Method and apparatus for position measurement of a pattern formed by a lithographic exposure tool

Abstract

Variation in position of test marks formed of overlapping exposed features imaged by an imaging structure such as that of a lithography tool are characterized at high speed and with extremely high accuracy by imaging test marks formed in resist or on a target or wafer by a lithographic process, collecting irradiance distribution data and fitting a mathematical function to respective portions or regions of output data corresponding to a test mark of a test mark pattern such as respective maxima or minima regions or other regions of the irradiance distribution data to determine actual location and shift of position of respective patterns of test marks. Metrology fields are formed of patterns of test marks on test wafers or production wafers preferably including a critical dimension exposed at different focus distances and/or illumination conditions to capture position/aberration data for the imaging structure. The imaging structure can then be adjusted or corrected to minimize or eliminate aberrations of performance of the imaging structure or the performance on a complete lithographic process and/or to achieve overlay positioning with high accuracy and minimal requirements for wafer space.

Dependencies are inferred from the claim text.