Multi-zone heater

Abstract

A multi-zone heater according to the present invention comprises: first and second feed terminals to which both ends of an inner-zone heater are connected; first and second relay terminals to which both ends of an outer-zone heater are connected; third and fourth feed terminals; a first jumper wire which connects the first relay terminal and the third feed terminal; and a second jumper wire which connects the second relay terminal and the fourth feed terminal, wherein the first and fourth feed terminals are metal terminals, the first and second jumper wires are made of metal, and the distance A between the third feed terminal and the fourth feed terminal, the distance B between the first relay terminal and the second relay terminal, and the shortest distance C between the first jumper wire and the second jumper wire, which are separated in the same direction, satisfy A>B>C, 10 mm≤A≤25 mm, and C≥1 mm.

Description

Multi-Zone Heater

[0001] The present invention relates to a multi-zone heater for heating semiconductor wafers.

[0002] Ceramic heaters are widely used as heaters for heating wafers in semiconductor manufacturing equipment. Known examples of such ceramic heaters include so-called multi-zone heaters, which are configured to heat multiple zones using separate heaters. One type of multi-zone heater is a two-zone heater, which includes a heating element (coil) for heating a central portion (inner zone) of a disc-shaped ceramic base and another heating element (coil) for heating a peripheral portion (outer zone) of the ceramic base, both embedded within a single plane within the ceramic base. Voltages can be applied to the heating elements independently, allowing for independent control of heat output from each heating element (see, for example, Patent Document 1).

[0003] In the case of a multi-zone heater in which the inner zone and the outer zone are heated by separate heating elements, as disclosed in Patent Document 1, the heating elements for each zone are generally arranged in multiple arcs concentric with a disk-shaped ceramic substrate.

[0004] A hollow shaft is connected to the center of the ceramic base. A power supply rod, which is a rod-shaped power supply member that supplies power from the outside, is provided inside the shaft, and a connection terminal (power supply terminal) is provided at the tip of the power supply rod.

[0005] The heating elements arranged in the inner zone are directly connected to the power supply terminals, while the heating elements arranged in the outer zone are connected to relay terminals and are connected to the power supply terminals via lead wires (jumper wires) that connect the relay terminals to the power supply terminals. The power supply terminals and relay terminals are, for example, spherical metal terminals into which the tips of the heating elements can be inserted and fixed by brazing or the like.

[0006] With the need for multi-layer semiconductors and the demand for lower costs, next-generation ceramic heaters are required to have high thermal uniformity and long life.

[0007] With regard to high thermal uniformity, from the viewpoint of generating heat from the heating element evenly throughout the ceramic substrate, it is desirable that the heating element occupy a large area on the flat surface where it is embedded.

[0008] However, when the heating elements are placed close to each other to ensure a sufficient area for them to occupy, it is necessary to place the power supply terminals close to each other as well. However, the size (width) of the power supply terminals is large compared to the thickness (width) of the heating elements, and therefore the power supply terminals have a corresponding volume. Therefore, if the power supply terminals are placed too close to each other, excessive thermal stress occurs in the portion of the ceramic base sandwiched between the power supply terminals, making it more likely that cracks will occur starting from that portion. This is undesirable because it ultimately hinders the extension of the lifespan.

[0009] On the other hand, if the power supply terminals are spaced farther apart than necessary, it becomes difficult to place a heating element therebetween, which reduces the uniformity of heat, and this is not preferable.

[0010] The same applies to the relay terminals to which the jumper wires are connected and the heating elements arranged in the outer zone.

[0011] International Publication No. 2019 / 181500

[0012] The present invention has been made in view of the above-mentioned problems, and has as its object to realize a multi-zone heater in which the arrangement of embedded objects in a ceramic substrate is suitable from the viewpoint of high thermal uniformity.

