High‐Speed Roll‐to‐Roll Nanoimprint Lithography on Flexible Plastic Substrates (original) (raw)
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International Journal of Nanotechnology, 2014
Recent developments in flexible electronics, solar cells, displays, bio-chips and wearable technology have featured various micro/nanostructures in system designs. However, fabricating these micro/nanostructures on flexible substrates using existing technology such as photolithography, electron beam lithography (EBL) and other lithography techniques is troublesome, time consuming and costly. An in-house roll-to-roll ultraviolet nanoimprint lithography (R2R-UVNIL) system was designed and fabricated as an alternative low cost and large area patterning tool. It consists of a coating unit, soft-bake unit and imprinting unit which are connected together using a series of rollers. The aim of the integrated soft-bake stage was to minimise the mould sticking issues during the continuous R2R imprinting using solvent-based resist. The assembled R2R-UVNIL system was tested with imprinting process on an untreated commercial polyethylene terephthalate (PET) film as the flexible substrate, solvent-based SU8-2002 photopolymer as the resist and PDMS soft mould as the imprinting mould. The PDMS soft mould was replicated from an EBL patterned silicon master mould. Imprinting speeds of 50 to 150 mm/min have been achieved in this work, with relatively sound replication quality and formability for patterning sub-2 µm microstructures.
A review of roll-to-roll nanoimprint lithography
Since its introduction in 1995, nanoimprint lithography has been demonstrated in many researches as a simple, low-cost, and high-throughput process for replicating micro-and nanoscale patterns. Due to its advantages, the nanoimprint lithography method has been rapidly developed over the years as a promising alternative to conventional nanolithography processes to fulfill the demands generated from the recent developments in the semiconductor and flexible electronics industries, which results in variations of the process. Roll-to-roll (R2R) nanoimprint lithography (NIL) is the most demanded technique due to its high-throughput fulfilling industrial-scale application. In the present work, a general literature review on the various types of nanoimprint lithography processes especially R2R NIL and the methods commonly adapted to fabricate imprint molds are presented to provide a clear view and understanding on the nanoimprint lithography technique as well as its recent developments.
Bilayer, nanoimprint lithography
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2000
Nanoimprint lithography has been shown to be a viable means of patterning polymer films in the sub-100 nm range. In this work, we demonstrate the use of a bilayer resist to facilitate the metal liftoff step in imprinter fabrication. The bilayer resist technology exhibits more uniform patterns and fewer missing features than similar metal nanoparticle arrays fabricated with single layer resist. The bilayer resist relies upon the differential solubility between poly͑methyl methacrylate͒ and poly͑methyl methacrylate methacrylic acid copolymer͒. Evidence is presented that shows the technique has a resolution of better than 10 nm.
Pattern Generation by Using Multistep Room-Temperature Nanoimprint Lithography
IEEE Transactions on Nanotechnology, 2007
We have demonstrated multi-step room-temperature nanoimprint lithography (RTNIL) using polystyrene (PS, average molecular weight 97 kg/mol) as the imprint polymer layer on a silicon substrate for imprinting complex patterns. Single, double, and multiple (up to 10) sequential imprint steps were performed at imprint pressures between 1 to 30 MPa in separate experiments. We also transferred the imprinted patterns from the PS layer into the silicon substrate by means of an reactive-ion etching (RIE) process. To accomplish this demonstration, we designed and built a tool that controllably and repeatedly translated and pressed a sample into a stationary mold. The demonstrated inter-step alignment accuracy of this tool ranged between 80 nm and 380 nm. These experiments revealed that polymer deformation results when nanoimprint is used to further deform a previously structured surface. The molds used in these experiments consisted of 400-nm-period diffraction gratings, as well as of rectangular structures of varying aspect ratios, ranging from 150 to 300 nm wide.
Room-temperature and low-pressure nanoimprint lithography
Microelectronic Engineering, 2002
We demonstrate that room-temperature and low-pressure nanoimprint lithography techniques can be achieved by using Hybrane HS2550, a semi-crystalline hyperbranched resist polymer with a glass transition temperature below and a melting point above room temperature. Nanoimprint lithography at room temperature is possible with sub-100 nm resolution, as 75 nm line-and-spacing gratings were successfully fabricated with a tri-layer process and a metal lift-off. The melt viscosity of Hybrane HS2550 decreases drastically with temperature allowing nanoimprint experiments at low pressures, while maintaining imprint temperatures that are much lower than commonly required in nanoimprint technology.
