The chemical waste generated in today's microelectronic fabrication process can be released i... moreThe chemical waste generated in today's microelectronic fabrication process can be released into the environment and cause environmental and health concerns. It is therefore necessary to develop an environmentally friendly process that can eliminate the use of toxic chemical solvents. Silicone fluids are linear methyl siloxanes that only contain carbon, hydrogen, oxygen and silicon. They are low in toxicity, not ozone-depleting and contribute little to global warming. They degrade into naturally occurring compounds instead of accumulating in the atmosphere and can be recycled. Their unique physical and chemical properties have also made them promising developers for lithography. For example, their low surface tension can eliminate pattern collapse problems associated with high aspect-ratio features. Silicone fluids are non-polar solvents and their solvent strength is weaker than that of saturated hydrocarbons but stronger than that of the commercially available saturated hydrofluorocarbons and may be enhanced by adding other solvents. Two conventional photoresists used in this study, PBOCST and ESCAP are both insoluble in silicone fluids before or after exposure. However, the solubility of PBOCST and ESCAP in silicone fluids can be increased by using a silicon-containing additive. In this paper, we demonstrate this novel and environmentally friendly development of conventional photoresists in silicone fluids.

High-sensitivity material systems for two-photon three dimensional microfabrication

Proceedings of SPIE, Jan 24, 2004

A photoacid generator (PAG) is described that can be efficiently activated by two-photon excitati... moreA photoacid generator (PAG) is described that can be efficiently activated by two-photon excitation and can be used for high-sensitivity three-dimensional micro-patterning of acid-sensitive media. The molecule has been specifically engineered to have both a large peak two-photon absorption cross section (delta = 690 x 10-50 cm4 s photon-1 at 705 nm) and a high quantum yield for the photochemical

Research paper thumbnail of Solvent development processing of chemically amplified resists: chemistry, physics, and polymer science considerations

Solvent development processing of chemically amplified resists: chemistry, physics, and polymer science considerations

Proceedings of SPIE, Mar 17, 2011

Solvent development of chemically amplified (CA), negative tone photoresists depends on several f... moreSolvent development of chemically amplified (CA), negative tone photoresists depends on several factors including molecular weight of the photoresist, the strength of polymer-solvent interactions, and the strength of polymer-polymer interactions in the undeveloped regions. Absent are the ionic interactions present in the aqueous base development of CA resists that greatly aids dissolution and image contrast. In its place, strong hydrogen

Nanopatterning with tailored molecules

Proceedings of SPIE, Mar 27, 2014

ABSTRACT Star block copolymer synthesis was performed in a controlled fashion by an in-situ core ... moreABSTRACT Star block copolymer synthesis was performed in a controlled fashion by an in-situ core first ATRP route. The obtained resist materials on the basis of industrial used monomers with tailored star block copolymer architecture were systematically characterized and patterned. In dissolution investigations an excellent dissolution contrast between exposed and unexposed state was identified for this new resist material type. Additionally, the materials show an excellent sensitivity, which surpass the reference linear copolymer by a factor of eight. By a combinatorial resist optimization realized high resolution features are presented. Finally, preliminary results utilizing a further improved resist material design are shown.

Understanding of PS-b-PMMA phase segregation under laser-induced millisecond thermal annealing

Proceedings of SPIE, Mar 19, 2015

Laser thermal annealing of PS-b-PMMA is shown to modify phase segregation within the milliseconds... moreLaser thermal annealing of PS-b-PMMA is shown to modify phase segregation within the milliseconds timeframe at temperatures from the glass transition to far above the order-disorder transition temperature. We report the kinetics of phase segregation of cylinder forming PS-b-PMMA (53.8 kg/mol, fPS = 0.7) as probed by micro-beam grazing incidence small angle X-ray scattering. Structure evolution was probed as a function of peak temperature, time at temperature, and quench rate, with phase segregation readily occurring on millisecond time scales and at peak quench rates up to 107 K/s. The final film morphology is dependent on both the anneal time and the quench rate to ambient. With heating to sufficiently high temperatures, the thermal history is erased yielding a final state is purely dependent on the quench rate.

