Abstract: The present invention discloses a feedback and feedforward process control system, comprising the steps: 1.) Determining an output variable that is highly correlated with the controlled variable, the variation of which is mainly influenced by upstream processes rather than current process, 2.) Processing a semiconductor wafer with a first set of parameters, 3.) Measuring the output variable that is highly correlated with the controlled variable after the semiconductor wafer is processed, 4.) Developing a predictive feedforward signal based on the output variable, 5.) Measuring the controlled variable after the semiconductor wafer is processed to be used as feedback signal, and 6.) Determining a second set of parameters based on feedback and feedforward signals.