Lithographic apparatus, device manufacturing method, and device manufactured thereby
First Claim
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1. A lithographic projection apparatus comprising:
- a radiation system for supplying a projection beam of radiation;
a support structure for holding patterning structure, the patterning structure serving to pattern the projection beam according to a desired pattern;
a substrate table for holding a substrate;
a projection system for projecting the patterned beam onto a target portion of the substrate;
a level sensor for measuring at least one of a perpendicular position and tilt about at least one parallel axis of a surface of an object held by one of the support structure and the substrate table, and generating a position signal indicative thereof, perpendicular referring to a direction substantially perpendicular to the said surface and parallel referring to a direction substantially parallel to said surface;
a servo system responsive to said position signal for moving said object to a desired position; and
a filter connected between said level sensor and said servo system for filtering said position signal, the filter having a transfer function representative of a difference between an actual measurement of the level sensor and an ideal measurement of the level sensor.
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Abstract
On-the-Fly leveling in a lithographic apparatus is conducted using a setpoint derived by filtering the output of the combination of the output of a level sensor and another position sensor (LVDT or IFM). The level sensor may include look-ahead. The filter may be a low pass filter to cut-off level variations of wavelength shorter than the width of the slit during a scanning exposure. The filter may also be selected to reduce cross-talk between tilt movements and horizontal displacements.
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Citations
17 Claims
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1. A lithographic projection apparatus comprising:
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a radiation system for supplying a projection beam of radiation;
a support structure for holding patterning structure, the patterning structure serving to pattern the projection beam according to a desired pattern;
a substrate table for holding a substrate;
a projection system for projecting the patterned beam onto a target portion of the substrate;
a level sensor for measuring at least one of a perpendicular position and tilt about at least one parallel axis of a surface of an object held by one of the support structure and the substrate table, and generating a position signal indicative thereof, perpendicular referring to a direction substantially perpendicular to the said surface and parallel referring to a direction substantially parallel to said surface;
a servo system responsive to said position signal for moving said object to a desired position; and
a filter connected between said level sensor and said servo system for filtering said position signal, the filter having a transfer function representative of a difference between an actual measurement of the level sensor and an ideal measurement of the level sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of manufacturing a device comprising:
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providing a substrate that is at least partially covered by a layer of radiation-sensitive material;
providing a projection beam of radiation;
patterning the projection beam to produce a pattern in its cross-section;
measuring at least one of a perpendicular position and tilt about at least one parallel axis of a surface of an object with a level sensor and generating a position signal indicative thereof, perpendicular referring to a direction substantially perpendicular to the said surface and parallel referring to a direction substantially parallel to said surface;
projecting the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material while operating a servo system responsive to said position signal to maintain said object at said desired position; and
filtering said position signal to form a filtered position signal using a filter transfer function representative of a difference between an actual measurement of the level sensor and an ideal measurement of the level sensor before it is used by a servo system to control the position of the object. - View Dependent Claims (15)
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16. A lithographic projection apparatus comprising:
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a radiation system for supplying a projection beam of radiation;
a support structure for holding patterning structure, the patterning structure serving to pattern the projection beam according to a desired pattern;
a substrate table for holding a substrate;
a projection system for projecting the patterned beam onto a target portion of the substrate;
a level sensor for measuring at least one of a perpendicular position and tilt about at least one parallel axis of a surface of an object held by one of the support structure and the substrate table, and for generating a position signal as a function of time indicative thereof, perpendicular referring to a direction substantially perpendicular to the said surface and parallel referring to a direction substantially parallel to said surface;
a servo system responsive to said position signal for moving said object to a desired position; and
a filter for correcting the transfer function of the level sensor wherein the filter is, arranged for filtering said position signal in the time domain.
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17. A method of manufacturing a device comprising:
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providing a substrate that is at least partially covered by a layer of radiation-sensitive material;
providing a projection beam of radiation;
patterning the projection beam to produce a pattern in its cross-section;
measuring at least one of a perpendicular position and tilt about at least one parallel axis of a surface of an object with a level sensor and generating a position signal as a function of time indicative thereof, perpendicular referring to a direction substantially perpendicular to the said surface and parallel referring to a direction substantially parallel to said surface;
projecting the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material while operating a servo responsive to said position signal to maintain said object at said desired position; and
filtering said position signal in the time domain by using a filter transfer function for correcting the transfer function of the level sensor before it is used by said servo system to control the position of the object.
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Specification