Inspection method and apparatus, lithographic apparatus, lithographic processing cell and device manufacturing method

• US 20080279442A1
• Filed: 05/09/2007
• Published: 11/13/2008
• Est. Priority Date: 05/09/2007
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Den Boef, Arie Jeffrey, Cramer, Hugo Augustinus Joseph, Dusa, Mircea, Setija, Irwan Dani
• Granted Patent: US 8,189,195 B2
• Time in Patent Office: Days
• US Class Current: 382/144
• CPC Class Codes: G03F 1/84 Inspecting
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects

Abstract

A method of measuring a property of a substrate includes generating a patterned mask configured to cause a radiation beam passing through the mask to acquire the pattern, simulating radiating the substrate with a patterned radiation beam that has been patterned using the mask to obtain a simulated pattern, determining at least one location of the simulated pattern that is prone to patterning errors, and irradiating the substrate with the patterned radiation beam using a lithographic process. The method also includes measuring an accuracy of at least one property of the at least one location of the pattern on the substrate that has been determined as being prone to patterning errors, and adjusting the lithographic process according to the measuring.

Claims

1. A method of measuring a property of a substrate, the method comprising:

generating a patterned mask configured to cause a radiation beam passing through the mask to acquire the pattern;

simulating radiating the substrate with a patterned radiation beam that has been patterned using the mask to obtain a simulated pattern;

determining at least one location of the simulated pattern that is prone to patterning errors;

irradiating the substrate with the patterned radiation beam using a lithographic process;

measuring an accuracy of at least one property of the at least one location of the pattern on the substrate that has been determined as being prone to patterning errors; and

adjusting the lithographic process according to said measuring.

2. A method according to claim 1, wherein said measuring the accuracy is carried out using an optical technique.

3. A method according to claim 2, wherein the optical technique comprises comparing diffraction patterns of a radiation beam reflected from the surface of the substrate with diffraction patterns of known substrate surface properties.

4. A method according to claim 1, said measuring comprises:

choosing a measurement spot corresponding to a location of the pattern that has been determined as being prone to patterning errors;

irradiating the measurement spot on the pattern on the substrate with a first radiation source;

irradiating, with a second radiation source, a portion of the pattern on the substrate that is larger than the measurement spot irradiated by the first radiation source;

detecting radiation that is reflected from the measurement spot and the portion of the pattern with a first detector and outputting an image of the relative positions of the measurement spot and the portion of the pattern;

comparing the position of the measurement spot with respect to the portion of the pattern and outputting a value of the position of the measurement spot relative to the portion of the pattern;

detecting radiation from the first radiation source having been diffracted from the measurement spot using a second detector and outputting a diffraction spectrum associated with the pattern; and

reconstructing the pattern within the measurement spot using the image of the pattern and the value of the position of the measurement spot relative to the portion of the pattern.

5. An inspection apparatus configured to measure a property of a substrate, the inspection apparatus comprising:

a first radiation source configured to irradiate a measurement spot on a patterned target of a substrate;

a second radiation source configured to irradiate an area of the patterned target that is larger than the measurement spot;

a first detector configured to detect radiation having been reflected from the measurement spot and radiation having been reflected from the area of the patterned target, and to output an image of the relative positions of the measurement spot and the area of the patterned target;

an image processor configured to receive the output of the first detector, to compare the position of the measurement spot with respect to the area of the patterned target, and to output a value of the position of the measurement spot relative to the area of the patterned target;

a second detector configured to detect radiation from the first radiation source having been diffracted from the measurement spot, and to output a diffraction spectrum corresponding to the patterned target; and

a processor configured to process the output of the image processor and the output of the second detector to reconstruct the pattern of the patterned target within the measurement spot.

6. An inspection apparatus according to claim 5, wherein the image processor is configured to compare the output of the first detector with stored values of measurement spot positions to determine which of the stored values most closely matches the output of the first detector, and to output the best match value.

7. An inspection apparatus according to claim 5, wherein the processor is configured to compare the output of the image processor and the output of the second detector with stored values of patterned targets in order to determine which of the stored values most closely matches the output of the second detector in conjunction with the relative position output of the image processor to obtain a best match reconstruction value.

8. An inspection apparatus according to claim 5, wherein the image processor is configured to determine the position of the measurement spot relative to a second spot on the patterned target, the second spot being a predetermined spot that is known to be sensitive to errors in production of the pattern.

9. An inspection apparatus according to claim 5, wherein the first radiation source comprises a laser.

10. An inspection apparatus according to claim 9, wherein the laser is tunable.

11. An inspection apparatus according to claim 10, wherein the laser comprises a super-continuum laser and an acousto-optic tunable filter.

12. An inspection apparatus according to claim 5, further comprising a high numerical aperture objective configured to focus a light beam from the first light source onto the patterned target of the substrate.

