La miniaturisation des dispositifs de la microélectronique nécessite la mise au point de procédé de gravure toujours plus précis. Le sujet de cette thèse s’inscrit dans cette problématique, en effet un procédé de gravure séquentielle contrôlée à l’échelle nanométrique a été proposé pour pallier aux défauts inhérents à la gravure plasma directe. Ce procédé de gravure destiné dans notre cas à la gravure d’espaceurs en SiN, se décompose en deux étapes. La première étape est une implantation d’atome léger. L’implantation d’espèces chimiques légères telles que de l’Hydrogène ou de l’Hélium présente l’avantage de modifier la structure du matériau sans induire une pulvérisation dommageable pour le dispositif à graver. La couche modifiée par l’implantation est ensuite gravée de manière sélective vis-à-vis du matériau pristine via un plasma « downstream » ou plasma déporté.L’implantation d’hydrogène ayant principalement été étudiée au cours de ces travaux, différentes caractérisations visant à quantifier l’hydrogène implanté ainsi que l’épaisseur modifiée ont été réalisées. En effet, des mesures de réflectométrie des rayons X ont permis de déterminer l’épaisseur modifiée en fonction de la puissance d’autopolarisation ainsi que de la durée d’implantation. Des profils d’implant hydrogène sur du SiN ont également été effectués au travers de caractérisations électriques. Les profils de densité de charge obtenus ont été comparés à des profils de liaisons Si-H et N-H obtenus à partir de mesures spectroscopiques infra-rouge en réflexion multiple, et ces mesures ont également été comparées à des profils de spectrométrie de masse à ionisation secondaire. Ces profils permettent de quantifier l’hydrogène implanté en fonction de la profondeur, et ont également fournis des informations vis-à-vis de l’influence du rayonnement UV et de la configuration chimique du matériau implanté. Une présence significative d’oxyde à la surface du matériau implanté a également été observée par le biais de mesures spectroscopique de photoélectrons X.L’étape de retrait a principalement été étudiée via des mesures ellipsométriques cinétiques in situ, et des mesures spectroscopique de photoélectrons X pour différentes conditions de température, et pour différents mélanges chimiques. Les mesures ellipsométriques ont permis d’observer la formation de sels durant la gravure, alors que les analyses spectroscopiques de photoélectrons X ont montré que la surface du matériau été désoxydée par le plasma de retrait, parallèlement une quantité importante de fluor a été mesurée à la surface du matériau.Les études réalisées sur les étapes d’implantation et de retrait ont permis de graver de manière satisfaisante des échantillons patternés dans les conditions adéquates. / The miniaturization of microelectronics devices requires the development of ever more accurate etching processes. The subject of this thesis is part of this problematic: a controlled sequential etching process at the nanoscale has been developed to overcome the inherent defects of direct plasma etching. This etching process intended in our case for the etching for SiN spacers, is divided in two steps. The first step is a light atom implantation. The implantation of light chemical species such as Hydrogen or Helium has the advantage of modifying the structure of the material without inducing a damaging sputtering for the device to be etched. In the second step, the layer modified by the implantation is etched selectively regarding the pristine material via a remote plasma.Hydrogen implantation was mainly studied during this work: different characterizations to quantify the implanted hydrogen as well as the modified thickness were carried out. X-ray reflectometry measurements were used to determine the modified thickness as a function of the self-polarization power and the duration of implantation. Hydrogen implant profiles on SiN were also carried out through electrical characterizations. The charge density profiles observed were compared to Si-H and N-H bond profiles obtained from infrared spectroscopic measurements in multiple reflections. These measurements were also compared to secondary ionization mass spectrometry profiles. These profiles make it possible to quantify implanted hydrogen as a function of depth, and have also provided information regarding the influence of UV radiation and the chemical configuration of the implanted material. A significant presence of oxide on the surface of the implanted material has also been observed through X-ray photoelectron spectroscopic measurements.The removal step was mainly studied via kinetic ellipsometric in situ measurements and X-ray photoelectron spectroscopic measurements for different temperature conditions and for different chemical mixtures. The ellipsometric measurements made it possible to observe the formation of salts during etching, whereas the X-ray photoelectron spectroscopic analysis showed that the surface of the material was deoxidized by the remote plasma, while a large quantity of fluorine was measured at the same time on the material surface. The studies carried out on the implantation and removal steps made it possible to succesfully etch patterned samples under the appropriate conditions.

