Extending the resolution limits of nanoshape imprint lithography using molecular dynamics of polymer crosslinking (original) (raw)
Polymer Imprint Lithography with Molecular-Scale Resolution
Nano Letters, 2004
We show that small diameter, single-walled carbon nanotubes can serve as templates for performing polymer imprint lithography with feature sizes as small as 2 nm − comparable to the size of an individual molecule. The angstrom level uniformity in the critical dimensions of the features provided by this unusual type of template provides a unique ability to investigate systematically the resolution of imprint lithography at this molecular scale. Collective results of experiments with several polymer formulations for the molds and the molded materials suggest that the density of cross-links is an important molecular parameter that influences the ultimate resolution in this process. Optimized materials enable reliable, repetitive patterning in this single nanometer range.
Processing dependent behavior of soft imprint lithography on the 1-10-nm scale
IEEE Transactions on Nanotechnology, 2006
This paper examines aspects of a soft nanoimprint lithography technique for operation at resolutions that approach the 1-nm regime. Systematic studies using polymer molds made with single walled carbon nanotubes (diameters between 0.5 and 5 nm) and high-resolution electron beam patterned layers of hydrogen silsesquioxane (line widths and heights 10 and 20 nm, respectively) as templates reveal a dependence of the resolution limits on the polymer processing conditions. In particular, using a single choice of polymers for the molds and the molded materials, imprint results show that the conditions for spin casting and curing the polymers determine, to a large degree, the resolution and replication fidelity that can be achieved. Optimized procedures enable imprinted polymer surfaces that have a root mean squared surface roughness of 0.26 nm or lower and a resolution as high as 1 nm. These characteristics are significantly better than previous results obtained using these same polymers with unoptimized conditions. A diversity of molded polymers, including Bisphenol-F epoxy resin, polyacrylic acid, and polyurethane, show similar high-fidelity imprinting capabilities. Different procedures enable accurate relief replication for features with modest aspect ratios and dimensions of 10 nm. The results indicate that choice of processing conditions is, in addition to materials selections, extremely important in achieving high-fidelity soft nanoimprint lithography in the 1-10-nm regime.
3D Simulation of Nano-Imprint Lithography
Nanoscale Research Letters, 2010
A proof of concept study of the feasibility of fully three-dimensional (3D) time-dependent simulation of nano-imprint lithography of polymer melt, where the polymer is treated as a structured liquid, has been presented. Considering the flow physics of the polymer as a structured liquid, we have followed the line initiated by de Gennes, using a Molecular Stress Function model of the Doi and Edwards type. We have used a 3D Lagrangian Galerkin finite element methods implemented on a parallel computer architecture. In a Lagrangian techniques, the node point follows the particle movement, allowing for the movement of free surfaces or interfaces. We have extended the method to handle the dynamic movement of the contact line between the polymer melt and stamp during mold filling.
Nano patterning and Nanoimprint lithography [NIL] has advanced to great heights in recent years. Customizing the surface at micro and nano scale is of great demand. It facilitates the handling and working at micro and nano scale level. Its applications towards medical field are growing day by day. Precise surface patterning with nanometer resolution has great potential in many medical and biological applications. It also provides a platform for fundamental studies of molecular and cell biology. This review article comprises of current trends and future scope of nano patterning and NIL. In this article we particularly focus on biological applications.
Recent Advances in Nano Patterning and Nano Imprint Lithography for Biological Applications
Procedia Engineering, 2014
Nano patterning and Nanoimprint lithography [NIL] has advanced to great heights in recent years. Customizing the surface at micro and nano scale is of great demand. It facilitates the handling and working at micro and nano scale level. Its applications towards medical field are growing day by day. Precise surface patterning with nanometer resolution has great potential in many medical and biological applications. It also provides a platform for fundamental studies of molecular and cell biology. This review article comprises of current trends and future scope of nano patterning and NIL. In this article we particularly focus on biological applications.
