CF X (X=1–3) radical densities during Si, SiO2, and Si3N4 etching employing electron cyclotron resonance CHF3 plasma

Abstract

The roles of CFX(X=1–3) radicals in etching reactions of Si, SiO2, and Si3N4 in an electron cyclotron resonance (ECR) CHF3 plasma have been investigated using infrared diode laser absorption spectroscopy (IRLAS). CFX radical densities in the plasma were measured as functions of Si, SiO2, and Si3N4 etch rates. The radical densities decreased with increasing etch rates of Si3N4, SiO2, and Si. Influences of byproducts from the etched substrates and substrate biases on CFX radicals were also investigated. Moreover, the FCN molecular density was measured using IRLAS in the ECRCHF3 plasma in the presence and absence of Si3N4 film. It was found that the FCN molecule was abundantly formed in the plasma during etching of Si3N4. The IRLAS measurement of the FCN molecule is considered to be suitable for detecting the FCN molecule and in situ monitoring of Si3N4 etching.