Black silicon formation using cryogenic etching and photoresist layer

A series of experiments were conducted to develop the plasma etching of black silicon through a layer of polydimethylglutarimide (PMGI) photoresist. The silicon wafers were previously subjected to wet-chemical treatment. A ~25 nm thick photoresist layer facilitates the process of creating regular black silicon structures on substrates with a diameter of 100 mm. The etching process was varied in terms of the sulfur hexafluoride (SF₆) and oxygen (O₂) gas mixture ratio, RF power applied to the substrate holder (bias power), inductively coupled plasma (ICP) power and chamber pressure. Increasing the bias power from 10 to 30 W under otherwise constant conditions enhances the etching rate. Reducing the pressure in the reactor from 10 to 5 mTorr at a constant gas flow rate leading to a higher etching rate. Increasing the proportion of oxygen in the SF₆/O₂ gas mixture (2:1) enhances passivation, reducing the black silicon structures size.