Method for measuring substrate temperature in radiant heated reactors

Abstract

The heat energy in a reactor used to process substrates is controlled to allow a more accurate measurement of the substrate temperature. The method of substrate temperature measurement is applicable to any reactor geometry and any type of heat source. Further, the method does not affect the process and so the performance of the reactor is unaffected when the substrate temperature measurement method is utilized. At a first predetermined time t1 during the process cycle, power to the heat source is turned off. At a second predetermined time t2, i.e., at the end of a time interval after the power is turned off, the heat energy from the reactor is measured for a predefined time interval, i.e., from second predetermined time t2 to a third predetermined time t3. After the measurement, i.e., at a fourth predetermined time t4, the power to the heat source is turned-on again and the process cycle continues. The time window over which the power is turned-off, i.e., the time between the first and fourth predetermined times, is small relative to the heat cycle in the particular process. Consequently, the process is unaffected by the brief interruption in heating. However, during the brief interruption, the only contribution to the heat energy in the reactor is from the substrate and other black body radiation.