Here, silicon oxide was formed in a U-shaped trench of a power metal-oxide semiconductor field-effect transistor device by various processes. One SiO₂ formation process was performed in multiple steps to create a low-defect Si-SiO₂ interface, where first a thin initial oxide was grown by thermal oxidation followed by the deposition of a much thicker oxide layer by chemical vapor deposition (CVD). In a second novel approach, silicon nitride CVD was combined with radical oxidation to form silicon oxide in a stepwise sequence. The resulting stack of silicon oxide films was then annealed at temperatures between 1000 and 1100 °C. All processes were executed in an industrial environment using 200 mm-diameter (100)-oriented silicon wafers. The goal was to optimize the trade-off between wafer uniformity and conformality of the trenches. The thickness of the resulting silicon oxide films was determined by ellipsometry of the wafer surface and by scanning electron microscopy of the trench cross sections. The insulation properties such as gate leakage and electrical breakdown were characterized by current–voltage profiling. The electrical breakdown was found to be highest for films treated with rapid thermal processing. The films fabricated via the introduced sequential process exhibited a breakdown behavior comparable to films deposited by the common low-pressure CVD technique, while the leakage current at electric fields higher than 5 MV/cm was significantly lower.

Shape memory alloys (SMAs) have been recognized as one of the most promising materials for MEMS micro-actuator applications. Among the available materials, Nickel/Titanium (NiTi) SMAs are more popular because, they exhibit unique properties in shape memory effect (SME) and pseudo-elasticity (PE). In addition NiTi SMA possesses high corrosion resistance, excellent mechanical properties and is also bio¬compatible. NiTi thin-film SMAs have been considered as the most significant material in the field of MEMS applications, which can be patterned with standard lithographic techniques to scale-up for batch production. However, the lack of proper understanding of basic materials’ properties and inability to reproduce, has limited the usage of this material in MEMS devices. The properties of NiTi SMA thin-films are very much sensitive to the elemental composition and structure, which are in turn decided by the deposition process and process parameters. A brief history of NiTi shape memory alloys (SMAs), basic information, transformation characteristics, crystal structure, phase diagram and literature reviewed for the current motivation have been presented in the second chapter In the third chapter, a brief summary about the deposition techniques relevant to NiTi film deposition has been presented. The deposition of NiTi films by a number of deposition techniques such as thermal evaporation, co-evaporation, molecular beam Epitaxy, pulsed laser deposition, flash evaporation, electron beam deposition, filtered arc deposition, ion beam assisted sputter deposition, vacuum plasma spraying, ion beam sputtering, ECR sputtering and magnetron sputtering techniques have been discussed. In order to achieve a precise control over film thickness and composition of the films on to the substrates, the selection of magnetron sputtering has been highlighted. In the present thesis, two prolonged approaches such as DC magnetron sputtering of an alloy target and co-sputtering of elemental targets have been presented. Various characterization techniques used for film thickness, composition, structure, micro¬structure, electrical, phase transformation and mechanical properties have also been briefly presented in the same chapter. In the fourth chapter, description of Conventional Alloy Target Sputtering System has been presented. DC magnetron sputtering of an alloy target with two different atomic ratios (Ni:Ti = 45:55 & 50:50) has been used for depositing the coatings. Several limitations in the reproducibility and repeatability have been observed with single alloy target sputtering, irrespective of the target composition ratio. In addition to this, incorporation of oxygen in the films during and after deposition has been observed, which has limited the extensive usage of this single alloy target system. The limitations regarding control over composition, thickness uniformity over large area have been improved by designing and fabricating a dedicated Three Target Magnetron Co-sputtering System. The vacuum diagnosis of the system under different conditions has been carried out by using PPR-200 Residual Gas Analyzer (RGA), which have included in Appendix I. Similar to alloy target