In-situ wafer parameter measurement method employing a hot susceptor as radiation source for reflectance measurement

A method of measuring surface emissivity of a specimen by reflectance of environmental radiation, comprising:

• providing a susceptor that is heated to a known temperature, the susceptor having a support surface that includes an open region and emitting an amount of radiation corresponding to the known temperature;
• positioning a wavelength selective sensor in optical communication with the open region, the sensor being wavelength selective within a measurement wavelength range;
• providing a specimen having a susceptor contact surface and placing it at rest on the support surface of the heated susceptor, the specimen being nominally opaque at the measurement wavelength range and reflecting from the susceptor contact surface at the open region the radiation emitted by the heated susceptor;
• and
• using the sensor to acquire a reflectance measurement of the radiation reflected by the specimen contact surface resting on the susceptor contact surface under conditions in which the specimen is significantly colder than the susceptor so that the reflectance measurement is indicative of the emissivity of the specimen.