Large area nanoimprint by substrate conformal imprint lithography (SCIL)
Advanced Optical Technologies, 2017
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 nanopatterns on large areas (from cm 2 to 200 mm up to display sizes) in a cost-effective manner. Conventional high-end optical lithography such as stepper/scanners is highly capital intensive and not flexible towards substrate types. Nanoimprint has had the potential for over 20 years to bring a cost-effective, flexible method for large area nano-patterning. Over the last 3-4 years, nanoimprint has made great progress towards volume production. The main accelerator has been the switch from rigid-to wafer-scale soft stamps and tool improvements for step and repeat patterning. In this paper, we discuss substrate conformal imprint lithography (SCIL), which combines nanometer resolution, low patterns distortion, and overlay alignment, traditionally reserved for rigid stamps, with the flexibility and robustness of soft stamps. This was made possible by a combination of a new soft stamp material, an inorganic resist, combined with an innovative imprint method. Finally, a volume production solution will be presented, which can pattern up to 60 wafers per hour.
2012 35th IEEE/CPMT International Electronics Manufacturing Technology Conference (IEMT), 2012
The recent developments of flexible electronics, biochips, optical devices and micro/nano-electromechanical-systems (MEMS/NEMS) have featured various complex three-dimensional or multileveled micro/ nano structures in its designs. However, fabricating these structures using the existing technologies such as photolithography and electron beam lithography (EBL) are time consuming and involved high process costs. Nevertheless, the production of these microstructures at high volume manufacturing scale has led to the demand for a simpler, low-coat and high-throughput technique for patterning process. In the present work, multi-level microstructures (3-levels) with minimum feature size of approximately 50 µm are continuously patterned onto flexible polymer substrate using in-house designed roll-toroll ultraviolet nanoimprint lithography (R2R-UV-NIL) system. Using a commercially available 50µm-thick polyethylene terephthalate (PET) film as the flexible substrate and SU8-2002 photopolymer as the imprint resist, continuous patterning of the multi-level structures has been demonstrated at speed of 100 mm/min using R2R-UV-NIL imprinting tool. Ten imprints were produced consecutively, where the confocal laser scanning microscopy (CLSM) measurements of the imprints demonstrated the potential of the R2R-UV-NIL technique to replicate multi-level structures, albeit the pattern waviness or plane flatness issue due to the deformation of the soft PDMS mold. With further process optimization and usage of a harder mold material, the R2R-UV-NIL is a promising technique and tool for fabricating complex 3D and multi-level microstructures on flexible substrate for future applications.
Flexible stamp for nanoimprint lithography
18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005., 2005
The design, fabrication and pedomance of a flexible silicon stamp for homogenous large area nanoimprint lithography (NIL) are presented. The flexible stamp is fabricated by bulk semiconductor micro machining of a 4-inch silicon wafer and consists of thick anchor-like imprint areas connected by membranes. The bending stiffness difference between the imprint areas and the membranes ensures that the deformation of the stamp during the imprint process mainly takes place in the membranes, leaving the imprint structures unaffected. By this design the strong demand to the parallelism between stamp and substrate in the imprint situation is decoupled from the pressing tool and the wafer quality. The stamp consist of 1562 imprint areas (1 mm x 1 mm) containing the pattems to be replicated. The imprinted patterns are characterized with respect to the imprint depth and the polymer residual layer thickness. It is found that within a 50 111111 diameter the polymer residual layer thickness is 18.8 nm with a standard deviation of 6.6 nm.
Fabrication of three-dimensional imprint lithography templates by colloidal dispersions
Journal of Materials Chemistry, 2011
Flexible displays, Self aligned imprint lithography, stamps, fluorothermoplastics, latex Self-aligned imprint lithography (SAIL) enables patterning and alignment of submicron-sized features on flexible substrates in the roll-to roll (R2R) environment. Soft molds made of elastomers have been used as stamps to pattern three-dimensional masks. Durability of these stamps is one factor that limits their efficiency in a R2R process. Fluorothermoplastics are low cost imprint stamp materials with great mechanical strength and chemical compatibility but with low gas permeability that trap air bubbles in the photopolymer during the imprint process. This paper describes the strategy for increasing gas permeability of fluorothermoplastics by introducing voids in the stamp by using aqueous colloidal dispersions of fluorothermoplastic nanoparticles. The hard fluorinated particles, whose modulus is too high to deform during drying, remain as hard spheres and lead to a porous packing when drying is complete. The selection of additives to eliminate cracks created during water evaporation is also described in this paper.