100-nm-Scale Alignment using Laser Beam Diffraction Pattern Observation Techniques and Wafer Fusion for Realizing Three-Dimensional Photonic Crystal Structure

We previously proposed a new method for realizing three-dimensional photonic crystals in the optical wavelength region, where two-dimensional basic structures are aligned using a laser beam diffraction pattern observation technique and stacked by means of a wafer fusion. In this method, it is essential to align the two-dimensional basic structures with an accuracy of optical wavelength order at wafer fusion. In this work, we develop an alignment system based on a laser beam diffraction pattern observation technique and achieve alignment and wafer fusion with accuracy of less than 100 nm, for the first time.