Y. Chinzei et al., HIGHLY SELECTIVE SIO2 SI ETCHING AND RELATED KINETICS IN TIME-MODULATED HELICON WAVE PLASMA/, JPN J A P 1, 35(6A), 1996, pp. 3585-3589
Highly selective SiO2/Si etching has been achieved by using time-modul
ated helicon wave plasma (HWP) employing C4F8/H-2 mixture. Time modula
tion of less than 5 mu s. effectively controlled the electron energy,
suppressing redissociation of HF. The selectivity window for H-2 conce
ntration was widened by synchronizing the phase of 100 kHz self-bias t
o the phase of 100 kHz time-modulated HWP. This is performed by extens
ion of the polymer point to higher H-2 concentration due to bombardmen
t of more ions. Measurements of AMS of radicals and XPS of polymer for
med on the Si surface suggest that CF1 radicals contribute to the poly
mer formation and produce carbon-rich film in the presence of hydrogen
in the case of the pulse discharge in which electron energy is contro
lled and dissociation is suppressed. Measurement of CF1/F ratio also s
upported this conclusion.