Displacement measurement systems lithographic apparatus and device manufacturing method

A displacement measurement system configured to measure a displacement between first and second components, the displacement measurement system comprising:

• first and second elongated diffraction gratings, wherein the first component is attached to the first elongated diffraction grating that is oriented such that its elongated direction is substantially parallel to a first direction, and the second component is attached to the second elongated diffraction grating that is oriented such that its elongated direction is substantially parallel to a second direction which is not parallel to the first direction, wherein the second elongated diffraction grating is configured to receive a diffracted radiation beam from the first elongated diffraction grating and reflect the diffracted radiation beam in a direction towards the first diffraction grating;
• one or more optical components configured to receive another diffracted radiation beam from the first elongated diffraction grating and re-direct the another diffracted radiation such that the another diffracted radiation is incident on the first elongated diffraction grating and is diffracted in turn by the first elongated diffraction grating, the second elongated diffraction grating and then the first elongated diffraction grating, and
• a sensor configured to detect a pattern of radiation generated by a diffraction of at least one beam of radiation by the first and second elongated diffraction gratings;
• wherein said pattern of radiation is indicative of the displacement of the first elongated diffraction grating relative to the second elongated diffraction grating in a third direction substantially perpendicular to both the first and the second direction.

A displacement measurement system configured to measure a movement of a first object relative to a second object, comprising:

• a first planar diffraction grating mounted to said first object;
• a second planar diffraction grating mounted to said second object and substantially parallel to the first planar diffracting grating;
• a source providing a first beam of radiation;
• wherein the first beam of radiation is incident on a first point on the first planar diffraction grating and diffracted such that first order and negative first order diffracted radiation is incident on the second planar diffraction grating;
• wherein the second planar diffraction grating is configured such that:
• at least a part of the first order radiation from the first planar diffraction grating is further diffracted by the second planar diffraction grating, is reflected from the second planar diffraction grating in a direction towards the first planar diffraction grating, and is incident on a second point on the first planar diffraction grating;
• at least a part of the negative first order radiation from the first planar diffraction grating is further diffracted by the second planar diffraction grating, is reflected from the second planar diffraction grating in a direction towards the first planar diffraction grating, and is incident on said second point on the first planar diffraction grating;
• and
• wherein both radiation derived from said first order diffracted radiation from the first planar diffraction grating and radiation derived from said negative first order diffracted radiation from the first planar diffraction grating are further diffracted by the first planar diffraction grating and propagate from said second point on said first planar diffraction grating in a common direction as a second beam of radiation;
• one or more optical components configured to re-direct the second beam of radiation such that the second beam of radiation is incident on the first planar diffraction grating and is diffracted in turn by the first planar diffraction grating, the second planar diffraction grating and then the first planar diffraction grating in a same manner as the first beam of radiation in order to generate a third beam of radiation;
• and
• a sensor configured to detect a pattern of radiation derived from the second point on said first planar diffraction grating, indicative of the relative movements of the first and second planar diffraction gratings in a direction parallel to the plane of the first and second planar diffraction gratings and perpendicular to the striations of the first and second planar diffraction gratings.

A lithographic apparatus, comprising:

• a radiation source configured to provide a beam of radiation;
• a support configured to support a patterning structure, the patterning structure configured to produce a desired pattern in the beam of radiation;
• a substrate table configured to hold a substrate;
• a projection system configured to project the patterned beam onto a target portion of the substrate;
• and
• a displacement measurement system configured to measure a displacement of a first component of the lithographic apparatus relative to a second component of the lithographic apparatus, the displacement measurement system comprising:
• first and second elongated diffraction gratings, wherein the first component is attached to the first elongated diffraction grating that is oriented such that its elongated direction is substantially parallel to a first direction, and the second component is attached to the second elongated diffraction grating that is oriented such that its elongated direction is substantially parallel to a second direction which is not parallel to the first direction, wherein the second diffraction grating is configured to receive a diffracted radiation beam from the first diffraction grating and reflect the diffracted radiation beam in a direction towards the first diffraction grating;
• one or more optical components configured to receive another diffracted radiation beam from the first elongated diffraction grating and re-direct the another diffracted radiation such that the another diffracted radiation is incident on the first elongated diffraction grating and is diffracted in turn by the first elongated diffraction grating, the second elongated diffraction grating and then the first elongated diffraction grating;
• and
• a sensor configured to detect a pattern of radiation generated by the diffraction of at least one beam of radiation by the first and second elongated diffraction gratings, wherein said pattern of radiation is indicative of the displacement of the first elongated diffraction grating relative to the second elongated diffraction grating in a third direction substantially perpendicular to both the first and the second direction.

