Effect of ion bombardment on the chemical and the mechanical properties of silicon-nitride thin films deposited by using PECVD with SiH₄/NH ₃/Ar gases at low temperature

The influence of the ion bombardment energy controlled by using the d.c. bias voltage from no-bias to -200 V on the chemical and the mechanical properties of Si_xN_y, deposited by plasma enhanced chemical vapor deposition (PECVD) at substrate temperatures lower than 100°C was investigated for applications to thin film diffusion barriers for organic electronic devices. The deposited film was a silicon-rich Si_xN _y thin film having oxygen and hydrogen as major impurities. A change in the d.c. bias voltage up to -200 V during the deposition changed the properties, such as the stress, the hardness, the surface roughness, etc. in addition to the deposition rate. A lower stress, a harder material, and a smoother surface could be obtained by applying a moderate bias voltage of about -100 V through a change in the bonding states of the oxygen impurity in the film, a densification of the film, and an increased surface mobility of the deposited atoms.