Method and apparatus for position-dependent optical metrology calibration

A method, comprising:

• moving a portion of an optical metrology apparatus over a plurality of positions relative to a test article holder, whereby a measurement location over the test article holder is changed;
• producing calibration signals over the plurality of positions with the optical metrology apparatus, the calibration signals containing information over a range of wavelengths;
• comparing the calibration signals to a model of signals produced by the metrology apparatus, the model including a set of position-dependant parameters characterizing the optical metrology apparatus;
• and
• determining values for the position-dependant parameters at a plurality of discreet wavelength values.

An apparatus, comprising:

• a chuck with a support structure upon which a test article rests during measurement of the test article;
• a metrology unit including movable optics, the metrology unit positioned relative to the chuck such that, over a range of travel, the movable optics have full optical access to a surface of the test article;
• and
• at least one calibration reference fixed to a chuck portion so as to be immovable relative to the support structure, and positioned such that the test article is interposed between a portion of the at least one calibration reference and the movable optics when the test article rests on the support structure.

A method, comprising:

• moving a portion of an optical metrology apparatus over a plurality of positions relative to a wafer chuck, whereby a measurement location over the wafer chuck is changed;
• producing calibration signals over the plurality of positions with the optical metrology apparatus and a calibration reference fixed to the wafer chuck, the calibration signals containing information over a range of wavelengths;
• placing a calibration wafer on the wafer chuck;
• producing calibration signals over the plurality of positions with the optical metrology apparatus and the calibration wafer, the calibration signals containing information over a range of wavelengths;
• comparing the calibration signals to a model of signals produced by the optical metrology apparatus, the model including a set of position-dependant parameters characterizing the optical metrology apparatus;
• and
• determining values for the position dependant parameters at a plurality of discreet wavelength values.

A computer readable storage medium storing instructions that, when executed by a computer processor, cause the computer to perform a method of calibration, the method comprising:

• moving a portion of an optical metrology apparatus over a plurality of positions relative to a test article holder, whereby a measurement location over the test article holder is changed;
• producing calibration signals over the plurality of positions with the optical metrology apparatus, the calibration signals containing information over a range of wavelengths;
• comparing the calibration signals to a model of signals produced by the metrology apparatus, the model including a set of position-dependant parameters characterizing the optical metrology apparatus;
• and
• determining values for position-dependant parameters at a plurality of discreet wavelength values.