EFFECT OF TIME-VARYING AXIAL MAGNETIC FIELD ON HIGH ASPECT RATIO CONTACT HOLE ETCHING

초록

Time-varying axial magnetic field is added to conventional inductively coupled plasma. Weak axial magnetic field of about 10-15 G is obtained by a pair of Helmholtz coils attached to the outside of the chamber. Efficient power transfer from RF source to plasma is enhanced by the axial magnetic field. High aspect ratio deep-sub-micron contact holes in BPSG oxide have been etched by C4F8/Ar plasma. The role of deposition of polymeric precursors in the etching process is monitored. By means of appearance mass spectroscopy (AMS), the distributions of CFx+ ions and CFx radicals are measured as a function of magnetization frequency. The axial magnetic field is found to influence the densities of fluorocarbon ions (CFx+; x=1-3) and F and CFx radicals. X-ray photoelectron spectroscopy (XPS) studies have allowed analysis of high aspect ratio contact holes etching. The XPS analyses show that the fluorocarbon polymer on BPST strongly varies with the magnetization frequency. 0.2? diameter contact holes with aspect ratio of 10 are successfully fabricated in this system.