Barrières métalliques auto-alignées déposées par voie electroless pour la fabrication des interconnexions au nœud 32 nm (étude electrochimique, propriétés physico-chimiques et enjeux technologiques )

l' utilisation du cuivre comme métal conducteur dans les interconnexions a entraîné l'apparition de nouvelles solutions technologiques. Afin de d'empêcher la 'fusion du cuivre dans le matériau diélectrique interligne, il est nécessaire d'encapsuler les interconnexions par une couche barrière. Les barrières !Iectriques actuelles en SiCCN) contribuent à l'augmentation des phénomènes de couplage capacitifs, et les phénomène d'électromigration sont connus ,ur apparaître au niveau de l'interface cuivre - barrière. Afin de limiter ces phénomènes, une solution consiste à déposer sélectivement à la surface des nes de cuivre des barrières métalliques par voie electroless. Différents procédés de dépôts electroless conduisant à des dépôts d'alliages de cobalt IWP(B) et de nickel NiMoPB sont étudiés en équipement industriel pour plaques de 300 mm. Deux de ces barrières sont déposées après activation de la rface du substrat en cuivre par un dépôt de palladium, les trois autres dites auto-initiées étant déposées directement à la surface du cuivre. L'étude !ctrochimique des réactions d'oxydoréduction qui ont lieu durant le dépôt electroless met en évidence que le dépôt de ces alliages est un dépôt anormal tié par la présence de Had5 à la surface du substrat. Les cinétiques de dépôt diffèrent en fonction de l'état de surface du substrat en cuivre: elles sont plus pides sur motifs, et sont favorisée sur les grains de cuivre d'orientation (111). L'information cristalline du cuivre semble être conservée dans la barrière ~tallique. Par ailleurs, la composition des films métalliques joue sur leur microstructure: une concentration plus importante en métal réfractaire diminue Jr cristallinité. Des premières analyses de leurs propriétés en tant que barrières à la diffusion du cuivre indiquent que leurs performances sont moindres le celle de la barrière diélectrique actuelle. D'un point de vue électrique, les procédés avec activation du substrat en cuivre par dépôt de palladium éservent les propriétés d'isolation des lignes de cuivre mais dégradent légèrement leurs propriétés de conduction, à l'inverse des procédés auto-initiés. Les >Is de résistance à l'électromigration effectués avec le procédé CoWP Enthone (avec activation) montrent que l'intégration des barrières métalliques posées par voie electroless améliore la durée de vie des interconnexions d'un facteur 10000 dans les conditions standard d'utilisation, en modifiant la :alisation du mécanisme de dégradation des interconnexions par les phénomènes d'électromiaration.The use of copper as a conductive metal for the fabrication of advanced interconnects has driven the emergence of innovative technological solutions. To event copper diffusion into the surrounding dielectric material, it is mandatory to encapsulate copper lines with a barrier layer. Currently, the SiC(N) materials used for this application contribute to capacitive coupling, and electromigration failure proceeds through this copper - barrier interface. To Ii mit ese phenomena, a possible solution would be to selectively deposit metallic barriers on top of the copper lines, which can be achieved by electroless position. Several electroless processes are investigated or 300 mm wafer processing using an industrial deposition equipment, which lead to the selective position of cobalt-based CoWP(B) and nickel-based NiMoPB alloys. Among them, two are deposited using an intermediate activation of the metallic surfacepalladium deposition. The three others named self-initiated are directly deposited onto copper. The electrochemical study of the redox reactions that cur during deposition indicates that this anormal deposition is initiated by the presence of adsorbed Hads at the copper surface. Reaction kinetics depend 1 the type of surface to be plated: deposition proceeds faster on features as compared to fullsheet, and seems to be enhanced on (111) oriented copper ains. Also, the microstructure of the film is conditioned by its composition: a higher content in refractory metalleads to more amorphous deposits. :ntative characterization of their properties as diffusion barriers suggest that they do not offer he same level of performances as conventional dielectric fers. Electrical tests show that the palladium activated processes preserve insulation performances, but slightly increase line resistance. The reverse Ihaviour is observed for self-initiated processes. Electromigration tests using the activated CoWP process from Enthone establish that these electrolessly lposited films drastically improve lifetime of the structures. Under working conditions, this lifetime is multiplied by a factor of 10000, due to the different !ctromigration failure mechanism induced bv these barri ers.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Physical investigation of the impact of electrolessly deposited self-aligned caps on insulation of copper interconnects

