System and method for lithography process monitoring and control

• US 6,884,984 B2
• Filed: 01/12/2004
• Issued: 04/26/2005
• 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 T.
• Application Number:
  US10/755,809
• Publication Number:
  US 20040140418A1
• Time in Patent Office: 470 Days
• Field of Search: 250/208.1, 250/548, 250/559.4, 356/399, 356/400, 356/401, 355/53, 355/55
• US Class Current: 250/208.1
• 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

In one aspect, the present invention is a technique of, and a system and sensor for measuring, inspecting, characterizing and/or evaluating optical lithographic equipment, methods, and/or materials used therewith, for example, photomasks. In one embodiment, the system, sensor and technique 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 during the integrated circuit fabrication process) 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 measure the critical dimensions of features of the photomask, using data which is representative of the intensity of light sampled by the image sensor unit, to control at least one operating parameter of the lithographic equipment.

Claims

1. A system to control the manufacture of integrated circuits using (1) a production-type mask, which includes features having a line width that includes a critical dimension, and (2) a lithographic integrated circuit manufacturing system having (i) an optical system to produce an image of the production-type mask on a wafer plane, and (ii) platform moveable between a plurality of discrete locations relative to the image, the system comprising:

an image sensor unit capable of being disposed on the moveable platform, the image sensor unit includes a sensor array capable of being located in the wafer plane, wherein the sensor array includes a plurality of sensor cells to sample light of a predetermined wavelength that is incident thereon, and wherein at each discrete location of the plurality of discrete locations of the platform the sensor cells sample the intensity of light; and

a processing unit, coupled to the image sensor unit, to measure the critical dimension of the features using tile data which is representative of the intensity of light sampled by a plurality of sensor cells at a plurality of discrete locations of the platform and, in response to the measured critical dimension, to control at least one operating parameter of the lithographic integrated circuit manufacturing system.

2. The system of claim 1 wherein the operating parameter is a parameter of the optical system.

3. The system of claim 2 wherein the processing unit, in response to determining the measured critical dimension of a first feature on the production-type mask that is smaller than a target critical dimension, instructs the optical system to increase the illumination when the platform is located in an area corresponding to the particular feature.

4. The system of claim 3 wherein the target critical dimension is based on an expected or a desired critical dimension of the first feature.

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

a substrate wherein the sensor array is disposed on or in the substrate;

a film, disposed over selected portions of the effective active areas of the plurality of sensor cells to reduce the effective active area and enhance the spatial resolution of each sensor cells wherein the film is comprised of a material that impedes passage of light of the predetermined wavelength.

6. The system of claim 5 wherein the film defines at least one aperture disposed over a selected portion of each effective active area of the plurality of sensor cells and wherein the aperture includes a shape, wherein the shape is based on at least the critical dimension of a first feature on the production mask.

7. The system of claim 5 wherein the film defines at least one aperture disposed over a selected portion of each effective active area of the plurality of sensor cells and wherein the location of the at least one aperture is correlated to the location of a first feature on the production-type mask.

8. The system of claim 5 wherein the film defines at least one aperture disposed over a selected portion of each effective active area of the plurality of sensor cells wherein the aperture includes a shape which is based on the critical dimension of at least one feature on the production-type mask.

9. The system of claim 5 wherein the substrate includes a wafer-shaped profile.

10. The system of claim 1 wherein:

the processing unit generates;

a first data set using the intensity of light sampled by each sensor cell when the platform is positioned at a first location relative to the aerial image, wherein the first data set includes data which is representative of the aerial image at locations corresponding to the locations of the sensor cells relative to the aerial image; and

a second data set using the intensity of light sampled by each sensor cell when the platform is positioned at a second location relative to the aerial image, wherein the second data set includes data which is representative of the aerial image at locations corresponding to the locations of the sensor cells relative to the aerial image; and

wherein the first location and the second location are adjacent locations along an axle in a first direction of the platform and wherein the distance between the first location and the second location is less than the distance between the two opposing edges of the effective active area of each sensor cell of the sensor array, wherein the opposing sides are transverse to the axis.

