Etch Selectivity of Silicon Dioxide over Titanium Silicide Using CF₄/H₂ Reactive Ion Etching

Abstract

Selective reactive ion etching of SiO2 over TiSi2 in a flexible diode reactor has been studied using CF4/H2 and CHF3. Different flow rates, and quartz and Teflon electrode materials, were evaluated and shown to have a profound effect on the SiO2/TiSi2 etch selectivity. Addition of H2 greatly increases the selectivity without markedly affecting the oxide etch rate. Teflon was shown to be the more effective electrode material over quartz for high oxide etch rates and selectivity with the addition of H2 to the plasma. Increasing the total flow rate increased the SiO2/TiSi2 etch selectivity in most cases, and we have achieved SiO2/TiSi2 etch rate ratios greater than 40:1. Using x-ray photoemission spectroscopy, a TiFx-rich surface region was observed under all conditions. The lowering of the TiSi2 etch rate correlates to the increase in fluorocarbon film and appears to be primarily due to the selective formation of the film on TiSi2 and not on SiO2. © 1989, The Electrochemical Society, Inc. All rights reserved.