Abstract
Magnetic bearing technology is applied to a CMP wafer head to control the polish rate profile by tilting the wafer head during polishing. If no control is applied, the wafer head subsides slightly into the pad and is tilted 18×10^<-5> rad by the viscoelasticity of the pad. Tilting the head to the positive side can increase the polish rate in the wafer outer area ; tilting it to the negative side can reduce the polish rate of the wafer center area. It has been reported to be possible to improve the polish rate profile by keeping the wafer head in a horizontal position using a magnetic control. Magnetic control is available to the over hang polishing. Over hang polishing is useful for the reduction of footprint and in-situ film thickness monitor.
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