sputtering system, the thickness uniformity and required composition with deposition parameters over a size of 75 mm diameter has been achieved and the process repeatability has been established. Oxygen incorporation in the films during deposition has been minimized by pre-sputtering of Ti target for known duration of time, which has resulted in significant reduction in partial pressure of oxygen in the chamber. The oxide layer formation on film surface has been eliminated by in-situ capping layer (TiN) deposition. In the fifth chapter, the influence of process parameters such as sample locations, substrate to target distance (STD), working pressure (WP), gas flow rates, deposition rates, deposition and annealing temperature, Target power, on the film thickness and composition uniformity have been presented for alloy target sputtering system as well as for the co-sputtering system. The film thicknesses have been measured with stylus method. Film compositions have been determined by energy dispersive X-ray spectroscopy (EDS), Secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). The working pressure of 1.5 X 10-3 mbar, STD of 90 mm and target power of 100 W have been found to produce coatings having uniform thickness and composition over the given area for alloy target sputtering system. Similar investigations have been carried out for co-sputtered NiTiCu films. The working pressure of 1.5x 10-3 mbar, at a STD of 90 mm, at a rotational speed of 15 rpm and at target powers of 600, 50 and 12 W for Ti, Ni and Cu respectively, have resulted in the thickness and required composition uniformity over a size of 75 mm diameter substrate and the process repeatability has been established. In the Sixth chapter, the influence of process parameters on film structure and micro-structure on the NiTi/NiTiCu films deposited by a single alloy target and co¬sputtering have been studied by different analytical techniques like XRD, TEM, AFM, SEM etc. Phase transformation temperatures and kind of transformations have been investigated by DSC, Resistivity / Temperature and Stress/ Temperature studies and correlations have been established. The process parameters have been optimized for TiN deposition, which act as the capping layer to protect NiTi films from surface oxidation. The variation in mechanical behavior for the NiTi/ NiTiCu films before and after TiN capping by nano-indentation test have also presented. XRD and TEM studies have shown that the NiTi / NiTiCu films deposited at room temperature to 400o C are amorphous. Post-annealing, at a temperature of 450O C or above resulted in the film crystallization with oxide layer formation at the film surface, which has been confirmed by XRD and XTEM studies. In the case of Ni-rich NiTi films, R-phase diffraction peaks have also been identified in addition to the Austenite / Martensite phase. XRD investigations have shown that Ti-rich NiTi and Ni-rich NiTi films have resulted in precipitate free films. In the case of Ti-rich NiTiCu and Ni-rich NiTiCu films, the variations in Ti/Ni target power has resulted in the formation of NiTi 2 and Ni3Ti precipitates along with their parent Martensite and Austenite phases. When the Cu content is increased in NiTiCu films, an increase in number of Martensite phase diffraction peaks in XRD spectrum has been observed. XTEM studies have confirmed formation of oxide layer, inter-metallic layer and interface layer at higher post annealing temperatures. SEM studies have shown that the films deposited at higher gas flow rate results in the columnar micro-structure. In the context of NiTiCu films, the films deposited at higher Ti target power have shown more compact and tightly packed film micro-structure. AFM studies have shown increase in the average crystallite size and film roughness with post annealing temperature and duration. TiN coating has been used as the capping layer onto NiTi / NiTiCu films. Structural and micro-structural comparison of these films before and after TiN coating has resulted the appearance of (111) TiN peak in all TiN capped films. SEM and AFM studies have shown that the film roughness have decreased after capping layer deposition. DSC thermal cycling used to verify the film crystallization temperature has shown the appearance of exothermic peak in NiTi / NiTiCu films. DSC, Resistivity-temperature, stress-temperature response has been confirmed the transformation temperature and kind of transformations in all the films. Residual stress measurements have shown that the crystalline films exhibited lower bi-axial stress in comparison to the amorphous films. Ti-rich NiTi films have shown single phase transformations (M-A and