Chemical mechanical polishing (CMP) has been used for a long time in the manufacturing of prime silicon wafers for the IC industry. Lately, other substrates, such as silicon-on-insulator has become in use which requires a greater control of the silicon CMP process. CMP is used to planarize oxide interlevel dielectric and to remove excessive tungsten after plug filling in the Al interconnection technology. In Cu interconnection technology, the plugs and wiring are filled in one step and excessive Cu is removed by CMP. In front end processing, CMP is used to realize shallow trench isolation (STI), to planarize trench capacitors in dynamic random access memories (DRAM) and in novel gate concepts. This thesis is focused on CMP for front end processing, which is the processing on the device level and the starting material. The effects of dopants, crystal orientation and process parameters on silicon removal rate are investigated. CMP and silicon wafer bonding is investigated. Also, plasma assisted wafer bonding to form InP MOS structures is investigated. A complexity of using STI in bipolar and BiCMOS processes is the integration of STI with deep trench isolation (DTI). A process module to realize STI/DTI, which introduces a poly CMP step to planarize the deep trench filling, is presented. Another investigated front end application is to remove the overgrowth in selectively epitaxially grown collector for a SiGe heterojunction bipolar transistor. CMP is also investigated for rounding, which could be beneficial for stress reduction or to create microoptical devices, using a pad softer than pads used for planarization. An issue in CMP for planarization is glazing of the pad, which results in a decrease in removal rate. To retain a stable removal rate, the pad needs to be conditioned. This thesis introduces a geometrically defined abrasive surface for pad conditioning.

L’objectif de cette étude est de recycler du slurry, suspension silicatée, utilisé dans le domaine de l’électronique lors du polissage. Deux applications de polissage sont étudiées : le polissage silicium et le polissage tungstène. Pour ces deux applications, une caractérisation physico-chimique des slurries en amont et en aval du procédé de polissage a mis en exergue une importante dilution du slurry par de l’eau déionisée destinée au rinçage des wafers : une collecte ségrégée a ainsi été mise en place. Le procédé d’ultrafiltration permet une reconcentration de la silice. Toutefois ce procédé ne permet pas la récupération des composés dissous du slurry, qui restent pourtant essentiels au polissage et d’autant plus pour l’application tungstène : un ajustement chimique est donc développée avant réutilisation du slurry ainsi retraité. Pour le slurry tungstène, la matrice chimique étant plus complexe, deux types d’ajustement ont été testés dont les proportions ont été optimisées par une méthode de plans d’expériences.Concernant le slurry silicium, un prototype industriel a été installé et les résultats de polissage sont similaires au slurry POU sur un nombre significatif de plaques. La qualification industrielle a été réalisée. Ce prototype permet d’atteindre les objectifs de diminution de 30% de la consommation de slurry et de 40% des volumes d’effluents rejetés vers station d’épuration. / The chemical and mechanical polishing is a costly step in the process of microelectronic chips manufacturing. This study aims for recycle the silicate suspension named slurry by membrane processes. Both polishing applications are studied: the silicium and the tungsten polishing. A physical and chemical characterization before and after polishing process shows an important dilution of slurry by deionized water used for wafers rinsing. From CMP machine, a collect segregation of a concentrated effluent is realised by a diverter valve. Ultrafiltration has been chosen to reconcentrate silica but does not permit to recover the chemical compounds of the slurry which are essential to the polishing mainly to the tungsten application. Thus, retreatment process includes a collect segregation at the CMP outlet to decrease the dilution factor of slurry, an ultrafiltration step to concentrate silica and a chemical adjustment step. About tungsten application, the chemical media is more complex and two types of adjustment have been led. Firstly, a mix of POU and retreated slurry has been tested and secondly, an experiment of design with three important compounds of the slurry has been tested. Most CMP parameters are obtained in industrial specifications with the mix of POU and retreated slurry.Concerning the silicium slurry, an industrial prototype is installed and polishing results are similar to the original slurry for a significant wafers number. The industrial agreement is obtained. This prototype allows reaching a 30% decrease of slurry consumption and a 40% decrease of waste waters.

