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

Abstract

We report the ALD RuO<inf>2</inf> process using a new Ru metalorganic precursor, tricarbonyl (trimethylenemethane) ruthenium [Ru(TMM)(CO)<inf>3</inf>], and molecular oxygen (O<inf>2</inf>) as a reactant at the relatively low temperature of 180 °C for a diffusion barrier application of Ru interconnect. RuO<inf>2</inf> thin films could be prepared by controlling the reactant and precursor pulsing time ratio (t<inf>o2</inf>/t<inf>Ru</inf>) and the deposition pressure. The formation of RuO<inf>2</inf> phase is generally favorable at a higher pulsing time ratio (t<inf>o2</inf>/t<inf>Ru</inf>) and deposition pressure. It was also demonstrated that Ru single, the mixture phase of Ru and RuO<inf>2</inf>, and RuO<inf>2</inf> single phase could be controllably grown with deposition condition. The RuO<inf>2</inf> 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-RuO<inf>2</inf> 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-RuO<inf>2</inf> (5 nm)/Si] were stable up to 850 °C.