Rjmm. Snijkers et al., MASS-RESOLVED ION ENERGY MEASUREMENTS AT BOTH ELECTRODES OF A 13.56MHZ PLASMA IN CF4, Journal of applied physics, 79(12), 1996, pp. 8982-8992
The ion energy distributions (IEDs) at the electrodes ina capacitively
coupled 13.56 MHz plasma in CF4 have been measured mass resolved with
a Balzers quadrupole in combination with a home-built energy analyzer
. Mass-resolved determination offers the possibility to compare the LE
D of different ions achieved in the same sheath. The IEDs have been de
termined at both the largest and the smallest electrode. Apart from th
e IEDs of the CF4 species, the IEDs of ionic species in plasmas in arg
on and nitrogen also were determined. Apart from the CF4 ionic species
CF3+ CF2+, CF+, and F+, CHF2+ ions also are present in the CF4 plasma
due to residual water in the reactor. Because the CHF2+ ions are not
produced in the sheath and because we do not detect elastically scatte
red ions, the IEDs of these ions show the typical bimodal distribution
for rf plasmas which corresponds to an IED of ions which have not col
lided in the sheath. From these IEDs we can obtain the sheath characte
ristics, such as the averaged sheath potential. From the IEDs of CFnions one can conclude that, in the sheath of the CF4 plasma, a large n
umber of chemical reactions takes place between the CnF(n)(+)7 ions an
d the neutrals. (C) 1995 American Institute of Physics.