Electric heating – Heating devices – With heating unit structure
Reexamination Certificate
1999-11-30
2001-03-20
Jeffery, John A. (Department: 3742)
Electric heating
Heating devices
With heating unit structure
C219S444100, C219S458100
Reexamination Certificate
active
06204488
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a sealing terminal and more particularly to a sealing terminal used for a heater having a heating element sealed in a quartz member.
In a process of semiconductor manufacturing, a silicon wafer or the like is subjected to various heat treatments.
Such heat treatments require not only strict temperature control but also a clean atmosphere which is free from particles including fine dusts.
For this purpose, the heater for such heat treatments is required to show uniform heating performance and superior temperature rising and decreasing control capabilities as well as non-emission of polluting matters such as particles.
As one example of the heater for manufacturing semiconductors, there is known a type in which a heating element is sealed in a support member of quartz glass or the like together with a non-oxidizing gas.
The inventors once developed a superior heater for subjecting semiconductors to heat treatments; that is, fine carbon mono filaments bound into a plurality of carbon fiber bundles, which are woven into a carbon wire heating element which in turn is sealed in a quartz glass support member together with a non-oxidizing gas. Said heater is already proposed in Japanese Patent Application H10-254513.
Said carbon wire heating element has such a smaller heat capacity than metallic counterparts that it shows less temperature fluctuation as well as an excellent high temperature resistance in a non-oxidizing atmosphere.
Moreover, since a plurality of fine carbon mono filaments are woven in the manufacture of said carbon wire heating element, it has a remarkable flexibility as compared with a heating element of solid carbon member such that it has an advantage in term of structural variety and workability.
Therefore, said heating element sealed in a heat resistant clean support member of high purity quartz glass or the like together with a non-oxidizing gas will not produce particles and is most suitable as a heater for the semi-conductor manufacturing as stated in the foregoing.
In this connection, the heater which uses the carbon wire element as a heating element requires a terminal device for connection between terminal wires composed of carbon heater bundles and metal wires. The inventors proposed some terminal devices in the above mentioned earlier application.
With reference to
FIGS. 7 and 8
, the outline of such heaters and terminal devices proposed in said earlier application will be explained.
A carbon heater
50
has substantially an integral structure prepared by sealing a pair of heater members
51
(carbon wire heating element) in a plate-like quartz glass support member
52
.
Although not shown, said plate-like quartz glass support member
52
is formed with spaces within which heater elements
51
are accommodated.
Said heater element
51
is in contact with said spaces by way of the carbon fibers having a fluffed surface.
Further, the heater element
51
has its end substantially drawn perpendicularly to a heater face
52
a
and is connected to a molybdenum (Mo) terminal line
54
by way of a carbon terminal
53
and a connector
58
.
Further, said molybdenum (Mo) terminal line
54
is connected to a pair of molybdenum (Mo) terminal line
57
for outside connection by way of a plate-shaped molybdenum (Mo) foil
56
.
In this connection, the molybdenum (Mo) foil
56
is pinch sealed by a quartz glass tube
55
together with the respective ends of said molybdenum terminal lines
54
and a pair of such external connection lines
57
.
Further, said members are arranged in a glass tube
55
to constitute a sealing terminal.
Now then, said sealing terminal is required to have less electrical resistance to prevent sparks from being generated such that it is possible to supply power to the carbon heating element.
Said terminal structure will suffice the above requirements.
However, said sealing terminal is structured in such a way that the carbon terminal
53
is connected to the molybdenum (Mo) terminal line
54
and the external connection lines
57
by way of the connectors
58
to make the structure complicated and assembly thereof difficult.
Further, a compact sealing terminal is desired considering various devices to be arranged around near the heater.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above mentioned-technical problems and its objective is to provide a compact and easy-to-assemble sealing terminal which has less electrical resistance to prevent sparks from being generated such that it is possible to supply power to the carbon heating element.
To realize the above objective, the sealed terminal according to the present invention is essentially characterized in comprising heating elements; internal connection lines to be electrically connected to said heating elements; external connection lines from which power is supplied; a glass body formed with a plurality of grooves in outer surfaces thereof to retain said internal and external connection lines therein; conductive foils to electrically connect said internal and external connection lines; a glass tube to accommodate therein said internal and external connection lines with end portions thereof projecting out of said glass tube, said glass tube being fused to said glass body at outer surfaces thereof; and a plug member to close said glass tube at an end thereof at least on the external connection line side.
It is preferable that said glass body and said glass tube are formed of quartz glass.
It is further preferable that said internal and external connection lines include two pairs of internal connection lines and external connection lines and that said internal and external connection lines include members made of either molybdenum or tungsten. In this case, it is even more preferable that the thickness of said molybdenum foils is 20 to 40 &mgr;m. The reason therefor is that the electrical resistance of less than 20 &mgr;m is too high and there is a likelihood of overheat to destroy the glass tube as a result of oxidization and expansion of the molybdenum foil. On the other hand, the electrical resistance of more than 40 &mgr;m causes the sealing performance between the glass body and the glass tube to be degraded and there is a likelihood of an air leaking to oxidize the molybdenum (Mo) terminal foil and the wire carbon terminal. Further, it is preferable that the plug member is made of a cement formed primarily of pulverized alumina cement material. Specifically, pulverized alumina is added to water which is dried until it is set.
It is further preferable that a heat resistant resin coated layer is formed between said glass body and said plug member, that said internal connection lines are provided at ends thereof with a retaining member made from opaque glass or foamed glass, where said retaining member is used to retain said internal connection lines in said glass tube, and that said opaque glass and said foamed glass are formed of quartz glass.
It is further preferable that said heating element is prepared by binding carbon fibers each having a diameter of 5 to 15 &mgr;m into a plurality of bundles and weaving said plurality of bundles into knitted cords, braids or the like.
It is further preferable that said carbon fibers contain less than 10 ppm of ash contents as impurities.
The sealing terminal of the invention is characterized in that the glass body is formed with grooves in outer surface thereof to retain the internal and external connection lines and that there are provided conductive foils to electrically connect said internal and external connection lines such that the glass body is accommodated within the glass tube.
Thus constructed, downsizing is realized more efficiently than the conventional flat molybdenum foils.
Moreover, the need for connectors is eliminated and mere insertion of the internal connection lines into terminal lines completes the work of electrical connection to simplify the operation.
REFERENCES:
patent: 5231690 (1993-07-01), Soma et al.
patent: 5753891 (1998-05-01), Iwa
Konn Tomio
Makiya Toshiyuki
Nagata Tomohiro
Nakao Ken
Osanai Hisaei
Foley & Lardner
Jeffery John A.
Toshiba Ceramics Co., Ltd
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