Patent Application
20210235548
The present invention relates to a ceramic heater.
For a semiconductor-manufacturing apparatus, a ceramic heater that heats a wafer is used. A so-called two-zone heater is known as such a ceramic heater. In a heater known as this kind of two-zone heater, as disclosed in PTL 1, an inner-peripheral resistance heating element and an outer-peripheral resistance heating element are embedded in a ceramic base on the same plane, and heat generated from the resistance heating elements is separately controlled by separately applying a voltage to the resistance heating elements. Each resistance heating element is a coil composed of high-melting-point metal such as tungsten.
PTL 1: Japanese Patent No. 3897563 B
According to PTL 1, however, the resistance heating elements are the coils, and accordingly, the adjacent coils need to be spaced from each other so as not to short-circuit. The ceramic heater has a gas hole and a lift pin hole that extend through a ceramic plate in the vertical direction, and the resistance heating elements need to detour around the holes. For this reason, there is a problem in that sufficient thermal uniformity cannot be achieved.
The present invention has been accomplished to solve the problems, and it is a main object of the present invention to achieve sufficient thermal uniformity even in the case where a coil is used as a main resistance heating element.
A ceramic heater according to the present invention includes
a ceramic plate that has a wafer placement surface;
a main resistance heating element that is disposed parallel with the wafer placement surface in the ceramic plate, that is wired from one of a pair of main terminals in a one-stroke pattern, that reaches the other of the pair of main terminals, and that has a coil shape; and
a sub resistance heating element that is disposed in the ceramic plate, that complements heating with the main resistance heating element, and that has a two-dimensional shape.
In the ceramic heater, the main resistance heating element that is disposed in the ceramic plate and that has a coil shape heats a wafer that is placed on the wafer placement surface. The main resistance heating element is a coil and is accordingly restricted when wired. For this reason, just heating with the main resistance heating element is likely to create a point at which temperature singularly decreases, that is, temperature singularity. According to the present invention, the sub resistance heating element that heats the temperature singularity and that has a two-dimensional shape is disposed in the ceramic plate. The sub resistance heating element has a two-dimensional shape and can be accordingly manufactured by printing, and this achieves wiring with a high degree of freedom (for example, a line distance is decreased for wiring at a high density). For this reason, the sub resistance heating element can complement heating with the main resistance heating element that has a coil shape. Accordingly, sufficient thermal uniformity can be achieved even in the case where the coil is used as the main resistance heating element.
The main resistance heating element and the sub resistance heating element may be composed of the same material or composed of different materials. The word “parallel” includes not only a case of being completely parallel but also a case of being substantially parallel (for example, a case of being within tolerance). The sub resistance heating element may be disposed on the same plane as the main resistance heating element or a different plane therefrom. The word “same” includes not only a case of being completely the same but also a case of being substantially the same (for example, a case of being within tolerance).
In the ceramic heater according to the present invention, the ceramic plate may have a hole that extends therethrough in a vertical direction, and the sub resistance heating element may be disposed around the hole. The main resistance heating element is wired so as to detour around the hole that extends through the ceramic plate in the vertical direction. For this reason, a portion around the hole is likely to have the temperature singularity. The sub resistance heating element is disposed around the hole here, and the portion around the hole can be prevented from having the temperature singularity.
In the ceramic heater according to the present invention, the main resistance heating element may extend from the one of the pair of main terminals, may be folded at folded portions, and may reach the other of the pair of main terminals, and the sub resistance heating element may be disposed at a portion at which the folded portions of the main resistance heating element face each other. There is no main resistance heating element at the portion at which the folded portions of the main resistance heating element face each other, and the portion is likely to have the temperature singularity. The sub resistance heating element is disposed at the portion here, and accordingly, the portion can be prevented from having the temperature singularity.
In the ceramic heater according to the present invention, the sub resistance heating element may be disposed in a space between parts of a wiring line of the main resistance heating element. The space between the parts of the wiring line of the main resistance heating element is relatively wide in view of insulation and is accordingly likely to have the temperature singularity. The sub resistance heating element is disposed in the space here, and accordingly, the space can be prevented from having the temperature singularity.
In the ceramic heater according to the present invention, the sub resistance heating element may form a parallel circuit together with the main resistance heating element. In this case, it is not necessary for the sub resistance heating element to include an exclusive terminal.
