Spectral Feature Metrology of a Pulsed Light Beam

Patent metadata

Field	Value
Publication number	US-2016341602-A1
Application number	US-201514720207-A
Country	US
Kind code	A1
Filing date	May 22, 2015
Priority date	May 22, 2015
Publication date	Nov 24, 2016
Grant date	—

Abstract

A metrology system includes an optical frequency separation apparatus in the path of the pulsed light beam and configured to interact with the pulsed light beam and output a plurality of spatial components that correspond to the spectral components of the pulsed light beam; a plurality of sensing regions that receive and sense the output spatial components; and a control system connected to an output of each sensing region. The control system is configured to: measure, for each sensing region output, a property of the output spatial components from the optical frequency separation apparatus for one or more pulses; analyze the measured properties including averaging the measured properties to calculate an estimate of the spectral feature of the pulsed light beam; and determine whether the estimated spectral feature of the pulsed light beam is within an acceptable range of values of spectral features.

First claim

What is claimed is:

1 . A metrology system for measuring a spectral feature of a pulsed light beam, the system comprising:
an optical frequency separation apparatus in the path of the pulsed light beam and configured to interact with the pulsed light beam and output a plurality of spatial components that correspond to the spectral components of the pulsed light beam; a plurality of sensing regions that receive and sense the output spatial components; and a control system connected to an output of each sensing region and configured to: measure, for each sensing region output, a property of the output spatial components from the optical frequency separation apparatus for one or more pulses; analyze the measured properties including averaging the measured properties to calculate an estimate of the spectral feature of the pulsed light beam; and determine whether the estimated spectral feature of the pulsed light beam is within an acceptable range of values of spectral features.

2 . The system of claim 1 , wherein the optical frequency separation apparatus comprises a plurality of optical frequency separation devices.

3 . The system of claim 2 , further comprising a beam separation device that divides the pulsed light beam into a plurality of pulsed light beams, each of the divided pulsed light beams being directed to a respective optical frequency separation device.

4 . The system of claim 2 , wherein each optical frequency separation device includes an etalon.

5 . The system of claim 2 , wherein each sensing region of the plurality of sensing regions is formed on a distinct sensor placed at the output of one of the optical frequency separation devices.

6 . The system of claim 2 , wherein each optical frequency separation device has the same response function as the other optical frequency separation devices.

7 . The system of claim 1 , wherein the optical frequency separation apparatus comprises one or more etalons.

8 . The system of claim 1 , further comprising a beam separation device in the path between a source that produces the light beam and a photolithography exposure apparatus, wherein the beam separation device:
directs a first percentage of the light beam toward the optical frequency separation apparatus, and directs a second percentage of the light beam along the path toward the photolithography exposure apparatus.

9 . The system of claim 1 , wherein the light beam has a plurality of wavelengths, at least some being in the deep ultraviolet range.

10 . The system of claim 1 , wherein each sensing region has the same performance parameters as the other sensing regions of the plurality.

11 . The system of claim 1 , wherein the spectral feature is a bandwidth of the pulsed light beam.

12 . The system of claim 1 , further comprising a spectral feature selection system optically connected to the pulsed light beam, wherein:
the control system is connected to the spectral feature selection system; and if the control system determines that the estimated spectral feature of the pulsed light beam is outside the acceptable range, then the control system is configured to send an adjustment signal to the spectral feature selection system to modify the spectral feature of the pulsed light beam.

13 . The system of claim 1 , wherein the range of one or more pulses is a single pulse.

14 . The system of claim 1 , wherein averaging the measured properties comprises determining which measured property is the most accurate representation of the spectral feature and calculating the spectral feature of the pulsed light beam comprises selecting the measured property that most accurately represents the spectral feature.

15 . The system of claim 1 , wherein:
the control system is configured to determine which of the measured properties fall inside a target range of values, and the control system averages the measured properties to calculate an estimate by averaging only those measured properties that fall inside the target range of values.

16 . The system of claim 1 , wherein averaging the measured properties comprises performing a weighted average of the measured properties and calculating the estimate of the spectral feature of the pulsed light beam comprises selecting the weighted average as the spectral feature estimate.

17 . The system of claim 1 , wherein the optical frequency separation apparatus comprises a single optical frequency separation device, and the plurality of sensing regions are formed on a single two-dimensional sensor that receives one or more entire spectral components.

18 . The system of claim 1 , wherein each sensing region of the plurality of sensing regions has a sensing axis that is perpendicular to an optical axis of the outputted spatial components.

19 . The system of claim 1 , wherein each sensing region of the plurality of sensing regions is formed at a distinct location of a single sensor placed at the output of the optical frequency separation apparatus.

20 . A method for measuring a spectral feature of a pulsed light beam, the method comprising:
interacting the pulsed light beam with an optical frequency separation apparatus that outputs a plurality of spatial components that correspond to the spectral components of the pulsed light beam; sensing the plurality of spatial components at each of a plurality of sensing regions placed in the path of the output spatial components; measuring, at each of the sensing regions, a property of the output spatial components for one or more pulses of the pulsed light beam; analyzing the measured properties including averaging the measured properties to calculate an estimate of the spectral feature of the pulsed light beam; and determining whether the estimated spectral feature of the pulsed light beam is within an acceptable range of spectral features.

21 . The method of claim 20 , wherein sensing the plurality of spatial components at each of the plurality of sensing regions comprises sensing the plurality of spatial components at each of the plurality of sensing regions simultaneously for the same pulse of the light beam.

22 . The method of claim 20 , further comprising, if it is determined that the estimated spectral feature of the pulsed light beam is outside the acceptable range, then sending an adjustment signal to a spectral feature selection system to modify the spectral feature of the pulsed light beam.

23 . The method of claim 20 , wherein averaging the measured properties comprises determining which measured property is the most accurate representation of the spectral feature and calculating the spectral feature of the pulsed light beam comprises selecting the measured property that most accurately represents the spectral feature.

24 . The method of claim 20 , further comprising determining which of the measured properties fall inside a standard range of values,
wherein averaging the measured properties to calculate an estimate comprises averaging only those measured properties that fall inside the standard range of values.

25 . The method of claim 20 , wherein averaging the measured properties comprises performing a weighted average of the measured properties and calculating the estimate of the spectral feature of the pulsed light beam comprises selecting the weighted average as the spectral feature estimate.

26 . The method of claim 20 , wherein measuring, at each

Assignees

• Cymer LLC

Inventors

• Thornes Joshua

Classifications

• G01J9/00

  Measuring optical phase difference (devices or arrangements for controlling the phase of light beams G02F1/01); Determining degree of coherence; Measuring optical wavelength (spectrometry G01J3/00) · CPC title

• G01J3/26 Primary

  using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters · CPC title

• G01J3/027

  Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation · CPC title

• G01J3/18

  using diffraction elements, e.g. grating (gratings per se G02B) · CPC title

• G01J3/2803 Primary

  using photoelectric array detector · CPC title