JP7483952B2 - heater - Google Patents

Description

The present disclosure relates to a heater.

Conventionally, heaters are known that heat substrates such as semiconductor wafers during the semiconductor manufacturing process. One such heater is known to have a disk-shaped ceramic base and a resistive heating element embedded in the base (see Patent Document 1).

JP 2015-529969 A

A heater according to one aspect of the present disclosure has a base, a resistive heating element, and a cavity. The base is made of ceramics and has an upper surface, which is a heating surface, and a lower surface, which is the surface opposite to the upper surface. The resistive heating element is located inside the base. At least a portion of the cavity is located inside the base between the resistive heating element and a side surface of the base. In addition, in a cross-sectional view of the base in a direction perpendicular to the upper surface, the cavity has an outer wall surface located on the side surface and an inner wall surface facing the outer wall surface, and at least a portion of the inner wall surface moves away from the central axis of the base in a direction perpendicular to the upper surface as it moves from the lower surface to the upper surface.

FIG. 1 is a schematic perspective view of a heater system according to a first embodiment. FIG. 2 is a schematic cross-sectional view of the heater according to the first embodiment. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. FIG. 4 is a schematic cross-sectional side view of the periphery of a cavity in a heater according to a second embodiment. FIG. 5 is a schematic enlarged view of a portion H shown in FIG. FIG. 6 is a schematic enlarged view of the portion H shown in FIG. 4 . FIG. 7 is a schematic cross-sectional side view of the periphery of a cavity in a heater according to a third embodiment. FIG. 8 is a schematic cross-sectional side view of the periphery of a cavity in a heater according to a fourth embodiment. FIG. 9 is a schematic cross-sectional side view of the periphery of a cavity in a heater according to a fifth embodiment. FIG. 10 is a schematic cross-sectional view of a heater according to a sixth embodiment.

Below, a detailed description will be given of a form for implementing the heater according to the present disclosure (hereinafter, referred to as an "embodiment") with reference to the drawings. Note that the heater according to the present disclosure is not limited to this embodiment. Furthermore, each embodiment can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same parts in each of the following embodiments are given the same reference numerals, and duplicate explanations will be omitted.

In addition, in the embodiments described below, expressions such as "constant," "orthogonal," "vertical," and "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "vertical," or "parallel" in the strict sense. In other words, each of the above expressions allows for deviations due to, for example, manufacturing precision, installation precision, and the like.

In addition, the figures referenced below are schematic for the convenience of explanation. Therefore, details may be omitted and the dimensional ratios do not necessarily correspond to the actual ones.

In addition, in order to make the explanation easier to understand, in each of the drawings referenced below, the vertical upward direction is defined as the Z-axis direction.

A heater is known that has a disk-shaped ceramic base and a resistance heating element embedded in the base. There is room for further improvement in this type of heater in terms of improving its thermal efficiency.

Therefore, there is a need to provide a heater that can improve thermal efficiency.

First Embodiment
First, the configuration of the heater system according to the first embodiment will be described with reference to Figures 1 to 3. Figure 1 is a schematic perspective view of the heater system 1 according to the first embodiment. Figure 2 is a schematic cross-sectional view of a heater 2 according to the first embodiment. Figure 3 is a schematic cross-sectional view taken along the line III-III in Figure 2. Note that Figure 2 also shows a schematic cross-sectional view taken along the line II-II in Figure 1. In Figure 2, the shaft 20 is omitted, and only the cross section of the base 10 is shown.

The heater system 1 according to the first embodiment shown in Fig. 1 heats semiconductor wafers, quartz wafers, and other wafers (hereinafter simply referred to as "wafers"). For example, the heater system 1 is mounted in a substrate processing apparatus that performs plasma processing or the like on the wafers.

As shown in FIG. 1, the heater system 1 has a heater 2, power supply units 5a and 5b, and a control unit 6.

As shown in Figures 1 and 2, the heater 2 has a base 10, a shaft 20, a resistive heating element 30, an electrode layer 40, and a plurality of power supply wires 45a, 45b.

The base 10 has a disk shape with thickness in the vertical direction (Z direction). Specifically, the base 10 has an upper surface 101 and a lower surface 102 that are circular when viewed from above, and a side surface 103 that connects the upper surface 101 and the lower surface 102. The upper surface 101 and the lower surface 102 of the base 10 are approximately parallel. A wafer W (see FIG. 2), which is an example of an object to be heated, is placed on the upper surface 101 of the base 10. In other words, the upper surface 101 of the base 10 corresponds to a heating surface. The planar shape and various dimensions of the base 10 may be set appropriately taking into account the shape and dimensions of the object to be heated.

