Automatic measurement of thickness as applied to germanium wafer production in transistor manufacture

摘要

The paper first examines the problems involved in the measurement of the thickness of germanium wafers, the difficulties encountered in handling and manoeuvring them due to their small size and weight and the nature of their material composition. Errors and failings in hand measurement are discussed, together with the advantages of mechanical measurement. The design and construction of an automatic measuring machine are then described, showing how the wafers are measured, sorted into seven different sizes and counted. The movement of them to the measuring point is by mechanical means, but they are measured, sorted and counted electronically. Measurement is effected by an electronic comparator of high magnification and accuracy, the output signal of which is amplified and then used to operate the sorting mechanism. Some half-million wafers were measured during the development period, which is described, together with the difficulties encountered and the modifications found necessary finally to produce the consistency and accuracy of measurement required. In conclusion, the assets of the machine in eliminating human error in hand measurement and operator fatigue, together with its production capacity, are described.