Ceramic heater

Abstract

Provided is a multi-zone ceramic heater with jumpers, resistant to breakage during manufacture or use and capable of achieving not only desired heat uniformity but also a desired temperature distribution profile when changing the inner zone / outer zone power ratio. This ceramic heater comprises: a ceramic plate including an inner zone defined as a circular area within a prescribed distance from the center and an outer zone defined as an annular area outside the inner zone; an inner zone heater circuit embedded in the inner zone of the ceramic plate; an outer zone heater circuit embedded in the outer zone of the ceramic plate; and a pair of jumpers embedded in the inner zone of the ceramic plate so as not to contact the inner zone heater circuit, and electrically connected to the outer zone heater circuit. The resistance per jumper as a percentage of the resistance of the outer zone heater circuit is between 0.5% and 1.9%.

Description

Ceramic heater

[0001] The present disclosure relates to ceramic heaters.

[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] The miniaturization and high layer density for higher integration of semiconductors are progressing at an accelerating pace, and the semiconductor manufacturing process is becoming higher in temperature, longer in duration, and more powerful in plasma. As a result, the demands for thermal uniformity of ceramic heaters are becoming increasingly strict.

[0004] On the other hand, in multi-zone ceramic heaters with two or more zones, each having an inner zone heater circuit and an outer zone heater circuit, a jumper is used to ensure electrical connection from a power supply terminal near the center of the ceramic plate to the outer zone heater circuit. However, due to its structure, the jumper is prone to becoming a singular point in the temperature distribution, which can impair thermal uniformity. For this reason, various measures have been proposed regarding the jumper to improve thermal uniformity. Examples of such measures include (1) increasing the cross-sectional area of ​​the jumper relative to the cross-sectional area of ​​the heater (see Patent Document 1, described below), (2) shortening the jumper length by making it as linear as possible (see Patent Document 2, described below), and (3) shortening the jumper length by reducing the area of ​​the inner zone and increasing the area of ​​the outer zone.

[0005] Patent Document 1 (JP 2018-537802 A) discloses a substrate heating device including a body portion that supports a substrate, a first heating element (inner zone heater circuit) located in an internal region of the body portion, a second heating element (outer zone heater circuit) located in an external region that surrounds the internal region, and a third heating element (jumper) that transmits current to the second heating element across the internal region of the body portion, and the diameter of the wire that constitutes the third heating element (jumper) is set to be larger than the diameter of the wire that constitutes the second heating element (outer zone heater circuit).

[0006] Patent Document 2 (Japanese Patent No. 4640842) discloses a heating device including a heater and a hollow support member fixed to the back surface of the heater. This heater comprises a plate-shaped substrate made of an insulating material, in which a first heating element, a second heating element, a first conductive connection, a first terminal, a second conductive connection, and a second terminal are embedded. The first heating element is provided on the periphery of the heater to form an outer zone heater circuit, while the second heating element, together with the first terminal, the second terminal, and the second conductive connection, is provided in the center of the heater to form an inner zone heater circuit. The first heating element, which corresponds to the outer zone heater circuit, has multiple ends connected to first conductive connections, and the first terminals are connected to the first conductive connections. Therefore, the first conductive connections correspond to jumpers. The drawings in this document also disclose a circuit pattern in which the length of the first conductive connections (jumpers) is shortened by being configured in a linear manner.

[0007] Special table publication No. 2018-537802 Publication Patent No. 4640842

[0008] However, conventional multi-zone ceramic heaters equipped with jumpers can be damaged during manufacturing or use, and even if this does not happen, they have problems such as not being able to achieve the desired thermal uniformity or making it difficult to achieve the desired temperature distribution profile when changing the power ratio of the inner zone / outer zone.

[0009] The inventors have now discovered that by setting the percentage of the resistance per jumper relative to the resistance of the outer zone heater circuit within the range of 0.5 to 1.9%, breakage during manufacturing or use is less likely to occur, and desirable thermal uniformity as well as desirable temperature distribution profiles can be achieved when changing the power ratio of the inner zone to the outer zone.

[0010] Therefore, an object of the present invention is to provide a multi-zone ceramic heater with a jumper that is less likely to be damaged during manufacturing or use, and that can achieve not only desirable thermal uniformity but also desirable temperature distribution profiles when the power ratio of the inner zone / outer zone is changed.

