Le coût de la poursuite de la miniaturisation des transistors en-dessous de 14 nm demande l’introductionde techniques moins onéreuses comme l’approche auto-alignée par copolymères à blocs (DSA) combinéeà la lithographie 193 nm. Etudiée principalement pour des motifs de tranchées (pour les FinFETs)ou de cylindres verticaux (pour les trous de contact, c’est ce cas qui nous intéressera), le polystyrène-bpolyméthylmétacrylate(PS-b-PMMA) est un des copolymères à blocs les plus étudiés dans la littérature,et dont la gravure présente de nombreux défis dûs à la similarité chimique des deux blocs PS et PMMA.Proposer une solution à ces défis est l’objet de cette thèse.Dans notre cas où le PS est majoritaire, le principe est d’obtenir par auto-organisation des cylindresverticaux de PMMA dans un masque de PS. Le PMMA est ensuite retiré par solvant ou par plasma,les motifs ainsi révélés dans le PS peuvent être alors transférés en utilisant ce dernier comme masque degravure. Une couche de copolymères statistiques PS-r-PMMA neutralise les affinités du PS/PMMA avecle substrat et permet l’auto-organisation.Un des problèmes majeurs est le contrôle des dimensions ; traditionnellement, le PMMA est retiré paracide acétique et le PS-r-PMMA gravé par plasma d’Ar/O2 qui aggrandit le diamètre des trous (CD)en consommant lattéralement trop de PS. Des temps de recuit acceptables pour l’Industrie donnent ausommet du masque de PS une forme de champignon induisant une dispersion importante des diamètresmesurés (~4-5 nm).Nos travaux montrent que la dispersion de CD peut être corrigée par plasma en facettant le sommetdes motifs. Dans un premier temps, un procédé de retrait du PMMA par plasma continu de H2N2 a étédéveloppé afin de s’affranchir des problèmes induits par l’acide acétique et les plasmas à base d’O2. Cecia permis de révéler des défauts d’organisation non rapportés dans la littérature à notre connaissance : desfilms de PS de quelques nanomètres peuvent aléatoirement se trouver dans le domaine du PMMA et ainsibloquer la gravure de certains cylindres. Afin de graver ces défauts sans perdre le contrôle des dimensions,un procédé composé d’un bain d’acide acétique et d’un plasma synchronisé pulsé de H2N2 à faible rapportde cycle et à forte énergie de bombardement a été mis au point. Il permet de retirer le PMMA, facetterle sommet du PS (ce qui réduit la dispersion de CD à moins de 2 nm), graver les défauts et la couche deneutralisation tout en limitant l’agrandissement des trous à moins d’un nanomètre. La dernière difficultévient des dimensions agressives et du rapport d’aspect important des trous de contact gravés. Afin delimiter la gravure latérale et la consommation des masques, des couches de passivation sont déposées surles flancs des motifs pendant la gravure mais à des échelles inférieures à 15 nm, ces couches de quelquesnanomètres sont trop épaisses et nuisent au contrôle des dimensions. Les plasmas doivent être alors moinspolymérisants et la création d’oxydes sur les flancs par ajout d’O2 doit être évitée.Enfin, les techniques de détermination des dimensions à partir d’images SEM ne sont plus assezrobustes à ces échelles. Afin d’en améliorer la robustesse, des algorithmes de reconstruction d’image etd’anti-aliasing ont été implémentés. / Shrinking transistor’s dimensions below 14 nm is so expensive that lower-cost complementary techniquessuch as Directed Self-Assembly (DSA) combined with 193 nm-lithography are currently beingdeveloped. Either organized as trenches for the FinFET’s fin or vertical cylinders for contact holes(which is our case study), Polystyrene-b-polymethylmetacrylate (PS-b-PMMA) is a well-studied blockcopolymer but introduces challenging etching issues due to the chemical similarities between the PS andPMMA blocks. The aim of this thesis is to overcome those etching challenges.In our case where PS is the dominant phase, the principle of DSA is to obtain through self-assemblya pattern of vertical cylinders of PMMA inside a mask constituted of PS. PMMA is then removed eitherby solvent or plasma, revealing the patterns in the PS mask, which will be used as an etching mask forpattern transfer. In order to allow self-assembly, a thin brush layer of random copolymers PS-r-PMMAis used to neutralize the affinity of each phase