International audienceWith the miniaturization of ULSI circuits and the associated increase of current density up to several MA/cm2, copper interconnects are facing electromigration issues at the top interface with the dielectric capping layer SiC(N). A promising solution is to insert selectively on top of copper lines a CoWP metallic self-aligned encapsulation layer, deposited using a wet electroless process. We study the impact of this process on electrical line insulation as a function of cap thickness at the 65 nm technology node and we investigate the physical origin of leakage currents. Below a critical thickness, only a slight leakage current increase of less than one decade is observed, remaining within the specification for self-aligned capping layer processes. Above this critical thickness, large leakage currents are generated due to the combined effect of lateral growth and the presence of parasitic redeposited nodules. We show that a simple phenomenological model allows to reproduce the experimental data, to assess quantitatively the contribution of parasitic defects, and to predict that the self-aligned barrier technology should be extendible up to the 32 nm node, provided that a thin cap layer of less than 8 nm is used

Electroless deposition of CoWP: Material characterization and process optimization on 300 mm wafers

International audienceThe use of copper as a metal for interconnections has driven the apparition of new technological solutions. Selective barriers against copper diffusion deposited by electroless reaction bring interests in term of electromigration. In this article, CoWP electroless barriers deposited in a 300 mm Semitool Raider equipment are studied. Good uniformity for a standard thickness of 15 nm is demonstrated. Different growth rates of the barrier as a function of copper grain orientation are observed. The composition of the barrier is constant throughout the film. The deposition is selective, but corrosion phenomena and a superficial metallic contamination on the interline dielectric are revealed. The selectivity of the process is confirmed electrically for 12 nm thick barriers. The impact of copper corrosion on line resistance is addressed through preclean optimization

Electroless deposition of Co-based barriers: selectivity, corrosion and growth properties.

International audienceElcctroless metallic caps are convincing alternatives to standard SiC(N) barriers for the 45 nm technology node and beyond to improve electromigration resistance and limit the dielectric constant of the structures. In this work, particular emphasis is put on possible selectivity issues, corrosion of the copper lines and nucleation/growth properties for two processes (Pd-activated Co\VP and Pd-free CoWB) deprniited in an industrial 300 mm equipment Co\VP process exhibits promising results for 12 nm nominal thickness. For both processes, the control of the preclean step seems to be fundamental to limit copper corrosion. Under optimal conditions, line resistance increase is limited to less than 3 %

Electroless deposition of NiMoPB : electrical performances and material properties

International audienceElectroless deposited Co-based caps are convicing alternatives to standard SiC(N) barriers for the 45 nm node and beyond to improve electromigration resistance and limit the dielectric constant of the structures. In this work, growth kinetics, process selectivity, microstructure and composition of an alternative self-initiated NiMoPB cap are reported for 300 mm fabrication. This process is very selective, and does not modify the electrical performances of the structures. The film presents very promising barrier properties against copper diffusion, due to a high quantity of phosphorus and refractory metal in the fihn

Thin film characterization by total reflection x-ray fluorescence

International audienceSensitive and accurate characterization of films thinner than a few nm used in nanoelectronics represents a challenge for many conventional production metrology tools. With capabilities in the 1010 at/cm2, methods usually dedicated to contamination analysis appear promising, especially Total-reflection X-Ray Fluorescence (TXRF). This study shows that under usual configuration for contamination analysis, with incident angle smaller than the critical angle of the substrate, TXRF signal saturation occurs very rapidly for dense films (below 0.5 nm for HfO2 films on Si wafers using a 9.67 keV excitation at 0.5°). Increasing the incident angle, the range of linear results can be extended, but on the other hand, the TXRF sensitivity is degraded because of a strong increase of the measurement dead time. On HfO2 films grown on Si wafers, an incident angle of 0.32° corresponding to a dead time of 95% was used to achieve linear analysis up to 2 nm. Composition analysis by TXRF, and especially the detection of minor elements into thin films, requires the use of a specific incident angle to optimize sensitivity. Although quantitative analyses might require specific calibration, this work shows on Co–based films that the ratio between minor elements (W, P, Mo) and Co taking into account their relative sensitivity factors is a good direct reading of the compositio