Factors affecting an efficient sealing of porous low-k dielectrics by physical vapor deposition Ta(N) thin films

Abstract

The deposition of homogeneous thin films on porous substrates has been investigated. The thin film deposition of Ta͑N͒ by physical vapor deposition on porous films with different average pore sizes and material compositions has been studied. The continuity of Ta͑N͒ 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 Ta͑N͒ 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.

Toward Successful Integration of Porous Low-k Materials: Strategies Addressing Plasma Damage

“…While it is relatively easy to deposit thin liners on low porosity dielectric materials, especially by ALD, it becomes a lot more challenging when the pore size is on the same order or bigger than the precursor molecules. In that case, a couple of major drawbacks arise: i) thicker liners are needed to form pin-holes free barriers, 102,104,105 and ii) the precursor molecules deposit inside the pores before a continuous layer is actually formed on the material surface. 106 Even though the latter could help ensure a good adhesion between the two materials, it should be avoided (or limited to a few nanometers at the interface) to keep the increase in k effective at a minimum.…”

Integration of Low‐ k Dielectric Films in Damascene Processes

“…The sealing effi ciency of thin barrier layers depends however not only on the porosity [117] and pore size [118,122], but also on the surface composition of the dielectric [119]. A strong correlation was found between the carbon content of the dielectric and the sealing effi ciency of PVD Ta(N) fi lms on porous low-k fi lms.…”

Low‐kMaterials: Recent Advances

“…For maximum effectiveness, this barrier layer needs to be continuous and without defects and pinholes. For highly porous ILDs, this requires the use of relatively thick barrier layers to seal off the pores, preventing Cu intrusion into the ILD, as shown in Figure 1.3 (h) [48,49]. However, as line and via dimensions shrink in accordance with future technology nodes, thinner barrier layers are needed to maintain or improve electrical performance.…”

“…The first pathway interposes a thin, continuous layer between the porous ILD and the barrier metal [90,91]. This material could be deposited by various means and both organic and inorganic candidates have been proposed [25,48,49,[92][93][94][95]. Furthermore, since this material contributes to the overall dielectric constant, candidates with relatively low k values are preferred.…”