Evaluation of Polishing Pad Property by Rubber Hardness Test-estimating Edge Surface Flatness of Workpiece

Demand for diminishing edge roll off of workpiece has rapidly increased, particularly in polishing silicon wafers as the substrates of the semiconductor devices and glass disks as the substrates of magnetic media disks. In general, the usage of harder polishing pads is thought to be very effective in achieving the high surface flatness of the workpiece edge. Then the hardness, especially the rubber hardness of the polishing pads is widely measured as one of the most important pad specifications in practical processes. However, it has not been clarified whether the edge surface flatness can be estimated by the current rubber hardness tests. Then, based on the elastic contact theory, the polishing pad property which influences the surface profile near the edge was investigated and, as a result, it was found that the usage of the indenter with a diameter of 20 mm or above could estimate the obtained edge surface flatness appropriately in indentation tests such as rubber hardness tests.