Methode zur Erfassung periodischer sub-wellenlängen Nanostrukturen für den In-Prozess-Einsatz

Scatterometry has the potential to evaluate periodical nanostructures, like e.g. gratings, during the manufacturing process. But, the method does not measure topography data sets. Instead, it determines surface property parameters, like e.g. the width of a nanostructure, and this can only be achieved, if the relationship between scattered light distribution and surface property is known. This paper presents a scatterometry-based approach for an in-process determination of the local heights of a sinusoidal grating imprinted in a foil. Initially, the relationship between the grating height and the resulting light distribution was not known. Hence, the scattering process has to be simulated for different surfaces andmeasuring parameters with a numerical model. The simulation results were used to derive a measurement method and a setup, which enabled to achieve biunique measurements of grating heights up to 500 nm. Additionally, the uncertainty of the approach was investigated based on the simulation results for different measurement and simulation parameters, like e.g. angle of incidence and laser wavelength. The determined measurement uncertainty of the grating height is recently limited by unknown systematic measurement deviations and is below a value of 8 nm, if laser light in the visible wavelength range is used. An experimental evaluation of the measurement approach with a laboratory setup proofed its sensitivity for the identification of local grating height deviations. If a suitable detection system is used for the scattered light distribution, measurement rates up to the MHz-range can be achieved, which shows that the approach is appropriate for an in-process application.