high precision and better circuit layouts on the wafer can then be developed application_number US 41786699 A description it is an object of the present invention to provide a method of pressure detection on the surfaces of the wafer and the pressure related components so that different modes of feedback loop analysis for system correction and modification can be generated for further improvements on the wafer cmp process referring to fig3 a a side view of a wafer carrier and a polishing pad belonging to a cmp machine is shown the components of which are arranged in such a fashion that a method to detect pressure distribution can be directly applied on the surfaces one of the surface of the wafer 30 to be processed by cmp is in contact with the surface of the wafer carrier 32 in holding position and both of these two components are to be pushed towards the polishing pad 34 until the other surface of the wafer 30 overlaps and touches the surface of the polishing pad 34 the body structure of the wafer carrier 32 is made of steel and a rubber ring 36 is installed on the working surface of the wafer carrier 32 cushioning a wafer 30 which is securely held on top of the airtight rubber ring by vacuum pressure during a cmp operation the vacuum is actuated by evacuating air with a pump through a center hole 38 on the wafer carrier 32 a wafer 30 will then stick to the working surface of.