A lithographic apparatus, comprising:

• a radiation source configured to provide a beam of radiation;
• a support configured to support a patterning structure, the patterning structure configured to produce a desired pattern in the beam of radiation;
• a substrate table configured to hold a substrate;
• a projection system configured to project the patterned beam onto a target portion of the substrate;
• and
• a displacement measurement system configured to measure a movement of a first object relative to a second object, the displacement measurement system comprising:
• a first planar diffraction grating mounted to said first object;
• a second planar diffraction grating mounted to said second object and substantially parallel to the first planar diffracting grating;
• a source providing a first beam of radiation;
• wherein the first beam of radiation is incident on a first point on the first planar diffraction grating and diffracted such that first order and negative first order diffracted radiation is incident on the second planar diffraction grating;
• wherein the second planar diffraction grating is configured such that:
• at least a part of the first order radiation from the first planar diffraction grating is further diffracted by the second planar diffraction grating, is reflected from the second planar diffraction grating in a direction towards the first planar diffraction grating, and is incident on a second point on the first planar diffraction grating;
• at least a part of the negative first order radiation from the first planar diffraction grating is further diffracted by the second planar diffraction grating, is reflected from the second planar diffraction grating in a direction towards the first planar diffraction grating, and is incident on said second point on the first planar diffraction grating;
• wherein both radiation derived from said first order diffracted radiation from the first planar diffraction grating and radiation derived from said negative first order diffracted radiation from the first planar diffraction grating are further diffracted by said first planar diffraction grating and propagate from said second point on said first planar diffraction grating in a common direction as a second beam of radiation;
• one or more optical components configured to re-direct the second beam of radiation such that the second beam of radiation is incident on the first planar diffraction grating and is diffracted in turn by the first planar diffraction grating, the second planar diffraction grating and then the first planar diffraction grating in a same manner as the first beam of radiation in order to generate a third beam of radiation;
• and
• a sensor configured to detect a pattern of radiation derived from the second point on said first planar diffraction grating, indicative of the relative movements of the first and second planar diffraction gratings in a direction parallel to the plane of the first and second planar diffraction gratings and perpendicular to the striations of the first and second planar diffraction gratings.

displacement measurement system comprising:

• first and second diffraction gratings, said displacement measurement system being configured to measure a displacement between said first and second diffraction gratings, wherein the measurement system is configured such that:
• a first beam of radiation input to the measurement system is divided into first and negative first order diffracted radiation beams by the first diffraction grating;
• said first and negative first order diffracted radiation beams are further diffracted by the second diffraction grating, reflected from the second diffraction grating in a direction towards the first diffraction grating, and subsequently recombined to form a second beam of radiation;
• a sensor configured to determine the relative displacement of said first and second gratings from a determination of a phase difference between a first component of said second beam, derived from said first order diffracted radiation beam, and a second component of said second beam, derived from said negative first order diffracted radiation beam;
• and
• at least one linear polarizer configured such that said first and second components of said second beam of radiation are linearly polarized and oriented in substantially mutually orthogonal directions,
• wherein the sensor is configured to detect a radiation derived from zero order radiation generated when the first beam is incident on the first diffraction grating and, based on said detected radiation, to determine the relative displacement of said first and second diffraction gratings in a direction substantially perpendicular to a plane of said first and second diffraction gratings by comparing a beam pathlength of the radiation derived from the zero order and radiation from at least one of the first and negative first orders.

displacement measurement system configured to measure a movement of a first object relative to a second object, comprising:

• a first planar diffraction grating mounted to said first object;
• a second planar diffraction grating mounted to said second object and substantially parallel to the first planar diffracting grating;
• a source providing a first beam of radiation;
• wherein the first beam of radiation is incident on a first point on the first diffraction grating and diffracted such that first order and negative first order diffracted radiation is incident on the second planar diffraction grating;
• wherein the second planar diffraction grating is configured such that:
• at least a part of the first order radiation from the first planar diffraction grating is further diffracted by the second planar diffraction grating, is reflected from the second planar diffraction grating in a direction towards the first planar diffraction grating, and is incident on a second point on the first planar diffraction grating;
• at least a part of the negative first order radiation from the first planar diffraction grating is further diffracted by the second planar diffraction grating, is reflected from the second planar diffraction grating in a direction towards the first planar diffraction grating, and is incident on said second point on the first planar diffraction grating;
• and
• wherein both radiation derived from said first order diffracted radiation from the first planar diffraction grating and radiation derived from said negative first order diffracted radiation from the first planar diffraction grating are further diffracted by said first planar diffraction grating and propagate from said second point on said first planar diffraction grating in a common direction as a second beam of radiation;
• and
• a sensor configured to detect a pattern of radiation derived from the second point on said first planar diffraction grating, indicative of the relative movements of the first and second planar diffraction gratings in a direction parallel to the plane of the first and second planar diffraction gratings and perpendicular to the striations of the first and second planar diffraction gratings,
• wherein the sensor is configured to detect a radiation derived from zero order radiation generated when the first beam is incident on the first planar diffraction grating and, based on said detected radiation, to determine the relative movement of the first and second planar diffraction gratings in a direction substantially perpendicular to the plane of the first and second planar diffraction gratings by comparing a beam pathlength of the radiation derived from the zero order and radiation from at least one of the first and negative first orders.

lithographic apparatus, comprising:

• a radiation source configured to provide a beam of radiation;
• a support configured to support a patterning structure, the patterning structure configured to produce a desired pattern in the beam of radiation;
• a substrate table configured to hold a substrate;
• a projection system configured to project the patterned beam onto a target portion of the substrate;
• and
• a displacement measurement system configured to measure a movement of a first object relative to a second object, the displacement measurement system comprising:
• a first planar diffraction grating mounted to said first object;
• a second planar diffraction grating mounted to said second object and substantially parallel to the first planar diffracting grating;
• and
• a source providing a first beam of radiation;
• wherein the first beam of radiation is incident on a first point on the first planar diffraction grating and diffracted such that first order and negative first order diffracted radiation is incident on the second planar diffraction grating;
• wherein the second planar diffraction grating is configured such that:
• at least a part of the first order radiation from the first planar diffraction grating is further diffracted by the second planar diffraction grating, is reflected from the second planar diffraction grating in a direction towards the first planar diffraction grating, and is incident on a second point on the first planar diffraction grating;
• at least a part of the negative first order radiation from the first planar diffraction grating is further diffracted by the second planar diffraction grating, is reflected from the second planar diffraction grating in a direction towards the first planar diffraction grating, and is incident on said second point on the first planar diffraction grating;
• and
• wherein both radiation derived from said first order diffracted radiation from the first planar diffraction grating and radiation derived from said negative first order diffracted radiation from the first planar diffraction grating are further diffracted by said first planar diffraction grating and propagate from said second point on said first planar diffraction grating in a common direction as a second beam of radiation;
• and
• a sensor configured to detect a pattern of radiation derived from the second point on said first planar diffraction grating, indicative of the relative movements of the first and second planar diffraction gratings in a direction parallel to the plane of the first and second planar diffraction gratings and perpendicular to the striations of the first and second planar diffraction gratings,
• wherein the sensor is configured to detect a radiation derived from zero order radiation generated when the first beam is incident on the first planar diffraction grating and, based on said detected radiation, to determine the relative movement of the first and second planar diffraction gratings in a direction substantially perpendicular to the plane of the first and second planar diffraction gratings by comparing a beam pathlength of the radiation derived from the zero order and radiation from at least one of the first and negative first orders.