The use of imprint resists in the frame of a multi-layer systems is a viable and also very effective approach to overcome critical challenges typically associated with the patterning and fabrication of demanding nano-patterned substrates like high-aspect ratio structures often applied e.g. in optical devices. The high etch performance of the systems needed for such pattern transfers is either realized by the fabrication of in situ etch masks or by the preparation of a metal hard mask after the imprint and subsequent etch processes. While it might seem counterintuitive at first glance, to split the different features and functions of one resist into different materials and layers, the overall fabrication process however becomes more inherent robust and is moreover also easier adaptable to changes and modifications like e.g. the use of other substrate materials). Herein, we present in detail different types of multi-layer material systems that are all realized by applying candidates of the mr-NIL210 resist series.

Greyscale lithography is applied to manufacture complex 2.5D and freeform microstructures in photoresists which serve as master for the pattern transfer into materials for permanent applications, often used in micro-optics. We present the results and the challenges in reproducible generation of deep greyscale patterns in a highly sensitive greyscale positive photoresist, mr-P 22G_XP, when using photomask-based mask aligner greyscale lithography in contrast to laser direct writing on which resist development had been focused. Furthermore, we show the influence of resist aging on the resist response, and ways to correct it by process adaption, as well as we conclude requirements to greyscale photomasks suitable to make use of the full potential of the mr-P 22G_XP resist dedicated for > 100 mu m deep greyscale patterns.

Hybrid polymers are a class of materials especially suited for micro-optical applications due to their outstanding transmission and excellent stability towards temperature, chemicals and radiation. They are solvent-free viscous liquid and therefore UV-replication has become the most established process for their usage in micro-optics manufacture. However, they have also comparable processing behavior to classical photoresists and can be processed in versatile ways offering further possibilities for 2D and 3D structuring. Herein, we report on different UV-lithographical technologies to create high-aspect and high resolution pattern with hybrid polymers.

Hybrid Polymers are a material class established in the industry for manufacturing of high-performance optical components, mainly patterned by (nano)imprint processes. Recently, the application range of Hybrid Polymers has been extended into bonding and passivation. In this context, patterning by classical UV-lithography has come into focus as an alternative patterning method to (nano)imprinting. By applying a two-stage curing process with a high intensity, low dose patterning step and a high dose flood exposure after development, it is possible to realize previously unattainable resolutions limits for Hybrid Polymers of 6μm L/S and aspect ratios of more than 3.

Greyscale lithography for the manufacture of complex 2.5D and freeform microstructures in photoresists receives increasing attention from industry for the fabrication of advanced micro-optical elements. The thus obtained structures serve as master or template for different methods of pattern transfer into materials for final, permanent applications, such as refractive and diffractive lenses, blazed gratings, beam-shapers etc. However, many such applications require large structure heights beyond 100 μm which was not easily accessible until now. We present a novel photoresist, mr-P 22G_XP, enabling greyscale lithography of very deep patterns. Issues limiting the pattern depth caused by the photoresist chemistry were addressed. Greyscale pattern depths of 120 μm were possible with an easily accessible set-up with this prototype, with a well-considered choice of photoresist ingredients, and lithography process adjustments focusing on laser direct writing, with the prospect of even deeper patterns up to 140–150 μm.

The ongoing advancement of lithographic manufacturing in micro- and nanopatterning rely on the commercial availability of innovative photoresists, polymers and photopolymers as well as complementary process chemicals: This allows to enhance current micro- and nanofabrication technologies by increasing the overall pattern complexity or general process simplicity. In this contribution, we demonstrate that material innovations have a significant part in enhancing micro- and nanofabrication by outperforming generic photoresists through cross-functionality as it is increasingly required in ever growing pattern complexity (e.g. advanced mix-and-match methods) or when additional material features are set by the final application.

We propose a novel approach of combined patterning technologies to manufacture individualized micro-optical components as required for the integration of system-level optical packaging, e.g. for coupling light into on-chip level waveguides. The presented work consists of an innovative combination of inkjet printing of available optical polymers onto a prepatterned substrate and UV-replication which enables the manufacturing processes for tailor-made polymeric hybrid and biconvex micro-optical components. For this, inkjet printing of the optical polymers InkOrmo or InkEpo is used as a dispensing technique for additive manufacturing. The ink is printed into designated cavities on a patterned substrate that shows either diffractive or refractive features. After UV-induced polymerization, the cured component is separated from the soft mold substrate. This results in a combination of either a diffractive and a refractive element or two convex refractive elements in one monolithic component. The refractive part on top is self-organized by the surface energy and the shape is adjusted with the amount of dispensed ink enabling to tune the refractive power of the lens. The diffractive structure or convex shape on the opposite side of the lens is obtained by replicating the shape of the prepatterned substrate. Such advanced micro-optic components allow in principle a higher degree of system integration and thus further system miniaturization by e.g. substituting a multi lens system with a single hybrid lens. This novel manufacturing concept is composed to cost-effectively implement design requirements, making tailor-made diffractive-refractive lenses easily accessible e.g. to the MEMS/MOEMS community.

