Nanoimprint lithography (NIL) is more than a planar high-end technology for the patterning of waf... more Nanoimprint lithography (NIL) is more than a planar high-end technology for the patterning of wafer-like substrates. It is essentially a 3D process, because it replicates various stamp topographies by 3D displacement of material and takes advantage of the bending of stamps while the mold cavities are filled. But at the same time, it keeps all assets of a 2D technique being able to pattern thin masking layers like in photon-and electron-based traditional lithography. This review reports about 20 years of development of replication techniques at Paul Scherrer Institut, with a focus on 3D aspects of molding, which enable NIL to stay 2D, but at the same time enable 3D applications which are ''more than Moore.'' As an example, the manufacturing of a demonstrator for backlighting applications based on thermally activated selective topography equilibration will be presented. This technique allows generating almost arbitrary sloped, convex and concave profiles in the same polymer film with dimensions in micro-and nanometer scale.
Microelectronic Structures and MEMS for Optical Processing III, 1997
ABSTRACT We report on the fabrication of lens components, based on diffractive optical elements, ... more ABSTRACT We report on the fabrication of lens components, based on diffractive optical elements, for the purpose of imaging laser-diode emission onto fibers or photodetectors, or for collimation applications. The miniature optical elements are arranged in arrays with 250 micrometer pitch which make them well suited for applications with fiber ribbons. Test optical plates were made of polycarbonate using hot stamper replication technology. The imaging properties of these optical plates from single-mode fibers onto single-mode fibers or from lasers onto single-mode fibers are discussed. The addition of 3D-marker structures to the outline borders of such plates made them suitable for use in micro-optical benches with built-in mechanical registration structures. We fabricated the optical bench inserts with built-in passive alignment elements using deep x-ray LIGA technology (LIGA is a German acronym for 'lithographie, galvanik und abformung' meaning lithography, electroforming and molding). This technology offers high mechanical precision even for the 500 micrometer thick optical bench inserts which we fabricated by injection molding out of transparent and thermally stable polycarbonate. We report on first arrangements of plastic optical bench inserts into micro-optical benches. With the aim towards a fully replicated micro-optical bench made out of plastic we also report on a mounting concept for laser-didoes with built-in alignment trenches. The fabrication process and important properties of these special lasers which we recently developed for transceiver applications are described. We use these lasers for imaging onto single-mode fibers applying the diffractive optical element plates already mentioned.
The nanoimprint lithography (NIL) process with its key elements molding and thin film pattern tra... more The nanoimprint lithography (NIL) process with its key elements molding and thin film pattern transfer refers to the established process chain of resist-based patterning of hard substrates. Typical processes for mass fabrication are either wafer-scale imprint or continuous roll-to-roll processes. In contrast to this, similar process chains were established for polymeric microelements fabricated by injection molding, particularly when surface topographies need to be integrated into monolithic polymer elements. NIL needs to be embedded into the framework of general replication technologies, with sizes ranging from nanoscopic details to macroscopic entities. This contribution presents elements of a generalized replication process chain involving NIL and demonstrates its wide application by presenting nontypical NIL products, such as an injection-molded microcantilever. Additionally, a hybrid approach combining NIL and injection molding in a single tool is presented. Its aim is to introduce a toolbox approach for nanoreplication into NIL-based processing and to facilitate the choice of suitable processes for micro-and nanodevices. By proposing a standardized process flow as described in the NaPANIL library of processes, the use of establish process sequences for new applications is facilitated.
