System and method for lithography process monitoring and control

• US 6,969,864 B2
• Filed: 06/21/2004
• Issued: 11/29/2005
• Est. Priority Date: 06/07/2002
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: Brion Technologies Incorporated (ASML Holding NV)
• Inventors: Ye, Jun, Chen, Xun, Pease, R. Fabian W.
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US10/873,539
• Publication Number:
  US 20040232313A1
• Time in Patent Office: 526 Days
• Field of Search: 250/559.4, 250/559.3, 250/208.1, 250/548, 250/559.45, 356/399, 356/400, 356/401, 355/53, 355/55
• US Class Current: 250/559.4
• CPC Class Codes: G03F 7/70591 Testing optical components
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects
• CPC Class Codes: G03F 7/7085 Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load

Abstract

A system and sensor for measuring, inspecting, characterizing, evaluating and/or controlling optical lithographic equipment and/or materials used therewith, for example, photomasks. In one embodiment, the system and sensor measures, collects and/or detects an aerial image (or portion thereof) produced or generated by the interaction between the photomask and lithographic equipment. An image sensor unit may measure, collect, sense and/or detect the aerial image in situ—that is, the aerial image at the wafer plane produced, in part, by a production-type photomask (i.e., a wafer having integrated circuits formed therein/thereon) and/or by associated lithographic equipment used, or to be used, to manufacture of integrated circuits. A processing unit, coupled to the image sensor unit, may generate image data which is representative of the aerial image by, in one embodiment, interleaving the intensity of light sampled by each sensor cell at the plurality of location of the platform. Notably, many inventions/embodiments are disclosed herein.

Claims

1. A photomask inspection system to detect defects in a photomask, wherein an image of the photomask is produced on a wafer plane by an optical system having a platform, the system comprising:

an image sensor unit capable of being disposed on or the platform, the image sensor unit includes;

a sensor array, capable of being located in the wafer plane, including a plurality of sensor cells wherein each sensor cell includes an active area to sample the intensity of light of a predetermined wavelength that is incident thereon and wherein, at discrete locations relative to the image of the photomask produced on the wafer plane, the sensor cells sample the intensity of light; and

a film, disposed over selected portions of the active areas of the plurality of sensor cells, to increase the spatial resolution of each sensor cell wherein the film is comprised of a material that impedes passage of light of the predetermined wavelength; and

a first processing unit, coupled to the image sensor unit, to compare data which is representative of the intensity of light sampled by a plurality of sensor cells at the discrete locations to associated data of a mask pattern design database, wherein the mask pattern design database includes data which is representative of the features on the photomask.

2. The system of claim 1 wherein the image sensor unit further includes a substrate having a wafer or wafer-like shaped profile, wherein the sensor array is disposed on or in the substrate and wherein the substrate is capable of being disposed on the platform.

3. The system of claim 1 wherein the film is disposed between the active areas of the sensor cells and a protective outer layer of the sensor array and includes a plurality of apertures which are arranged such that one aperture of the plurality of apertures overlies a corresponding active area of a corresponding sensor cell to expose a portion of the active area of the corresponding sensor cell and wherein light of the predetermined wavelength is capable of being sensed by the portion of the active area that is exposed by the corresponding aperture.

4. The system of claim 1 wherein the film is disposed on a protective outer layer of the sensor array and includes a plurality of apertures which are arranged such that one aperture of the plurality of apertures overlies a corresponding active area of a corresponding sensor cell to expose a portion of the active area of the corresponding sensor cell and wherein light of the predetermined wavelength is capable of being sensed by the portion of the active area that is exposed by the corresponding aperture.

5. The system of claim 1 wherein the mask pattern design database is comprised of intensity data.

6. The system of claim 1 wherein the mask pattern design database includes polygon data.

7. The system of claim 6 wherein the first processing unit converts the polygon data to associated intensity data.

8. The system of claim 1 wherein the first processing unit converts the data which is representative of the intensity of light sampled by the plurality of sensor cells at each discrete location to associated polygon data and wherein the mask pattern design database is comprised of polygon data.

