Illumination system with spatially controllable partial coherence compensating for line width variances
An illumination system having an array optical element with different illumination regions corresponding or matched to different line width variations printed on a photosensitive material. The array optical element may be a filter, diffractive optical element, or micro lens array having illumination regions producing different types of illumination properties or characteristics. Each of the illumination regions are matched or correspond to a respective region on a patterning device to provide optimized exposure of a photosensitive material. The optical element may be used to tailor a conventional illumination system to the unique characteristics of the projection optics used in a system, thereby compensating for vertical and horizontal bias or variations in line width for features oriented in the vertical and horizontal direction.
1. A system, comprising:
an illumination source that produces a beam of radiation;
an optical element having regions that change at least one of partial coherence and fill geometry of the beam, each of the regions producing a different change to the beam to correspondingly modify line width at an image plane;
a patterning device that patterns the beam; and
projection optics that project the patterned beam onto a the image plane.
2. The system of claim 1 , wherein said optical element is a microlens array.
3. The system of claim 2 , wherein the micro lens array comprises hexagonal close packed parabolic lenslets.
4. The system of claim 2 , wherein the micro lens array includes conical lenslets.
5. The system of claim 2 , wherein the micro lens array includes pyramidal lenslets.
6. The system of claim 1 , wherein said optical element is a diffractive optical element.
7. A method, comprising:
(a) identifying spatial locations on a printed photosensitive coating having variations in printed line widths; and
(b) changing partial coherence or fill geometry in portions of a beam of radiation based on step (a), each of the portions corresponding to a respective one of the spatial locations to compensate for the variation at the respective one of the spatial locations,
whereby local modifications to line width are made thereby reducing local line width variations.
8. The method of claim 7 , wherein step (b) comprises:
placing an optical element, having differing illumination regions, between an illumination source and a patterning device.
9. The method of claim 7 , wherein step (b) affects the printed line widths oriented in a single direction only.
10. A method, comprising:
forming a rectangular illumination field having a longitudinal dimension;
identifying locations on a photosensitive coating of an object having horizontal/vertical bias introduced by projection optics;
determining required changes in cones of illumination in the longitudinal dimension of the rectangular illumination field needed to compensate for the horizontal/vertical bias introduced by the projection optics to accurately reproduce an image formed from a means for patterning;
modifying the cones of illumination in the illumination field along the longitudinal dimension with an optical element according to the required changes; and
scanning the rectangular illumination field across the means for patterning,
whereby horizontal/vertical bias introduced by the projection optics is substantially corrected improving imaging performance.
11. The method of claim 10 , wherein the optical element is a diffractive optical element.