Optical phase measurement method and system

Patent metadata

Field	Value
Publication number	US-10161885-B2
Application number	US-201515300768-A
Country	US
Kind code	B2
Filing date	Apr 12, 2015
Priority date	Apr 7, 2014
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

A measurement system for use in measuring parameters of a patterned sample is presented. The system comprises: a broadband light source; an optical system configured as an interferometric system; a detection unit; and a control unit. The interferometric system defines illumination and detection channels having a sample arm and a reference arm comprising a reference reflector, and is configured for inducing an optical path difference between the sample and reference arms; the detection unit comprises a configured and operable for detecting a combined light beam formed by a light beam reflected from said reflector and a light beam propagating from a sample's support, and generating measured data indicative of spectral interference pattern formed by at least two spectral interference signatures. The control unit is configured and operable for receiving the measured data and applying a model-based processing to the spectral interference pattern for determining one or more parameters of the pattern in the sample.

First claim

The invention claimed is:

1. A measurement system for use in measuring parameters of a patterned sample, the system comprising: a broadband light source; an optical system configured as an interferometric system; a detection unit; and a control unit; wherein:
the interferometric system defines illumination and detection channels having a sample arm and a reference arm comprising a reference reflector, and is configured to induce an optical path difference between the sample and reference arms, and to combine output of the sample and reference arms into the detection channel for propagation of a combined light beam formed by a light beam reflected from said reference reflector and a light beam propagating from a sample's support;
the detection unit comprises a spectral sensor configured and operable to detect the combined light beam, and generate measured data indicative of spectral interference pattern formed by at least two spectral interference signatures corresponding to at least two different values of the optical path difference between the sample and reference arms; and
said control unit is configured and operable to receive the measured data and apply a model-based processing to the spectral interference pattern for determining one or more parameters of the pattern in the sample.

2. The measurement system of claim 1 , wherein said interferometric system comprises polarizers in the illumination and detection channels.

3. The measurement system of claim 2 , wherein said interferometric system comprises a driving mechanism associated with either one or both of said reference reflector and the sample's support and configured and operable to controllably move at least one of said reference reflector and the sample's support along an optical axis of the interferometric system, to induce the optical path difference between the sample and reference arms.

4. The measurement system of claim 1 , wherein at least one of the sample's support and the reference reflector is oriented with a fixed tilted position with respect to an optical axis of the interferometric system, providing the optical path difference between the sample and reference arms.

5. The measurement system of claim 4 , wherein said reflector is located in a plane parallel to and spaced-apart from a focal plane of an objective lens unit of said interferometric system.

6. The measurement system of claim 4 , wherein said reflector is configured as a retro-reflector assembly.

7. The measurement system of claim 1 , wherein said interferometric system is configured and operable to induce defocusing effect on illuminating light beam propagating along the reference arm towards said reference reflector, providing the optical path difference between the sample and reference arms.

8. The measurement system of claim 1 , wherein the light source is configured and operable to produce illumination in the form of ultra short pulses.

9. An optical system for use in measuring parameters of a patterned sample, the optical system being configured as a spectral interferometer comprising an interferometric system and a detection unit comprising a spectral sensor, wherein:
the interferometric system defining illumination and detection channels having a sample arm and a reference arm comprising a reference reflector, and being configured to induce an optical path difference between the sample and reference arms, and to combine output of the sample and reference arms into the detection channel for propagation therethrough of a combined light beam formed by a light beam reflected from said reference reflector and a light beam propagating from a sample, such that said combined light beam is indicative of spectral interference pattern formed by at least two spectral interference signatures corresponding to at least two values of the optical path differences.

10. The optical system of claim 9 , comprising polarizers accommodated in the illumination and detection channels and configured to provide cross-polarization scheme.

11. The optical system of claim 10 , comprising a mechanism configured and operable to induce the optical path difference between the sample and reference arms.

12. The optical system of claim 11 , wherein said mechanism is configured as a driving mechanism to controllably move either one or both of said reflector and the sample's support along an optical axis of the interferometric system.

13. The optical system of claim 10 , wherein at least one of the sample's support and the reference reflector is oriented with a fixed tilted position with respect to an optical axis of the interferometric system, thereby inducing the optical path difference between the sample and reference arms.

14. The optical system of claim 10 , configured and operable to induce defocusing effect on illuminating light beam propagating along the reference arm towards said reference reflector, providing the optical path difference between the sample and reference arms.

15. The optical system of claim 14 , wherein said reflector is located in a plane parallel to and spaced-apart from a focal plane of an objective lens unit of said interferometric system.

16. The optical system of claim 14 , wherein said reflector is configured as a retro-reflector assembly.

17. A method for use in Optical Critical Dimension (OCD) measurements of parameters of a patterned sample, the method comprising:
directing broadband light through an interferometric optical system having a sample arm and a reference arm with an optical path difference between the sample and reference arms;
detecting, by a spectral sensor, a combined light beam formed by a light beam reflected from a reflector in the reference arms and a light beam propagating from the sample under measurements, and generating measured data indicative of spectral interference pattern comprising spectral phase information and being formed by at least two spectral interference signatures corresponding to at least two different values of the optical path difference between the sample and reference arms; and
applying a model-based processing to the spectral interference pattern and determining one or more parameters of the pattern in the sample.

18. A measurement system for use in measuring parameters of a patterned sample, the measurement system comprising: a broadband light source; an optical system configured as an interferometric system; a detection unit; and a control unit; wherein
the interferometric system defines illumination and detection channels having a sample arm and a reference arm comprising a reference reflector, and comprising one of the following configurations of optical elements adapted to induce an optical path difference between the sample and reference arms without movement of any of said optical elements: (1) the reference reflector is oriented with a fixed tilted position with respect to an optical axis of the interferometric system; (2) the sample's support is oriented with a fixed tilted position with respect to the optical axis of the interferometric system; (3) the reference reflector is located in a plane parallel to and spaced-apart from a focal plane or a plane conjugate to the focal plane of an objective lens unit of the interferometric system inducing defocusing effect on a reference beam propagating along the reference arm; or (4) the reference reflector is configured as a retro-reflector assembly inducing a field shift to the reference beam;
the detection unit comprises a spectral sensor, which is configured and operable to detect a combined light beam formed by a light beam refl

Assignees

• Nova Measuring Instr Ltd

Inventors

• Barak Gilad
• Grossman Danny
• Shafir Dror
• Berlatzky Yoav
• Hainick Yanir

Classifications

• G01B9/02032

  generating a spatial carrier frequency, e.g. by creating lateral or angular offset between reference and object beam (shearing interferometers G01B9/02098) · CPC title

• G01N21/956 Primary

  Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} · CPC title

• G01B11/0675

  using interferometry · CPC title

• G01N2021/8848

  Polarisation of light · CPC title

• G01B9/02072

  by calibration or testing of interferometer · CPC title