[0013] In order to solve the above problems, a first aspect of the present invention is a multi-zone heater that includes a disk-shaped ceramic base having one main surface serving as a wafer-mounting surface and is capable of heating a wafer mounted on the one main surface, the multi-zone heater including: an inner zone heater disposed in an inner zone of the ceramic base; first and second power supply terminals that are disposed in a central portion of the ceramic base and connected to both ends of the inner zone heater; an outer zone heater disposed in an outer zone of the ceramic base that is outside the inner zone; first and second relay terminals that are connected to both ends of the outer zone heater; third and fourth power supply terminals that are disposed in the central portion of the ceramic base; and a terminal that is connected to the first relay terminal and the third relay terminal. the first to fourth power supply terminals are metal terminals, the first jumper wire and the second jumper wire are metal, the direction of separation between the third power supply terminal and the fourth power supply terminal, the direction of separation between the first relay terminal and the second relay terminal, and the direction of separation between the first jumper wire and the second jumper wire are the same, and when the distance between the third power supply terminal and the fourth power supply terminal is A, the distance between the first relay terminal and the second relay terminal is B, and the shortest distance between the first jumper wire and the second jumper wire is C, A>B>C, 10mm≦A≦25mm, and C≧1mm.

[0014] A second aspect of the present invention is the multi-zone heater according to the first aspect, characterized in that the first to fourth power supply terminals have a diameter of 3 mm to 5 mm.

[0015] A third aspect of the present invention is the multi-zone heater according to the first or second aspect, further comprising: a hollow cylindrical ceramic shaft connected to the other main surface; and four power feed rods disposed inside the shaft and connected to the first through fourth power feed terminals, respectively, as power feed lines extending from an external power source to the inner zone heater and the outer zone heater.

[0016] A fourth aspect of the present invention is the multi-zone heater according to the first or second aspect, characterized in that the first and second relay terminals are metal terminals that are smaller than the first through fourth power supply terminals.

[0017] According to the first to fourth aspects of the present invention, the occurrence of cracks near the power supply terminals in a multi-zone heater is effectively suppressed, thereby realizing a multi-zone heater with high temperature uniformity and a long life.

[0018] 1 is a schematic plan view of the multi-zone heater 10. FIG. 2 is a schematic cross-sectional view of the multi-zone heater 10. FIG. 3 is a diagram showing in more detail the connection of a second jumper wire 46 and a power feed rod 54 to a fourth power feed terminal 44. FIG. 4 is a schematic enlarged plan view of the vicinity of the jumper wire of the multi-zone heater 10. FIG. 5 is a diagram showing a thermal stress evaluation position M in a simulation. FIG. 6 is a graph showing the dependency of thermal stress generated at the thermal stress evaluation position M on the distance A when the size of the power feed particle is changed to two levels.

[0019] <Configuration of Multi-Zone Heater> Fig. 1 is a schematic plan view of a multi-zone heater 10 according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of the multi-zone heater 10. Note that Fig. 1 uses a right-handed xyz coordinate system with the x-axis extending left to right as viewed in the drawing, and the z-axis in Fig. 2 also coincides with that in Fig. 1.

[0020] The multi-zone heater 10 is used as a support table (susceptor) that supports a semiconductor wafer downward in a semiconductor wafer heating step, which is one step in the semiconductor manufacturing process. A more specific example of such a heating step is heating a wafer in a step of forming a semiconductor thin film on the wafer by plasma CVD. In this embodiment, the multi-zone heater 10 is assumed to be incorporated into a semiconductor manufacturing device (not shown), such as a known plasma CVD device.

[0021] The multi-zone heater 10 mainly comprises a ceramic substrate 20 , an inner zone heater 30 , an outer zone heater 40 , a first jumper wire 45 , a second jumper wire 46 , and a shaft 50 .

[0022] The ceramic substrate 20 is a disk-shaped plate member made of a fired ceramic material, such as aluminum nitride, silicon carbide, silicon nitride, and aluminum oxide.

[0023] The ceramic base 20 has, for example, a diameter of 320 mm to 385 mm and a thickness of 10 mm to 30 mm. One main surface of the ceramic base 20 (the upper surface in FIG. 2) serves as a wafer mounting surface 22. The wafer mounting surface 22 may have a plurality of projections and recesses formed by embossing, or may have a plurality of grooves formed therein.