Good old Gutenberg could not have imagined that his revolutionary printing concept which so great... more Good old Gutenberg could not have imagined that his revolutionary printing concept which so greatly contributed to dissemination of knowledge and thus today's wealth, would have been a source of inspiration five hundred years later. Now, it seems intuitive that a simple way to produce a large number of replicates is using a mold to emboss pattern you need, but at the nanoscale nothing is simple: the devil is in the detail. And this book is about the "devil". In the following 17 chapters, the authors-all of them well recognized and active actors in this emerging field-describe the state-of-theart, today's technological bottlenecks and the prospects for micro-contact printing and nanoimprint lithography. Many results of this book originate from projects funded by the European Commission through its "Nanotechnology Information Devices" (NID) initiative. NID was launched with the objective to develop nanoscale devices for the time when the red-brick scenario of the ITRS roadmap would be reached. It became soon clear however, that there was no point to investigate only alternative devices to CMOS, but what was really needed was an integrated approach that took into account more facets of this difficult undertaking. Technologically speaking, this meant to have a coherent strategy to develop novel devices, nanofabrication tools and circuit & system architectures at the same time. There is no point having an interesting device; we have to know how to produce them massively by millions and once we have achieved it we must find a way to interconnect them in a useful way. Thus, projects were therefore selected taking also into account a balance between these different technological areas. Two additional important issues had to be taken into the NID strategy. First, the NID budget was insufficient to fund all promising European research work. Second, My thanks go to Steve Beaumont and Chris Wilkinson for introducing me to nanofabrication and to Hella-Cristin Scheer for accompanying me in the first steps of our joint work on nanoimprint lithography. I have learnt much on many aspects of nanofabrication with partners of our European IST FET projects NANOTECH and later on CHANIL,
LiGA and NIL are both techniques with origination by lithography, using molding techniques for up... more LiGA and NIL are both techniques with origination by lithography, using molding techniques for upscaling or even stamp copying. The main difference is the size range for which they were seen to have most of their applications. The technology toolboxes contain similar processes and concepts, but due to historical differences, NIL and LiGA were not seen as twins, but rather children from different families. LiGA, as the more mature microtechnology, has found its application in microfluidics,-optics and-mechanics. NIL has found its place in photonics and sub-wavelength gratings, and is considered as a candidate for patterned media and next generation lithography for IC manufacturing. In this review I will discuss similarities and differences of the two technologies, tackle questions from pattern transfer, size effects including the need for hard and soft elements for molding and discuss points where LiGA and NIL might find a common basis for further cross-fertilization and joint applications.
We like to express our thanks to Prof. W. Ehrfeld and his LIGA-team at the Institute of Microtech... more We like to express our thanks to Prof. W. Ehrfeld and his LIGA-team at the Institute of Microtechnology Mainz (IMM), Germany, where much of the work has been done in the program ''Microfabrication Capability and Expertise for User Defined Purposes''. The work profited much from recent experience with injection molding of miniaturized gear boxes (see Thu¨rigen et al. (1996)).
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2008
Nanoimprint lithography ͑NIL͒ is a high throughput, high-resolution parallel patterning method in... more Nanoimprint lithography ͑NIL͒ is a high throughput, high-resolution parallel patterning method in which a surface pattern of a stamp is replicated into a material by mechanical contact and three dimensional material displacement. This can be done by shaping a liquid followed by a curing process for hardening, by variation of the thermomechanical properties of a film by heating and cooling, or by any other kind of shaping process using the difference in hardness of a mold and a moldable material. The local thickness contrast of the resulting thin molded film can be used as a means to pattern an underlying substrate on wafer level by standard pattern transfer methods, but also directly in applications where a bulk modified functional layer is needed. Therefore it is mainly aimed toward fields in which electron beam and high-end photolithography are costly and do not provide sufficient resolution at reasonable throughput. The aim of this review is to play between two poles: the need to establish standard processes and tools for research and industry, and the issues that make NIL a scientific endeavor. It is not the author's intention to duplicate the content of the reviews already published, but to look on the NIL process as a whole. The author will also address some issues, which are not covered by the other reviews, e.g., the origin of NIL and the misconceptions, which sometimes dominate the debate about problems of NIL, and guide the reader to issues, which are often forgotten or overlooked.
Nanoimprint Lithography (NIL) is considered as a low-cost fabrication process for photonic device... more Nanoimprint Lithography (NIL) is considered as a low-cost fabrication process for photonic devices. By embossing a two-dimensional periodic pattern into a thin polymer layer, a photonic bandgap (PBG) device can be generated. A waveguide can be generated by removing single rows of pillars or holes in the PGB structures. This implies that by engineering a grating structure by a lithographic means, the light propagation can be controlled and even be tuned. Because of their low propagation loss at telecommunication wavelengths, polymer waveguides with two-dimensional periodic patterns are attractive candidates for platforms implementing low loss PBG photonic crystals [1]. We present a fabrication process for producing dense two-dimensional periodic patterns in polymers, with defined fill factor (the ratio pillar diameter to gap) and aspect ratio. A stamp copying process (figure 1) was developed, which had significant advantages over a one-step stamp manufacturing process. It allows us t...
