Optical inspection of a specimen using multi-channel responses from the specimen using bright and darkfield detection

An inspection system to inspect a first pattern on a specimen for defects to be compared against a second pattern that is intended to be the same, said second pattern has known reflected darkfield and brightfield images at each point of interest, said inspection system comprising:

• a darkfield and brightfield illumination system to illuminate said first pattern on said specimen;
• a reflected darkfield image detector positioned to detect a reflected darkfield image from said each point of interest on said first pattern on said specimen independent of a brightfield image at said each point of interest;
• a reflected brightfield image detector positioned to detect a reflected brightfield image from said each point of interest on said first pattern on said specimen independent of a darkfield image at said each point of interest;
• a reflected darkfield comparator coupled to said darkfield detector to generate a darkfield difference signal at said each point of interest by comparing said reflected darkfield image from said darkfield image detector and said reflected darkfield image from said second pattern to develop a reflected darkfield difference signal at each corresponding point of interest in each of said first and second patterns;
• a reflected brightfield comparator coupled to said brightfield detector to generate a brightfield difference signal at said each point of interest by comparing said reflected brightfield image from said brightfield image detector and said reflected brightfield image from said second pattern to develop a reflected brightfield difference signal at said each corresponding point of interest in each of said first and second patterns;
• and
• a processor coupled to said darkfield and brightfield comparators to utilize both of said reflected darkfield and brightfield difference signals at said each point of interest as coordinates of a reflected pattern defect map.

A method of inspection of a first pattern on a specimen for defects against a second pattern that is intended to be the same, said second pattern has known first and second responses to at least one probe, said method comprising the steps of:

• a. applying said at least one probe to each point of said first pattern on said specimen to generate at least two responses from said each point of said first pattern;
• b. detecting a first response from said each point of said first pattern;
• c. detecting a second response from said each point of said first pattern;
• d. comparing said first response of step b. against said first response from the same point of said second pattern to develop a first response difference signal at said each point;
• e. comparing said second response of step c. against said second response from the same point of said second pattern to develop a second response difference signal at said each point;
• and
• f. processing said first and second response difference signals from steps d. and e. together as coordinates to unilaterally determine a first pattern defect map.

An inspection system to inspect a first pattern on a specimen for defects against a second pattern that is intended to be the same, said second pattern has known first and second responses to at least one probe, said inspection system comprising:

• at least one probe to each point of said first pattern on said specimen to generate at least two responses from said each point of said first pattern on said specimen;
• a first response detector positioned to detect said first response from said each point of said first pattern on said specimen;
• a second response detector positioned to detect said second response from said each point of said first pattern on said specimen;
• a first response comparator coupled to said first response detector to generate a first response difference signal by comparing the output from said first response detector and said first response from the same point of said second pattern to develop a first response difference signal at said each point;
• a second response comparator coupled to said second response detector to generate a second response difference signal by comparing the output from said second response detector and said second response from the same point of said second pattern to develop a second response difference signal at said each point;
• and
• a processor coupled to said first and second response comparators to process said first and second response difference signals together as coordinates to unilaterally determine a first pattern defect map.

A method of inspection of a first pattern on a specimen for defects to be compared against a second pattern that is intended to be the same, said second pattern having known reflected darkfield and brightfield images each resulting from different selected frequencies of illumination at each point of interest, said method comprising the steps of:

• a. illuminating said first pattern on said specimen with brightfield illumination from a single brightfield illumination source, and darkfield illumination from a plurality of darkfield illumination sources, each brightfield and darkfield illumination source having a different illumination frequency, the different illumination frequencies resulting in distinguishable darkfield and brightfield images of said first pattern;
• b. separately detecting a plurality of reflected darkfield images from said first pattern resulting from each of said plurality of darkfield illumination sources at said each point of interest independent of a brightfield image at said each point of interest;
• c. detecting a reflected brightfield image from said first pattern at said each point of interest independent of a darkfield image at said each point of interest;
• d. comparing said reflected darkfield images of step b. against said reflected darkfield image from corresponding illumination frequencies from said second pattern to develop a plurality of reflected darkfield difference signals at said each corresponding point of interest in each of said first and second patterns;
• e. comparing said reflected brightfield image of step c. against said reflected brightfield image from said second pattern to develop a reflected brightfield difference signal at said each corresponding point of interest in each of said first and second patterns;
• and
• f. utilizing said reflected darkfield and brightfield difference signals of steps d. and e. together at said each point of interest as coordinates of a combined pattern reflected defect map.

