[PDF] Directed Self Assembly Of Symmetric Block Copolymer With Density Multiplication For Nanopatterning Applications eBook
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Block copolymers (BCPs) are a group of fascinating materials that self-assemble into highly uniform nanoscale structures. With precise control of interfacial properties on both interfaces, these nanostructures can be directed to form user-defined periodic patterns. The directed self-assembly (DSA) of BCPs offers a cost-effective solution to complement the conventional lithography with the capability of density multiplication and pattern rectification. This dissertation mainly focuses on the chemoepitaxial DSA of symmetric BCP into line patterns.
The directed self-assembly (DSA) method of patterning for microelectronics uses polymer phase-separation to generate features of less than 20nm, with the positions of self-assembling materials externally guided into the desired pattern. Directed self-assembly of Block Co-polymers for Nano-manufacturing reviews the design, production, applications and future developments needed to facilitate the widescale adoption of this promising technology. Beginning with a solid overview of the physics and chemistry of block copolymer (BCP) materials, Part 1 covers the synthesis of new materials and new processing methods for DSA. Part 2 then goes on to outline the key modelling and characterization principles of DSA, reviewing templates and patterning using topographical and chemically modified surfaces, line edge roughness and dimensional control, x-ray scattering for characterization, and nanoscale driven assembly. Finally, Part 3 discusses application areas and related issues for DSA in nano-manufacturing, including for basic logic circuit design, the inverse DSA problem, design decomposition and the modelling and analysis of large scale, template self-assembly manufacturing techniques. Authoritative outlining of theoretical principles and modeling techniques to give a thorough introdution to the topic Discusses a broad range of practical applications for directed self-assembly in nano-manufacturing Highlights the importance of this technology to both the present and future of nano-manufacturing by exploring its potential use in a range of fields
Molecular self-assembly is the basis of structure in nature. While of far less complexity than a natural system, the same physical rules apply to simple synthetic designed systems that spontaneously form self-assembled structures and patterns. The self-assembly of block copolymers (BCPs) is an interesting example, as it can be harnessed to form both 2D (in thin films) and 3D (in bulk) porous and chemically controlled morphologies at scale. The self-assembly of BCPs on surfaces is of interest for a range of applications, but due to the enormous economic driver that is the computer industry, this direction has been pushed most strongly. Self-assembly of BCPs has been described in the International Technology Roadmap for Semiconductors (the ITRS, and now the IDRS) for almost two decades for lithography on semiconductors and for patterning the magnetic material of hard drives. As a result, there has been much academic interest, both fundamental and applied, to meet the challenges as outlined in the ITRS/IDRS due to the promise of this scalable and low-cost nanopatterning approach. More recently, the remarkable work harnessing BCP self-assembly has been directed to other applications, one being optical metamaterials; this thesis will add to this growing body of science. One aspect holding BCP self-assembly back is the defectivity in the patterned material or surface; some applications are more defect tolerant than others, but hard drive and other computer-industry applications have very low tolerance for defects. It is, therefore, important to have systematic control over the self-assembly process as well as quality of the final patterns generated by BCP self-assembly for these applications and others not yet imagined. This thesis examines the defectivity of the hexagonal nanoscale patterns derived from BCP self-assembly and looks at extending them to produce nanoscale patterns of native and non-native morphologies that have plasmonic properties. This thesis is divided into two parts. The first part deals with optimization of solvent vapor annealing of BCP self-assembly, the critical step in which the actual nanoscale phase segregation takes place; in this case, it uses a controlled solvent vapor flow annealing apparatus, design of experiment and machine learning approaches. In this work, it was discovered that slight variations in the initial film thickness on the order of even a couple of nanometers and the final swelling degree have a huge influence on the defectivity and the quality of the resulting patterns. Next, machine learning approaches are applied to compile qualitative and quantitative defect analysis into a single figure of merit that is mapped across an experimental parameter space. This approach enables faster convergence of results to arrive at the optimum annealing conditions for the annealing of thin films of BCPs of PS-b-PDMS that generate nanoscale hexagonal patterns of silica dots with a minimum number of defects. In the second part of the thesis, mixed metal/oxide double layer patterning was studied using sequential self-assembly of BCPs. The second part of the thesis starts with optimization of reactive ion etching (RIE) for producing single layer metal nanopatterns from metal ion-loaded thin films of PS-b-P2VP BCPs to generate single layers of hexagonal metal nanopatterns that can withstand a second consecutive reactive ion etching step. The goal of this work is to enable density doubled and/or Moiré pattern formation via self-assembly of a second layer of BCP on the initial pattern prepared by self assembly of either the same or different BCP, as will be described in Chapter 4. Therefore, the initial pattern produced via BCP self-assembly and RIE etching would need to withstand a second treatment step of BCP self-assembly and RIE. While single layer nanopatterns of Au and Pt nanoparticles can be produced without much trouble, these resulting patterns could not be applied for density multiplication of metal-metal nanopatterns since the metal dots become too small and disordered. To demonstrate that metal nanoparticles derived from BCPs could be used, at least, to produce a mixed metal oxide/metal patterns, arrays of SiOx dots were first produced from PS-b-PDMS BCPs and then layered a BCP of PS-b-P2VP that was subsequently loaded with gold or platinum ions. Upon RIE etching, the BCP is removed and the SiOx/Au or Pt nanoparticle arrays were produced. Based upon the outcomes of the optimization of the etching work, mixed Au-Pt commensurate and incommensurate hexagonal lattice patterns were produced on both silicon and quartz substrates. Finally, the optical properties of these mixed metal Pt-Au bilayer patterns were studied. They demonstrated interesting plasmonic properties of the bilayer patterns, including consistent observation of extended plasmon bands that suggest coupling of the localized surface plasmon resonances (LSPRs) of the gold nanoparticles through proximal platinum nanoparticles when arrayed in periodic patterns.