The base 10 is made of, for example, ceramics and has insulating properties. The ceramics constituting the base 10 are, for example, sintered bodies mainly composed of aluminum nitride (AlN), aluminum oxide (Al ₂ O ₃ , alumina), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), etc. The main component is, for example, a material that occupies 50 mass % or more or 80 mass % or more of the material. When the main component of the base 10 is aluminum nitride, the base 10 may contain a compound of yttrium (Y). Examples of Y compounds include YAG (Y ₃ Al ₅ O ₁₂ ) and Y ₂ O ₃ .

The shape of the base 10 is arbitrary. For example, in the first embodiment, the shape of the base 10 is circular in a plan view, but is not limited thereto, and may be elliptical, rectangular, trapezoidal, etc. in a plan view. Also, here, an example is shown in which the upper surface 101 of the base 10 is a uniform flat surface, but the upper surface 101 of the base 10 may have, for example, grooves and steps.

The shaft 20 has a cylindrical shape with both ends open. The shaft 20 is connected to the lower surface 102 of the base 10. In one embodiment, the shaft 20 is bonded (adhered) to the lower surface 102 of the base 10 by an adhesive. In another embodiment, the shaft 20 may be bonded to the base 10 by solid-state welding. The shape of the shaft 20 is arbitrary. In one embodiment, the shape of the shaft 20 is cylindrical. In another embodiment, the shape of the shaft 20 may be, for example, a square tube.

The material of the shaft 20 is arbitrary. In one embodiment, the material of the shaft 20 is insulating ceramics. In another embodiment, the material of the shaft 20 may be, for example, a conductive material (metal). The ceramic constituting the shaft 20 is, for example, a sintered body containing aluminum nitride (AlN), aluminum oxide (Al ₂ O ₃ , alumina), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), or the like as a main component.

2, the resistive heating element 30 and the electrode layer 40 are located inside the base 10. Specifically, the resistive heating element 30 is located between the upper surface 101 and the lower surface 102 of the base 10, and the electrode layer 40 is located between the upper surface 101 of the base 10 and the resistive heating element 30. In other words, the resistive heating element 30 and the electrode layer 40 are located from the upper surface 101 to the lower surface 102 of the base 10 in the order of the electrode layer 40 and the resistive heating element 30.

The resistive heating element 30 is made of, for example, a metal such as Ni, W, Mo, or Pt, or an alloy containing at least one of the above metals. The electrode layer 40 is also made of, for example, a metal such as Ni, W, Mo, or Pt, or an alloy containing at least one of the above metals.

The resistive heating element 30 and the electrode layer 40 extend along the upper surface 101. The resistive heating element 30 is arranged in a predetermined pattern, such as a spiral or meandering pattern, so that the outer shape in a plan view is circular. The electrode layer 40 has a disk shape in a plan view.

The resistance heating element 30 generates heat by Joule heat generated by the power supplied from the power supply unit 5a (described later) via the power supply line 45a. This allows the heater 2 to heat the wafer W placed on the upper surface 101 of the base 10.

In the first embodiment, an example is shown in which the heater 2 is a so-called single-zone heater. Such a heater 2 has one resistive heating element 30 that is spread in a circular shape in an area narrower than the upper surface 101. However, this is not limited to this, and the heater 2 may be a multi-zone heater that can individually control multiple areas on the upper surface 101 of the base 10. In this case, the heater 2 only needs to have multiple resistive heating elements 30 that are spread in different areas of the upper surface 101 of the base 10. When the heater 2 is a multi-zone heater, the number of power supply lines 45a increases according to the number of areas that are individually controlled.

In the first embodiment, the electrode layer 40 is, for example, an electrostatic adsorption electrode for adsorbing the wafer W onto the upper surface 101 of the substrate 10. The electrode layer 40 generates an electrostatic force by power supplied from a power supply unit 5b described later. The heater 2 can adsorb the wafer W onto the upper surface 101 of the substrate 10 by using the electrostatic force.

The electrode layer 40 is not limited to the above example, and may be, for example, an RF (radio frequency) electrode for generating plasma. The heater 2 does not need to have an electrode layer 40. In other words, it is sufficient that at least the resistive heating element 30 is located inside the base 10.

The power supply line 45a electrically connects the resistance heating element 30 located inside the base 10 to the power supply unit 5a located outside the base 10. The power supply line 45b electrically connects the electrode layer 40 located inside the base 10 to the power supply unit 5b located outside the base 10. As shown in FIG. 2, the heater 2 has a terminal 41 for connecting the resistance heating element 30 and the power supply line 45a. Although not shown here, the heater 2 also has a terminal for connecting the electrode layer 40 and the power supply line 45b.