A method of inspection of a first pattern on a specimen for defects to be compared against a second pattern that is intended to be the same, said second pattern having known reflected darkfield and brightfield images each resulting from different selected frequencies of illumination at each point of interest, said method comprising the steps of:

• a. illuminating said first pattern on said specimen with darkfield illumination from a single darkfield illumination source, and brightfield illumination from a plurality of brightfield illumination sources, each brightfield and darkfield illumination source having a different illumination frequency, the different illumination frequencies resulting in distinguishable darkfield and brightfield images of said first pattern;
• b. separately detecting a plurality of reflected brightfield images from said first pattern resulting from each of said plurality of brightfield illumination sources at said each point of interest independent of a darkfield image at said each point of interest;
• c. detecting a reflected darkfield image from said first pattern at said each point of interest independent of a brightfield image at said each point of interest;
• d. comparing said reflected darkfield image of step c. against said reflected darkfield image from said second pattern to develop a reflected darkfield difference signal at said each corresponding point of interest in each of said first and second patterns;
• e. comparing said reflected brightfield images of step b. against said reflected brightfield images from corresponding illumination frequencies from said second pattern to develop a plurality of reflected brightfield difference signals at said each corresponding point of interest in each of said first and second patterns;
• and
• f. utilizing said reflected darkfield and brightfield difference signals of steps d. and e. together at said each point of interest as coordinates of a combined pattern reflected defect map.

A method of inspection of a first pattern on a specimen for defects to be compared against a second pattern that is intended to be the same, said second pattern having known reflected darkfield and brightfield images each resulting from different selected frequencies of illumination at each point of interest, said method comprising the steps of:

• a. illuminating said first pattern on said specimen with darkfield illumination from a plurality of darkfield illumination sources, and brightfield illumination from a plurality of brightfield illumination sources, each of said brightfield and darkfield illumination sources having a different illumination frequency, the different illumination frequencies resulting in distinguishable darkfield and brightfield images of said first pattern;
• b. separately detecting a plurality of reflected brightfield images from said first pattern resulting from each of said plurality of brightfield illumination sources at said each point of interest independent of a darkfield image at said each point of interest;
• c. separately detecting a plurality of reflected darkfield images from said first pattern resulting from said plurality of darkfield illumination sources at said each point of interest independent of a brightfield image at said each point of interest;
• d. comparing said reflected darkfield images of step c. against said reflected darkfield images from corresponding illumination frequencies from said second pattern to develop a plurality of reflected darkfield difference signals at said each corresponding point of interest in each of said first and second patterns;
• e. comparing said reflected brightfield images of step b. against said reflected brightfield images from corresponding illumination frequencies from said second pattern to develop a plurality reflected brightfield difference signals at said each corresponding point of interest in each of said first and second patterns;
• and
• f. utilizing said reflected darkfield and brightfield difference signals of steps d. and e. together at said each point of interest as coordinates of a combined pattern reflected defect map.

An inspection system to inspect a first pattern on a specimen for defects to be compared against a second pattern that is intended to be the same, said second pattern has known reflected darkfield and brightfield images each resulting from different selected frequencies of illumination at each point of interest, said inspection system comprising:

• an illumination system including:
• a brightfield illumination subsystem having a single brightfield illumination source to illuminate said first pattern on said specimen;
• and
• a darkfield illumination subsystem having a plurality of darkfield illumination sources to illuminate said first pattern on said specimen;
• with each of said brightfield and darkfield illumination sources having a different illumination frequency resulting in distinguishable reflected brightfield and darkfield images on said first pattern;
• a darkfield image detector positioned to individually detect reflected darkfield images from said each point of interest on said first pattern on said specimen resulting from each of said plurality of darkfield illumination sources independent of a brightfield image at said each point of interest;
• a brightfield image detector positioned to detect a reflected brightfield image from said each point of interest on said first pattern on said specimen independent of a darkfield image at said each point of interest;
• a darkfield comparator coupled to said darkfield image detector to generate a plurality of darkfield difference signals by comparing said reflected darkfield image from said darkfield image detector and said reflected darkfield images from corresponding illumination frequencies from said second pattern to develop a plurality of reflected darkfield difference signals at said each corresponding point of interest in each of said first and second patterns;
• a brightfield comparator coupled to said brightfield detector to generate a brightfield difference signal by comparing said reflected brightfield image from said brightfield image detector and said reflected brightfield image from said second pattern to develop a reflected brightfield difference signal at said each corresponding point of interest in each of said first and second patterns;
• and
• a processor coupled to said darkfield and brightfield comparators to utilize said reflected darkfield and brightfield difference signals together at said each point of interest as coordinates of a first pattern reflected defect map.

