Abstract:
A method for repairing a defective photomask having contained therein a minimum of one defect within a defective pattern employs a non-defective photomask for purposes of photoexposing a photoresist layer formed upon the defective photomask such as to form a patterned photoresist layer which leaves exposed the minimum of one defect. The minimum of one defect may then be repaired with the patterned photoresist layer in place as a repair mask. The method also provides for use of a non-defective pattern region within a defective photomask in a like fashion for repairing a defective pattern region within the same photomask. The method may be extended to repairing defective microelectronic products.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to methods for repairing patterned layers formed over substrates employed for fabricating microelectronic products. More particularly, the present invention relates to methods for efficiently repairing photomasks employed for fabricating microelectronic products. 
     2. Description of the Related Art 
     Common in the microelectronic product fabrication art is the use of photomasks for purposes of defining patterned photoresist layers which in turn are employed for defining patterned microelectronic layers and patterned microelectronic structures when fabricating microelectronic products. 
     While photomasks are clearly desirable and often essential in the microelectronic product fabrication art, photomasks are nonetheless not entirely without problems in the microelectronic product fabrication art. In that regard, photomasks often suffer from defects which are difficult to efficiently repair since photomask repair methods often employ direct repair methods and apparatus which require lengthy processing time and often result in incidental damage when repairing photomasks. 
     It is thus desirable to provide methods for efficiently repairing photomasks employed for fabricating microelectronic products. It is towards the foregoing object that the present invention is directed. 
     Various methods for repairing photomasks have been disclosed in the microelectronic product fabrication art. 
     Included but not limiting among the methods are methods disclosed within: (1) Adair et al., in U.S. Pat. No. 5,506,080 (a photomask repair method which involves repair of defects within a photoresist layer employed for fabricating a photomask); (2) Shimanaka, in U.S. Pat. No. 5,757,480 (a laser alignment method for photomask repair); (3) George et al., in U.S. Pat. No. 5,981,110 (a photoresist masking layer method for photomask repair); and (4) Grenon et al., in U.S. Pat. No. 6,165,649 (a sacrificial masking layer method for photomask repair). 
     The teachings of each of the foregoing references are incorporated herein fully by reference. 
     Desirable are additional methods for efficiently repairing photomasks employed for fabricating microelectronic products. 
     It is towards the foregoing object that the present invention is directed. 
     SUMMARY OF THE INVENTION 
     A first object of the invention is to provide a method for repairing a photomask. 
     A second object of the invention is to provide a method in accord with the first object of the invention, wherein the photomask is efficiently repaired. 
     In accord with the objects of the invention, the invention provides a method for repairing a photomask. 
     To practice the method of the invention, there is first provided a defective photomask having contained therein a defective pattern having a minimum of one defect. There is also provided a non-defective photomask having contained therein a non-defective pattern identical to the defective pattern, but absent the minimum of one defect. There is also formed a photoresist layer upon the defective photomask including the defective pattern to form a photoresist coated defective photomask. There is then aligned, via optical projection, the non-defective pattern within the non-defective photomask with the defective pattern within the photoresist coated defective photomask. There is then photoexposed and developed the photoresist layer upon the photoresist coated defective photomask while employing the non-defective pattern within the non-defective photomask as a mask to form a patterned photoresist layer coated defective photomask which leaves exposed the minimum of one defect within the defective pattern. Finally, there is then repaired the minimum of one defect within the defective pattern while employing the patterned photoresist layer as a repair mask. 
     The method may also be extended to repairing a defective patterned layer within a microelectronic product. 
     The present invention provides a method for repairing a photomask, wherein the photomask is efficiently repaired. 
     The present invention realizes the foregoing object by employing an identical non-defective pattern within a non-defective photomask as a photomask for forming upon a defective pattern within a defective photomask a patterned photoresist layer which serves as a mask layer for repairing a defect within the defective pattern within the defective photomask. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, features and advantages of the invention are understood within the context of the Description of the Preferred Embodiment, as set forth below. The Description of the Preferred Embodiment is understood within the context of the accompanying drawings, which form a material part of this disclosure, wherein: 
         FIG. 1  and  FIG. 2  show a schematic cross-sectional diagram and a schematic plan-view diagram of a non-defective photomask which may be employed within the invention. 
         FIG. 3 ,  FIG. 4 ,  FIG. 5  and  FIG. 6  show a series of schematic cross-sectional diagrams and schematic plan-view diagrams illustrating a pair of defective photomasks which may be repaired in accord with the invention. 
