Characterization of transmission losses in an optical system
First Claim
Patent Images
1. A method for characterizing transmission losses in an optical system, comprising:
- splitting a radiation beam into a reference portion and a measurement portion;
during a measurement of the reference portion, detecting an illumination profile of the reference portion reflected from a moveable reference mirror in a first position;
during a measurement of the measurement portion, detecting an illumination profile of the measurement portion after the radiation beam has traveled through the optical system and detecting the illumination profile of the reference portion reflecting from the reference mirror in a second position, the second position being different than the first position; and
comparing the illumination profile of the reference portion to the illumination profile of the measurement portion to characterize the transmission losses in the optical system.
1 Assignment
0 Petitions
Accused Products
Abstract
The illumination profile of a radiation beam is initially measured using a CCD detector. A reference mirror is then placed in the focal plane of the high aperture lens and the reflected radiation measured. By comparing the illumination profile and the detected radiation it is possible to determine the transmission losses for S and P polarisation which can then be used in scatterometry modeling.
64 Citations
21 Claims
-
1. A method for characterizing transmission losses in an optical system, comprising:
-
splitting a radiation beam into a reference portion and a measurement portion; during a measurement of the reference portion, detecting an illumination profile of the reference portion reflected from a moveable reference mirror in a first position; during a measurement of the measurement portion, detecting an illumination profile of the measurement portion after the radiation beam has traveled through the optical system and detecting the illumination profile of the reference portion reflecting from the reference mirror in a second position, the second position being different than the first position; and comparing the illumination profile of the reference portion to the illumination profile of the measurement portion to characterize the transmission losses in the optical system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A method for measuring properties of a substrate, comprising:
-
projecting a radiation beam onto the substrate, wherein the radiation beam is directed through an optical system; detecting an intensity distribution of a reflected radiation beam that is indicative of the properties of the substrate; characterizing transmission losses of the optical system by splitting the radiation beam into a reference portion and a measurement portion; during a measurement of the reference portion, detecting an illumination profile of the reference portion reflected from a moveable reference mirror in a first position, during a measurement of the measurement portion, detecting an illumination profile of the measurement portion after the radiation beam has traveled through the optical system and detecting the illumination profile of the reference portion reflecting from the reference mirror in a second position, the second position being different than the first position, and comparing the illumination profile of the reference portion to the illumination to the illumination profile of the measurement portion to characterize transmission losses in the optical system; and subtracting the transmission losses from the reflected radiation beam. - View Dependent Claims (11, 12, 13)
-
-
14. An inspection apparatus configured to measure a property of a substrate, comprising:
-
a radiation projector configured to project a radiation beam through an optical system onto the substrate; a detector configured to detect radiation reflected from the substrate; a moveable reference mirror; a data handling unit configured to normalize the detected radiation beam by taking into account the transmission losses from P and S polarized light, wherein the data handling unit characterizes the transmission losses by, splitting the radiation beam into a reference portion and a measurement portion; during a measurement of the reference portion, detecting an illumination profile of the reference portion reflected from a reference mirror in a first position; during a measurement of the measurement portion, detecting an illumination profile of the measurement portion after the radiation beam has traveled through the optical system and detecting the illumination profile of the reference portion reflecting from the reference mirror in a second position, the second position being different than the first position; and comparing the illumination profile of the reference portion to the illumination profile of the measurement portion to characterize the transmission losses in the optical system. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
-
Specification