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Generalized measurement configuration optimization for accurate reconstruction of periodic nanostructures using optical scatterometry

Optical scatterometry is a model based technique, which conventionally requires minimization of a predefined least square function. This minimization relies heavily on the measurement configuration: wavelength, incident angle, azimuthal angle, and sample position, which brings up the question of how to find the configuration that maximizes measurement accuracy. We propose a general measurement configuration optimization method based on error propagation theory and singular value decomposition, by which the measurement accuracy can be approximated as a function of a Jacobian matrix with respect to the measurement configurations. Simulation and experiments for a one-dimensional trapezoidal grating establishes the feasibility of the proposed method.