The addition of inorganic spherical nanoparticles to polymers allows the modification of the polymers physical properties as well as the implementation of new features in the polymer matrix. This review article covers considerations on special features of inorganic nanoparticles, the most important synthesis methods for ceramic nanoparticles and nanocomposites, nanoparticle surface modification, and composite formation, including drawbacks. Classical nanocomposite properties, as thermomechanical, dielectric, conductive, magnetic, as well as optical properties, will be summarized. Finally, typical existing and potential applications will be shown with the focus on new and innovative applications, like in energy storage systems.

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Polymer-Nanoparticle Composites: From Synthesis to Modern Applications

In the past decade, the feature size in ultra large-scale integration (ULSI) has been continuously decreasing, leading to nanostructure fabrication. Nowadays, various lithographic techniques ranging from conventional methods (e.g. photolithography, x-rays) to unconventional ones (e.g. nanoimprint lithography, self-assembled monolayers) are used to create small features. Among all these, resist-based electron beam lithography (EBL) seems to be the most suitable technique when nanostructures are desired. The achievement of sub-20-nm structures using EBL is a very sensitive process determined by various factors, starting with the choice of resist material and ending with the development process. After a short introduction to nanolithography, a framework for the nanofabrication process is presented. To obtain finer patterns, improvements of the material properties of the resist are very important. The present review gives an overview of the best resolution obtained with several types of both organic and inorganic resists. For each resist, the advantages and disadvantages are presented. Although very small features (2-5 nm) have been obtained with PMMA and inorganic metal halides, for the former resist the low etch resistance and instability of the pattern, and for the latter the delicate handling of the samples and the difficulties encountered in the spinning session, prevent the wider use of these e-beam resists in nanostructure fabrication. A relatively new e-beam resist, hydrogen silsesquioxane (HSQ), is very suitable when aiming for sub-20-nm resolution. The changes that this resist undergoes before, during and after electron beam exposure are discussed and the influence of various parameters (e.g. pre-baking, exposure dose, writing strategy, development process) on the resolution is presented. In general, high resolution can be obtained using ultrathin resist layers and when the exposure is performed at high acceleration voltages. Usually, one of the properties of the resist material is improved to the detriment of another. It has been demonstrated that aging, baking at low temperature, immediate exposure after spin coating, the use of a weak developer and development at a low temperature increase the sensitivity but decrease the contrast. The surface roughness is more pronounced at low exposure doses (high sensitivity) and high baking temperatures. A delay between exposure and development seems to increase both contrast and the sensitivity of samples which are stored in a vacuum after exposure, compared to those stored in air. Due to its relative novelty, the capabilities of HSQ have not been completely explored, hence there is still room for improvement. Applications of this electron beam resist in lithographic techniques other than EBL are also discussed. Finally, conclusions and an outlook are presented.

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Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art.

The present invention provides new high resolution resists applicable to next generation lithographies, methods of making these novel resists, and methods of using these new resists in lithographic processes to effect state-of-the-art lithographies. New nanocomposite resists comprising nanoparticles in a polymer matrix are provided in this invention. New chemically amplified resists that incorporate inorganic moieties as part of the polymer are presented herein, as are new chemically amplified resists that incorporate photoacid generating groups within the polymeric chain. Novel non-chemically amplified yet photosensitive resists, and new organic-inorganic hybrid resists are also provided herein. This invention and the embodiments described herein constitute fundamentally new architectures for high resolution resists.

High resolution resists for next generation lithographies

A new lithographic technique has been developed and applied to cell adhesion studies and electro-optical material development. Attachment of 6 nm Au particles, in periodic and non-periodic pattern, onto non-conductive substrates has been achieved. This was performed via a combination of diblock copolymer self-assembly and electron beam lithographic techniques. To optimize e-beam resolution on non-conductive materials, an additional carbon layer was thread-coated onto the substrates. This carbon coating and the diblock copolymer used in the self-assembly step were simultaneously removed by a final hydrogen plasma treatment to reveal Au nanodot patterns of unprecedented pattern quality. These optically transparent substrates (glass cover slips) were bio-functionalized via the Au-dot patterns to yield a platform for unique cell adhesion studies. The same Au-dot patterning technique was applied to sapphire substrates, which were subsequently employed to nucleate electro-optically active ZnO nanopost growth.

https://iopscience.iop.org/article/10.1088/1367-2630/6/1/101/pdf

Block copolymer micelle nanolithography on non-conductive substrates

Topcoat layer compositions are provided that are applied above a photoresist composition. The compositions find particular applicability to immersion lithography processing.