         FIG. 7 ,  FIG. 8 ,  FIG. 9  and  FIG. 10  show a series of schematic cross-sectional diagrams illustrating the results of progressive stages in repairing a first defective photomask in accord with the present invention. 
         FIG. 11 ,  FIG. 12 ,  FIG. 13  and  FIG. 14  show a series of schematic cross-sectional diagrams illustrating the results of progressive stages in repairing a second defective photomask in accord with the present invention. 
         FIG. 15  and  FIG. 16  show a pair of schematic diagrams illustrating operation of a photolithographic apparatus for repairing a photomask in accord with the present invention. 
         FIG. 17 ,  FIG. 18 ,  FIG. 19  and  FIG. 20  show a series of schematic cross-sectional diagrams illustrating a pair of defective microelectronic products which may be repaired in accord with the invention, as well as a pair of repaired defective microelectronic products repaired in accord with the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides a method for repairing a photomask, wherein the photomask is efficiently repaired. 
     The present invention realizes the foregoing object by employing an identical non-defective pattern within a non-defective photomask as a photomask for forming upon a defective pattern within a defective photomask a patterned photoresist layer which serves as a mask layer for repairing a defect within the defective pattern within the defective photomask. 
       FIG. 1  to  FIG. 6  show a series of schematic cross-sectional diagrams and schematic plan-view diagrams illustrating: (1) a non-defective photomask which may be employed within the context of the present invention; and (2) a pair of defective photomasks which may be repaired in accord with the present invention. The photomasks may be employed for fabricating microelectronic products, and in particular semiconductor products. 
       FIG. 1  and  FIG. 2  show a schematic plan-view diagram and a schematic cross-sectional diagram of the non-defective photomask. 
     Within both  FIG. 1  and  FIG. 2 , the non-defective photomask  11  comprises a transparent substrate  10  having formed thereupon a series of opaque pattern layers  12   a ,  12   b ,  12   c  and  12   d.    
     Within the invention, the transparent substrate  10  is typically a quartz substrate formed to a thickness of from about 1 millimeter to about 10 millimeters. In addition, the opaque pattern layers  12   a ,  12   b ,  12   c  and  12   d  are typically opaque metal pattern layers, such as chromium opaque metal pattern layers. Other opaque metals, such as but not limited to aluminum, molybdenum, titanium and tungsten, may also be employed for forming the opaque pattern layers  12   a ,  12   b ,  12   c  and  12   d . Within the invention, each of the series of opaque pattern layers  12   a ,  12   b ,  12   c  and  12   d  is typically formed to a thickness of from about 200 to about 1000 angstroms and a linewidth and spacing of from about 0.1 to about 1.0 microns. 
       FIG. 3  and  FIG. 4  show a schematic plan-view diagram and a schematic cross-sectional diagram of a first defective photomask which may be repaired in accord with the present invention. 
     Within both  FIG. 3  and  FIG. 4 , the first defective photomask  11 ′ comprises a transparent substrate  10 ′ and a series of opaque pattern layers  12   a ′,  12   b ′,  12   c ′ and  12   d ′ as are otherwise identical in dimension and location with the transparent substrate  10  and the series of opaque pattern layers  12   a ,  12   b ,  12   c  and  12   d  within the non-defective photomask  11  as illustrated within  FIG. 1  and  FIG. 2 . However, the first defective photomask  11 ′ also comprises an opaque patterned layer excess defect  13  which is otherwise undesirable and bridges between the pair of opaque pattern layers  12   b ′ and  12   c′.    
       FIG. 5  and  FIG. 6  show a schematic plan-view diagram and a schematic cross-sectional diagram of a second defective photomask which may be repaired in accord with the present invention. 
     Within both  FIG. 5  and  FIG. 6 , the second defective photomask  11 ″ comprises a transparent substrate  10 ″ and a series of opaque pattern layers  12   a ″,  12   b ″,  12   c ″ and  12   d ″ as are otherwise identical in dimension and location with the transparent substrate  10  and the series of opaque pattern layers  12   a ,  12   b ,  12   c  and  12   d  within the non-defective photomask  11  as illustrated within  FIG. 1  and  FIG. 2 . However, the second defective photomask  11 ″ also comprises an opaque patterned layer deficiency defect  15  within the opaque pattern layer  12   b ″. The opaque patterned layer deficiency defect  15  results in the opaque pattern layer  12   b ″ having a portion thereof narrower in linewidth than desired. 
