Patternable Materials for Next-generation Lithography

Patternable Materials for Next-generation Lithography
Author: Austin Patrick Lane
Publisher:
Total Pages: 462
Release: 2017
Genre:
ISBN:


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One of the salient truths facing the microelectronics industry today is that photolithography tools are unable to meet the resolution requirements for manufacturing next-generation devices. In the past, circuit feature sizes have been minimized by reducing the exposure wavelength used for patterning. However, this strategy failed with the worldwide dereliction of 157 nm lithography in 2003. Extreme ultraviolet (EUV) lithography still faces many technical challenges and is not ready for high volume manufacturing. How will the microelectronics industry continue to innovate without regular advances in photopatterning technology? Regardless of which paradigm is adopted, new materials will probably be required to meet the specific challenges of scaling down feature sizes and satisfying the economic ultimatum of Moore’s Law. In the search for higher resolution patterning tools, device manufacturers have identified block copolymer (BCP) lithography as a possible technique for next-generation nanofabrication. BCP self-assembly offers access to sub-5 nm features in thin films, well beyond the resolution limits of photolithography. However, BCP materials must be carefully designed, synthesized, and processed to create lithographically interesting features with good etch resistance for pattern transfer. In this dissertation, we describe a pattern transfer process for 5 nm BCP lamellae and a directed self-assembly (DSA) process for aligning 5 nm structures in thin films. To achieve defect-free alignment, the interfacial interactions between the BCP and pre-patterned substrate must be precisely controlled. We also discuss a new process for selectively modifying oxidized chromium films using polymer brushes, which could further improve the aforesaid DSA process. To facilitate better pattern transfer of BCP structures, several new BCPs with “self-developing” blocks were synthesized and tested. These materials depolymerize and evaporate in strongly acidic environments, leading to developed BCP features without the need for etching or solvent. “Self-developing” polymers may also be useful materials for traditional photolithography. Chemically amplified resists used in manufacturing today are fundamentally limited by a trade-off between sensitivity and pattern quality. To overcome this problem, we present a new type of photoresist that relies on depolymerization, rather than catalysis, to achieve amplification without producing significant roughness or bias in the final pattern

Materials and Processes for Next Generation Lithography

Materials and Processes for Next Generation Lithography
Author:
Publisher: Elsevier
Total Pages: 636
Release: 2016-11-08
Genre: Science
ISBN: 0081003587


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As the requirements of the semiconductor industry have become more demanding in terms of resolution and speed it has been necessary to push photoresist materials far beyond the capabilities previously envisioned. Currently there is significant worldwide research effort in to so called Next Generation Lithography techniques such as EUV lithography and multibeam electron beam lithography. These developments in both the industrial and the academic lithography arenas have led to the proliferation of numerous novel approaches to resist chemistry and ingenious extensions of traditional photopolymers. Currently most texts in this area focus on either lithography with perhaps one or two chapters on resists, or on traditional resist materials with relatively little consideration of new approaches. This book therefore aims to bring together the worlds foremost resist development scientists from the various community to produce in one place a definitive description of the many approaches to lithography fabrication. Assembles up-to-date information from the world’s premier resist chemists and technique development lithographers on the properties and capabilities of the wide range of resist materials currently under investigation Includes information on processing and metrology techniques Brings together multiple approaches to litho pattern recording from academia and industry in one place

Advanced Materials for Next-Generation Lithography

Advanced Materials for Next-Generation Lithography
Author: Evan Lawrence Schwartz
Publisher:
Total Pages: 264
Release: 2011
Genre:
ISBN:


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The constant demand for increased circuit density and higher resolution patterning calls for simultaneous advancements in materials chemistry. A variety of possible approaches for next-generation lithography are explored, centering on the use of directly patternable self-assembling block copolymers, along with hafnium oxidebased nanoparticle photoresists. In one example of the first approach, a random copolymer brush layer of poly(styrene-ran-hydroxystyrene) was designed and synthesized to precisely tune the substrate/polymer surface energy for a lithographically patternable poly([alpha]methylstyrene-block-4-hydroxystyrene) (P[alpha]MS-b-PHOST) block copolymer. The surface was designed to avoid preferential wetting of either P[alpha]MS or PHOST domains to the substrate and orient the block copolymer domains vertically relative to the substrate. To neutralize the polymer/ vapor interface during solvent vapor processing, the film was exposed to a mixed solvent vapor of a defined polarity, creating vertical microdomains with long-range order. In the latter approach, hafnium oxide nanoparticles were covalently coated with a photo-reactive ligand, which allowed neighboring nanoparticles to form a crosslinked network upon exposure to ultraviolet light. The basic science of this new class of resist material is discussed. These negative-tone resists have so far demonstrated sub-50 nm resolution using 193nm interference lithography, and plasma etch resistance over thirteen times greater than PHOST under standard silicon etching conditions. In a combination of the two approaches, the co-assembly of the inorganic nanoparticles with the PHOST phase of P[alpha]MS-b-PHOST is shown. TEM and SAXS studies indicated the expansion of the microdomain periodicity upon nanoparticle incorporation. These block copolymer nanocomposite films offer enhanced functionality and a larger process window for subsequent pattern transfer into semiconductor substrates. In another example of co-assembly, phenolic molecular glass photoresists were blended with low molecular weight, triblock copolymer surfactants based on poly(ethylene oxide)(PEO). The miscibility of these blend components is shown to be a result of preferential hydrogen bonding between the hydroxyl groups attached to the molecular glass and the alkyl ether group of the PEO block, as shown by FTIR and DSC analysis. The blending resulted in an enhancement in segregation strength that led to the formation of sub-10nm self-assembled morphologies, as verified by SAXS. Options for the lithographic patterning of these blends are explored. Lastly, a combined additive and subtractive patterning technique is demonstrated that allows the deposition of multiple block copolymer films, of different domain sizes and pitches, on the same layer of the substrate. The approach used a semifluorinated negative-tone photoresist which is designed to resist intermixing when spin coated on top of a block copolymer film.