11. The system of claim 1 wherein:

the processing unit generates;

a first data set using the intensity of light sampled by each sensor cell when the platform is positioned at a first location relative to the aerial image, wherein the first data set includes data which is representative of the aerial image at locations corresponding to the locations of the sensor cells relative to the aerial image; and

a second data set using the intensity of light sampled by each sensor cell when the platform is positioned at a second location relative to the aerial image, wherein the second data set includes data which is representative of the aerial image at locations corresponding to the locations of the sensor cells relative to the aerial image; and

wherein the first location and the second location are adjacent locations along an axis in a first direction of the platform and wherein the distance between the first location and the second location is less than the diameter of the effective active area of each sensor cell.

12. The system of claim 1 wherein the processing unit generates an aerial image of the mask by interleaving the intensity data sampled by each sensor cell at each discrete location of the platform.

13. The system at claim 12 wherein the processing unit determines the critical dimension based on at least a portion of the interleaved intensity data.

14. A system for controlling the manufacture of integrated circuits using (1) a production-type mask which includes a plurality of features including a first feature having a line width that includes a target critical dimension, and (2) a lithographic integrated circuit manufacturing system having (i) an optical system to produce en image of the production-type mask on a wafer plane, and (ii) a platform moveable between a plurality of discrete locations relative to the image of the production-type mask on the wafer plane, the system comprising:

an image sensor unit disposed in the moveable platform, the image sensor unit includes a sensor array capable of being located in the wafer plane, wherein the sensor array includes a plurality of sensor cells wherein each sensor cell includes an effective active area to sample light of a predetermined wavelength that is incident thereon, and wherein at each discrete location of the plurality of discrete locations of the platform the sensor cells sample the intensity of light; and

a processing unit, coupled to the image sensor unit, to measure the critical dimension of the first feature using data which is representative of the intensity of light sampled by at least one sensor cell at at least one location of the plurality of discrete locations and, in response to determining the measured critical dimension of the first feature is smaller than a the target critical dimension, to adjust at least one operating parameter of the optical system of the lithographic integrated circuit manufacturing system.

15. The system of claim 14 wherein the operating parameter is an illumination of the optical system.

16. The system of claim 15 wherein the processing unit adjusts the illumination of the optical system by instructing the optical system to increase the illumination when the platform is located in an area corresponding to the first feature.

17. The system of claim 14 wherein the target critical dimension is based on an expected or a desired critical dimension of the first feature.

18. The system of claim 14 wherein the image sensor unit further includes:

a substrate wherein the sensor array is disposed on or in the substrate;

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

19. The system of claim 18 wherein the film defines at least one aperture disposed over a selected portion of each effective active area of the plurality of sensor cells and wherein the location of the at least one aperture is correlated with the location of the first feature on the production-type mask.

20. The system of claim 18 wherein the film defines at least one aperture disposed over a selected portion of each effective active area of the plurality of sensor cells wherein at least one aperture includes a shape which is based on the critical dimension of the first feature on the production-type mask.

21. The system of claim 14 wherein the distance between opposing edges of the effective active area of the at least one sensor cell is greater than or equal to the distance between two adjacent discrete locations of the platform along an axis in a first direction.

22. The system of claim 14 wherein the diameter of the effective active area of the at least one sensor cell is greater than or equal to the distance between two adjacent discrete locations of the platform along an axis in a first direction.

23. The system of claim 14 wherein the processing unit generates an aerial image of the mask by interleaving the intensity data sampled by each sensor cell at each discrete location of the platform.

24. The system of claim 23 wherein the processing unit determines the critical dimension of the first feature using the interleaved intensity data of at least one sensor cell.

25. A system to evaluate the integrity of production-type masks and to control the manufacture of integrated circuits using (1) a production-type mask, which includes a plurality of features including a first feature having a line width, and (2) a lithographic integrated circuit manufacturing system having (i) an optical system to produce an image of the production-type mask on a wafer plane, and (ii) a platform moveable between a plurality of discrete locations relative to the image of the production-type mask, the system comprising:

a sensor array disposed on or in the moveable platform, the sensor array capable of being located in the wafer plane, wherein the sensor array includes a plurality of sensor cells wherein each sensor cell includes an effective active area to sample light of a predetermined wavelength that is incident thereon, and wherein at a plurality of discrete locations the sensor cells sample the intensity of light; and

a processing unit, coupled to the sensor array, to;

generate image data which is representative of the aerial image, wherein the processing unit generates the aerial image of the production-type mask by interleaving the image data sampled by each sensor cell at a plurality of discrete locations of the platform; and

measure the critical dimension of the first feature using the data which is representative of the intensity of light sampled by at least one sensor cell at at least one discrete location corresponding to the first feature.

