Single-pass and multi-pass interferometery systems having a dynamic beam-steering assembly for measuring distance, angle, and dispersion

An interferometry system comprising:

• an interferometer which during operation directs a measurement beam along a measurement path contacting a measurement object and combines at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams, the interferometer comprising a beam steering assembly having a beam steering element and a positioning system to orient the beam steering element the beam steering element positioned to direct the measurement beam, the measurement beam contacting the beam steering element;
• a control circuit which during operation causes the positioning system to reorient the beam steering element in response to a change in angular orientation of the measurement object;
• and
• a signal processor,
• wherein during operation the interferometer directs a second measurement beam along a second measurement path contacting the measurement object and combines at least a portion of the second measurement beam with an additional beam to form a second overlapping pair of exit beams,
• the measurement beams contacting the measurement object at separate locations, and
• wherein during operation the signal processor determines the change in angular orientation of the measurement object based on signals derived from the overlapping pairs of exit beams.

An interferometry system comprising:

• an interferometer which during operation directs a measurement beam along a measurement path contacting a measurement object and combines at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams, the interferometer comprising a beam steering assembly having a beam steering element and a positioning system to orient the beam steering element the beam steering element positioned to direct the measurement beam, the measurement beam contacting the beam steering element;
• a control circuit which during operation causes the positioning system to reorient the beam steering element in response to a change in at least one of angular orientation and position of the measurement object;
• and
• a signal processor,
• wherein the measurement beam includes components at two wavelengths, and during operation the interferometer produces the first mentioned overlapping pair of exit beams and a second overlapping pair of exit beams, the first pair of exit beams indicative of changes in optical path length to the measurement object at a first of the two wavelengths and the second pair of exit beams indicative of changes in optical path length to the measurement object at a second of the two wavelengths,
• wherein during operation the signal processor processes signals derived from the overlapping pairs of exit beams.

An interferometry system comprising:

• an interferometer which during operation directs a measurement beam along a measurement path contacting a measurement object and combines at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams, the interferometer comprising a beam steering assembly having a beam steering element and a positioning system to orient the beam steering element the beam steering element positioned to direct the measurement beam, the measurement beam contacting the beam steering element;
• a control circuit which during operation causes the positioning system to reorient the beam steering element in response to a change in at least one of angular orientation and position of the measurement object;
• and
• a signal processor,
• wherein the measurement beam, the other beam, and the overlapping pair of exit beams each include components at the two wavelengths, the overlapping exit beams indicative of changes in optical path length to the measurement object at each of the two wavelengths, and
• wherein the signal processor processes signals derived from the overlapping pair of exit beams.

An interferometry method comprising:

• directing a measurement beam along a measurement path contacting a measurement object;
• combining at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams;
• and
• using an electronic control system to redirect the measurement beam in response to a change in angular orientation of the measurement object.

An interferometry method comprising:

• directing a measurement beam along a measurement path contacting a measurement object;
• combining at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams,
• using an electronic control system to redirect the measurement beam in response to a change in at least one of the angular orientation and position of the measurement object;
• directing a second measurement beam along a second measurement path contacting the measurement object;
• combining at least a portion of the second measurement beam with an additional beam to form a second overlapping pair of exit beams, the first and second pairs of exit beams indicative of changes in optical path length to two separate locations on the measurement object;
• and
• calculating the change in angular orientation of the measurement object based on signals derived from the overlapping pairs of exit beams.

An interferometry method comprising:

• directing a measurement beam having components at two wavelengths along a measurement path contacting a measurement object;
• calculating changes in geometric distance to the measurement object based on interferometric signals derived from the measurement beam;
• and
• using an electronic control system to redirect the measurement beam in response to a change in at least one of the angular orientation and position of the measurement object.

An interferometry method comprising:

• directing a measurement beam having components at two wavelengths along a measurement path contacting a measurement object;
• calculating dispersion along the measurement path based on interferometric signals derived from the measurement beam;
• and
• using an electronic control system to redirect the measurement beam in response to a change in at least one of the angular orientation and position of the measurement object.

An interferometry system comprising:

• an interferometer which during operation directs a measurement beam along a measurement path contacting a measurement object and combines at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams, the interferometer comprising a beam steering assembly having a beam steering element and a positioning system to orient the beam steering element, the beam steering element having opposite sides and a mirror on each of the opposite sides, the beam steering element positioned to receive and redirect the measurement beam;
• and
• a control circuit which during operation causes the positioning system to reorient the beam steering element in response to a change in at least one of angular orientation and position of the measurement object,
• wherein during operation the interferometer directs the measurement beam to contact one of the sides of the beam steering element before contacting the measurement object and the other of the sides after contacting the measurement object.

An interferometry system comprising:

• an interferometer which during operation directs a measurement beam along a measurement path contacting a measurement object and combines at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams, the interferometer comprising a beam steering assembly having a beam steering element and a positioning system to orient the beam steering element, the beam steering element having opposite sides and a mirror on each of the opposite sides, the beam steering element positioned to receive and redirect the measurement beam;
• and
• a control circuit which during operation causes the positioning system to reorient the beam steering element in response to a change in at least one of angular orientation and position of the measurement object,
• wherein during operation the interferometer directs the measurement beam to contact one of the sides of the beam steering before contacting the measurement object and directs the at least a portion of the measurement beam to contact the other of the sides of the beam steering element.

A lithography method comprising:

• positioning a first component of a lithography system relative to a second component of a lithography system to expose a wafer to spatially patterned radiation;
• and
• measuring the position of the first component relative to the second component using an interferometry method wherein the first component includes the measurement object,
• and wherein the interferometry method comprises (i) directing a measurement beam along a measurement path contacting a retroreflector on a measurement object, (ii) combining at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams, and (iii) using an electronic control system to redirect the measurement beam in response to a change in position of the measurement object that causes a transverse displacement between the overlapping pair of exit beams.

A beam writing method for use in fabricating a lithography mask, the method comprising:

• directing a write beam to a substrate to pattern the susbtrate;
• positioning the substrate relative to the write beam;
• and
• measuring the position of the substrate relative to the write beam using an interferometry method comprising (i) directing a measurement beam along a measurement path contacting a retroreflector on a measurement object, (ii) combining at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams, and (iii) using an electronic control system to redirect the measurement beam in response to a change in position of the measurement object that causes a transverse displacement between the overlapping pair of exit beams.