Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1993-11-17
1995-07-11
Turner, Samuel A.
Optics: measuring and testing
By particle light scattering
With photocell detection
356363, 356351, G01B 902
Patent
active
054326036
ABSTRACT:
An optical element comprised of a plurality of polarizing beam splitters is provided on the optical path of a two-frequency linearly polarized laser beam source, and the optical element divides a light beam from the two-frequency linearly polarized laser beam source into two light beams, whereafter these two light beams are incident on diffraction gratings provided on a mask and a wafer, respectively. A pair of mirrors are provided vertically above the mask, and a pair of lenses, a pair of polarizing plates and a pair of photoelectric detectors are arranged in succession in the directions of reflection of the pair of mirrors. The outputs of the two photoelectric detectors become beat signals, and the phase difference between these beat signals is measured, whereby the alignment of the mask and wafer is effected. Since the optical element is comprised of a plurality of polarizing beam splitters, leak-in light included in each light beam is reduced.
REFERENCES:
patent: 4353650 (1982-10-01), Sonnargren
patent: 4859066 (1989-08-01), Sonnargren
patent: 5000573 (1991-03-01), Suzuki et al.
patent: 5028797 (1991-07-01), Abe et al.
patent: 5225892 (1993-07-01), Matsugu et al.
Matsumoto Takahiro
Nose Noriyuki
Saito Kenji
Sentoku Koichi
Tsuji Toshihiko
Canon Kabushiki Kaisha
Kim Robert
Turner Samuel A.
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