[0011] The present disclosure provides the following aspects: [Aspect 1] A ceramic heater comprising: a disc-shaped ceramic plate having a first surface on which a wafer is placed and a second surface opposite 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, an outer zone heater circuit embedded in the outer zone of the ceramic plate, and a pair of jumpers embedded in the inner zone of the ceramic plate so as not to come into contact with the inner zone heater circuit and electrically connected to the outer zone heater circuit, wherein the percentage of the resistance of each jumper with respect to the resistance of the outer zone heater circuit is 0.5 to 1.9%. [Aspect 2] The ceramic heater according to Aspect 1, wherein the inner zone heater circuit and the outer zone heater circuit comprise a resistance heating element in at least one form selected from the group consisting of a coil, a linear zigzag structure, a printed pattern, a ribbon, and a mesh. [Aspect 3] The ceramic heater according to Aspect 2, wherein the outer zone heater circuit comprises a resistance heating element in the form of a coil having a winding diameter of 2.5 to 5.0 mm and a wire diameter of 0.3 to 0.7 mm. [Aspect 4] The ceramic heater according to Aspect 2 or 3, wherein the outer zone heater circuit comprises a resistance heating element in the form of a linear zigzag structure having a maximum deflection amplitude of 5 to 15 mm and a wire diameter of 0.3 to 0.7 mm. [Aspect 5] The ceramic heater according to any one of Aspects 1 to 4, wherein the jumper comprises a resistance heating element in at least one form selected from the group consisting of a wire, a printed pattern, and a ribbon. [Aspect 6] The ceramic heater according to any one of Aspects 1 to 5, wherein the outer zone is divided into a plurality of outer subzones, and the sum of the resistance values ​​of the resistive heating elements embedded in the plurality of outer subzones is regarded as the resistance value of the outer zone heater circuit. [Aspect 7] The ceramic heater according to any one of Aspects 1 to 6, wherein the ceramic plate comprises aluminum nitride or aluminum oxide.[Aspect 8] The ceramic heater according to any one of Aspects 1 to 7, further comprising: 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 via the jumper. [Aspect 9] The ceramic heater according to any one of Aspects 1 to 8, further comprising an internal electrode, which is an RF electrode and / or an ESC electrode, within the ceramic plate. [Aspect 10] The ceramic heater according to any one of Aspects 1 to 9, further comprising a cylindrical ceramic shaft concentrically attached to the second surface of the ceramic plate and having an internal space.

[0012] 1 is a perspective cross-sectional view schematically showing an example of a ceramic heater according to the present invention. For convenience of explanation, the jumper 22 is drawn at a position slightly lower than its actual position in order to clearly show the configurations of the inner zone control heater circuit 14a and the jumper 22, which are actually located at the same height.

[0034] FIG. 1 is a perspective cross-sectional view schematically showing another example of a ceramic heater according to the present invention.

[0035] FIG. 3 is a schematic top view of the ceramic heater shown in FIG.

[0036] FIG. 4 is a plan view schematically showing the circuit patterns of the inner zone heater circuit, outer zone heater circuit, and jumper employed in Examples 1 to 9 and 12. Lines corresponding to the circuit patterns in this figure represent the center lines of the inner zone heater circuit, outer zone heater circuit, and jumper.

[0037] FIG. 5A is a plan view schematically showing the circuit pattern of the inner zone heater circuit shown in FIG. 5A.

[0038] FIG. 5B is a plan view schematically showing the circuit patterns of the outer zone heater circuit and jumper shown in FIG. 5A. 6A is a plan view schematically showing the circuit patterns of the inner zone heater circuit, the outer zone heater circuit, and the jumpers employed in Examples 10 and 11. The lines corresponding to the circuit patterns in this figure represent the center lines of the inner zone heater circuit and the outer zone heater circuit. FIG. 6B is a plan view schematically showing the circuit pattern of the inner zone heater circuit shown in FIG. 6A. FIG. 6C is a plan view schematically showing the circuit patterns of the outer zone heater circuit and the jumpers shown in FIG. 6A. FIG. 6D is a graph showing the relationship between the percentage of the resistance per jumper relative to the resistance of the outer zone heater circuit and the maximum in-plane temperature difference (thermal uniformity), measured in various examples including Examples 1 to 6. FIG. 6E is a temperature profile measured in Examples 1 to 6 when the outer / inner power ratio is changed to 1.4.