Composite materials formed from two or more functionally different materials offer a versatile avenue to create a tailored material with well defined traits. Within this dissertation research, multi-functional composites were synthesized based on organic and inorganic materials. The functionally of these composites was experimentally tested and a semi-empirical model describing the sedimentation behavior of these particles was developed. This first objective involved the fabrication of microcomposites consisting of titanium dioxide (TiO2) nanoparticles confined within porous, microgels of a thermo-responsive polymer for use in the photocatalytic treatment of wastewater. TiO2 has been shown to be an excellent photocatalyst with potential applications in advanced oxidative processes such as wastewater remediation. Upon UV irradiation, short-lived electron-hole pairs are generated, which produce oxidative species that degrade simple organic contaminants. The rapid sedimentation of these microcomposites provided an easy gravimetric separation after remediation. Methyl orange was used as a model organic contaminant to investigate the kinetics of photodegradation under a range of concentrations and pH conditions. Although after prolonged periods of UV irradiation (~8-13 hrs), the titania-microgels also degrade, regeneration of the microcomposites was straightforward via the addition of polymer microgels with no loss in photocatalytic activity of the reformed microcomposites. The second objective within this dissertation involved the systematic development of abrasive microcomposite particles containing well dispersed nanoparticles of ceria in an organic/inorganic hybrid polymeric particle for use in chemical mechanical polishing/planarization (CMP). A challenge in IC fabrication involves the defect-free planarization of silicon oxide films for successful multi-layer deposition. Planarization studies conducted with the microcomposites prepared in this research, yield very smooth, planar surfaces with removal rates that rival those of inorganic oxides slurries typically used in industry. The density and size of these ceria-microgel particles could be controlled by varying the temperature or composition during synthesis, leading to softer or harder polishing when desired.

The use of ultracold neutrons (UCN) to study fundamental parameters such as the neutron lifetime and decay correlations in polarized neutron beta decay are poised to make significant contributions to our understand of the Standard Model and its extensions. To this end, the UCNA experiment is pursuing a precision measurement (0.2%) of the angular correlation between the neutron spin and the direction of emission of the electron in polarized neutron decay (the ``A'' asymmetry). The UCNA experiment makes use of the spallation-driven solid deuterium (SD2) UCN source at the Los Alamos Neutron Science Center (LANSCE). The UCN leave the source and are 100% polarized by passing through a strong magnetic field before their decay is observed by a very sensitive electron spectrometer. UCN guides facilitate the transfer of UCN from the source to the spectrometer. Common guide materials include stainless steel, copper, aluminum, and quartz. Often a thin film is applied to these components to increase their ability to transport/bottle and preserve the polarization of UCN. In the region of the SD2 UCN source, nickel-58 films are applied, whereas once the UCN are polarized, diamond-like carbon (DLC) films are employed. This dissertation covers the application, process developments, and characterization of these coatings. In addition a study concerning the surface finish resulting from the mechanical polishing and electropolishing of the guides that make up the UCNA beamline is presented. / Ph. D.

Nowadays, silicon photonics is a widely studied research topic. Its high-index-contrast and compatibility with the complementary metal-oxide-semiconductor technology make it a promising platform for low cost high density integration. Several general problems have been brought up, including the lack of silicon active devices, the difficulty of light coupling, the polarization dependence, etc. This thesis aims to give new attempts to novel solutions for some of these problems. Both theoretical modeling and experimental work have been done. Several numerical methods are reviewed first. The semi-vectorial finite-difference mode solver in cylindrical coordinate system is developed and it is mainly used for calculating the eigenmodes of the waveguide structures employed in this thesis. The finite-difference time-domain method and beam propagation method are also used to analyze the light propagation in complex structures. The fabrication and characterization technologies are studied. The fabrication is mainly based on clean room facilities, including plasma assisted film deposition, electron beam lithography and dry etching. The vertical coupling system is mainly used for characterization in this thesis. Compared with conventional butt-coupling system, it can provide much higher coupling efficiency and larger alignment tolerance. Two novel couplers related to silicon photonic wires are studied. In order to improve the coupling efficiency of a grating coupler, a nonuniform grating is theoretically designed to maximize the overlap between the radiated light profile and the optical fiber mode. Over 60% coupling efficiency is obtained experimentally. Another coupler facilitating the light coupling between silicon photonic wires and slot waveguides is demonstrated, both theoretically and experimentally. Almost lossless coupling is achieved in experiments. Two approaches are studied to realize polarization insensitive devices based on silicon photonic wires. The first one is the use of a sandwich waveguide structure to eliminate the polarization dependent wavelength of a microring resonator. By optimizing the multilayer structure, we successfully eliminate the large birefringence in an ultrasmall ring resonator. Another approach is to use polarization diversity scheme. Two key components of the scheme are studied. An efficient polarization beam splitter based on a one-dimensional grating coupler is theoretically designed and experimentally demonstrated. This polarization beam splitter can also serve as an efficient light coupler between silicon-on-insulator waveguides and optical fibers. Over 50% coupling efficiency for both polarizations and -20dB extinction ratio between them are experimentally obtained. A compact polarization rotator based on silicon photonic wire is theoretically analyzed. 100% polarization conversion is achievable and the fabrication tolerance is relatively large by using a compensation method. A novel integration platform based on nano-epitaxial lateral overgrowth technology is investigated to realize monolithic integration of III-V materials on silicon. A silica mask is used to block the threading dislocations from the InP seed layer on silicon. Technologies such as hydride vapor phase epitaxy and chemical-mechanical polishing are developed. A thin dislocation free InP layer on silicon is obtained experimentally. / QC20100705