Step and Flash Imprint Lithography: An Efficient Nanoscale Printing Technology
Journal of Photopolymer Science and Technology, 2002
The goal of the SFIL development program is to enable patterning of sub-100 nm features at room temperature and with minimal applied pressure. We believe the use of low viscosity materials and photopolymerization chemistry will enable SFIL to achieve the throughput required for use in the microelectronics industry. Additionally, the rigid transparent imprint template used in SFIL enables a precision in overlay alignment that is difficult to achieve in other imprint schemes. Previous work demonstrated the ability to use SFIL to pattern over existing topography, to pattern on curved surfaces, and to produce working simple optical devices. Studies of defectivity have not revealed significant defect generation, and in fact have revealed no catastrophic defect propagation. Recent work has focused on improving etching processes used to amplify the aspect ratio of the polymer features. With this recent work we have demonstrated polymer-on-Si semi-dense lines smaller than 50 nm made with the SFIL process.
Improved step and flash imprint lithography templates for nanofabrication
Microelectronic Engineering, 2003
Step and flash imprint lithography (SFIL) is an attractive method for printing sub-100 nm geometries. Relative to other imprinting processes, SFIL has the advantage that the template is transparent, thereby facilitating conventional overlay techniques. In addition, the imprint process is performed at low pressures and room temperature, which minimizes magnification and distortion errors. Several different methods for fabricating templates are presented in this study. One scheme addresses some of the weaknesses associated with a solid glass substrate by incorporating a conductive and transparent layer of indium tin oxide (ITO) on the surface of the substrate. Features are defined on the templates by patterning a thin layer of PECVD oxide that is deposited on the ITO layer. A second method bypasses the oxide etch process by imaging a thin layer of hydrogen silsesquioxane (HSQ). By using a combination of these two methods, it is also possible to form multi-tiered structures on a template. Templates with features as small as 20 nm have been fabricated using the methods described above. The templates were then used to imprint patterns on 200 mm silicon wafers. It appears that any feature defined in the template is faithfully replicated on the wafer.
Curvature-Adjustable Polymeric Nanolens Fabrication Using UV-Controlled Nanoimprint Lithography
Micromachines, 2022
Nanolenses are gaining importance in nanotechnology, but their challenging fabrication is thwarting their wider adoption. Of particular challenge is facile control of the lens' curvature. In this work, we demonstrate a new nanoimprinting technique capable of realizing polymeric nanolenses in which the nanolens' curvature is optically controlled by the ultraviolet (UV) dose at the pre-curing step. Our results reveal a regime in which the nanolens' height changes linearly with the UV dose. Computational modeling further uncovers that the polymer undergoes highly nonlinear dynamics during the UV-controlled nanoimprinting process. Both the technique and the process model will greatly advance nanoscale science and manufacturing technology.
Controlling imprint distortions in step-and-flash imprint lithography
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2004
Step-and-Flash Imprint Lithography (S-FIL™) is a one-to-one imprinting process in which features are transferred from a template by lowering it onto a low-viscosity, photocurable, monomer solution that conforms to the template surface and is subsequently cured. The potential exists for both low cost and high throughput, making S-FIL a promising candidate for Next-Generation Lithography. However, there are many challenges that must be overcome in order to ensure the future viability of S-FIL. Mechanical distortion control is one of the principal challenges, and is addressed in this article. During the imprinting process, the viscous flow of the monomer liquid causes a significant pressure elevation within the fluid as it is forced to flow outwards through a small gap. These pressures cause out-of-plane distortions and in-plane distortions (OPD and IPD) of the template, which may be manifested as errors in the replicated pattern. A fluid-structure model was developed to predict the te...
Geometrical properties of multilayer nano-imprint-lithography molds for optical applications
Microelectronic Engineering, 2012
The functionality of micro-and nano-optical devices can be increased by using three-dimensional structures instead of two-dimensional ones. This paper reports on a fabrication method for nano-imprint lithography molds for planar optical applications which exhibit two different height levels with large pattern diversity as various lithographic technologies can be applied. To ensure a proper operation of optical elements as waveguides, a precise control of the feature dimensions is essential. The lateral and depth resolution as well as the alignment of two structure height levels have been investigated. The results show the feasibility of the process to obtain single-mode operating waveguides and micro-ring resonator structures for sensor applications. The replication of these structures has been performed in a UV-curable polymer. A residual layer could be avoided using non-wetting perfluoropolyether polymer molds cast from the original ones used in a reverse nano-imprint setup.
Microelectronic Engineering, 2008
A formulation including dissolved phosphorescent iridium complex has been synthesised as a resist for step and flash imprint lithography (S-FIL TM ). Functional properties of the resist after curing are demonstrated and structures as small as 50 nm have been successfully imprinted with this material onto a 4 in. silicon wafer. Fluorescent microscopy images demonstrate increased fluorescent signals where arrays of nano structures are imprinted. This technique of direct imprinting of functional materials could potentially lead to rapid, high throughput and low-cost fabrication of nanoscale organic devices and circuits.
