Lithographic method to apply a pattern to a substrate and lithographic apparatus
A slit shaped area of a patterning device is illuminated to impart a radiation beam with a pattern in its cross-section. A projection system projects the patterned radiation beam onto a target portion of a substrate. As the radiation beam is scanned across the target portion of the substrate, a configuration of the projection system is adjusted and applies a pattern to the target portion. The adjusting may affect a magnitude of an image magnification component of the projection system, along the length of the slit shaped area, or an image distortion in a scan direction. The adjusting is arranged to compensate an effect on pattern overlay accuracy of a distortion of the patterning device.
1. A lithographic method to apply a pattern to a substrate comprising:
illuminating a slit shaped area, elongated along a first direction, of a patterning device with a radiation beam to provide a patterned radiation beam;
scanning the patterning device through the radiation beam in a scan direction perpendicular to the first direction;
imaging the patterned radiation beam onto a target portion of the substrate using a projection system, a characteristic of the projection system being an image magnification component along the first direction, and an image distortion component along the scan direction;
synchronously scanning the substrate along the scan direction;
applying an adjustment to the image magnification component as the substrate is scanned across a footprint of the radiation beam corresponding to the slit shaped area, the adjustment being a function of a distance in the scan direction between a center of the footprint of the radiation beam corresponding to the slit shaped area and a center of the target portion; and
applying a supplementary adjustment to the image distortion component as the substrate is scanned across the footprint of the radiation beam, the supplementary adjustment being a function of a distance in the first direction between the center of the footprint of the radiation beam and the center of the target portion.
2. The method of claim 1 , wherein the adjustment is determined by combining the distance in the first direction between the center of the footprint and the center of the target portion and the square of the distance in the scan direction between the center of the footprint and the center of the target portion.
3. The method of claim 2 , wherein the supplementary adjustment is determined by combining the distance in the scan direction between the center of the footprint and the center of the target portion and the square of the distance in the first direction between the center of the footprint and the center of the target portion.
4. The method of claim 1 , wherein the supplementary adjustment is determined by combining the distance in the scan direction between the center of the footprint and the center of the target portion and the square of the distance in the first direction between the center of the footprint and the center of the target portion.