[0013] The ceramic heater according to the present invention is a ceramic platform for supporting a wafer in a semiconductor manufacturing device. Typically, the ceramic heater according to the present invention can be a ceramic heater for a semiconductor film deposition device. Typical examples of film deposition devices include CVD (chemical vapor deposition) devices (e.g., thermal CVD devices, plasma CVD devices, photo CVD devices, and MOCVD devices) and PVD (physical vapor deposition) devices.

[0014] 1 and 2 show one embodiment of a ceramic heater. The 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, and a pair of jumpers 22. The ceramic plate 12 is circular 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 from above, 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. The inner zone heater circuit 14 is embedded in the inner zone Z1 of the ceramic plate 12, while the outer zone heater circuit 16 is embedded in the outer zone Z2 of the ceramic plate. The pair of jumpers 22 are embedded in the inner zone Z1 of the ceramic plate 12 so as not to come into contact with the inner zone heater circuit 14, and are electrically connected to the outer zone heater circuit 16. The percentage of the resistance of each jumper 22 relative to the resistance of the outer zone heater circuit 16 is 0.5 to 1.9%. By setting the percentage of the resistance of each jumper 22 relative to the resistance of the outer zone heater circuit 16 within this range of 0.5 to 1.9%, breakage during manufacturing or use is less likely to occur, and desirable temperature uniformity as well as a desirable temperature distribution profile when the power ratio between the inner zone and the outer zone is changed can be achieved.

[0015] As mentioned above, conventional multi-zone ceramic heaters equipped with jumpers can be damaged during manufacturing or use. Even if they are not, they can fail to achieve the desired thermal uniformity or make it difficult to achieve a desired temperature distribution profile when changing the power ratio between the inner and outer zones. For example, when using a three-dimensional coil-type resistance heating element, increasing the diameter of the jumper as proposed in Patent Document 1 increases the thermal stress generated during manufacturing or use, increasing the risk of damage. Similarly, when using a resistance heating element with a linear zigzag structure, increasing the diameter of the jumper also increases the risk of damage, as with a three-dimensional coil. Furthermore, if the size of the outer zone is made larger relative to the inner zone, changing the power ratio between the inner and outer zones of a two-zone heater due to changes in process conditions, etc., can make it difficult to achieve the user's desired temperature distribution profile (e.g., selectively or preferentially increasing the temperature of the outer periphery of the ceramic heater). The present invention successfully solves these problems.

[0016] In particular, while increasing the diameter of the jumper in the prior art could reduce the resistance of the jumper relative to the resistance of the outer zone heater circuit, it increased the risk of breakage due to thermal stress during manufacturing or use, making it difficult to actually use. Therefore, in order to significantly increase the heating element density in the outer zone heater circuit, attempts have been made to (i) increase the coil winding diameter, reduce the coil wire diameter, and / or maximize the number of coils (reduce the coil pitch) for three-dimensional coil-type resistance heating elements, (ii) increase the maximum amplitude of the linear zigzag structure, reduce the wire diameter of the linear zigzag structure, and / or maximize the number of zigzags (reduce the pitch) for linear zigzag resistance heating elements, and (iii) reduce the printing width, thin the printing thickness, and / or zigzag the printing pattern for printed pattern resistance heating elements, thereby significantly reducing the ratio of the resistance of the jumper relative to the resistance of the outer zone heater circuit. This significantly reduces the relative heat generation of the jumper, and as a result, the thermal uniformity (temperature uniformity) of the ceramic heater 10 can be improved.

[0017] Specifically, the percentage of the resistance of each jumper 22 relative to the resistance of the outer zone heater circuit 16 is 0.5 to 1.9%, preferably 0.5 to 1.1%, and more preferably 0.5 to 0.9%. Within these ranges, breakage during manufacturing or use is less likely to occur, and desirable thermal uniformity and a desirable temperature distribution profile when changing the inner / outer zone power ratio can be more effectively achieved.

[0018] The ceramic plate 12 preferably contains aluminum nitride or aluminum oxide, more preferably aluminum nitride, in its main portion (i.e., the ceramic substrate) other than the embedded members such as the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22, from the viewpoints of excellent thermal conductivity, high electrical insulation, and thermal expansion characteristics similar to those of silicon.

[0019] The ceramic plate 12 is disk-shaped. However, the planar shape of the disk-shaped ceramic plate 12 does not need to be a perfect circle; for example, it may be an incomplete circle with a portion missing, such as an orientation flat. The size of the ceramic plate 12 is not particularly limited and can be determined appropriately depending on the diameter of the wafer to be used. However, when the ceramic plate 12 is circular, the diameter is typically 150 to 450 mm, and particularly for 300 mm silicon wafers, the diameter is typically 320 to 380 mm. The thickness of the ceramic plate 12 is typically 10 to 25 mm.