An inspection system to inspect a first pattern on a specimen for defects to be compared against a second pattern that is intended to be the same, said second pattern has known reflected darkfield and brightfield images each resulting from different selected frequencies of illumination at each point of interest, said inspection system comprising:

• an illumination system including:
• a darkfield illumination subsystem having a single darkfield illumination source to illuminate said first pattern on said specimen;
• and
• a brightfield illumination subsystem having a plurality of brightfield illumination sources to illuminate said first pattern on said specimen;
• with each of said brightfield and darkfield illumination sources having a different illumination frequency resulting in distinguishable reflected brightfield and darkfield images on said first pattern;
• a brightfield image detector positioned to individually detect reflected brightfield images from said each point of interest on said first pattern on said specimen resulting from each of said plurality of brightfield illumination sources independent of a darkfield image at said each point of interest;
• a darkfield image detector positioned to detect a reflected darkfield image from said each point of interest on said first pattern on said specimen independent of a brightfield image at said each point of interest;
• a brightfield comparator coupled to said brightfield image detector to generate a plurality of brightfield difference signals by comparing said reflected brightfield images from said brightfield image detector and said reflected brightfield images from corresponding illumination frequencies from said second pattern to develop a plurality of reflected brightfield difference signals at said each corresponding point of interest in each of said first and second patterns;
• a darkfield comparator coupled to said darkfield detector to generate a darkfield difference signal by comparing said reflected darkfield image from said darkfield image detector and said reflected darkfield image from said second pattern to develop a reflected darkfield difference signal at each said corresponding point of interest in each of said first and second patterns;
• and
• a processor coupled to said darkfield and brightfield comparators to utilize said reflected darkfield and brightfield difference signals together at said each point of interest as coordinates of a first pattern reflected defect map.

An inspection system to inspect a first pattern on a specimen for defects to be compared against a second pattern that is intended to be the same, said second pattern has known reflected darkfield and brightfield images each resulting from different selected frequencies of illumination at each point of interest, said inspection system comprising:

• an illumination system including:
• a darkfield illumination subsystem having a plurality of darkfield illumination sources to illuminate said first pattern on said specimen;
• and
• a brightfield illumination subsystem having a plurality of brightfield illumination sources to illuminate said first pattern on said specimen;
• with each of said brightfield and darkfield illumination sources having a different illumination frequency resulting in distinguishable reflected brightfield and darkfield images on said first pattern;
• a brightfield image detector positioned to individually detect reflected brightfield images from said each point of interest on said first pattern on said specimen resulting from each of said plurality of brightfield illumination sources independent of a darkfield image at said each point of interest;
• a darkfield image detector positioned to individually detect a plurality of reflected darkfield images from said each point of interest on said first pattern on said specimen resulting from each of said plurality of darkfield illumination sources independent of a brightfield image at said each point of interest;
• a brightfield comparator coupled to said brightfield image detector to generate a plurality of brightfield difference signals by comparing said reflected brightfield images from said brightfield image detector and said reflected brightfield images from corresponding illumination frequencies from said second pattern to develop a plurality of reflected brightfield difference signals at said each corresponding point of interest in each of said first and second patterns;
• a darkfield comparator coupled to said darkfield detector to generate a plurality of darkfield difference signals by comparing said reflected darkfield images from said darkfield image detector and said reflected darkfield images from corresponding illumination frequencies from said second pattern to develop a plurality of reflected darkfield difference signals at said each corresponding point of interest in each of said first and second patterns;
• and
• a processor coupled to said darkfield and brightfield comparators to utilize said reflected darkfield and brightfield difference signals together at said each point of interest as coordinates of a first pattern reflected defect map.