Robust Ta N x diffusion barrier for Cu-interconnect technology with subnanometer thickness by metal-organic plasma-enhanced atomic layer deposition J. Appl. Phys. 98, 014308 (2005); 10.1063/1.1935761 Growth of cubic-TaN thin films by plasma-enhanced atomic layer deposition J. Appl. Phys. 92, 7080 (2002); 10.1063/1.1519949Tantalum and tantalum nitride films deposited by electron cyclotron resonance sputtering as barriers to copper diffusion J.Thin films of inert, refractory materials are used in semiconductor interconnect applications as diffusion barriers, seed, and adhesion layers. A typical example is the use of a thin, conformal Ta or Ti/TiN films on the walls of a dielectric trench or via which reduces or eliminates out-diffusion of the primary conductor, usually Cu, into the dielectric. Atomic layer deposition is a known technique which is intrinsically conformal and is appropriate for this application. Plasma enhancement of the process allows deposition at significantly lower temperatures than conventional chemical vapor deposition, which is a requirement for low-k dielectrics. Tantalum films deposited at 25-400°C using ALD with a TaCl 5 precursor and atomic hydrogen as the reactive species at up to a rate of 1.67 Ang/cycle are amorphous, conformal, and show moderate or controllable levels of impurities; primarily oxygen and a small level of Cl. Similar results have been observed for Ti using TiCl 4 as a precursor. The process scales to manufacturing dimensions and applications and will facilitate the extension of interconnect technology beyond ͑below͒ 100 nm dimensions.

Chemical vapor deposition has been used to deposit titanium nitride (TIN) on silicon wafers at low pressures in a coldwall single-wafer reactor. Experiments are reported for pressures in the range of 100-300 mtorr and temperatures between 450~176with titanium tetrachloride and ammonia as reactants. Both hydrogen and nitrogen are evaluated as diluents. Deposition rates as high as 1000/~/min have been achieved. The chemical nature of the films are evaluated by Auger and RBS techniques, while the morphology is depicted by SEM. For the most part, the films are stoichiometric and contain small quantities of oxygen, chlorine, and hydrogen. Film resistivities as low as 50 ~ll-cm are reported. Behavior of the TiN film as a diffusion barrier between silicon (boron doped) and aluminum, at annealing temperatures up to 550~ is evaluated by measurements of contact resistance and diode leakage.

This paper reviews recent studies of the low-temperature chemical vapor deposition of titanium nitride thin films suitable for ULSI applications. In addition to the comprehensive studies available for films grown thermally from TiCl4 and NH3, films deposited from organometallic precursors are discussed, as well as those derived from plasma-enhanced techniques. Two applications of such films for ULSI are as a diffusion barrier between different conductors, and as a nucleation layer for CVD tungsten. Properties of LPCVD TiN for these applications, are covered including film conformality, effectiveness as a diffusion barrier, contact resistance, nucleation of tungsten, and the influence of any residual chlorine.

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