New microwave plasma development with extended operating conditions

This work was done in the 'Laboratoire de Physique Subatomique et de Cosmologie (IN2P3, Grenoble)' during a collaboration with Thales. The aim of the project was the development of a new generation of microwave plasma with extended operating conditions in the pressure range 0.5 mtorr to 10 torr in argon. The presented work consists of: i) designing applicators based on sections of?/4 length serving as impedance transformers between the generator and the plasma with impedance of given assumed value (approximate impedance adaptation); ii) experimentally determine the real plasma impedance (the real part and the imaginary part) for given operating conditions from the measurement of modulus and phase of the reflection coefficient S11; iii) resize the different sections of the applicator by digital simulation taking the real plasma impedance into account; iv) finally, verify experimentally that the impedance adaptation between the generator and the plasma is correct. The obtained results clearly demonstrate that it is possible, at a given frequency (here 2.45 GHz), to design and size a plasma source with an efficiency greater than 80 % for a window in pressure (at least one decade) equivalent to an operating window in terms of plasma parameters. These individual sources with localized absorption of microwaves can be used in numbers to achieve uniform plasmas via their distribution over two-dimensional (planar sources) or tri-dimensional (volume plasma) networks, and thus for industrial surface treatments. (author)