[0024] 1, the ceramic base 20 may be provided with a plurality of lift pin holes, which are through holes. Support pins (lift pins) provided in a semiconductor manufacturing apparatus (not shown) that can support downward a wafer placed on the upper surface of the ceramic base and raise and lower the wafer are freely inserted into the plurality of lift pin holes. The plurality of lift pin holes are provided at equal angular intervals in the circumferential direction at positions equidistant from the axial center O of the ceramic base 20 (i.e., on a circle concentric with the ceramic base 20).

[0025] Furthermore, the other main surface of the ceramic base 20 (the lower surface in FIG. 2) serves as a connection surface 24 of the shaft 50. The shaft 50 is a hollow cylindrical member made of a fired ceramic material similar to that of the ceramic base 20.

[0026] The ceramic substrate 20 is divided into an inner zone 20a and an outer zone 20b by an imaginary boundary circle 26, which is conceived as a circle concentric with the ceramic substrate 20. The inner zone 20a is a circular region inside the imaginary boundary circle 26. The outer zone 20b is an annular region outside the imaginary boundary circle 26.

[0027] An inner zone heater 30 is embedded in the inner zone 20a, and an outer zone heater 40 is embedded in the outer zone 20b.

[0028] The inner zone heater 30 is a heating element (coil) that is wired across the entire inner zone 20a in a plane (xy plane) parallel to the wafer mounting surface 22 inside the ceramic base 20. In the case shown in Fig. 1, the inner zone heater 30 is wired in a single stroke while being folded back in the vicinity of the yz plane that passes through the axial center O.

[0029] The outer zone heater 40 is a heating element (coil) that is wired across the entire outer zone 20b within the ceramic base 20 in the same plane (xy plane) as the inner zone heater 30. In the case shown in Fig. 1, the outer zone heater 40 is wired in a single stroke while being folded back in the vicinity of the yz plane that passes through the axial center O.

[0030] As shown in FIG. 1, the inner zone heater 30 and the outer zone heater 40 are arranged in the shape of arcs at equal intervals in the radial direction of the ceramic substrate 20, that is, in the shape of concentric arcs, in most parts except for the folded-back portions.

[0031] In addition, when the above-mentioned lift pin holes are provided, the inner zone heater 30 and the outer zone heater 40 may each be locally curved in the vicinity of the lift pin holes in order to suppress the occurrence of temperature unevenness due to the presence of such lift pin holes.

[0032] Examples of materials for the heating elements (coils) that make up the inner zone heater 30 and the outer zone heater 40 include molybdenum, tungsten, and molybdenum / tungsten compounds. The wire diameter of the heating elements is preferably about 0.2 mm to 0.8 mm, and the width in the coiled state (coil width) is preferably about 3.0 mm to 5.0 mm.

[0033] The number of turns per unit length of the coils constituting the inner zone heater 30 and the outer zone heater 40 may be appropriately changed depending on the location within the inner zone 20a and the outer zone 20b. For example, when plasma heating a wafer, temperature unevenness may occur on the wafer due to partial differences in the plasma heat input to the wafer. To eliminate such temperature unevenness, the number of turns per unit length may be changed depending on the location. The more turns a coil has per unit length, the more heat it generates and the higher the temperature it is likely to become. Instead of changing the number of turns of the coil, the winding diameter or the wire distance (the distance between adjacent coils) may be changed.

[0034] Both ends 30a, 30b of the inner zone heater 30 are connected to a first power supply terminal 31 and a second power supply terminal 32, respectively. The first power supply terminal 31 and the second power supply terminal 32 are embedded in the center of the ceramic base 20 (near the axial center O).

[0035] Both ends 40a, 40b of the outer zone heater 40 are connected to a first relay terminal 41 and a second relay terminal 42, respectively. The first relay terminal 41 and the second relay terminal 42 are embedded in the vicinity of the imaginary boundary circle 26 at positions symmetrical with respect to the yz plane passing through the axial center O.

