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.