9. The system of claim 1 further including a second processing unit to convert polygon data of a first design database to the mask pattern design database comprised of intensity data wherein the intensity data for each location corresponds to the polygon data for the associated location.

10. The system of claim 1 wherein the first processing unit generates an aerial image of at least a portion of the photomask by interleaving the intensity data sampled by a plurality of sensor cells at discrete locations.

11. The system of claim 10 wherein the first processing unit compares the aerial image of at least the portion of the photomask with a simulated aerial image of the photomask that is generated using the mask pattern design database.

12. The system of claim 1 wherein the image sensor unit further includes:

a substrate that is capable of being disposed on the platform, wherein the sensor array is disposed on or in the substrate; and

a processor to instruct the sensor array when to sample the intensity of light.

13. The system of claim 1 wherein the photomask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of a design-target.

14. The system of claim 1 wherein the photomask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of an after-OPC or after-PSM decoration pattern.

15. The system of claim 1 wherein the photomask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of a design-target and data which is representative of an after-OPC or after-PSM decoration pattern.

16. A photomask inspection system to detect defects in a photomask, wherein an image of the photomask is produced on a wafer plane by an optical system having a platform, the system comprising:

an image sensor unit capable of being disposed on or the platform, the image sensor unit includes;

a sensor array, capable of being located in the wafer plane, including a plurality of sensor cells wherein each sensor cell includes an active area to sample the intensity of light of a predetermined wavelength that is incident thereon and wherein, at discrete locations relative to the image of the photomask produced on the wafer plane, the sensor cells sample the intensity of light; and

a film, disposed over selected portions of the active areas of the plurality of sensor cells, to increase the spatial resolution of each sensor cell wherein the film is comprised of a material that impedes passage of light of the predetermined wavelength; and

a first processing unit, coupled to the image sensor unit, to compare (i) data which is representative of the intensity of light sampled by sensor cells at a first set of discrete locations corresponding to a first area of a wafer disposed in the wafer plane to (ii) data which is representative of the intensity of light sampled by sensor cells at a second set of discrete locations corresponding to a second area of the wafer disposed in the wafer plane.

17. The system of claim 16 wherein the image sensor unit further includes a substrate having a wafer or wafer-like shaped profile, wherein the sensor array is disposed on or in the substrate and wherein the substrate is capable of being disposed on the platform.

18. The system of claim 16 wherein the film is disposed between the active areas of the sensor cells and a protective outer layer of the sensor array and includes a plurality of apertures which are arranged such that one aperture of the plurality of apertures overlies a corresponding active area of a corresponding sensor cell to expose a portion of the active area of the corresponding sensor cell and wherein light of the predetermined wavelength is capable of being sensed by the portion of the active area that is exposed by the corresponding aperture.

19. The system of claim 16 wherein the film is disposed on a protective outer layer of the sensor array and includes a plurality of apertures which are arranged such that one aperture of the plurality of apertures overlies a corresponding active area of a corresponding sensor cell to expose a portion of the active area of the corresponding sensor cell and wherein light of the predetermined wavelength is capable of being sensed by the portion of the active area that is exposed by the corresponding aperture.

20. The system of claim 16 wherein first processing unit further compares data which is representative of the intensity of light sampled by a plurality of sensor cells at the first set of discrete locations to associated data of a mask pattern design database.

21. The system of claim 20 wherein the mask pattern design database includes polygon data or intensity data which is representative of features on the photomask.

22. The system of claim 21 further including a second processing unit to convert the polygon data of a first design database to the mask pattern design database comprised of intensity data, wherein the intensity data for discrete locations correspond to the polygon data for associated discrete locations.

23. The system of claim 22 wherein the photomask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of a design-target.

24. The system of claim 22 wherein the photomask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of an after-OPC or after-PSM decoration pattern.

