Calibration method and apparatus
First Claim
1. A method of calibration of an optical inspection apparatus for inspecting a target, the optical inspection apparatus comprising at least one ingoing optical system for illuminating the target and at least one outgoing optical system for delivering radiation from the target to a detector, the method comprising:
- using the ingoing optical system and the outgoing optical system in a first arrangement to obtain a first measurement of radiation in an outgoing direction, the measured radiation in the outgoing direction in the first arrangement being a combination of radiation illuminating a target from a first plurality of ingoing directions;
using the ingoing optical system and the outgoing optical system in a second arrangement to obtain a second measurement of radiation in the outgoing direction, the measured radiation in the outgoing direction in the second arrangement being a different combination of radiation illuminating a target from a second plurality of ingoing directions; and
using the first and second measurements and modeling a difference between the first and second arrangements to determine separately properties of the ingoing and outgoing optical systems.
1 Assignment
0 Petitions
Accused Products
Abstract
Calibration of an angularly resolved scatterometer is performed by measuring a target in two or more different arrangements. The different arrangements cause radiation being measured in an outgoing direction to be different combinations of radiation illuminating the target from ingoing directions. A reference mirror measurement may also be performed. The measurements and modeling of the difference between the first and second arrangements is used to estimate separately properties of the ingoing and outgoing optical systems. The modeling may account for symmetry of the respective periodic target. The modeling typically accounts for polarizing effects of the ingoing optical elements, the outgoing optical elements and the respective periodic target. The polarizing effects may be described in the modeling by Jones calculus or Mueller calculus. The modeling may include a parameterization in terms of basis functions such as Zernike polynomials.
-
Citations
22 Claims
-
1. A method of calibration of an optical inspection apparatus for inspecting a target, the optical inspection apparatus comprising at least one ingoing optical system for illuminating the target and at least one outgoing optical system for delivering radiation from the target to a detector, the method comprising:
-
using the ingoing optical system and the outgoing optical system in a first arrangement to obtain a first measurement of radiation in an outgoing direction, the measured radiation in the outgoing direction in the first arrangement being a combination of radiation illuminating a target from a first plurality of ingoing directions; using the ingoing optical system and the outgoing optical system in a second arrangement to obtain a second measurement of radiation in the outgoing direction, the measured radiation in the outgoing direction in the second arrangement being a different combination of radiation illuminating a target from a second plurality of ingoing directions; and using the first and second measurements and modeling a difference between the first and second arrangements to determine separately properties of the ingoing and outgoing optical systems. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
-
-
12. An optical inspection apparatus comprising:
-
an ingoing optical system configured to illuminate a target; an outgoing optical system configured to deliver radiation from the target to a detector; and a processor configured to perform calibration by; using the ingoing optical system and the outgoing optical system in a first arrangement to obtain a first measurement of radiation in an outgoing direction, the measured radiation in the outgoing direction in the first arrangement being a combination of radiation illuminating a target from a first plurality of ingoing directions; using the ingoing optical system and the outgoing optical system in a second arrangement to obtain a second measurement of radiation in the outgoing direction, the measured radiation in the outgoing direction in the second arrangement being a different combination of radiation illuminating a target from a second plurality of ingoing directions; and using the first and second measurements and modeling a difference between the first and second arrangements to determine separately properties of the ingoing and outgoing optical systems. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
-
Specification