Optics: measuring and testing – By alignment in lateral direction – With registration indicia
Patent
1989-02-09
1990-07-03
Evans, F. L.
Optics: measuring and testing
By alignment in lateral direction
With registration indicia
358101, 358106, 358107, 356400, 2504911, G01B 1100
Patent
active
049386000
ABSTRACT:
Method and apparatus for measuring displacement between layers of a semiconductor wafer wherein systematic errors associated with the measurement system are eliminated. An optical system, including a microscope and a camera, records an image of registration patterns on different layers of the wafer. The image is analyzed to measure displacement between the registration patterns. A first measurement is taken, the wafer is rotated by 180.degree. about the measurement axis, and a second measurement is taken. The actual displacement between layers of the semiconductor wafer is calculated from the first and second measurements. Since the measured displacements change sign when the wafer is rotated and the systematic errors remain constant, systematic errors drop out of the calculated values of actual displacement. System errors can also be calculated for subsequent correction of measured values.
REFERENCES:
patent: 4467211 (1984-08-01), Smith et al.
patent: 4536239 (1985-08-01), Benson
patent: 4742233 (1988-05-01), Kuyel
Evans F. L.
Hantis Karen P.
Interactive Video Systems, Inc.
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