Few Graphene layer/Carbon-Nanotube composite Grown at CMOS-compatible Temperature

We investigate the growth of the recently demonstrated composite material composed of vertically aligned carbon nanotubes capped by few graphene layers. We show that the carbon nanotubes grow epitaxially under the few graphene layers. By using a catalyst and gaseous carbon precursor different from those used originally we establish that such unconventional growth mode is not specific to a precise choice of catalyst-precursor couple. Furthermore, the composite can be grown using catalyst and temperatures compatible with CMOS processing (T < 450\degree C).Comment: 4 pages, 4 figure

Catalyst preparation for CMOS-compatible silicon nanowire synthesis

Metallic contamination was key to the discovery of semiconductor nanowires, but today it stands in the way of their adoption by the semiconductor industry. This is because many of the metallic catalysts required for nanowire growth are not compatible with standard CMOS (complementary metal oxide semiconductor) fabrication processes. Nanowire synthesis with those metals which are CMOS compatible, such as aluminium and copper, necessitate temperatures higher than 450 C, which is the maximum temperature allowed in CMOS processing. Here, we demonstrate that the synthesis temperature of silicon nanowires using copper based catalysts is limited by catalyst preparation. We show that the appropriate catalyst can be produced by chemical means at temperatures as low as 400 C. This is achieved by oxidizing the catalyst precursor, contradicting the accepted wisdom that oxygen prevents metal-catalyzed nanowire growth. By simultaneously solving material compatibility and temperature issues, this catalyst synthesis could represent an important step towards real-world applications of semiconductor nanowires.Comment: Supplementary video can be downloaded on Nature Nanotechnology websit

Toward optimized SiOCH films for BTEX detection Impact of chemical composition on toluene adsorption

International audienceVolatile Organic Compounds are a cause of concern for human health. It is particularly the case for BTEX compounds (Benzene, Toluene, Ethylbenzene and Xylenes). Gravimetric sensors are good candidates for their detection but they have to be functionalized by a sensitive film to become active. In this work, organosilicate thin films (SiOCH) deposited by plasma enhanced chemical vapor deposition are investigated. This work aims at understanding the role of their chemical composition on gas adsorption and to propose an optimized material for BTEX detection. Through the synthesis and characterization of various SiOCH thin films, the role of hydrophobicity, carbon content and specific chemical bonding is highlighted. This led to an optimized film presenting both high affinity (partition coefficient toward toluene higher than 15000) and rapid temporal response

Porous extreme low κκ (ELκκ) dielectrics using a PECVD porogen approach

International audienceThe introduction of new dielectrics into silicon chip interconnection technology, to improve the electrical performance of ultra large-scale integration (ULSI), is marked by continuous revisions to meet the International Technology Roadmap for Semiconductors (ITRS) projection. Amorphous a-SiOC:H ($k$=2.9) deposited by plasma-enhanced chemical vapor deposition (PECVD) from linear precursors is now in scale up towards production. Using other precursors like cyclic siloxanes,$k$ value is reduced to 2.5 at least. The main way to reduce the dielectric constant is to introduce porosity into the film. In this work, a two-step porogen approach is followed to perform extreme low (EL) $κ$($k$<2.5) deposition. Firstly, a dual-phase thin film is deposited by PECVD using two advanced precursors: decamethylcyclopentasiloxane (D5) to create a a-SiOC:H matrix and a sacrificial organic precursor. Within the matrix, the organic precursor generates organic inclusions. In a second step, the organic phase is removed by a suitable curing to induce porosity. Various types of organic precursors are investigated and thin films are then characterized. Incorporation and removal of organic molecules from a-SiOC:H material are closely studied using infrared spectroscopy. Using cyclohexene oxide as organic precursor (porogen), κ value of the porous dielectric is measured at 2.2. Nitrogen adsorption isotherms measurements prove the cured material porosity. This work clearly demonstrates the ability of achieving an EL with a PECVD porogen approach using D5 as matrix precursor and new organic precursors as porogen

Porous extreme low k (ELK) dielectrics using a PECVD porogen approach

International audienc

Development of a stretchable and removable electrical interconnection solution for ultra-thin electronic components

