Balancing planarization of layers and the effect of underlying structure on the metrology signal

摘要

One embodiment of the present invention is a method of designing underlying structures in a wafer with pads of varying sizes and varying loading factors, and selecting the design of pads that yield a reflected metrology signal closest to the calibration metrology signal and that meet preset standard planarization characteristics. Another embodiment is a method of designing underlying structures with random shapes of varying sizes and varying loading factors. Still another embodiment is the use of periodic structures of varying line-to-space ratios in one or more underlying layers of a wafer, the periodicity of the underlying periodic structure being positioned at an angle relative to the direction of periodicity of the target periodic structure of the wafer.