Optical scatterometry of asymmetric lines and structures
A method for analyzing asymmetric structures (including isolated and periodic structures) includes a split detector for use in a broadband spectrometer. The split has detector has separate right and left halves. By independently measuring and comparing the right and left scattered rays, information about asymmetries can be determined.
1. A method of optically inspecting and evaluating a subject including a potentially asymmetric structure, the method comprising:
(a) directing an optical beam to be reflected by the subject;
(b) measuring light reflected by the potentially asymmetric structure at two detector locations where the two detector locations are chosen to detect asymmetries in the reflected optical beam; and
(c) analyzing the measurements made in step b to obtain information about a direction of asymmetry of the potentially asymmetric structure.
2. A method as recited in claim 1 , which further comprises:
(d) separately measuring light that is specularly and non-specularly reflected by the potentially asymmetric structure; and
(e) analyzing the measurements made in steps d to obtain information about the direction of asymmetry of the potentially asymmetric structure.
3. A method of optically inspecting and evaluating a subject including a potentially asymmetric structure, the method comprising:
(a) directing an optical beam to be reflected by the subject;
(b) separately measuring light that is specularly and non-specularly reflected by the potentially asymmetric structure; and
(c) analyzing the measurements made in step b to obtain information about a direction of asymmetry of the potentially asymmetric structure.
4. A method as recited in claim 3 , which further comprises:
(d) measuring light reflected by the potentially asymmetric structure at two detector locations where the two detector locations are chosen to detect asymmetries in the reflected optical beam; and
(e) analyzing the measurements made in step d to obtain information about the direction of asymmetry of the potentially asymmetric structure.
5. An apparatus for evaluating asymmetric line structures on a sample comprising:
a source of light for generating a probe beam;
optics for focusing the beam on the line structure on the sample;
a detector having a least two independent sensor regions and oriented to detect asymmetries in the reflection and scattering of the probe beam light from the sample, each sensor region generating output signals; and
a processor for evaluating a direction of asymmetry in the geometry of the sample based on the output signals.
6. An apparatus for evaluating asymmetric line structures on a sample comprising:
a source of light for generating a probe beam;
optics for focusing the beam on the line structure on the sample;
a detector having a least two independent sensor regions and oriented to detect asymmetries in the reflection and scattering of the probe beam light from the sample, each sensor region generating output signals; and
a processor for evaluating the asymmetries in the geometry of the sample based on the output signals;
wherein the detector includes a split detector having two halves and oriented to monitor radial asymmetries in the reflected probe beam.
7. An apparatus for evaluating asymmetric line structures on a sample comprising:
a source of light for generating a probe beam;
optics for focusing the beam on the line structure on the sample;
a first detector positioned in the path of the specularly reflected probe beam and generating first output signals in response thereto;
a second detector positioned to measure only scattered light outside of the path of the specularly reflected beam and generating second output signals; and
a processor for evaluating a direction of asymmetry in the geometry of the sample based on the first and second output signals.
8. An apparatus for evaluating asymmetric line structures on a sample comprising:
a source of light for generating a probe beam;
optics for focusing the beam on the line structure on the sample with a spread of angles of incidence;
a pair of orthogonal related detector arrays positioned in the path of the specularly reflected probe beam and generating output signals in response thereto; and
a processor containing instructions to evaluate a direction of asymmetry in the geometry of the sample based on the output signals from the arrays.