The terminal 41 is, for example, a metal having a certain length in the vertical direction. The upper end side of the terminal 41 is located inside the base 10, and the lower end side is located outside the base 10. In the illustrated example, the terminal 41 is electrically connected to the resistance heating element 30. The shape of the terminal 41 is arbitrary. In one embodiment, the shape of the terminal 41 is cylindrical. The terminal 41 is, for example, made of a metal such as Ni, W, Mo, and Pt, or an alloy containing at least one of the above metals.

The power supply unit 5a is electrically connected to the resistance heating element 30 via the power supply line 45a and supplies power to the resistance heating element 30 via the power supply line 45a. For example, the power supply unit 5a includes a power supply circuit that converts power supplied from a power source (not shown) into an appropriate voltage. The power supply unit 5b is electrically connected to the electrode layer 40 via the power supply line 45b and supplies power to the electrode layer 40 via the power supply line 45b. The control unit 6 controls the supply of power in the power supply units 5a and 5b. Note that the number of power supply lines 45a and 45b, power supply units 5a and 5b, and control unit 6 shown in FIG. 1 is an example. For example, the heater system 1 may have a first control unit for controlling the power supply unit 5a and a second control unit for controlling the power supply unit 5b. Also, in FIG. 1, the power supply units 5a and 5b are shown as separate units, but the power supply units 5a and 5b may be integrated.

The heater system 1 is configured as described above, and heats the wafer W placed on the upper surface 101 by using power supplied from the power supply unit 5a to generate heat in the resistive heating element 30 inside the base 10.

Here, it is difficult to extend the resistive heating element 30 and the electrode layer 40 to the vicinity of the side surface 103 of the base 10. This is because if the resistive heating element 30 and the electrode layer 40 are extended to the vicinity of the side surface 103 of the base 10, delamination may occur in the base 10. For this reason, the resistive heating element 30 and the electrode layer 40 are arranged at a certain distance from the side surface 103 of the base 10. In other words, the resistive heating element 30 and the electrode layer 40 have a smaller diameter than the upper surface 101 of the base 10. Note that the resistive heating element 30 and the electrode layer 40 have a smaller diameter than the wafer W placed on the upper surface 101 of the base 10.

The heat generated by the resistive heating element 30 is transferred not only to the top surface 101 of the substrate 10 on which the wafer W, which is the object to be heated, is placed, but also to the side surface 103 of the substrate 10. In order to improve the thermal efficiency of the heater 2, it is desirable to suppress the thermal conduction to the side surface 103 of the substrate 10 where the object to be heated is not located, i.e., where there is no need to heat it.

In contrast, the heater 2 according to the first embodiment has a cavity 50 inside the base 10. The cavity 50 is located at least between the resistive heating element 30 and the side surface 103 of the base 10.

A gas, for example air, exists inside the cavity 50. The air inside the cavity 50 has a lower thermal conductivity than the base 10. Therefore, by providing the cavity 50 between the resistive heating element 30 and the side surface 103 of the base 10, it is possible to suppress the thermal conduction from the resistive heating element 30 to the side surface 103 of the base 10.

The gas present inside the cavity 50 is not limited to air, and may be, for example, an inert gas. Examples of inert gases that may be used include argon, helium, and nitrogen. The inside of the cavity 50 may be in a vacuum state or a reduced pressure state. A reduced pressure state refers to a state in which the pressure inside the cavity 50 is lower than atmospheric pressure. By making the inside of the cavity 50 a vacuum state or a reduced pressure state, it is possible to suppress the load on the base 10 due to the thermal expansion of the gas when the inside of the cavity 50 is a closed space.

2, that is, in a cross-sectional view of the base 10 in a cross-section passing through the center of the upper surface 101 and in a cross-sectional view of the base 10 in a direction perpendicular to the upper surface 101 (Z-axis direction), a virtual line perpendicular to the upper surface 101 and passing through the outer peripheral end 31 of the resistance heating element 30 is defined as a "first virtual line L1". In addition, in the cross-sectional view, a virtual line extending from the outer peripheral end 31 of the resistance heating element 30 and inclined more toward the outside of the base 10 than the first virtual line L1 is defined as a "second virtual line L2". In the cross-sectional view shown in FIG. 2 (hereinafter referred to as a "side cross-sectional view"), the cavity 50 according to the first embodiment extends obliquely along the second virtual line L2.

Specifically, the cavity 50 according to the first embodiment has a first space 50a, a second space 50b, and a third space 50c that are partitioned from one another in a side cross-sectional view. The first space 50a, the second space 50b, and the third space 50c are aligned along the second virtual line L2. Specifically, the first space 50a, the second space 50b, and the third space 50c are aligned along the second virtual line L2 in the order of the first space 50a, the second space 50b, and the third space 50c in order of proximity to the outer peripheral end 31 of the resistance heating element 30.

