Atomic layer deposition of RuO2 using a new metalorganic precursor as a diffusion barrier for Ru interconnect

Abstract

We report the ALD RuO2 process using a new Ru metalorganic precursor, tricarbonyl (trimethylenemethane) ruthenium [Ru(TMM)(CO)3], and molecular oxygen (O2) as a reactant at the relatively low temperature of 180 °C for a diffusion barrier application of Ru interconnect. RuO2 thin films could be prepared by controlling the reactant and precursor pulsing time ratio (to2/tRu) and the deposition pressure. The formation of RuO2 phase is generally favorable at a higher pulsing time ratio (to2/tRu) and deposition pressure. It was also demonstrated that Ru single, the mixture phase of Ru and RuO2, and RuO2 single phase could be controllably grown with deposition condition. The RuO2 films deposited under optimized pulsing conditions showed resistivity of ~103 μΩ·cm, and a growth rate of ~0.056 nm/cycle with short incubation cycles of ~15 cycles. The diffusion barrier performance of ALD-RuO2 thin films against Ru is analyzed using XRD and electrical impedance analysis. According to both analyses, the non-barrier layer structure [ALD-Ru (50 nm)/Si] began to lose its stability by forming ruthenium silcides at 750 °C, while the structure with a barrier layer [ALD-Ru/ALD-RuO2 (5 nm)/Si] were stable up to 850 °C.