Alignment measurement system, lithographic apparatus, and a method to determine alignment of in a lithographic apparatus

Patent metadata

Field	Value
Publication number	US-9280057-B2
Application number	US-201514725023-A
Country	US
Kind code	B2
Filing date	May 29, 2015
Priority date	Sep 13, 2010
Publication date	Mar 8, 2016
Grant date	Mar 8, 2016

Abstract

An alignment measurement system measures an alignment target on an object. A measurement illuminates the target and is reflected. The reflected measurement beam is split and its parts are differently polarized. A detector receives the reflected measurement beam. A processing unit determines alignment on the basis of the measurement beam received by the detector. An alternative arrangement utilizes an optical dispersive fiber to guide a multi-wavelength measurement beam reflected from the object to a detector.

First claim

The invention claimed is:

1. An alignment measurement system for measuring an alignment target on an object, comprising:
an illumination source configured to provide towards the object a measurement beam pulse including light of multiple wavelengths;
a detector system configured to receive a reflected measurement beam pulse after reflection from the object, the detector system comprising a first detector and a dispersive fiber arranged to guide at least a part of the reflected measurement beam pulse towards the first detector so that different wavelengths of the part of the reflected measurement beam pulse are dispersed in the dispersive fiber and reach the first detector at different moments in time; and
a processing unit configured to determine alignment based on the reflected measurement beam pulse received by the detector system.

2. The system of claim 1 , wherein an intensity variation in time for the reflected measurement beam pulse received at the first detector is a function of wavelength.

3. The system of claim 1 , wherein the processing unit is configured to determine an intensity variation response of the different wavelengths of the reflected measurement beam pulse.

4. The system of claim 1 , wherein the illumination source is configured to provide a polarized measurement beam.

5. The system of claim 1 , wherein the illumination source provides a measurement beam comprising multiple wavelengths.

6. The system of claim 1 , wherein the illumination source provides a pulsed measurement beam.

7. The system of claim 1 , wherein the detector system further comprises:
a beam splitting device configured to split the reflected measurement beam pulse into a first beam part and a second beam part, wherein the first detector is configured to receive the first beam part; and
a second detector configured to receive the second beam part.

8. The system of claim 7 , wherein the detector system further comprises a first polarizing device to modify polarization of the first beam part and a second polarizing device to modify polarization of the second beam part, a resulting polarization angle of the first beam part is different than a resulting polarization angle of the second beam part.

9. The system of claim 7 , wherein the dispersive fiber is between the beam splitting device and the first detector and the detector system further comprises a second dispersive fiber between the beam splitting device and the second detector.

10. The system of claim 9 , wherein the first and second detectors are configured to measure intensities of the first and second beam parts, respectively.

11. The system of claim 10 , including an arrangement for subtracting intensities measured by the second detector from intensities measured by the first detector.

12. The system of claim 1 , wherein the detector system comprises an interferometer device.

13. A lithographic apparatus comprising:
an illumination system configured to condition a radiation beam;
a support configured to support a patterning device capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam;
a substrate table configured to hold a substrate to be patterned by the patterned radiation beam;
a projection system configured to project the patterned radiation beam onto a target portion of the substrate; and
an alignment measurement system configured to measure an alignment target on an object, comprising:
an illumination source configured to provide towards the target a measurement beam pulse comprising light of multiple wavelengths,
a detector system configured to receive the measurement beam pulse after reflection from the target, the detector system comprising a detector and a dispersive fiber, the dispersive fiber arranged to guide at least a part of the reflected measurement beam pulse towards the detector so that different wavelengths of the part of the reflected measurement beam pulse are dispersed in the dispersive fiber and reach the detector at different moments in time, and

a processing unit constructed and arranged to determine alignment based on a signal from the detector system.

14. A method to determine alignment of a substrate in a lithographic apparatus, comprising:
illuminating an alignment target on the substrate with a measurement beam pulse including light of multiple wavelengths;
receiving by a detector system a reflected measurement beam pulse after reflection from the target;
guiding at least a part of the reflected measurement beam pulse through a dispersive fiber towards a detector of the detector system so that different wavelengths of the part of the reflected measurement beam pulse are dispersed in the dispersive fiber and reach the first detector at different moments in time; and
determining alignment based on a signal from the detector system.

15. The method of claim 14 , wherein the alignment target is sub-segmented.

16. The method of claim 15 , wherein the alignment target comprises lines and spaces, wherein the lines are sub-segmented.

Assignees

• Asml Netherlands Bv

Inventors

• Bijnen Franciscus Godefridus Casper
• Deckers David
• Musa Sami

Classifications

• G03F7/70141 Primary

  Illumination system adjustment, e.g. adjustments during exposure or alignment during assembly of illumination system · CPC title

• G03F9/7088 Primary

  Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection · CPC title

• G01B11/272

  using photoelectric detection means · CPC title

• G03F9/7046

  Strategy, e.g. mark, sensor or wavelength selection · CPC title

• G01D5/344

  using polarisation (G01D5/35303 takes precedence) · CPC title