a-SiC:H low-k deposition as copper diffusion barrier layer in advanced microelectronic interconnections

This study deals with the deposition of a new a-SiC:H material as barrier layer against copper diffusion in dual damascene interconnections for microelectronics. Indeed, new low-k dielectric barriers (k < 4) must be introduced into the future technologies allowing chip miniaturization and performances improvement. In this work, films were deposited on silicon wafers by RF-PECVD, with trimethylsilane and toluene as gas precursors and He as carrier gas. One of the main challenges of this work was to correlate the presence of phenyl rings in the film with the material dielectric constant. It is shown that soft plasma conditions such as high pressure, low dilution, high toluene flow rate, low power, and low temperature were necessary to incorporate phenyl rings in the film. These soft plasma conditions also allow increasing the total amount of carbon in the film. The film dielectric constant can be reduced from 4.5 to 3.1 depending on the carbon content incorporated and the correlation with the presence of phenyl rings in the film is discussed.