the present invention is a method and apparatus for calibrating a temperature feedback value in a wafer processing chamber to automatically compensate for variations in infrared emissions from a heated semiconductor wafer due to variations in composition and coatings from wafer to wafer . a calibration wafer with an imbedded thermocouple is used to generate a table relating actual wafer temperatures to power supplied to the heating chamber and infrared emissions detected by a pyrometer . a sample wafer of a batch to be processed is subsequently placed in the chamber at a known power level , and any difference between the detected infrared emission value and the value in the table is used to adjust the entire table according to a first predetermined formula or table . before each wafer is processed , a known source of infrared light is reflected off the wafer and detected . the reflected light value is compared to a reflection measurement for the sample wafer . the difference in reflection measurements is correlated to emissions from heating , and the calibration table is fine - tuned with the correlation value according to a second predetermined formula or table to account for variations in emissions between individual wafers due to variances in wafer surface conditions .