[0036] One end 45a of a first jumper wire 45 is also connected to the first relay terminal 41, and one end 46a of a second jumper wire 46 is also connected to the second relay terminal 42. The other end 45b of the first jumper wire 45 and the other end 46b of the second jumper wire 46 are connected to the third power supply terminal 43 and the fourth power supply terminal 44, respectively. The third power supply terminal 43 and the fourth power supply terminal 44 are embedded in the vicinity of the axial center O of the ceramic base 20. Hereinafter, the first jumper wire 45 and the second jumper wire 46 will be collectively referred to simply as jumper wires.

[0037] The first power supply terminal 31, the second power supply terminal 32, the third power supply terminal 43, and the fourth power supply terminal 44 are metallic (e.g., molybdenum) and substantially spherical terminals with receptacles into which the ends of the heating elements (inner zone heater 30 or outer zone heater 40) or jumper wires can be inserted. In this embodiment, a component (e.g., a spherical terminal) being "metallic" means that the component contains 80% or more of a metal material as its main component. Hereinafter, the first power supply terminal 31, the second power supply terminal 32, the third power supply terminal 43, and the fourth power supply terminal 44 will be collectively referred to as "power supply terminals." The power supply terminals are connected to the heating elements or jumper wires by brazing (brazing material joining) the ends of the heating elements or jumper wires inserted into the receptacles. The size (diameter) of the power supply terminals may be 3 mm to 5 mm, preferably 4 mm to 5 mm.

[0038] The feed terminals are provided in positions symmetrical to one another (at four-fold symmetric positions) with respect to the axial center O within a single plane. In the example shown in Fig. 1, the first feed terminal 31 and the second feed terminal 32 are located within a single xy plane, and the third feed terminal 43 and the fourth feed terminal 44 are located within another xy plane. However, for convenience of illustration in Fig. 2, the feed terminals are shown in a row.

[0039] The first relay terminal 41 and the second relay terminal 42 are spherical terminals made of metal (e.g., molybdenum) and have receiving portions into which the heating element (outer zone heater 40) and the ends of the jumper wires can be inserted. Hereinafter, the first relay terminal 41 and the second relay terminal 42 will be collectively referred to simply as relay terminals.

[0040] The relay terminal is formed by brazing (solder joint) the ends of the heating element and jumper wire inserted into the receiving portion to connect the heating element and jumper wire. The size (diameter) of the relay terminal is preferably 3 mm to 5 mm, but is smaller than the size of the power supply terminal.

[0041] In the case shown in FIG. 1, the relay terminals are located within a certain xy plane, and most of the first jumper wire 45 and the second jumper wire 46 are arranged parallel to each other along the y-axis direction.

[0042] The jumper wire is made of a metal wire. Examples of the material of the wire include molybdenum, tungsten, and a molybdenum / tungsten compound. The diameter of the wire is not particularly limited, but is preferably 0.3 mm or more and 1.0 mm or less.

[0043] The jumper wire is provided in a manner that crosses the inner zone 20a. Fig. 2 schematically shows how the second jumper wire 46 crosses the inner zone 20a of the ceramic base 20 in a plane perpendicular to the z-axis. However, for simplicity of illustration, the inner zone heater 30, the outer zone heater 40, and the first jumper wire 45 are omitted from Fig. 2.

[0044] The inner zone heater 30, the outer zone heater 40, the four power supply terminals, the two relay terminals, and the two jumper wires are all brazed as required and then embedded in predetermined positions inside the ceramic base 20 as shown in FIG. 1 during the production of the ceramic base 20.

[0045] 2, the first power supply terminal 31 and the second power supply terminal 32 are further connected to a power supply rod 51 or a power supply rod 52, which is a power supply line from a power supply 61 for an inner zone heater outside the ceramic base 20. The third power supply terminal 43 and the fourth power supply terminal 44 are further connected to a power supply rod 53 or a power supply rod 54, which is a power supply line from a power supply 62 for an outer zone heater outside the ceramic base 20.

