Glow discharge processing in the liquid crystal display industry
The active matrix display industry is briefly presented. The most challenging aspect for plasma source design lies in the substrate size which is now entering the 1-2 m range. This paper focuses on the conventional planar RF capacitor at 13.56 MHz. A detailed analysis of the local perturbation due to a hole in the metal susceptor illustrates the process effects of various plasma microscopic parameters. It appears that not only the process rate must be kept uniform, but also the ion bombardment. It is also shown that very wide capacitive reactors no longer follow some classical rules: (1) plasma RF conductivity is limited, its propagation is shown to be described by a telegraph equation, in agreement with numerical modelling and electrostatic measurements, (2) the RF wavelength is no longer infinite compared to the dimensions, this leads to standing waves. The presence of the plasma is shown to worsen the effect by shortening the RF propagation wavelength.