Development and Characterization of a PECVD Silicon Nitride for Damascene Applications

A silicon nitride film, Damascene Nitride™, is deposited in a plasma-enhanced chemical vapor deposition (PECVD) chamber with a conical hole faceplate using silane and ammonia as precursors. Fourier transform infrared analysis indicates that Damascene Nitride is similar to a high-density plasma nitride film. Hydrogen forward scattering spectroscopic analysis shows the film’s hydrogen content to be 13%, ∼6% less than other PECVD nitride films, leading to a 20% improvement in etch selectivity to fluorinated silicate glass. Secondary ion mass spectrometric analysis shows that Cu diffusion is <250 Å in the nitride; a low leakage current ( 10 − 12 A ) is confirmed through bias temperature stress testing. The higher density of Damascene Nitride leads to higher etch selectivity and better Cu barrier properties, allowing a thinner nitride film to be used. Thinner nitride layers, in addition to the lower dielectric constant (κ) of Damascene Nitride, leads to a 5-6% reduction in resistance-capacitance delay when Damascene Nitride is used with low-κ dielectric materials.