Abstract: An apparatus and method for providing substantially uniform substrate temperature in a chemical vapor deposition reaction chamber is provided. The method and apparatus utilize a carrier for holding at least one substrate in the reaction chamber and a plurality of heating elements arranged to heat the carrier and the at least one substrate. At least one substrate pyrometer measures the temperature of the substrates to provide a signal representing the process temperature. This signal is used in a feedback loop to control one or more of the heating elements. At least two carrier pyrometers focused at different zones of the carrier are provided. The signals from the carrier pyrometers are compared to one another to provide an indication of temperature non-uniformity. This indication is used in a separate feedback loop to adjust other heating elements so as to maintain temperature uniformity across the carrier.