To detect a substrate temperature in a low-temperature range, where accuracy in temperature measurements made by a temperature measuring means becomes lower than allowable accuracy, without keeping the cost unchanged.
When heating is finished (step S3), a substrate is cooled down, and a substrate cooling curve is obtained in approximating manner by the use of the least squares method with respect to the measurement results of substrate temperatures in a prescribed range of temperature higher than the measurable lower limit temperature of a radiation thermometer (step S6). The time required for a substrate to reach to an unloading temperature is obtained by the substrate cooling curve obtained (step S7). As a result of this setup, even without providing a temperature measuring means other than a radiation thermometer is, a substrate temperature lower than a measurable lower limit temperature can be obtained.
TAKAHASHI MITSUKAZU
SASAKI KIYOHIRO
