Moiré method for nanoprecision wafer-to-wafer alignment: Theory, simulation and application

The two dimensional (2D) moireacute centrosymmetric grating is developed to assist realization of high-precision wafer-to-wafer alignment and non-destructive measurement of misalignments for wafer bonding. Using these moireacute patterns the misalignments in the order of plusmn 64 nm in X-Y axis can be resolved by a simple IR microscopy (5times objective) images. This value can be further improved to sub-10 nm range if the sub-pixel estimation is performed. For current status, the limit of the minimum resolved misalignment using moireacute gratings is ~0.2 nm according to theoretical analysis. It can be applied for not only the future 3D integration of wafer-scale, but also the fabrication of 3D nanostructures and advanced lithography techniques.