Fluorocarbon radicals and surface reactions in fluorocarbon high density etching plasma. I. O2 addition to electron cyclotron resonance plasma employing CHF3

Abstract

Gas phase reactions of CFx (x=1−3) radicals and F atoms in an electron cyclotron resonance (ECR) downstream plasma were investigated at 300 W and a CHF3 pressure of 0.4 Pa by adding O2 to CHF3 using infrared diode laser absorption spectroscopy and actinometry, respectively. By adding a small amount of O2 to CHF3, the CF and CF2 radical densities rapidly decreased, while the CF3 radical density rapidly increased but then decreased with further addition of O2 to CHF3. These reaction mechanisms in the plasma were evaluated on the basis of measurement results of CFx (x=1−3) radical and F atom densities. Under the same conditions as the measurements of radical densities, the etching rates of Si and SiO2 were measured. Furthermore, the etched Si surfaces were also analyzed with x-ray photoelectron spectroscopy. The etching mechanisms for Si and SiO2 in the CHF3/O2 ECR plasma were investigated by connecting these etching characteristics on Si and SiO2 with the behaviors of CFx (x=1−3) radical and F atom densities. The Si etching rate was affected primarily by the concentrations of the CF and CF2 radicals and F atoms in the plasma.