Oxygenated polymeric thin films deposited from toluene and oxygen by remote plasma enhanced chemical vapor deposition

Highly oxygenated polymeric films have been deposited by remote plasma enhanced chemical vapor deposition using a plasma of oxygen and toluene. The films grew in a very narrow range of pressures around ∼1 Torr, while at lower or higher pressures no deposition was observed. The differences in the optical emission spectra of the plasma corresponding to the deposition and nondeposition conditions reveal that the precursor is not effectively fragmented at low pressures. The films have been analyzed by ultraviolet–visible absorption spectroscopy, x-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The analysis by these techniques shows that the films have a high percentage of oxygenated functional groups (–OH, –CO, –COO) and a low percentage of hydrocarbon groups (C–H, –C–C–, –C=C–, etc.). The overall O/C ratio in these thin films was 0.8. Thin films with a lower O/C ratio have been obtained by applying a dc bias to the substrate and combining bias and Ar addition to the plasma. To study the possible use of the oxygenated polymeric thin films as sacrificial layers, the stability of the thin films has been studied under different etching treatments, including Ar and O2 plasma treatments and Ar+ ion bombardment. The high etching rates under oxygen plasma treatments at low pressures support the use of these thin films as sacrificial layers. It is also found that the etching rate of the different thin films increases with the content of oxygen.