     The present invention is directed towards repairing defective photomasks, such as the defective photomasks  11 ′ and  11 ″ whose schematic plan-view diagrams and schematic cross-sectional diagrams are illustrated in  FIG. 3 ,  FIG. 4 ,  FIG. 5  and  FIG. 6 , defects such as both the opaque pattern layer excess defect  13  as illustrated in  FIG. 3  and the opaque pattern layer deficiency defect  15  as illustrated in  FIG. 5 . 
       FIG. 7  to  FIG. 10  show a series of schematic cross-sectional diagrams illustrating the results of progressive stages in repairing the first defective photomask  11 ′ as illustrated in  FIG. 3  and  FIG. 4 , in accord with the present invention. 
       FIG. 7  shows the first defective photomask of  FIG. 4 , in turn having formed thereupon a photoresist layer  14 ′. Within the invention, the photoresist layer  14 ′ is formed of a positive photoresist material, as may be otherwise generally conventional in the microelectronic product fabrication art. Typically, the photoresist layer  14 ′ is formed to a thickness of from about 8000 to about 20000 angstroms. 
     Also shown in  FIG. 7  is the non-defective photomask  11  which is aligned with the defective photomask such that the non-defective pattern within the non-defective photomask is aligned with the defective pattern within the defective photomask. Such alignment may be undertaken within an otherwise conventional photomask alignment tool, or within a special apparatus which is specifically designed to achieve such alignment in accord with the present invention. Such a special apparatus is disclosed in greater detail below. 
       FIG. 8  shows the results of further processing of the defective photomask of  FIG. 7 . 
       FIG. 8  illustrates the results of photoexposing and developing the photoresist layer  14 ′ of  FIG. 7  to form a series of patterned photoresist layers  14   a ′,  14   b ′,  14   c ′ and  14   d ′ which are aligned upon the series of opaque pattern layers  12   a ′,  12   b ′,  12   c ′ and  12   d ′, and which leave exposed portions of the transparent substrate  10 ′ and the opaque pattern layer excess defect  13 . Photoexposure of the blanket photoresist layer  14 ′ may be undertaken employing a photoexposure apparatus as is otherwise generally conventional in the microelectronic fabrication art, while employing photoexposure conditions as are appropriate for the positive photoresist material from which is formed the photoresist layer  14 ′. Development of the photoexposed photoresist layer  14 ′ may be undertaken employing developing methods as are otherwise generally conventional in the microelectronic fabrication art. 
       FIG. 9  shows the results of further processing of the defective photomask of  FIG. 8 . 
       FIG. 9  illustrates the results of etching the opaque pattern layer excess defect  13  interposed between the pair of opaque pattern layers  12   b ′ and  12   c ′, while employing the series of patterned photoresist layers  14   a ′,  14   b ′,  14   c ′ and  14   d ′ as an etch mask layer. 
     Within the invention, the opaque pattern layer excess defect  13  may be etched from between the opaque pattern layers  12   b ′ and  12   c ′ while employing etching methods including but not limited to wet chemical etching methods, dry plasma etching methods, sputter etching methods and aggregate methods thereof. 
       FIG. 10  shows the results of further processing of the defective photomask of  FIG. 9 . 
       FIG. 10  shows the results of stripping the series of patterned photoresist layers  14   a ′,  14   b ′,  14   c ′ and  14   d ′ from the corresponding series of opaque pattern layers  12   a ′,  12   b ′,  12   c ′ and  12   d ′, to thus form from the defective photomask  11 ′ as illustrated in  FIG. 4  a repaired defective photomask  11   a′.    
     The series of patterned photoresist layers  14   a ′,  14   b ′,  14   c ′ and  14   d ′ may be stripped employing stripping methods and materials as are otherwise generally conventional in the microelectronic fabrication art. 
       FIG. 10  illustrates a repaired defective photomask  11   a ′ identical with the non-defective photomask  11  as illustrated in  FIG. 2 . The repaired defective photomask  11   a ′ is efficiently repaired while employing a photolithographic method which employs an identical non-defective pattern within the non-defective photomask as a photomask for forming upon a defective pattern within a defective photomask a patterned photoresist layer which serves as an etch mask layer for etching and repairing a defect within the defective pattern within the defective photomask. 
     Insofar as the invention employs an alignment and projection photolithographic method (rather than an ion beam method which charges a substrate) for forming a patterned photoresist layer as a defect repair mask layer, the present invention also provides for greater accuracy in image alignment when repairing the defect within the defective pattern within the defective photomask. 
