Abstract: A lithographic apparatus includes a displacement measuring system to measure a position of a moveable object with respect to a reference frame of the lithographic apparatus, in at least three coplanar degrees of freedom (x, y, Rz) of an orthogonal x-y-z coordinate system centred in the center of the moveable object. The moveable object includes a support structure configured to support a patterning device or a substrate table configured to support a substrate. The displacement measuring system includes at least three sensor heads, each sensor head being positioned with a measuring direction substantially coplanar with the x-y plane of the coordinate system and each sensor head being furthermore positioned with the measuring direction substantially perpendicular to a connection line connecting the sensor head with the center of the movable object and extending coplanar with the x-y plane.

Abstract: A lithographic apparatus includes a position measurement system to determine along a measurement path a position of a first part of the lithographic apparatus with respect to a position of a second part of the lithographic apparatus. The position determination system comprises a plurality of temperature sensors to measure a temperature of a medium along the measurement path. The position measurement system corrects the determined position making use of the temperature as measured by the temperature sensors.

Abstract: A lithographic apparatus including a projection system configured to project a patterned radiation beam onto a target portion of a substrate includes a position measuring system configured to determine the position of a movable object in at least one direction. The measuring system includes at least a first sensor arranged spaced from one side of the object and at least a second sensor arranged spaced from an opposite side of the movable object, and a calculation device configured to calculate the position of the object on the basis of distances measured by the first sensor and the second sensor between the first and the object and the second sensor and the object, respectively. By using the (weighted) difference between measured signals for calculation of the position of the object, the errors in the sensor signals caused by disturbances, such as global and/or local changes of the refractive index and expansion can be substantially reduced.

Abstract: A position measurement system includes a first position measurement unit configured to measure a position of an object in a first and a second direction, the first position measurement unit including a first sensor and a first grating that extends in a first direction, a second position measurement unit configured to measure the position of the object in the first and the second direction, the second position measurement unit including a second sensor and a second grating that extends in the first direction. The position measurement system is configured to initialize the second position measurement unit based on a position measurement of the first position measurement unit.

Abstract: A position measurement system for measuring a position of an object is described, the system including: a first incremental measurement unit for measuring a first number of first distance steps in a distance between a reference frame and the object, wherein the first number equals a first integer value plus a first fraction, and a second incremental measurement unit for measuring a second number of second distance steps in a distance between the reference frame and the object, wherein the second number equals a second integer value plus a second fraction, wherein the position measurement system is constructed and arranged to initialize the second incremental measurement unit on the basis of the first number and the second fraction.

Abstract: A lithographic apparatus includes an object support configured to support an object. The apparatus further includes X, Y and Z interferometer measurement systems, and an object support positioning system configured to position the object support in a number of degrees of freedom on the basis of measurements of the interferometer measurement systems. A calibration device is configured to measure Ry of the object support with the X interferometer measurement system in at least two different Z positions, measure Ry of the object support with the Z interferometer measurement system in at least two different Z positions, calibrate a linear Z dependency of Ry on the basis of the measurements, and calibrating a linear X dependency of Z on the basis of the previous calibration. Similarly, a linear Y dependency of Z is calibrated.

Abstract: In a lithographic apparatus, a measurement of the position of an object in an ambient space by an object position measuring system which is influenced by pressure variations in the ambient space, is corrected by an accurate measurement of the pressure in the ambient space. A reference pressure volume may be provided, having a fluid connection with predetermined flow characteristics to the ambient space. A pressure difference is measured between a pressure in the reference pressure volume and an ambient pressure in the ambient space. The absolute pressure in the reference pressure volume is added to the pressure difference to determine a change of pressure in the ambient space. Alternatively, the pressure difference is integrated over time for determining a change of pressure in the reference pressure volume, and this change of pressure in the reference pressure volume is added to the pressure difference to determine a change of pressure in the ambient space.

Abstract: An improved lithographic interferometer system, is presented herein. The lithographic interferometer system comprises a beam generating mechanism, mirrors which reflect those beams, and detection devices for detecting an interference pattern of overlapping reflected beams. The beam generating mechanism comprises a beam-splitter, which splits the beams into reference beams and measuring beams, a reference mirror that provides a plane mirror interferometer, and a reflective surface that emits at least one reference beam used in a differential plane mirror interferometer.

Abstract: An improved lithographic interferometer system, is presented herein. The lithographic interferometer system comprises a beam generating mechanism, mirrors which reflect those beams, and detection devices for detecting an interference pattern of overlapping reflected beams. The beam generating mechanism comprises a beam-splitter, which splits the beams into reference beams and measuring beams, a reference mirror that provides a plane mirror interferometer, and a reflective surface that emits at least one reference beam used in a differential plane mirror interferometer.