Method and imaging apparatus for imaging a structure onto a semiconductor wafer by means of immersion lithography
View Patent ↗The hydrodynamic effects—which occur during immersion lithography as a result of the movement of the semiconductor wafer—in a liquid preferably provided between the last lens surface of the projection system and the semiconductor wafer can be avoided by means of a movable illumination region for illuminating a cutout of a mask containing a structure to that can be imaged onto the semiconductor wafer. A scan movement of the mask and the semiconductor wafer can be either reduced or entirely avoided by means of a movement of the illumination region.
1. A method for imaging a structure from a mask onto a semiconductor wafer, comprising the steps of:
exposing a cutout of the mask provided in an x-y plane with the aid of an illumination region arranged above the mask;
imaging a partial structure comprised in the exposed cutout onto the semiconductor wafer by means of a projection system;
filling a gap with liquid between the semiconductor wafer and a lens surface of the projection system that is nearest to the semiconductor wafer;
moving the illumination region with respect to the mask and the projection system in the x-y plane, so that the structure prescribed by the mask is imaged onto the semiconductor wafer by a sequence of imagings of the partial structure respectively contained in the successively exposed cutouts, in order to repeat the imaging of the structure on the semiconductor wafer;
interrupting a contact between the semiconductor wafer and the liquid;
moving the semiconductor wafer to a new position with regard to the projection system, so that the repeated imaging of the structure is effected onto an as yet unexposed section of the semiconductor wafer;
providing the liquid between the semiconductor wafer and the lens surface;
moving the semiconductor wafer into a focal range of the projection system; and
repeating the imaging of the structure onto the semiconductor wafer.
2. The method as claimed in claim 1 , wherein the illumination region includes a slotted form.
3. The method as claimed in claim 1 , wherein the illumination region is moved in substantially one direction.
4. The method as claimed in claim 1 , wherein the mask and the semiconductor wafer, during the imaging of the structure, are provided with a fixed position in the x-y plane with respect to the projection system.
5. The method as claimed in claim 1 , wherein the mask and the semiconductor wafer, during the imaging of the structure, are moved in the x-y plane in each case with respect to the projection system.
6. The method as claimed in claim 5 , wherein the semiconductor wafer is moved with a direction substantially parallel to the direction of movement of the illumination region and the mask is moved with a direction substantially antiparallel.
7. The method as claimed in claim 1 , wherein in order to interrupt the contact between the semiconductor wafer and the liquid, the semiconductor wafer is moved away from the lens surface in a z direction substantially perpendicular to the x-y plane at least until contact with the liquid is broken.
8. The method as claimed in claim 7 , wherein in order to bring the semiconductor wafer to the new position with regard to the projection system, the semiconductor wafer is moved in the x-y plane and the semiconductor wafer is moved in the z direction toward the lens surface until a gap between the semiconductor wafer and the lens surface is substantially filled by the liquid.