       FIG. 11  to  FIG. 14  show a series of schematic cross-sectional diagrams illustrating the results of progressive stages in repairing the second defective photomask  11 ″ of  FIG. 5  and  FIG. 6 , in accord with the present invention. 
       FIG. 11  shows the second defective photomask  11 ″ of  FIG. 6 , in turn having formed thereupon a photoresist layer  14 ″. Within the invention, the photoresist layer  14 ″ is formed of a negative photoresist material, as may be otherwise generally conventional in the microelectronic product fabrication art. Typically, the photoresist layer  14 ″ is formed to a thickness of from about 8000 to about 20000 angstroms. 
     Also shown in  FIG. 11  is the non-defective photomask  11  which is aligned with the defective photomask such that the non-defective pattern within the non-defective photomask  11  is aligned with the defective pattern within the defective photomask  11 ″. Such alignment may be undertaken within an otherwise conventional photomask alignment tool, or within a special apparatus which is specifically designed to achieve such alignment in accord with the present invention. Such a special apparatus is disclosed in greater detail below. 
       FIG. 12  shows the results of further processing of the defective photomask  11 ″ of  FIG. 11 . 
       FIG. 12  illustrates the results of photoexposing and developing the photoresist layer  14 ″ of  FIG. 11  to form a series of patterned photoresist layers  14   a ″,  14   b ″,  14   c ″,  14   d ″ and  14   e ″, which are interposed between the series of opaque pattern layers  12   a ″,  12   b ″,  12   c ″ and  12   d ″.  FIG. 12  also illustrates a gap formed between the opaque pattern layer  12   b ″ and the patterned photoresist layer  14   c ″ at the location of the opaque patterned layer deficiency defect  15  as illustrated in  FIG. 5 . Photoexposure of the photoresist layer  14 ″ may be undertaken employing a photoexposure apparatus as is otherwise generally conventional in the microelectronic fabrication art, while employing photoexposure conditions as are appropriate for the negative photoresist material from which is formed the photoresist layer  14 ″. Development of the photoexposed photoresist layer  14 ″ may be undertaken employing developing methods as are otherwise generally conventional in the microelectronic fabrication art. 
       FIG. 13  shows the results of further processing of the defective photomask of  FIG. 12 . 
       FIG. 13  illustrates the results of depositing a patch layer  17  into the gap interposed between the opaque pattern layer  12   b ″ and the patterned photoresist layer  14   c ″, such as to fill the opaque patterned layer deficiency defect  15  as illustrated in  FIG. 5 . The patch layer  17  is typically also formed of an opaque material, and generally formed by employing a localized photoassisted deposition of a patch material. Under such circumstances, the series of patterned photoresist layers  14   a ″,  14   b ″,  14   c ″,  14   d ″ and  14   e ″ provide a barrier precluding deposition of excess patch material upon the transparent substrate. 
       FIG. 14  shows the results of further processing of the defective photomask of  FIG. 13 . 
       FIG. 14  shows the results of stripping the series of patterned photoresist layers  14   a ″,  14   b ″,  14   c ″,  14   d ″ and  14   e ″ from the defective photomask as illustrated in  FIG. 13 , to thus form a repaired defective photomask  11   a″.    
     The series of patterned photoresist layers  14   a ″,  14   b ″,  14   c ″,  14   d ″ and  14   e ″ may be stripped employing stripping methods and materials as are otherwise generally conventional in the microelectronic fabrication art. 
       FIG. 14  illustrates a repaired defective photomask  11   a ″ functionally equivalent with the non-defective photomask  11  as illustrated in  FIG. 2 . The repaired defective photomask is efficiently repaired while employing a photolithographic method which employs an identical non-defective pattern within the non-defective photomask as a photomask for forming upon a defective pattern within a defective photomask a patterned photoresist layer which serves as a mask layer for repairing the defect within the defective pattern within the defective photomask. 
       FIG. 15  and  FIG. 16  show a pair of schematic diagrams illustrating an apparatus which may be employed for repairing a defective photomask in accord with the invention. 
     The apparatus comprises an alignment and photoexposure light source  30 , a light beam from which travels through a series of mirrors  32   a ,  32   b ,  32   c  and  32   d  and a pair of lenses  36   a  and  36   b  to reach an image detector  38 . 
