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US 5,633,747 AGranted
Variable spot-size scanning apparatus
AssigneeTencor Instruments
InventorMehrdad Nikoonahad
Life of this patent
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AssigneeTencor Instruments
InventorMehrdad Nikoonahad
Estimating the term…
An apparatus for both deflecting a beam of light illuminating a spot on a surface and varying the size of the spot, electronically, without changing any system components. The apparatus includes an acousto-optic deflector driven with a linear FM signal produced by a chirp signal generator. The linear FM signal is characterized with a dispersion rate, and the chirp signal generator includes a chirp dispersion selector to vary the dispersion rate. A beam of collimated light passes through the acousto-optic deflector and appropriate focusing optics image the beam onto a spot in a nominal focal plane. The chirp dispersion selector sets the dispersion rate in accord to a nominal rate, resulting in the beam illuminating a spot in the focal plane. Generally, the focal plane coincides with a wafer surface, of the type having periodic and non-periodic features on it. The spot size may be varied from that of a diffraction limited spot to a spot whose maximum size is system dependent. The spot size varies as a result of changing the dispersion rate of the chirp signal. The spot size may vary as it is scanned, or may remain fixed during the inspection of a wafer. In this manner, inspection by periodic feature comparison may be implemented when it proves advantageous. Alternatively, a larger spot may be obtained when periodic feature comparison would provide no benefit, and spatial filtering would achieve an enhanced signal/background.
An apparatus for scanning a patterned wafer of the type having periodic and non-periodic features comprising:
An apparatus for deflecting a beam of light illuminating a spot on a surface, of the type having periodic and non-periodic features, comprising:
An optical scanning system for defect and foreign matter detection on a surface comprising,
A method for scanning a patterned wafer of the type having periodic and non-periodic features comprising:
A method for varying a size of a spot produced by a beam of light illuminating a surface comprising the steps of:
An optical scanning method for anomaly detection on a surface comprising,
A method for scanning a patterned surface of the type having periodicity characteristics, comprising:
An apparatus for deflecting a beam of light illuminating a spot on a surface, comprising:
Dependencies are inferred from the claim text.