This application claims the benefits of Japanese Patent Application P2004-1725 filed on Jan. 7, 2004, the entirety of which is incorporated by reference.
1. Field of the Invention
The invention relates to a heating resistance and heater suitable to, for example, for heating semiconductors, whose temperature distribution can be easily controlled.
2. Related Art Statement
In semiconductor producing systems, ceramic heaters have been applied for heating a wafer so as to deposit a semiconductor thin film on the wafer from gaseous raw materials such as silane gas by means of thermal CVD or the like. In such ceramic heaters, it is required to make the temperature of the heating face and the semiconductor wafer mounted thereon uniform at a high precision.
Several techniques for reducing the temperature distribution on the heating (mounting) face of the ceramic heater are known. For example, a so-called two-zone heater is such a heater. Such a two-zone heater has a ceramic substrate and inner and outer resistance heat generators embedded in the substrate. Separate power supply terminals are connected to the respective heat generators so that electric power may be applied independently to the respective heat generators. Heat generated from the inner and outer heat generators may thus be independently controlled.
Two-zone heaters include the following types. Japanese patent publication 2001-102157A discloses a heater having a ceramic substrate and two layers of heating elements embedded in the substrate. The calorific values in the inner zone and outer zone of each heating element are controlled so that a two-zone control system of inner and outer zones is realized.
It is desired to provide a design for adjusting the heat generation density from a heating resistance embedded in a ceramic heater, depending on the actual environmental conditions where the heater is set. For example, when a heating resistance (wound body) having a coil spring shape is embedded in a ceramic substrate, the heat generation density per unit area can be raised by increasing the winding number or winding diameter (coil diameter) or by reducing the wire diameter. Further, the heat generation density per unit area can be lowered by reducing the winding number or winding diameter (coil diameter) or by increasing the wire diameter.
Normally, the material of a heating resistance embedded in a ceramic substrate should be a high melting point metal which does not melt or easily deform at the sintering temperature of ceramics, and thus is limited. For example, when a wound body of molybdenum wire or tungsten wire is used, it is difficult to change the winding diameter or wire diameter in a single wound body due to the limitations of the manufacturing process. It is thus necessary that a plurality of wound bodies having the different winding diameters, winding numbers or wire diameters are joined and electrically connected with each other before the connected wound bodies are embedded in a ceramic substrate.
According to Japanese Patent publication 2003-272, 805A, for example, when a heating resistance composed of a tungsten coil is embedded in a ceramic substrate, two kinds of heating resistances having different wire diameters and winding diameters are used and are mechanically connected with each other using a spherical connecting terminal. It is thus possible to embed and combine two or more kinds of heating resistances having different wire diameters or winding diameters in a single ceramic substrate so that hot and cold spots on the surface of the substrate can be reduced.
The material of a heating resistance embedded in a ceramic substrate is, for example, a high melting point metal such as tungsten or molybdenum. A wire made of such high melting point metal is hard, brittle, hard to deform and is thus difficult to process. The terminal described above is thus necessary for connecting a plurality of heating resistances having the different wire diameters. However, if the resistance at the connecting part of the heating resistance and the terminal in use is raised, hot spots may be observed on the heating face. Moreover, for assuring excellent mechanical strength and reliability of the connecting parts of the heating resistance and the terminal, the structure, shape and method of connecting the connecting part need to be studied in detail. The manufacturing process required for producing the connecting part may become troublesome.
An object of the present invention is, in a heating resistance, to make the design and change of the heating value per unit length easier, and to improve the reliability and prevent abnormal heat generation at interfaces where the heating value per unit length is changed.
A first aspect of the present invention provides a heating resistance comprising a shaped body of a band made of a conductive material and having a shape of a wave. The first aspect of the present invention further provides a heater comprising a substrate made of an insulating material and the above heating resistance fixed to the substrate.
