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The deposition of homogeneous thin films on porous substrates has been investigated. The thin film deposition of Ta(N) by physical vapor deposition on porous films with different average pore sizes and material compositions has been studied. The continuity of Ta(N) films on top of porous low-k dielectrics is evaluated by means of ellipsometric porosimetry combined with sheet resistance and atomic force microscopy measurements. Interface reactions are analyzed by x-ray photoelectron spectroscopy profiling. It has been observed that the minimal Ta(N) thickness required to obtain a continuous metal layer on top of the porous film depends, on the one hand, on the porosity and pore size and, on the other hand, on the chemical interaction of the thin film with the porous substrate. The sealing of pores is favored by the presence of carbon in the dielectric matrix. This is explained through a mechanism of local enhancement of the degree of crosslinking in the dielectric matrix, catalyzed by Ta. [ABSTRACT FROM AUTHOR]

Titanium nitride (TiN) is widely used in metal gate applications. Exposing TiN to a Cl2/HBr plasma results in pronounced surface roughness that can be easily characterized by ellipsometry. The ellipsometric angle Δ is proportional to the roughness if the roughness does not exceed 30 nm. It is possible to plot a "roughness diagram" where a border can be drawn between the smooth and rough etch surfaces depending on the etch conditions. This diagram could be used for gate-etch process optimization. In our case, the roughness could be overcome by increasing HBr content and/or substrate bias during the etching. [ABSTRACT FROM AUTHOR]

Abstract: The modification of a SiOCH based low-k by oxygen plasma in a transformer coupled plasma (TCP) is reported. Modification of the film is studied as function of TCP power and time. Spectroscopic ellipsometry (SE) and Fourier transformed infrared absorption spectroscopy (FTIR) measurements are used for characterization. Both techniques show that the modification (damage) depth increases with increasing TCP power. Optical emission spectroscopy (OES) indicates that adding TCP power increases the O/O2 + ratio in the plasma. By means of FTIR and OES, evidence is found for the removal of hydrogen and carbon from the low-k during plasma exposure. Using a two-layer SE fitting model, and no TCP power a refractive index (RI) of 1.44 for the chemically altered top layer was found. This RI decreases with TCP power. Presumably, at increased TCP power, relatively more radicals are generated and they penetrate more easily because of a less dense top layer. [Copyright &y& Elsevier]

Implementation of Cu/low-k in advanced interconnections requires a diffusion barrier to prevent copper penetration in low-k dielectrics. The barrier should be continuous to prevent copper diffusion and thin enough to keep interconnection line resistance low. Deposition of a diffusion barrier becomes an issue when porous low-k dielectrics are used. We developed a Monte Carlo simulation model to describe deposition of a diffusion barrier on a porous low-k film. The model provided explanation for the sealing behavior of different porous film by TaN diffusion barrier. Previously we have shown that TaN barrier integrity depends on chemical nature of the substrate rather than on porous structure: the same barrier can be continuous on oxycarbide (SiOCH) but non-continuous on HSQ (hydrogen silsesquioxane) although porous structures of the two films are similar. Using the model, we show that surface diffusion of TaN during deposition plays a key role in continuous barrier formation. Presence of carbon suppresses TaN diffusion (probably by TaC formation) and the barrier does not penetrate deep into the film forming a continuous layer on the top surface. The model is also able to predict sealing behavior for different porous low-k films with different porosity/pore sizes. [Copyright &y& Elsevier]