Patent ID: 7618686

Claim:
A method for plasma treatment of a non-conductive elongated hollow substrate having a length, a transverse dimension transverse to the length and an internal cavity, by an apparatus for plasma treatment including a plurality of ionization energy sources disposed adjacent to each other along said length, each ionization energy source including a first and a second source part that face each other and are dimensioned to produce there between a uniform field covering at least said transverse dimension, said method comprising the steps of: a) placing the substrate to be treated in between said first and second source parts of said ionization energy sources; b) injecting a process gas inside the cavity of said substrate, said process gas containing a precursor to be consumed for plasma treatment of said substrate; and c) maintaining pressure inside the cavity of said substrate within a predetermined range; and d) powering from radio frequency power supply means the ionization energy sources sequentially, thus selectively creating plasma inside the cavity of said substrate at a location corresponding to the respective powered ionization energy source, said radio frequency power supply means delivering power at a frequency around 10 kHz to 100 MHz; wherein said step b) of injecting the process gas inside the cavity of said substrate is repeated at least before the powering of each ionization energy source to replace consumed precursor so as to maintain a constant precursor concentration each time plasma is created.