[0046] The power supply rods 51 to 54 are rod-shaped power supply members disposed inside the shaft 50. The power supply rods 51 to 54 are preferably made of metal, more preferably nickel. Alternatively, they may be made of a nickel alloy such as Inconel (a registered trademark of Special Metal Corporation). Alternatively, they may be made of a tungsten / nickel composite material. In place of the power supply rods 51 to 54, wire-shaped power supply members may be used.

[0047] FIG. 3 is a diagram showing in more detail the connection of the second jumper wire 46 and the power supply rod 54 to the fourth power supply terminal 44, which is schematically illustrated in FIG.

[0048] 3(a), when connecting the power feed rod 54 to the fourth power feed terminal 44 embedded in the ceramic base 20, a connecting hole h is first drilled from the connecting surface 24 of the ceramic base 20 toward the fourth power feed terminal 44 to insert the tip end 54a of the power feed rod 54. The connecting hole h is drilled in a manner that exposes the upper part of the fourth power feed terminal 44. At this time, the other end 46b of the second jumper wire 46 has already been brazed to the inserted portion 44a of the fourth power feed terminal 44, as described above.

[0049] Specifically, the joining holes h are provided in two stages: a primary hole h1 on the connection surface 24 side, and a secondary hole h2 that is smaller in diameter than the primary hole h1 and exposes the fourth power supply terminal 44 at its bottom. The side surface of the secondary hole h2 is also threaded. In other words, the secondary hole h2 is provided as a female thread.

[0050] Meanwhile, a rod guide part 55 having a thread that matches the female thread of the secondary hole h2 is annularly fixed to the side surface of the tip end 54a of the power supply rod 54. That is, a male thread is provided on the tip end 54a of the power supply rod 54 in the rod guide part 55. The rod guide part 55 is a cylindrical member made of, for example, nickel.

[0051] A thermal expansion adjustment part 56 is brazed to the substantially flat end surface 54b of the power supply rod 54. The thermal expansion adjustment part 56 is a disc-shaped conductive member made of, for example, Kovar. The thermal expansion adjustment part 56 is provided to absorb deformation due to thermal expansion of the power supply rod 54, which has a larger thermal expansion coefficient than the ceramic base 20, that occurs during operation of the multi-zone heater 10.

[0052] Then, by threading the male thread of the rod guide part 55 fixed to the power feed rod 54 into the female thread provided in the secondary hole h2, the power feed rod 54, with the thermal expansion adjustment part 56 brazed to its end face 54b, is fixed to the joining hole h. This achieves a state in which the fourth power feed terminal 44 and the power feed rod 54 are connected via the thermal expansion adjustment part 56, as shown in Fig. 3(b) . Note that, to ensure more reliable contact between the fourth power feed terminal 44 and the thermal expansion adjustment part 56, at least the portion of the fourth power feed terminal 44 exposed to the joining hole h may be flat.

[0053] The other power supply rods 51 to 53 are connected to the corresponding power supply terminals in the same manner as in FIG.

[0054] As described above, the size (diameter) of the power supply terminals may be 3 mm to 5 mm in order to ensure a suitable joining strength with the power supply rods 51 to 54. The size (diameter) of the relay terminals is smaller than that of the power supply terminals because they are not joined to the power supply rods.

[0055] The operation of the inner zone heater power supply 61 and the outer zone heater power supply 62 is controlled by a controller 70. As a result, in the multi-zone heater 10 according to this embodiment, the temperatures of the inner zone 20 a and the outer zone 20 b can be controlled independently. In other words, the multi-zone heater 10 has a configuration in which the inner zone 20 a and the outer zone 20 b outside it can be heated independently by separate heaters.

[0056] <Details of the Layout of Components> Next, a detailed description will be given of the layout of the power supply terminals, relay terminals, and jumper wires in the multi-zone heater 10. Fig. 4 is a schematic enlarged plan view of the multi-zone heater 10 in the vicinity of the jumper wires.

[0057] From the viewpoint of generating heat from the heating elements evenly throughout the ceramic substrate 20 in order to realize a multi-zone heater 10 with excellent heat uniformity, it is desirable that the heating elements (inner zone heater 30 and outer zone heater 40) occupy a large area on the embedded plane.

