Numerical aspects of temperature profile reconstruction using acoustic tomography in RTP

Precise wafer temperature control is crucial to the viability of the emerging technology of rapid thermal processing (RTP) for semiconductor manufacturing. The authors examine the problem of accurate noninvasive measurement of wafer temperature, which is required for precise temperature control. The paper extends the work of Khuri-Yakub et al. (1993) on acoustic techniques for noninvasive wafer temperature measurement. The authors propose a method for estimation of wafer temperatures via regularized tomographic inversion using a priori knowledge of properties of the temperature distribution and data obtained by their technique. Results of simulation studies of the methods proposed are described