From another perspective, the positions of the ceiling surfaces of the first space 50a, the second space 50b, and the third space 50c increase in the order of the first space 50a, the second space 50b, and the third space 50c. That is, the positions of the ceiling surfaces of the first space 50a, the second space 50b, and the third space 50c are lowest in the first space 50a, which is closest to the outer peripheral end 31 of the resistance heating element 30, and highest in the third space 50c, which is farthest from the outer peripheral end 31 of the resistance heating element 30 (closest to the side surface 103 of the base 10).

When comparing the wafer W, which is the object to be heated, with the resistance heating element 30, the wafer W has a larger diameter. If the cavity extends from near the outer periphery 31 of the resistance heating element 30 (for example, the position of the first space 50a) along the first virtual line L1, heat conduction to the outer periphery of the wafer W is suppressed, making it difficult to heat the wafer W uniformly. For this reason, one idea is to position the cavity extending along the first virtual line L1 outward from the outer periphery of the wafer W. However, in this case, the heat conduction to the area that contributes less to the heat conduction to the wafer W, which is the object to be heated, is increased, resulting in low thermal efficiency. Here, the area that contributes less to the heat conduction to the object to be heated refers to, for example, an area other than the area surrounded by the upper surface of the resistance heating element 30, the lower surface of the wafer W, and the virtual line connecting the outer periphery 31 of the resistance heating element 30 and the outer periphery of the wafer W.

In contrast, the cavity 50 according to the first embodiment extends obliquely along the second virtual line L2 as described above. Therefore, the heater 2 having such a cavity 50 can improve thermal efficiency. In other words, the wafer W can be heated uniformly while suppressing heat conduction to areas that contribute little to heat conduction to the wafer W, which is the object to be heated.

From another perspective, the inner wall surface 512 of the cavity 50 becomes more distant from the central axis L0 of the base 10 in a direction perpendicular to the upper surface 101 as it moves from the lower surface 102 toward the upper surface 101 of the base 10. Specifically, each of the spaces 50a to 50c of the cavity 50 has an outer wall surface 511 located on the side surface 103 of the base 10 and an inner wall surface 512 facing the outer wall surface 511.

Here, the distance from the central axis L0 of the base 10 to the inner wall surface 512 of the first space 50a is defined as "distance D1", the distance from the central axis L0 to the inner wall surface 512 of the second space 50b is defined as "distance D2", and the distance from the central axis L0 to the inner wall surface 512 of the third space 50c is defined as "distance D3". In this case, of the distances D1 to D3, the distance D1 is the shortest, followed by the distance D2, and the distance D3 is the longest. By adopting such a configuration, it is possible to improve the thermal efficiency. In other words, it is possible to uniformly heat the wafer W, which is the object to be heated, while suppressing the thermal conduction to an area that contributes little to the thermal conduction to the wafer W.

2 shows an example in which distance D1 is the shortest, followed by distance D2 and then distance D3, but it is sufficient that at least a portion of the inner wall surface 512 of the cavity 50 is farther from the central axis L0 the further from the lower surface 102 to the upper surface 101 of the base 10. That is, for example, distance D3 may be the longest, and distance D1 and distance D2 may be the same length. Alternatively, distance D1 may be the shortest, and distance D2 and distance D3 may be the same length.

In addition, the inner wall surface 512 of the cavity 50 may be located in a region defined by the first virtual line L1, the second virtual line L2, the side surface 103 of the base 10, and the lower surface 102 of the base 10 in a side cross-sectional view. In other words, the cavity 50 does not necessarily need to be along the second virtual line L2.

In the first embodiment, the second imaginary line L2 is an imaginary line extending from the outer peripheral end 31 of the resistance heating element 30 toward the outer edge 104 of the upper surface 101. According to the heater 2 having the cavity 50 extending along the second imaginary line L2, the thermal efficiency can be appropriately improved.

Without being limited thereto, the second virtual line L2 may be, for example, a virtual line connecting the outer peripheral end 31 of the resistance heating element 30 and the outer peripheral end of the wafer W. The second virtual line L2 may also be a virtual line connecting the outer peripheral end 31 of the resistance heating element 30 and the upper surface 101 (in other words, the upper surface 101 exposed from the wafer W) located between the outer peripheral end and the outer edge 104 of the wafer W. Note that the "outer peripheral end of the wafer W" here refers to the assumed position of the outer peripheral end of the wafer W when it is assumed that the wafer W is properly placed on the upper surface 101 (so that the center of the wafer W coincides with the center of the upper surface 101).

