Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
2001-06-11
2003-09-30
Paik, Sang (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S438000
Reexamination Certificate
active
06627859
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an apparatus and method for implementing temperature control on a means for heating.
BACKGROUND ART
Various types of semiconductor manufacturing apparatuses having a heater are used in the process of manufacturing a semiconductor device. For instance, heaters are provided at a process chamber wall, a stage on which a semiconductor wafer (hereafter referred to as a “wafer”) is placed and the like in a thermal CVD (film forming) device. Thus, in the thermal CVD device, film formation processing is implemented after heating the process chamber wall and the stage to a specific temperature with the heaters. In addition, temperature control of the heaters is implemented by a temperature control apparatus. The temperature control apparatus compares the set temperature and the temperature at a heater detected by a thermal (temperature) sensor. Then, the temperature control apparatus implements on/off control of the power supplied to the heater through switching so as to set the two temperatures roughly equal to each other through an adjustment of the quantity of heat generated by the heater. In addition, an interlocking thermal sensor (hereafter referred to as an “interlock sensor”) is connected to the temperature control apparatus. The temperature control apparatus stops power supply to a heater if the temperature of the heater detected by the interlock sensor indicates a level equal to or higher than the temperature upper limit set at the temperature control apparatus.
However, in the prior art described above, it is necessary to provide a thermal sensor and an interlock sensor in correspondence to each heater. For this reason, if there are a plurality of heaters, the number of individual types of sensors and the wirings required to connect the sensors to the temperature control apparatus are bound to increase in correspondence to the number of heaters. As a result, a problem arises in the prior art in that a large initial cost must be incurred since a great number of sensors must be provided.
In addition, there is another problem in the prior art technology in that the maintainability of the apparatus is lowered due to the complex and time-consuming inspection and testing process that must be conducted on the sensors and the wirings.
In the prior art, the apparatus is bound to be large because of the large numbers of sensors and wirings. Consequently, there is a problem in that the technological requirement for miniaturizing devices such as the CVD device provided in the clean room cannot be met.
Furthermore, the temperature at a heater cannot be directly detected in the prior art. Thus, the heater temperature cannot be ascertained accurately, to lead to a problem of unstable heater temperature control.
In the prior art technology, even when heating a single member by using a plurality of heaters, the temperatures at the individual heaters are sustained at levels roughly equal to one another regardless of the positions at which the heaters are installed. As a result, mutual interference occurs between the heat generated at a given heater and the heat generated at another heater, thereby presenting a problem in that uniformity is not achieved with regard to the temperature of the member.
Moreover, the temperature of a heater is adjusted by supplying power at a specific level to the heater through on/off control implemented on the power in the prior art. This results in a problem in that accurate temperature control cannot be achieved since there is a great difference in the heater temperature when power is on and the heater temperature when power is off and the heater temperature is not sustained at a constant level.
The object of the present invention, which has been completed by addressing the problems of the prior art discussed above, is to provide a new and improved apparatus and a new and improved method for implementing temperature control on a means for heating, that solve the problems discussed above and other problems as well.
DISCLOSURE OF THE INVENTION
In order to achieve the object described above, in a first aspect of the, present invention, a temperature control apparatus that implements temperature control on a means for heating which heats an object to be heated, comprising at least two means for heating each with the resistance thereof increasing as the temperature rises, at least one means for temperature detection that detects the temperature of the object to be heated, a means for target resistance calculation that calculates a target resistance for each of the means for heating by correcting a reference resistance determined based upon the set temperature for the object to be heated with a correction value obtained in correspondence to the temperature detected by the means for temperature detection and multiplying the corrected reference resistance by a temperature distribution constant that is determined in advance for each means for heating to adjust the temperature distribution at the object to be heated, a means for actual resistance calculation that determines the actual resistance at each of the means for heating based upon a feedback voltage value obtained based upon the voltage applied to the means for heating and a feedback current value obtained based upon the current flowing through the means for heating and, a means for power control that controls the power applied to each means for heating so that the actual resistance at the means for heating conforms to the target resistance, is provided.
According to the present invention, means for heating each having a resistance that increases in proportion to an increase in temperature are utilized. As a result, the temperature at each means for heating can be ascertained based upon the actual resistance determined in correspondence to the feedback voltage value and the feedback current value obtained from the means for heating. Thus, the need for providing a means for temperature detection that detects the temperature at a means for heating and a means for connection such as a wiring that connects the means for temperature detection to the temperature control device for each means for heating is eliminated. Consequently, even when heating the object to be heated by utilizing a plurality of means for heating, the initial cost can be minimized and, at the same time, the maintenance work is facilitated. Furthermore, since the temperature at each means for heating can be directly detected, accurate and stable temperature control can be implemented on the means for heating.
In addition, according to the present invention, the reference resistance used as the reference value when implementing control on each means for heating is corrected by using a correction value obtained in correspondence to the temperature detected by the means for temperature detection. By adopting such a structure, it becomes possible to control each means for heating based upon the actual temperature of the object to be heated as well as based upon the set temperature, is provided. As a result, even more accurate temperature control on the individual means for heating is achieved to set the temperature of the object to be heated even closer to the set temperature. Furthermore, according to the present invention, the target resistance is obtained by multiplying the corrected reference resistance by a temperature distribution constant that is provided to adjust the temperature distribution of the object to be heated. When such a target resistance is adopted, the temperatures of the means for heating can be adjusted in conformance to the temperature levels at the individual portions of the object to be heated. Thus, the temperature of the object to be heated can be maintained in an even more consistent manner. Moreover, the ratio of the temperatures of the individual means for heating can be adjusted so as to achieve uniformity in the temperature of the entire object to be heated in this structure. As a result, accurate temperature management is achieved for the object to be heated. The actual
Ikeda Naoto
Kasai Shigeru
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Paik Sang
Tokyo Electron Limited
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