http://www.ecmjournal.org Comparing physical properties of PEKK and PEEK Prabitha Urwyler, Xue Zh... more http://www.ecmjournal.org Comparing physical properties of PEKK and PEEK Prabitha Urwyler, Xue Zhao, Alfons Pascual, Uwe Pieles, Helmut Schift, Bert Müller 1 Biomaterials Science Center, University of Basel, CH. 2 Institute of Polymer Engineering, University of Applied Sciences and Arts Northwestern Switzerland, Windisch, CH. 3 Institute for Chemistry and Bioanalytics, University of Applied Sciences and Arts Northwestern Switzerland, Muttenz, CH. 4 Laboratory for Microand Nanotechnology, Paul Scherrer Institut, Villigen, CH
Dispositif d'affichage a cristaux liquides comprenant un premier substrat avant (4) et un sec... more Dispositif d'affichage a cristaux liquides comprenant un premier substrat avant (4) et un second substrat arriere (6) separes par un espace (8) delimitant un volume pour le confinement d'une couche de molecules de cristal liquide (10), ces substrats (4, 6) comportant sur leurs faces interieures en regard un premier et un second groupe d'electrodes (12, 14) respectivement, l'application d'une tension de commande appropriee a des electrodes selectionnees permettant de modifier localement les proprietes optiques du cristal liquide, ce dispositif d'affichage (2) comprenant en outre une couche d'alignement heterogene (16) menagee sur la face interieure de l'un au moins des deux substrats (4, 6), cette couche d'alignement (16) comprenant un film (22) qui induit soit un alignement planaire, soit un alignement homeotrope des molecules de cristal liquide et sur lequel est structure un reseau periodique de motifs elementaires (20) qui induisent un alignemen...
Two-photon polymerization by direct laser writing enables to write refractive micro-optical eleme... more Two-photon polymerization by direct laser writing enables to write refractive micro-optical elements with sub-µm precision. The trajectories and layering during the direct writing process often result in roughness in the range of the writing increment, which has adverse effects for optical applications. Instead of increasing overlap between adjacent voxels, roughness in the range of 100 nm can be smoothed out by post-processing. For this a method known as TASTE was developed, which allows polishing of surfaces without changing the structural details or the overall shape. It works particularly well with thermoplastic polymers and enables sub-10 nm roughness. The optical quality was confirmed for an array with several 100 microlenses.
State-of-the-art, polymeric, refractive micro-optics simultaneously require an ultrasmooth threed... more State-of-the-art, polymeric, refractive micro-optics simultaneously require an ultrasmooth threedimensional (3-D) surface and a precise geometry for excellent optical performance with minimal stray light. In earlier work, we have established a surface finishing process for thermoplastic polymer master structures that is only effective on the surface and does not affect the designed optical geometry, thus enabling polishing without touching. Therewith, the high curvature corners of a 50-μm-tall optical diffuser device were maintained while the surface roughness was reduced to about 10-nm root mean square. For this, 3-D master structures were first fabricated by direct write laser-lithography with two-photon polymerization. The master structures were replicated into poly(methyl methacrylate) through a poly(dimethyl siloxane) intermediate replication stamp. Finally, all structures were surface-polished by selective high-energy photon exposure and thermal postprocessing. In this work, we focus on the comparison of the surface smoothening using either postprocessing or dedicated direct writing strategies. For this comparison, strategies for modifying the exposed voxel size and the writing discretization being the primary source of roughness were tested by sweeping the laser exposure dose for two different resist materials and objectives. In conclusion, the postprocessing smoothening resulted in a lower roughness compared to a direct writing strategy-even when 50-nm vertical discretization steps were usedand still enabled 10 times shorter writing times.
Nanoimprint lithography (NIL) is more than a planar high-end technology for the patterning of waf... more Nanoimprint lithography (NIL) is more than a planar high-end technology for the patterning of wafer-like substrates. It is essentially a 3D process, because it replicates various stamp topographies by 3D displacement of material and takes advantage of the bending of stamps while the mold cavities are filled. But at the same time, it keeps all assets of a 2D technique being able to pattern thin masking layers like in photon-and electron-based traditional lithography. This review reports about 20 years of development of replication techniques at Paul Scherrer Institut, with a focus on 3D aspects of molding, which enable NIL to stay 2D, but at the same time enable 3D applications which are ''more than Moore.'' As an example, the manufacturing of a demonstrator for backlighting applications based on thermally activated selective topography equilibration will be presented. This technique allows generating almost arbitrary sloped, convex and concave profiles in the same polymer film with dimensions in micro-and nanometer scale.
