Friday 03 Dec 2004
                   2:00-3:00pm
              4101 Etcheverry Hall
         University of California-Berkeley

contact: johnv@eecs.berkeley.edu
seminar list: http://ptsg.eecs.berkeley.edu/~johnv/seminar.html


Effects of the secondary electron emission coefficient in RF oxygen
discharge and Global model of oxygen discharges

M. Roberto (ITA, S. Jose dos Campos, Brasil)

Radio-frequency discharges in oxygen have a variety of applications for
plasma processing such as etching and surface modifications. In order to
investigate the structure of O2 RF discharges between parallel plates at
13.56 MHz we use the Particle-in-Cell plus Monte Carlo Collision Model.
The discharge contains the elementary particles O2+, O- and electrons. A
500sinwt voltage is used for 20 and 200 mTorr pressure. The dominant
process of generation of O- is the dissociative attachment, while the loss
processes are electron impact detachment, mutual neutralization and
detachment. For 20 mTorr process, O2+ and O- ions have a maximum density
at the center and the electron density is two orders of magnitude less
than that of these ions. However, at higher pressure, for 200 mTorr case,
the charged density profiles become broader, compared to the 20 mTorr
case. The influence of the secondary electron emission from the electrodes
is also verified. There is a value of this coefficient (of approximately
0.4) for which the electron density has the same order of magnitude of O2+
density. A shape change of the electron energy distribution function for
energies around 5 and 12 eV can be observed. Processes such as O2
ionization and dissociative attachment are responsible for this change.


Bio:

M. Roberto received the B.S. degree in physics from the Catholic
University of S.Paulo, Brazil, the M.S. degree from the Space
Research Institute, Brazil, and the Ph.D. degree in plasma
physics from the Aeronautical Technological Institute (ITA), Brazil. She
is currently an Associate Professor with the Physics Department, ITA,
where one of her research interests is cold plasmas discharge simulation
for application in deposition and etching processes. She also performs
research in the area of nonlinear dynamics and chaos.