AbstractThe continuous miniaturization of components and devices along with the increasing need of sustainability in production requires materials which can fulfill the manifold requests concerning their functionality. From an industrial point of view emphasis is on cost reduction either for the materials, the processes, or for both, along with a facilitation of processing and a general reduction of resource consumption in manufacturing. Multifunctional nanoscale materials have been widely investigated due to their tunable material properties and their ability to fulfill the increasingly growing demands in miniaturization, ease of processes, low-cost manufacturing, scalability, reliability, and finally sustainability. A material class which fulfills these requirements and is suited for integrated or waferscale optics are inorganic–organic hybrid polymers such as ORMOCER®s [ORMOCER®is registered by the Fraunhofer Gesellschaft für Angewandte Forschung e.V. and commercialized by microresist technology GmbH under license since 2003]. The combination of chemically designed multifunctional low-cost materials with tunable optical properties is very attractive for (integrated) optical and waferscale applications via a variety of different nano- and microstructuring techniques to fabricate micro- and nano-optical components, typically within less than a handful of process steps. The influence of photoinitiator and cross-linking conditions onto the optical properties of an acrylate-based inorganic–organic hybrid polymer will be discussed, and its suitability for being applied in waferscale optics is demonstrated and discussed for miniaturized multi- and single channel imaging optics.

We present a versatile and scalable method for the preparation of microfluidic channels with incorporated nano patterns. Since our approach is highly industrial driven, all used methods and materials are available in common micro-fabrication environment and are available in large quantities, respectively. In comparison to other fabrication methods capable of realizing multi-level patterns, we combine nanoimprint lithography with standard photolithography, and thereby overcome the problems of limited pattern dimensions as well as fabrication time, pathing the way for a new class of microfluidic devices.

Hybrid polymers constitute a class of optical materials combining properties of inorganic glass and organic polymers. The flexible synthesis and processing allows for specific tailoring of their properties as required for the fabrication of high-performance and reliable microoptical elements. While wafer-scale fabrication of microoptics using hybrid polymers is widely used in an industrial environment, they gain ever-increasing attention in additive manufacturing and 3D printing technologies. This chapter introduces the chemical concepts behind hybrid polymers, discusses their synthesis and processing, and gives a record on their application for the fabrication of microoptical and photonic elements using established wafer-scale as well as emerging additive manufacturing processes, in particular inkjet printing and two-photon polymerization direct laser writing.

We propose novel additive manufacturing processes to cost-effectively generate prototypes and small batches of hybrid micro-optical components. We combine UV-molding with inkjet printing techniques using the polymer inks InkOrmo and InkEpo designated for permanent optical applications. This enables the integration of diffractive and refractive optical elements into one monolithic micro-component and thus the implementation of tailor-made optical designs. Finally, the proposed processes allow a high versatile fabrication making individual micro-optics easily accessible.

A novel manufacturing chain to cost-effectively generate prototypes of hybrid micro-optical components is proposed. UV-molding and inkjet printing techniques are combined with the optical polymer inks InkOrmo and InkEpo for easily implementing tailor-made optical designs.

This paper presents a novel and innovative combination of UV-replication and inkjet printing techniques with the goal to advance the manufacturing processes for individualized polymeric hybrid micro-optical components. With focus on a technology convergence, inkjet printing of the commercially available optical hybrid polymer InkOrmo is used as a dispensing technique by means of additive manufacturing. Additionally, the ink is printed on a patterned substrate and after UV-curing the lens is separated from the micro-structured substrate. This results in a combination of refractive and diffractive elements in one single component. The refractive part on top is self-organized by the surface energy and the shape is adjusted with the amount of dispensed ink enabling to tune the refractive power of the lens. The diffractive structure on the opposite side of the hybrid lens is obtained by demolding the polymer lens from the diffractive masterstructure. Due to the negative dispersion of diffractive optical elements, their combination with refractive optical elements, especially lenses, is a well-known, well-established and effective method (e.g. in CD-players) for correction of chromatic aberrations.

In microsystem technology, the lithographical processing of substrates with a topography is very top of the protecting wafer to the contact pads of the device wafer, are one example of patterning over a topography. For structuring such circuit paths, a photolithography process, and therefore a process for homogeneous photoresist coating, is required. The most flexible and advantageous way of depositing a homogeneous photoresist film over structures with high topography steps is spray-coating. As a pattern transfer process for circuit paths in cavities, the lift-off process is widely used. A negative resist, like ma-N (MRT) or AZnLOF (AZ) is favoured for lift-off processes due to the existing negative angle of the sidewalls. Only a few sprayable negative photoresists are commercially available. In this paper, the development of a novel negative resist spray-coating based on a commercially available single-layer lift-off resist for spin-coating, especially for the patterning of structures inside the cavity and on the cavity wall, is presented.A variety of parameters influences the spray-coating process, and therefore the patterning results. Besides the spray-coating tool and the parameters, the composition of the resist solution itself also influences the coating results. For homogeneous resist coverage over the topography of the substrate, different solvent combinations for diluting the resist solution, different chuck temperatures during the coating process, and also the softbake conditions, are all investigated. The solvent formulations and the process conditions are optimized with respect to the homogeneity of the resist coverage on the top edge of the cavities. Finally, the developed spray-coating process, the resist material and the process stability are demonstrated by the following applications: (i) lift-off, (ii) electroplating, (iii) the wet and (iv) the dry chemical etching of metals on substrates with topographies.

