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As feature sizes continue to shrink, the need for new materials and new processes for next-generation lithography becomes more urgent. Although aqueous base development has been the industry standard for over twenty years, there are still several issues that need to be overcome. First, the high surface tension of aqueous base developers can lead to pattern collapse of high aspect ratio patterns and limit resolution. The toxicity of aqueous base developers has also raised concerns about the environment. In order to reduce the problems related to aqueous development, solvents or materials with desirable properties must be used. Recently, there has also been growing interest in solvent-based negative-tone development (NTD) due to its better performance in printing certain feature types. Therefore, solvent-based development of photoresists was investigated in this study. One approach to reduce the pattern collapse problem and environmental issues of the lithographic process is through the use of environmentally friendly solvents with low surface tension. Supercritical carbon dioxide (scCO2) and linear methyl siloxanes (LMS) are green solvents that have low toxicity, low surface tension, low viscosity and can be recycled. Solvent-based development of both polymeric and molecular glass resists with positive- and negative-tone images have been successfully demonstrated in both solvents. High-resolution and high aspect ratio patterns were obtained with no pattern collapse observed using both solvents. As there is little iii understanding about the solvent power of linear methyl siloxanes, the dissolution behavior of polymers and molecular glasses in linear methyl siloxanes was also studied. Besides using low surface tension developers to mitigate pattern collapse problem, another approach is by using materials with high etch resistance that eliminates the use of thick films. Also, because of the low intensity of current EUV light source, the next-generation resists need to demonstrate high sensitivity and optimum absorbance. Inorganic metal oxide nanoparticles based on zirconium oxide (ZrO2) and hafnium oxide (HfO2) with organic ligands have been synthesized for EUV lithography. These nanoparticle resists can be developed as negative-tone patterns using an organic solvent and high-resolution patterns were achieved. The patterning performance of these nanoparticles in different organic solvents was also evaluated. iv

Photolithography remains the most efficient method to create semiconductor devices. Moore's law states that the number of transistors per integrated circuit will double every four years. In order to successfully continue this trend of miniaturizing feature sizes, new, smaller sized patterning materials must be studied. Small molecule photoresists are being developed for high resolution patterning. Low molecular weight amorphous materials, or molecular glasses (MGs), have emerged as alternatives to polymeric resist materials. They combine the benefits of small molecular size with the favorable aspects of polymers, such as a high glass transition temperature (Tg) and the ability to form thin films. Inorganic-based nanoparticles are currently being explored as next generation photoresists. These materials are similar in architecture to MGs, but are comprised of an inorganic core that provides excellent thermal stability and resistance to plasma etching. This research focuses on the synthesis and characterization both MG and nanoparticle resist materials for high resolution patterning. The materials studied are designed for use with Extreme Ultraviolet Lithography (EUV-L), using a wavelength of 13.5 nm. This next-generation technique is believed to be the key to extending patterning capabilities to sub 30 nm and beyond. Small molecule resists materials have been specifically designed for use with alternative lithographic processing techniques. Small, rigid structures were designed for vapor deposition, which has been examined as an alternative to spin-coating. This process has been shown to deposit a uniform film, free from defects and impurities, without the use of solvent. Sub-millisecond laser heating is a relatively new technique that is studied as an alternative the post exposure bake. This method has shown the ability to reduce line edge roughness while simultaneously improving resist sensitivity. Systematically designed MG photoacid generators have been used to characterize the acid diffusion behavior during laser heating as compared to traditional hotplate heating. The development of resist materials for these new processes is a critical step in the preparation of these processes for widespread use in lithographic processing. ii

Polymers synthesized with a star-shaped architecture can exhibit properties that differ from linear polymers. This has led several industries to use star polymers in their products. The utility of star polymers is currently restricted to high molecular weight applications because it is difficult to reproducibly isolate well controlled, low molecular weight star polymers. Consequently, little is known about the properties or behavior of star polymers in the low molecular weight regime. In this work, low molecular star polymers are reproducibly prepared using atom transfer radical polymerization. From simple homopolymers to more complex terpolymer compositions, stars with different cores, numbers of arms and arm lengths are studied. The potential of star polymers as photoresists is investigated to demonstrate the ability of stars in an application that requires extremely low (sub-10 kg/mol) molecular weights. Lithographic performance is comprehensively examined over a range of processing conditions using combinatorial techniques. This study reveals that the conformation of star polymers can result in smoother lithographic features, addressing a key challenge facing the photoresist community.

