US Patent No. 9,291,921

DETECTION APPARATUS, EXPOSURE APPARATUS, DEVICE FABRICATION METHOD AND FILTER TO REDUCE A DIFFERENCE BETWEEN DETECTED INTENSITY VALUES OF LIGHTS HAVING DIFFERENT WAVELENGTH RANGES


Patent No. 9,291,921
Issue Date March 22, 2015
Title Detection Apparatus, Exposure Apparatus, Device Fabrication Method And Filter To Reduce A Difference Between Detected Intensity Values Of Lights Having Different Wavelength Ranges
Inventorship Hironori Maeda, Utsunomiya (JP)
Assignee CANON KABUSHIKI KAISHA, Tokyo (JP)

Claim of US Patent No. 9,291,921

1. A detection apparatus which detects an object to be detected, the apparatus comprising:
an illumination system configured to illuminate the object with light containing a first wavelength range and a second wavelength
range different from the first wavelength range;

a detector configured to detect light from the object illuminated by the illumination system; and
an optical member configured to set a transmittance for light in the first wavelength range and a transmittance for light
in the second wavelength range to be different from each other, thereby reducing a difference between an intensity value of
the light which has the first wavelength range and is detected by the detector and an intensity value of the light which has
the second wavelength range and is detected by the detector,

wherein
the detection apparatus has, as operation modes, a detection mode in which the detection apparatus detects the object, and
a preparation mode in which the detection apparatus makes preparations to detect the object,

in the preparation mode,
the illumination system illuminates the object with light in each of a plurality of divided wavelength ranges obtained by
dividing a wavelength range including the first wavelength range and the second wavelength range, and

the detector detects the light in each of the plurality of divided wavelength ranges from the object,
the optical member includes a plurality of optical elements which have different transmittances and are exchangeably placed
in an optical path of the light, and

the detection apparatus further comprises a control unit configured to obtain an intensity ratio in the wavelength range from
an intensity value of the light in each of the plurality of divided wavelength ranges detected by the detector, select an
optical element, which reduces the difference, from the plurality of optical elements based on the intensity ratio, and place
the selected optical element in the optical path in the detection mode.