Development of an inorganic nanoparticle photoresist for EUV, e-beam, and 193nm lithography

Proceedings of SPIE, Mar 17, 2011

We have developed a transparent, high refractive index inorganic photoresist with significantly h... moreWe have developed a transparent, high refractive index inorganic photoresist with significantly higher etch resistance than even the most robust polymeric resist. As feature sizes continue to decrease, film thickness must be reduced in order to prevent pattern ...

Surface self assembly in side chain modified block copolymers

Control and Suppression of Surface Relief Gratings in Liquid-Crystalline Perfluoroalkyl–Azobenzene Polymers

Advanced Functional Materials, Aug 4, 2006

Azobenzene-functionalized polymers are potentially useful as materials for reversible optical inf... moreAzobenzene-functionalized polymers are potentially useful as materials for reversible optical information storage,[1,2] non-linear optical devices,[3] and photoswitchable liquid-crystal alignment.[4] In 1995, two research groups, the Natansohn[5] and the Tripathy groups,[6] ...

Environmentally friendly patterning of thin films in linear methyl siloxanes

Journal of Materials Chemistry, 2012

A number of green solvents have been explored to reduce the environmental impact of many chemical... moreA number of green solvents have been explored to reduce the environmental impact of many chemical processes. Among them, linear methyl siloxanes make up a class of solvents that are low in toxicity, VOC exempt and not ozone-depleting. In addition, their unique physical properties such as low surface tension and low viscosity can mitigate several issues encountered with conventional processing solvents. In order to understand the behavior of linear methyl siloxanes as processing solvents, the solubilities of polymers and small molecular glasses are studied in this work. Using lithography as a test of solubility differences, we have successfully shown patterning of thin films in linear methyl siloxanes thereby demonstrating their utility in processing organic systems.

Chemically Amplified Positive Resists for Two-Photon Three-Dimensional Microfabrication

Advanced Materials, Mar 17, 2003

... J. E 2002, 8, 347. [21] R. Seemann, S. Herminghaus, K. Jacobs, Phys. ... Chemically Amplified... more... J. E 2002, 8, 347. [21] R. Seemann, S. Herminghaus, K. Jacobs, Phys. ... Chemically Amplified Positive Resists for Two-Photon Three-Dimensional Microfabrication** By Tianyue Yu, Christopher K. Ober,* Stephen M. Kuebler, Wenhui Zhou, Seth R. Marder,* and Joseph W. Perry* ...

Materials for biosurfaces

Journal of Materials Chemistry, 2012

Kinetics of Block Copolymer Phase Segregation during Sub-millisecond Transient Thermal Annealing

Macromolecules, Aug 22, 2016

Millisecond thermal anneals were achieved by scanning a line-focused continuous wave CO 2 laser (... moreMillisecond thermal anneals were achieved by scanning a line-focused continuous wave CO 2 laser (λ=10.6 µm, ∼90 µm by 500 µm FWHM focus) as shown in Figure S1a. Figure S1b schematically shows the µ-GISAXS measurement geometry relative to the LSA spatial temperature profile. Example measured time-temperature profiles for 10 ms and 250 µs LSA anneals to a peak temperature of 500 • C are shown in Figure S1c. The LSA anneal duration is measured by the characteristic laser dwell time, τ , defined as the beam FWHM in the

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Molecular glass resists for next generation lithography

Proceedings of SPIE, Mar 14, 2008

The idea of using small molecules instead of polymers for next generation lithography may enable ... moreThe idea of using small molecules instead of polymers for next generation lithography may enable improved resolution and line edge roughness (LER). Rather than using polymeric materials we are focusing on a new class of materials known as molecular glasses (MGs). These are low molecular weight organic materials that demonstrate high glass transition temperatures despite their modest size. Unlike polymeric

