Study on preparation and conductivity of Ru thin films deposited by atomic layer deposition

With the ongoing miniaturization of device sizes inintegrated circuit component, traditional copper (Cu) interconnects encounter performance limitations below the 5 nm technology node due to the size-induced increase in resistivity. This challenge highlights the need for novel interconnect materials and fabrication techniques. This study utilized ALD with a Ru(EtCp)₂/O₂ system on SiO₂ substrates to examine the influence of optimizing critical process parameters on ruthenium (Ru) film growth and conductive network formation. These parameter include ALD cycles, precursor/oxygen pulse durations, and deposition temperature. The objective was to provide experimental insights for refining the ALD process to produce high-conductivity Ru interconnect films. Results indicated that Ru films deposited with fewer than 200 ALD cycles exhibited discrete island-like structures. A continuous conductive network formed when the cycle count reached 500. The metallic Ru film purity exceeded 90%. On SiO₂ substrates, the deposited Ru film thickness was 19.7 nm, with a corresponding resistivity of 25.6 μΩ·cm. Optimizing the precursor and oxygen pulse durations to 5 s and 10 s, respectively, increased the deposition rate to 0.510 Å/cycle. Temperature regulation, which influenced grain boundary diffusion, revealed that at 325 ℃, the conductive network remained stable, yielding a sheet resistance of 18 Ω. In contrast, at 350 ℃, thermal stress induced grain coarsening and network fragmentation, increasing the sheet resistance to 59 Ω.