Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1989-04-24
1991-07-02
Willis, Davis L.
Optics: measuring and testing
By particle light scattering
With photocell detection
356351, 356357, 356361, G01B 902
Patent
active
050281364
ABSTRACT:
A heterodyning interferometric monitoring apparatus for simultaneously measuring in situ and in real time the optical and physical thicknesses of a sample during a deposition process. A linearly polarized monochromatic light beam is passed through a frequency shifter which produces therefrom a dichromatic light beam having two orthogonally linearly polarized components at respective different frequencies. The dichromatic beam is applied to a modified Twyman-Greene interferometer, from which two heterodyne light beams emerge. The first of the two light beams is a combination of light at the first frequency reflected from the sample and light at the second frequency reflected from a reference plate, from which the physical thickness of the sample can be determined using a heterodyne signal detector. The second light beam is a combination of light at the first frequency passed through the sample and light at the second frequency passed through the reference plate, from which the optical thickness of the sample can be determined using another heterodyne signal detector.
REFERENCES:
patent: 4575247 (1986-03-01), Tansey
patent: 4909631 (1990-03-01), Tan et al.
Bartholomew Craig S.
Betz Howard T.
Harris Richard J.
Kogler Kent J.
Murarka Narayan P.
IIT Research Institute
Koren Matthew W.
Willis Davis L.
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