[en] At the CEA Laser 'Megajoule' facility, amorphous hydrogenated carbon (a-C:H or CH_x) is the nominal ablator used to achieve inertial confinement fusion experiments. These targets are filled with a fusible mixture of deuterium-tritium in order to perform ignition. Since the achievement of ignition greatly depends on the physical properties of the shell, there must be precise control of thicknesses, doping concentration, and roughness. Experimental devices associated with suitable characterizations are described in this paper. The tolerances and yields for each specification are also presented. Some specifications are largely reached; high-frequency surface roughness due to isolated surface defects appears to be the main yield-limiting factor. A microscopic approach of stress thin film measurement is described to examine oxygen uptake in CH_x film. (authors)