Lithographic apparatus and position sensor

A stage system, comprising:

• a support;
• a motor to drive the support, the motor comprising a stationary magnet assembly having a two dimensional arrangement of alternately polarized magnets to generate a spatially alternately polarized magnetic field;
• and
• a position sensor to measure a position of the support, the position sensor comprising a magnetic field sensor to measure a field strength of the magnetic field, and a sensor processing device to determine a position from the field strength as measured by the magnetic field sensor.

A lithographic apparatus comprising:

• an illumination system configured to condition a radiation beam;
• a patterning device support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam;
• a substrate support constructed to hold a substrate;
• a projection system configured to project the patterned radiation beam onto a target portion of the substrate;
• a motor comprising a stationary magnet assembly and a metallic layer to cover the magnet assembly, the motor configured to drive the patterning device support or the substrate support;
• and
• a position sensor to measure a position of the patterning device support or the substrate support in a direction substantially perpendicular to a plane formed by the metallic layer, the position sensor comprising an electromagnet, a drive circuit to drive the electromagnet to generate an alternating magnetic field, a measuring circuit to measure an electrical impedance parameter of the electromagnet and a sensor processing device to derive a position of the patterning device support or the substrate support from an effect on the electrical impedance parameter, the effect caused by eddy currents generated in the metallic layer by the alternating magnetic field.

A stage system, comprising:

• a support;
• a motor to drive the support, the motor comprising a stationary magnet assembly and a metallic layer to cover the magnet assembly;
• and
• a position sensor to measure a position of the support in a direction substantially perpendicular to a plane formed by the metallic layer, the position sensor comprising:
• an electromagnet,
• a drive circuit to drive the electromagnet to generate an alternating magnetic field,
• a measuring circuit to measure an electrical impedance parameter of the electromagnet, and
• a sensor processing device to derive a position of the support from an effect on the electrical impedance parameter, the effect caused by eddy currents generated in the metallic layer by the alternating magnetic field.

A lithographic apparatus comprising:

• an illumination system configured to condition a radiation beam;
• a patterning device support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam;
• a substrate support constructed to hold a substrate;
• a projection system configured to project the patterned radiation beam onto a target portion of the substrate,
• a motor comprising a stationary magnet assembly, the motor configured to drive the patterning device support or the substrate support;
• and
• a position sensor to measure a position of the patterning device support or the substrate support, the position sensor comprising:
• an emitter to emit a light plane, and
• a detector to detect a position of incidence of light from the light plane on the detector along a direction substantially perpendicular to the plane.