Atomic layer deposition of barriers for interconnect

Ternary tungsten carbo nitride WCN films and titanium nitride TiN films were deposited with atomic layer deposition as diffusion barrier materials for copper metallisation. The growth behaviour on different substrates and surface closure was studied by Rutherford backscattering spectroscopy (RBS). It was demonstrated that the initial surface condition and interaction of the ALD precursors with the substrate material play a major role in the nucleation and the final growth characteristics of the film. Large irregular TiN crystals were observed on chemical vapour deposited SiCO:H films due to growth initiation problems. Additionally, the growth of TiN on copper caused severe pitting and unacceptable copper contamination of the TiN barrier. In contrast the tungsten carbonitride deposited films were much more uniform and showed better compatibility with different substrates including Cu, SiO₂, SiN, poly aryl ether, MSQ, HSQ, and CVD SiCO:H type low-k materials. However, atomic layer deposition onto low-k dielectric materials with an interconnected pore structure results in penetration of the ALD precursors inside the pores and deposition inside the dielectric material. A pore sealing approach by plasma treatment is presented for CVD SiCO:H low-k materials.