Characteristics of fine contact hole etching have been investigated in
hydro-fluorocarbon magneto-microwave plasma focusing oil the z compon
ent of the gradient of magnetic field at 0.0875 T (dB/dz) and peak-to-
peak voltage of RF bias (V(pp) as parameters. Decrease of dB/dz drasti
cally decreases the etch rate of boro-phospho silicate glass (BPSG), c
ritical dimension loss (defined as diameter of the top of contact hole
minus diameter of the bottom of resist) and selectivity over heavily
doped n-type polycrystalline silicon (n+ poly Si) and resist in fine c
ontact holes. The changes of etching characteristics are correlated wi
th neither F/C ratio nor C1s spectrum of deposited film, but with depo
sition rate in the region of high V(pp), which presumably respects the
change of incident CF(m)+ ion species with dB/dz.