Amorphous Ta-nanocrystalline RuO_x diffusion barrier for lower electrode of high density memory devices

Authors: Yoon, Dong-Soo; Baik, Hong; Lee, Sung-Man; Roh, Jae

Source: Journal of Electronic Materials, Volume 30, Number 5, May 2001 , pp. 493-502(10)

Publisher: Springer

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Abstract:

The effects of the amount of RuO₂ added in the Ta film on the electrical properties of a Ta-RuO₂ diffusion barrier were investigated using n⁺⁺-poly-Si substrate at a temperature range of 650-800°C. For the Ta layer prepared without RuO₂ addition, Ta₂O₅ phase formed after annealing at 650°C by reaction between Ta and external oxygen, leading to a higher total resistance and a non-linear I-V curve. Meanwhile, in the case of the Ta film being deposited with RuO₂ incorporation, not only a lower total resistance and ohmic characteristics exhibited, but also the bottom electrode structure was retained up to 800°C, attributing to the formation of a conductive RuO₂ crystalline phase in the barrier film by reaction with the indiffused oxygen because of a Ta amorphous structure formed by chemially strong Ta-O or Ta-Ru-O bonds and a large amount of conductive RuO₂ added. Since a kinetic barrier for nucleation in formation of the crystalline Ta₂O₅ phase from an amorphous Ta(O) phase is much higher than that of crystalline RuO₂ phase from nanocrystalline RuO_x phase, the formation of the RuO₂ phase by reaction between the indiffused oxygen and the RuO_x nanocrystallites is kinetically more favorable than that of Ta₂O₅ phase.

Keywords: RuO2; Ta film; diffusion barrier; poly-Si substrate

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11664-001-0089-9

Affiliations: 1: Email: dsyoon@sr.hei.co.kr

Publication date: 2001-05-01