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

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.