Process margin using discrete assist features
First Claim
1. A method of improving a process margin of a lithographic imaging system, comprising:
- identifying a semi-isolated pattern feature on a mask as a potential limiting factor to a process margin for a lithographic imaging technique;
determining a resolution threshold for the imaging technique;
determining a maximum size threshold for discrete scatterbar segments based at least in part on the determined resolution threshold for the imaging system and a known amount line-end pull back that occurs at the resolution threshold; and
mitigating a resist residue by placing a discrete scatterbar comprising more than one discrete sub-resolution scatterbar segment near the semi-isolated mask featureConstructing the more than one discrete scatterbar segments with a pitch outside of a range of pitches that can be resolved perpendicular to an axis of a dipole illumination source, and within a range of pitches that can be resolved parallel to the axis of the dipole illumination source, and orienting the discrete scatterbar perpendicular to the axis to mitigate discrete scatterbar segments resolution by the imaging system.
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Abstract
The subject invention provides a system and method for improving the process margin of a lithographic imaging system. The process margin improvement is achieved through the novel placement of discrete assist features and/or the use of forbidden pitches and specific pitch orientations. Novel geometries are utilized, which take advantage of line-end pull back and/or a lack of resolution of pitches perpendicular to an axis of a dipole illumination source. The strategic placement of a series of discrete scatterbar segments on a mask near positions of critical features, such as, for example, contacts, mitigates resist residue that can result from the use of a contiguous scatterbar.
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Citations
19 Claims
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1. A method of improving a process margin of a lithographic imaging system, comprising:
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identifying a semi-isolated pattern feature on a mask as a potential limiting factor to a process margin for a lithographic imaging technique; determining a resolution threshold for the imaging technique; determining a maximum size threshold for discrete scatterbar segments based at least in part on the determined resolution threshold for the imaging system and a known amount line-end pull back that occurs at the resolution threshold; and mitigating a resist residue by placing a discrete scatterbar comprising more than one discrete sub-resolution scatterbar segment near the semi-isolated mask feature Constructing the more than one discrete scatterbar segments with a pitch outside of a range of pitches that can be resolved perpendicular to an axis of a dipole illumination source, and within a range of pitches that can be resolved parallel to the axis of the dipole illumination source, and orienting the discrete scatterbar perpendicular to the axis to mitigate discrete scatterbar segments resolution by the imaging system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 15, 16, 17, 18, 19)
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8. A photomask comprising:
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one or more semi-isolated mask features; and one or more discretized scatterbars positioned near at least one of the one or more semi-isolated mask features, the one or more discretized scatterbar comprises more than one discrete sub-resolution scatterbar segment wherein each of the more than one discrete sub-resolution scatterbar segments is constructed smaller than a predefined maximum segment size threshold in only one transverse direction to incident illumination and based on a determined line-end pull, below which the imaging system does not generate an image, the discretized scatterbars alter a pitch of the one or more semi-isolated mask features and mitigate photoresist residue after an exposure period. - View Dependent Claims (9, 10, 11, 12)
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13. A system that facilitates improving wafer yield after a photoresist exposure technique, comprising:
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means for identifying a potential yield-limiting pattern feature on a photomask; means for determining a maximum size threshold for discrete scatterbar segments based at least in part on a resolution limit perpendicular to an axis of a dipole illuminator, which is poorer than a resolution limit parallel to the dipole illuminator axis; and means for mitigating a resist residue by generating a plurality of discrete scatterbar segments that are of a sub-resolution size relative the perpendicular resolution limit, and are not sub-resolution size relative the parallel resolution limit, and orienting the discrete scatterbar segments perpendicular to the axis of the dipole illuminator to mitigate scatterbar segment resolution means for constructing the more than one discrete scatterbar segments with a pitch outside of a range of pitches that can be resolved perpendicular to an axis of a dipole illumination source, and within a range of pitches that can be resolved parallel to the axis of the dipole illumination source, and orienting the discrete scatterbar perpendicular to the axis to mitigate discrete scatterbar segments resolution by the imaging system. - View Dependent Claims (14)
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Specification