Characterisation of the transfer function of an advanced process control system for chemical mechanical polishing (CMP)

Chemical Mechanical Polishing (CMP) is widely used for planarisation in semiconductor manufacturing. While the process is capable in terms of producing surfaces of extreme planarity and integrity, there is inherent drift due mainly to physical and chemical changes of the polishing pad surface. Our Research Centre is pioneering a new concept for advanced process control (referred to as multifunctional intelligent tooling, MIT) with the potential to provide a paradigm improvement in control capabilities. The test programme described below was designed to characterise the transfer function for an MIT control system. The tests involve monitoring the stress-strain response in a basic compression test of the pad and further simulating the basic CMP set-up where a geometrically similar pad is subjected to similar cyclical pressures. Results indicate that the sample material, geometrical dimensions and loading velocity all have effects on the pad compression stress-strain response, but pads demonstrate relatively linear behaviour within the 0 to 10% strain region under different experimental conditions.