In the first embodiment, a portion of the cavity 50 (here, the first space 50a) is located to the side of the outer peripheral end 31 of the resistance heating element 30. That is, in a side cross-sectional view, the cavity 50 overlaps with a third imaginary line L3 that extends horizontally from the outer peripheral end 31 of the resistance heating element 30 toward the side surface 103 of the base 10. In this way, by having a portion of the cavity 50 located to the side of the outer peripheral end 31 of the resistance heating element 30, it is possible to more reliably suppress heat conduction from the resistance heating element 30 to the side surface 103 of the base 10.

3, that is, in a cross-sectional view of the base 10 passing through the cavity 50 and parallel to the upper surface 101 (hereinafter referred to as "planar cross-sectional view"), the third space 50c extends circumferentially. Although not shown here, the first space 50a and the second space 50b also extend circumferentially in the planar cross-sectional view. With this configuration, the thermal efficiency can be improved over the entire circumference of the base 10. Note that, as described later, one or more walls supporting the ceilings of the first space 50a, the second space 50b, and the third space 50c may be partially located inside the first space 50a, the second space 50b, and the third space 50c.

In addition, the first space 50a, the second space 50b, and the third space 50c are partitioned in the side cross-sectional view shown in Figure 2, but may be connected in other side cross-sectional views. In this way, the first space 50a, the second space 50b, and the third space 50c do not necessarily have to be independent spaces.

In addition, here, an example is shown in which the side cross-sectional areas of the first space 50a, the second space 50b, and the third space 50c are the same, but the side cross-sectional areas of the first space 50a, the second space 50b, and the third space 50c may be different. For example, the side cross-sectional areas of the first space 50a, the second space 50b, and the third space 50c may be the largest in the third space 50c closest to the resistance heating element 30, and the smallest in the first space 50a farthest from the resistance heating element 30. By relatively increasing the side cross-sectional area of the third space 50c closest to the resistance heating element 30, it is possible to further suppress the heat conduction to the side surface 103 of the base 10. In addition, by relatively decreasing the side cross-sectional area of the first space 50a farthest from the resistance heating element 30, it is possible to suppress the decrease in strength of the base 10.

In the first embodiment, the cavity 50 extends so as to be in contact with the second virtual line L2, but the cavity 50 does not necessarily need to be in contact with the second virtual line L2 and may be spaced apart from the second virtual line L2. In other words, the cavity 50 needs to extend at least parallel to the second virtual line L2. Preferably, the cavity 50 is provided at a position in contact with the second virtual line L2 or at a position overlapping with the second virtual line L2.

Second Embodiment
Fig. 4 is a schematic cross-sectional side view of the periphery of a cavity in a heater according to the second embodiment. As shown in Fig. 4, in a heater 2A according to the second embodiment, a base 10A has a cavity 50A extending along a second imaginary line L2 and a third imaginary line L3.

Specifically, the cavity 50A is divided into fourth to ninth spaces 50d to 50i in a side cross-sectional view. The fourth to ninth spaces 50d to 50i are arranged in a lattice pattern with intervals between them. Among the fourth to ninth spaces 50d to 50i, the fourth space 50d, the fifth space 50e, and the seventh space 50g are arranged in this order from the side of the resistance heating element 30 along the third virtual line L3. In addition, the sixth space 50f is arranged above the fifth space 50e with an interval therebetween, and the eighth space 50h is arranged above the seventh space 50g with an interval therebetween. Furthermore, the ninth space 50i is arranged above the eighth space 50h with an interval therebetween. Of the fourth to ninth spaces 50d to 50i, the fourth space 50d, the sixth space 50f, and the ninth space 50i are arranged along the second virtual line L2. Each of the fourth to ninth spaces 50d to 50i extends circumferentially in a plan cross-sectional view, similar to the third space 50c shown in FIG.

In this way, the cavity 50A may extend along the second virtual line L2 and the third virtual line L3. This configuration can further suppress the heat conduction from the outer peripheral end 31 of the resistance heating element 30 to the side surface 103 of the base 10A, that is, the heat conduction to the region that contributes less to the heat conduction to the wafer W, which is the object to be heated. In addition, the base 10A in the upper part (ninth space 50i) of the cavity 50A is denser than the base 10A in the lower part (fourth space 50d, fifth space 50e, and seventh space 50g) of the cavity 50A, so that the strength against the thermal stress caused by the thermal cycle can be increased.

Furthermore, by dividing the hollow portion 50A into a number of spaces (here, the fourth to ninth spaces 50d to 50i) in a lattice pattern rather than making it one large space, it is possible to prevent a decrease in the strength of the base body 10A.

