Dependence of Etch Selectivity of SiO2 Etching on the Axial Magnetic Field Added to ICP

초록

Effects of time-varying axial magnetic field added to an ICP have been studied in terms of plasma characteristics and etching performance. The time-varying field is provided by ac current to the upper coil of a Helmholtz coils. The electron energy distribution function is measured as a function of the magnetization frequency, and shows energy of high energy tail becomes higher with the axial magnetic field. The periodic variations of plasma density and electron temperature are also observed by time resolved Langmuir probe with Boxcar-mode. We have measured the CFx+ (x=1-3) ion density and its energy distribution function using Quadrupole Mass Spectrometry with an energy analyzer. The enhanced etch selectivity of SiO2 over photoresist and silicon in axial magnetic field added to ICP is investigated in C4F8/Ar plasma. The frequency of the axial magnetic field is found to affect the etch selectivity and etch profile.