Compositions and processes for photolithography

Resists for advanced mask-making with high-voltage electron-beam writing tools have undergone dramatic changes over the last three decades. From PMMA and the other early chain-scission resists for micron dimensions to the aqueous-base-developable, dry-etchable chemically amplified systems being developed today, careful tuning of the chemistry and processing conditions of these resist systems has allowed the patterning of photomasks of increasing complexity containing increasingly finer features. Most recently, our research efforts have been focused on a low-activation-energy chemically amplified resist based on ketal-protected poly(hydroxystyrene). These ketal resist systems, or KRSs, have undergone a series of optimization and evaluation cycles in order to fine-tune their performance for advanced mask-fabrication applications using the 75-kV IBM EL4+ vector scan e-beam exposure system. The experiments have led to an optimized formulation, KRS-XE, that exhibits superior lithographic performance and has a high level of processing robustness. In addition, we describe advanced formulations of KRS-XE incorporating organometallic species, which have shown superior dry-etch resistance to novolak-based resists in the Cr etch process while maintaining excellent lithographic performance. Finally, current challenges facing the implementation of a chemically amplified resist in the photomask manufacturing process are outlined, along with current approaches being pursued to extend the capabilities of KRS technology.

Recent progress in electron-beam resists for advanced mask-making

Nanocomposite resist systems for next generation lithography

A nonpolymeric silsesquioxane is provided wherein at least one silicon atom of the silsesquioxane is directly or indirectly bound to an acid-cleavable substituent R CL . The silsesquioxane has a glass transition temperature T g of greater than 50° C., and the R CL substituent can be cleaved from the silsesquioxane at a temperature below T g , generally at least 5° C. below T g . The remainder of the silicon atoms within the silsesquioxane structure may be bound to additional acid-cleavable groups, acid-inert polar groups R P , and/or acid-inert nonpolar groups R NP . The nonpolymeric silsesquioxane can be a polyhedral silsesquioxane optionally having one to three open vertices, such that the polyhedron appears to be a “partial cage” structure, or a macromer of two to four such polyhedral silsesquioxanes. Photoresist compositions containing the novel nonpolymeric silsesquioxanes are also provided, as is a method for using the compositions in preparing a patterned substrate.

Molecular photoresists containing nonpolymeric silsesquioxanes

Aqueous base soluble conducting polymers are disclosed, as is their use to dissipate an electrical charge and thereby to improve the precision of processes involving charged particle beams. Electrically conductive functionalized polymers include polyanilines, polyparaphenylvinylenes, polythiophenes, polypyrroles, poly-p-phenylene oxides, polyfurans, polyphenylenes, polyazines, polyselenophenes, polyphenylene sulfides and polyacetylenes. Also disclosed are processes for the synthesis of poly(hydroxyanilines) and polythiophenes and compositions and methods for preparing aqueous base soluble conductive films.

Base developable discharge toplayer for E-beam resists

Embodiments include a silicon-containing antireflective material including a silicon- containing base polymer, a non-polymeric silsesquioxane material, and a photoacid generator. The silicon-containing base polymer may contain chromophore moieties, transparent moieties, and reactive sites on an SiOx background, where x ranges from approximately 1 to approximately 2. Exemplary non-polymeric silsesquioxane materials include polyhedral oligomeric silsesquioxanes having acid labile side groups linked to hydrophilic groups Exemplary acid labile side groups may include tertiary alkyl carbonates, tertiary alkyl esters, tertiary alkyl ethers, acetals and ketals, Exemplary hydrophilic groups may include phenols, alcohols, carboxylic acids, amides, and sulfonamides. Embodiments further include lithographic structures including an organic anti-reflective layer, the above-described silicon-containing anti-reflective layer above the organic anti-reflective layer, and a photoresist layer above the above-described silicon-containing anti-reflective layer. Embodiments further include a method of forming a lithographic structure utilizing the above-described silicon-containing anti- reflective layer.

Wu-Song Huang

Papers

Recent progress in electron-beam resists for advanced mask-making

Nanocomposite resist systems for next generation lithography

Molecular photoresists containing nonpolymeric silsesquioxanes

Base developable discharge toplayer for E-beam resists

Silicon-containing antireflective coatings including non-polymeric silsesquioxanes