In situ Monitoring of the Effects of Gas Mixtures on Ion Beam Depositions of Diamond-Like Carbon Films

A quadrupole mass spectrometer and a total ion-current measuring device have been utilized to monitor the ion compositions of gas mixtures of CH 4 /H 2 and CH 4 /H 2 /O 2 during the deposition for quality control and process optimization. An ultra high vacuum system using a 20 cm diameter RF excited (13.56 MIfz) ion gun and a four-axis substrate scanner has been developed for deposition of diamond-like carbon films for electrical, optical, and tribological applications. At a constant RF power of 179W, the mass spectra of gas mixture CH 4 /H 2 (1:2.5) showed the most abundant ion is CH 3 + . Addition of O 2 to the ion source has been found to affect the adhesion, deposition rate, and physical and chemical properties of the DLC films. By use of a mass spectrometer with and without the electron beam, the degree of ionization of CH 4 was calculated to be about 10%. As the concentration of O 2 was increased, all hydrocarbon ions decreased and H 3 O + increased, resulting in a decrease in the film growth rate and an increase in etching of Si and glass substrates. In general, the optical bandgap, adsorption coefficients and refractive index decreased as oxygen concentration increased. Raman spectra showed the G-peak position shifted toward the graphitic peak with narrow peak width as oxygen concentration increased. At ultra high vacuum, the coefficient of friction increased with increased adhesion on substrates as oxygen was increased.