High‐Speed Roll‐to‐Roll Nanoimprint Lithography on Flexible Plastic Substrates
Advanced materials, 2008
Continuous Roll-to-Roll NanoImprint Lithography (R2RNIL) provides greatly improved throughput by overcoming the challenges faced by conventional NIL in maintaining pressure uniformity and successful large-area imprinting and demolding. We present continuous imprinting of nanoscale structures with linewidth down to 70nm on a flexible plastic substrate. Our new process used a flexible and non-sticking fluoropolymer mold, and fast thermal and UV curable liquid resist materials. In addition, pattern quality in continuous R2RNIL process according to two different mold-separation directions has been analytically investigated.
Large area nanoimprint by substrate conformal imprint lithography (SCIL)
Advanced Optical Technologies
Releasing the potential of advanced material properties by controlled structuring materials on sub-100-nm length scales for applications such as integrated circuits, nano-photonics, (bio-)sensors, lasers, optical security, etc. requires new technology to fabricate nano-patterns on large areas (from cm
Recent Advances in Step-and-flash Imprint Lithography
Interface, 2002
The goal of the Step and Flash Imprint Lithography (SFIL) development program is to enable patterning of sub-100 nm features in a manner that has dramatic cost savings over conventional projection lithography techniques. The SFIL process is performed at room temperature and with minimal applied pressure, and we believe the use of low viscosity materials and photopolymerization chemistry will enable SFIL to achieve the throughput required for use in the microelectronics industry. Additionally, the rigid transparent imprint template used in SFIL enables a precision in overlay alignment that is difficult to achieve in other imprint schemes. This paper presents recent work that has focused on improving the resolution of the etch barrier formulation, modeling the free radical polymerization reaction to include oxygen inhibition, and improving the etching processes used to amplify the aspect ratio of the polymer features. Replacing the silylated crosslinker component in the etch barrier with ethylene glycol diacrylate has greatly reduced the viscosity of the solution without sacrificing feature resolution. Etch process development has shown that a CF 4 /O 2 feed rich in CF 4 provides sufficient etch selectivity to etch the residual etch barrier layer, while O 2 rich feed provides sufficient selectivity for the transfer layer etch. With this recent work we have demonstrated polymer-on-Si semi-dense lines smaller than 50 nm made with the SFIL process. Studies of defectivity have not revealed significant defect generation, and in fact have revealed no substantial defect propagation. Oxygen diffusion into the polymerizing imprint material inhibits the free radical curing reaction to such an extent around the imprint perimeter so as to create a
Modelling and optimisation study on the fabrication of nano-structures using imprint forming process
Engineering Computations, 2011
Purpose -Nano-imprint forming (NIF) is a manufacturing technology capable of achieving high resolution, low-cost and high-throughput fabrication of fine nano-scale structures and patterns. The purpose of this paper is to use modelling technologies to simulate key process steps associated with the formation of patterns with sub-micrometer dimensions and use the results to define design rules for optimal imprint forming process. Design/methodology/approach -The effect of a number of process and pattern-related parameters on the quality of the fabricated nano-structures is studied using non-linear finite element analysis. The deformation process of the formable material during the mould pressing step is modelled using contact analysis with large deformations and temperature dependent hyperelastic material behaviour. Finite element analysis with contact interfaces between the mould and the formable material is utilised to study the formation of mechanical, thermal and friction stresses in the pattern. Findings -The imprint pressure, temperature and the aspect ratio of grooves which define the pattern have significant effect on the quality of the formed structures. The optimal imprint pressure for the studied PMMA is identified. It is found that the degree of the mould pattern fulfilment as function of the imprint pressure is non-linear. Critical values for thermal mismatch difference in the CTE between the mould and the substrate causing thermally induced stresses during cooling stage are evaluated. Regions of high stresses in the pattern are also identified. Originality/value -Design rules for minimising the risk of defects such as cracks and shape imperfections commonly observed in NIF-fabricated nano-structures are presented. The modelling approach can be used to provide insights into the optimal imprint process control. This can help to establish further the technology as a viable route for fabrication of nano-scale structures and patterns.