Small Molecule Photoresist Materials for Next Generation Lithography

Small Molecule Photoresist Materials for Next Generation Lithography
Author: Marie Elyse Krysak
Publisher:
Total Pages: 414
Release: 2013
Genre:
ISBN:


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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.

Solvent-based Development of Photoresists for Next-generation Lithography

Solvent-based Development of Photoresists for Next-generation Lithography
Author: Christine Y. Ouyang
Publisher:
Total Pages: 334
Release: 2013
Genre:
ISBN:


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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.

Materials and Processes for Advanced Lithography Applications

Materials and Processes for Advanced Lithography Applications
Author: Wei-Lun Kane Jen
Publisher:
Total Pages: 354
Release: 2009
Genre:
ISBN:


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Step and Flash Imprint Lithography (S-FIL) is a high resolution, next-generation lithography technique that uses an ambient temperature and low pressure process to replicate high resolution images in a UV-curable liquid material. Application of the S-FIL process in conjunction with multi-level imprint templates and new imprint materials enables one S-FIL step to reproduce the same structures that require two photolithography steps, thereby greatly reducing the number of patterning steps required for the copper, dual damascene process used to fabricate interconnect wirings in modern integrated circuits. Two approaches were explored for the implementation of S-FIL in the dual damascene process: sacrificial imprint materials and imprintable dielectric materials. Sacrificial imprint materials function as a pattern recording medium during S-FIL and a three-dimensional etch mask during the dielectric substrate etch, enabling the simultaneous patterning of both the via and metal structures in the dielectric substrate. Development of sacrificial imprint materials and the associated imprint and etch processes are described. Application of S-FIL and the sacrificial imprint material in a commercial copper dual damascene process successfully produced functional copper interconnect structures, demonstrating the feasibility of integrating multi-level S-FIL in the copper dual damascene process. Imprintable dielectric materials are designed to combine the multi-level patterning capability of S-FIL with novel dielectric precursor materials, enabling the simultaneous deposition and patterning of the interlayer dielectric material. Several candidate imprintable dielectric materials were evaluated: sol-gel, polyhedral oligomeric silsesquioxane (POSS) epoxide, POSS acrylate, POSS azide, and POSS thiol. POSS thiol shows the most promise as functional imprintable dielectric material, although additional work in the POSS thiol formulation and viscous dispense process are needed to produce functional interconnect structures. Integration of S-FIL with imprintable dielectric materials would enable further streamlining of the dual damascene fabrication process. The fabrication of electronic devices on flexible substrates represents an opportunity for the development of macroelectronics such as flexible displays and large area devices. Traditional optical lithography encounters alignment and overlay limitations when applied on flexible substrates. A thermally activated, dual-tone photoresist system and its associated etch process were developed to enable the simultaneous patterning of two device layers on a flexible substrate.

Microlithography

Microlithography
Author: Bruce W. Smith
Publisher: CRC Press
Total Pages: 770
Release: 2020-05-01
Genre: Technology & Engineering
ISBN: 1351643444


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The completely revised Third Edition to the bestselling Microlithography: Science and Technology provides a balanced treatment of theoretical and operational considerations, from fundamental principles to advanced topics of nanoscale lithography. The book is divided into chapters covering all important aspects related to the imaging, materials, and processes that have been necessary to drive semiconductor lithography toward nanometer-scale generations. Renowned experts from the world’s leading academic and industrial organizations have provided in-depth coverage of the technologies involved in optical, deep-ultraviolet (DUV), immersion, multiple patterning, extreme ultraviolet (EUV), maskless, nanoimprint, and directed self-assembly lithography, together with comprehensive descriptions of the advanced materials and processes involved. New in the Third Edition In addition to the full revision of existing chapters, this new Third Edition features coverage of the technologies that have emerged over the past several years, including multiple patterning lithography, design for manufacturing, design process technology co-optimization, maskless lithography, and directed self-assembly. New advances in lithography modeling are covered as well as fully updated information detailing the new technologies, systems, materials, and processes for optical UV, DUV, immersion, and EUV lithography. The Third Edition of Microlithography: Science and Technology authoritatively covers the science and engineering involved in the latest generations of microlithography and looks ahead to the future systems and technologies that will bring the next generations to fruition. Loaded with illustrations, equations, tables, and time-saving references to the most current technology, this book is the most comprehensive and reliable source for anyone, from student to seasoned professional, looking to better understand the complex world of microlithography science and technology.

MEMS Materials and Processes Handbook

MEMS Materials and Processes Handbook
Author: Reza Ghodssi
Publisher: Springer Science & Business Media
Total Pages: 1211
Release: 2011-03-18
Genre: Technology & Engineering
ISBN: 0387473181


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MEMs Materials and Processes Handbook" is a comprehensive reference for researchers searching for new materials, properties of known materials, or specific processes available for MEMS fabrication. The content is separated into distinct sections on "Materials" and "Processes". The extensive Material Selection Guide" and a "Material Database" guides the reader through the selection of appropriate materials for the required task at hand. The "Processes" section of the book is organized as a catalog of various microfabrication processes, each with a brief introduction to the technology, as well as examples of common uses in MEMs.