Immersion lithography has emerged as the next technology to achieve the resolution improvement needed to produce smaller and faster microelectronic devices. It involves filling the air gap between the lens and photoresist-coated silicon wafer in a lithographic exposure tool with a higher refractive index medium. This improves the coupling of light into the resist and allows for better resolution. At the current exposure wavelength of 193 nm, water has been identified as the most promising immersion medium. Several potential issues had to be resolved before the process would be adopted. One was the unknown consequence of intimate contact between water and a photoresist. Any extraction of small molecule photoresist components by water could lead to a degradation of imaging performance and/or contamination. To address this, the possible extraction of several examples of these components from model 193 nm photoresists was studied by multiple experimental techniques including liquid chromatography/mass spectroscopy, scanning electrochemical microscopy and radiochemical analysis. It was found that both a photoacid generator and a base additive were extracted in small quantities. A study of the optical properties of water-based solutions with ionic additives was then undertaken. This study was intended to identify fluids with a higher index than water for greater resolution improvement. The solutions had higher index values, though typically with prohibitively high absorbance. The survey did lead to a series of methylsulfonate salts with some of the highest index values paired with low absorbance found for these materials. However, none of the target fluid properties were reached, so a theoretical approach was then used to model the properties of an ideal additive. This model served as a guide to identify a new type of additive with both a high index and low absorbance. The principles used for a high index/low absorbance additive were then applied to fabricate a polymer photonic device. A photonic crystal structure was designed for a polymer with an additive. A process for fabricating it was then developed using step and flash imprint lithography. The process development included a demonstration of a template created with a negative tone electron beam lithography process.

Immersion lithography has emerged as the next technology to achieve the resolution improvement needed to produce smaller and faster microelectronic devices. It involves filling the air gap between the lens and photoresist-coated silicon wafer in a lithographic exposure tool with a higher refractive index medium. This improves the coupling of light into the resist and allows for better resolution. At the current exposure wavelength of 193 nm, water has been identified as the most promising immersion medium. Several potential issues had to be resolved before the process would be adopted. One was the unknown consequence of intimate contact between water and a photoresist. Any extraction of small molecule photoresist components by water could lead to a degradation of imaging performance and/or contamination. To address this, the possible extraction of several examples of these components from model 193 nm photoresists was studied by multiple experimental techniques including liquid chromatography/mass spectroscopy, scanning electrochemical microscopy and radiochemical analysis. It was found that both a photoacid generator and a base additive were extracted in small quantities. A study of the optical properties of water-based solutions with ionic additives was then undertaken. This study was intended to identify fluids with a higher index than water for greater resolution improvement. The solutions had higher index values, though typically with prohibitively high absorbance. The survey did lead to a series of methylsulfonate salts with some of the highest index values paired with low absorbance found for these materials. However, none of the target fluid properties were reached, so a theoretical approach was then used to model the properties of an ideal additive. This model served as a guide to identify a new type of additive with both a high index and low absorbance. The principles used for a high index/low absorbance additive were then applied to fabricate a polymer photonic device. A photonic crystal structure was designed for a polymer with an additive. A process for fabricating it was then developed using step and flash imprint lithography. The process development included a demonstration of a template created with a negative tone electron beam lithography process.

The dimensional tolerances of photoresist features are now at the nanometer scale, where effects of individual molecules are important. In recognition of the industrial need for a molecular-scale understanding of photoresist performance, mechanistic models have been developed for each of the several photolithography processes that are used with positive-tone, chemically amplified photoresists: film creation, exposure, post exposure bake, and development. These models are based on experimental studies that have clarified details of photoresist function including the photochemical quantum efficiency of photoresist exposure, the reaction-diffusion properties of exposure photoproducts, and the complex dissolution behavior of phenolic homopolymers and copolymers in aqueous base. A dynamic Monte Carlo simulation has been developed to test the experimentally derived models and further examine the underlying physical processes relevant to photoresist patterning. This mesoscale simulation consists of distinct modules for each processing step, each of which captures the appropriate chemical and physical phenomena at the molecular scale. The several simulation modules have yielded results that are qualitatively correct for every major resist processing step. The inputs to the simulation are fundamental and measurable material and processing parameters and empirical calibrations are not required. The chemical detail included in the models enables investigation of the wide formulation variable space. Furthermore, the mesoscale nature of the simulation offers the unique ability to study the stochastic processes that contribute to resist feature roughness. This simulation thus provides a useful predictive tool to guide the rational design of new photoresist materials and the optimization of photolithography processes.

The dimensional tolerances of photoresist features are now at the nanometer scale, where effects of individual molecules are important. In recognition of the industrial need for a molecular-scale understanding of photoresist performance, mechanistic models have been developed for each of the several photolithography processes that are used with positive-tone, chemically amplified photoresists: film creation, exposure, post exposure bake, and development. These models are based on experimental studies that have clarified details of photoresist function including the photochemical quantum efficiency of photoresist exposure, the reaction-diffusion properties of exposure photoproducts, and the complex dissolution behavior of phenolic homopolymers and copolymers in aqueous base. A dynamic Monte Carlo simulation has been developed to test the experimentally derived models and further examine the underlying physical processes relevant to photoresist patterning. This mesoscale simulation consists of distinct modules for each processing step, each of which captures the appropriate chemical and physical phenomena at the molecular scale. The several simulation modules have yielded results that are qualitatively correct for every major resist processing step. The inputs to the simulation are fundamental and measurable material and processing parameters and empirical calibrations are not required. The chemical detail included in the models enables investigation of the wide formulation variable space. Furthermore, the mesoscale nature of the simulation offers the unique ability to study the stochastic processes that contribute to resist feature roughness. This simulation thus provides a useful predictive tool to guide the rational design of new photoresist materials and the optimization of photolithography processes.

