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US 7,116,496 B1Granted
High NA large-field unit-magnification projection optical system
AssigneeUltratech, Inc.
InventorRomeo I. Mercado
Life of this patent
Estimating the term…
Abstract
An optical system for projection photolithography is disclosed. The optical system is a modified Dyson system capable of imaging a large field over both a narrow and a broad spectral range. The optical system includes a positive lens group having a positive subgroup of elements that includes at least a plano-convex element and a negative subgroup that includes at least a negative meniscus element. The lens subgroups are separated by a small air space. The positive and negative subgroups constitute a main lens group arranged adjacent to but spaced apart from a concave mirror along the mirror axis. The system also includes a variable aperture stop so that the system has a variable NA. A projection photolithography system that employs the optical system is also disclosed.
Claims35
A projection optical system comprising:
- a concave mirror with an aperture on its optical axis;
- a variable aperture stop located at the concave mirror that determines a numerical aperture (NA) of the system;
- a main lens group with positive refracting power arranged adjacent the mirror and spaced apart therefrom, the main lens group comprising in order towards the mirror:
- a first subgroup having positive refractive power;
- and
- a second subgroup having negative refractive power and spaced apart from first subgroup by an air space;
- and
- first and second prisms each having respective first and second flat surfaces, wherein the second flat surfaces are arranged adjacent the positive subgroup on opposite sides of the optical axis, and wherein the first flat surfaces are arranged adjacent object and image planes, respectively;
- wherein the optical system is anastigmatic, projects an image of a pattern located in said object plane to said image plane at substantially unit magnification and has an exposure field at the image plane that is variable in size depending on the adjustment of the variable aperture stop.
6 more elements
A projection optical system comprising:
- a concave mirror;
- a variable aperture stop located at the mirror and centered on the projection system optical axis that determines a numerical aperture (NA) of the system;
- a main lens group with positive refracting power arranged adjacent the mirror and spaced apart therefrom, the main lens group comprising in order towards the mirror:
- a first subgroup consisting of a doublet lens that consists of, in order towards the mirror, a plano-convex lens with a mirror-facing convex surface and a first negative meniscus lens element with mirror-facing convex, surface;
- and
- a second subgroup consisting of a second negative meniscus lens having mirror-facing convex surfaces, with a concave surface of the second meniscus lens separated from the convex surface of the first negative meniscus lens by an air space;
- and
- first and second prisms each having respective first and second flat surfaces, wherein the second flat surfaces are arranged adjacent the planar surface of the plano-convex lens on opposite sides of the optical axis, and wherein the first flat surfaces are arranged adjacent object and image planes, respectively;
- wherein the optical system is anastigmatic, projects an image of a pattern located in said object plane to said image plane at substantially unit magnification and has an exposure field at the image plane that is adjustable in size by adjusting the variable aperture stop.
6 more elements
A projection lithography system comprising:
- an optical system comprising:
- a concave mirror with an aperture on its optical axis;
- a variable aperture stop located at the concave mirror that determines a numerical aperture (NA) of the system of 0.50 or lower;
- a main lens group with positive refracting power arranged adjacent the mirror and spaced apart therefrom, the main lens group comprising in order towards the mirror:
- a first subgroup having positive refractive power;
- and
- a second subgroup having negative refractive power and spaced apart from first subgroup by an air space;
- and
- first and second prisms each having respective first and second flat surfaces, wherein the second flat surfaces are arranged adjacent the positive subgroup on opposite sides of the optical axis, and wherein the first flat surfaces are arranged adjacent object and image planes, respectively;
- wherein the optical system has an exposure field at the image plane that is adjustable in size by adjusting the variable aperture stop;
- a mask stage capable of supporting a mask at the object plane;
- an illuminator adapted to illuminate the mask with at least one of the g-line, h-line, and I-line wavelengths;
- and
- a wafer stage capable of movably supporting at wafer at the image plane.
11 more elements
A projection lithography system comprising:
- an optical system comprising:
- a concave mirror with an aperture on its optical axis;
- a variable aperture stop located at the concave mirror that determines a numerical aperture (NA) of the system of 0.50 or lower;
- a main lens group with positive refracting power arranged adjacent the mirror and spaced apart therefrom, the main lens group comprising in order towards the mirror:
- a first subgroup consisting of a doublet lens that consists of, in order towards the mirror, a plano-convex lens with a mirror-facing convex surface and a first negative meniscus lens element with mirror-facing convex surface;
- and
- a second subgroup consisting of a second negative meniscus lens having mirror-facing convex surfaces, with a concave surface of the second meniscus lens separated from the convex surface of the first negative meniscus lens by an air space;
- and
- first and second prisms each having respective first and second flat surfaces, wherein the second flat surfaces are arranged adjacent the planar surface of the piano-convex lens on opposite sides of the optical axis, and wherein the first flat surfaces are arranged adjacent object and image planes, respectively;
- wherein the optical system has an exposure field at the image plane that is adjustable in size by adjusting the variable aperture stop;
- a mask stage capable of supporting a mask at the object plane;
- an illuminator adapted to illuminate the mask with at least one of the g-line, h-line, and I-line wavelengths;
- and
- a wafer stage capable of movably supporting a wafer at the image plane.
11 more elements
Dependencies are inferred from the claim text.