Multivariable control of multi-zone chemical mechanical polishing

The modeling and multivariable control of the multi-zone CMP are studied in this work. In the process control notation, the manipulated variables are the three pressures applied to each zone. Therefore, this is a 60/spl times/3 non-square multivariable control problem. The singular value decomposition (SVD) is used to design a non-square feedback controller. The proposed control system is test on incoming wafers with different surface profiles. Results show that achievable performance can be maintained using the proposed SVD controller.