Method and apparatus for measuring the curvature of wafers with

Details Method and apparatus for measuring the curvature of wafers with Method and apparatus for measuring the curvature of wafers with

1993-10-22

1996-06-04

Le, Que T.

Radiant energy

Photocells; circuits and apparatus

With circuit for evaluating a web, strand, strip, or sheet

25055927, 356376, G01N 2186

Patent

active

055235824

ABSTRACT:
A method and apparatus for measuring the curvature of a wafer. The apparatus includes a laser head that includes multiple laser sources that each emit a laser beam, each beam having a different wavelength. A CPU selects one of the sources to emit a beam. The beam is directed through a lens within the laser head and onto a surface of a wafer. The beam is reflected from the surface of the wafer and detected by a detector. The present invention includes a motor to cause relative motion between the laser head and the wafer such that the beam scans across the surface of the wafer, relaying data to the detector and the CPU. The CPU calculates the curvature of the wafer surface using the scanned data. The CPU selects a different laser source to direct a beam having a different wavelength at the wafer surface to avoid destructive interference that may occur with previously-used wavelengths. Other embodiments include the laser sources within a carousel apparatus, and the addition of a beamsplitter to transmit and reflect selected beams onto the wafer surface.

REFERENCES:
patent: 4432239 (1984-02-01), Bykov
patent: 4566797 (1986-01-01), Kaffka et al.
patent: 4667316 (1987-05-01), Suda et al.
patent: 5029245 (1991-07-01), Keranen et al.
patent: 5134303 (1992-07-01), Blech et al.
patent: 5248889 (1993-09-01), Blech et al.

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