Element for defocusing tm mode for lithography
OwnerGabriel Y. Sirat, Joseph Fisherinventors
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Abstract
A method for imaging a mask pattern with small features through a lithographic system includes an illumination source and providing a uniaxial material having an ordinary index of refraction and a different extraordinary index of refraction. The extraordinary mode is modified such that the extraordinary mode is defocused relative to the ordinary mode. Light from the illumination source is passed through the material and focusing the ordinary mode on an image plane and defocusing the extraordinary mode relative to the image plane.
Claims37
A method for imaging a mask pattern with small features through a lithographic system:
- providing an illumination source;
- providing a uniaxial material having an ordinary index of refraction and a different extraordinary index of refraction;
- modifying the extraordinary mode such that the extraordinary mode is defocused relative to the ordinary mode;
- passing light from the illumination source through the material and focusing the ordinary mode on an image plane and defocusing the extraordinary mode relative to the image plane.
A lithographic system for imaging a mask pattern with small features through a lithographic system:
- an illumination source;
- a uniaxial material having an ordinary index of refraction and a different extraordinary index of refraction, the material being configured to focus the ordinary mode on an image plane and to modify the extraordinary mode such that the extraordinary mode is defocused relative to the ordinary mode;
- a photoresist positioned at an image plane, wherein the ordinary mode from the illumination source is focused on the image plane and the extraordinary mode is defocused relative to the image plane.
A lithographic apparatus having a projection objective for imaging a pattern provided in an object plane of the projection objective onto an image plane of the projection objective suitable for microlithography projection exposure machines comprising:
- a UV light source providing light;
- a polarization controller to control the polarization of the light;
- an optical module to shape the spatial profile of the light;
- a mask to define a pattern;
- optical elements including a last optical element placed along a geometric axis;
- a wafer and a photoresist coated on the wafer placed such that the photoresist is positioned at the image plane of the projection objective;
- and
- an immersion liquid filled in between the last optical element and the wafer, wherein the last optical element is in the form of a plano-convex lens, with the flat surface oriented facing the wafer and up against the immersion liquid,
- wherein the material of the last optical element is made of uniaxial crystal,
- wherein the optical axis of the uniaxial crystal is perpendicular to the bottom surface of the last optical element,
- wherein an image is created in the wafer in a preferred polarization, by the projection objective,
- wherein unwanted polarization creates a uniform background in the photoresist.
A method of immersion lithography comprising:
- providing a UV light source providing light;
- providing a polarization controller to control the polarization of the light;
- providing an optical module to shape the spatial profile of the light;
- providing a mask to define a pattern;
- providing optical elements including a last optical element placed along a geometric axis;
- a wafer and a photoresist coated on the wafer placed such that the photoresist is positioned at the image plane of the projection objective;
- and
- filling an immersion liquid between the last optical element and the wafer;
- wherein the last optical element is in the form of a plano-convex lens, with the flat surface oriented facing the wafer and up against the immersion liquid,
- wherein the material of the last optical element is made of uniaxial crystal,
- wherein the optical axis of the uniaxial crystal is perpendicular to the bottom surface of the last optical element;
- creating an image on the wafer in a preferred polarization,
- creating a uniform background in the photoresist from unwanted polarization.
A projection objective for imaging a pattern provided in an object plane of the projection objective onto an image plane of the projection objective suitable for microlithography projection exposure machines, comprising:
- a UV light source providing light;
- a polarization controller to control the polarization of the light;
- an optical module to shape the spatial profile of the light;
- a mask to define a pattern;
- optical elements including a last optical element placed along a geometric axis;
- a wafer and a photoresist coated on the wafer placed such that the photoresist is positioned at the image plane of the projection objective;
- and
- wherein the photoresist is kept at a distance from the last optical element to neutralize the decay of high frequency spatial components due to non propagating waves,
- wherein the last optical element is in the form of a plano-convex lens, with the flat surface oriented facing the wafer,
- wherein the material of the last optical element is made of uniaxial crystal,
- wherein the optical axis of the uniaxial crystal is perpendicular to the bottom surface of the last optical element,
- wherein an image is created in the wafer in a preferred polarization, by the projection objective,
- wherein unwanted polarization creates a uniform background in the photoresist.
Dependencies are inferred from the claim text.