Nonlinear Run-to-Run Controller for Semiconductor Manufacturing

Run-to-run control is a generic methodology in control of semiconductor manufacturing processes. It is a model based process control strategy whereby process inputs (recipes) are adjusted on a run-to-run basis in response to measurements (responses) of process state variables. It updates the recipes of the process at the beginning of each run. In semiconductor manufacturing, many processes are subjected to small drifts or shifts. If the perturbations are small enough, they can be compensated successfully using the exponential weighted moving average (EWMA) method. But, unfortunately, this is not always the case. For example, many plasma processes have been shown to exhibit small to large non-linearity in behavior. Furthermore, the photoresist process and the chemical mechanical processing (CMP) process require dynamic process models too. Thus it is hard to use a linear model to approximate the process and necessary to develop nonlinear algorithms to solve this type of problems.