Laser Spike Annealing of DSA Photoresists

Journal of Photopolymer Science and Technology, 2015

The thermodynamic mismatch of different segments in a block copolymer drives microphase separatio... moreThe thermodynamic mismatch of different segments in a block copolymer drives microphase separation, while their covalent bonds limit the phase separated domains to the nanometer scale. As a result, densely arranged high resolution patterns, the goal of lithography, form a thermodynamically preferred equilibrium state for block copolymers. For production new annealing methods are being explored to speed up and improve structure formation. Solvent vapor annealing is a powerful technique to control the ordering process and the morphology of block copolymers by selectively or non-selectively swelling polymers. In recent years high are attracting more and more attention due to their potential to form small s using solvent vapor or increased temperature to enhance the polymer chain mobility is a key to increase ordering rate. In this paper, we review recent work on using solvent annealing to control the morphology and report high speed laser annealing of high for lithographic applications.

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Lithographic Patterning with Block Copolymers

Journal of Photopolymer Science and Technology, 2003

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Research paper thumbnail of The role of hydrogels with tethered acetylcholine functionality on the adhesion and viability of hippocampal neurons and glial cells

The role of hydrogels with tethered acetylcholine functionality on the adhesion and viability of hippocampal neurons and glial cells

Biomaterials, Mar 1, 2012

In neural tissue engineering, designing materials with the right chemical cues is crucial in prov... moreIn neural tissue engineering, designing materials with the right chemical cues is crucial in providing a permissive microenvironment to encourage and guide neuronal cell attachment and differentiation. Modifying synthetic hydrogels with biologically active molecules has become an increasingly important route in this field to provide a successful biomaterial and cell interaction. This study presents a strategy of using the monomer 2-methacryloxyethyl trimethylammonium chloride (MAETAC) to provide tethered neurotransmitter acetylcholine-like functionality with a complete 2-acetoxy-N,N,N-trimethylethanaminium segment, thereby modifying the properties of commonly used, non-adhesive PEG-based hydrogels. The effect of the functional monomer concentration on the physical properties of the hydrogels was systematically studied, and the resulting hydrogels were also evaluated for mice hippocampal neural cell attachment and growth. Results from this study showed that MAETAC in the hydrogels promotes neuronal cell attachment and differentiation in a concentration-dependent manner, different proportions of MAETAC monomer in the reaction mixture produce hydrogels with different porous structures, swollen states, and mechanical strengths. Growth of mice hippocampal cells cultured on the hydrogels showed differences in number, length of processes and exhibited different survival rates. Our results indicate that chemical composition of the biomaterials is a key factor in neural cell attachment and growth, and integration of the appropriate amount of tethered neurotransmitter functionalities can be a simple and effective way to optimize existing biomaterials for neuronal tissue engineering applications.

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Research paper thumbnail of Chemical reaction and diffusion kinetics during laser-induced submillisecond heating for lithographic applications

Chemical reaction and diffusion kinetics during laser-induced submillisecond heating for lithographic applications

Journal of vacuum science and technology, Jun 5, 2019

Reactions in solid-state chemistry are controlled by both underlying chemical reaction rates and ... moreReactions in solid-state chemistry are controlled by both underlying chemical reaction rates and temperature-dependent diffusion of reactants and products. Due to distinctly different activation energies, the relative rates of reaction and diffusion may shift dramatically with temperature. In this work, the acid catalyzed deprotection of acid labile groups of model chemically amplified photopolymers was studied to understand the effects of temperature on diffusioncoupled reactions. In these systems, strong acids form during exposure of photoacid generators (PAGs) to ultraviolet radiation and then diffuse and catalyze deprotection reactions. By using very short duration laser-induced heating for the postexposure bake step, the potential reaction temperature range is extended by several hundred degrees compared to traditional thermal processing temperatures. Thermal degradation at these temperatures is avoided by simultaneously reducing the heating time from minutes to submilliseconds. Both diffusion and reaction rates were measured in this high temperature region for three different photoresists combined with two different PAGs, with activation energies of the key processes determined. The interplay of diffusion and reaction rates was also examined by comparing results of high-resolution pattern formation. The best image formation at high temperature was achieved using photoresists with high deprotection rates combined with PAGs exhibiting low diffusivity.

