Hybrid polymers have been already widely applied in photonic applications to manufacture microlenses or 2D and 3D waveguides. Thus, they are promising candidates to manufacture optical systems down to the chip level. A brief review on hybrid polymers consisting of both inorganic and organic functional units and thus combine superior material properties in just one material class will be given in this report. The material properties, which can be adjusted to the application in wide ranges enable to fabricate micro-optical elements (e.g. microlenses) using replication techniques such as UV-assisted replication or nano-imprint lithography. Aside of their applicability in 2D, emphasis will be in particular on the evaluation of hybrid polymer materials for two-photon absorption lithography, which is employed to directly manufacture sophisticated 3D photonic structures impossible to be generated with conventional 2D techniques.
We report on our development strategy of photo-curable resists for nanoimprint lithography (NIL) based on modularity. Starting with a basic formulation, we address two topics: the integration of fluorinated additives and the enhancement of the dry etching stability. We prove both concepts by the introduction of two different resists derived from the same basic formulation. The viscosity of the novel resist materials was optimized for inkjet dispensing at room temperature (RT). The novel resist materials can be applied either in NIL batch processes or in high-throughput roller processes. Batch-wise imprints were performed on various substrates such as Si or plastics, demonstrating the distinctive application versatility of the novel materials. Dry etching of spin-coated thin films on Si wafers was performed, demonstrating an etch stability versus Si of 3.5:1 by using the resist formulation with improved etching stability. Roll-to-roll NIL at high throughput on large areas was performed with web speeds of up to 30 m min−1 with different stamp materials. We conclude that all resists reported herein can be deposited via inkjet dispensing at RT, are suitable for continuous high-throughput imprinting on flexible substrates, and are applicable in step-wise NIL processes with good etch resistance in dry etch processes.
Numerous studies report the importance of nanoscale metallic features to increase the sensitivity of gas sensors, biodetectors, and for the fabrication of the new-generation plasmonic devices. So far, nanoimprint lithography has not shown the capability to pattern a metallic structure that would both be sub-15 nm and sufficiently thick to ensure electrical conductance. To overcome these limitations, we report a step and repeat nanoimprint lithography (SR-NIL) on a pre-spin-coated layer stack. This work reports the fabrication of sub-15-nm lines that are 15-nm thick and have a 50-nm-half-pitch grating with 35-nm-thick metal, which represents the new state of the art for SR-NIL.
The high throughput and large area nanostructuring of flexible substrates by continuous roller processes has great potential for future custom applications like wire grid polarizers, antireflection films, or super-hydrophobic surfaces. For each application different material characteristics have to be considered, e.g. refractive index, hydrophobicity, or dry etch stability. Herein, we show experimental results of nanoimprint lithography resist developments focused on inkjetable and photo-curable resists suitable for high throughput production, especially roll-to-roll NIL. The inkjet deposition of the novel materials is demonstrated by the use of different state-of-the-art inkjet printheads at room temperature. A plate-to-plate process on silicon substrates was successfully implemented on a NPS300 nano patterning stepper with previously inkjet dispensed NIL resist. Furthermore, we demonstrate a throughput of 30 m min-1 in a roller NIL process on PET. Dry etching of unstructured thin films on Si wafers was performed, and it was demonstrated that the etch stability in Si is tunable to a value of 3.5:1 by a concise selection of the resist components. The surface roughness of the etched films was measured to be < 2 nm, after etching of around 100 nm of the resist films what is an essential factor for a low line edge roughness. All resists reported herein can be deposited via inkjet dispensing at room temperature, are suitable for continuous high throughput imprinting on flexible substrates, and are applicable in step-wise NIL processes with good etch resistance in dry etch processes.
Advanced micro- and nanofabrication processes are constantly evolving from academic R&D environment towards real
production technology. Therefore, the availability of suitable polymers for optical applications plays a crucial role to
satisfy not only application based requirements but also the compatibility to industrial production technologies. In this
context, UV-curable hybrid polymers, i.e. inorganic-organic materials obtained by sol-gel chemistry, were recently
implemented into mass production environment, e.g. for micro-lenses in mobile device applications.
In this contribution, we report on the development of innovative hybrid polymers and their tailoring towards an easy and
fast processing with reliable and reproducible performance output for industrial large-scale production. Based on a
discussion on standard process parameters with respect to optimize the material’s performance, the technical demands of
industrial manufacture to the hybrid polymers will be subsequently reviewed by giving selective examples. This will be
complemented by a brief description of current R&D activities adapting hybrid polymers to future patterning
technologies.
The motivation for the presented research was the known issue of very expansive UV transparent stamps and moulds,
which are necessary tools for UV-based patterning methods such as UV-based nanoimprint lithography, which has been
developing as an attractive alternative lithography approach in recent 10 years. Low priced polymer working stamps
could be an alternative to quartz as stamp material. UV transparent nanoimprint stamps were fabricated from sol-gel
process-derived hybrid polymer, which has the benefit of high thermal, chemical and UV radiation stability. Tailored
surface treatment and release agents were applied to ease the de-moulding process and secure the accuracy and fidelity of
the transferred patterns. To increase the life time of the hybrid polymer nanoimprint stamps some adhesives between
stamp substrate and the stamp material were used. The hybrid polymer stamps are compatible with NIL polymers and
long-term stable even at elevated temperatures of thermal imprint processes.
One of the key elements for the successful integration of nanoimprint lithography into industrial production processes is
the availability of high-performance resist materials. In this contribution we present a novel low-viscosity and fast curing
UV-NIL polymer, which is applied by spin-coating and designed for wafer-scale imprinting. Systematic investigations of
photocurable components and photoinitiators led to the formulation of the polymer system mr-UVCur06. Film
thicknesses in the range of 50 - 500 nm with excellent quality and uniformity could be obtained by spin-coating. Its
suitability for UV-NIL processes was evaluated by means of imprinting tests and plasma etching investigations. This
included investigations on imprinting with hard moulds, UV curing doses, resolution, etch rates using various plasma
gases and pattern transfer. The beneficial flow behaviour of mr-UVCur06 led to short UV-NIL cycle times. Patterns of
several orders of magnitude with feature sizes in the range of 30 nm to several tens of micrometers could be imprinted
simultaneously. An example of a pattern transfer into Si was shown, where mr-UVCur06 was used as an polymer etch
mask.
Prepolymers formed from multifunctional allyl monomers can beneficially used in nanoimprint lithography (NIL), since they cure as a consequence of heating during the imprint process. Thus they have the potential to enable NIL at comparatively low temperatures while the imprinted patterns concurrently show high thermal stability, in contrast to thermoplastic polymers, where the thermal behaviour of the imprinted patterns is closely related to the glass transition temperature (Tg) of the polymers.
The use of allyl prepolymers for NIL was previously described, but only very few experimental data are known. In recent investigations on the application of allyl prepolymers for NIL a displacement of the patterns on the wafer has been observed after cooling down the imprinted polymer in the press. This could be avoided by detaching the stamp at the imprint temperature, i.e. without cooling down the press, which requires the polymer to be crosslinked to a great extent in this stage. Since high temperatures are necessary (150 °C - 190 °C), and the imprint time is still long, allyl prepolymers to be reported here have been modified aiming at a reduction of imprint temperature and time.
The admixture of free-radical initiators increases the polymerization rate and allows the polymerization to start at lower temperatures. A reduced imprint temperature (100 °C) and shorter imprint time (10 min) are achieved. Additional polymer modification by plasticizers improves the material flow during the imprint due to a lower Tg. Recipes for polymer modifications have been found out, which result in thermally stable imprints under the specified processing conditions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.