According to the first aspect, it is necessary that the shaped body has a shape of a wave in a front view as shown in
A second aspect of the present invention provides a heating resistance comprising a wound body of a band of conductive material. The second aspect of the present invention further provides a heater comprising a substrate made of an insulating material and the above heating resistance fixed to the substrate.
These and other objects, features and advantages of the invention will be appreciated upon reading the following description of the invention when taken in conjunction with the attached drawings, with the understanding that some modifications, variations and changes of the same could be made by the skilled person in the art.
b) is a front view showing the heating resistance 1.
a) is a plan view showing a heating resistance 1A according to the first aspect of the present invention.
b) is a front view showing the heating resistance 1A.
a) is a diagram schematically showing the planar pattern of the heating resistance 1 embedded in the substrate 9.
b) is a diagram schematically showing the planar pattern of the heating resistance embedded in the substrate 9.
a) is a plan view showing a heating resistance 1 with a through hole 15 formed therein.
b) is a front view showing the heating resistance 1 of
a) is a diagram showing contour lines of temperature on the surface of the heater.
b) is a diagram showing contour lines of temperature on the surface of the heater.
The advantageous effects of the present invention will be described below referring to
“λ1” represents a length (pitch) of the repetition unit 3, “B1” represents an amplitude of the repetition unit 3, and “W1” represent a width of the band in the repetition unit 3. Further, “λ2” represents a length (pitch) of the repetition unit 4, “B2” represents an amplitude of the repetition unit 4, and “W2” represents a width of the band in the repetition unit 4. According to the present example, the amplitudes “B1” and “B2” are the same and the pitches “λ1” and “λ2” are the same in repetition units 3 and 4. The width “W2” of repetition unit 4 is, however, made larger than the width “W1” of repetition unit 3. The heating value per unit length in repetition unit 4 is smaller than that in repetition unit 3 when power is supplied to the heating resistance 1A in the longitudinal direction.
As can be seen from the examples shown in
For example, a pair of terminals 10 are embedded in a central part of the substrate 9 and are electrically and mechanically connected with respective outer power supply cables (not shown). The heating resistance 1 or 1A having the shape described above is connected to a pair of terminals 10. The heating resistance is positioned according to a predetermined spiral pattern so that the heating resistance surrounds the terminals 10.
For example, as schematically shown in
Depending on the design of the heater, however, it may be necessary to increase the heating value in one part of the heating resistance compared to another part of the heating resistance. In the example shown in
A second aspect of the present invention provides a heating resistance comprising a wound body of a band composed of a conductive material. The second aspect of the present invention further provides a heater comprising a substrate made of an insulating material and the above heating resistance fixed to the substrate.
The advantageous effects will be described referring to
The heating resistance 12 of
In
According to the present example, the pitches λ1 and λ2 of the spiral are the same and the widths “W1” and “W2” of the bands 20A and 20B are the same in the repetition units 13 and 14. The winding diameter “E2” of the repetition unit 14 is, however, made larger than the winding diameter “E1” of the repetition unit 13. The heating value per a unit length of the heating resistance in the repetition unit 14 is made larger than that in the repetition unit 13 when power is supplied to the heating resistance 12A in the longitudinal direction.
Alternatively, the winding diameters and pitches can be made different in the repetition units 13 and 14. In this case, the width “W1” (repetition unit 13) of the band 20A is made larger than the width “W2” (repetition unit 14) of the band 20B. The heating value per a unit length of the heating resistance in the repetition unit 14 is thus made larger than that in the repetition unit 13.
Alternatively, the widths and winding diameters can be made different in the repetition units 13 and 14. In this case, the pitch “λ1” (repetition unit 13) of the band 20A is made larger than the pitch “λ2” (repetition unit 14) of the band 20B. The heating value per a unit length of the heating resistance in the repetition unit 14 is thus made larger than that in the repetition unit 13.