25. The system of claim 22 wherein the photomask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of a design-target and data which is representative of the after-OPC or after-PSM decoration pattern.

26. A photomask inspection system to detect defects in a photomask wherein an aerial image of the photomask is produced on a wafer plane by an optical system having a platform, the system comprising:

an image sensor unit capable of being disposed on or the platform, the image sensor unit includes;

a sensor array, capable of being located in the wafer plane, including a plurality of sensor cells wherein each sensor cell includes an active area to sample the intensity of light of a predetermined wavelength that is incident thereon and wherein at discrete locations relative to the image of the photomask produced on the wafer plane, the sensor cells sample the intensity of light; and

a film, disposed over selected portions of the active areas of the plurality of sensor cells, to increase the spatial resolution of each sensor cell wherein the film is comprised of a material that impedes passage of light of the predetermined wavelength; and

a first processing unit, coupled to the image sensor unit, to generate image data which is representative of a portion of the aerial image of the photomask wherein the portion of the aerial image includes a plurality of non-contiguous sub-images and wherein the processing unit generates each sub-image of the plurality of non-contiguous sub-images using the intensity of light sampled by at least one sensor cell at a plurality of discrete locations relative to the aerial image, and wherein the non-contiguous sub-images include images of features of the photomask.

27. The system of claim 26 further including a second processing unit, to compare the image data generated by the first processing unit to data of a mask pattern design database, wherein the mask pattern design database includes data which is representative of features on the photomask.

28. The system of claim 27 wherein the mask pattern design database is a design-target of the wafer image of the photomask.

29. The system of claim 27 wherein the mask pattern design database includes polygon data which is representative of features on the photomask.

30. The system of claim 27 wherein the mask pattern design database includes intensity data which is representative of features on the photomask.

31. The system of claim 27 wherein the first or second processing unit converts the data which is representative of the intensity of light sampled by each sensor cell at each discrete location to corresponding polygon data.

32. The system of claim 31 wherein the mask pattern design database is comprised of polygon data representing an intended wafer image.

33. The system of claim 27 further including a database conversion processing unit to convert the polygon data of a first design database to the mask pattern design database comprised of intensity data wherein the intensity data for each spatial location corresponds to the polygon data for each associated spatial location.

34. The system of claim 27 wherein the first processing unit generates at least a portion of the aerial image of the photomask by interleaving the intensity data sampled by a plurality of the sensor cells.

35. The system of claim 34 wherein the first processing unit generates the aerial image of the photomask using de-convolution.

36. The system of claim 34 wherein the second processing unit compares the aerial image of the photomask with an aerial image of the photomask which is generated using the mask pattern design database.

37. The system of claim 34 wherein the second processing unit compares the aerial image of the photomask with the design-target of the intended image of the photomask.

38. The system of claim 26 wherein the image sensor unit further includes a substrate having a wafer or wafer-like shaped profile, wherein the sensor array is disposed on or in the substrate and wherein the substrate is capable of being disposed on the platform.

39. The system of claim 26 wherein the film is disposed between the active areas of the sensor cells and a protective outer layer of the sensor array and includes a plurality of apertures which are arranged such that one aperture of the plurality of apertures overlies a corresponding active area of a corresponding sensor cell to expose a portion of the active area of the corresponding sensor cell and wherein light of the predetermined wavelength is capable of being sensed by the portion of the active area that is exposed by the corresponding aperture.

40. The system of claim 26 wherein the film is disposed on a protective outer layer of the sensor array and includes a plurality of apertures which are arranged such that one aperture of the plurality of apertures overlies a corresponding active area of a corresponding sensor cell to expose a portion of the active area of the corresponding sensor cell and wherein light of the predetermined wavelength is capable of being sensed by the portion of the active area that is exposed by the corresponding aperture.

41. The system of claim 27 wherein the first and second processing units are the same processing unit.