Interferometric roll-off measurement using a static fringe pattern

Patent metadata

Field	Value
Publication number	US-9829310-B2
Application number	US-201615198661-A
Country	US
Kind code	B2
Filing date	Jun 30, 2016
Priority date	Jun 30, 2015
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

An apparatus for measuring the surface contour of a target area of a substrate has a light source to emit a measurement light beam. A beam splitting element defines a measurement axis and a reference axis. A substrate holder disposes the target area along the measurement axis and tilted away from normal incidence, about a tilt axis that orthogonally intersects the measurement axis, according to a predetermined tilt angle that is a function of the measurement light beam wavelength. An imaging sensor records a fringe pattern generated from the measurement light beam and a reference light beam. A computer extracts frequency profiles from the recorded fringe pattern, each profile taken in a direction that is orthogonal to the direction of the tilt axis, wherein the programmed instructions further compute changes in the contour of the target area surface according to the frequency profiles.

First claim

What is claimed is:

1. An apparatus for measuring the surface contour of a target area of a substrate, the apparatus comprising:
a light source energizable to emit a measurement light beam;
a beam splitting element that defines a measurement axis and a reference axis;
a substrate holder that disposes the target area of the substrate along the measurement axis and tilted away from normal incidence, about a tilt axis that orthogonally intersects the measurement axis, according to a predetermined tilt angle that is a function of the measurement light beam wavelength;
an imaging sensor energizable to record a fringe pattern for the target area, the fringe pattern generated from the measurement light beam and a reference light beam from the reference axis; and
a computer in signal communication with the imaging sensor and programmed with instructions to extract a plurality of frequency profiles from the recorded fringe pattern, each profile taken in a direction that is substantially orthogonal to the direction of the tilt axis, wherein the programmed instructions further compute changes in the contour of the target area surface according to the frequency profiles.

2. The apparatus of claim 1 wherein the light source is a solid-state light source.

3. The apparatus of claim 1 wherein the light source is a light emitting diode and further comprising a spectral filter in the path of light from the light source.

4. The apparatus of claim 1 wherein the substrate holder is further actuable to rotate the substrate for measurement of a plurality of target areas.

5. The apparatus of claim 1 further comprising an actuator for focus adjustment along the measurement axis.

6. The apparatus of claim 1 wherein the target area is an edge portion of the substrate.

7. The apparatus of claim 1 wherein the substrate is flat.

8. The apparatus of claim 1 wherein the image sensor comprises an array of pixels arranged in rows and columns and wherein the rows are aligned with the tilt axis.

9. The apparatus of claim 1 wherein the substrate holder rotates the substrate during recording by the imaging sensor.

10. An apparatus for measuring the surface contour of a perimeter portion of a substrate, the apparatus comprising:
a light source energizable to emit a measurement light beam;
an interferometer having a measurement axis and a reference axis;
a substrate holder that disposes the perimeter portion of the substrate along the measurement axis and tilted away from normal incidence, about a tilt axis that orthogonally intersects the measurement axis, wherein the tilt axis is orthogonal to an edge of the perimeter portion, according to a predetermined tilt angle that is a function of the measurement light beam wavelength;
an imaging sensor energizable to record a fringe pattern for the perimeter portion of the substrate, the fringe pattern generated from the measurement light beam and a reference light beam from the reference axis; and
a computer in signal communication with the imaging sensor and programmed with instructions to extract a carrier wave from the recorded fringe pattern, taken in a direction that is substantially orthogonal to the direction of the tilt axis, wherein the programmed instructions further compute surface contour measurements according to changes in the phase of the carrier wave.

11. The apparatus of claim 10 wherein the light source is a solid-state light source and further comprising a spectral filter for the emitted light.

12. The apparatus of claim 10 wherein the interferometer comprises a Michelson objective.

13. The apparatus of claim 10 wherein the interferometer comprises a Mirau objective.

14. The apparatus of claim 10 wherein the programmed instructions further display surface contour measurements according to changes in the phase of the carrier wave.

15. A method for measuring the surface contour of a target area of a substrate, the method executed at least in part by a computer and comprising:
energizing a light source to emit a measurement light beam;
directing the measurement light beam to an interferometer having a measurement axis and a reference axis;
disposing the target area of the substrate along the measurement axis and tilted away from normal incidence, about a tilt axis that orthogonally intersects the measurement axis, according to a predetermined tilt angle that is a function of the measurement light beam wavelength;
recording a fringe pattern for the target area, the fringe pattern generated from the measurement light beam and a reference light beam from the reference axis;
extracting a plurality of frequency profiles from the recorded fringe pattern, each profile taken in a direction that is substantially orthogonal to the direction of the tilt axis; and
computing changes in the contour of the target area surface according to the frequency profiles.

16. The method of claim 15 further comprising automatically adjusting focus of the interferometer along the measurement axis according to a change in height of the substrate surface.

17. The method of claim 15 further comprising displaying the contour of the target area surface according to the computed changes.

18. The method of claim 15 wherein computing changes in the contour comprises applying Fourier analysis to the plurality of extracted frequency profiles.

19. The method of claim 15 wherein the target area is a first target area and further comprising rotating the substrate to measure a second target area using the same sequence of steps.

20. The method of claim 15 wherein the target area lies along the perimeter of the substrate.

Assignees

• Corning Inc

Inventors

• Bean Alexander Timothy
• Dunn Thomas James
• Lee Christopher Alan
• Tronolone Mark Joseph

Classifications

• G01B9/02044

  Imaging in the frequency domain, e.g. by using a spectrometer · CPC title

• G06T7/0006

  using a design-rule based approach · CPC title

• G01N21/9503 Primary

  Wafer edge inspection · CPC title

• G01B11/2441 Primary

  using interferometry · CPC title

• G06T7/64

  of convexity or concavity · CPC title