| Popis: |
This work extends an extreme variant of superconformal Au electrodeposition to deeper device architectures while exploring factors that constrain its function and the robustness of void-free processing. The unconventional bottom-up process is used to fill diffraction gratings with trenches 94 μm deep and 305 μm deep, with aspect ratios (height/width) of just below 20 and 15, respectively, in near-neutral 0.16 mol∙l−1 Na3Au(SO3)2 + 0.64 mol∙l−1 Na2SO3 electrolyte containing 50 μmol∙l−1 Bi3+. Although the aspect ratios are modest compared to previously demonstrated void-free filling beyond AR = 60, the deepest trenches filled exceed those in previous work by 100 μm—a nearly 50% increase in depth. Processes that substantially accelerate the start of bottom-up deposition demonstrate a linkage between transport and void-free filling. Final profiles are highly uniform across 65 mm square gratings because of self-passivation inherent in the process. Electron microscopy and electron backscatter diffraction confirm the fully dense Au and void-free filling suggested by the electrochemical measurements. X-ray transmission “fringe visibility” averages more than 80% at 50 kV X-ray tube voltage across the deeper gratings and 70% at 40 kV across the shallower gratings, also consistent with uniformly dense, void-free fill across the gratings. |