In the ceramic heater according to the present invention, the sub resistance heating element may be wired from one of a pair of sub terminals in a one-stroke pattern and reaches the other of the pair of sub terminals. This enables heating with the main resistance heating element and heating with the sub resistance heating element to be separately controlled.
In the ceramic heater according to the present invention, the sub resistance heating element may contain ceramics. With the ceramics contained, the thermal expansion coefficient of the sub resistance heating element can be close to the thermal expansion coefficient of the ceramic plate, and bonding strength between the sub resistance heating element and the ceramic plate can be increased.
In the ceramic heater according to the present invention, the sub resistance heating element may be disposed so as to bridge a curved portion of the main resistance heating element, and a coil winding pitch of the curved portion may be less than a coil winding pitch outside the curved portion. In this case, the coil winding pitch of the curved portion is less than the coil winding pitch outside the curved portion, and accordingly, the amount of heat generation of the curved portion increases. For this reason, the amount of heat generation of the curved portion can be inhibited from decreasing as a result of the curved portion and the sub resistance heating element arranged in parallel.
A preferred embodiment of the present invention will hereinafter be described with reference to the drawings.
The ceramic heater 10 is used to heat a wafer that is subjected to a process such as etching or CVD and is installed in a vacuum chamber not illustrated. The ceramic heater 10 includes the ceramic plate 20 that has the wafer placement surface 20a and that is discoid, and a tubular shaft 40 that is joined coaxially with the ceramic plate 20 to a surface (a back surface) 20b of the ceramic plate 20 opposite the wafer placement surface 20a.
The ceramic plate 20 is a discoid plate composed of a ceramic material, representatively, aluminum nitride or alumina. The diameter of the ceramic plate 20 is, for example, about 300 mm. Fine irregularities are formed on the wafer placement surface 20a of the ceramic plate 20 by an embossing process, although these are not illustrated. An imaginary boundary 20c (see
As illustrated in
As illustrated in
As illustrated in
The tubular shaft 40 is composed of ceramics such as aluminum nitride or alumina as in the ceramic plate 20. The inner diameter of the tubular shaft 40 is, for example, about 40 mm, and the outer diameter thereof is, for example, about 60 mm. The upper end of the tubular shaft 40 is diffusion-joined to the ceramic plate 20. Power supply rods 42a and 42b that are connected to the respective a pair of main terminals 22a and 22b of the inner-peripheral main resistance heating element 22 and power supply rods 44a and 44b that are connected to the respective a pair of terminals 24a and 24b of the outer-peripheral main resistance heating element 24 are disposed in the tubular shaft 40. The power supply rods 42a and 42b are connected to a first power supply 32, and the power supply rods 44a and 44b are connected to a second power supply 34. This achieves separate temperature control of the inner-peripheral zone Z1 that is heated by the inner-peripheral main resistance heating element 22 and the inner-peripheral sub resistance heating elements 23 connected thereto in parallel and the outer-peripheral zone Z2 that is heated by the outer-peripheral main resistance heating element 24 and the outer-peripheral sub resistance heating elements 25 connected thereto in parallel. Gas supply pipes through which gas is supplied to the gas holes 26 and the lift pins that are inserted in the lift pin holes 28 are also disposed in the tubular shaft 40 although these are not illustrated.
An example of the use of the ceramic heater 10 will now be described. The ceramic heater 10 is first installed in the vacuum chamber not illustrated, and the wafer W is placed on the wafer placement surface 20a of the ceramic heater 10. The first power supply 32 adjusts power that is supplied to the inner-peripheral main resistance heating element 22 and the inner-peripheral sub resistance heating elements 23 such that the temperature of the inner-peripheral zone Z1 that is detected by an inner-peripheral thermocouple not illustrated becomes a predetermined inner-peripheral target temperature. In addition to this, the second power supply 34 adjusts power that is supplied to the outer-peripheral main resistance heating element 24 and the outer-peripheral sub resistance heating elements 25 such that the temperature of the outer-peripheral zone Z2 that is detected by an outer-peripheral thermocouple not illustrated becomes a predetermined outer-peripheral target temperature. Consequently, the temperature of the wafer W is controlled so as to be the desired temperature. Settings are adjusted such that the interior of the vacuum chamber becomes a vacuum atmosphere or a decompression atmosphere, plasma is produced in the vacuum chamber, a CVD film is formed on the wafer W by using the plasma, and etching is performed.