It should be noted that the fourth to ninth spaces 50d to 50i do not necessarily need to be partitioned around the entire circumference of the base 10A. That is, two adjacent cavities among the fourth to ninth spaces 50d to 50i may be connected in a side cross-sectional view different from the side cross-sectional view shown in FIG. 4. For example, the fourth space 50d and the fifth space 50e may be connected in a side cross-sectional view different from the side cross-sectional view shown in FIG. 4. Similarly, the fifth space 50e and the sixth space 50f may be connected in a side cross-sectional view different from the side cross-sectional view shown in FIG. 4.

Figure 5 is an example of a schematic enlarged view of part H shown in Figure 4. As shown in Figure 5, hollow portion 50A (here, sixth space 50f and fifth space 50e) has, for example, a plurality (four here) of corners 501 and a plurality (four here) of sides 502 connecting adjacent corners 501 in a side cross-sectional view. At least the centers of the plurality of sides 502 of hollow portion 50A may be located more inward than the plurality of corners 501 of hollow portion 50A.

Figure 6 is another example of a schematic enlarged view of part H shown in Figure 4. As shown in Figure 6, the base 10A has a gap 55 between two adjacent spaces (here, as an example, the sixth space 50f and the fifth space 50e) in a side cross-sectional view, the gap 55 being lower in height than these spaces. The gap 55 does not necessarily need to be located around the entire circumference of the base 10A.

In this way, by positioning the gap 55 between two adjacent spaces in the hollow portion 50A, the heat generated in the resistive heating element 30 can be further prevented from passing between the two spaces and being transmitted to the side surface 103 of the base 10A (see Figure 4).

Third Embodiment
Fig. 7 is a schematic side cross-sectional view of the periphery of a cavity in a heater according to the third embodiment. As shown in Fig. 7, in a heater 2B according to the third embodiment, a base 10B has a cavity 50B extending along a second imaginary line L2 and a third imaginary line L3.

Specifically, the hollow portion 50B according to the third embodiment has a triangular shape in a side cross-sectional view, with one of the three sides extending along the second virtual line L2 and the other extending along the third virtual line L3.

In this way, the cavity 50B may have a triangular shape in a side cross-sectional view. With this configuration, it is possible to further suppress the heat conduction from the outer peripheral end 31 of the resistance heating element 30 to the side surface 103 of the base 10B. In addition, since the base 10B in the upper part of the cavity 50B is denser than the base 10B in the lower part of the cavity 50B, it is possible to increase the strength against thermal stress caused by thermal cycles.

In the example shown in FIG. 7, the side of hollow portion 50B along second virtual line L2 is away from second virtual line L2, but the side of hollow portion 50B along second virtual line L2 may be in contact with second virtual line L2 or may overlap with second virtual line L2.

Fourth Embodiment
Fig. 8 is a schematic side cross-sectional view of the periphery of a cavity in a heater according to the fourth embodiment. As shown in Fig. 8, in a heater 2C according to the fourth embodiment, a base 10C has a cavity 50C extending along a second imaginary line L2 and a third imaginary line L3.

The hollow portion 50C according to the fourth embodiment has a stepped shape in a side cross-sectional view. Specifically, the hollow portion 50C corresponds to a hollow portion 50B shown in FIG. 7, for example, in which the shape of the side along the second virtual line L2 is replaced with a stepped shape along the second virtual line L2, specifically, a shape in which straight lines along the first virtual line L1 and straight lines along the third virtual line L3 are alternately arranged.

In this way, the cavity 50C may have a stepped shape in a side cross-sectional view. In this case, too, the same effect as that of the heater 2B according to the third embodiment can be obtained. That is, the heat conduction from the outer peripheral end 31 of the resistance heating element 30 to the side surface 103 of the base 10C can be further suppressed. In addition, since the base 10C in the upper part of the cavity 50C is denser than the base 10C in the lower part of the cavity 50C, the strength against thermal stress caused by thermal cycles can be increased.

Fifth Embodiment
9 is a schematic side cross-sectional view of the periphery of a cavity in a heater according to the fifth embodiment. As shown in FIG. 9, in a heater 2D according to the fifth embodiment, a base 10D has a cavity 50D. The cavity 50D according to the fifth embodiment has a shape in which, for example, the cavity 50C according to the fourth embodiment is divided by a plurality of (here, two) walls 105 in a side cross-sectional view. The walls 105 extend along a first imaginary line L1, and in a side cross-sectional view, a first end (lower end) of both ends is located on the bottom surface of the cavity 50D, and a second end (upper end) of both ends is located on the ceiling surface of the cavity 50D.

