To achieve flattening of a sheet by a method wherein hardness of a surface plate is changed according to the position in a radial direction of the surface plate and the surface of the surface plate is maintained approximately in a flat state, in a device to apply surface machining, such as polishing, on the sheet by pressing the sheet on the surface plate.
In such a way that when lapping is applied on the surface of a semiconductor wafer 20, a lower surface plate 11, an upper surface plate 12, and a carrier 13 are rotationally driven and the semiconductor wafer 20 is rotated as it is removed, surface machining is applied on the two surface of the semiconductor wafer 20. In this case, when surface machining is applied on the semiconductor wafer 20 larger than the carrier 13, the intermediate part in a radial direction of the lower surface plate 11 is tended to be seriously worn compared with the inner peripheral part and the outer peripheral part thereof. In which case, the surface plates 1 (11, 12) have an inner peripheral part 1a formed of a soft material, an intermediate part 1b formed of a rigid material, and an outer peripheral part 1c formed of a soft material and hardness is continuously changed. This constitution maintains the surface of the surface plate 1 approximately in a flat state and improves flattening of the semiconductor wafer 20.
NISHIMAKI NOBUYUKI
SEKIKAWA SHOHEI
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