System and method for lithography process monitoring and control

• US 20040232313A1
• Filed: 06/21/2004
• Published: 11/25/2004
• Est. Priority Date: 06/07/2002
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: Jun Ye, R. Fabian W. Pease, Xun Chen
• Inventors: Ye, Jun, Chen, Xun, Pease, R. Fabian W.
• Granted Patent: US 6,969,864 B2
• Time in Patent Office: Days
• 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 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 product-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. In this way, the aerial image used, generated or produced to measure, inspect, characterize and/or evaluate the photomask is the same aerial image used, generated or produced during wafer exposure in integrated circuit manufacturing.

In another embodiment, the system, sensor and technique characterizes and/or evaluates the performance of the optical lithographic equipment, for example, the optical sub-system of such equipment. In this regard, in one embodiment, an image sensor unit measures, collects, senses and/or detects the aerial image produced or generated by the interaction between lithographic equipment and a photomask having a known, predetermined or fixed pattern (i.e., test mask). In this way, the system, sensor and technique collects, senses and/or detects the aerial image produced or generated by the test mask-lithographic equipment in order to inspect, evaluate and/or characterize the performance of the lithographic equipment.

Claims

1-40. -40. (Canceled).

41. 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 within 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.

42. The system of claim 41 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.

43. The system of claim 41 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.

44. The system of claim 41 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.

45. The system of claim 41 wherein the mask pattern design database is comprised of intensity data.

46. The system of claim 41 wherein the mask pattern design database includes polygon data.

47. The system of claim 46 wherein the first processing unit converts the polygon data to associated intensity data.

48. The system of claim 41 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.

49. The system of claim 41 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.

50. The system of claim 41 wherein the first processing unit generates an aerial image of the photomask by interleaving the intensity data sampled by a plurality of sensor cells at each discrete location.

51. The system of claim 50 wherein the first processing unit compares the aerial image of the photomask with a simulated aerial image of the photomask that is generated using the mask pattern design database.

52. The system of claim 41 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.

53. The system of claim 41 wherein the photomask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of a design-target.

54. The system of claim 41 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.

55. The system of claim 41 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.

56. 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 within 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 each sensor cell at discrete locations of a first die to data which is representative of the intensity of light sampled by each sensor cell at corresponding discrete locations of a second die.

57. The system of claim 56 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.

58. The system of claim 56 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.

59. The system of claim 56 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.

60. The system of claim 56 wherein first processing unit further compares data which is representative of the intensity of light sampled by a plurality of sensor cells at discrete locations of a first die to associated data of a mask pattern design database.

61. The system of claim 60 wherein the mask pattern design database includes polygon data or intensity data which is representative of features on the photomask.

62. The system of claim 61 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.

63. The system of claim 62 wherein the photomask includes OPC or PSM features and wherein the mask pattern design database includes data which is representative of a design-target.

64. The system of claim 62 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.

65. The system of claim 62 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.

66. 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 within 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.

67. The system of claim 66 further including a second processing unit, coupled to the first 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.

68. The system of claim 67 wherein the mask pattern design database is a design-target of the wafer image of the photomask.

69. The system of claim 67 wherein the mask pattern design database includes polygon data which is representative of features on the photomask.

70. The system of claim 67 wherein the mask pattern design database includes intensity data which is representative of features on the photomask.

71. The system of claim 67 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.

72. The system of claim 71 wherein the mask pattern design database is comprised of polygon data representing an intended wafer image.

73. The system of claim 67 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.

74. The system of claim 67 wherein the first processing unit generates the aerial image of the photomask by interleaving the intensity data sampled by the sensor cells at discrete locations relative to the image of the photomask produced on the wafer plane.

75. The system of claim 74 wherein the first processing unit generates the aerial image of the photomask using de-convolution.

76. The system of claim 74 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.

77. The system of claim 74 wherein the second processing unit compares the aerial image of the photomask with the design-target of the intended image of the photomask.

78. The system of claim 66 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.

79. The system of claim 66 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.

80. The system of claim 66 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.