The temperature of a thin photoresist layer on a silicon wafer was measuredinsituduring dry etching by using a silver halide optical fiber noncontact thermometer. A two‐bandpass radiometer was constructed to reduce errors arising from geometrical factors and emissivity changes. Such a system may be used to monitor surface temperatures during dry processing of semiconductors and to prevent overheating that may cause damage, such as cross linking of photoresists. ©1996 American Institute of Physics.