A-M) whereas two phase transformations (M-R-A and A-R-M) have been observed in Ni-rich NiTi films. Higher deposition / annealing temperature have shown the appearance of distinct phase transformation peaks in resistivity vs. temperature studies. In the case of NiTiCu films, the decrease in film crystallization temperature with increase in the Cu content has been observed. The phase transformation temperature evaluated from second thermal cycle has shown decrease in the width of hysteresis loop with increase in the Cu content in NTC films. Nano-indentation studies have been carried out to evaluate the micro-hardness and modulus values of TiN capped and uncapped NiTi / NiTiCu films. The modulus and hardness uniformity have been confirmed for the different location over a diameter of 75 mm. The modulus and hardness values have increased with increase in the substrate and annealing temperature. Increase in the Cu target power has resulted in the increase in the hardness and modulus values under same deposition conditions. TiN coated NiTi / NiTiCu films have shown larger modulus and hardness values than the uncapped films. In the Seventh chapter, the fabrication process and actuation response for silicon dioxide, Aluminum and NiTi SMA coated micro-cantilevers has been discussed. Various nano-structures such as pyramids, beams and pillars by focused ion beam (FIB) micro-machining have been fabricated. High aspect ratio nano-pillars have been selected for micro-compression testing. In summary, this thesis emphasizes on the fabrication of specific sputtering systems relevant to NiTi film deposition and process parameter optimization for desired film thickness and composition uniformity. DC magnetron sputtering of a NiTi alloy target (50:50 and 45:55 at. %) and co-sputtering of elemental targets (Ni, Ti and Cu) have been presented. These films have been investigated for structural, micro-structural, phase transformation and mechanical properties. In-situ deposition of TiN capping layer, on to NiTi / NiTiCu films has been carried out to reduce the oxygen trapping. The fabrication process and actuation response of micro-cantilevers have been described. The etching characteristics to generate various nano-structures viz. pyramids, beams and pillars by focused ion beam (FIB) micro-machining have been investigated and mechanical testing of selected nano-structures have also been reported.

Ces dix dernières années, les technologies de stockage non-volatile Flash ont joué un rôle majeur dans le développement des appareils électroniques mobiles et multimedia (MP3, Smartphone, clés USB, ordinateurs ultraportables…). Afin d’améliorer davantage les performances, augmenter les capacités et diminuer les coûts de fabrication, de nouvelles solutions technologiques sont aujourd’hui étudiées pour pouvoir compléter ou remplacer la technologie Flash. Citées par l’ITRS, les mémoires résistives polymères présentent des caractéristiques très prometteuses : procédés de fabrication à faible coût et possibilité d’intégration haute densité au dessus des niveaux d’interconnexions CMOS ou sur substrat souple. Ce travail de thèse a été consacré au développement et à l'étude des mémoires résistifs organiques à base de polymère de poly-méthyl-méthacrylate (PMMA) et de molécules de fullerènes (C60). Trois axes de recherche ont été menés en parallèle: le développement et la caractérisation physico-chimique de matériaux composites, l’intégration du matériau organique dans des structures de test spécifiques et la caractérisation détaillée du fonctionnement électrique des dispositifs et des performances mémoires. / Over the past decade, non-volatile Flash storage technologies have played a major role in the development of mobile electronics and multimedia (MP3, Smartphone, USB, ultraportable computers ...). To further enhance performances, increase the capacity and reduce manufacturing costs, new technological solutions are now studied to provide complementary solutions or replace Flash technology. Cited by ITRS, the polymer resistive memories present very promising characteristics: low cost processing and ability for integration at high densities above CMOS interconnections or on flexible substrate. This PhD specifically focused on the development and study of composite material made of Poly-Methyl-Methacrylate (PMMA) polymer resist doped with C60 fullerene molecules. Studies were carried out on three different axes in parallel: Composite materials development & characterization, integration of the organic material in specific test structure and advanced devices and finally detailed electrical characterization of memory cells and performances analysis.

