Method and apparatus for automated reading of vernier patterns

Details Method and apparatus for automated reading of vernier patterns Method and apparatus for automated reading of vernier patterns

1986-12-22

1988-05-03

Fields, Carolyn E.

Radiant energy

Means to align or position an object relative to a source or...

2504922, 356400, 356401, 368490, G01N 2304

Patent

active

047422335

ABSTRACT:
Automatic determination of the lateral offset between a pair of overlapping vernier patterns (20 and 22) on overlying layers (14 and 15) of a semiconductor wafer (10) is achieved by first capturing the image of the vernier patterns using a television camera (26). The output signal of the television camera is processed by an image acquisition circuit (32) coupled to a computer (34) to determine the intensity of each of a plurality of pixels lying within a strip extending across the image of the vernier patterns. The intensity of each of the pixels is mathematically correlated by the computer (34) with each of a plurality of values corresponding to the intensity of each of a plurality of pixels comprising an image representative of a pair of aligned vernier patterns. The location within the captured image of the maximum of the correlated intensities is then found. The offset between the pair of vernier patterns is determined in accordance with the distance between the location of the maximum of the correlated intensities and the center of one of the pair of vernier patterns.

REFERENCES:
patent: 4200395 (1980-05-01), Smith et al.
patent: 4292672 (1981-09-01), Southgate
patent: 4349880 (1982-09-01), Southgate
patent: 4449193 (1984-05-01), Tournois

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