Three-dimensional etching of silicon substrates using a modified deep reactive ion etching technique

Abstract

We report realization of highly featured three-dimensional micro- and nano-structures on silicon substrates with a single masking layer using a hydrogen-assisted deep reactive ion etching process. Three gases of oxygen, hydrogen and SF6 are used in a sequential passivation and etching process to achieve high aspect ratio features. By controlling the flows of these gases and the power and timing of each subsequence, it is possible to achieve desired deep vertical etching with controlled underetching and recovery, yielding three-dimensional features directly on silicon substrates. Etch rates up to 0.75 µm min−1 have been obtained with a low plasma power density of 1 W cm−2. Also features with a controllable underetching with more than 8 µm in sidewall recession have been achieved. The three-dimensional structures can be used as a mold for polymers as well as a holding substrate for projection display applications where an electro-chromic material (WO3) has been used.