, the ESC electrode chucks a wafer placed on the surface of the ceramic plate 12 by the Johnsen-Rahbek force. The ESC electrode is preferably a circular thin-layer electrode with a diameter slightly smaller than that of the ceramic plate 12. For example, it may be a mesh electrode formed by weaving thin metal wires into a net shape into a sheet. The ESC electrode may also be used as a plasma electrode. That is, by applying high frequency to the ESC electrode, the ESC electrode can also be used as an RF electrode, and film formation by a plasma CVD process can also be performed. An RF terminal 32 or an ESC terminal for feeding power is connected to the RF electrode 30 or the ESC electrode. The RF terminal 32 or the ESC terminal is rod-shaped, and the RF electrode 30 or the ESC electrode is connected to an external power source (not shown) via the rod-shaped RF terminal 32 or the ESC terminal.

[0029] Optionally, a ceramic shaft 28 may be concentrically attached to the second surface 12b of the ceramic plate 12. The ceramic shaft 28 is a cylindrical member with an internal space S 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 to allow terminal rods such as the first power supply terminal 18, the second power supply terminal 20, and the RF terminal 32 to pass therethrough. The ceramic shaft 28 is preferably made of the same ceramic material as the ceramic plate 12. Therefore, the ceramic shaft 28 preferably contains aluminum nitride or aluminum oxide, more preferably aluminum nitride. The upper end surface of the ceramic shaft 28 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 28 is not particularly limited and may be, for example, approximately 44 mm. The inner diameter of the ceramic shaft 28 (the diameter of the internal space S) is also not particularly limited and may be, for example, approximately 39 mm.

[0030] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0031] Example 1 (1) Fabrication of a Multi-Zone Ceramic Heater A multi-zone ceramic heater 10 having the cross-sectional structure shown in Fig. 2 and the planar arrangement shown in Fig. 5, and satisfying the conditions shown in Table 1, was fabricated by a known procedure using the components shown below. <Components and Their Specifications> Ceramic plate 12: a disc-shaped sintered aluminum nitride body (diameter: 340 mm, thickness: 18 mm) (with the inner zone heater circuit 14, outer zone heater circuit 16, jumper 22, and RF electrode 30 embedded inside) Ceramic shaft 28: a cylindrical sintered aluminum nitride body (height: 170 mm, outer diameter: 45 mm, inner diameter: 39 mm) Inner zone Z1: a circular region with a diameter of 240 mm located at the center of the ceramic plate 12 Outer zone Z2: an annular region on the ceramic plate 12 outside the inner zone Z1, having four outer subzones Z2a, Z2b, Z2c, and Z2d separated by linear boundary regions B extending in the radial direction. 5, embedded at a depth of 6 mm from the first surface 12 a of the inner zone Z1. Outer zone heater circuit 16: A printed pattern of a parallel circuit made up of the resistance heating elements shown in FIG. 5, embedded at a depth of 12 mm from the first surface 12 a of the outer zone Z2. The deviation angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B １ : 20° Jumper 22: A symmetrical printed pattern composed of the resistance heating element shown in FIG. 5 , embedded in the inner zone Z1 at a position 12 mm deep from the first surface 12 a (see Table 1 for thickness ratio and area ratio) Resistance heating element: tungsten carbide-titanium nitride composite material (common to the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22) RF electrode 30: A molybdenum electrode layer embedded in the ceramic plate 12 at a position 1 mm deep from the first surface 12 a First power supply terminal 18: Two nickel terminal rods Second power supply terminal 20: Two nickel terminal rods RF terminal 32: One nickel terminal rod First connecting portion 24 and second connecting portion 26: Central angle θ ２ : 6.0° arc-shaped portion (end of jumper 22)

[0032] The ceramic plate 12 with the inner zone heater circuit 14, outer zone heater circuit 16, jumper 22, and RF electrode 30 embedded therein was fabricated by the following procedure. First, two disk-shaped aluminum nitride sintered bodies were prepared. The inner zone heater circuit 14 was printed in a predetermined pattern on one of the aluminum nitride sintered bodies. The outer zone heater circuit 16 and jumper 22 were printed in the pattern shown in FIG. 5 on the other aluminum nitride sintered body. The thicknesses of the jumper 22 and outer zone heater circuit 16 were controlled so that the ratio of the thickness of the jumper 22 to the thickness of the outer zone heater circuit 16 would be 1.2 after firing. Next, the aluminum nitride powder and the RF electrode 30 were press-molded to obtain an aluminum nitride compact with the RF electrode 30 embedded therein. This aluminum nitride compact and the aluminum nitride sintered body with the above-mentioned printed pattern were stacked and press-molded to form the layer structure shown in FIG. 2. The obtained press-molded body (laminate) was fired in a nitrogen atmosphere at 1750 to 1850°C for 3 hours to obtain a ceramic plate 12 having the inner zone heater circuit 14, the outer zone heater circuit 16, the jumper 22, and the RF electrode 30 embedded therein.