Microelectronic Structures and MEMS for Optical Processing III, 1997
ABSTRACT We report on the fabrication of lens components, based on diffractive optical elements, ... more ABSTRACT We report on the fabrication of lens components, based on diffractive optical elements, for the purpose of imaging laser-diode emission onto fibers or photodetectors, or for collimation applications. The miniature optical elements are arranged in arrays with 250 micrometer pitch which make them well suited for applications with fiber ribbons. Test optical plates were made of polycarbonate using hot stamper replication technology. The imaging properties of these optical plates from single-mode fibers onto single-mode fibers or from lasers onto single-mode fibers are discussed. The addition of 3D-marker structures to the outline borders of such plates made them suitable for use in micro-optical benches with built-in mechanical registration structures. We fabricated the optical bench inserts with built-in passive alignment elements using deep x-ray LIGA technology (LIGA is a German acronym for 'lithographie, galvanik und abformung' meaning lithography, electroforming and molding). This technology offers high mechanical precision even for the 500 micrometer thick optical bench inserts which we fabricated by injection molding out of transparent and thermally stable polycarbonate. We report on first arrangements of plastic optical bench inserts into micro-optical benches. With the aim towards a fully replicated micro-optical bench made out of plastic we also report on a mounting concept for laser-didoes with built-in alignment trenches. The fabrication process and important properties of these special lasers which we recently developed for transceiver applications are described. We use these lasers for imaging onto single-mode fibers applying the diffractive optical element plates already mentioned.
The nanoimprint lithography (NIL) process with its key elements molding and thin film pattern tra... more The nanoimprint lithography (NIL) process with its key elements molding and thin film pattern transfer refers to the established process chain of resist-based patterning of hard substrates. Typical processes for mass fabrication are either wafer-scale imprint or continuous roll-to-roll processes. In contrast to this, similar process chains were established for polymeric microelements fabricated by injection molding, particularly when surface topographies need to be integrated into monolithic polymer elements. NIL needs to be embedded into the framework of general replication technologies, with sizes ranging from nanoscopic details to macroscopic entities. This contribution presents elements of a generalized replication process chain involving NIL and demonstrates its wide application by presenting nontypical NIL products, such as an injection-molded microcantilever. Additionally, a hybrid approach combining NIL and injection molding in a single tool is presented. Its aim is to introduce a toolbox approach for nanoreplication into NIL-based processing and to facilitate the choice of suitable processes for micro-and nanodevices. By proposing a standardized process flow as described in the NaPANIL library of processes, the use of establish process sequences for new applications is facilitated.
Good old Gutenberg could not have imagined that his revolutionary printing concept which so great... more Good old Gutenberg could not have imagined that his revolutionary printing concept which so greatly contributed to dissemination of knowledge and thus today's wealth, would have been a source of inspiration five hundred years later. Now, it seems intuitive that a simple way to produce a large number of replicates is using a mold to emboss pattern you need, but at the nanoscale nothing is simple: the devil is in the detail. And this book is about the "devil". In the following 17 chapters, the authors-all of them well recognized and active actors in this emerging field-describe the state-of-theart, today's technological bottlenecks and the prospects for micro-contact printing and nanoimprint lithography. Many results of this book originate from projects funded by the European Commission through its "Nanotechnology Information Devices" (NID) initiative. NID was launched with the objective to develop nanoscale devices for the time when the red-brick scenario of the ITRS roadmap would be reached. It became soon clear however, that there was no point to investigate only alternative devices to CMOS, but what was really needed was an integrated approach that took into account more facets of this difficult undertaking. Technologically speaking, this meant to have a coherent strategy to develop novel devices, nanofabrication tools and circuit & system architectures at the same time. There is no point having an interesting device; we have to know how to produce them massively by millions and once we have achieved it we must find a way to interconnect them in a useful way. Thus, projects were therefore selected taking also into account a balance between these different technological areas. Two additional important issues had to be taken into the NID strategy. First, the NID budget was insufficient to fund all promising European research work. Second, My thanks go to Steve Beaumont and Chris Wilkinson for introducing me to nanofabrication and to Hella-Cristin Scheer for accompanying me in the first steps of our joint work on nanoimprint lithography. I have learnt much on many aspects of nanofabrication with partners of our European IST FET projects NANOTECH and later on CHANIL,
LiGA and NIL are both techniques with origination by lithography, using molding techniques for up... more LiGA and NIL are both techniques with origination by lithography, using molding techniques for upscaling or even stamp copying. The main difference is the size range for which they were seen to have most of their applications. The technology toolboxes contain similar processes and concepts, but due to historical differences, NIL and LiGA were not seen as twins, but rather children from different families. LiGA, as the more mature microtechnology, has found its application in microfluidics,-optics and-mechanics. NIL has found its place in photonics and sub-wavelength gratings, and is considered as a candidate for patterned media and next generation lithography for IC manufacturing. In this review I will discuss similarities and differences of the two technologies, tackle questions from pattern transfer, size effects including the need for hard and soft elements for molding and discuss points where LiGA and NIL might find a common basis for further cross-fertilization and joint applications.