The fabrication of optical interconnects has been widely investigated for the generation of optical circuit boards. Twophoton absorption (TPA) lithography (or high-precision 3D printing) as an innovative production method for direct manufacture of individual 3D photonic structures gains more and more attention when optical polymers are employed. In this regard, we have evaluated novel ORMOCER-based hybrid polymers tailored for the manufacture of optical waveguides by means of high-precision 3D printing. In order to facilitate future industrial implementation, the processability was evaluated and the optical performance of embedded waveguides was assessed. The results illustrate that hybrid polymers are not only viable consumables for industrial manufacture of polymeric micro-optics using generic processes such as UV molding. They also are potential candidates to fabricate optical waveguide systems down to the chip level where TPA-based emerging manufacturing techniques are engaged. Hence, it is shown that hybrid polymers continue to meet the increasing expectations of dynamically growing markets of micro-optics and optical interconnects due to the flexibility of the employed polymer material concept.

We present a new epoxy-based negative-tone dry film photoresist (DFR) for fabricating multilayer microfluidic devices using a lamination process combined with a standard photolithography technology. As proof-of-concept, a complex 3D-hydrodynamic focusing device was produced via a six-layer lamination process of 33 µm-thick DFR layers. The bonding strength of the new DFR was tested on silicon, glass, and titanium substrates, respectively. A maximum bonding strength of 37 MPa was obtained for the dry film photoresist laminated on glass. No leakage was found, and burst tests proved excellent robustness and sealing reliability of the microchannels.

Herein, we present the results of a systematic material development study we carried out in order to obtain a new positive tone resist for high resolution electron-beam lithography. Several acrylic copolymer materials with different mass fractions of the comonomers, different molecular weights and similar molecular weight distributions were synthesized and – as resist solutions – evaluated in terms of electron-beam lithography performance. On the one hand, within the ranges investigated, it was shown that the lithographic sensitivity is significantly influenced by the composition rather than by the molecular weight or molecular weight distribution. On the other hand, the etch resistance of the materials remains unaffected by changes of these parameters. The resist material exhibiting the best combination of the desired properties, mr-PosEBR, is 2 times more sensitive than PMMA (495kDa) and performs comparably to the known high resolution resist ZEP520A. For example, a grating pattern with 29nm wide lines with a period of 100nm could be generated in films of mr-PosEBR with an area dose of 100μC/cm2. In terms of resolution, single lines of only 35nm width could be fabricated via metal lift-off using 100kV EBL. Furthermore, the dry etch stability of mr-PosEBR in a reactive-ion etching (RIE) process (etch gases: CF4/SF6) is similar to the one of ZEP520A (etch rates, mr-PosEBR: 190nm/min, ZEP520A: 150nm/min, silicon: 440nm/min). Moreover, high resolution nanopatterns in mr-PosEBR could be smoothly transferred into the underlying Si substrate by a RIE process.

In this contribution, we present the results of a systematic material variation for the development of a resist material for high resolution positive tone electron beam lithography (EBL). Several acrylic copolymer materials with different compositions, that is varying mass fractions of the comonomers and different molecular weights, were synthesized and as resist solutions - evaluated in terms of EBL performance at acceleration voltages of 30 kV and 100 kV. The resist material exhibiting the best combination of the desired properties, named mr-PosEBR, is two times more sensitive than PMMA 495k and performs comparably to the known high resolution resist ZEP520A at 30 kV. For example, a grating pattern with 29 nm wide lines with a period of 100 nm could be lithographically generated in films of mr-PosEBR with an area dose of 100 mu C/cm(2). In terms of resolution, single lines of only 35 nm width could be fabricated via metal liftoff. Furthermore, the dry etch stability of mr-PosEBR in a CF4/SF6 process is similar to the one of ZEP520A. Consequently, via dry etching nano patterns in mr-PosEBR could be smoothly transferred into the underlying Si substrate with high fidelity. Moreover, mr-PosEBR was evaluated as electron beam grayscale patterning and reflow resist. It was shown that the resist exhibits a good grayscale and reflow performance very similar to PMMA 120k and ZEP520A. Via these well controllable processes the generation of a wide variety of features and applications is possible.

An all-polymer photonic crystal slab sensor is presented, and shown to exhibit narrow resonant reflection with a FWHM of less than 1 nm and a sensitivity of 31 nm/RIU when sensing media with refractive indices around that of water. This results in a detection limit of 4.5 × 10(-6) RIU when measured in conjunction with a spectrometer of 12 pm/pixel resolution. The device is a two-layer structure, composed of a low refractive index polymer with a periodically modulated surface height, covered with a smooth upper-surface high refractive index inorganic-organic hybrid polymer modified with ZrO2based nanoparticles. Furthermore, it is fabricated using inexpensive vacuum-less techniques involving only UV nanoreplication and polymer spin-casting, and is thus well suited for single-use biological and refractive index sensing applications.