Interferometer system for a semiconductor exposure system
AssigneeNikon Corporation
InventorsW. Thomas Novak, David Stumbo, Fuyuhiko Inoue
Life of this patent
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Abstract
An interferometer measuring system comprising two moveable members and a reference member that may have significantly less movement, the group having a number of attached measurement mirrors, interferometers for measuring position and two optical support blocks for the interferometers. The interferometers are used to determine the measured optical path lengths to each of the moveable members and reference member and these positions are used to calculate the misalignment, or error in the relative positions of the moveable members with respect to the reference member. This calculated error is then used to correct the misalignment by moving the appropriate members in the manner directed by the calculation.
Claims43
A method employing an interferometer system to determine the relative position, within a given plane, of a plurality of moveable members, wherein said interferometer system comprises at least one component supporting a plurality of interferometer measurement beams and at least two moveable members, at least one of which is a reference moveable member, the method comprising:
- directing from each said at least one interferometer component at least two interferometer measurement beams toward said reference moveable member;
- directing at least two interferometer measurement beams from the at least one interferometer component toward each of said at least two moveable members that are not said reference moveable member;
- measuring an optical path length change of said at least four interferometer beams as a result of relative movement of said at least one interferometer component and said moveable members;
- and
- determining the relative positions of said moveable members based on said measured optical path length changes.
A method employing an interferometer system to determine the relative positions, within a given plane, of a plurality of movable members, wherein said interferometer system comprises at least one component supporting a plurality of interferometer measurement beams directed toward at least two moveable members, the method comprising:
- measuring optical path length change between the at least one interferometer component and said at least two moveable members along each of the plurality of interferometer beams;
- calculating a nominal relative position based on a first selected set of measured optical path length changes;
- calculating a correction to account for movement of the at least one interferometer system component based on a second selected set of measured optical path length changes;
- and
- determining relative positions between the moveable members based on the nominal relative positions and said correction.
A method employing an interferometer system to determine the relative positions of a plurality of movable members with respect to a moveable reference member within a given plane, wherein said interferometer system includes at least two interferometer blocks, each block supporting a plurality of interferometer measurement beams directed at least at the reference moveable member and one other moveable member, the method comprising:
- sensing, with interferometers of a first interferometer block, the measured optical path lengths to at least two points on each of a first plurality of moveable members, said first plurality of moveable members including a first moveable member and a reference member;
- sensing, with interferometers of a second interferometer block, the measured optical path lengths to at least two points on each of a second plurality of moveable members, said second plurality of moveable members including a second moveable member and said reference member;
- calculating the positions of said first and second moveable members relative to the reference member based on (i) the measured optical path lengths between the first moveable member and the first interferometer block, (ii) the measured optical path lengths between the second moveable member and the second interferometer block and (iii) the measured optical path lengths between said first and second interferometer blocks and said reference member.
A method for controlling stage position relative to a projection lens assembly in a lithography exposure system, comprising:
- positioning a stage with respect to a projection lens assembly;
- providing an interferometer system comprising at least one interferometer component supporting a plurality of interferometer measurement beams directed at said projection lens assembly and stage, wherein said interferometer measurement beams are disposed in two adjacent pairs, one pair directed at each of the projection lens assembly and stage, the beams in each pair being spaced apart by a determined spacing distance and wherein adjacent beams of the adjacent pair are spaced apart by a determined adjacent distance;
- measuring optical path length change between the at least one interferometer component and the projection lens assembly and between the at least one interferometer component and the stage along each of the plurality of interferometer beams;
- calculating a nominal relative position of the stage with respect to the projection lens assembly based on a first selected set of measured optical path length changes;
- calculating a correction to account for movement of the at least one interferometer system component based on a second selected set of measured optical path length changes;
- determining relative positions between the stage and the projection lens assembly based on the nominal relative positions and said correction;
- and
- controlling the position of the stage with respect to the projection lens assembly in accordance with said determined relative positions.
A system for relative positioning of moveable members in a reference plane, comprising:
- a first moveable member having a first measurement mirror attached thereto;
- a second moveable member having a second measurement mirror attached thereto;
- a third moveable member having at least a third measurement mirror attached thereto;
- a plurality of interferometers including a plurality of reference mirrors and providing a plurality of measurement beams and a plurality of reference beams to measure optical path length changes;
- a first optical support block supporting a plurality of said interferometers wherein at least two of said interferometer measurement beams are directed to points on said first measurement mirror and at least two interferometer measurement beams are directed to points on said third measurement mirror and wherein each of said measurement beams is paired with one of said reference beams to provide a signal representing the path length to said measurement mirror;
- a second optical support block supporting a plurality of said interferometers wherein at least two of said interferometer measurement beams are directed to points on said second measurement mirror and at least two interferometer measurement beams are directed to points on said third measurement mirror and wherein each of said measurement beams is paired with one of said reference beams to provide a signal representing the path length to said measurement mirror;
- a plurality of sensors for receiving each of said signals;
- and
- at least one controller cooperating with at least each of the first and second moveable members to position at least one of said members with respect to the third moveable member in response to the sensed signals.
A method for controlling stage position relative to a projection lens assembly in a lithography exposure system, comprising:
- positioning a plurality of moveable members with respect to one another, said moveable members comprising a stage and a projection lens assembly;
- providing an interferometer system comprising an interferometer block supporting a first plurality of interferometer measurement beams directed at said projection lens assembly and a second plurality of interferometer measurement beams directed at said stage;
- measuring optical path length change between said interferometer block and said projection lens assembly and between said interferometer block and said stage along each of said plurality of interferometer beams;
- calculating a correction to account for movement of said interferometer system block based on a selected set of measured optical path length changes;
- determining relative positions between said projection lens assembly and said stage based on said correction;
- and
- controlling relative positions between said projection lens assembly and said stage based on said determined relative positions.
An apparatus, comprising
- a projection system configured to project along a projection axis;
- a stage;
- an interferometer system configured to generate:
- a first set of beams between the interferometer system and the projection system, the first set of beams being configured to detect movement of the projection system in all degrees of freedom except along the projection axis;
- and
- a second set of beams between the interferometer system and the stage, the second set of beams being configured to detect movement of the stage in all degrees of freedom except along the projection axis;
- and
- a control system, coupled to the interferometer system, and configured to maintain the projection system and stage in relative alignment in all degrees of freedom except along the projection axis.
Dependencies are inferred from the claim text.