Membrane technology for the fabrication of three-dimensional photonic crystals

Abstract

Three-dimensional photonic crystals hold tremendous promise toward the realization of truly integrated photonic circuits on a single substrate. Nanofabrication techniques currently limit the ability to create the multilayer structure of dielectric materials. Past investigators have approached the problem using the layer-by-layer fabrication method; this method leverages the planar processes that have been developed by the semiconductor industry. Ultimately, the result from this path offered a small area with low yield and exorbitant costs in terms of time and resources. We introduce large-area membrane stacking as a new approach for three-dimensional nanofabrication. Silicon-nitride membranes are pre-patterned with the two-dimensional photonic crystals. The membranes can then assembled in a serial manner on a substrate to generate the three-dimensional photonic crystal. The efficacy of this method is founded upon the ability to inspect membranes before assembly; it also requires a large yield for stacking. This thesis is concerned with addressing the key challenges of the membranes-tacking- nanofabrication architecture. We develop a process for generating large-area- silicon-nitride membranes and investigate emerging lithography techniques for patterning them: nano-imprint lithography and coherent diffraction lithography. We demonstrate the ability to reliably bond these membranes to a new substrate. Finally, we address the novel problem of releasing the membrane from its frame. This is accomplished by designing stress-engineered cleavage points that detach the membrane while leaving behind defined edges and a particle-free surface. We will show the stacking of two large-area membranes on a patterned substrate for a total of three functional layers.