[0020] 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 may be divided into multiple outer subzones (e.g., two to four). In this case, the resistance value of the outer zone heater circuit 16 is considered to be the sum of the resistance values ​​of the resistance heating elements embedded in the multiple outer subzones. For example, the outer zone Z2 may be composed of multiple outer subzones divided into arcs (e.g., two to four). (For example, in FIG. 4, the outer zone Z2 is divided into two). Alternatively, the outer zone Z2 may have two or more concentric annular regions of different sizes that do not overlap each other. 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 desired, there may be a third or more outer zones outside the second outer zone.

[0021] The inner zone heater circuit 14 and the outer zone heater circuit 16 preferably include a resistance heating element having at least one form selected from the group consisting of a coil, a linear zigzag structure, a printed pattern, a ribbon, and a mesh. A coil has a configuration in which a resistance heating wire is wound three-dimensionally, while a linear zigzag structure has a configuration in which a resistance heating wire is alternately folded two-dimensionally within a plane. The printed pattern is not particularly limited, but a typical pattern is a strip-shaped line of the resistance heating element layer that alternates between straight and bent (e.g., zigzag). It is preferable to use resistance heating elements of the same form for the inner zone heater circuit 14 and the outer zone heater circuit 16 because of ease of fabrication, but resistance heating elements of different forms may also be used. Each of the inner zone heater circuit 14 and the outer zone heater circuit 16 is preferably arranged in a single-stroke form when viewed in a plan view. The single-stroke form may be any of various known forms, such as an alternating forward and backward trajectory or a spiral.

[0022] 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 may be 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.

[0023] In a preferred embodiment of the present invention, the inner zone heater circuit 14 includes a resistance heating element in the form of a coil. In this case, 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. In another preferred embodiment of the present invention, the inner zone heater circuit 14 includes a resistance heating element in the form of a linear zigzag structure. In this case, the maximum amplitude of the linear zigzag structure is preferably 5 to 15 mm, more preferably 5 to 10 mm, and even more preferably 6 to 8 mm. The maximum amplitude of the linear zigzag structure is defined as the distance between the line connecting the vertices on one side of the linear zigzag structure and the line connecting the vertices on the opposite side. The wire diameter of the linear zigzag structure 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. In yet another preferred embodiment of the present invention, the inner zone heater circuit 14 includes a resistance heating element in the form of a printed pattern. In this case, the printing thickness of the printed pattern (thickness of the resistance heating element layer) is preferably 0.01 to 0.06 mm, more preferably 0.01 to 0.04 mm, and even more preferably 0.015 to 0.03 mm.

[0024] The outer zone heater circuit 16 is embedded in the outer zone Z2 of the ceramic plate 12 at the same or a different depth as the inner zone heater circuit 14 and parallel to the first surface 12a. In a preferred embodiment of the present invention, as shown in FIGS. 1 and 2, the outer zone heater circuit 16 may be embedded in the outer zone Z2 of the ceramic plate 12 at the same depth as the inner zone heater circuit 14 and parallel to the first surface 12a. In another preferred embodiment of the present invention, as shown in FIGS. 3 and 4, the outer zone heater circuit 16 may be embedded in the outer zone Z2 of the ceramic plate 12 at a different depth than the inner zone heater circuit 14 and parallel to the first surface 12a. In FIG. 3, 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 also be embedded lower than the outer zone heater circuit 16 (i.e., at a depth closer to the second surface 12b). In either embodiment, a pair of second power supply terminals 20 for supplying power to the outer zone heater circuit 16 via jumpers 22 is provided in the center of the inner zone Z1 of the ceramic plate 12 (but at a position different from the first power supply terminals 18). That is, the pair of second power supply terminals 20 is located at a position away from the outer zone heater circuit 16, and therefore the pair of second power supply terminals 20 is electrically connected to the outer zone heater circuit 16 via the pair of jumpers 22. Two or more pairs of second power supply terminals 20 may be provided. The second power supply terminals 20 are rod-shaped, and the outer zone heater circuit 16 is connected to a heater power source (not shown) via the jumpers 22 and the rod-shaped second power supply terminals 20.