[0058] However, in this case, it is necessary to place the power supply terminals close to each other. However, since the size (width) of the power supply terminals is large compared to the wire width or coil width of the heating element and therefore the power supply terminals have a corresponding volume, if the power supply terminals are placed too close to each other, excessive thermal stress occurs in the portion of the ceramic base 20 sandwiched between the power supply terminals, making it more likely that cracks will occur starting from that portion.

[0059] Furthermore, since the power supply terminal is disposed inside the shaft 50, a temperature distribution is likely to occur near the power supply terminal due to heat dissipation from the shaft 50. This can also be a factor in excessive thermal stress.

[0060] The occurrence of cracks due to such excessive thermal stress is undesirable because it leads to an impairment of the long life of the multi-zone heater 10. In particular, in the vicinity of jumper wires as shown in Figure 4, the proximity of power supply terminals also leads to the proximity of jumper wires and relay terminals, making it more likely that cracks will occur.

[0061] In view of the above, in the multi-zone heater 10 according to this embodiment, the direction of separation between the third power supply terminal 43 and the fourth power supply terminal 44, the direction of separation between the first relay terminal 41 and the second relay terminal 42, and the direction of separation between the first jumper wire 45 and the second jumper wire 46 are all the same (the x-axis direction in FIG. 1 ), and the distance between the third power supply terminal 43 and the fourth power supply terminal 44 (the size of the gap between them in the x-axis direction) is A. When the distance between terminal 41 and second relay terminal 42 (the size of the gap between them in the x-axis direction) is B and the shortest distance between first jumper wire 45 and second jumper wire 46 (the smallest value of the gap between them in the x-axis direction) is C, third power supply terminal 43, fourth power supply terminal 44, first relay terminal 41, second relay terminal 42, first jumper wire 45, and second jumper wire 46 are arranged so as to satisfy the following equations (1) to (3).

[0062] A>B>C (1) 10mm≦A≦25mm (2) C≧1mm (3) The value of distance A is also the value of the distance between the first power supply terminal 31 and the second power supply terminal 32, the distance between the first power supply terminal 31 and the third power supply terminal 43, and the distance between the second power supply terminal 32 and the fourth power supply terminal 44.

[0063] The reason why distances A and B in formula (1) are specified to be greater than the shortest distance C is that the thermal stress generated in the power supply terminal and relay terminal, which are spherical terminals, is higher than that in jumper wires.

[0064] Furthermore, the distance B is specified to be smaller than the distance A because the relay terminal has a smaller size (diameter) than the power supply terminal, and therefore generates less thermal stress, and because the relay terminal, unlike the power supply terminal, is provided outside the shaft 50, there is no increase in thermal stress due to heat dissipation by the shaft 50.

[0065] The lower limit of equation (2), which defines the range of distance A, is based on the results of a simulation of thermal stress generated between the third power supply terminal 43 and the fourth power supply terminal 44. Fig. 5 is a diagram showing the thermal stress evaluation position M in the simulation. The ceramic substrate 20 was made of 99.9 atm% aluminum nitride (AlN) (the remainder being impurities). Fig. 6 is a graph showing the dependence of the thermal stress generated at the thermal stress evaluation position M on distance A when the size of the power supply particles is changed to two levels: 4 mm and 5 mm.

[0066] As shown in Fig. 5, the thermal stress evaluation position M is set to the midpoint between the third power supply terminal 43 and the fourth power supply terminal 44. The simulation conditions are as follows: temperature: 650°C; Young's modulus: 3.00 x 10 ５ [MPa]; Density: 3.33×10 －６ [kg / cm ３ ]; Thermal expansion coefficient: 5.00 × 10 －６ [1 / T].

[0067] As shown in FIG. 6, it was confirmed that the magnitude of the thermal stress occurring at the thermal stress evaluation position M tends to increase as the distance A decreases, regardless of the size of the power feed particle.