[0033] (2) Evaluation The multi-zone ceramic heater 10 was installed in the chamber of a film forming apparatus. The chamber was evacuated and N ２ Introduce N gas into the chamber. ２ The gas pressure was set to 5 Torr. The multi-zone ceramic heater 10 was heated to a set temperature of 650°C by supplying power to the inner zone heater circuit 14 and the outer zone heater circuit 16 via the first power supply terminal 18, the second power supply terminal 20, and the jumper 22. 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 calculated as an index of thermal uniformity. The results are shown in Table 1.

[0034] Example 2 As shown in FIG. 6 and Table 1, the deviation angle θ of the center of each of the first connecting portion 24 and the second connecting portion 26 from the boundary region B １The multi-zone ceramic heater 10 was produced and evaluated in the same manner as in Example 1, except that the angle was set to 0°. The results are shown in Table 1.

[0035] Example 3 As shown in FIG. 7 and Table 1, 1) the deviation angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B １ 1) the angle of the jumper was set to 45°, and 2) the jumper shape was set to a spiral shape occupying 76% of the area of ​​the inner zone Z1. The multi-zone ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0036] Example 4 As shown in FIG. 8 and Table 1, 1) the deviation angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B １ The multi-zone ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1, except that 1) the angle of the jumper 22 to the outer zone heater circuit 16 was 45°, and 2) the ratio of the jumper 22 thickness to the outer zone heater circuit 16 thickness was 2.0. The results are shown in Table 1.

[0037] Example 5 A multi-zone ceramic heater 10 was fabricated and evaluated in the same manner as in Example 3, except that the ratio of the thickness of the jumper 22 to the thickness of the outer zone heater circuit 16 was set to 2.0, as shown in Figure 7 and Table 1. The results are shown in Table 1.

[0038] Example 6 As shown in FIG. 9 and Table 1, 1) the outer zone Z2 is divided into two outer sub-zones Z2a and Z2b by two boundary regions B extending in the radial direction, 2) the outer zone heater circuit 16 is configured as a series circuit, and 3) the offset angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B is １ 3) the ratio of the thickness of the jumper 22 to the thickness of the outer zone heater circuit 16 was 2.0, and the multi-zone ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0039] Example 7 As shown in FIG. 8 and Table 1, 1) the deviation angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B １The multi-zone ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1, except that 1) the angle of the outer zone heater circuit 16 to the jumper 22 was 45°, and 2) the ratio of the jumper 22 thickness to the outer zone heater circuit 16 thickness was 3.0. The results are shown in Table 1. The results are shown in Table 1.

[0040] Example 8 (Comparison) As shown in FIG. 8 and Table 1, 1) the deviation angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B １ An attempt was made to fabricate a multi-zone ceramic heater 10 in the same manner as in Example 1, except that 1) the angle of the jumper 22 to the outer zone heater circuit 16 was 45°, and 2) the ratio of the jumper 22 thickness to the outer zone heater circuit 16 thickness was 4.0. However, as shown in Table 1, damage occurred near the connection (step portion) between the jumper 22 and the outer zone heater circuit 16 during the manufacture of the ceramic heater, impairing the functionality of the multi-zone ceramic heater 10. For this reason, it was not possible to evaluate thermal uniformity. It is believed that this damage occurred because stress generated in the ceramic plate molding process was amplified in the ceramic plate firing process, causing stress to concentrate in the step portion.

[0041] Example 9 (Comparison) As shown in FIGS. 10 and 11 and Table 1, 1) the inner zone heater circuit 14 was formed into a single layer structure at the same depth as the outer zone heater circuit 16 and the jumper 22, 2) the outer zone Z2 was divided into two outer sub-zones Z2a and Z2b by two boundary regions B extending in the radial direction, 3) the outer zone heater circuit 16 was configured as a series circuit, 4) a pair of jumpers 22 was configured as two parallel rows of narrow strips, and 5) the offset angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B was １10 and 11 , the multi-zone ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1, except that 5) the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22 were arranged as a single-layer structure of resistance heating elements, and therefore the inner zone heater circuit 14 could not be disposed in the area where the jumper 22 was present. The results are shown in Table 1.

[0042] Example 10 (Comparative) As shown in FIG. 6 and Table 1, 1) the deviation angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B １ 1) the jumper 22 thickness was set to 0°, and 2) the ratio of the outer zone heater circuit 16 thickness to the jumper 22 thickness was set to 1.0. The multi-zone ceramic heater 10 was fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0043] Example 11 (Comparison) As shown in Table 1, 1) the deviation angle θ of the first connecting portion 24 and the second connecting portion 26 from the boundary region B １ The multi-zone ceramic heater 10 was fabricated and evaluated in the same manner as in Example 3, except that 1) the angle of the jumper 22 to the outer zone heater circuit 16 was set to 20°, and 2) the ratio of the jumper 22 thickness to the outer zone heater circuit 16 thickness was set to 1.0. The results are shown in Table 1.

