Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-11-29
2002-05-21
Paik, Sang (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
Reexamination Certificate
active
06392205
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disc heater incorporated in a temperature control apparatus which alternately repeats heating and cooling operations in a manufacturing process of semiconductor or in a forming process of various thin films or electrode pattern with respect to glass plate of liquid crystal display, and also relates to a temperature control apparatus provided with the heater. More particularly, the present invention relates to a disc heater in which a wire-like heating element is disposed in one stroke drawing manner onto a plate surface, thereby securing thermal uniformity in a heating surface of the disc heater, and a number of excessively heated local portions is reduced. The present invention also relates to a temperature control apparatus provided with the heater.
2. Description of the Related Art
A disc heater of this kind can be applied to various processing apparatus used in film forming process of manufacture of semiconductors, etching process, photoresist application process, or light exposure process in manufacturing of crystal displays. As disclosed in Japanese Patent Laid-open Publication No. 7-183281 for example, the disc heater of this kind is used for smooth cooling control.
The disc heater disclosed in the above-described publication is a temperature adjusting heater used for controlling cooling temperature at the time of cooling process of semiconductor wafers. In a conventional low temperature processing apparatus to which this temperature adjusting heater is applied, since an electricity feeding pipe used for feeding high frequency electricity or feeding electricity to the heater is disposed in a center of a table on which an object to be processed is placed, cold temperature from a cooling jacket is less prone to be transmitted to the center region of the table. Further, since the heat from the heater is actively transmitted around a periphery of the table and thus, even when the heater is designed such that the calorific value from a heating surface of the heater becomes uniform, the entire heating surface of the heater is not heated uniformly. Therefore, there is a tendency that the center of the heater is higher in temperature than peripheral region. Thus, topology of a wire heating body of the temperature adjusting heater is set rough at a center thereof as compared with a peripheral region thereof, thereby preventing the center from being excessively heated and securing uniform temperature over the entire heating surface.
However, in a temperature control apparatus that the present inventor previously proposed in Japanese Patent Application No. 10-40765, the electricity feeding pipe as described above is not necessarily disposed in the center of the table intensively. In this case, it is preferable that an entire heating surface of the disc heater of this kind is heated uniformly.
On the other hand, in the conventional disc heater as disclosed in Japanese Patent Laid-open Publications Nos. 5-21308 and 7-183281 for example, a thick metal plate having great thermal capacity is interposed between a heating body and an object to be processed. By interposing the metal plate in such a manner, it is possible to uniformly transmit heat from the heating body to the object to be processed through the metal plate, so that it is unnecessary to pay special attention to the topology pattern of the heating body.
However, in a case of a processing apparatus which alternately repeats heating and cooling operations with respect to the object to be processed, it is preferable that after the object is heated for a predetermined time period by swiftly increasing the temperature to a preset processing temperature, the temperature is swiftly lowered to a preset cooling temperature, as shown in FIG.
16
. As described above, when the thick metal plate having great thermal capacity is interposed between the heating body and the object to be processed, the thermal transmission is prone to be delayed and its control is difficult. To avoid such problems, it is ideal to bring the heating body into direct contact with the object to be processed and to heat and cool it.
Actually, the heating body is not brought into direct contact with the object to be processed, considering influence on the object to be processed, so that a surface of the heating body is covered with a metal foil which is extremely thin and has high thermal conductivity, such as aluminum foil of 0.5 mm. However, when the heating body is covered with the metal foil having great thermal conductivity, since the object to be processed is largely influenced by the topology pattern of the heating body, higher uniformity of heat of the heating body is required. Therefore, the topology pattern of the heating body becomes important.
FIGS. 17
to
19
show an example of commercially available topology pattern of a wire heating body designed so as to obtain uniform calorific value, and its locally excessively heated state. As can be understood from these drawings, in the topology pattern formed by a wire-like heating element
40
, in a region of a disc heater whose center diameter is about ½ of the disc heater, adjacent straight lines of a large number of straight line portions
40
b
comprising parallel strings divided into ½ are sequentially connected by arc portions
40
a
or short straight line portions
40
′
b
so that the entire pattern has continuous repeating zigzag shapes. A peripheral region of the center region is divided into two regions in a diametrical direction of the disc heater. In a region closer to the center, each diametrically adjacent pair of ends of a large number of concentrically disposed-long and short various arc portions
40
a
are connected by the straight line portions
40
′
b
, while in a region closer to the outer periphery, each pair of diametrically adjacent ends of the arc portions
40
a
on an extensions in a diametrical direction of the connected portions of the ends in the above-described center region are connected by the straight line portions
40
′
b
. Such a complicated topology pattern has been invented for securing thermal uniformity of the heating surface to the utmost.
In
FIGS. 19A and 19B
, blackened portions indicate burnt portions
40
c
by heat. It can be understood from distribution of the burnt portions
40
c
that the burnt portions are concentrated on bent portions of the wire-like heating elements, and many burnt portions
40
c
exist in portions where closed regions between adjacent wire-like heating elements in which heat is less prone to be released. This is caused because heating current is shortcut in the bent portions and concentrated in inner side of the bent portions. Due to the existence of the burnt portions
40
c
, the calorific value concentrates in such portions so that the calorific value there is remarkably increased as compared with the other portions, and the object to be processed is locally heated excessively. Further, when the excessively heating state continues, such portions are burnt to cut down wires, so that the heater can not function as a heater.
If the topology pattern is studied in detail, wire-like heating elements disposed in the outermost peripheral region are wider and a distance between the adjacent wires is narrower than the wire-like heating elements in other regions. This is because the heating density of the center of the heater is made rough so that excessive heating in the center can be avoided and the object to be processed can be processed with uniform heat, as in the temperature adjusting heater disclosed in Japanese Patent Laid-open Publication No. 7-183281. However, as described above, according to the latest processing apparatus, high frequency electricity is not always supplied to the center of the heater, or a feeding pipe used for feeding electricity to the heater or static electricity chuck is not always disposed in the center of the heater. Further, when the object to be processed is directly heated, it is required th
Bell Boyd & Lloyd LLC
Komatsu Limited
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