An important goal of the microelectronics industry is to make new technological advances while keeping the cost of the fabrication process down. To achieve this goal, the microelectronics industry are presently placing more active devices on each chip, while at the same time trying to increase the number of successful chips per wafer. In order for the industry to successfully do this, they must reduce all of the dimensions in the circuit while trying to maintain its physical, chemical, and functional properties. These demands have made all steps of the fabrication process more critical. The scope of this project will encompass the development of exposed positive photoresist with an emphasis placed upon the effects of agitation on resist image quality.

The spectral sensitivity of KODAK Micro Positive Resist 820 has been determined for the spectral range of 300nm to 500nm. A xenon-source monochrometer was used in a hard contact exposing system. Se/isitivity is defined as the inverse of the exposure (mj/cm ) needed to produce an image in a photoresist coated plate having walls of 70 normal slope. Low intensity reciprocity law failure has been conclusively shown to exist in this resist with exposure intensities of 100 mw/cm and below. Guide lines have been drawn up, based on the procedures and results of the experimentation, to assist photoresist users in determining the spectral sensitivity of a photoresist. The feasibility of these procedures has been determined to be positive.

An experiment was run to determine the ability of surfactants to reduce or remove scum produced during development of a positive resist. Anionic, cationic and nonionic surfactants were added to a low metal ion developer at concentrations between 0.025% and 0.57o. The film thickness loss due to development was measured, and image profiles were observed with scanning electron micrographs . Of the surfactants tried, Aerasol OT-75 (dioctyl ester of sodium sulfosuccinic acid) produced the best results, 9.57o film thickness loss with little image profile change. However, the experiment was limited by processing condition variables.

The feasibility of photographic speed values for positive photoresist is evaluated. Speed is defined as the reciprocal of exposure necessary to produce a desired response. An outline of the microlithographic process, the chemistry of positive resist, and previous exposure models precede the experimental body of work to facilitate understanding of the photoresist system. The experimental method proposes a mathematical model describing the resist response to exposure. Photographic speed values result from this model. They are tested for sensitivity to process changes using Analysis of Variance. One speed definition is chosen as a possible standard and process control. It is based on the exposure required to produce a resist thickness of .4 microns above the under-lying substrate.

A procedure is established which will enable the study of contrast and sensitivity characteristics of electron-beam resist materials. The imaging system includes an electron beam-sensitive resist coating on an oxidized silicon substrate exposed with a scanning electron microscope (SEM) and developed in a suitable solvent. The results correlate with published data. A chemically amplified electron-beam resist imaging system is studied using a three level, three factor Box-Behnken design. The effects of postbake temperature, postbake time, and development time on contrast and sensitivity are presented.

A series of images of a AMI/RIT resolution mask was imaged at the following partial coherence values: 0.7, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, and 0.35. The line-width and slope of the 10 micron lines imaged at each particular partial coherence value was analyzed and evaluated. The slope of the developed photoresist sidewall improved significantly with a decrease in partial coherent illumination, except for the 0.7 to 0.65, range while the line-width decreased.

Collection of linewidth data is an important part of photoresist characterization. Linewidth data are usually collected by optical measurements or scanning electron microscopy. Both of these techniques are tedious and time-consuming. In this work, electrically measurable test structures are used to collect linewidth data. These structures use a measured sheet resistance, a known length of conducting material, and the measured resistance of the structure to determine the linewidth. The benefits of using these structures include completely automated data collection and the ability to collect statistically significant amounts of data. This allows the use of existing statistical analysis software to analyze and fit a model to the data. In this study, electrically testable linewidth structures are used in two photoresist characterization experiments to provide important process latitude information. The measured linewidth includes the effects of the photolithography and the subsequent etching step.

This thesis was performed to determine if low intensity reciprocity law -failure (RLF) exists in Kodak Micro Positive Resist B09 (KMPR 809) . At exposure irradiances at or below .44 mw/sq cm, it was observed that solublization of the photopolymer was incomplete, indicating that low-intensity RLF of the photosolubilization does exist. RLF was indicated by the formation of a "scum" layer over the exposed areas of the resist, the thickness of which increased with decreased irradiance. Mechanisms have been identified which may explain the RLF of the photoreaction. Confirmation of the proposed mechanisms could be the subject of another study. The RLF was expected to lead to proportional changes in the line width of the resist patterns, due to intensity differences in the shadow areas of the mask. Line width was found to be independent of irradiance and time of exposure, and the RLF was within the experimental error.