Lithographic apparatus and an object positioning system

A lithographic apparatus comprising:

• a liquid supply system configured to supply a liquid to a space between a projection system and a substrate;
• an object table configured to carry an object, the object table comprising a channel for the passage therethrough of a two-phase flow comprising liquid from the space, wherein the two-phase flow through the channel causes a varying load to act on the object table causing deformation of a part of the object;
• a projection system configured to project a pattern on a patterning device onto the object using a projection beam, wherein placement of the projection beam on the object is movable in at least one direction relative to the object;
• and
• a control system to control the placement of the pattern relative to the object in the at least one direction based on a quantity representative of the deformation of the part of the object.

A lithographic apparatus comprising:

• a displacement measurement system comprising a target configured to receive a radiation beam and an optical displacement sensor configured to detect at least part of the radiation beam redirected by the target, wherein a varying load acts on the displacement sensor and/or the target, during operational use, causing deformation of a part of the displacement sensor and/or the target respectively;
• an object table which carries at least part of the displacement measurement system, the object table being movable in at least one direction;
• and
• a control system to control the movement of the object table in the at least one direction based on an output from the displacement measurement system and a quantity representative of the deformation of the part of the displacement sensor and/or the target respectively.

An object positioning system for a lithographic apparatus, the lithographic apparatus comprising a liquid supply system configured to supply a liquid to a space between a projection system and a substrate, wherein the object positioning system comprises:

• an object table configured to carry an object, the object table being movable in at least one direction, the object table comprising a channel for the passage therethrough of a two-phase flow comprising liquid from the space, wherein the two-phase flow through the channel causes a varying load to act on the object table causing deformation of a part of the object table and/or object:
• one or more sensors configured to measure a characteristic;
• one or more heaters configured to maintain a temperature of the object table;
• a predictor configured to determine a quantity representative of the deformation of the part, the quantity determined based on the measured characteristic and on a model or relationship representing at least the varying load;
• and
• a control system to control a heater of the one or more heaters based on an output from the one or more sensors.

An object positioning system for a lithographic apparatus, the object positioning system comprising:

• a measurement system comprising a target configured to receive a radiation beam and an optical sensor configured to detect at least some of the radiation beam redirected by the target, wherein a varying load acts on the optical sensor and/or the target, during operational use in the lithographic apparatus, causing deformation of a part of the optical sensor and/or the target respectively;
• an object table which carries at least a portion of the measurement system, the object table being movable in at least one direction;
• one or more sensors configured to measure a characteristic;
• one or more heaters configured to maintain a temperature of the object table;
• a predictor configured to determine a quantity representative of the deformation of the part, the quantity determined based on the measured characteristic and on a model or relationship representing at least the varying load:
• and
• a control system to control a heater of the one or more heaters based on an output from the one or more sensors and to control the movement of the object table in the at least one direction based on an output from the measurement system.