[0068] For example, when the ceramic base 20 is made of aluminum nitride (AlN), the strength is approximately 300 MPa. Therefore, even if the safety factor is set to 30%, if the thermal stress generated in the ceramic base 20 is 100 MPa or less, the risk of cracking is judged to be low. On the other hand, if the thermal stress generated in the ceramic base 20 exceeds 100 MPa, the risk of cracking is judged to be high.

[0069] As shown in Fig. 6, when the size of the power supply terminal is 4 mm or more, the generated thermal stress is 100 MPa or less if the distance A is 10 mm or more. Based on this, the lower limit of formula (2) is set to 10 mm.

[0070] On the other hand, if the power supply terminals are spaced farther apart than necessary, it becomes difficult to place a heating element between them, which reduces the uniform heating property, and this is undesirable. In consideration of this, the upper limit of formula (2) is set to 25 mm.

[0071] Furthermore, in formula (3), the minimum value of the shortest distance C is set to 1 mm. This is based on the fact that even if the jumper wire is thin compared to the size of the power supply terminal or relay terminal, if it is placed too close, the thermal stress cannot be ignored.

[0072] 1 and 4, most of the first jumper wire 45 and the second jumper wire 46 are linear (along the y-axis direction).

[0073] However, such a linear shape is not a required feature, and the shape when viewed from above may be serpentine (i.e., winding) or curved as a whole, as long as they are line-symmetrical with respect to a plane (yz plane) passing through the axial center O and the maximum distance between them is equal to or less than distance B. However, when the length along the y-axis (y-axis length) of first jumper wire 45 and second jumper wire 46 excluding the portions inserted into the power supply terminal and relay terminal shown in Figure 4 is L, the maximum distance may exceed distance B within a range of L / 4 close to the power supply terminal and relay terminal, respectively.

[0074] In this embodiment, the term "the first jumper wire 45 and the second jumper wire 46 are line-symmetrical" includes cases where they are positioned approximately symmetrically, and some degree of misalignment that inevitably occurs during manufacturing is permitted. For example, a misalignment of approximately 4 mm or less from the original line-symmetrical position is permitted. This degree of misalignment does not deteriorate thermal uniformity.

[0075] As described above, according to this embodiment, by adopting an arrangement in the multi-zone heater that satisfies the formulas (1) to (3), the occurrence of cracks near the power supply terminals is suitably suppressed, thereby realizing a multi-zone heater with high thermal uniformity and a long life.

Claims

1. A multi-zone heater having a disc-shaped ceramic base having one main surface serving as a wafer-mounting surface and capable of heating a wafer mounted on said one main surface, comprising: an inner zone heater disposed in an inner zone of said ceramic base; a first power supply terminal and a second power supply terminal disposed in a central portion of said ceramic base and connected to both ends of said inner zone heater; an outer zone heater disposed in an outer zone of said ceramic base outside said inner zone; a first relay terminal and a second relay terminal connected to both ends of said outer zone heater; a third power supply terminal and a fourth power supply terminal disposed in a central portion of said ceramic base; a first jumper wire connecting said first relay terminal and said third power supply terminal; and a second jumper wire connecting said second relay terminal and said fourth power supply terminal; a direction of separation between the third power supply terminal and the fourth power supply terminal, a direction of separation between the first relay terminal and the second relay terminal, and a direction of separation between the first jumper wire and the second jumper wire are the same; and, when a distance between the third power supply terminal and the fourth power supply terminal is A, a distance between the first relay terminal and the second relay terminal is B, and a shortest distance between the first jumper wire and the second jumper wire is C, the following relationships are satisfied: A>B>C; 10 mm≦A≦25 mm; C≧1 mm.

2. A multi-zone heater according to claim 1, wherein the diameters of the first to fourth power supply terminals are 3 mm to 5 mm.

3. A multi-zone heater according to claim 1 or 2, further comprising: a hollow cylindrical ceramic shaft connected to the other main surface; and four power supply rods arranged inside the shaft and connected to the first through fourth power supply terminals, respectively, which are power supply lines from an external power source to the inner zone heater and the outer zone heater.

4. A multi-zone heater according to claim 1 or 2, characterized in that the first and second relay terminals are metal terminals smaller than the first through fourth power supply terminals.

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