The growth of solid residues within PECVD (plasma enhanced chemical va
pour deposition) reactors has been extensively studied because of its
implications for wafer particle contamination and is often referred to
as dusty plasmas. On dielectric CVD (DCVD) production systems the coa
ting of chamber walls and vacuum exhaust line with residues addresses
also the issue of system maintenance. A common solution consists of pe
riodically cleaning the deposition chamber by ionizing a PFC (perfluor
o-compound) gas such as CF4, NF3 or C2F6 This generates free fluorine
radicals that dry etch the residues deposited on chamber walls. Howeve
r, because of limited fluorine radical lifetime, this clean process is
not efficient in the vacuum exhaust line where residues accumulate. W
e propose an active solution to address the issue of solid waste treat
ment on a production DCVD system. We review the particular case of sil
icon nitride deposition, which is one of the worst known processes in
terms of particle generation. These considerations are also valid for
silicon oxide, silicon oxynitride, silicon carbide and amorphous silic
on deposition processes. Here we report on our investigation on the pa
rticle formation, composition and morphology within a PECVD chamber an
d the deposition of these particles on chamber walls and vacuum exhaus
t line. We describe a method to design an efficient precipitator that
traps the particles immediately downstream of the deposition chamber.
The trapping uses gravitational and electrostatic means. This system d
oes not necessitate any disposal procedure because of its capability t
o perform an in situ plasma assisted clean, reactivating the effluent
PFC gas from the processing chamber. Here, the system is referred to a
s downstream plasma apparatus (DPA).