The wall 105 divides the cavity 50D into a tenth space 50j, an eleventh space 50k, and a twelfth space 50m in a side cross-sectional view. The wall 105 does not necessarily need to be provided around the entire circumference of the base 10D, but may be provided partially in the circumferential direction of the base 10D. That is, for example, the tenth space 50j and the eleventh space 50k may be connected in another side cross-sectional view. Similarly, the eleventh space 50k and the twelfth space 50m may be connected in another side cross-sectional view.

In this manner, the cavity 50D may have a wall portion 105. With this configuration, the cavity 50D can be formed wider while maintaining the strength of the base body 10D.

Sixth Embodiment
Fig. 10 is a schematic cross-sectional view of a heater according to the sixth embodiment. As shown in Fig. 10, in a heater 2E according to the sixth embodiment, a base 10E has a cavity 50E.

The cavity 50E according to the sixth embodiment has a first cavity 51 and a second cavity 52. The first cavity 51 is a cavity located between the resistive heating element 30 and the side surface 103 of the base 10E. Here, an example is shown in which the shape of the first cavity 51 in a side cross-sectional view is the same as that of the cavity 50D according to the fifth embodiment, but the shape of the first cavity 51 may be the same as that of the cavity 50, 50A to 50C according to the first to fourth embodiments.

The second cavity 52 is a cavity located on the surface of the base 10E opposite the heating surface, i.e., between the lower surface 102 of the base 10E and the resistance heating element 30. The second cavity 52 extends along the upper surface 101 of the base 10E and is connected to the first cavity 51 at both ends.

In this manner, the cavity 50E may have a second cavity 52 located between the underside 102 of the base 10E and the resistance heating element 30. With this configuration, heat conduction to the underside 102 of the base 10E can be suppressed in addition to the side surface 103 of the base 10E, thereby further improving thermal efficiency.

10, the cavity 50E may also have multiple wall portions 105 in the second cavity 52. With this configuration, the cavity 50E can be made wider while maintaining the strength of the base 10E.

Other Embodiments
In each of the above-described embodiments, the cavities 50, 50A-50E may be used, in addition to functioning as a heat insulating layer, as a flow path for gas to be supplied to the wafer W placed on the upper surface 101. In this case, the cavities 50, 50A-50E may further include an inlet path for introducing the gas and an outlet path communicating with the upper surface 101. An example of the gas to be introduced into the cavities 50, 50A-50E is an inert gas such as helium gas.

In this way, the cavities 50, 50A to 50E may be used as gas flow paths. In this case, there is no need to provide a separate gas flow path.

In addition, in each of the above-described embodiments, the base 10, 10A to 10E may be formed as a single unit, rather than being made by joining multiple members together. With such a configuration, it is not necessary to provide a bonding layer, for example, and this can improve reliability against thermal cycles.

(Heater manufacturing method)
Next, a method for manufacturing a heater according to the present disclosure will be described. In the method for manufacturing a heater, for example, the base body, the shaft, and the power supply line are individually manufactured. Then, these members are fixed to each other. Note that the base body and the shaft may be manufactured in part or in whole as a single body. The method for manufacturing the shaft and the power supply line may be the same as, for example, various known methods.

The base is formed by stacking a plurality of ceramic green sheets. Specifically, a ceramic green sheet constituting the base, a metal sheet constituting the resistance heating element, and a metal sheet constituting the electrode layer are prepared. Then, the prepared sheets are stacked. Here, a plurality of types of ceramic green sheets with different shapes are prepared to form a cavity. For example, when forming a peripheral cavity in the base in a planar cross-sectional view, such as the third space 50c shown in FIG. 3, in addition to a circular first ceramic green sheet having approximately the same diameter as the upper surface of the base, a circular second ceramic green sheet having a smaller diameter than the upper surface of the base, and an annular third ceramic green sheet having an inner diameter larger than that of the second ceramic green sheet and an outer diameter the same as that of the first ceramic green sheet are prepared. Then, the second ceramic green sheet and the third ceramic green sheet are stacked on the first ceramic green sheet. At this time, the second ceramic green sheet is arranged inside the annular third ceramic green sheet. Then, the first ceramic green sheet is stacked on the second ceramic green sheet and the third ceramic green sheet.

Next, the laminate of the ceramic green sheets and metal sheets is degreased and fired. The firing temperature is, for example, 1700°C to 1850°C. If the cavity is a closed space, the firing atmosphere during firing can be made vacuum, allowing gas to be discharged from the communicating holes in the ceramic green sheets that were created during degreasing, and the cavity can be made into a vacuum state. Metal paste or wire may also be used instead of the metal sheet.

