A Theoretical Method for Removal of Gravity-Induced Effects in Silicon Wafer Geometry Measurements

In the current study, an improved method to obtain measurements of geometry of silicon wafers capable of removing the effect induced by gravity and the contact of supports is presented. The classical method only requires two measurements, while the proposed method requires several images. Nevertheless, the classical method relies on the perfect placement and alignment of the wafer over the supports, while the proposed method is strongly immune against misplacing and misaligning the wafer from one measurement to another. The mathematical basis for the new method is presented together with results of a simulation that compares the performance of the classical and the proposed method. It is also shown that, for placement errors as small as 100 nm, the proposed method has better results than the classical method.