Parmi d’autres caractéristiques, la mémoire électronique idéale doit présenter une faible consommation d'énergie, haute densité et de la rapidité en lecture/écriture/effacement. Différents types de mémoires ont été ainsi développées. Un exemple en l’eSTM (Embedded Select Trench Memory). Ce travail de thèse étudie la caractérisation et l'optimisation des procédés de gravure plasma utilisés dans la fabrication de cette nouvelle technologie développée par STMicroelectronics Rousset, l'eSTM. Ce travail a été fortement lié à la caractérisation des parois du réacteur, le plasma lui-même et la surface de la plaquette de silicium. La caractérisation chimique des surfaces exposées aux plasmas a permis de caractériser et d'optimiser ce nouveau procédé de gravure. De plus, cette étude vise également à comprendre les dépôts sur les parois du réacteur qui se produisent pendant la gravure de la tranchée de l’eSTM. Ces interactions sont responsables de l’absence de reproductibilité des procédés de gravure. La gravure plasma est contrôlée par la formation d'une couche de passivation se formant en surface des flancs du silicium. La maitrise de cette couche par les conditions du plasma (pression, puissance source débit de gaz...) a permis de développer un model innovant afin d'optimiser le CD de la tranchée. De plus, cette thèse a également porté sur l'étude des dérives des CD au niveau des STI (Shallow Trench Isolation). Des mesures correctives ont été développées afin de contrôler les sources de variations en créant une nouvelle stratégie de gravure pour corriger la dispersion des CD entre lots (25 plaquettes de silicium). / Among other characteristics, the ideal memory should have low power consumption, fast read/write/erase and high density solution. Different types of memories have been developed to pursuit these specific properties. Example of this attempt is the eSTM (Embedded Select Trench Memory). This PhD work studies the characterization and optimization of the plasma etching processes for this new technology developed by STMicroelectronics, the eSTM. This work has been highly related to the characterization of the reactor walls, the plasma itself and the wafer surface. The main objectives of this thesis are to understand the fundamental mechanisms of the etching processes and to propose innovative solutions to reduce the variations of CD by reaching the good control of the process desired. This thesis would help for the enhancement of our knowledge on the physical phenomena which happens during this process, especially the passivation. This would offer the possibility of optimize the etch process and get the best CD (Critical Dimension) in terms of electrical results. The emphasis, was put on the characterization to get the maximum knowledge about the interactions taking place during the process, such as plasma-surface interactions and plasma-reactor wall interactions. Furthermore, this thesis was also focused on the optimization of the process drifts at STI (Shallow Trench Isolation) level, since the reproducibility of production processes generates serious concerns in making the component of the chips. Therefore, corrective actions were developed to control the source of variations by creating a regulation loop able to correct the CD dispersion between lots (25wafers).

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第17788号 / 工博第3767号 / 新制||工||1576(附属図書館) / 30595 / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 斧 髙一, 教授 木村 健二, 教授 立花 明知 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19687号 / 工博第4142号 / 新制||工||1639(附属図書館) / 32723 / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 斧 髙一, 教授 稲室 隆二, 教授 青木 一生 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24580号 / 工博第5086号 / 新制||工||1974(附属図書館) / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 江利口 浩二, 教授 土屋 智由, 教授 平方 寛之 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This dissertation presents a method for fabricating integrated hollow and solid optical waveguides on planar substrates. These waveguides are antiresonant reflecting optical waveguides (ARROWs), where high-index cladding layers confine light to hollow cores through optical interference. Hollow waveguides that can be filled with liquids or gases are an important new building block for creating highly-integrated optical sensors. The method developed for fabricating these integrated waveguides employs standard processes and materials used in the microelectronics industry, allowing for parallel, low-cost fabrication. Dielectric cladding layers are deposited on a silicon wafer using plasma-enhanced chemical vapor deposition (PECVD). After the lower cladding layers have been deposited, a sacrificial material is deposited and patterned using photolithography to produce the hollow-core shape. After the sacrificial cores are defined, they are coated with additional PECVD dielectric layers to form the sides and tops of the waveguides. Integrated solid-core waveguides can be easily created by etching a ridge into the top dielectric cladding layer. Finally, the ends of the sacrificial cores are exposed and removed with an acid solution, resulting in hollow waveguides. Improved optical performance for integrated ARROW platforms can be achieved by only using a single over-coating for the cladding on the sides and top of the hollow waveguide. Such a structure resulted in 70% improvement in optical throughput for the platforms and increased sensitivity for optical manipulation and fluorescence detection of single particles, including viruses. Reduced loss for the hollow waveguides can be obtained by surrounding the core with a terminal layer of air on the sides and top of the waveguide. Such devices were created by forming the hollow waveguides on top of a pedestal on the silicon substrate. This process produces the ideal geometry for hollow ARROW waveguides, and loss measurements of waveguides with air-filled cores had loss coefficients of 1.54/cm, which is the lowest achieved for air-core ARROWs.

