Interferometric position-measuring devices and methods

A microlithography system, comprising:

• an optical system;
• a stage that is movable in at least a first movement direction relative to the optical system;
• a stage-position-measurement interferometer system situated relative to the stage, the stage-position-measurement interferometer system producing at least one respective reference beam and at least one respective measurement beam, at least the measurement beam being directed in the first movement direction for reflection from a surface moving with the stage, the stage-position-measurement interferometer system producing, from interference of its reference and measurement beams, stage-position data concerning stage position in the first movement direction;
• a first reference interferometer system situated relative to the optical system, the first reference interferometer system producing at least one respective reference beam and at least one respective measurement beam, at least the measurement beam being directed in the first movement direction for reflection from a surface associated with the optical system, the first reference interferometer system producing, from interference of its reference and measurement beams, first reference data for the stage-position data;
• a second reference interferometer system situated relative to the optical system, the second reference interferometer system producing at least one respective measurement beam that is directed in the first movement direction for reflection from a surface associated with the optical system, the second reference interferometer system producing, from interference of its at least one measurement beam with a reference beam, second reference data for the stage-position data;
• and
• a processor connected to receive the stage-position data, the first reference data, and the second reference data from the interferometer systems, the processor being configured to determine a position of the stage, in the first movement direction, relative to the optical system and to correct the determined position for displacement of the optical system.

A microlithography system, comprising:

• a first stage;
• a lithography optical system situated relative to the first stage, wherein the first stage is movable relative to the optical system;
• a first stage-position interferometer system situated relative to the first stage and comprising at least one respective reference beam and at least one respective measurement beam, the at least one respective measurement beam reflecting from a surface movable with the stage;
• an optical-system position-measurement device situated relative to the optical system;
• a processor coupled to receive respective data from the first stage-position interferometer system and from the optical-system position-measurement device, and to use data from the optical-system position-measurement device to determine corrections based on optical-system movements and to apply the corrections to data from the first stage-position interferometer system to correct a position-measurement signal produced by the first stage-position interferometer system.

In a process system, a method for determining position of a stage that is movable in at least one movement direction relative to a process tool situated at a process position, the method comprising:

• interferometrically determining a position of the stage in the movement direction relative to the process position;
• determining displacement of the process tool from the process position;
• and
• determining a position of the stage, relative to the process tool, corrected for the displacement of the process tool.

In a lithography system, a method for determining position of a first stage that is movable in at least one movement direction relative to a reference position of an optical system of the lithography system, the method comprising:

• directing at least one position-measurement beam and at least one reference beam of a stage-position-measurement interferometer to the first stage to determine a position of the first stage in the movement direction relative to the reference position;
• directing at least one beam of an optical-system reference interferometer along a pathway to and from the optical system;
• producing, from the optical-system reference interferometer, an interferometer signal including data on air fluctuation occurring in the pathway;
• based on the interferometer signal, determining an air-fluctuation correction;
• and
• applying the air-fluctuation correction to the determined position of the first stage to determine a corrected position of the first stage relative to the reference position.

In a method for performing microlithography of a substrate with a reticle pattern as projected by an optical system, a method for correcting a synchronization error of movement of a reticle stage and of movement of a substrate stage relative to each other, comprising:

• providing each of the reticle stage and substrate stage with respective interferometer systems each comprising respective reference and measurement interferometers;
• determining a difference (Wm−Wr) from data from the substrate-stage measurement interferometer (Wm) and at least one substrate-stage reference interferometer (Wr), the difference (Wm−Wr) comprising data, obtained during actual movements of the substrate stage relative to the optical system, that are independent of movements of the optical system;
• determining a difference (Rm−Rr) from data from a reticle-stage measurement interferometer (Rm) and at least one reticle-stage reference interferometer (Rr);
• determining, from data from the substrate-stage interferometer system, an air fluctuation error, the air fluctuation error comprising fluctuations in Wm predicted from corresponding measured fluctuations in the beam of the substrate-stage reference interferometer Wr;
• inputting (Wm−Wr) and the air fluctuation error to a filter operating according to an algorithm to determine a true substrate-stage position (Wm−Wr)′ that takes into account fluctuations in the interferometer beam paths and movements of the optical system;
• comparing (Wm−Wr)′ to (Rm−Rr) to yield a synchronization error representing a positional discrepancy in the positions of the stages;
• and
• adjusting position of the reticle stage based on the synchronization error

In a method for performing microlithography of a substrate with a reticle pattern as projected by an optical system, a method for correcting a synchronization error of movement of a reticle stage and of movement of a substrate stage relative to each other, comprising:

• providing each of the reticle stage and substrate stage with respective interferometer systems each comprising respective reference and measurement interferometers;
• determining a difference (Wm−Wr) from data from the substrate-stage measurement interferometer (Wm) and at least one substrate-stage reference interferometer (Wr), the difference (Wm−Wr) constituting data, obtained during actual movements of the substrate stage relative to the optical system, that are independent of movements of the optical system;
• determining a difference (Rm−Rr) from data from a reticle-stage measurement interferometer (Rm) and at least one reticle-stage reference interferometer (Rr);
• determining, from data from the substrate-stage interferometer system, an air fluctuation error, the air fluctuation error comprising fluctuations in Wm predicted from corresponding measured fluctuations in the beam of the substrate-stage reference interferometer Wr;
• producing an uncompensated synchronization error from the differences (Wm−Wr) and (Rm−Rr);
• inputting the air fluctuation error and the uncompensated synchronization error into a filter that produces, from these inputs, a compensated synchronization error that takes into account air fluctuation and movement of the optical system;
• and
• adjusting position of the reticle stage based on the compensated synchronization error.