13. An inspection apparatus according to claim 5, wherein the measurement spot size is of the order of about 300 nm.

14. An inspection apparatus according to claim 5 wherein the second radiation source is an extended light source.

15. An inspection apparatus according to claim 14, wherein the second radiation source is an LED.

16. An inspection apparatus according to claim 14, wherein the second radiation source is a white-light LED.

17. An inspection apparatus according to claim 5, wherein the second radiation source is pulsed.

18. An inspection apparatus according to claim 17, wherein the second radiation source is switched on and off in order to create the pulse.

19. An inspection apparatus according to claim 18, further comprising a shutter configured alternately to allow and to prevent radiation from the second radiation source from reaching the substrate.

20. An inspection apparatus according to claim 5, further comprising a timer and controller configured to prevent the second radiation source from irradiating the substrate while the second detector is detecting diffracted radiation from the substrate such that the second detector detects only radiation from the first radiation source.

21. An inspection apparatus according to claim 5, further comprising a feedback system configured to switch the second radiation source off during the acquisition of the diffracted radiation beams by the second detector.

22. An inspection apparatus according to claim 21, wherein the duration of the radiation beam acquisition by the second detector, during which the second radiation source is switched off, is approximately 0.1 ms.

23. An inspection apparatus according to claim 5, configured to inspect a non-periodic pattern.

24. An inspection apparatus according to claim 5, further comprising a color filter between the substrate and the first detector such that the detected measurement spot is filtered.

25. An inspection apparatus according to claim 5, wherein the acquisition time of a measurement spot by the first detector is less than about 1 ms.

26. An inspection apparatus according to claim 5, wherein the inspection apparatus is configured to acquire a series of radiation measurements for a plurality of locations of the measurement spot.

27. An inspection apparatus according to claim 26, further configured to move the first radiation source in order to change the measurement spot position relative to the patterned target position.

28. An inspection apparatus according to claim 26, further configured to move the substrate in order to change the relative position of the measurement spot with respect to the patterned target.

29. An inspection apparatus according to claim 28, further comprising a substrate table configured to support a substrate, wherein the inspection apparatus is configured to scan the substrate table to move the substrate.

30. A method of measuring a property of a substrate, the method comprising:

irradiating a measurement spot on a patterned target on a substrate with a first radiation source;

irradiating, with a second radiation source, a portion of the patterned target on the substrate that is larger than the measurement spot irradiated by the first radiation source;

detecting radiation that is reflected from the measurement spot and the portion of the patterned target with a first detector and outputting an image of the relative positions of the measurement spot and the portion of the patterned target;

comparing the position of the measurement spot with respect to the portion of the patterned target and outputting a value of the position of the measurement spot relative to the portion of the patterned target;

detecting radiation from the first radiation source having been diffracted from the measurement spot using a second detector and outputting a diffraction spectrum associated with the patterned target; and

reconstructing the pattern of the patterned target within the measurement spot using the image of the patterned target and the value of the position of the measurement spot relative to the portion of the patterned target.

31. A lithographic apparatus configured to measure a property of a substrate, the lithographic apparatus comprising:

a first radiation source configured to irradiate a measurement spot on a patterned target of a substrate;

a second radiation source configured to irradiate an area of the patterned target that is larger than the measurement spot;

a first detector configured to detect radiation having been reflected from the measurement spot and radiation having been reflected from the area of the patterned target and to output an image of the relative positions of the measurement spot and the area of the patterned target;

an image processor configured to receive the output of the first detector, to compare the position of the measurement spot with respect to the area of the patterned target and to output a value of the position of the measurement spot relative to the area of the patterned target;

a second detector configured to detect radiation from the first radiation source having been diffracted from the measurement spot and outputting a diffraction spectrum corresponding to the patterned target; and

a processor for processing the output of the image processor and the output of the second detector to reconstruct the pattern of the patterned target within the measurement spot.

32. A lithographic cell configured to measure a property of a substrate, the lithographic cell comprising:

a first radiation source configured to irradiate a measurement spot on a patterned target of a substrate;

a second radiation source configured to irradiate an area of the patterned target that is larger than the measurement spot;

a first detector configured to detect radiation having been reflected from the measurement spot and radiation having been reflected from the area of the patterned target and to output an image of the relative positions of the measurement spot and the area of the patterned target;

an image processor configured to receive the output of the first detector, to compare the position of the measurement spot with respect to the area of the patterned target and to output a value of the position of the measurement spot relative to the area of the patterned target;

a second detector configured to detect radiation from the first radiation source having been diffracted from the measurement spot and outputting a diffraction spectrum corresponding to the patterned target; and

a processor for processing the output of the image processor and the output of the second detector to reconstruct the pattern of the patterned target within the measurement spot.

33. A device manufacturing method, comprising:

simulating radiating a substrate with a patterned radiation beam that has been patterned with a patterning device to obtain a simulated pattern;

determining at least one location of the simulated pattern that is prone to patterning errors;

irradiating the substrate with the patterned radiation beam using a lithographic process;

measuring an accuracy of at least one property of the at least one location of the pattern on the substrate that has been determined as being prone to patterning errors; and

adjusting the lithographic process according to said measuring.

34. A method according to claim 33, further comprising

projecting the patterned radiation beam onto a target portion of the substrate after said adjusting.