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Oxide Nanoparticle EUV (ONE) Photoresists: Current Understanding of the Unusual Patterning Mechanism

Journal of Photopolymer Science and Technology, 2015

In the past few years, industry has made significant progress to deliver a stable high power EUV ... moreIn the past few years, industry has made significant progress to deliver a stable high power EUV scanner and a 100 W light source is now being tested on the manufacuring scale. The success of a high power EUV source demands a fast and high resolution EUV resist. However, chemcially amplied resists encounter unprecedented challenges beyond the 22 nm node due to resolution, roughness and sensitivity tradeoffs. Unless novel solutions for EUV resists are proposed and further optimzed, breakthroughs can hardly be achieved. Oxide nanoparticle EUV (ONE) resists stablized by organic ligands were originally proposed by Ober et al. Recently this work attracts more and more attention due to its extraordinanry EUV sensitivity. This new class of photoresist utilizes ligand cleavage with a ligand exchange mechanism to switch its solubilty for dual-tone patterning. Therefore, ligand selection of the nanoparticles is extremely important to its EUV performance.

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New developments in ligand-stabilized metal oxide nanoparticle photoresists for EUV lithography

SPIE Proceedings, 2015

The introduction of EUV lithography to manufacturing requires the development of both new EUV exp... moreThe introduction of EUV lithography to manufacturing requires the development of both new EUV exposure tools and photoresists. The main challenges for photoresists are to achieve high resolution, and low roughness patterning at very high sensitivity given the limited intensity of current sources. A new class of photoresist formed from ligand-stabilized metal oxide nanoparticles shows extraordinary sensitivity for EUV lithography. These nanoparticles are processed in traditional organic solvents for both deposition and development as negative tone resist; positive tone images are possible if the aqueous base developer is used in addition to a post-exposure bake step. This paper presents new developments in the study of ligand-stabilized nanoparticle photoresists for EUV lithography. It is our current understanding that a key aspect of the solubility change of these photoresists during exposure involves ligand displacement by anions generated from photoactive compounds such as sulfonic acid photoacid generators. Both positive and negative tone patterning are possible and depend on thermal treatment history and choice of developer. On the basis of a non-chemically amplified ligand exchange mechanism, new resist structures were created. Both aromatic and aliphatic carboxylic acids with different functional groups have been studied in the formation of the nanoparticles and include dimethylacrylic acid, isobutyric acid, toluic acid. It has been shown that those nanoparticles with higher binding affinity ligands show better resolution and line edge roughness under EUV exposure. Some formulations demonstrate EUV sensitivity as high as 1.4 mJ/cm2, while other formulations demonstrate that improved LER values of 3-5nm. The overall resolution, sensitivity and roughness tradeoff has been evaluated and provides an understanding of structure - property relationships. In this paper, we also discuss major efforts on the further understanding of the patterning mechanism. By testing the dissolution rate and plotting it in Hansen interaction triangles, we can compare the differences between different formulations and choose a suitable developer for each formulation. We also used the dissolution rate study to confirm the important role of PAG and ligand exchange for pattern formation. In addition, aspects of the EHS properties of these new photoresists have been investigated and will be discussed.

Systematic study of ligand structures of metal oxide EUV nanoparticle photoresists

SPIE Proceedings, 2015

Ligand stabilized metal oxide nanoparticle resists are promising candidates for EUV lithography d... moreLigand stabilized metal oxide nanoparticle resists are promising candidates for EUV lithography due to their high sensitivity for high-resolution patterning and high etching resistance. As ligand exchange is responsible for the patterning mechanism, we systematically studied the influence of ligand structures of metal oxide EUV nanoparticles on their sensitivity and dissolution behavior. ZrO2 nanoparticles were protected with various aromatic ligands with electron withdrawing and electron donating groups. These nanoparticles have lower sensitivity compared to those with aliphatic ligands suggesting the structures of these ligands is more important than their pka on resist sensitivity. The influence of ligand structure was further studied by comparing the nanoparticles’ solubility for a single type ligand to mixtures of ligands. The mixture of nanoparticles showed improved pattern quality.

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