An incorrect position of a semiconductor wafer during thermal treatment in a process chamber heated by means of infrared emitters and transmissive to infrared radiation is identified, wherein the semiconductor wafer lies in a circular pocket of a rotating susceptor and is held at a predetermined temperature with the aid of the infrared emitters and a control system, and wherein thermal radiation is measured by a pyrometer, an amplitude of the fluctuations of the measurement signal is determined and an incorrect position of the semiconductor wafer is assumed if the amplitude exceeds a predetermined maximum value. The pyrometer is oriented such that the measurement spot detected by the pyrometer lies partly on the semiconductor wafer and partly outside the semiconductor wafer on the susceptor so that it is possible to identify an eccentric position of the semiconductor wafer within the pocket of the susceptor.