Heterogeneous Particle Formation during Low Pressure Etching of Silicon Dioxide

Abstract

Particles generated during highly selective SiO2 etching using a magnetically enhanced reactive ion etcher and an inductively coupled plasma etcher are investigated. The pressure ranges from 3 to 60 mTorr in mixtures of CHF3, CF4, C2F6, C4F8, O2 and Ar. Polymers at the reactor surface are the major contributors to particle formation, and particles fall onto the wafer during the etching process. The formation mechanism is heterogeneous. By quadrupole mass spectrometry and optical emission spectroscopy, C2 and Cx Fy species can be used to monitor the level of particle contamination in highly selective SiO2 etching. During the Ar/O2 dry cleaning process to decontaminate the plasma chamber, concentrations of C2 and Cx Fy radicals and CO products decrease with the removal of the polymers from the chamber wall, while the concentrations of O and O2 radicals increase.