As can be seen from the examples shown in
The planar patterns of the embedded heating resistances 12 and 12A are the same as that shown in
Depending on the design of the heater, however, it may be required that the heating value is made larger in one part of the heating resistance than in another part of the resistance. In the example of
In the first and second aspects of the present invention, the kind of object to be heated is not limited. Further, the application of the heating resistance and heater according to the present invention is not particularly limited, and may preferably a system for producing semiconductors. Such system means a system usable in a wide variety of semiconductor processing in which metal contamination of a semiconductor is to be avoided. Such system includes a film forming, etching, cleaning and testing systems.
The material for the heating resistance is preferably tantalum, tungsten, molybdenum, platinum, rhenium, hafnium or the alloys of these metals. In particular, when the ceramic substrate is made of aluminum nitride, the material of the heating resistance is preferably pure molybdenum or an alloy containing molybdenum. The material of the heating resistance may be a conductive material such as carbon, TiN or TiC, in addition to the high melting point metals described above.
The materials that can be used for the substrate of the heater include a ceramic material or other insulating materials, and are not particularly limited. The material for the substrate may be a known ceramic material including a nitride ceramics such as aluminum nitride, silicon nitride, boron nitride and sialon, and an alumina-silicon carbide composite material. Aluminum nitride or alumina is most preferred for providing an excellent anti-corrosion property against a corrosive gas such as a halogen based corrosive gas.
The shape of the substrate is not particularly limited and may preferably be a disk. Pocket shaped parts, emboss-shaped parts, or grooves may be formed on the heating face.
According to the first and second aspects of the present invention, the thickness of the band is not particularly limited. The thickness is preferably 0.05 mm or larger for preventing the disconnection of the heating resistance. Further, the thickness is preferably 5 mm or smaller from the viewpoint of easily deforming the band to a shape of spiral or bellows.
Further, in the first and second aspects of the present invention, a through hole may be formed in the band. It is possible to control the heating value generated from any part of the heating resistance, by controlling the shape, dimension and number of the through hole. Further, when the wave shaped body or wound body composed of a band having a through holes formed therein is embedded in an insulating substrate, it is possible to improve the adhesion of the insulating material, particularly ceramics, constituting the substrate.
The heater 8 described referring to
Specifically, the substrate 9 was made of aluminum nitride sintered body having a diameter φ of 350 mm and a thickness of 20 mm. The heating resistance 1 shown in
The temperature of the ceramic heater was raised so that the average temperature on the surface 9a reached about 500° C. The temperature distribution on the surface 9a was observed with a thermoviewer.
The heater 8A described referring to
The heating resistance 1A shown in
The temperature of the ceramic heater was raised so that the average temperature on the surface 9a reached about 500° C. The temperature distribution on the surface 9a was observed with a thermoviewer.
The heater 18 described referring to
Specifically, the substrate 9 was made of aluminum nitride sintered body had a diameter φ of 350 mm and a thickness of 20 mm. The heating resistance 12 shown in
The temperature of the ceramic heater was raised so that the average temperature on the surface 9a reached about 500° C. The temperature distribution on the surface 9a was observed with a thermoviewer. The difference of the maximum and minimum temperatures was 8° C. to prove that the temperature uniformity on the surface can be considerably improved.
The heater 18A described referring to
The heating resistance 12A shown in
The temperature of the ceramic heater was raised so that the average temperature on the surface 9a reached about 500° C. The temperature distribution on the surface 9a was observed with a thermoviewer. The difference of the maximum and minimum temperatures was 5° C. to prove that the temperature uniformity on the surface can be considerably improved.
As described above, the present invention provides a heating resistance so that the heating value per a unit length can be easily designed and changed, and the reliability can be improved and abnormal heat generating can be prevented at the interface where the heating value per a unit length is changed.
The present invention has been explained referring to the preferred embodiments. However, the present invention is not limited to the illustrated embodiments which are given by way of examples only, and may be carried out in various modes without departing from the scope of the invention.
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