| Semiconductors as well as MEMS are often produced on wafers with diameters from 150 mm to 300 mm. During manufacturing, the wafers (silicone, glass or sapphire) are iteratively treated by various polishing, etching or grinding processes to achieve a perfectly flat surface. The total thickness variation (TTV) of those finished wavers lays in the range of several micrometers and is a critical characteristic for quality. Therefore, the TTV is the most important parameter besides the surface topography of a waver. Up to today, available metrology instruments have not been able to simultaneously measure both, TTV and roughness at high resolutions.
FRT has developed the surface metrology tool MicroProf® TTV for this demanding application. The system inspects in a contact-free fashion both upper and the lower surface of a wafer for TTV, bow or warp. At the same time, it measures topography, roughness or profiles for computer aided evaluation. The integrated optical sensors work quickly and precisely at a height resolution of up to 3 nm. Furthermore, the multi-sensor capable instrument can be extended with AFM for even higher resolutions. Overall, the MicroProf® TTV performs the following tasks fully automated: measurement of total thickness variation, parallelism, bow, warp, roughness, film thickness, step height, pitch, bumps, PGA’s, profile, contour, trenches, topography, geometry, coplanarity, critical dimensions, and angles. Automated wafer handling and cleanroom compatibility up to class 1 are offered on demand.
The images depict a MicroProf® TTV 300 mm with sensor configuration as well as a sample measurement.
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