[0025] In a preferred embodiment of the present invention, the outer zone heater circuit 16 includes a resistance heating element in the form of a coil. In this case, 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. In another preferred embodiment of the present invention, the outer zone heater circuit 16 includes a resistance heating element in the form of a linear zigzag structure. In this case, the maximum amplitude of the linear zigzag structure is preferably 5 to 15 mm, more preferably 5 to 10 mm, and even more preferably 6 to 8 mm. The wire diameter of the linear zigzag structure 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. In yet another preferred embodiment of the present invention, the outer zone heater circuit 16 includes a resistance heating element in the form of a printed pattern. In this case, the printing thickness of the print pattern (thickness of the resistance heating element layer) is preferably 0.01 to 0.06 mm, more preferably 0.01 to 0.04 mm, and even more preferably 0.015 to 0.03 mm. In either embodiment, dimensions within the above ranges facilitate significantly increasing the heating element density in the outer zone heater circuit and effectively reduce the ratio of the resistance of the jumper 22 to the resistance of the outer zone heater circuit 16. That is, it becomes easier to adjust the percentage of the resistance of the jumper 22 (per jumper 22) to the resistance of the outer zone heater circuit 16 to within a range of 0.5 to 1.9%, which results in less damage during manufacturing or use and more effectively achieves not only desirable thermal uniformity but also a desirable temperature distribution profile when changing the power ratio between the inner zone and the outer zone.

[0026] The outer zone heater circuit 16 may be either a series circuit or a parallel circuit. That is, the outer zone heater circuit 16 may be provided so as to start in one direction from one of the pair of jumpers 22 and reach the other of the pair of jumpers 22 in a single stroke, so as to form a series circuit (see, for example, FIGS. 5A and 5C described below). Alternatively, the outer zone heater circuit 16 may be provided so as to start in two directions from one of the pair of jumpers 22 and reach the other of the pair of jumpers 22 in a single stroke, so as to form a parallel circuit (see, for example, FIGS. 6A and 6C described below). The outer zone heater circuit 16 shown in FIG. 1 corresponds to this series circuit, while the outer zone heater circuit 16 shown in FIG. 3 corresponds to this parallel circuit.

[0027] A pair of jumpers 22 are embedded in the inner zone Z1 of the ceramic plate 12 so as not to come into contact with the inner zone heater circuit 14, and are electrically connected to the outer zone heater circuit 16. They may be embedded parallel to the first surface 12a at the same or a different 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 one end of the outer zone heater circuit 16, and the other jumper 22 electrically connecting the other of the second power supply terminals 20 to the other end of the outer zone heater circuit 16. Two or more pairs of jumpers 22 may be present.

[0028] The jumper 22 preferably includes a resistance heating element in at least one form selected from the group consisting of a line, a printed pattern, and a ribbon. The specific form of the line is not particularly limited, but typical examples include a straight line, a curve (e.g., an arc), and a combination of a straight line and a curve (e.g., a straight line bent with a partial curvature). In a preferred embodiment of the present invention, the jumper 22 is a linear resistance heating element (i.e., a resistance heating element wire). In this case, the wire diameter of the resistance heating element wire is preferably 0.3 to 0.7 mm, more preferably 0.4 to 0.7 mm, and even more preferably 0.5 to 0.7 mm. In another preferred embodiment of the present invention, the jumper 22 is a printed pattern. In this case, the printing thickness of the printed pattern (thickness of the resistance heating element layer) is preferably 0.01 to 0.06 mm, more preferably 0.02 to 0.05 mm, and even more preferably 0.025 to 0.04 mm.

[0029] 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.

[0030] 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.

[0031] 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 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 28 is not particularly limited, but is preferably 40 to 60 mm. The inner diameter of the ceramic shaft 28 (the diameter of the internal space S) is also not particularly limited, but is preferably 33 to 55 mm.

