A model is described which determines pyrometer measurements of the temperature of silicon wafers. The wafers may have any combination of silicon polysilicon and 2 on it. The inputs to the model are the wavelength range of the pyrometer temperature film thicknesses and order doping levels and polysilicon grain size. Experimental data provides qualitative agreement to the model. Since the emissivity of the wafer is shown to generally vary with radiation wavelength conventional multi-wavelength pyrometry does not have any obvious ways of compensating for measurement differences due to varying wafer structures. However there may be an empiricalbased alternative for multi-wavelength corrections. 1 Background As rapid thermal processors find their way into commercial applications they are likely to face increasingly tighter requirements in the control of the transient and steady state temperature of the wafer. To achieve this level of control accurate closed loop temperature control is necessary for many commercial applications of rapid thermal processing. The temperature measurement tool usually employed in these closed loop control systems is one or more pyrometers. Pyrometers determine the temperature of the wafer by measuring the magnitude of the radiation being emitted from the wafer. The relationship between temperature and spectral radiant exitance can be expressed as follows: [7] M (1) where M is the spectral radiant exitance of the wafer Mb is the spectral exitance of a black body (both measured in Watts/rn3) and