Showing papers by "Dominique Drouin published in 2013"

A damascene platform for controlled ultra-thin nanowire fabrication.

Abstract: This paper presents a damascene process for the fabrication of titanium micro/nanostructures and nanowires with adjustable thickness down to 2?nm. Their depth is precisely controlled by chemical?mechanical planarization together with in-process electrical characterization. The latter, in combination with a model of the titanium resistivity versus thickness, allows control of the metal line depth in the nanometer range. In summary, we have developed a planarization end point detection method for metal nanostructures. In addition, the model adopted covers geometrical influences like oxidation and ageing. The fabricated titanium nanowire test structures have a thickness ranging from 2 to 25?nm and a width ranging between 15 and 230?nm.

Fabrication of p-type porous GaN on silicon and epitaxial GaN

Abstract: Porous GaN layers are grown on silicon from gold or platinum catalyst seed layers, and self-catalyzed on epitaxial GaN films on sapphire. Using a Mg-based precursor, we demonstrate p-type doping of the porous GaN. Electrical measurements for p-type GaN on Si show Ohmic and Schottky behavior from gold and platinum seeded GaN, respectively. Ohmicity is attributed to the formation of a Ga2Au intermetallic. Porous p-type GaN was also achieved on epitaxial n-GaN on sapphire, and transport measurements confirm a p-n junction commensurate with a doping density of ∼1018 cm−3. Photoluminescence and cathodoluminescence confirm emission from Mg-acceptors in porous p-type GaN.

Interactions between Variable Frequency Microwave Underfill Processing and High Performance Packaging Materials

Abstract: Variable frequency microwave (VFM) has been recently proposed as an alternative underfill curing method that provides flip chip package warpage improvement as well as potential underfill cure time reductions. The current paper outlines how such advantages in VFM processing of underfill can be compromised when applied to high performance organic packages. VFM recipes for three underfill materials were developed by performing several VFM curing runs followed by curing rate measurements using the differential scanning calorimetry method. The VFM curing rate was seen to strongly dependent upon the underfill chemistry. By testing flip chip parts that comprised large and high-end substrates, we showed that the underfill material has negligible impact on VFM warpage with the major cause attributed to the coefficient of thermal expansion mismatch between the die and the substrate. Comparison between the convection and the VFM methods indicated two warpage tendencies that depended upon the VFM curing temperature. ...

Metal Catalyzed Porous n-type GaN Layers: Low Resistivity Ohmic Contacting and Single-Step MgO/GaN Diode Formation

Abstract: gas through chemical vapor deposition, intermetallic metal-Ga alloys form at the GaN-metal interface, allowing vapour-solid-solid seeding and subsequent growth of porous GaN. Current-voltage and capacitance-voltage measurements confirm that the intermetallic seed layers prevent interface oxidation and give a high-quality reduced workfunction contact that allows exceptionally low contact resistivity. Additionally, the simultaneous formation of a lower workfunction intermetallic permits ohmic electron transport to n-type GaN grown using high workfunction metals that be st catalyze the formation of porous GaN layers and may be employed to seed and ohmically contact a range of III-N compounds and alloys for broadband absorption and emission. Additionally, we show how a porous Ga N rectifying diode can be formed by oxidatively crystallizing Mg typically employed for p-doping GaN, as a layer formed under porous structure resulting in a high-k polycrystalline MgO dielectric. Introduction Gallium nitride (GaN) is considered one of the most important wide band-gap semiconductors for a number of applications in electronics and optoelectronics (1). In its porous form, GaN has received particular in terest in the last decade due to beneficial optical and electronic properties for gas sensors with high sensitivity (2), and light-emitting diodes (LEDs) with high light extraction efficiency (3). Porous GaN has been typically fabricated by (photo)electrochemical and chemical etching methods (4-7), giving textured surfaces as a result of pore coalescence and variations in etch rates for extended etching times. We produced porous GaN through the direct reaction of metallic Ga with NH

Study of influential parameters for lead-free flip chip solder joint cracking

Abstract: In this work, we investigated the flip chip lead-free solder joint cracking phenomenon. A study on the occurrence and severity of solder joint cracking before the encapsulation operation across several device technologies enabled the identification of the dominant parameters. The respective influence of CJ reflow profile, solder joint density in chip corners, substrate core thickness and the solder voiding are discussed with respect to this phenomenon. The CJ reflow profile was found to be the most significant parameter in this study. The influence of the CJ reflow profile is described with respect to measured chip warpage reduction and frequency of solder joint cracking. Amongst the more secondary relationships, a comparison between various solder joint densities in chip corners revealed that higher solder joint density exhibits an improved resistance to crack occurrence and propagation. In terms of substrate core thickness, coreless packages have shown to be more sensitive than packages with cored substrates to mechanical stresses and vibrations that can induce cracking. Finally, the presence of voids in solder was found to be an aggravating parameter based predominantly on its effect on cracking severity. These relationships are discussed in detail along with hypotheses to support same.

Effect of illumination on the electron transport mechanisms in Silicon nanocrystal-based nanopixels

Abstract: In this paper, we present an analysis of conduction in silicon nanocrystals (nc-Si) of small area nanopixels in dark conditions and under illumination. The photosensitive layer of the analyzed devices is mad up a small number of (nc-Si) embedded in SiO2. The interface between the oxide and the silicon substrate is shown to play a significant role in the conduction process: we observed that the presence of (nc-Si) situated inside the oxide, at some angstroms from the interface with the active region, induced discrete variations in the current. In dark conditions the transport of electrons is dominated by trap-assisted mechanisms (Poole-Frenkel, Hopping) at low electric fields and a Fowler-Nordheim mechanism at high electric fields. Under illumination, a new generation-recombination contribution is observed. This mechanism has been carefully studied by Random Telegraph Signal (RTS) measurements. This work shows that the photo-induced current fluctuations (RTS) could be related to the interaction between single photogenerated charges.

Molecule sensor that can be integrated into a mobile terminal

Abstract: The present invention concerns a device for detecting target molecules comprising a source (21) and a drain (22) extending on a substrate (10), and an island (23) between the source (21) and the drain (22), the island (23) forming a tunnel junction between the source (21) and the drain (22), characterised in that the device further comprises a nano-object (40) extending at right angles to the island (23), the nano-object (40) being functionalised to sense at least one target molecule.