IN-SITU CHARACTERIZATION OF PLASMA-DEPOSITED A-C-H THIN-FILMS BY SPECTROSCOPIC INFRARED ELLIPSOMETRY

A computer-controlled rotating polarizer ellipsometer, operating in th e infrared spectral region between 3.00 and 3.75 mu m, has been develo ped for Bt situ characterization of amorphous hydrocarbon (a-C:H) thin films, deposited from methane in a rf plasma-enhanced chemical vapor deposition reactor. Spectroscopic IR ellipsometry permits insight into the chemical bonding structure of a-C:H coatings by the nondestructiv e detection of infrared stimulated C:PI stretch vibrations. It is show n that the sp(2)CH(x)/sp(3)CH(x) ratio, the content of bonded hydrogen , the infrared linewidth, and the real refractive index of the films d epend on the negative self-bias voltage, which is formed at the sample s during the deposition process. A transition from a-C:H films with po lymerlike properties to hard a-C:H films was attained at a self-bias v oltage of approximately -75 V.