[0044]

Claims

1. A disc-shaped ceramic plate having a first surface on which a wafer is placed and a second surface opposite to the first surface, the ceramic plate including, when the ceramic plate is viewed in a plane, an inner zone defined as a circular region within a predetermined distance from the center of the ceramic plate, and an outer zone defined as an annular region outside the inner zone; an inner zone heater circuit embedded in the inner zone of the ceramic plate parallel to the first surface; an outer zone heater circuit embedded in the outer zone of the ceramic plate parallel to the first surface at a depth position different from that of the inner zone heater circuit; a pair of first power supply terminals provided in a center of the inner zone of the ceramic plate for supplying power to the inner zone heater circuit; and a pair of second power supply terminals provided in a center of the inner zone of the ceramic plate for supplying power to the outer zone heater circuit. a pair of jumpers separated from each other and embedded in the inner zone of the ceramic plate at the same depth as the outer zone heater circuit and parallel to the first surface, one of the pair of jumpers electrically connecting one of the second power supply terminals to the outer zone heater circuit at a first connection portion and the other of the pair of jumpers electrically connecting the other of the second power supply terminals to the outer zone heater circuit at a second connection portion located at a position different from the first connection portion; wherein each of the inner zone heater circuit, the outer zone heater circuit and the jumpers is a thin element made of a resistive heating element selected from the group consisting of a printed pattern, a foil, a punched metal and a mesh, and a thickness of the jumpers is 1.2 to 3.0 times a thickness of the outer zone heater circuit.

2. The multi-zone ceramic heater according to claim 1, wherein the outer zone is composed of a plurality of outer subzones partitioned into an arc shape, and between adjacent outer subzones in the circumferential direction, a linear boundary region that is not crossed by the outer zone heater circuit exists in the radial direction of the ceramic plate so as not to completely divide the outer zone, and the outer zone heater circuit is arranged to start from the first connection portion in one or two directions, and in each starting direction, in a single stroke, pass through almost the entire area of ​​each of the plurality of outer subzones, meandering while alternately proceeding in the circumferential direction and turning back just before the boundary region, to reach the second connection portion.

3. A multi-zone ceramic heater as described in claim 2, wherein, when the ceramic plate is viewed in a plane, for each of the first connection portion and the second connection portion, the boundary region and the connection portion are arranged at a distance from each other so that an angle formed by a line passing through the circumferential center of the boundary region closest to the connection portion and the center of the ceramic plate and a line passing through the circumferential center of the connection portion and the center of the ceramic plate is 20° or more.

4. A multi-zone ceramic heater as described in claim 2 or 3, wherein when each of the first connection portion and the second connection portion is considered to be an arc constituting the outer peripheral circle of the inner zone, the central angle of each of the arcs is within the range of 6.0 to 10.0°.

5. A multi-zone ceramic heater as described in claim 2 or 3, wherein the outer zone heater circuit is arranged to form a series circuit, starting in one direction from the first connection portion and reaching the second connection portion in a single stroke.

6. A multi-zone ceramic heater as described in claim 2 or 3, wherein the outer zone heater circuits are arranged to form parallel circuits, starting in two directions from the first connection portion and reaching the second connection portion in a single stroke in each starting direction.

7. A multi-zone ceramic heater as described in any one of claims 1 to 3, wherein, when the ceramic plate is viewed in a plane, the pair of jumpers and the pair of second power supply terminals are arranged symmetrically with respect to a perpendicular bisector of a line segment connecting the pair of second power supply terminals.

8. The multi-zone ceramic heater of any one of claims 1 to 3, wherein each of the inner zone heater circuits, the outer zone heater circuits, and the jumpers are in the form of a printed pattern.

9. The multi-zone ceramic heater of any one of claims 1 to 3, wherein the outer zone heater circuits have a constant thickness in the in-plane direction and the jumpers have a constant thickness in the in-plane direction.

10. A multi-zone ceramic heater as described in any one of claims 1 to 3, further comprising an RF electrode and / or an ESC electrode embedded in the ceramic plate at a depth closer to the first surface than the inner zone heater circuit and the jumper.

11. The multi-zone ceramic heater of any one of claims 1 to 3, wherein the ceramic plates comprise aluminum nitride or aluminum oxide.

12. A multi-zone ceramic heater as claimed in any one of claims 1 to 3, further comprising a cylindrical ceramic shaft concentrically attached to the second surface of the ceramic plate and having an internal space.

13. The multi-zone ceramic heater of any one of claims 1 to 3, wherein the resistive heating element comprises at least one selected from the group consisting of tungsten, molybdenum, a tungsten-molybdenum alloy, tungsten carbide, a tungsten carbide-titanium nitride composite, and a tungsten carbide-aluminum oxide composite.

14. The multi-zone ceramic heater of any one of claims 1 to 3, wherein the jumper has a thickness that is 1.8 to 3.0 times the thickness of the outer zone heater circuit.

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