The impressive developments in the semiconductor industry over the past five decades have largely been dependent on the ability to continually reduce the dimensions of devices on a chip. However, as critical dimension requirements for these devices approach the limits of photolithography, new fabrication strategies must be introduced for these remarkable advances to continue. One technology listed by the International Technology Roadmap for Semiconductors as a candidate for next-generation nanostructure fabrication is the directed self-assembly of block copolymers. Block copolymers have received significant attention of late for their ability to template large regular arrays of nanostructures with dimensions ranging from 10 to 50 nm. The production of denser sub-10 nm nanostructures is also possible by reducing the size of these polymers, but a reduction of the polymer size also compromises the quality of nanostructures, making small polymers extremely difficult to use. In this thesis, two different patterning approaches are introduced to push the nanostructure density limits possible for a given polymer. In the first, a novel patterning approach involving thin films of bilayer block copolymer domains is used to effectively double the nanostructure density patterned by a given polymer. The technique is successfully applied to different types and sizes of polymer, and can also form highly controlled arrays of patterns with the help of surface topography. By varying different process parameters during the self-assembly or subsequent plasma steps, the dimensions of these density-doubled patterns may be finely-tuned to the desired width and pitch. The surface coverage of these density-doubled nanostructures is also maximized through adjusting the film thickness and parameters in the self-assembly process. Besides using bilayer films, dense arrays of nanostructures may also be patterned using a multi-step patterning approach. In this approach, multiple layers of block copolymer films are subsequently deposited onto the substrate to template nanostructures. Because nanostructures from previous layers contribute to the surface topography, they influence the self-assembly of successive layers and more dense and complex patterns may be produced as a result.
It is the belief of the editors of this book that the recognition of block copolymers as being amphiphilic molecules and sharing common features with other well-studied amphiphiles will prove beneficial to both the surfactant and the polymer communities. An aim of this book is to bridge the two communities and cross-fertilise the different fields. To this end, leading researchers in the field of amphiphilic block copolymer self-assembly, some having a background in surfactant chemistry, and others with polymer physics roots, have agreed to join forces and contribute to this book.The book consists of four entities. The first part discusses theoretical considerations behind the block copolymer self-assembly in solution and in the melt. The second part provides case studies of self-assembly in different classes of block copolymers (e.g., polyethers, polyelectrolytes) and in different environments (e.g., in water, in non-aqueous solvents, or in the absence of solvents). The third part presents experimental tools, ranging from static (e.g., small angle neutron scattering) to dynamic (e.g., rheology), which can prove valuable in the characterization of block copolymer self-assemblies. The fourth part offers a sampling of current applications of block copolymers in, e.g., formulations, pharmaceutics, and separations, applications which are based on the unique self-assembly properties of block copolymers.
Many researchers have studied the orientation behavior of block copolymers (BCPs) with the most recent works directed towards nanotechnologies. Self-assembly of block copolymers is very relevant in controlling periodic nanostructures for nanotechnological applications. Nanotechnological applications of BCPs are possible due to their physical properties related to mass and energy transport, as well as mechanical, electrical, and optical properties. These properties provide substantial benefits in nanostructure membranes, nanotemplates, photonic crystals, and high-density information storage media. In many applications, such nanopatterns need to be achieved as ordered and tunable structures. Consequently, the control of orientation of such structures with defect-free ordering on larger length scales still remain as major research challenge in many cases. In addition to their pure block forms, blends of copolymers with other polymers offer productive research areas in relation to nanostructural self-assembly. We prepared well-aligned nanocylinders into block copolymer over the enhanced sample area and scale of height without any external field applications or modification of interaction between the sample and the substrate. Self-assembled 3-dimensional perpendicular cylinder orientation was achieved mainly by blending of minority homopolymer into the blockcopolymer. Thus, this study investigated a spontaneous and simple method for the orientation of perpendicular cylinders in BCP/homopolymer mixtures on a preferential substrate, by increasing the interaction force between the homologous polymer pair at a fixed composition of minority block component. Since the thermodynamical changes have been simply accomplished by the control of incompatibility between the block components, the intrinsic advantages of block copolymer nanopatterning, such as fast and spontaneous 3-dimensional nanopatterning with a high thermodynamic stability and reproducibility, have been completely preserved in this fabrication strategy. By exploiting thermodynamical changes using temperature variation and by blending a homopolymer with well controlled molecular weight, we illustrated that redistribution of homopolymer resulted in a shift of phase boundaries and in the stabilization of well-ordered structures to create new opportunities for nanotechnologies.