Modeling and control of an epitaxial silicon deposition process with step disturbances

The Run by Run (RbR) Controller, which performs automated on-line optimization and control of VLSI processes, is considered. The RbR Controller combines statistical process control and feedback control to prescribe control responses which minimize the variation of the process output. It functions by adapting a model to the changing process and designing a new recipe based on the adapted model. The rapid mode of the controller responds to shifts in a process while the gradual mode responds to process drifts. To test the rapid and gradual modes, experiments were performed on a radiantly heated barrel epitaxy reactor. The performance of the reactor under control of the gradual mode was found to be superior to previous performance with no control action taken. The effects of step disturbances (shifts) on the epitaxy process were investigated, and it was found that the simplest approach to rapid mode (where the process model is adapted by changing only the constant term) would respond to these shifts in a constant stable manner.<
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