A METHOD TO ENHANCE THE ADHESION OF SILICON NITRIDE TO LOW-K FLUORINATED AMORPHOUS CARBON USING A SILICON CARBIDE ADHESION PROMOTER LAYER

摘要

A plasma enhanced chemical vapor deposition (PECVD) process is provided for depositing one or more dielectric material layers on a substrate for use in interconnect structures of integrated circuits. The method comprises the steps of depositing a fluorinated amorphous carbon (a-F:C) layer on a substrate by providing a fluorine containing gas, preferably octafluorocyclobutane, and a carbon containing gas, preferably methane, in ratio of approximately 5.6, so as to deposit a a-F:C layer having an internal compressive stress of approximately 28 MPa. After deposition the film is annealed at approximately 400° C. for approximately two hours. An adhesion promoter layer of relatively hydrogen-free hydrogeneated silicon carbide is then deposited on the a-F:C layer using silane (SiH4) and methane (CH4) as the deposition gases. The silicon carbide layer may be deposited at a rate of approximately 180 Å per minute and typically results in deposition of a silicon carbide layer having an internal compressive stress of approximately 400 MPa. The deposited silicon carbide layer has relatively few hydrogen bonds thereby yielding a compact structure which promotes adhesion of the a-F:C layer to a silicon nitride layer and to the a-F:C layer, and which reduces diffusion of fluorine through the silicon carbide layer. A silicon nitride layer is then deposited on the adhesion promoter layer, the deposition materials preferably comprising silane (SiH4) and nitrogen (N2) in a ratio of 30:100 at 400° C. The silicon nitride layer has relatively few hydrogen bonds thereby resulting in a layer having an internal compressive stress of approximately 240 MPa. This stacked layer structure has thermal stability and resists peeling and cracking up to 450° C., and the a-F:C dielectric layer has a dielectric constant (k) as low, or lower, than 2.5.