Formation of nano-cone structures on silicon via maskless reactive ion etching

We report a maskless reactive ion etching (RIE) method that employs O2, CHF3 and SF6&O2 gas plasma sequentially to generate nano-cones structures on silicon substrates with good uniformity. In this method, nano-cones are made under carefully-controlled conditions that restrict their width and height to 60 nm and 82 nm, respectively. According to the formation trend of nano-cones under different plasma conditions, the contributing mechanism is discussed. With the multiple effects of etching time, chamber pressure and self-bias voltage, the height, angle and density of nano-cones will be varied within a certain range. Given these variations, a nano-cone structure with good uniformity was generated using the following parameters: etching time of 300 s, chamber pressure of 40 mtorr, self-bias voltage of 75 W, and a SF6&O2 flow ratio of 75 sccm: 75 sccm. The experiment in this report demonstrates a promising way to fabricate silicon-based nano-cone structures for photonic and optoelectronic applications, with advantages of the controllability and compatibility of its dry-etching process.