L'objectif de ce travail de thèse a été d'évaluer, à partir d'outils de caractérisation électrique (spectroscopie d'impédance basse fréquence et courants thermo-stimulés), l'impact des étapes de polissage mécanochimique (CMP) et de recuits thermiques sur les propriétés diélectriques de matériaux utilisés pour les dernières générations de circuits intégrés. Une première partie est focalisée sur le matériau SiOCH poreux déposé par voie chimique « en phase vapeur » assisté par plasma (PECVD) suivant une approche porogène (p=26%, d=2nm et er=2,5). Son intégration dans les technologies 45nm nécessite l'utilisation d'un procédé de ‘CMP directe' qui induit une dégradation des propriétés isolantes attribuée à l'adsorption de surfactants et de molécules d'eau. L'analyse diélectrique sur une large gamme de fréquence (10-1Hz- 105Hz) et de température (-120°C -200°C) a mis en évidence plusieurs mécanismes de relaxation diélectrique et de conduction liés à la présence de molécules nanoconfinées (eau et porogène) dans les pores du matériau. L'étude de ces mécanismes a permis d'illustrer le phénomène de reprise en eau du SiOCH poreux ainsi que d'évaluer la capacité de traitements thermiques à en restaurer les performances. Une seconde partie concerne l'étude d'une résine époxy chargée avec des nanoparticules de silice, utilisée en tant que ‘wafer level underfill' dans les technologies d'intégration 3D. Les analyses en spectroscopie d'impédance ont montré que l'ajout de nanoparticules de silice s'accompagne d'une élévation de la température de transition vitreuse et de la permittivité diélectrique, ainsi que d'une diminution de la conductivité basse fréquence. L'autre contribution majeure des mesures diélectriques a été de montrer qu'un refroidissement trop rapide de la résine à l'issue de la réticulation était responsable d'une contrainte interne qui pourra occasionner des problèmes de fiabilité pour l'application. / The aim of the thesis was to investigate, by electrical means (dielectric spectroscopy and thermally stimulated current), the impact of the chemical-mechanical polishing process and of thermal treatments on the dielectric properties of materials used in state-of-the-art Integrated Circuit (IC) technologies. A first part focuses on the nanoporous SiOCH (p=26%, e=2 nm and er=2,5) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) using a porogen approach. After undergoing a process of direct CMP for its integration in the 45 nm node technology and beyond, those films experience a degradation of the insulating properties due to the adsorption of water and surfactants. A dielectric analysis performed on a wide range of frequency (10-1Hz - 105Hz) and temperature (-120°C - 200°C) exhibited many dielectric relaxation and conduction mechanisms due to molecules (water and porogen) nano-confined in pores. The phenomenon of water uptake of the porous SiOCH has been enlightened and the efficiency of thermal treatment to restore its performances has been evaluated through the study of these mechanisms. A second part deals with an epoxy resin filled with nano-particles of silica used as ‘wafer level underfill' for the 3D integration. Impedance spectroscopy showed that the addition of nano-particles induces an increase in the glass transition temperature and dielectric permittivity, as well as a decrease of the low frequencyconductivity. Furthermore, the dielectric measurements showed that a fast cool down of the resin after the cross-linking stage give rise to internal stresses which could potentially lead to reliability issues.