with the substrate.One of the main issues with DSA is the control of the dimensions (CD control): usually, PMMAis dissolved in acetic acid bath and the brush layer is etched by an Ar/O2 plasma which increasesdramatically the pore’s diameter (CD) by laterally etching the PS. Short duration of thermal annealingsuitable for the Industry induces some “mushroom” shape at the top of the mask which consequentlyincreases the measured CD dispersion (~ 4-5 nm).Our work shows that CD uniformity can be corrected by faceting the top of the patterns throughplasma etching. As a first step, a dry-etch process for PMMA based on H2N2 chemistry has beendeveloped in order to free ourselves from acetic-acid’s and O2-based plasma’s issues. As far as we know,the discovered kind of defects has never been reported in the literature: few nanometer-thick films madeof PS can randomly be found in the PMMA’s domain, thus delaying the etching of random cylinders. Inorder to etch those defects without loosing the CD control, an other process constituted of an acetic acidbath followed by a synchronously-pulsed H2N2 plasma at low duty cycle and high bias power has beendeveloped. This process removes PMMA, facets the top of the PS features (decreasing CD dispersionbelow 2 nm), etches both the defects mentionned above and the brush layer without increasing thepores’ diameters by more than one nanometer. One last etching challenge comes from the aggressivedimensions and the high aspect ratio of the contact holes. In order to limit the lateral etching and themask consumption overall, passivation’s layer are usually deposed on the sidewall of the features duringthe etching process, but at dimensions below 15 nm, those layers are too thick and cause a CD control lossthough they are only few-nanometer thick. The polymerization’s capacity of plasmas has to be loweredat this scale and oxidized layer’s formation by adding O2 to the plasma chemistry has to be avoided.Last but not least, the techniques based on SEM images to determine the pore’s dimensions are notrobust enough at those scales. In order to gain in robustness, image reconstruction and anti-aliasingalgorithm have been implemented.

Doctor of Philosophy / Department of Chemistry / Takashi Ito / We have investigated the orientation of cylindrical domains in thin films of a polystyrene–poly(methylmethacrylate) diblock copolymer (PS-b-PMMA) on planar substrates having different surface roughnesses and hydrophilicities. The research in this dissertation covers the substrate surface modifications, the enhancement of the diblock copolymer film coating, and the refinement of the treatments leading to nanoporous material. Treatment of the substrate with organic mercaptans forming self-assembled-monolayer (SAM), leading to various hydrophilicities of the surfaces, was inconclusive as far as orienting the PMMA domains in the PS matrix due to thermal instability of some thiols. This directed us to a different approach involving substrate roughness. PS-b-PMMA films of 20~200 nm thick were prepared via spin-coating on silicon, gold or indium tin oxide (ITO) substrates, and annealed in vacuum at 170 °C for 60 hours to induce the formation of cylindrical PMMA domains. Atomic force microscopy (AFM) images indicated the domain orientation at the free surface. In PS-b-PMMA films much thicker than the domain periodicity (L0), the domains were oriented perpendicularly to the free surface regardless of underlying substrates, reflecting the balanced interactions of PS and PMMA blocks at the polymer–vacuum interface. In films having thickness similar to L0, vertically oriented domains were observed on the Au and ITO surfaces that are covered with nanoscale grains, whereas horizontal domains were observed on the smooth Si substrates. In particular, the cylindrical PMMA domains were efficiently perpendicularly aligned when the grain size nearly was equal to L0. The perpendicular domain alignment induced by the substrate roughness was corroborated using cyclic voltammetry (CV) for gold substrates coated with PS-b-PMMA films whose PMMA domains were removed by UV and subsequent acetic acid treatments. The CV data also suggested that the PMMA domains were successfully removed, leaving a nanoporous stable PS matrix on the substrate.

