WGI 300 is a fully automatic measuring system which can measure and geometrically evaluate the edge profiles of 300 mm wafers extremely precisely. The wafer is rotated enabling profile measurements to be carried out at any number of points on the circumference of the wafer. The sophisticated measurement setup is even able to deliver a full geometrical characterisation of the wafer edge in the notch area.

The absolute orientation of the wafer is determined by a high-resolution area scan camera system, the notch serving as the reference. This means that each and every profile measure-ment is exactly reproducible. A simultaneous top-view measurement carried out by this camera system serves to check the wafer diameter.

The very high measuring accuracies achieved by the system are due to the use of light-sectioning sensors with extremely short line lengths. Each of these sensors is set to measure a third of the total profile at each measuring position. The software automatically combines these 3 sub-profiles to form a total profile. The profile measurement is repeated sev-eral times at each measurement position and averaged accordingly in order to increase repeat accuracy.

The software uses special algo-rithms to calculate the geometrical contour of the wafer edge from these averaged profiles. This mathematical contour is used as the basis for all further geometrical evaluations.

In order to pick up even the most minute profile deformations, the system carries out a comprehensive geometrical comparison of the calculated contour with a saved nominal contour. The tolerance range can be selected freely.

The results of the comprehen-sive contour evaluations include the lengths, radii and angles which are characteristic for wafer edges. Accuracies of up to ±1 µm or ±0.2° can be achieved.

The top-view measurement delivers the geometrical characteristics of the notch.

The pass/fail assessment of the test specimen is performed automatically using the calculated parameters.

SEC II/GEM interfaces are provided for data transfer.

Because of the high degree of flexibility it affords, WGI 300 can be used for laboratory measurement tasks as well as for checking and setting various processing steps in wafer manufacturing. The Equipment Front End Module (EFEM) is the perfect solution for integration.