Realization of Three-Dimensional Micro and Nano-Structures on Silicon Substrates

The realization of nano and micro-sized, highly-featured, 3-dimensional structures on Si substrates is reported where a single mask in a hydrogen-assisted deep reactive ion etching is exploited. Three main gases of oxygen, hydrogen and SF6 are used in a sequential passivation and etching process to achieve high aspect ratio features. The ows of gases, and the plasma power and timing of each subsequence are the main parameters to achieve the desired three-dimensional etching by controlling the under-etching and recovery steps, which leads to the formation of unique features directly on silicon substrates. Depending on the plasma power, etch-rates as high as 0.75 m/min can be obtained. The plasma power can reach a high value of 1 W/cm2 over a large area of 20  15 cm2. In addition, features with a controllable under-etching and a recovery with more than 8 m in the sidewall recession have been achieved. Furthermore, values of aspect ratios higher than 40-50 can be obtained. The formation of nano-wall features is also reported.