Thereafter, holes for inserting terminals are formed in the fired laminate by, for example, drilling, and the terminals are inserted into the formed holes to bond the terminals to the laminate via a bonding layer. The bonding layer may be, for example, a metallized layer using an Ag-Ti-Cu alloy. The bonding layer may be formed by sintering a paste of conductive material, such as platinum, by heat treatment. In this case, a paste of conductive material, such as platinum, is applied to the tip of the terminal in advance. Next, the laminate with the terminals attached is heat-treated in a vacuum to sinter the conductive material. The treatment temperature at this time is, for example, 1250°C. This results in a base according to the present disclosure.

The manufacturing method of the base body 10B according to the third embodiment may be, for example, a method of preparing a first sintered body having a bottomed cylindrical shape (concave in side cross section) and a second sintered body having a cylindrical upper part and an inverted truncated cone lower part, and joining them using a joining material such as a wax material. The first sintered body and the second sintered body can be obtained, for example, by cutting a cylindrical sintered body. Alternatively, a method may be used of preparing a first molded body having a bottomed cylindrical shape (concave in side cross section) and a second molded body having a cylindrical upper part and an inverted truncated cone lower part, and joining them using a slurry-like paste containing the same material as these, and sintering them.

As described above, the heater according to the embodiment (heaters 2, 2A to 2E, for example) has a base (base 10, 10A to 10E, for example), a resistive heating element (resistive heating element 30, for example), and a cavity (cavity 50, 50A to 50E, for example). The base is made of ceramics and has a heating surface (upper surface 101, for example). The resistive heating element is located inside the base. At least a portion of the cavity is located inside the base between the resistive heating element and the side surface of the base. In addition, the cavity is a virtual line extending from the outer circumferential end of the resistive heating element (outer circumferential end 31, for example) in a cross-sectional view of the base in a direction perpendicular to the heating surface, and extends along a second virtual line (second virtual line L2, for example) that is inclined outward from the base from a first virtual line (first virtual line L1, for example) that extends perpendicularly from the outer circumferential end of the resistive heating element toward the heating surface.

Therefore, the heater according to the embodiment can improve thermal efficiency.

Further advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Thus, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

1: heater system 2: heaters 5a, 5b: power supply unit 6: control unit 10: base 20: shaft 30: resistance heating element 31: outer periphery 40: electrode layer 41: terminals 45a, 45b: power supply line 50: cavity 51: first cavity 52: second cavity 55: gap 101: upper surface 102: lower surface 103: side surface 104: outer edge 105: wall L0: central axis L1: first imaginary line L2: second imaginary line L3: third imaginary line W: wafer

Claims (9)

A base body made of ceramics and having an upper surface which is a heating surface and a lower surface which is a surface opposite to the upper surface;
A resistive heating element located inside the base;
a cavity portion, at least a part of which is located inside the base between the resistance heating element and a side surface of the base,
the hollow portion has an outer wall surface located on the side surface side in a cross-sectional view of the base in a direction perpendicular to the top surface, and an inner wall surface opposed to the outer wall surface,
A heater, wherein at least a portion of the inner wall surface becomes more distant from a central axis of the base in a direction perpendicular to the upper surface as it moves from the lower surface to the upper surface. The heater of claim 1, wherein, in the cross-sectional view, the inner wall surface is located in an area defined by a first imaginary line that is perpendicular to the upper surface and passes through the outer peripheral end of the resistance heating element, a second imaginary line that extends from the outer peripheral end and is inclined more toward the outside of the base than the first imaginary line, the side surface, and the lower surface. The heater of claim 2, wherein the second imaginary line extends from the outer peripheral end toward the outer edge of the upper surface. A heater as described in claim 2 or 3, wherein the cavity, in the cross-sectional view, intersects with a third imaginary line extending horizontally from the outer peripheral end toward the side surface. A heater as described in claim 4, wherein the cavity extends along the second imaginary line and the third imaginary line in the cross-sectional view. The heater according to claim 5, wherein the cavity has a wall portion, in the cross-sectional view, a first end of the two ends of which is located on the bottom surface of the cavity and a second end of the two ends of which is located on the ceiling surface of the cavity. A heater as described in claim 5, wherein the cavity has a plurality of spaces arranged in a lattice pattern when viewed in cross section. A heater as described in claim 7, wherein the base has a gap between two adjacent spaces in the cross-sectional view that is shorter in height than the spaces. The cavity is
a first cavity portion located between the resistive heating element and the side surface;
a second cavity portion located between the lower surface of the base and the resistance heating element,
9. The heater according to claim 1, wherein the first cavity and the second cavity are connected to each other.

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