Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-02-03
2001-05-08
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C374S179000, C118S728000, C219S446100, C219S510000
Reexamination Certificate
active
06229116
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a heat treatment apparatus such as a baking apparatus and a prebaking apparatus to be incorporated into a semiconductor manufacturing system for manufacturing a semiconductor device.
In a photolithography process for manufacturing a semiconductor device and an LCD, resist is coated on a substrate, and the resultant resist coating film is exposed to light and developed. Such a series of processing is carried out in a coating/developing system. The coating/developing system has heating sections such as a prebaking unit and a postbaking unit. Each of these heating sections has a hot plate with a built-in heater of a resistance heating type.
Recently, semiconductor device circuits have been miniaturized more and more. Their pattern wiring is formed in a width of the sub micron order. Under the circumstances, it has been strongly desired to control the heat treatment temperature of the photoresist film more accurately. The wafers W (objects to be treated) are usually treated in units (lots) each consisting of, e.g., 25 wafers. Each lot is processed under the same recipe (individual treatment program). Prebaking and postbaking are performed under heat treatment conditions according to individual recipes. The wafers belonging in the same lot are heated under the same conditions.
According to each of the recipes, the heat treatment temperature may be varied within such an acceptable range that the temperature will have no effect on a final semiconductor device. In other words, a desired temperature may differ from a heat treatment temperature in practice. When the wafer is treated with heat beyond the acceptable temperature range, a desired photoresist film cannot be obtained. Then, to obtain the desired photoresist film, a thermocouple is used for detecting the temperature of the hot plate. On the basis of the detected temperature, the power supply to the heater can be controlled in a feed-back manner. To describe more strictly, since the temperature of the entire hot plate is not uniform and varies with the passage of time, it is difficult to determine the temperature of the hot plate by a single thermocouple momentarily.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a heat treatment apparatus capable of accurately controlling a heat treatment temperature.
The heat treatment apparatus according to the present invention comprises:
a hot plate on which a substrate to be processed is to be mounted;
a heater for heating the hot plate;
a plurality of first sensors for detecting temperatures of a plurality of portions of the hot plate, respectively;
a second sensor for detecting temperature of a representative portion of the hot plate; and
a controller for controlling a heat generating operation of the heater on the basis of a plurality of first detection temperatures which are detected by the first sensors respectively, and a second detection temperature detected by the second sensor, thereby controlling the temperature of the hot plate.
It is preferable that the apparatus further have correction means for correcting each of the first detection temperatures by using the second detection temperature. In this case, the controller controls the heater on the basis of a plurality of first detection temperatures which are corrected by the correction means.
In the present invention, the relative temperatures are detected respectively by the first sensors with respect to portions of the hot plate, whereas a standard temperature of the hot plate is detected by the second sensor. The temperatures detected by the first sensors are corrected by using the standard temperature. The first sensor is advantageous in capturing a temperature distribution of the entire hot plate. The second sensor is advantageous in capturing temperatures of individual portions of the hot plate. In this manner, the first sensor and the second sensor are complemented with each other, so that thermal conditions of the hot plate can be accurately captured. Accordingly, the heat treatment can be applied to the substrate with a high accuracy. Note that at least one film of a photoresist film and an anti-reflection film is formed on the substrate. The heat treatment apparatus of the present invention is used to bake such a film.
In the heat treatment apparatus, various types of temperature sensors may be used in combination. Such sensors to be used in combination include a thermocouple, a temperature indicating resistor, a radiation type temperature sensor, and the like. The thermocouple and the radiation type temperature sensor may be used as the first sensor. The temperature indication resistor may be used as the second sensor.
As the thermocouple, a chromel-alumel thermocouple, a platinum-platinum·10% rhodium thermocouple, a platinum-platinum·13% rhodium thermocouple, and a copper-constantan thermocouple may be mentioned. Two different thermocouples selected from these thermocouples may be used in combination. Alternatively, one thermocouple may be used in combination with the temperature indicating resistor. Since the thermocouple is responsible for measuring a heat electromotive force to a standard electromotive force, the thermocouple has a stability (repeatability) to some extent. Thus, the values measured by a plurality of thermocouples do not significantly differ. However, temperature characteristics of the standard electrode are easily degraded, so that absolute accuracy of the temperature measured by the thermocouple is low. Acceptable errors in temperature measured by the thermocouple are, for example, ±0.5° C., ±1.0° C., and ±1.5° C. Since the thermocouple is low in absolute accuracy with respect to measured temperature in a high-temperature range, the reliability of the thermocouple is poor in a temperature range of 300° C. or more.
As a representative temperature indicating resistor, platinum is mentioned. In the thermo-sensor having a temperature indicating platinum resistor (hereinafter, referred to as “Pt sensor”), since temperature characteristics of the temperature indicating platinum resistor rarely change, the absolute accuracy of the measurement temperature is high. Acceptable errors in the temperature measured by the Pt sensor are, for example, ±0.35° C., ±0.50° C., and ±0.75° C. However, it is not preferable that a plurality of Pt sensors be used in combination since there is a significant difference in temperature characteristics between a certain Pt sensor and another Pt sensor. In addition, the Pt sensor is more expensive and bigger than the thermocouple.
Since the radiation type temperature sensor cannot be used in measuring an absolute value of the temperature directly unless a surface radiation rate of an object to be measured is known, the sensor is a relative temperature measurement means. Hence, the radiation type temperature sensor can be used in place of the thermocouple. However, the temperature sensor of this type is susceptible for effects of foreign matters interposed between the sensor and the object to be measured.
As the substrate to be treated, a semiconductor wafer and an LCD glass substrate are used. Usually such a substrate has a photoresist film or an anti-reflection film coated thereon. Hence, if such a film is baked at a desired heat treatment temperature, the film can be obtained in a desired quality and thickness.
It is preferable that a contact-type sensor be used as the first and second sensors since the contact-type sensor has a small error in measurement. However, a non-contact sensor may be used as the first sensor.
The first and second sensors may be fitted at any place of the hot plate. For example, a plurality of first sensors are fitted to the hot plate so as to be arranged along a radius thereof and the second sensor is fitted to the hot plate concentrically with one of the first sensors. The first sensors are fitted onto an upper surface of the hot plate and the second sensor is fitted to a side surface or a bottom surface of the ho
Sata Nobuyuki
Shirakawa Eiichi
Fuqua Shawntina
Rader Fishman & Grauer
Tokyo Electron Limited
Walberg Teresa
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