Plasmonics-Based Alignment Ruler for 3D Circuit Technology

Metallic nanostructures can be engineered to manipulate light into a certain and unique fashion. One such example of these structures is the so-called plasmonic structures, which allows the coupling of an incident radiation with the surface electrons on the metal surface of the plasmonic nanostructure. This coupling has been utilized in a wide area of applications including structural coloring, which can be used in display, imaging, sensing and security applications. One such important area that can utilize these structures is the three-dimensional integrated circuit technology (3D ICs). 3D ICs technology is about the vertical stacking and integration of various technologies that can include electronics, biological systems, chemistry analysis, energy, etc. to form one complete autonomous system. Integrating these technologies altogether involve several steps, one of which is alignment to accuracies at the micro and nanoscale. Wafer-to-Wafer and Wafer-to-chip alignment is an inherited concept from the CMOS and MEMs technologies. However, using the plasmonic structures and their spectral responses to achieve the alignment in 3D IC technology is a very new concept. In this research, an optical technique for this alignment by incorporating nano-optical technology, known as ‘alignment ruler’, is proposed, implemented, and tested.