Mask blanks inspection tool
First Claim
1. A system comprising:
- a source of extreme ultraviolet (EUV) light to illuminate a multilayered patterning mask blank;
a first spherical mirror having a first perimeter and an opening, the first mirror designed to reflect scattered light to be received from a multilayered patterning mask blank illuminated by the source;
a second spherical mirror having a second perimeter smaller than the first perimeter, the second mirror designed to reflect the scattered light received from the first spherical mirror through the opening and to a detector; and
a first comparator coupled to the detector to compare a first threshold value to a pixel reflective light intensity value received by the detector for a first pixel of a multilayered patterning mask blank;
a second comparator coupled to the detector to compare a second threshold value to a pixel reflective light intensity value received by the detector for a plurality of pixel block reflective light intensity values for a pixel block of the multilayered patterning mask blank, wherein the pixel block includes the pixel.
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Accused Products
Abstract
Embodiments include determining whether defects exist in an extreme ultraviolet (EUV) light mask blank. Incident EUV light scattered or diffused by abnormalities in the layers of the mask blank may be measured, normalized, and compared to threshold values to determine if and where a defect exists. Normalizing may be performed by dividing a light intensity value for a pixel by the average of light intensity values for one or more rings of surrounding pixels. A defect may be determined by considering whether the normalized intensity value for a pixel is greater than a pixel threshold to identify the pixel is a candidate for a location with a defect; and by determining whether the sum of normalized light intensity values for a block of pixels including the pixel satisfies a pixel block threshold to determine whether the block scatters or diffuses a critical amount of light to identify a defect.
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Citations
18 Claims
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1. A system comprising:
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a source of extreme ultraviolet (EUV) light to illuminate a multilayered patterning mask blank;
a first spherical mirror having a first perimeter and an opening, the first mirror designed to reflect scattered light to be received from a multilayered patterning mask blank illuminated by the source;
a second spherical mirror having a second perimeter smaller than the first perimeter, the second mirror designed to reflect the scattered light received from the first spherical mirror through the opening and to a detector; and
a first comparator coupled to the detector to compare a first threshold value to a pixel reflective light intensity value received by the detector for a first pixel of a multilayered patterning mask blank;
a second comparator coupled to the detector to compare a second threshold value to a pixel reflective light intensity value received by the detector for a plurality of pixel block reflective light intensity values for a pixel block of the multilayered patterning mask blank, wherein the pixel block includes the pixel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification