Gi. Font et al., EFFECTS OF WALL RECOMBINATION ON THE ETCH RATE AND PLASMA COMPOSITIONOF AN ETCH REACTOR, Journal of vacuum science & technology. A. Vacuum, surfaces, and films, 16(4), 1998, pp. 2057-2064
Citations number
10
Categorie Soggetti
Physics, Applied","Materials Science, Coatings & Films
A helicon plasma etch reactor is simulated using direct simulation Mon
te Carlo and particle-in-cell methods for a chlorine (Cl-2) feed gas f
low. Computations for the gas discharge are carried out by modeling th
e ions and neutrals as particles and by imposing the electrons as a ba
ckground condition conforming to experimental measurements. The neutra
ls and ions are then allowed to interact with the background electrons
and to relax to a steady state. The effects on the reactor flow field
and etch rate of chlorine atom recombination into chlorine molecules
at the walls is investigated. Results show that recombination at the w
alls results in the depletion of the amount of chlorine atoms (Cl) in
the reactor. The depleted chlorine atom population leads to lower ioni
zation levels and a diminished ion (Cl+) flux to the wafer. Consequent
ly, the etch rate is decreased by as much as 15% when compared to simu
lations without recombination. The creation of chlorine (Cl-2) molecul
es at the walls through recombination also provides a new source for n
egative ions (Cl-) which increases the electronegativity of the plasma
. In addition, the results of the simulation are compared with ion cur
rent and optical emission spectroscopy (OES) measurements. The Cl-Ar r
atio (measured by the OES technique) increases less than 20% from the
centerline to the wall of the reactor. An inspection of absolute densi
ties, however, reveals that the individual near-wall densities are as
much as a factor of 2 greater than the centerline densities. The trace
species, Ar, therefore, does not become distributed evenly throughout
the reactor. (C) 1998 American Vacuum Society. [S0734-2101(98)04604-1
].