Abstract: An inspection system includes a controller including a memory maintaining program instructions and one or more processors configured to execute the program instructions. The program instructions cause the one or more processors to generate a geometric model of a structure of a sample, generate an optical response function model of the structure of the sample to illumination based at least in part on the geometric model, receive measured data from a detector, generate a parametric sub-structure model based on at least the optical response function model and the measured data, and extract one or more parameters of the structure based on the measured data.

Abstract: Methods and systems for selecting measurement locations on a wafer for subsequent detailed measurements employed to characterize the entire wafer are described herein. High throughput measurements are performed at a relatively large number of measurement sites on a wafer. The measurement signals are transformed to a new mathematical basis and reduced to a significantly smaller dimension in the new basis. A set of representative measurement sites is selected based on analyzing variation of the high throughput measurement signals. In some embodiments, the spectra are subdivided into a set of different groups. The spectra are grouped together to minimize variance within each group. Furthermore, a die location is selected that is representative of the variance exhibited by the die in each group. A spectrum of a measurement site and corresponding wafer location is selected to correspond most closely to the center point of each cluster.

Abstract: Methods and systems for calibrating simulated measurement signals generated by a parametric measurement model are described herein. Regression on real measurement signals is performed using a parametric model. The residual fitting error between the real measurement signals and simulated measurement signals generated by the parametric model characterizes the error of the parametric model at each set of estimated values of the one or more floating parameters. Simulated measurement signals are generated by the parametric model at specified values of the floating parameters. A residual fitting error associated with the simulated measurement signals generated at the specified values of the floating parameters is derived from the residual fitting errors calculated by the regression on the real measurement signals. The simulated measurement signals are calibrated by adding the residual fitting error to the uncalibrated, simulated measurement signals.

Abstract: Methods and systems for selecting measurement locations on a wafer for subsequent detailed measurements employed to characterize the entire wafer are described herein. High throughput measurements are performed at a relatively large number of measurement sites on a wafer. The measurement signals are transformed to a new mathematical basis and reduced to a significantly smaller dimension in the new basis. A set of representative measurement sites is selected based on analyzing variation of the high throughput measurement signals. In some embodiments, the spectra are subdivided into a set of different groups. The spectra are grouped together to minimize variance within each group. Furthermore, a die location is selected that is representative of the variance exhibited by the die in each group. A spectrum of a measurement site and corresponding wafer location is selected to correspond most closely to the center point of each cluster.