PECVD Silicon Nitride for Damascene Applications

Abstract

AbstractA Pecvd silicon nitride film, Damascene Nitride™, is deposited in a PECVD chamber with a hollow cathode faceplate using silane and ammonia as precursor gases. Various techniques (FTIR, RBS-HFS, SIMS, TDS and BTS) were used to characterize the structure, composition, density and wet etch rate of the film. FTIR analysis indicates that Damascene Nitride is very similar to a high density plasma (HDP) nitride film. HFS 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 FSG. The film wet etch rate is 2 times slower than that of other PECVD nitrides, and the dielectric constant k was measured to be 6.8, which is lower compared to other PECVD nitrides and HDP CVD nitrides where k∼ 7.0 and 7.5, respectively. SIMS analysis shows that Cu diffusion is <250Å in the nitride, and low leakage current (10-10 A) is confirmed through BTS 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 k of Damascene Nitride, leads to a 5-6% reduction in RC delay when Damascene Nitride is used with low k dielectric materials.