La commune de Thio en Nouvelle-Calédonie connait une hypersédimentation et un engravement massif de ses cours d’eau. Selon les habitants, ces processus sont majoritairement associés à l’activité ...minière. Dans la région, les phénomènes météorologiques extrêmes et répétés depuis 1975 (cyclones, fortes pluies) contribuent à augmenter cette charge sédimentaire et ont grandement transformé tant l'environnement que les pratiques et savoirs locaux qui y sont liés. En conséquence, les inondations et la dégradation de certains lieux portent atteinte à la relation entre les habitants kanak des tribus de la montagne et leur environnement. Si le vocable de pollution a pris un sens spécifique localement et qu'une rupture dans les pratiques sociales et culturelles liées à la rivière est visible et exprimée, les savoirs écologiques continuent d'être construits par l'expérience répétée des lieux et se renouvellent dans ce contexte bouleversé par les événements climatiques et les choix d'aménagements des cours d'eau.
Thin Al2O3 layers were grown by atomic layer deposition using trimethylaluminum (TMA) and water as precursors on 1.2 nm thermal SiO2 and HF cleaned Si surfaces. The stoichiometry and the ...contamination (H, OH and C) of as-deposited and N2 annealed thick Al2O3 layers were characterized by secondary ion mass spectrometry (SIMS), elastic recoil detection analysis (ERDA) and X-ray photoelectron spectroscopy (XPS). We show a perturbed region (≈5 nm thick) at the Al2O3/Si interface by XPS and Auger electron spectrometry (AES). Post-deposition annealings induced important interface oxidation, Si atoms injection and SiO2/Al2O3 mixture whereas the initial interface was abrupt. Silicon oxidation before Al2O3 growth highly limits interfacial oxidation and improves interfacial quality. We proposed that OH groups may play a key role to explain silicon oxidation during post-deposition annealings in inert ambience with low oxygen contamination levels.
Advanced Cu interconnects using air gaps Gosset, L.G.; Farcy, A.; de Pontcharra, J. ...
Microelectronic engineering,
12/2005, Volume:
82, Issue:
3
Journal Article, Conference Proceeding
Peer reviewed
The integration of air gaps for advanced Cu interconnects is mandatory to achieve the performances required for high performance integrated circuits (ICs). The interest of their introduction as a ...function of the chosen architecture, i.e. hybrid (i.e. air cavities at metal levels with a low-K material at via level) or full homogenous air gaps with an effective relative constant close to 1, is discussed in terms of signal propagation requirements for delay, crosstalk and delay increased by crosstalk. The different approaches currently investigated within the microelectronic community are classified into two main categories depending on the use of a non-conformal plasma enhanced chemical vapor deposition (PE-CVD) including innovative alternatives or the removal of a sacrificial material during a specific technological operation. While the first technique,, faces many integration issues that can be alleviated at the detriment of the global performances, the second approach may be all the more promising as well-known materials such as USG or SiOC are now introduced as sacrificial dielectrics as an alternative to degradable polymers. However, it is evidenced from published results that air gaps integration maturity permits their introduction for the 32
nm technology node high performance ICs.
Self-aligned barriers have been widely investigated in the replacement of standard PECVD dielectric liners to decrease coupling capacitance. As an alternative to CVD or electroless approaches, a two ...step process based on the modification of the Cu surface is proposed. This technique consists first in enriching Cu surface with Si atoms followed by a nitridation step to complete the so called CuSiN self-aligned barrier. In this paper, the silicidation mechanism is described and the crucial role of the nitridation step is demonstrated in terms of barrier stability under electrical stress. CuSiN efficiency against Cu diffusion and oxidation is also evidenced. Compared to a standard SiCN barrier, CuSiN self-aligned barriers revealed a gain of at least 3 decades in time-dependent dielectric breakdown lifetime and up to 7% decrease in intra-level coupling capacitance.
The formation of air gaps by means of a non-conformal chemical vapor deposition (CVD) on patterned wafers was successfully demonstrated using SiOC (
K=2.9) as inter-level metal dielectric. This paper ...presents the results on physical characterization and electrical performance evaluation of integrated SiOC air gaps in a three-metal level Cu/SiOC interconnect module. The influence of the air gaps shape on parasitic coupling capacitance between copper lines was also discussed in accordance with mask design rules and processing steps.
Device performance for 65 nm node CMOS technology and beyond will require the integration of porous ultra-low-k materials with dielectric constant below 2.5, in order to reduce coupling effects ...between interconnect lines. This paper discusses the process development, the characterization (chemical composition and structure, porosity, mechanical and electrical characteristics), and the integration of a porous chemical vapor deposition dielectric with a dielectric constant lower than 2.5. An optimized material, characterized by a hardness of about 1 GPa in association with a porosity of 41% and a mean pore radius of 1.9 nm, was successfully integrated using a dual damascene architecture scheme in copper interconnects.
The formation of intra metal level “air cavities” using a sacrificial oxide in a Dual Damascene copper interconnect structure was investigated for different HF solutions. In this approach, HF ...solutions diffuse throughout a porous polymer membrane to realise the cavities within the interconnect stack. Results were discussed in terms of silicon dioxide etching rate, vertical and lateral diffusion behaviour in the porous membrane for three different chemistries. The formation of two oxide levels in the same operation with very short process times (in the range of few minutes) was demonstrated. Main limitations on the current architecture have been evaluated in terms of copper and diffusion barrier integrity and alternative solutions have been proposed to overcome them.
Of great interest for sub-65
nm interconnect technologies, low-
k barriers are potentially sensitive to Cu diffusion and oxygen-based contamination, respectively leading to short circuits and to ...performance degradations of Cu lines. Two characterization methods were developed to evaluate these potential weaknesses, (i) liquid phase decomposition (LPD), coupled to Cu contamination analysis in a sacrificial silicon oxide layer, and (ii) nondestructive reflectivity. LPD was shown to detect defects on the Cu surface or in the barrier itself that cannot be investigated with local analysis such as SIMS probe. Results evidenced the degradation of barrier efficiency against Cu diffusion with the low-
k barrier thickness reduction. On the opposite, reflectivity measurements showed that hermeticity of these barriers to oxygen diffusion is not critical for most of the dielectric barriers with
k-value higher than 4. The two techniques developed in this study will be useful to evaluate advanced low-
k barriers.
Self-aligned barriers on copper are widely investigated as a promising solution to replace standard PECVD dielectric barriers for the 65 nm technology node and beyond. As an alternative to ...electroless or selective CVD deposition, CuSiN barriers, based on the controlled modification of copper surface using a sequential exposure to SiH4 flow and NH3 plasma has been proposed. This paper focuses on the key role played by SiH4 flow on the physical and electrical barrier characteristics and more particularly on the existing relation between silane flow and Ta atoms from the TaN/Ta metal barrier. Non-regular defects observed after electromigration tests were not only attributed to intentionally modified copper surface but also to the presence of Ta atoms that diffused through copper lines during the tests.
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