Method of and preventing focal plane anomalies in the focal plane of a projection system
AssigneeASML Netherlands B.V.
InventorsIngrid Minnaert-Janssen, Johannes Jacobus Matheus Baselmans, Frits Jurgen Van Hout, Peter Van Oorschot, Christian Wagner, Adriaan Roelof Van Zwol, Roderik Willem Van Es, Petrus Augustinus Marie Van Der Wielen, Hubrecht Lodewijk Van Ginneken
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Abstract
To reduce and prevent local field anomalies created localized thinning of the coating of optical elements in the apparatus. The projection system is flood exposed to an intense beam of radiation for a substantial period of time. As the rate of thinning of the coating decreases with time, a uniform coating results.
Claims24
A method of decreasing focal plane anomalies of a focal plane of a projection system of a lithographic projection apparatus comprising:
- exposing the projection system to an intense beam of radiation for a substantial period of time until a rate of thinning of a coating of an optical element of the projection system is substantially reduced.
A method of decreasing focal plane anomalies of the focal plane of a projection system of a lithographic projection apparatus comprising:
- exposing the projection system to an intense beam of radiation for a substantial period of time until a rate of thinning of a coating of an optical element of the projection system is substantially reduced, wherein the method is carried out in a lithographic projection apparatus comprising a radiation system for providing a projection beam of radiation.
A method of pre-treating a projection system to substantially prevent focal plane anomalies of the focal plane of a projection system of a lithographic projection apparatus due to optical element coating thinning comprising:
- exposing the projection system to an intense beam of radiation for a substantial period of time until a rate of thinning of a coating of an optical element of the projection system is substantially reduced.
A method of decreasing optical aberrations of a projection system of a lithographic projection apparatus comprising:
- exposing the projection system to an intense beam of radiation for a substantial period of time until a rate of thinning of a coating of an optical element of the projection system is substantially reduced.
A method of decreasing focal plane anomalies of the focal plane of a projection system of a lithographic projection apparatus comprising:
- exposing the projection system to an intense beam of radiation for a substantial period of time until a rate of thinning of a coating of an optical element of the projection system is substantially reduced, said exposing being carried out in a lithographic projection apparatus comprising a radiation system for providing a projection beam of radiation and a substrate table for holding a substrate, and
- reflecting said intense beam of radiation back into the projection system during exposure with said substrate.
A dummy mask comprising a plane glass plate for diverging radiation to fill a projection system.
A lithographic apparatus comprising a projection system and a machine readable medium comprising machine executable instructions for:
- measuring focal plane anomalies of the focal plane in the projection system, and
- exposing the projection system to an intense beam of radiation for a substantial period of time when the measured focal plane anomalies exceed a preselected value.
A method comprising:
- measuring at least one focal plane anomaly of a focal plane in a projection optical system of a lithographic apparatus;
- comparing the measured anomaly to a preselected threshold value;
- and
- when the measured anomaly exceeds the preselected threshold value, exposing the projection system to a beam of radiation so that a rate of thinning of a coating of an optical element of the projection optical system is substantially reduced.
Dependencies are inferred from the claim text.