Performance of W sub 100-x N sub x Diffusion Barriers between (Si) and Cu

摘要

The performance of reactively RF sputtered tungsten nitride diffusion barriers inboth amorphous (W7,N24) and polycrystalline (W46N54) forms is studied in the (Si)/W100-xNx/Cu contact metallization by electrical measurements on shallow n+p junction diodes, backscattering spectrometry, and X-ray diffraction analyses. The DC characteristics of the diodes measured before and after vacuum annealings for 30 min reveal that about 120 nm thick, initially X-ray amorphous W76N24 film between (Si> and Cu preserves the integrity of the metallization up to 750 degC. The stability is confirmed also both by 2 MeV 4He2+ backscattering and X-ray diffraction analyses. Annealing at 800 deg C for 30 min results in overall intermixing of the layers, causing a shorting of the shallow junction diodes and forming a mixture of Cu, Beta-W2N, a-W, (Cu, Si)n', and W5Si3 phases in the structure observed by X-rays. Analysis by electrical measurements on shallow junction diodes and X-ray diffraction reveals that the initially polycrystalline form of the W100-xNx alloy is an inferior barrier. After annealing at 750 deg C for 30 min the DC characteristics of the diodes show a significant increase of the leakage current, and a mixture of Cu, Beta-W2N, and (Cu, Si) phases are found by X-ray diffraction analysis.