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SemDex A32

Production inspection in a clean room

Substrate-thicknesses with sub-µm accuracy

The substrate layer thickness of a wafer must be determined with a high degree of accuracy after back grinding or etching in order to ensure optimum starting conditions for further processing. A StraDex f sensor integrated into a SemDex wafer-inspection system measures and evaluates the respective thickness at every measured point. Sequential scanning of the object and the small spot size of the sensor translate into a high lateral resolution. The difference between the maximum and the minimum thickness over the entire wafer yields the Total Thickness Variation (TTV).

2D Schichtdickenverteilung

Moreover, a combination of two StraDex f sensors (above and below) can determine the total thickness of an object after the manner of an optical comparator. This mode of operation is particularly suitable for very thick objects and also for those that are optically non-transparent, e.g. highly doped and metallic.

Measuring systems for:

Substrate Layer Thicknesses and TTV