This dissertation presents research on the fabrication of optofluidic sensor platforms, which consist of integrated hollow waveguides and solid waveguides. Antiresonant reflecting optical waveguides (ARROWs) filled with liquids or gases, can be used for high-sensitivity sensing in applications of biotechnology, chemical synthesis, and analytical chemistry. The fabrication method developed for integrated ARROW sensing platforms utilizes standard microfabrication processes and materials. Dielectric cladding layers are deposited on a silicon wafer using plasma-enhanced chemical vapor deposition (PECVD) or sputtering. A sacrificial material is then patterned over the bottom cladding layers by photolithography. Additional dielectric layers are deposited around the core, forming the structure of the waveguides. Integrated solid-core waveguides can be easily created by etching a ridge into the topmost dielectric cladding layer. The hollow core waveguides are then formed by wet etching the sacrificial core material. The coupling efficiency between solid core and hollow core waveguides is extremely important for the platform's overall sensitivity. Efficiencies can be enhanced from 18% to 67% by adjusting the thickness of the thick top oxide. Experimental results prove that optical throughput was improved by 17.1× with this improved interface transmission. Sputtered films were investigated as an alternative to for producing cladding layers. The experimental results reveal that sputtered layers show poor adhesion and mechanical strength which make them unreliable for hollow waveguides with small dimension. High-sensitivity ARROW platforms were obtained by employing hybrid layers (PECVD SiO2 and sputtered Ta2O5) as claddings and building waveguides on self-aligned pedestals. The photolumiscence background was only 1/10 that of previous devices made with SiO2/SiN and the average signal-to-noise ratio was improved by 12×.

No description available.

Polymeric membranes for gas separation are limited in their performance by a trade-off between permeability and selectivity. New methods of design are necessary in making membranes, which can show both high permeability and selectivity. A mixed matrix membrane is one such particular design, which brings in the superior gas separation performance of inorganic membranes together with the easy processability and price of the polymers. In a mixed matrix membrane, the inorganic phase is dispersed in the polymeric continuous phase. Nanocomposite membranes have a more sophisticated design with a thin separation layer on top of a porous support. The objective of this research was to fabricate thin SWNT nanocomposite membranes for gas separation, which have both high permeability and selectivity. SWNT/polyacrylic nanocomposite membranes were fabricated by orienting the SWNTs by high vacuum filtration. The orientation of SWNTs on top of the porous support was sealed by UV polymerization. For making these membranes, the CNTs were purified and cut into small open tubes simultaneously functionalizing them with COOH groups. Gas sorption of CO2 in COOH functionalized SWNTs was lower than in purified SWNTs. Permeabilities in etched membrane were higher than Knudsen permeabilities by a factor of 8, and selectivities were similar to Knudsen selectivities. In order to increase the selectivities, SWNTs were functionalized with zwitterionic functional groups. Gas sorption in zwitterion functionalized SWNTs was very low compared to in COOH functionalized SWNTs. This result showed that the zwitterionic functional groups are kinetically blocking the gas molecules from entering the pore of the CNT. SWNT/polyamide nanocomposite membranes were fabricated using the zwitterion functionalized SWNTs by interfacial polymerization. The thickness of the separation layer was around 500nm. Gas permeabilities in the CNT membranes increased with increasing weight percentage of the SWNTs. Gas permeabilities were higher in COOH SWNT membrane than in zwitterion SWNT membrane. Gas selectivities were similar to the Knudsen selectivities, and also to the intrinsic selectivities in the pure polyamide membrane. The water flux in SWNT-polyamide membranes increased with increasing weight percentage of zwitterion functionalized SWNTs, along with a slight increase in the salt rejection. Membranes exhibited less than 1% variability in its performance over three days. / Ph. D.

Gallium nitride (GaN) and its related semiconductor alloys are attracting tremendous interest for their wide range of applications in blue and green LEDs, diode lasers, high-temperature and high-power electronics. Nanomaterials such as InGaN/GaN core-shell three-dimensional nanostructures are seen as a breakthrough technology for future solid-state lighting and nano-electronics devices. In a core-shell LED, the active semiconductor layers grown around a GaN core enable control over a wide range of wavelengths and applications. In this thesis the capability for the heteroepitaxial growth of a proof-of-principle core-shell LED is advanced. A design that can be applied at the wafer scale using metalorganic vapor phase epitaxy (MOVPE) crystal growth on highly uniform GaN nanorod (NR) structures is proposed. This project demonstrates understanding over the growth constraints of active layers and dopant layers. The impact of reactor pressure and temperature on the morphology and on the incorporated InN mole fraction was studied for thick InGaN shells on the different GaN crystal facets. Mg doping and effectiveness of the p-n junction for a core-shell structure was studied by extensive growth experiments and characterization. Sapphire and Si substrates were used, and at all the stages of growth and fabrication. The structures were optimized to achieve geometry homogeneity, high-aspect-ratio, incorporation homogeneity for InN and Mg dopant. The three-dimensional nature of NRs and their light emission provided ample challenges which required adaptation of characterization and fabrication techniques for a core-shell device. Finally, an electrically contacted core-shell LED is demonstrated and characterized. Achieving a proof-of-principle core-shell device could be the starting point in the development of nanostructure-based devices and new physics, or in solving technical problems in planar LEDs, such as the polarization of emitted light, the quantum-confined Stark effect, efficiency droop, or the green gap.