Dynamics and Control of a Rapid Thermal Multiprocessor

Proceedings SPIE Conference on Rapid Thermal and Integrated Processing, 1595(1):2-17, 1992

• thermal_multiprocessor.pdf

A first-principles low-order model of rapid thermal processing of semiconductor wafers is derived. The nonlinear model describes the steady-state and transient thermal behavior of a wafer with approximate spatial temperature uniformity undergoing rapid heating and cooling in a multilamp RTP chamber. The model is verified experimentally for a range of operating temperatures from 400C to 900C and pressure of 1 torr in an inter N2 environment. Advantages of the low-order model over detailed models include ease of identification and implementation for real-time predictive applications in signal processing and temperature control. This physics-based model is used in the design of an advanced real-time multivariable control strategy. The strategy employed a feedforward mechanism to predict temperature transients and a feedback mechanism to correct for errors in the prediction. The controller is applied to achieve a ramp from 20C to 900C at a rate of 45deg/second in a one atmosphere environment with less than 15deg nonuniformity during the ramp and less than 1deg average nonuniformity during the hold as measured by three thermocouples.