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En las últimas décadas, el interés por los sistemas poliméricos, en particular por los copolímeros bloque, ha ido incrementándose, no solo desde el punto de vista académico sino también desde el tecnológico, porque permiten obtener materiales con propiedades especificas debido a la presencia de sus dos o más fases. Además, los copolímeros bloque presentan procesos de separación en microfases o formación de estructuras auto-ensambladas que los convierte en excelentes candidatos para aplicaciones en nanotecnología y electrónica. En esta Tesis se desarrollan técnicas para la obtención de membranas nanoporosas a partir del auto-ordenamiento de copolímeros bloque de Poli(estireno)-bloque-Poli(metil metacrilato), PS-b-PMMA. Los copolímeros fueron sintetizados, empleando polimerización aniónica en alto vacío, y caracterizados química y térmicamente mediante numerosas técnicas analíticas, tales como Cromatografía por exclusión de tamaños (SEC), Resonancia Magnética Nuclear de protón (1H-NMR), Espectroscopia Infrarroja con Transformada de Fourier (FTIR), Calorimetría Diferencial de Barrido (DSC), Análisis Termogravimétrico (TGA). Todos los copolímeros mostraron tener un control adecuado de las masas molares, presentando bajos índices de polidispersión para un amplio rango de masas molares y composiciones, además los resultados permitieron corroborar la formación de nanoestructuras. Se prepararon películas de los copolímeros sobre sustratos de silicio (Si), en los cuales se implementaron técnicas para la orientación de los dominios de PMMA en la matriz de PS. La metodología con mejores resultados fue la aplicación de una película de un copolímero al azar de PS-r-PMMA, de composición similar a los copolímeros bloque, que actúe como neutralizante del sustrato de modo que ambos bloques del copolímero sean afines a la superficie. Posteriormente, se degradó el bloque de PMMA, de manera de obtener una membrana nanoporosa. Estas membranas se caracterizaron morfológicamente mediante Microscopía de Fuerza atómica (AFM), y Microscopía electrónica de barrido (SEM). Las membranas nanoporosas presentaron poros de los tamaños esperados de modo de poder convertirse en prototipos para la preparación de membranas de filtración en aplicaciones industriales, como por ejemplo, filtros de virus. Los resultados informados en esta Tesis constituyen un aporte de interés respecto a las técnicas de preparación de membranas ya existentes. En tal sentido, se ha desarrollado una metodología de separación de las películas del sustrato, de modo de poder desarrollar una tecnología que permita soportarlas en sustratos porosos con el objeto de obtener membranas de filtración de virus u otras sustancias de tamaños similares. / In recent decades, interest in polymeric systems, in particular block copolymers, has been increasing, not only from the academic but also from the technological point of view. This allows obtaining materials with specific properties due to the presence of the two or more phases. In addition, block copolymers exhibit microphase separation and the formation of self-assembled structures, which makes them excellent materials for applications in nanotechnology and electronics. In this thesis, techniques were developed for obtaining nanoporous membranes from the self-ordering of polymer blocks in Poly(styrene) -block-Poly (methyl methacrylate), PS-b-PMMA. The copolymers were synthesized using high vacuum anionic polymerization and characterized chemically and thermally using analytical techniques such as Size Exclusion Chromatography (SEC), Proton Nuclear Magnetic Resonance (1H-NMR), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA). All the copolymers showed adequate control of the molar masses, presenting low polydispersity rates on a wide range of molar masses and compositions, besides the results allowed to corroborate the formation of nanostructures. Films of the copolymers were prepared on silicon (Si) substrates, in which several technics were implemented for the orientation of the PMMA domains in the PS matrix. The methodology with the best results was the application of a film of a random PS-r-PMMA copolymer, of similar composition to the block copolymers, which acts as a neutralizer of the substrate so that both blocks of the copolymers are surface related. Subsequently, the PMMA block was degraded in order to obtain a nanoporous membrane. These membranes were characterized morphologically by Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM). Nanoporous membranes presented pores of the expected sizes for converting in prototypes for the preparation of filtration membranes in industrial applications, such as virus filters. The results reported in this thesis constitute a contribution of interest regarding the techniques of preparation of already existing membranes. In this sense, a methodology has been developed for separating the films from the substrate, in order to develop a technology that allows them to be supported on porous substrates with the object of obtaining filtration membranes for virus or similar sized substances.