Plasma enhanced chemical vapor deposition of fluorocarbon thin films via CF3H/H2 chemistries: Power, pressure, and feed stock composition studies

Since fluorocarbon thin films exhibit unique properties such as a low coefficient of friction, a low index of refraction, chemical inertness, and hydrophobicity they continue to have industrial interest. The ease by which plasma enhanced chemical vapor deposition fluorocarbon thin films properties can be varied is of interest to the present study. Further, it has been found that these properties, such as index of refraction, hydrophobicity, stress and film hardness can be varied much more easily and substantially with the addition of hydrogen to a CxFy feed stock. The present study is continued work which has investigated the chemical structure and properties of fluorocarbon films as a function or pressure, radio frequency (rf) power density and H2/CF3H feed stock. As a function of rf power density, the index of refraction exhibited a large dependence for the thin films deposited from CF3H with 10 sccm H2. Namely, at 0.0877 W/cm2 the film had an index of 1.420 which dropped to 1.388 at 0.219 W/cm2. The addition of H2 to the CF3H feed stock decreased the intrinsic stress from 430 MPa tensile with no H2 added to 70 MPa tensile with a H2/CF3H ratio of 0.75 (30 sccm H2). Further, the addition of hydrogen qualitatively increased the hardness of the films due to a higher crosslinking density and increased the film thickness uniformity due to the high molecular diffusivity of hydrogen.