Optical phase measurement method and system

Patent metadata

Field	Value
Publication number	US-2017016835-A1
Application number	US-201515300768-A
Country	US
Kind code	A1
Filing date	Apr 12, 2015
Priority date	Apr 7, 2014
Publication date	Jan 19, 2017
Grant date	—

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

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 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; and said 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.

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 mechanism for inducing the optical path difference between the sample and reference arms, said mechanism comprising a driving unit for controllably moving either one or both of said reflector and the sample's support along an optical axis of the interferometric system.

4 . The measurement system of claim 1 or 2 , wherein at least one of the sample's support and the 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.

5 . The measurement system of claim 1 or 2 , wherein said interferometric system is configured and operable for inducing defocusing effect on illuminating light beam propagating along the reference arms towards said reflector, thereby inducing the optical path difference between the sample and reference arms.

6 . 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.

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

8 . The measurement system of any one of the preceding claims, wherein the light source is configured and operable for producing 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 interferometric system defining illumination and detection channels having a sample arm and a reference arm comprising a reference reflector, and being configured for inducing an optical path difference between the sample and reference arms, such that combined light beam, propagating along the detection channel to a spectrometer, is formed by a light beam reflected from said reflector and a light beam propagating from a sample and is indicative of spectral interference pattern formed by at least two spectral interference signatures corresponding to at least two 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 for inducing the optical path difference between the sample and reference arms

12 . The optical system of claim 11 , wherein said mechanism comprises a driving unit for controllably moving 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 11 , wherein at least one of the sample's support and the 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 11 , configured and operable for inducing defocusing effect on illuminating light beam propagating along the reference arm towards said reflector, thereby inducing 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 measuring 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 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 formed by at least two spectral interference signatures; and applying a model-based processing to the spectral interference pattern and determining one or more parameters of the pattern in the sample.

Assignees

• Nova Measuring Instr Ltd

Inventors

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

Classifications

• G01B9/0209

  Low-coherence interferometers · CPC title

• G01B2210/56

  Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth · 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

• G01B2290/70

  Using polarization in the interferometer · CPC title

• G01B9/02007

  Two or more frequencies or sources used for interferometric measurement (using only beat G01B9/02003) · CPC title