[0032] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0033] Examples 1 to 9 and 12 (1) Fabrication of Ceramic Heater Using the components shown below, a ceramic heater 10 having the structure shown in FIGS. 1 and 2 was fabricated by a known procedure except for the firing conditions.<Constituent members and their specifications> Ceramic plate 12: a disk-shaped sintered aluminum nitride body (diameter: 330 mm, thickness: 20 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: 172 mm, outer diameter: 47 mm, inner diameter: 36 mm) Inner zone Z1: a circular region with a diameter of 216 mm located in the center of the ceramic plate 12 Outer zone Z2: an annular region on the ceramic plate 12 outside the inner zone Z1 Inner zone heater circuit 14: a three-dimensional coil-shaped resistance heating element (Examples 1 to 5, 8, and 9, material: molybdenum, winding diameter and wire diameter: as shown in Table 1) embedded in the inner zone Z1 at a depth of 6.5 mm from the first surface 12a according to the circuit pattern shown in FIGS. 5A and 5B, or a resistance heating element with a linear zigzag structure (Examples 6 and 7, material: molybdenum, wire diameter and maximum fluctuation width of heating element (maximum fluctuation width of zigzag structure): as shown in Table 1) Outer zone heater circuit 16: a three-dimensional coil-shaped resistance heating element (Examples 1 to 5, 8, and 9, material: molybdenum, winding diameter and wire diameter: as shown in Table 1) or a linear zigzag resistance heating element (Examples 6 and 7, material: molybdenum, wire diameter and maximum fluctuation width of heating element (maximum fluctuation width of zigzag structure): as shown in Table 1) embedded at a depth of 6.5 mm from the first surface 12a of the outer zone Z2 according to the circuit pattern shown in FIGS. 5A and 5C. Jumper 22: a pair of substantially linear, symmetrical resistance heating wires (material: molybdenum, wire diameter: 0.7 mm) embedded at a depth of 6.5 mm from the first surface 12a of the inner zone Z1 according to the circuit pattern shown in FIGS. 5A and 5C (although the jumper 22 is schematically drawn as a straight line in FIGS. 5A and 5C, in reality it is a substantially linear line with a curved portion as shown in FIG. 2). - RF electrode 30: An electrode layer made of molybdenum embedded at a depth of 1.0 mm from the first surface 12a of the ceramic plate 12. - First power supply terminal 18: Two terminal rods made of nickel. - Second power supply terminal 20: Two terminal rods made of nickel. - RF terminal 32: One terminal rod made of nickel.

[0034] The ceramic plate 12 having 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, 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 14, the outer zone heater circuit 16, and the jumper 22 were arranged according to the circuit patterns shown in Figures 5A to 5C and press-molded to obtain a second aluminum nitride compact having the inner zone heater circuit 14, the outer zone heater circuit 16, and the jumper 22 embedded therein. 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 having the RF electrode 30 further embedded therein. In this way, a press-molded body was obtained consisting of an aluminum nitride powder compact in which the inner zone heater circuit 14, outer zone heater circuit 16, jumper 22, and RF electrode 30 were embedded, as shown in Figure 2. The obtained press-molded body (laminate) was fired in a nitrogen atmosphere under the following conditions: Maximum temperature: 1810°C, Holding time at maximum temperature: 5 hours, Heating rate: Vary within the range of 10 to 120°C / min (temperature range including each heating rate in multiple heating steps), and Firing pressure: 90 kg / cm ２ By firing at this temperature, a ceramic plate 12 was obtained in which the inner zone heater circuit 14, the outer zone heater circuit 16, the jumper 22, and the RF electrode 30 were embedded.

[0035] (2) Evaluation Various evaluations were carried out on the obtained ceramic heater.

[0036] <Jumper / Outer Heater Resistance Ratio> The resistance of the outer zone heater circuit 16 and the resistance of each jumper 22 were measured at room temperature. The resistance of the outer zone heater circuit 16 was measured by connecting a four-terminal tester to both ends of the outer zone heater circuit 16. The resistance of each jumper 22 was measured by connecting a four-terminal tester to both ends of each pair (i.e., two) of jumpers 22, and the average of the two obtained resistance values ​​was calculated. The resistance of each jumper 22 was divided by the resistance of the outer zone heater circuit 16 and multiplied by 100 to calculate the percentage of the resistance per jumper to the resistance of the outer zone heater circuit (hereinafter referred to as the jumper / outer heater resistance ratio). The results are shown in Table 1.

[0037] <Heat Uniformity> The ceramic heater 10 was installed in the chamber of a film forming apparatus. The chamber was evacuated and N ２ Introduce N gas into the chamber. ２ The gas pressure was 5 Torr. The ceramic heater 10 was heated to a set temperature of 550°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. The ratio of the power supplied to the outer zone heater circuit 16 to the power supplied to the inner zone heater circuit 14 was finely adjusted to achieve the most uniform temperature distribution, based on a standard of 1:1. 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 in-plane temperature difference) was calculated as an index of thermal uniformity. The results are shown in Table 1. Figure 7 also shows the relationship between the maximum in-plane temperature difference and the jumper / outer heater resistance ratio. However, for Example 12, the ceramic heater 10 broke during the evaluation, so the thermal uniformity and the temperature profile described below could not be evaluated.

