Permittivity of amorphous hydrogenated carbon (a-C:H) films as a function of thermal annealing
New metal-insulator-semiconductor structures with a composite insulating layer, consisting of an amorphous hydrogenated carbon (a-C:H) film and a silicon dioxide, were obtained on silicon substrates. Carbon films were deposited on SiO2 layer by radio-frequency plasma-enhanced chemical vapor deposition (rf PECVD) method from methane. The structures were annealed at the annealing temperature Ta=250, 275, 300, and 350C. CV characteristics of the annealed and as-grown metal-amorphous carbon-oxide-semiconductor (MCOS) structures were examined at room temperature at a frequency of 1MHz and compared with CV characteristics of the classic metal-oxide-semiconductor (MOS) system. High-frequency CV curves of both MCOS and MOS structures were used for extracting the permittivity ?a-C:H of carbon films before and after thermal annealing. ?a-C:H showed no variations with subsequent annealing of the structure up to Ta=250C, but it was observed to decrease from 5.6 to 2.8 as the film was annealed from 250C up to 300C with the most rapid changes occuring between 275 and 300C.
permittivity amorphous hydrogenated carbon annealing cv characterization