US 9,810,530 B2
Autofocus system and method
Daniel Gene Smith, Tucson, AZ (US); and Eric Peter Goodwin, Tucson, AZ (US)
Assigned to NIKON CORPORATION, Tokyo (JP)
Filed by Nikon Corporation, Tokyo (JP)
Filed on Jan. 9, 2015, as Appl. No. 14/593,190.
Application 14/593,190 is a continuation of application No. 13/066,741, filed on Apr. 22, 2011, abandoned.
Claims priority of provisional application 61/343,074, filed on Apr. 23, 2010.
Prior Publication US 2015/0116729 A1, Apr. 30, 2015
Int. Cl. G01B 9/02 (2006.01); G01B 11/25 (2006.01); G01B 11/06 (2006.01); G03F 7/20 (2006.01)
CPC G01B 11/25 (2013.01) [G01B 11/0608 (2013.01); G03F 7/70641 (2013.01)] 28 Claims
OG exemplary drawing
 
1. An autofocus system for use with a lithography exposure tool configured to expose a target substrate, said autofocus system comprising:
a fringe projection system configured to project, at respectively corresponding multiple wavelengths, sinusoidal fringe patterns from a diffraction grating disposed inside the fringe projection system through a first optical element onto a surface of the target substrate, to form target sinusoidal fringe patterns thereon,
said fringe projection system configured to deliver, to the target substrate, only light in +1 and −1 diffraction orders formed by said diffraction grating from light incident thereon;
a fringe detection system having sensing elements positioned
to acquire optical images of respectively corresponding target sinusoidal fringe patterns through a second optical element and an optical polarization-filtering element, and,
to generate corresponding outputs respectively representing said images,
wherein said optical images are formed at different wavelengths and different polarization states;
a data processing system in operable communication with the sensing element and configured
(i) to generate data based on the output, the data indicative of topology features on the surface of the target substrate as the substrate is moved relative to said target sinusoidal fringe patterns;
(ii) to generate processed data to determine a topology profile of the surface of the target substrate in the vicinity of said target sinusoidal fringe patterns as the substrate is moved relative to the target sinusoidal fringe patterns.