Method and apparatus for aerial image analyzer
AssigneeNikon Precision Inc.
InventorMichael R. Sogard
Life of this patent
Estimating the term…
Abstract
A method and apparatus to analyze the aerial image of an optical system using a subwavelength slit. A slit configuration yields a higher signal-to-noise ratio than that achievable with a round aperture. The slit also allows the polarization of the aerial image to be analyzed. In an alternative embodiment a tunneling slit is used. The tunneling slit comprises an optically transparent ridge-like structure mounted to a substrate, the combined structure covered by a thin, planar metal film.
Claims38
A method for optically analyzing the aerial image formed by an optical projection lithography system having a source of light and a light path, comprising:
- positioning a slit in a first plane, said first plane proximate an image plane of said optical lithography system, wherein said slit has an equivalent width less than the wavelength of said source of light;
- moving said slit across and within said first plane, wherein said movement is in a direction perpendicular to the length of said slit;
- and
- detecting the intensity of said light transmitted through said slit as a function of slit position.
A method for optically analyzing the aerial image of an optical projection lithography system having a source of light and a light path, comprising:
- positioning a plurality of slits in a first plane, said first plane proximate an image plane of said optical projection lithography system, wherein each individual slit of said plurality of slits has an equivalent width less than the wavelength of said light;
- moving said plurality of slits across and within said first plane, wherein said movement is in a direction perpendicular to the lengths of said plurality of slits;
- and
- detecting the intensity of said light transmitted through the plurality of slits as a function of position of said plurality of slits.
An aerial image analyzer for performing self metrology of an optical projection lithography system having a source of light and a light path, comprising:
- a translation stage;
- a slit plate mounted to said translation stage and positioned in a first plane, said first plane proximate an image plane of said optical projection lithography system, wherein said slit plate contains at least one slit with an equivalent slit width of less than the wavelength of said light;
- a scanning mechanism coupled to said translation stage, wherein said scanning mechanism translates said slit plate across and within said first plane, said translation direction perpendicular to the length of said slit;
- and
- means for detecting the intensity of light in the near field of said slit plate.
A method for optically analyzing the aerial image formed by an optical projection lithography system having a reticle, a source of light and a light path, comprising:
- replacing the reticle with a test pattern;
- positioning a slit in a first plane, said first plane proximate an aerial image plane of said optical lithography system, wherein said slit has an equivalent width less than the wavelength of said source of light;
- moving said slit across and within said first plane, wherein said movement is in a direction perpendicular to a long axis of said slit;
- and
- detecting the intensity of said light in a near field region of said slit as a function of slit position.
A method for optically analyzing the aerial image formed by an optical projection lithography system having a source of light and a light path, comprising:
- positioning a slit in a first plane, said first plane proximate an aerial image plane of said optical lithography system;
- moving said slit across and within said first plane, wherein said movement is in a direction perpendicular to a long axis of said slit;
- measuring the intensity of evanescent light transmitted by said slit as a function of slit position;
- and
- analyzing the intensity profile of said aerial image.
Dependencies are inferred from the claim text.