[0038] <Temperature Profile with Change in Outer / Inner Power Ratio> The ceramic heater 10 was heated to a set temperature of 550°C (the temperature measured by the thermocouple 36 in the inner zone Z1) in the same manner as in the evaluation of thermal uniformity described above, except that the outer zone heater circuit 16 was supplied with 1.3 to 1.5 times the power of the inner zone heater circuit 14 (i.e., the outer / inner power ratio was changed) to promote preferential temperature increase in the outer zone Z2. At this set temperature, the temperature distribution on the first surface 12a of the ceramic plate 12 was measured using an infrared camera. In the obtained temperature distribution map, an arbitrary line passing through the center of the ceramic plate 12 was defined as the X-axis, and the center of the ceramic plate 12 was set as the reference point (X = 0 mm) of the X-coordinate axis. Temperatures at various positions (radial positions) on the X-axis coordinate of the ceramic plate 12, including the inner zone Z1 and the outer zone Z2, were read from the temperature distribution map, and the central temperature at X = 0 mm was subtracted from the temperatures read at each position to determine the temperature difference, which represents the temperature increase. The obtained temperature differences at each position were plotted in relation to the position on the X-axis coordinate to set an approximate curve, thereby obtaining a temperature profile. The obtained temperature profiles were evaluated according to the following criteria. The results are shown in Table 1 and FIG. 8. [Evaluation Criteria] Good: The temperature profile is roughly symmetrical, and the temperature rises at a higher temperature gradient (the slope of the tangent to the approximate curve of the temperature profile) as it approaches the periphery, while suppressing an excessive temperature rise in the middle part of the ceramic plate 12 (the region where the absolute value of X is approximately 60 to 130 mm). Poor: The temperature profile does not meet the above criteria for "good" (i.e., the temperature profile is asymmetrical and / or an excessive temperature rise is observed in the middle part (e.g., a temperature gradient higher than near the periphery)).

[0039] Examples 10 and 11 (1) Fabrication of Ceramic Heater Using the components shown below, a ceramic heater 10 having the structure shown in FIGS. 3 and 4 was fabricated by a known procedure except for the firing conditions. <Constituent members and their specifications> Ceramic plate 12: disc-shaped sintered aluminum nitride body (diameter: 330 mm, thickness: 20 mm) (with inner zone heater circuit 14, outer zone heater circuit 16, jumper 22, and RF electrode 30 embedded inside) Ceramic shaft 28: cylindrical sintered aluminum nitride body (height: 172 mm, outer diameter: 60 mm, inner diameter: 51 mm) Inner zone Z1: circular region with a diameter of 216 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 Inner zone heater circuit 14: printed pattern (zigzag, printing thickness: as shown in Table 1) composed of resistance heating elements embedded according to the circuit pattern shown in Figures 6A and 6B at a depth of 6.5 mm from the first surface 12a of the inner zone Z1 Outer zone heater circuit 16: a parallel circuit printed pattern (zigzag, printing thickness: as shown in Table 1) made up of resistance heating elements embedded in the outer zone Z2 at a depth of 11 mm from the first surface 12 a according to the circuit pattern shown in FIGS. 6A and 6C Jumper 22: a symmetrical printed pattern (printing thickness: 0.03 mm) made up of resistance heating elements embedded in the inner zone Z1 at a depth of 11 mm from the first surface 12 a in the region shown in FIGS. 6A and 6C 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 depth of 1.0 mm 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

[0040] 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 on one of the aluminum nitride sintered bodies according to the circuit pattern shown in FIGS. 6A and 6B . The outer zone heater circuit 16 and jumper 22 were printed on the other aluminum nitride sintered body according to the circuit pattern shown in FIGS. 6A and 6C . 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. 4 . The obtained press-molded body (laminate) was fired under a nitrogen atmosphere under the following conditions: Maximum temperature: 1810°C; Holding time at maximum temperature: 5 hours; Heating rate: Vary within the range of 10 to 120°C / min (temperature range including the individual heating rates in multiple heating steps); Firing pressure: 90 kg / cm ２ By firing at this temperature, a ceramic plate 12 was obtained in which the inner zone heater circuit 14, the outer zone heater circuit 16, the jumper 22, and the RF electrode 30 were embedded.

[0041] (2) Evaluation The ceramic heater obtained was evaluated in the same manner as in Example 1.