As for the ceramic heater 10 according to the present embodiment described above, the sub resistance heating elements 23 and 25 have a ribbon shape and can be accordingly manufactured by printing, a line width and a line distance can be decreased, and the degree of freedom of wiring can be increased. For this reason, the sub resistance heating elements 23 and 25 can complement heating with the main resistance heating elements 22 and 24 that have a coil shape. Accordingly, sufficient thermal uniformity can be achieved even in the case where the coils are used as the main resistance heating elements 22 and 24.
The main resistance heating elements 22 and 24 are the coils and are accordingly restricted when wired. For example, the main resistance heating elements 22 and 24 need to be wired so as to detour around the gas holes 26 and the lift pin holes 28. For this reason, portions around the holes 26 and 28 are likely to have the temperature singularity. Since the sub resistance heating elements 23 and 25 are disposed around the holes 26 and 28 here, the portions around the holes 26 and 28 can be prevented from having the temperature singularity.
The inner-peripheral sub resistance heating elements 23 form the parallel circuits together with the inner-peripheral main resistance heating element 22, and the outer-peripheral sub resistance heating elements 25 form the parallel circuits together with the outer-peripheral main resistance heating element 24. For this reason, it is not necessary for the sub resistance heating elements 23 and 25 to include exclusive terminals.
It should be noted that the present invention is not limited to the above-described embodiment at all, and it is needless to say that the present invention can be implemented in various embodiments without departing from the technical scope of the present invention.
For example, a ceramic plate 120 illustrated in
In
As for the ceramic plate 120, as illustrated in
In
The sub resistance heating elements 23 and 25 according to the embodiment described above, the sub resistance heating element 123 in
A ceramic plate 220 illustrated in
In
As for the ceramic plate 220, as illustrated in
According to the embodiment described above, the sub resistance heating elements 23 and 25 are the ribbons but are not particularly limited thereto, and any shape may be used provided that the shape is a two-dimensional shape. The two-dimensional shape enables manufacturing to be performed by applying paste by printing. Accordingly, the sub resistance heating elements 23 and 25 can be readily thinned and can be wired at a high density.
According to the embodiment described above, the ceramic plate 20 may contain an electrostatic electrode. In this case, the wafer W can be electrostatically sucked and held on the wafer placement surface 20a by applying a voltage to the electrostatic electrode after the wafer W is placed on the wafer placement surface 20a. The ceramic plate 20 may contain a RF electrode. In this case, a shower head, not illustrated, is disposed with a space created above the wafer placement surface 20a, and high-frequency power is supplied between parallel flat plate electrodes including the shower head and the RF electrode. In this way, plasma is produced, a CVD film can be formed on the wafer W by using the plasma, and etching can be performed. The electrostatic electrode may double as the RF electrode. The same is true for the ceramic plates 120 and 220 in
According to the embodiment described above, the outer-peripheral zone Z2 is described as a single zone but may be divided into multiple small zones. In this case, the resistance heating elements are separately wired for every small zone. Each small zone may be formed into an annular shape by dividing the outer-peripheral zone Z2 by a boundary line concentric with the ceramic plate 20 or may be formed into a sectorial shape (a shape obtained by unfolding the side surface of a truncated cone) by dividing the outer-peripheral zone Z2 by lines radially extending from the center of the ceramic plate 20.
According to the embodiment described above, the inner-peripheral zone Z1 is described as a single zone but may be divided into multiple small zones. In this case, the resistance heating elements are separately wired for every small zone. Each small zone may be formed into an annular shape and a circular shape by dividing the inner-peripheral zone Z1 by a boundary line concentric with the ceramic plate 20 or may be formed into a sectorial shape (a shape obtained by unfolding the side surface of a cone) by dividing the inner-peripheral zone Z1 by lines radially extending from the center of the ceramic plate 20.
This application claims the priority of Japanese Patent Application No. 2019-011300, filed on Jan. 25, 2019, the entire contents of which are incorporated herein by reference in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-011300 | Jan 2019 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2019/050764 | Dec 2019 | US |
| Child | 17301773 | US |
