Exact transmission balanced alternating phase-shifting mask for photolithography
First Claim
1. A method of eliminating pattern size and placement inaccuracies caused by errors in the relative amount of light transmitted through transparent features of different phase on a phase-shifted photomask, the method comprising the steps of:
- building design data of said photomask representing pattern size, shape, placement and phase of said transparent features;
modifying said design data by altering the size or shape of at least one of said phase-shifted features;
fabricating said photomask with said modified design data by forming opaque and transparent features of said photomask and selectively etching transparent material of said photomask to a depth which establishes the phases of said transparent phase-shifted features, thereby partially reducing said transmission errors; and
subjecting said photo-mask to an etch-back process comprising adjusting edge locations of said transparent material within said etched features in relation to edge locations of said opaque film of said photomask to a position wherein residual transmission errors between said features having a different phase on said photomask are corrected, thereby eliminating said residual transmission errors that were not previously corrected by a combination of said design data modification step and said fabrication step.
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Accused Products
Abstract
A two-step method for eliminating transmission errors in alternating phase-shifting masks is described. Initially, the design data is selectively biased to provide a coarse reduction in the inherent transmission error between features of different phase, size, shape, and/or location. During fabrication of the mask with the modified data, residual transmission errors are then eliminated via the positioning of the edges of the etched-quartz trenches which define the phase of a given feature to a set location beneath the opaque chrome film. Application of feedback, in which the aerial image of the mask is monitored during the positioning of the etched-quartz edges, provides additional and precise control of the residual transmission error.
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Citations
22 Claims
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1. A method of eliminating pattern size and placement inaccuracies caused by errors in the relative amount of light transmitted through transparent features of different phase on a phase-shifted photomask, the method comprising the steps of:
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building design data of said photomask representing pattern size, shape, placement and phase of said transparent features; modifying said design data by altering the size or shape of at least one of said phase-shifted features; fabricating said photomask with said modified design data by forming opaque and transparent features of said photomask and selectively etching transparent material of said photomask to a depth which establishes the phases of said transparent phase-shifted features, thereby partially reducing said transmission errors; and subjecting said photo-mask to an etch-back process comprising adjusting edge locations of said transparent material within said etched features in relation to edge locations of said opaque film of said photomask to a position wherein residual transmission errors between said features having a different phase on said photomask are corrected, thereby eliminating said residual transmission errors that were not previously corrected by a combination of said design data modification step and said fabrication step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of eliminating pattern size and placement inaccuracies caused by errors in the relative amount of light transmitted through transparent features of different phase on a phase-shifted photomask, the method comprising the steps of:
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building design data of said photomask representing pattern size, shape, placement and phase of said transparent features; selectively biasing said design data, said biasing including altering the size or shape of at least one of said phase-shifted features; fabricating said photomask with said modified design data, forming opaque and transparent features of said photomask and selectively etching transparent material of said photomask to a depth which establishes the phases of said transparent phase-shifted features, said selective biasing of said design data coupled to said fabricating said photomask with said modified design data providing a first reduction of said transmission errors between said features; and subjecting said photo-mask to an etch-back process comprising adjusting edge locations of said transparent material within said etched features in relation to edge locations of said opaque film of said photomask to a position, wherein residual transmission errors between said features having a different phase on said photomask that were not previously corrected by a combination of said design data modification step and said fabrication step are eliminated.
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Specification