Optimization of Cryogenic Deep Reactive Ion Etching Process for On-Chip Energy Storage

In this paper we optimize cryogenic deep reactive ion etching processes to achieve the best aspect ratios of holes in a silicon substrate that is supposed to be used for fabrication of on-chip energy storage. By optimizing capacitively coupled plasma source power and oxygen flow, aspect ratio of 28:1 for holes of 2 μm in diameter was achieved. Bottling effect was suppressed by tuning capacitively coupled plasma, inductively coupled plasma sources and process pressure at the same time. The smoothness and purity of the hole walls are other parameters we investigate using atomic force microscopy and X-ray photoelectron spectroscopy.