ESD and ALD Depositions of Ta2O5 Thin Films Investigated as Barriers to Copper Diffusion for Advanced Metallization

Abstract

Deposits of tantalum oxide thin films on silicon wafer substrates by electrostatic spray deposition (ESD) and atomic layer deposition (ALD) have been studied for their integration as barriers to copper diffusion in interconnect technologies. In the case of ESD, both precursor solution and deposition time have been optimized in order to produce homogeneous films of lowest thickness, as required for applications. As-deposited films were amorphous; their crystallization after annealing treatment at was studied by transmission electron microscopy. Depending on the thermal treatment, the crystallization occurs with the formation of monoclinic phase either pure or mixed with a trigonal phase. In the case of ALD, thin-film deposits were optimized as a function of the different parameters of temperature, number of cycles, and tantalum precursor pulse times. As-deposited films were also amorphous but were crystallized in a pure monoclinic phase after annealing treatment at . Copper diffusion was tested with high thermal budgets through thin films of thickness using X-ray photoelectron spectroscopy. Barrier-diffusion failures were detected in these films at . The conformity of such films was examined from deposits realized on patterned substrates.