Time-to-failure analysis of 5 nm amorphous Ru(P) as a copper diffusion barrier

Abstract

Evaluation of chemical vapor deposited amorphous ruthenium–phosphorous alloy as a copper interconnect diffusion barrier is reported. Approximately 5 nm-thick Ru(P) and TaN films in Cu/Ru(P)/SiO 2/p-Si and Cu/TaN/SiO 2/p-Si stacks are subjected to bias-temperature stress at electric fields from 2.0 MV/cm to 4.0 MV/cm and temperatures from 200 °C to 300 °C. Time-to-failure measurements suggest that chemical vapor deposited Ru(P) is comparable to physical vapor deposited TaN in preventing Cu diffusion. The activation energy of failure for stacks using Ru(P) as a liner is determined to be 1.83 eV in the absence of an electric field. Multiple models of dielectric failure, including the E and Schottky-type √ E models indicate that Ru(P) is acceptable for use as a diffusion barrier at conditions likely in future technology generations.