International audienceCurrently, the solutions for interconnecting electronic components with their active face facing on substrates are based on metallic soldering. The mechanical contacts are therefore rigid. In order to enhance the reliability of the bonding, underfill is usually used to redistribute the thermo-mechanical stress created by the Coefficient of Thermal Expansion (CTE) mismatch between the silicon chip and substrate. Underfill is done with epoxy resins containing silica fillers (SiO2). As a result, the removal of components is no longer possible. Moreover, this solution is not suitable for devices integrating ultra-thin silicon components (<100 µm) hybridized on flexible substrates that may be subject to deformation. This is the case, for example, of medical "patches" worn on the person and continuously solicited. Indeed, the rigid contact points are likely to break. To address this issue, we are developing a thin anisotropic conductive and stretchable adhesive film inspired by the adhesion of the gecko.. Thanks to the microstructuration of its toes involving about 1 million setae, the gecko can develop a large contact surface and thus a large force of attraction by the multiplication of van der Waals interactions (1). In this work, this "dry adhesion" based on the principle of "contact splitting", was implemented in order to improve the adhesion of a flexible interconnection. For this purpose, the surface of a polydimethylsiloxane (PDMS) film was structured with micrometric mushroom-shaped patterns known to be the most efficient form of contact (2,3). To this end, silicon molds with varying mushroom geometries were used to shape the PDMS (with different cap and pillar diameters) and the adhesion force microstructured films were assessed (shear and pull-off experiments). To make these films locally conductive through the thickness, a conductive composite was prepared and locally deposited in the mold. One approach we investigated, was using a screen-printing mask. This approach has been implemented and characterized using electrical tests (I-V measurements) in order to select the most suitable films to realize a flexible interconnection

Development of a stretchable and removable electrical interconnection solution for ultra-thin electronic components

International audienceCurrently, the solutions for interconnecting electronic components with their active face facing on substrates are based on metallic soldering. The mechanical contacts are therefore rigid. In order to enhance the reliability of the bonding, underfill is usually used to redistribute the thermo-mechanical stress created by the Coefficient of Thermal Expansion (CTE) mismatch between the silicon chip and substrate. Underfill is done with epoxy resins containing silica fillers (SiO2). As a result, the removal of components is no longer possible. Moreover, this solution is not suitable for devices integrating ultra-thin silicon components (<100 µm) hybridized on flexible substrates that may be subject to deformation. This is the case, for example, of medical "patches" worn on the person and continuously solicited. Indeed, the rigid contact points are likely to break. To address this issue, we are developing a thin anisotropic conductive and stretchable adhesive film inspired by the adhesion of the gecko.. Thanks to the microstructuration of its toes involving about 1 million setae, the gecko can develop a large contact surface and thus a large force of attraction by the multiplication of van der Waals interactions (1). In this work, this "dry adhesion" based on the principle of "contact splitting", was implemented in order to improve the adhesion of a flexible interconnection. For this purpose, the surface of a polydimethylsiloxane (PDMS) film was structured with micrometric mushroom-shaped patterns known to be the most efficient form of contact (2,3). To this end, silicon molds with varying mushroom geometries were used to shape the PDMS (with different cap and pillar diameters) and the adhesion force microstructured films were assessed (shear and pull-off experiments). To make these films locally conductive through the thickness, a conductive composite was prepared and locally deposited in the mold. One approach we investigated, was using a screen-printing mask. This approach has been implemented and characterized using electrical tests (I-V measurements) in order to select the most suitable films to realize a flexible interconnection

Porous SiOCH Thin Films Obtained by Foaming

Porous organosilicate thin films (SiOCH) deposited by plasma-enhanced chemical vapor deposition (PECVD) are used as dielectric layers in advanced microelectronic interconnections and as chemical layers in chemical sensors and biosensors. One challenge is to increase the porosity in these films, the classical method being limited to porosity rate close to 50%. In this paper, we report an innovative and simple strategy to perform highly nanoporous SiOCH thin films without the use of any templates or external blowing agents. This approach uses a SiOCH deposited by PECVD (without any porogens) intentionally covered by a dense crust. The porosity generation is obtained through an ultraviolet (UV)-assisted thermal annealing of the stack. The highest porosities ever demonstrated for SiOCH PECVD thin films are obtained (porosity close to 65%). The impact of different process parameters (choice of precursor, deposition, and annealing conditions) on the creation of porosity is studied. The porosity introduction with this original method can be related to a foaming mechanism: a gas is produced inside the film during the UV-assisted curing which causes a film expansion and allow the creation of porosity

Hydrophobic mesostructured organosilica-based thin films with tunable closed mesoporosity

International audienc