Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-08-11
2001-07-24
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S494000, C219S405000, C250S497100, C374S123000, C118S724000
Reexamination Certificate
active
06265696
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a heat treatment technique used in the field of semiconductor devices and particularly to a heat treatment method and a heat treatment apparatus for controlling the temperature of a substrate surface.
In recent years, as high integration of semiconductor devices has progressed, patterns have been miniaturized and preciseness thereof has been improved. In steps of manufacturing a photomask used for pattern exposure, a means for subjecting a photosensitive material to a heat treatment is necessary for the step of forming a pattern. In the process including the step of heating or cooling substrates to be exposed, variants of the treatment temperature are reflected on variants of the pattern size. Therefore, more precise management of the temperature has been demanded in accordance with miniaturization and improvement of the preciseness.
Conventionally, a thermocouple or a resistance bulb is embedded near the surface of a heating plate used for a heating treatment to measure the temperature, when managing the temperature of a substrate. Further, the output of a heating mechanism is controlled based on the obtained temperature, and a heat treatment is performed. However, since quartz forming the under layer of the substrate to be exposed has a very low thermal diffusivity, temperature of the photosensitive material film on the surface of the substrate to be processed cannot be accurately controlled by the method described above.
To perform precise temperature control with user of a quartz substrate used for a substrate to be exposed, it is necessary to measure directly the temperature of the film as a target to be subjected to a heat treatment on the substrate. Means for measuring the surface temperature are roughly divided into two types, one being a contact type and the other being a non-contact type, depending on the characteristics of a monitoring method.
As the contact type, there is a method of measuring the surface temperature by embedding a thermocouple into a film as a target on the substrate. However, it is not a realistic way to embed thermocouples into all substrates to be processed. Also, a photomask manufactured and processed by embedding directly a thermocouple in the substrate to be processed is not suitable for practical use. By attaching a thermocouple or a resistance member, the temperature characteristic is changed. Therefore, there is a problem that the photosensitive material film as a target to be heated cannot be accurately measured. In particular, it is impossible to embed a temperature sensor into a photosensitive material film having a film thickness of about 0.1 to 2 &mgr;m called a resist.
From the reasons described above, it is preferable to use the temperature measuring method of the non-contact type. A radiation thermometer is a representative example of the temperature measuring device of this type. There is an example using the radiation thermometer which has succeeded in measurement of a surface temperature of a steel material having a precise oxide film processed by a shape steel line or the like.
However, the temperature measurement of a substrate to be processed or the like with use of the radiation thermometer involves the following problems. In this measurement, since the temperature of the temperature measurement area is as low as about 50 to 200° C., the signal is weak. Therefore, if other radiated light than that from the target to be measured enters into the sensor section, a measurement error is caused. In addition, it is not possible to neglect a measurement error due to drifting of the sensitivity which is considered as depending on the environmental temperature and the like. From the reasons described above, the radiation thermometer involves a problem that accurate temperature measurement is difficult.
In addition, to obtain more precise patterns, it is highly necessary to use a step of measuring the temperature of the substrate surface with high preciseness and of performing heating (or cooling) based on the measurement result. Therefore, demands for a method and an apparatus, by which temperature measurement is carried out while monitoring the surface temperature of a substrate (in-situ) and feedback is immediately reflected on a heat control section or the like, have become more and more serious.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described situation, and has an object of providing a heat treatment method and a heat treatment apparatus, by which the surface temperature of a substrate to be processed such as a substrate for exposure can be measured with high preciseness so that accurate temperature management of a thin film formed on the substrate can be achieved.
To achieve the above object, the present invention according to a first aspect thereof has the structure as follows. A heat treatment method is characterized by comprising steps of: measuring a temperature of a thin film formed on a substrate to be processed, by a radiation thermometer which performs measurement with use of a wavelength range except for a wavelength range of light which is transmitted through the thin film; and controlling a heated temperature of the thin film in response to the temperature measured by the step.
Also, to achieve the above object, the present invention according to the second aspect thereof has the structure as follows. A heat treatment apparatus is characterized by comprising: a support member for supporting a substrate to be processed, on which a thin film is formed; a heating section for heating the thin film; a radiation thermometer for measuring a surface temperature of the thin film; and a control section for controlling a temperature which is heated by the heating section, in response to the temperature measured by the radiation thermometer.
Also, to achieve the above object, the present invention according to a third aspect thereof further comprises, before the step of measuring the temperature of the thin film, steps of: measuring a surface temperature of a reference sample which is made of same material as the substrate and is set at a target temperature, by the radiation thermometer; and correcting a measurement value of the radiation thermometer, based on temperature data obtained by the step of measuring the temperature of the reference sample.
Also, to achieve to the above object, the present invention according to a fourth aspect thereof has a structure as follows. The heat treatment apparatus described above further comprises: a reference sample which is made of same material as the substrate and is set at a target temperature; and a correcting section for measuring a surface temperature of the reference sample, and for correcting a measurement value of the radiation thermometer, based on temperature data obtained by measurement of the surface temperature of the reference sample.
Preferred embodiments of the present invention will be as follows, for example.
(1) The substrate to be processed is a photomask blank in which a thin film containing metal made of chrome (Cr) or the like is formed on a transparent substrate made of quartz or the like, and a photosensitive thin film made of a chemical amplification type resist or the like is formed thereon.
(2) There is provided a blackbody for cutting stray light which enters into the radiation thermometer through the surface of the substrate.
(3) The blackbody is provided at a position optically symmetrical to the radiation thermometer with respect to a surface of the thin film, and the blackbody is set at a predetermined temperature.
(4) The radiation thermometer is an infrared sensor.
(5) The radiation thermometer makes measurement with use of light of a wavelength range except for light of a wavelength range which is radiated to the radiation thermometer from the substrate.
(6) The wavelength range of the light measured by the radiation thermometer is set to either a range of 2.7 to 2.8 &mgr;m or a range from 4.3 &mgr;m. Furthermore, the wavelength range of the li
Arikado Tsunetoshi
Higashikawa Iwao
Ito Shin'ichi
Kumagae Akitoshi
Okumura Katsuya
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Fuqua Shawntina
Kabushiki Kaisha Toshiba
Walberg Teresa
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