Plasma treatment method for PECVD silicon nitride films for improved passivation layers on semiconductor metal interconnections

摘要

A plasma treatment method used to form improved PECVD silicon nitride film passivation layers over metal interconnections on ULSI circuits is achieved. The process is carried out in a single PECVD reactor. After depositing a thin silicon oxide stress-release layer over the metal lines, a plasma-enhanced CVD silicon nitride layer is deposited, and subsequently a plasma treatment step is carried out on the silicon nitride layer. The use of a sufficiently thin silicon nitride layer eliminates photoresist trapping at the next photoresist process step that would otherwise be trapped in the voids (keyholes) that typically form in the silicon nitride passivation layer between the closely spaced metal lines, and can cause corrosion of the metal. The plasma treatment in He, Ar, or a mixture of the two, is then used to densify the silicon nitride layer and to substantially reduce pinholes that would otherwise cause interlevel metal shorts.