Granted Patent: Detection Of Phase Defects On Photomasks By Differential Imaging

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Patent History
  • Application
    US 09/336445
    1999-06-21
  • Granted
    US 6327033
    2001-12-04
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TitleDetection Of Phase Defects On Photomasks By Differential Imaging
Granted PatentUS 6327033
Granted Date2001-12-04
Priority Date1999-06-21 US 09/336445
InventorsFerguson, RA
Ferguson, R
Wong, AKK
CitationUS Patent 6327033. Washington, DC: US Patent and Trademark Office (USPTO), 2001 [How to Cite?]
AbstractA Method For Detecting Phase Features Or Phase Defects On Photomasks For Optical Lithography Is Described. The Asymmetric Imaging Behavior Through Focus Of Defects Or Features With A Phase Other Than 0 Deg Or 180 Deg Is Used To Distinguish Them From Other Features On The Mask. The Mask Is Inspected At Equally Spaced Positions About An Optimum Focus In Both Positive And Negative Directions. The Images Are Subtracted From One Another To Produce A Differential Image Of The Mask. While Opaque Features As Well As Transmitting Features At 0 Deg And 180 Deg Behave Identically At Positive And Negative Defocus, Thus Leading To A Zero-Valued Differential Image, The Focus Asymmetry Of Phase Defects And Features Produces A Non-Zero Differential Image From Which These Phase Defects And Features Can Be Located. By Comparing The Locations On The Mask For Which A Non-Zero Differential Image Is Obtained With The Designed Data For The Mask, The Phase Defects Can Be Sorted From The Phase Features And The Absence Of Phase Features Can Be Detected. Additional Image Processing Can Be Applied To Verify The Integrity Of The Phase Features. The Differential Image Inspection Technique Can Be Implemented On Existing Optical Inspection Tools By Employing A Two-Pass Inspection Performed At Positive And Negative Defocus In Sequence. In Addition, A New Apparatus With Parallel Inspection Optics Is Described For Inspecting The Mask At Positive And Negative Focus Simultaneously.
ReferencesUS 5270796 (A) 1993-12-14

US 5353116 (A) 1994-10-04

US 5786112 (A) 1998-07-28
DC Field
Value
dc.contributor.inventorFerguson, RA
dc.contributor.inventorFerguson, R
dc.contributor.inventorWong, AKK
dc.date.accessioned2007-10-30T06:52:13Z
patents.date.application1999-06-21
dc.date.available2007-10-30T06:52:13Z
patents.date.granted2001-12-04
patents.date.priority1999-06-21 US 09/336445
dc.description.abstractA Method For Detecting Phase Features Or Phase Defects On Photomasks For Optical Lithography Is Described. The Asymmetric Imaging Behavior Through Focus Of Defects Or Features With A Phase Other Than 0 Deg Or 180 Deg Is Used To Distinguish Them From Other Features On The Mask. The Mask Is Inspected At Equally Spaced Positions About An Optimum Focus In Both Positive And Negative Directions. The Images Are Subtracted From One Another To Produce A Differential Image Of The Mask. While Opaque Features As Well As Transmitting Features At 0 Deg And 180 Deg Behave Identically At Positive And Negative Defocus, Thus Leading To A Zero-Valued Differential Image, The Focus Asymmetry Of Phase Defects And Features Produces A Non-Zero Differential Image From Which These Phase Defects And Features Can Be Located. By Comparing The Locations On The Mask For Which A Non-Zero Differential Image Is Obtained With The Designed Data For The Mask, The Phase Defects Can Be Sorted From The Phase Features And The Absence Of Phase Features Can Be Detected. Additional Image Processing Can Be Applied To Verify The Integrity Of The Phase Features. The Differential Image Inspection Technique Can Be Implemented On Existing Optical Inspection Tools By Employing A Two-Pass Inspection Performed At Positive And Negative Defocus In Sequence. In Addition, A New Apparatus With Parallel Inspection Optics Is Described For Inspecting The Mask At Positive And Negative Focus Simultaneously.
patents.description.assigneeIbm [Us]
patents.description.ccUS
patents.description.countryUnited States of America
patents.description.kindB1
dc.description.naturepublished_or_final_version
dc.format.extent2095326 bytes
dc.format.extent5278 bytes
dc.format.mimetypeapplication/pdf
dc.format.mimetypetext/plain
patents.identifier.applicationUS 09/336445
dc.identifier.citationUS Patent 6327033. Washington, DC: US Patent and Trademark Office (USPTO), 2001 [How to Cite?]
patents.identifier.grantedUS 6327033
dc.identifier.urihttp://hdl.handle.net/10722/46533
dc.languageeng
patents.relation.familyUS 6327033 (B1) 2001-12-04
dc.relation.isreferencedbyUS 2010226562 (A1) 2010-09-09
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dc.relation.isreferencedbyWO 03058681 (A2) 2003-07-17
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dc.relation.isreferencedbyUS 6704695 (B1) 2004-03-09
dc.relation.referencesUS 5270796 (A) 1993-12-14
dc.relation.referencesUS 5353116 (A) 1994-10-04
dc.relation.referencesUS 5786112 (A) 1998-07-28
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License For Public Patent Documents
dc.titleDetection Of Phase Defects On Photomasks By Differential Imaging
dc.typePatent
patents.typePatent_granted