We present the development of a novel, UHV-compatible device fabrication strategy for the realisation of nano- and atomic-scale devices in silicon by harnessing the atomic-resolution capability of a scanning tunnelling microscope (STM). We develop etched registration markers in the silicon substrate in combination with a custom-designed STM/ molecular beam epitaxy system (MBE) to solve one of the key problems in STM device fabrication ??? connecting devices, fabricated in UHV, to the outside world. Using hydrogen-based STM lithography in combination with phosphine, as a dopant source, and silicon MBE, we then go on to fabricate several planar Si:P devices on one chip, including control devices that demonstrate the efficiency of each stage of the fabrication process. We demonstrate that we can perform four terminal magnetoconductance measurements at cryogenic temperatures after ex-situ alignment of metal contacts to the buried device. Using this process, we demonstrate the lateral confinement of P dopants in a delta-doped plane to a line of width 90nm; and observe the cross-over from 2D to 1D magnetotransport. These measurements enable us to extract the wire width which is in excellent agreement with STM images of the patterned wire. We then create STM-patterned Si:P wires with widths from 90nm to 8nm that show ohmic conduction and low resistivities of 1 to 20 micro Ohm-cm respectively ??? some of the highest conductivity wires reported in silicon. We study the dominant scattering mechanisms in the wires and find that temperature-dependent magnetoconductance can be described by a combination of both 1D weak localisation and 1D electron-electron interaction theories with a potential crossover to strong localisation at lower temperatures. We present results from STM-patterned tunnel junctions with gap sizes of 50nm and 17nm exhibiting clean, non-linear characteristics. We also present preliminary conductance results from a 70nm long and 90nm wide dot between source-drain leads which show evidence of Coulomb blockade behaviour. The thesis demonstrates the viability of using STM lithography to make devices in silicon down to atomic-scale dimensions. In particular, we show the enormous potential of this technology to directly correlate images of the doped regions with ex-situ electrical device characteristics.

We present the development of a novel, UHV-compatible device fabrication strategy for the realisation of nano- and atomic-scale devices in silicon by harnessing the atomic-resolution capability of a scanning tunnelling microscope (STM). We develop etched registration markers in the silicon substrate in combination with a custom-designed STM/ molecular beam epitaxy system (MBE) to solve one of the key problems in STM device fabrication ??? connecting devices, fabricated in UHV, to the outside world. Using hydrogen-based STM lithography in combination with phosphine, as a dopant source, and silicon MBE, we then go on to fabricate several planar Si:P devices on one chip, including control devices that demonstrate the efficiency of each stage of the fabrication process. We demonstrate that we can perform four terminal magnetoconductance measurements at cryogenic temperatures after ex-situ alignment of metal contacts to the buried device. Using this process, we demonstrate the lateral confinement of P dopants in a delta-doped plane to a line of width 90nm; and observe the cross-over from 2D to 1D magnetotransport. These measurements enable us to extract the wire width which is in excellent agreement with STM images of the patterned wire. We then create STM-patterned Si:P wires with widths from 90nm to 8nm that show ohmic conduction and low resistivities of 1 to 20 micro Ohm-cm respectively ??? some of the highest conductivity wires reported in silicon. We study the dominant scattering mechanisms in the wires and find that temperature-dependent magnetoconductance can be described by a combination of both 1D weak localisation and 1D electron-electron interaction theories with a potential crossover to strong localisation at lower temperatures. We present results from STM-patterned tunnel junctions with gap sizes of 50nm and 17nm exhibiting clean, non-linear characteristics. We also present preliminary conductance results from a 70nm long and 90nm wide dot between source-drain leads which show evidence of Coulomb blockade behaviour. The thesis demonstrates the viability of using STM lithography to make devices in silicon down to atomic-scale dimensions. In particular, we show the enormous potential of this technology to directly correlate images of the doped regions with ex-situ electrical device characteristics.