Reactive Ion Etching of SiC Thin Films by Mixtures of Fluorinated Gases and Oxygen

Abstract

Reactive ion etching (RIE) of thin films has been investigated in depth in a variety of fluorinated gas plasmas, such as , , and mixed with oxygen. The optical emission spectrum of the RF plasma and the plasma‐induced dc bias were monitored to explore the etching mechanisms. Argon actinometry has been used to convert the plasma emission intensity to relative concentration of plasma species in order to more accurately quantify the etching process. Plasma conditions, such as composition of gas mixture, pressure, and power were investigated in order to achieve selective etching and anisotropic patterning of thin films. A etch rate ratio higher than unity was obtained for the first time by using and at 200W, 20 sccm, 20 mtorr plasma conditions. The best anisotropic profile was obtained by using gas in the RIE mode. A critical dc bias level, around −300 V, appears to separate regimes of chemical and physical rate limiting step domination of the etch rate. A carbon‐rich surface on the etched films was found for all gases. The etching mechanisms in fluorinated gases were deduced from loading experiments, surface analysis, and other etching phenomena. Evidence of the chemical reaction between carbon and oxygen is presented. No evidence of chemical reaction between fluorine and carbon has been observed. A combined chemical and physical etching model, supported by experiments, is suggested. A carbon blocking mechanism is proposed to understand the etching profile.