26. The system of claim 25 wherein the line width of the first feature includes a target critical dimension and wherein the processing unit, in response to determining the measured critical dimension of the first feature is smaller than the target critical dimension, adjusts at least one operating parameter of the optical system of the lithographic integrated circuit manufacturing system.

27. The system of claim 26 wherein the processing unit adjusts the illumination of the optical system.

28. The system of claim 27 the processing unit adjusts the illumination of the optical system by instructing the lithographic integrated circuit manufacturing system to increase the illumination when the platform is located in an area corresponding to the first feature.

29. The system of claim 25 wherein the sensor array is disposed on or in a substrate having a wafer-shaped profile, and wherein the system further includes a film, disposed over selected portions of the effective active areas of the plurality of sensor cells to reduce the effective active area and enhance the spatial resolution of each sensor cell wherein the film is comprised of a material that impedes passage of light of the predetermined wavelength.

30. The system of claim 29 wherein the film defines at least one aperture disposed over a selected portion of each effective active area of the plurality of sensor cells and wherein the location of at least one of the apertures is correlated with the location of the first feature on the production-type mask.

31. The system of claim 29 wherein the film defines at least one aperture disposed over a selected portion of each effective active area of the plurality of sensor cells wherein at least one of the apertures includes a shape which is based on a target critical dimension of the first feature on the production-type mask.

32. The system of claim 25 wherein the distance between opposing edges of the effective active area of the at least one sensor cell is greater than or equal to the distance between two adjacent discrete locations of the platform along an axis in a first direction.

33. The system of claim 25 wherein the diameter of the effective active area of the at least one sensor cell is greater than or equal to the distance between two adjacent discrete locations of the platform along an axis in a first direction.

34. The system of claim 25 wherein the processing unit compares data which is representative of the intensity of light sampled by each sensor cell at each discrete location to data of a mask pattern design database, wherein the mask pattern design database includes data which is representative of the features on the production-type mask.

35. The system of claim 34 wherein the mask pattern design database is a design-target of the wafer image of the mask.

36. The system of claim 34 wherein the mask pattern design database includes polygon data which is representative of the production-type mask.

37. The system of claim 34 wherein the mask pattern design database includes intensity data which is representative of the production-type mask.

38. The system of claim 34 further including a film, disposed over the effective active areas of the plurality of sensor cells and comprised of a material that impedes passage of light of the predetermined wavelength, wherein the film includes a plurality of apertures which are arranged such that one aperture of the plurality of apertures overlies an associated active area of a corresponding sensor cell to expose a portion of the effective active area and wherein light of the predetermined wavelength is capable of being sensed by the portion of the effective active area that is exposed by the associated aperture.

39. The system of claim 34 wherein the 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.

40. The system of claim 39 wherein the mask pattern design database is comprised of polygon data representing an intended wafer image.

41. The system of claim 34 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.

42. The system of claim 34 wherein the processing unit generates the aerial image of the production-type mask by interleaving the intensity data sampled by each sensor cell at each discrete location of the platform.

43. The system of claim 42 wherein the processing unit generates the aerial image of the production-type mask using de-convolution.

44. The system of claim 42 wherein the processing unit compares the aerial image of the production-type mask with an aerial image of the mask which is generated using the mask pattern design database.

45. The system of claim 42 wherein the processing unit compares the aerial image of the production-type mask with a design-target of the wafer image of the mask.

46. The system of claim 25 wherein the processing unit compares data which is representative of the intensity of light sampled by each sensor cell at each discrete location of a first die to data which is representative of the intensity of light sampled by each sensor cell at each discrete location of a second die.

47. The system of claim 46 wherein processing unit further compares data which is representative of the intensity of light sampled by each sensor cell at each discrete location of a first die to associated data of a mask pattern design database.

48. The system of claim 47 wherein the mask pattern design database includes polygon data.

49. The system of claim 47 wherein the mask pattern design database is comprised of intensity data.

50. The system of claim 47 wherein the processing unit may further include a database processing unit to convert the polygon data of a first design database to the mask pattern design database comprised of intensity data, and wherein the intensity data for each spatial location corresponds to the polygon data for each associated spatial location.

51. The system of claim 50 wherein the mask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of the design-target.

52. The system of claim 50 wherein the mask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of the after-OPC or PSM-decoration pattern.

53. The system of claim 50 wherein the mask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of the design-target and data which is representative of the after-OPC or PSM-decoration pattern.