[0042]

[0043] Separately from the above-described example, an attempt was made to fabricate ceramic heaters using molybdenum coils with a wire diameter of 0.2 mm for the inner zone heater circuit 14 and the outer zone heater circuit 16, but the coils broke during fabrication and were significantly deformed, making it impossible to adopt the coils.

[0044] The results shown in Table 1 and Figures 7 and 8 reveal the following. Examples 1 and 2 (comparison) are comparative examples in which the jumper / outside heater resistance ratio exceeded 2%. The maximum in-plane temperature difference at the evaluation temperature of 550°C exceeded 5°C, resulting in poor thermal uniformity. Furthermore, when the outer / inside power ratio was changed to 1.4, an undesirable temperature profile with poor bilateral symmetry was obtained, as shown in Figure 3. Example 3 (comparison) is a comparative example in which the jumper / outside heater resistance ratio was low at 0.3%. Although it exhibited good thermal uniformity (maximum in-plane temperature difference of 5.0°C or less), when the outer / inside power ratio was changed to 1.4, an undesirable temperature profile was obtained in which an excessive temperature rise (a temperature gradient higher than that near the periphery) was observed in the middle portion (the region where the absolute value of X is around 60 to 130 mm) rather than the periphery, as shown in Figure 3. Examples 4 to 11 are examples in which the jumper / outer heater resistance ratio was in the range of 0.5 to 1.9%, and achieved good thermal uniformity (maximum in-plane temperature difference of 5.0°C or less) and a desirable temperature profile when the power ratio was changed. That is, as shown in Figure 8, the temperature profile when the power ratio was changed was symmetrical and suppressed excessive temperature rise in the middle part of the ceramic plate 12 (the region where the absolute value of X is around 60 to 130 mm), while the temperature rose at a higher temperature gradient toward the periphery, which was a desirable profile. In the ceramic heater industry, there is a high demand for ceramic heaters that not only have good thermal uniformity but also exhibit a temperature profile in which the temperature rises preferentially in the periphery, and it can be said that the ceramic heaters of Examples 4 to 11 fully meet such needs.

Claims

1. A disc-shaped ceramic plate having a first surface for mounting a wafer and a second surface facing the first surface, the ceramic plate including an inner zone defined as a circular region within a predetermined distance from the center of the ceramic plate in a plan view, 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; an outer zone heater circuit embedded in the outer zone of the ceramic plate; and a pair of jumpers embedded in the inner zone of the ceramic plate so as not to contact the inner zone heater circuit and electrically connected to the outer zone heater circuit, the ceramic heater having a percentage of the resistance value of each jumper with respect to the resistance value of the outer zone heater circuit being 0.5 to 1.9%.

2. The ceramic heater according to claim 1, wherein the inner zone heater circuit and the outer zone heater circuit include a resistance heating element in at least one form selected from the group consisting of a coil, a linear zigzag structure, a printed pattern, a ribbon, and a mesh.

3. The ceramic heater according to claim 2, wherein the outer zone heater circuit includes a resistance heating element in a coil form having a winding diameter of 2.5 to 5.0 mm and a wire diameter of 0.3 to 0.7 mm.

4. The ceramic heater according to claim 2, wherein the outer zone heater circuit includes a resistance heating element in a form of a linear zigzag structure having a maximum deflection width of 5 to 15 mm and a wire diameter of 0.3 to 0.7 mm.

5. The ceramic heater according to any one of claims 1 to 4, wherein the jumper includes a resistance heating element in at least one form selected from the group consisting of a wire, a printed pattern, and a ribbon.

6. The ceramic heater according to any one of claims 1 to 4, wherein the outer zone is divided into a plurality of outer sub-zones, and the sum of the resistance values of the resistance heating elements embedded in the plurality of outer sub-zones is regarded as the resistance value of the outer zone heater circuit.

7. The ceramic heater according to any one of claims 1 to 4, wherein the ceramic plate includes aluminum nitride or aluminum oxide.

8. A pair of first power supply terminals provided at the 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 at the center of the inner zone of the ceramic plate for supplying power to the outer zone heater circuit via the jumper. The ceramic heater according to any one of claims 1 to 4, further comprising:

9. The ceramic heater according to any one of claims 1 to 4, further comprising an internal electrode which is an RF electrode and / or an ESC electrode in the ceramic plate.

10. The ceramic heater according to any one of claims 1 to 4, further comprising a cylindrical ceramic shaft attached concentrically to the second surface of the ceramic plate and having an internal space.

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