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Volatile Ni(II) complexes with beta-diiminates derived - novel precursors for MOCVD processes


N. Morozova1 and K. Zherikova1

1Nikolaev Institute of Inorganic Chemistry of SB RAS, Russia

Keywords: nickel beta-diiminates, MOCVD
property: thermal properties
material: nickel films

Nickel films find extensive applications in advanced technology. Ni is promising material for microelectronics and nanotechnology because the electrical resistivity is low and the oxidation resistance is high. MOCVD technique is the method to deposit film with good-quality step coverage on patterned structures. So, new Ni precursor is strongly required. The synthesis of volatile nickel(II) bis-(beta-diiminates) derived from acetylacetone of the general formula Ni(CH3C(NR)CHC(NR)CH3)2, where R is H, CH3, is described. In order to identify a resulting N4 nickel(II) chelates different physicochemical methods were used. Analysis of nickel(II) beta-diiminates mass spectra has shown that Ni precursors transfer to gas phase without decomposition. The thermal behavior of the Ni(II) bis-(beta-diiminates) complexes and for comparison Ni(CH3COCHC(NH)CH3)2 in the solid state was investigated by means of TG and DSC, the thermodynamic characteristics of the melting processes (m.p., ΔmeltHm.p., ΔmeltSm.p.) were determined. TG analysis indicated that Ni(CH3COCHC(NH)CH3)2 is more stable than its diimine analogies, but is less volatile. The temperature dependences of saturated vapor pressure for Ni(II) beta-diiminates were studied by means of the Knudsen method with mass spectrometric registration of gas phase, the standard thermodynamic parameters of sublimation process were determined. The vapor thermodecomposition of Ni(II) precursors was studied in vacuum and hydrogen using in situ high temperature mass spectrometry, temperature range of thermolysis and gas by-products were determined. The information about thermal behavior of Ni precursors was used for choice of Ni MOCVD parameters. Ni films were obtained on Si/Ta substrates and studied by different methods: SEM, XRD, XAFs etc. Thickness of Ni films was no more 500 Å. It was shown by XRD, that film crystal phase consists of only metal with cell parameters 3.526(2) Å. By means of XAFs was determined that Ni remains mainly as Ni0, no oxidated phase was definited (method accuracy is 5%). By this approach it was demonstrated that MOCVD Ni films using nickel(II) bis-(beta-diiminates) precursors could achieve adhesive metal films to tantalum substrates.


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