Method for calibrating a lithographic projection apparatus and apparatus capable of applying such a method

Claim 3

A method according to claim 1 , wherein said set of reference positions are identified by detecting at least two marks provided to said object table.

Claim 4

A method according to claim 1 , wherein said set of reference positions are identified by detecting at least two marks on a workpiece held by said object table.

Claim 5

A method according to claim 2 , wherein said mark is a diffractive mark whose position is detected by directing a detection beam of radiation to said diffractive mark and measuring the intensity of sub-beams diffracted from said mark with an intensity detector such that the intensity detected by the intensity detector comprises an indication of the position of the mark with respect to that detector.

Claim 6

A method according to claim 1 , wherein said set of reference positions are identified by detecting an aerial image of a mark by at least two image sensors provided to said object table and adapted to detect an aerial image of a mark.

Claim 7

A method according to claim 5 , wherein said aerial image generated with a mark with a particular pattern is scanned over an image sensor comprising a similar pattern located on top of a light intensity detector such that the intensity detected by the intensity detector comprises an indication of the position of the aerial image with respect to said image sensor.

Claim 8

A method according to claim 1 , wherein at least one of said first position measuring system and said second position measuring system comprises an interferometer system.

Claim 9

A method according to claim 1 , wherein said calibration method is applied for every substrate processed in the lithographic projection apparatus.

Claim 10

A method according to claim 1 , wherein said lithographic projection apparatus includes a radiation system comprising a radiation source.

Claim 11

A lithographic projection apparatus comprising: an illumination system to supply a projection beam of radiation; a first object table to support patterning structure, the patterning structure constructed and arranged to pattern the projection beam according to a desired pattern; a second object table to hold a substrate; and a projection system to project the patterned beam onto a target portion of the substrate; a first position measuring system to measure a position of one of said first and second object table; a first detection system to identity a reference position of said one object table within a range of said first position measuring system; a second position measuring system to measure a position of said one object table; a second detection system to identity a reference position of said one object table within the range of said second position measuring system; and a processor in communication with said first and said second position measuring system and said first and said second detection system, the processor being configured and arranged to calculate corrected measurements for said first and said second position measuring system.

Claim 12

A lithographic projection apparatus comprising: an illumination system to supply a projection beam of radiation; a first object table to support patterning structure, the patterning structure constructed and arranged to pattern the projection beam according to a desired pattern; a second object table to hold a substrate; and a projection system to project the patterned beam onto a target portion of the substrate; a first position measuring system to measure a position of one of said first and second object table; a first detection system to identity a reference position of said one object table within a range of said first position measuring system; a second position measuring system to measure a position of said one object table; a second detection system to identity a reference position of said one object table within the range of said second position measuring system; and a processor in communication with said first and said second position measuring system and said first and said second detection system, the processor being configured and arranged to calculate corrected measurements for said first and said second position measuring system.