The present disclosure addresses various problems discussed above. In a first aspect, the present disclosure provides an improved measurement method of determining the position of the metrology mark on a substrate in the lithography process. In another aspect overlay control and process robustness can be improved. The present disclosure sets forth a number of improvements in the design of the metrology mark on a substrate in a lithography process. The present disclosure also addresses the accuracy of the determination of the position of the metrology mark on the substrate caused by the stack of layers on the layer containing the metrology mark (e.g., caused by the change of the angular reflectance and the change in a wavelength of the reflected beam, etc.) mentioned above, among others. The present disclosure also sets forth a method of reducing measurement sensitivity to a linear apodization effect of non-zeroth diffraction orders of the reflected beams caused by the stack of layers on the layer containing the metrology mark by using the sub-segmented grating structure. The present disclosure also sets forth a method of creating or modifying a metrology mark in a matter that avoids some of the process variations introduced by the stack of layers on top of the mark.
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