engleski

The efects of deposition conditions and annealing temperature on the structure and morphology of Ta-N thin films

Tantalum nitrides (Ta-N) are used in a wide variety of applications such as diffusion barrier in magnetoresistive random access memory, wear and corrosion-resistant materials, high-speed thermal printing head, as well as thin film resistors. Structural properties of magnetron-sputter-deposited Ta-N thin layers were investigated in correlation with electrical properties. We focused on the impact of varying nitrogen content in the deposition chamber during synthesis as well as post-deposition annealing in the temperature range up to 950°C. Thin Ta-N films were grown on silicon wafers, pre-deposited with 100 nm SiO2 buffer layer, kept at room temperature (RT) or at 550°C during deposition. The films were structurally and morphologically characterized with grazing incidence X-ray techniques: specular reflectivity (XRR), diffraction (GIXRD) and small angle scattering (GISAXS). Structural features in films deposited at RT strongly depend on the Nitrogen partial flow rate (pN2) ; as pN2 increases the crystal structure changes: from amorphous Ta-rich (pN2 =10%), to fcc-TaN (pN2 =20-40%), to amorphous N-rich (pN2 >60%) ; the density of the films are correspondingly affected. Upon annealing, amorphous films crystallize into fcc-TaN (pN2=10%) and Ta4N5 or Ta3N5 (pN2>60%), while as deposited fcc-TaN films are stable up to 950°C with releasing stacking fault deformations. The loose homogenous structure of the films deposited at high pN2>60% anneals into particulate nanostructure with the average grain size increasing from 3nm (annealing @550°C) to 15 nm (annealing @950°C). All these findings are evaluated in relation with electrical measurements of the film resistivity to gain deeper insight into material parameters relevant for electronic devices.

annealing ; structure ; morphology ; Ta-N ; thin films

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