Remote-plasma chemical vapor deposition of conformal ZrB₂ films at low temperature: A promising diffusion barrier for ultralarge scale integrated electronics

High-quality ZrB₂ thin films have been deposited at substrate temperatures as low as 300°C by a new method: remote hydrogen-plasma chemical vapor deposition from the single-source precursor Zr(BH₄)₄. Carrying out the deposition in the presence of atomic hydrogen generates films with properties that are far superior to those deposited by purely thermal methods; the latter are boron-rich, oxidize readily in air, and adhere poorly to the substrates. In contrast, the films generated at a substrate temperature of 300°C in the presence of atomic H have a B/Zr ratio of 2, a resistivity of 40 μcm, an oxygen content of ≤4at.%, and are fully conformal in deep vias. A 20 nm thick amorphous film of ZrB₂ on c-Si(001) prevents Cu indiffusion after 30 min at 750°C. We propose that the beneficial effects of atomic hydrogen can be attributed to promoting the desorption of diborane from the growth surface.