Zugl.: Zürich, Techn. Hochsch., Diss., 2008

Targeted radiotherapy (TRT) is a technique which allows for individual cancer cells to be targeted by radiation. However, there is variation in uptake at the whole body, organ, cellular and subcellular levels. This distribution affects the biological efficacy of the TRT agents. To address this problem, novel techniques have been developed and demonstrated. These aim to provide quantitative information about the spatial distribution of Auger electron (AE) emitting radiopharmaceuticals at the subcellular level. Two methods have been developed. The first, photoresist autoradiography (PAR), uses photoresists as an autoradiography substrate, and the second uses microautoradiography (MAR) and a transmission electron microscope (TEM). The techniques have been demonstrated using the AE emitter indium-111. Firstly, PAR is demonstrated using poly (methyl methacrylate) (PMMA). Photoresists were exposed to indium-111 which had been internalised into cells, and the photoresists were analysed using atomic force microscopy (AFM). The technique has a theoretical resolution in the nanometre range and was able to demonstrate cellular patterns on the micron scale. To gain quantitative information, the photoresist response (depth of pattern) was calibrated as a function of electron fluence and a model of the patterns was created. Combining the calibration data with the point source model allowed the position and intensity of the internalised source terms to be estimated using the PAR method. Secondly, a technique for electron microscope-microautoradiography (EM-MAR) was developed. The processing conditions of the MAR technique were determined and staining techniques developed, to produce high quality TEM micrographs. A time course experiment showed the distribution and variation in the uptake of the radiopharmaceutical at the cellular level. Both techniques are able to provide information about the subcellular distribution of the radioactivity at a higher resolution than current techniques. Both enable the collection of information which can be used in microdosimetric calculations.

No description available.

In this thesis, different approaches in synthesizing molecular resist are examined, and structure-property relations for the molecular resist properties are studied. This allows for design of resists that could be studied further as either negative or positive tone resists in photolithography. A series of compounds having different number of acrylate moiety, and different backbones were investigated for photoresist application. Thermal curing of acrylate compounds in organic solvent was also examined. Film shrinkage, as well as auto-polymerization was observed for these compounds that make them unsuitable as photoresist material. Furthermore, calix[4]resorcinarenes (C4MR) was chosen as backbone, and the functional groups was selected as oxetane and epoxy. Full functionalized C4MR compounds with oxetane, epoxy and allyl were synthesized. Variable-temperature NMR of C4MR-8Allyl was studied in order to get a better understanding of the structure’s conformers. Energy barrier of exchange (ΔG#) was determined from coalescence temperatures, and was 57.4 KJ/mol for aromatic and vinyl hydrogens and 62.1 KJ/mol for allylic hydrogens.

No description available.

No description available.

Each new generation of integrated circuits and other nano-structured devices is produced at ever decreasing length scales. The extension of conventional liquid-phase processes for the manufacturing of these devices is uncertain. This work investigates the ability of liquids to wet nanoscale features. A model for wetting time is derived that may be used to identify those geometries for which wetting is critical. Conditions under which wetting time is significant may result in low yield and poor uniformity, and may require alternate-phase processing. Furthermore, the dependence of wetting time on the properties of the fluid are quantified so that fluids may be designed to have optimal properties and thus optimal performance for wetting. The resulting model can be used as a tool to predict future processing requirements, and when necessary, to design novel processes implementing alternative phase fluids such as gas-expanded liquids (GXLs). This study also quantitatively predicts specific effects associated with modified transport properties for dissolution and transport in nanoscale features. The use of GXLs is a particularly promising alternative to conventional liquid-phase processes. GXLs have superior mass transport properties relative to liquids, but can maintain the solvent strength necessary for IC process steps such as post-etch residue removal and photoresist stripping. In addition, the environmental benefits associated with CO2-based processes can be substantial. Conceptual demonstration of the use of carbon dioxide (CO2)-expanded liquids for photoresist and residue removal has been performed. GXLs containing up to 75% CO2 are equally as effective as the pure solvents for removal of PHOST-based films. These experiments indicate that GXLs have potential applications in photoresist stripping and post-etch residue removal, in which cost savings due to reduced solvent use can be substantial. The removal of films with GXLs has been evaluated primarily with x-ray photoelectron spectroscopy (XPS). Additionally, an in situ optical technique has been developed for film and GXL diagnostics. This technique has been used to evaluate the response of PHOST-based thin films to GXLs and to monitor density changes of liquids upon gas expansion.

