A Robust Controller Design for Uniform Temperature Control of Nonlinear Multivariable Rapid Thermal Processor

The problem of temperature control for rapid thermal processor(RTP) is considered in this paper. In RTP of semiconductor wafers, not only accurate control of the wafer temperature but also temperature uniformity through the whole wafer are essential. RTP model considered in this paper is highly nonlinear due to its thermal properties. A robust controller is designed for this RTP model using an H_∞ two degree-of-freedom controller design method, and it is shown that the controller designed performs good tracking and temperature uniformity over a wide range of operating temperatures. Application of the controller to one of manufacturing processes(i.e. oxide growth process) is also investigated in accordance with its temperature profile and seems to be good. Finally, controller reduction is considered, showing possibility of the use of reduced-order controller.