Protective hardmask for producing interconnect structures

Abstract

The present invention provides a permanent protective hardmask which protects the dielectric properties of a main dielectric layer having a desirably low dielectric constant in a semiconductor device from undesirable increases in the dielectric constant, undesirable increases in current leakage, and low device yield from surface scratching during subsequent processing steps. The protective hardmask further includes a single layer or dual layer sacrificial hardmask particularly useful when interconnect structures such as via openings and/or lines are formed in the low dielectric material during the course of making the final product. The sacrificial hardmask layers and the permanent hardmask layer may be formed in a single step from a same precursor wherein process conditions are altered to provide films of differing dielectric constants. Most preferably, a dual damascene structure has a tri-layer hardmask comprising silicon carbide BLoK™, PECVD silicon nitride, and PECVD silicon dioxide, respectively, formed over a bulk low dielectric constant interlevel dielectric prior to forming the interconnect structures in the interlevel dielectric.