Beam-splitter optics design that maintains an unflipped (unmirrored) image for a catadioptric lithographic system
View Patent ↗The present invention is a catadioptric system having a reticle optical group, a beam splitter, an aspheric mirror, a baffle plate, a folding mirror and a semiconductor wafer optical group. The reticle optical group, the beam splitter and the semiconductor wafer optical group are placed on the same beam axis, different from aspheric mirror and folding mirror axis. The light passes through an image pattern on the reticle and is reflected by the beam splitter onto the aspheric mirror. The aspheric mirror reflects the light back through the beam splitter onto the folding mirror. The folding mirror reflects the light back to the beam splitter. The beam splitter reflects the light onto the semiconductor wafer optical group. A plurality of quarter wave plates can be placed in optical paths between optical elements of the present invention to change polarization of an incoming light. Before light passes through the semiconductor wafer optical group, it passes through the baffle plate, which prevents any background scattered light caused by internal reflections within the beam splitter from entering the semiconductor wafer optical group. In another embodiment, a spacer plate is inserted into the beam splitter. The spacer plate creates an offset between reticle optical group beam axis and semiconductor wafer optical group beam axis. This reduces direct passage of light from reticle optical group to semiconductor wafer optical group.
1. A device manufacturing method, comprising:
(a) patterning a beam of radiation;
(b) reflecting the patterned beam first through fourth times, the first and fourth reflections being performed with a beam splitter; and
(c) projecting the reflected patterned beam onto a target portion of a substrate.
2. The method of claim 1 , wherein the first reflection is performed using a prism that is provided within the beam splitter.
3. The method of claim 1 , wherein the second reflection is performed using an aspheric mirror.
4. The method of claim 1 , wherein the third reflection is performed using a folding mirror.
5. The method of claim 1 , wherein the fourth reflection is performed using a prism that is provided within the beam splitter.
6. The method of claim 1 , further comprising blocking backscattered light before step (c).
7. The method of claim 1 , further comprising polarizing the patterned beam at least one of before, during and after step (b).
8. A system, comprising:
a patterning device that patterns a beam of radiation;
a reflecting system that is configured to reflect the patterned beam first through fourth times, the reflecting system including a beam splitter that is configured to perform the first and fourth reflections; and
a projection system that projects the reflected patterned beam onto a target portion of a substrate.
9. The system of claim 8 , wherein the beam splitter comprises a prism, such that the first reflection is performed using the prism.
10. The system of claim 8 , wherein the reflecting system includes an aspheric mirror, and the second reflection is performed using the aspheric mirror.
11. The system of claim 8 , wherein the reflecting system includes a folding mirror, and the third reflection is performed using the folding mirror.
12. The system of claim 8 , wherein the beam splitter comprises a prism, such that the fourth reflection is performed using the prism.
13. The system of claim 8 , further comprising:
a blocking device that blocks backscattered light.
14. The system of claim 10 , further comprising:
at least one polarizing device located at least one of within and adjacent the reflecting system.