Method and apparatus for measuring the shape and thickness...

Optics: measuring and testing – By light interference – For dimensional measurement

Reexamination Certificate

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C356S511000

Reexamination Certificate

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06847458

ABSTRACT:
The present invention consists of a technique and device for measuring the thickness variation and shape of wafers or other polished opaque plates. A combination of two improved phase-shifting Fizeau interferometers is used to simultaneously measure the single-sided distance maps between each side of the wafer and the corresponding reference flat, with the thickness variation and shape being calculated from these data. Provisions are made to determine and eliminate the shape and tilt of the reference surfaces, and also to facilitate the correct overlay of the two single-sided measurements for the calculation of thickness variation and shape.

REFERENCES:
patent: 4653922 (1987-03-01), Jurisch
patent: 4732483 (1988-03-01), Biegen
patent: 5473434 (1995-12-01), de Groot
patent: 5502564 (1996-03-01), Ledger
patent: 5909282 (1999-06-01), Kulawiec
patent: 5995226 (1999-11-01), Abe et al.
patent: 6061133 (2000-05-01), Freischlad
patent: 6249351 (2001-06-01), de Groot
patent: 6480286 (2002-11-01), Kubo et al.
patent: 6504615 (2003-01-01), Abe

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