Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2000-04-27
2002-07-02
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S405000, C219S411000, C392S416000, C118S724000, C118S725000
Reexamination Certificate
active
06414277
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an ultra-high-temperature heat treatment apparatus.
2. Related Art
An ultra-high-temperature heat treatment apparatus having an electric furnace for use in heat treatment of wafers or the like is known. An electric heater of a conventional heat treatment apparatus is comprised of a single one-piece heater element which is installed in a spiral or folded form on the inner wall surface of a heat insulator of the electric furnace, with its heat generating portion directly fixed to the heat insulator. With such a one-piece heater structure, the whole heater element must be replaced even if the heater element is partly damaged, which is costly.
The conventional heat treatment apparatus further includes a water-cooled metal manifold and a furnace tube made of SiC/CVD-SiC and disposed above the metal manifold, the furnace tube being adapted to receive wafers or the like. An O-ring is inserted into a fitting portion between the furnace tube and the metal manifold, so as to prevent intrusion of contaminants from the outside. With this arrangement, however, it is difficult to increase the length of a uniform temperature zone of the furnace tube, and the furnace tube can be subject to a great heat shock.
Although the conventional heat treatment apparatus is configured to prevent the conduction of high temperature heat from the furnace tube, a SiC buffer is solely provided therefor, so that a large amount of heat may be transferred downwardly of the furnace tube, resulting in increased cooling costs to prevent the heat conduction.
Furthermore, the conventional heat treatment apparatus is provided with a flange which is vertically moveable relative to the above-mentioned manifold. To seal between the manifold and the flange, an O-ring is fitted into a tapered groove (generally, a dovetail groove) formed in a flat portion of the flange. However, the O-ring subject to high temperature heat sometimes sticks on the manifold to be detached from the tapered groove of the flange.
The conventional heat treatment apparatus further comprises a separator for loading a wafer into an annular holder and for separating the wafer from the holder. The separator is configured to push the wafer upward to separate the wafer and push the wafer downward to load the same into the holder. However, the work efficiency of the separator is not satisfactory.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ultra-high-temperature heat treatment apparatus including an electric furnace having a heater comprised of heater elements adapted to be replaceable on one-heater-element basis, thereby reducing costs for repair of the heater. Preferably, the heat treatment apparatus can suppress undesired reactions between a heat-generating portion of each heater element and a heat insulator constituting a refractory lining of the electric furnace and suppress a contraction of the heat insulator, thereby providing the electric furnace with a prolonged service life.
Another object of the present invention is to provide an ultra-high-temperature heat treatment apparatus permitting a joining portion between a furnace tube and a manifold to be disposed in a high-temperature environment and providing an increased length of a uniform temperature zone. Preferably, the heat treatment apparatus is arranged to perform evacuation through a slit formed in an upper face of the manifold so as to tightly seal the joining portion and to reduce metal contamination.
A further object of the present invention is to provide an ultra-high-temperature heat treatment apparatus which can reduce heat conduction from a furnace tube by means of a heat insulating apparatus and make it easy to cool a buffer-installed portion of the heat-insulating apparatus at low costs.
A still another object of the present invention is to provide an ultra-high-temperature heat treatment apparatus capable of unremovably holding an O-ring disposed between a manifold and a flange which constitute a contamination control apparatus, thereby positively preventing contamination.
A still another object of the present invention is to provide an ultra-high-temperature heat treatment apparatus capable of easily separating a heat-treatment object, preferably a wafer, from an annular holder for holding the heat-treatment object, thereby improving work efficiency.
According to one aspect of the present invention, there is provided an ultra-high-temperature heat treatment apparatus which comprises an electric furnace including a heater comprised of heater elements which are replaceable independently of each other, each heater element being disposed so as not to be in close contact with an inner wall face of a heat insulator of the electric furnace.
With the heat treatment apparatus of this invention, the heater elements of the heater of the electric furnace can be replaced on one-heater-element basis, thereby extremely reducing costs for fabrication and repair of the heater.
Preferably, each heater element includes a heat-generating portion disposed along the inner wall face of the heat insulator so as not to be in close contact therewith, and a fixture portion fixed to the heat insulator.
With this preferred arrangement, it is possible to suppress undesired reactions between the heat-generating portion of each heater element and the heat insulator as well as a contraction of the heat insulator, thereby permitting the heater elements to perform a stable heat-generating action at high temperatures. In addition, the heat-generating portions of the heater elements are not subject to mechanical constraint and hence deterioration of their durability due to thermal deformation stress is less likely to occur, so that the heater has a prolonged service life.
According to another aspect of the present invention, there is provided an ultra-high-temperature heat treatment apparatus which comprises a furnace tube, which is preferably made of porous SiC/CVD-SiC, and a manifold made of quartz and disposed beneath the furnace tube.
With the ultra-high-temperature heat treatment apparatus of the present invention, the length of a uniform temperature zone of the furnace tube can be increased by the provision of the quartz manifold disposed beneath the furnace tube preferably made of porous SiC/CVD-SiC, and a heat shock applied to the SiC/CVD-SiC furnace tube can be relieved.
Preferably, a slit is formed in an upper face of the quartz manifold at which the quartz manifold is joined to the furnace tube, and the slit is communicated with a vacuum evacuation system.
With this preferred arrangement, intermediate evacuation can be made through the slit formed in a joining face between the furnace tube and the quartz manifold and communicating with a vacuum evacuator system, thereby sealing the joining face. In the case of the Sic/CVD-SiC furnace tube for use with the quartz manifold communicating with the evacuation system, especially, metal contamination can be suppressed.
According to a further aspect of the present invention, there is provided an ultra-high-temperature heat treatment apparatus which comprises a furnace tube preferably made of porous SiC/CVD-SiC and a heat-insulating apparatus fitted into the furnace tube for interrupting heat conduction from the furnace tube. The heat-insulating apparatus includes a SiC buffer and a quartz buffer disposed beneath the SiC buffer.
With the ultra-high-temperature heat treatment apparatus of this invention, downward heat conduction from the furnace tube preferably made of porous SiC/CVD-SiC can be suppressed by the heat-insulating apparatus, and the cooling of a buffer-installed portion of the heat-insulating apparatus can be made with ease at low costs.
According to a further aspect of the present invention, there is provided an ultra-high-temperature heat treatment apparatus which comprises a furnace tube preferably made of porous SiC/CVD-SiC and a contamination control apparatus disposed beneath the furnace tube for preventing contamination in the furna
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