Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-06-08
2001-06-05
Paik, Sang (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S541000
Reexamination Certificate
active
06242719
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ceramic heater, in particular, a multiple-layered ceramic heater that is used in a temperature increasing and decreasing step of semiconductor fabrication process.
2. Description of Related Art
As a heater used in a semiconductor fabrication process, there has conventionally been used one comprising a support substrate composed of a sintered ceramic such as alumina, aluminum nitride, zirconia or boron nitride, which is wound or adhered with a wire or foil of high melting point metal such as molybdenum or tungsten as a heat generating body, and an insulating ceramic plate placed thereon. Further, as an improved version of such a heater with improved insulating property and anticorrosion property, there has been developed a ceramic heater comprising an electrical insulating support substrate, a heater pattern composed of electroconductive ceramic, which is adhered to a surface of the substrate as a heat generating layer, and an electrical insulating ceramic protective layer covering the heater pattern.
On the other hand, wafers of increasingly large diameter are being used in the production of semiconductor devices, and the diameter of mainstream silicon wafers is currently 200 mm, and is expected to reach 300 mm by the year 2010. When the diameter becomes larger, it becomes difficult to ensure production performance, such as process uniformity, by a conventional apparatus for batch processing, and it is expected that processes replaced by a single wafer processing process where wafers are treated one by one will increase to solve the foregoing problem.
As a heat source of the aforementioned single wafer processing treatment, ceramic heaters are seen as having great potential because they consume little electric power and exhibit excellent stability, and adaptation to a larger diameter and improvement of performance thereof have been attempted in parallel. Further, because wafer temperature greatly affects the properties of thin films formed on the wafers and film forming rate, with use of a larger diameter of wafers, how to control thermal uniformity over a larger surface of the wafers becomes an important issue.
On the other hand, as for the ceramic heater, which is a heat source, a multiple-layered ceramic heater
1
(occasionally referred to as simply “heater” hereinafter) comprises, as shown in
FIG. 7
for example, a support substrate
2
, heat generating layer
3
, and protective layer
4
, and feeding terminals
5
are connected to power terminal members
10
usually each comprising a bolt
7
and feeding support shaft
9
. When the heater is supplied with electric current to generate heat, the power terminal members
10
act as a heat radiator to radiate the heat. Therefore, the temperature around the feeding terminals
5
of the heater decreases, and the temperature of portions of a wafer W facing the feeding terminals
5
also decreases. Accordingly, the thermal uniformity of the wafer as a whole is degraded. If the wafer in this state is heat-treated or subjected to film forming thereon, characteristics or properties of the film on the portions of reduced temperature would be different from those of the other portions. This degrades quality parameters, reduces productivity in the device production, and constitutes one of the causes of reduced yield.
While it is considerable to solve the aforementioned problem by disposing the feeding terminals at positions not facing the wafer to be heated, the wafer would still be affected by the portions of reduced temperature unless the feeding terminals were separated from the periphery of the wafer by a substantial distance. This would lead to a substantially larger size of the heater compared with the object to be heated, and therefore the apparatus as a whole would have to be made larger. This would be a cause of increased equipment cost and heater production cost.
SUMMARY OF THE INVENTION
The present invention has been accomplished in order to overcome the aforementioned problems, and its major object is to provide a multiple-layered ceramic heater excellent in thermal uniformity, whose ability to uniformly heat an object to be heated is not adversely affected by feeding terminals of the heater even when the terminals are present at positions facing the object to be heated.
In order to achieve the foregoing object, the present invention provides an integrated type multiple-layered ceramic heater based on resistance heating comprising an electrical insulating ceramic support substrate, a heater pattern composed of electroconductive ceramic or metal, which is adhered to a surface of the substrate, and an electrical insulating ceramic protective layer covering the heater pattern, characterized in that feeding terminals of the heater are connected to power source terminal members through feeding members which generate heat when supplied with electric current.
According to the aforementioned structure, heat generated in the vicinity of each feeding terminal of the multiple-layered ceramic heater is not substantially conducted to the power terminal member through the feeding member and is not radiated therefrom. Therefore, an object to be heated placed over the upper surface of the heater, for example, the whole surface of a semiconductor wafer, is substantially uniformly heated, and its thermal uniformity is maintained. Accordingly, heat treatment of the wafer or film forming thereon can substantially uniformly performed over the entire surface of the wafer, and thus productivity and yield in the device production process can be improved.
In the aforementioned ceramic heater, the feeding member preferably generates heat at a power density substantially equal to that of the heater.
By that, the calorific power of the feeding member and the calorific power of the heater become substantially the same, and thus heat conduction from the feeding terminal portion of the heater to the power terminal member through the feeding member is substantially completely eliminated. Therefore, the temperature around the feeding terminal is not decreased, and it becomes possible to substantially uniformly heat the whole surface of an object to be heated.
In the aforementioned ceramic heater, the support substrate and the protective layer of the heater, and the support substrate and the protective layer of the feeding member are preferably composed of AlN, BN, a complex of AlN and BN, PBN or SiO
2
, and the heater pattern of the heater and the feeding members is preferably composed of carbon, high melting point metal, high melting point metal alloy, noble metal or noble metal alloy.
When the heater and the feeding members are constituted of materials selected from the particular materials mentioned above, characteristics required for the support substrate, the protective layer and the heater pattern can be sufficiently satisfied, and production and processing of the members become easy. At the same time, a long-life multiple-layered ceramic heater excellent in mechanical strength, heat resistance, and anticorrosion property can be obtained.
In the ceramic heater of the present invention, the support substrate, the protective layer, and the heater pattern constituting the heater and the feeding members are preferably formed by chemical vapor deposition.
If the heater and the feeding members are formed by chemical vapor deposition as described above, the heater pattern can be made in an arbitrary shape, and a member having a power density of desired value can easily be produced. As a result, a multiple-layered ceramic heater exhibiting excellent thermal uniformity, i.e., capable of uniformly heating the whole surface of an object to be heated can be produced.
As another aspect of the present invention, the present invention also provides a feeding member for connecting a feeding terminal and a power terminal member of a multiple-layered ceramic heater, characterized in that it comprises an electrical insulating ceramic support substrate, a heater pattern composed o
Ito Kenji
Iwai Ryouji
Kano Shoji
Hogan & Hartson L.L.P.
Paik Sang
Shin-Etsu Handotai & Co., Ltd.
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