Electrical properties of platinum interconnects deposited by electron beam induced deposition of the carbon-free precursor, Pt(PF₃)₄

Comprehensive analysis of the electrical properties, structure and composition of Pt interconnects, developed via mask-less, electron beam induced deposition of the carbon-free Pt precursor, Pt(PF₃)₄, is presented. The results demonstrate significantly improved electrical performance in comparison with that generated from the standard organometallic precursor, (CH₃)₃Pt(C_pCH₃). In particular, the Pt interconnects exhibited perfect ohmic behavior and resistivity that can be diminished to 0.24 × 10^-3 Ω cm, which is only one order of magnitude higher than bulk Pt, in comparison to 0.2 Ω cm for the standard carbon-containing interconnects. A maximum current density of 1.87 × 10⁷ A cm^-2 was achieved for the carbon-free Pt, compared to 9.44 × 10⁵ A cm^-2 for the standard Pt precursor. The enhanced electrical properties of the as-deposited materials can be explained by the absence of large amounts of carbon impurities, and their further improvement by postdeposition annealing in N₂. In-situ TEM heating experiments confirmed that the annealing step induces sintering of the Pt nanocrystals and improved crystallinity, which contributes to the enhanced electrical performance. Alternative annealing under reducing conditions resulted in improved performance of the standard Pt interconnects, while the carbon-free deposit suffered electrical and structural breakage due to formation of larger Pt islands.