Quality estimation and improvement of imaging metrology targets

Methods are provided, which estimate a quality of a metrology target by calculating a noise metric of its ROI kernels, derived from application of a Fourier filter on the measured kernel with respect to a periodicity of the target's periodic structure(s); and using the calculated noise metric to indicate the target quality. An additional Fourier filter may be applied perpendicularly on the measured kernel with respect to a periodicity of a perpendicular segmentation of the periodic structure(s), and the (2D) noise metric may be derived by application of both Fourier filters. The estimated noise may be analyzed statistically to provide various types of information on the target. 本发明提供方法，所述方法通过以下操作估计计量目标的质量：计算从关于所述目标的周期性结构的周期性对经测量的核心应用傅里叶滤波器导出的其ROI核心的噪声度量；及使用所述计算得到的噪声度量指示所述目标质量。可关于所述周期性结构的垂直片段的周期性对所述经测量的核心垂直地应用额外傅里叶滤波器，且所述(2D)噪声度量可通过应用两个傅里叶滤波而导出。可在统计上分析所述经估计的噪声以提供关于所述目标的各种类型的信息。