Defect-Free Reactive Ion Etching of Silicon by SiF4/Cl2 Plasma

Abstract

Defect-free reactive ion etching (RIE) of silicon has been carried out using a mixture of SiF₄ and Cl₂ as the etching gas. The etching mechanism is investigated with a quadrupole mass spectrometer and the main reaction products are found to be Si₂F₆ or SiF₃ for the Si etching and Si₂F₆O for the SiO₂ etching. The deposition of (SiF₂) _n which occurs during the etching of silicon can be prevented by adding Cl₂ gas to the SiF₄. A defect-free Si surface, characterized by deep-level transient spectroscopy (DLTS), is obtained by RIE using a mixture of SiF₄ (70%) and Cl₂ (30%) at a pressure of 7.0 Pa with an rf power density of 0.24 W/cm².