The achievement of thermally stable second-order nonlinear optical (NLO) coefficients in polymers is an important but elusive goal in obtaining useful materials for commercial devices. In order to demonstrate the effect of photocrosslinkable groups on enhancement of stability of NLO properties, a series of NLO polymers were investigated, which contain side-chain NLO chromophores with a variable number of crosslinkable methacrylate groups attached to the chromophore opposite the main chain attachment point. Following electric field poling, polymers were crosslinked by irradiating polymer samples containing a photoinitiator. Decay of second-order NLO properties was measured by second harmonic generation (SHG), and stability of SHG coefficients was significantly enhanced after photocrosslinking for polymers containing multiple crosslinkable groups on the chromophore. Addition of reactive diluents further enhanced stability. The enhancement of thermal stability demonstrates the efficacy of photocrosslinking and suggests that the stability improvements may carry over to systems with more efficient chromophores and more stable polymer backbones. The addition of photocrosslinkable materials is also exploited in photoresists to mitigate alignment limitations on flexible substrates during photolithographic patterning by enabling imaging of two device layers in a single lithographic exposure. To facilitate the simultaneous patterning of two device layers, a new photoresist system was developed which is able to store and transfer two images concurrently. The dual-tone photoresist system has the ability to store two independent latent images, distinguished by the incident exposure light wavelength, while remaining compatible with reactive ion etch image transfer processes. A modified chemically amplified photoresist for 193 nm lithography containing an added photobase generator (PBG) leads to a dual-threshold behavior of the dissolution vs. dose contrast curve that enables pitch division of patterned images. To improve these resists, a study of resist components’ effects on line edge roughness and pitch division process windows was performed. The kinetics of two-stage PBGs are compared to single-stage PBGs with a view toward achieving higher acid latent image gradients at the line edge. Application of nuclear magnetic resonance spectroscopy to determine the rate constants for resist components in thin films is demonstrated and discussed as a tool for formulating dual-threshold resists. / text

Current metrology methods involve technicians viewing through a microscope, increasing the time, cost, and error rate in inspection. Developing an automated inspection system eliminates these difficulties. Shown in this work is a laser scanning microscope (LSM) design for an opto-electronic detection system (OEDS), based upon the concept that intensity differences related to pattern defects can be obtained from reflections off fused silica samples coated with photoresist (PR) or Aluminum. Development of this system for data collection and processing is discussed. Results show that 2.1 μm resolution of these defects is obtainable. Preliminary results for larger-array patterns through stitching processes are also shown. The second part of this work uses the concept of phase contrast edge detection. Looking at non-metallized patterns, one can use the property that phase changes induced by a refractive-index sensitive material can be seen with a multi-cell array, rendering the image visible by comparing the respective phases. A variety of defects and samples are shown. Extrapolating results to larger arrays is also discussed. Latent imaging, or imaging without development, is also evaluated. Future work in the areas of system commercialization, sample storage, and other mass-printing techniques are discussed.

Chapter 1 provides an overview of the current literature regarding molecular level modification of conducting surfaces. The modification of carbon surfaces are discussed, with particular attention being given to the use of aryldiazonium salt compounds. Patterning of molecular layers using aryldiazonium salts and arylazides is detailed. The objectives of the project are outlined. Chapter 2 contains the general experimental methods, instrumentation, chemicals, and materials used throughout this thesis. Chapter 3 details the development of two technical methods: a heat treatment method for regenerating diazonium-modified or deactivated pyrolysed photoresist film electrodes, and a method for preparing evaporated carbon film electrodes. Although regeneration of the evaporated carbon surfaces was unsuccessful, the surfaces exhibited good electrochemical properties and are useful substrates for studying diazonium-derived films. Chapter 4 reports the covalent modification of carbon, gold, and indium tin oxide surfaces with thin porphyrin films via the electrochemical reduction of porphyrin aryldiazonium salts. Surface characterisation studies revealed that the films are stably-attached and exhibit well-defined redox and optical properties. Chapter 5 describes the preparation and patterning of organic films on carbon and silicon surfaces using arylazides combined with photolithography. Strategies were investigated to generate continuous mixed films and surfaces presenting patterns of one or two components. For all grafted surfaces, the reactivity of tether species was confirmed by coupling electroactive targets or gold nanoparticles to the tethers, followed by electrochemical analysis or surface microscopy. Chapter 6 details the modification of carbon surfaces with diazonium-derived films via aryltriazenes. Also described in this chapter is the development of microfluidics, for use with aryltriazene and aryldiazonium salt solutions, for generating parallel surface patterns. Chapter 7 concludes and answers to the challenges reported in this study. Future directions are briefly discussed.