     Within the apparatus, a defective photomask  34  having both a non-defective pattern region  35   a  and a corresponding otherwise dimensionally identical defective pattern region  35   b  having formed therein a minimum of one defect, is positioned within the apparatus such that the non-defective pattern within the non-defective pattern region  35   a  may be optically projected and aligned upon the defective pattern within the defective pattern region  35   b.    
       FIG. 15  illustrates the general alignment characteristics of the apparatus. Such preliminary optical projection alignment is also intended as applicable when employing a non-defective photomask separate from a defective photomask, in accord with the above disclosure.  FIG. 16  further illustrates a photoresist layer  40  formed upon the defective pattern within the defective pattern region  35   b , but not upon the non-defective pattern within the non-defective pattern region  35   a . When a photoexposure radiation dose (rather than an optical projection alignment radiation dose) is issued from the light source  30 , a portion of the photoresist layer  40  covering the defective pattern region  35   b  may be photoexposed in accord with the invention. 
     Thus, as illustrated within  FIG. 15  and  FIG. 16 , a defect within a defective pattern region within a defective photomask may be repaired while employing as a photomask a non-defective pattern region within the same defective photomask. 
     While the foregoing disclosure describes the invention within the context of repairing a defective photomask having either an opaque pattern layer excess defect or an opaque pattern layer deficiency defect, the present invention is not intended to be specifically so limited. Rather, the present invention may also be employed for repairing within defective microelectronic products defective patterned layers formed of materials including but not limited to conductor materials, semiconductor materials and dielectric materials formed upon substrates formed of materials including but not limited to conductor materials, semiconductor materials, dielectric materials and laminates thereof. In accord with the foregoing materials limitations, examples of defective microelectronic products which may be repaired in accord with the invention, as well as corresponding repaired defective microelectronic products after such repair, are illustrated in  FIG. 17  to  FIG. 20 . 
       FIG. 17  illustrates a defective microelectronic product  51 ′ comprising a substrate  50 ′ having formed thereupon a series of patterned layers  52   a ′,  52   b ′,  52   c ′ and  52   d ′ of which the patterned layers  52   b ′ and  52   c ′ are bridged by a patterned layer excess defect  53 . The defective microelectronic product  51 ′ of  FIG. 17  corresponds generally with the defective photomask  11 ′ of  FIG. 3  and  FIG. 4 . 
       FIG. 18  illustrates a repaired defective microelectronic product  51   a ′ corresponding with the defective microelectronic product  51 ′ of  FIG. 17 , but where the patterned layer excess defect  53  has been removed. The patterned layer excess defect  53  may be removed employing a processing sequence analogous, equivalent or identical to the processing sequence as illustrated in  FIG. 7  to  FIG. 10  for repairing the defective photomask  11 ′ as illustrated in  FIG. 3  and  FIG. 4 , but where the defective photomask  11 ′ is replaced with the defective microelectronic product  51 ′. 
       FIG. 19  illustrates a defective microelectronic product  51 ″ comprising a substrate  50 ″ having formed thereupon a series of patterned layers  52   a ″,  52   b ″,  52   c ″ and  52   d ″, where the patterned layer  52   b ″ is undersized such as to represent a patterned layer deficiency defect. The defective microelectronic product  51 ″ of  FIG. 19  corresponds generally with the defective photomask  11 ″ of  FIG. 5  and  FIG. 6 . 
       FIG. 20  illustrates a repaired defective microelectronic product  51   a ″ corresponding with the defective microelectronic product  51 ″ of  FIG. 19 , but where the undersized patterned layer  52   b ″ has been supplemented with a patch layer  57 . The patch layer  57  may be formed employing a processing sequence analogous, equivalent or identical to the processing sequence as illustrated in  FIG. 11  to  FIG. 14  for repairing the defective photomask  11 ″ as illustrated in  FIG. 5  and  FIG. 6 , but where the defective photomask  11 ″ is replaced with the defective microelectronic product  51 ″. 
     Within the additional embodiments of the invention as illustrated in  FIG. 17  to  FIG. 20 , and when the substrate  50 ′ or  50 ″ is not formed of a transparent material, the apparatus as illustrated in  FIG. 15  and  FIG. 16  may not be employed and an independent non-defective photomask is required for optical alignment and optical projection purposes. 
     The preferred embodiments of the invention are illustrative of the invention rather than limiting of the invention. Revisions and modifications may be made to materials, structures and dimensions in accord with the preferred embodiments of the invention while still providing a method for repairing a defective photomask or a defective microelectronic product in accord with the present invention, further in accord with the accompanying claims.