Methods and systems for measurement of semiconductor structures with multi-pass statistical optimization

Abstract

Methods and systems for measuring physical properties of a specimen by iterative solution of an optimization function including both current and prior measurement information are described herein. In one aspect, a Maximum A Posteriori (MAP) estimation approach is employed to integrate prior measurement information with current measurement information in the optimization function. In some examples, prior measurement information associated with the measurement of a semiconductor structure is available from a number of exogenous sources. In a further aspect, prior measurement information includes current measurements of a semiconductor structure under measurement as part of a multiple pass measurement. Prior statistics are determined based on an initial set of values of parameters of interest. The prior statistics are included in a subsequent MAP analysis of the same measurement data set employed in a first measurement pass. In another aspect, prior statistics are tracked to determine their impact on current measurements.