We like to express our thanks to Prof. W. Ehrfeld and his LIGA-team at the Institute of Microtech... more We like to express our thanks to Prof. W. Ehrfeld and his LIGA-team at the Institute of Microtechnology Mainz (IMM), Germany, where much of the work has been done in the program ''Microfabrication Capability and Expertise for User Defined Purposes''. The work profited much from recent experience with injection molding of miniaturized gear boxes (see Thu¨rigen et al. (1996)).
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2008
Nanoimprint lithography ͑NIL͒ is a high throughput, high-resolution parallel patterning method in... more Nanoimprint lithography ͑NIL͒ is a high throughput, high-resolution parallel patterning method in which a surface pattern of a stamp is replicated into a material by mechanical contact and three dimensional material displacement. This can be done by shaping a liquid followed by a curing process for hardening, by variation of the thermomechanical properties of a film by heating and cooling, or by any other kind of shaping process using the difference in hardness of a mold and a moldable material. The local thickness contrast of the resulting thin molded film can be used as a means to pattern an underlying substrate on wafer level by standard pattern transfer methods, but also directly in applications where a bulk modified functional layer is needed. Therefore it is mainly aimed toward fields in which electron beam and high-end photolithography are costly and do not provide sufficient resolution at reasonable throughput. The aim of this review is to play between two poles: the need to establish standard processes and tools for research and industry, and the issues that make NIL a scientific endeavor. It is not the author's intention to duplicate the content of the reviews already published, but to look on the NIL process as a whole. The author will also address some issues, which are not covered by the other reviews, e.g., the origin of NIL and the misconceptions, which sometimes dominate the debate about problems of NIL, and guide the reader to issues, which are often forgotten or overlooked.
Nanoimprint Lithography (NIL) is considered as a low-cost fabrication process for photonic device... more Nanoimprint Lithography (NIL) is considered as a low-cost fabrication process for photonic devices. By embossing a two-dimensional periodic pattern into a thin polymer layer, a photonic bandgap (PBG) device can be generated. A waveguide can be generated by removing single rows of pillars or holes in the PGB structures. This implies that by engineering a grating structure by a lithographic means, the light propagation can be controlled and even be tuned. Because of their low propagation loss at telecommunication wavelengths, polymer waveguides with two-dimensional periodic patterns are attractive candidates for platforms implementing low loss PBG photonic crystals [1]. We present a fabrication process for producing dense two-dimensional periodic patterns in polymers, with defined fill factor (the ratio pillar diameter to gap) and aspect ratio. A stamp copying process (figure 1) was developed, which had significant advantages over a one-step stamp manufacturing process. It allows us t...
http://www.ecmjournal.org Comparing physical properties of PEKK and PEEK Prabitha Urwyler, Xue Zh... more http://www.ecmjournal.org Comparing physical properties of PEKK and PEEK Prabitha Urwyler, Xue Zhao, Alfons Pascual, Uwe Pieles, Helmut Schift, Bert Müller 1 Biomaterials Science Center, University of Basel, CH. 2 Institute of Polymer Engineering, University of Applied Sciences and Arts Northwestern Switzerland, Windisch, CH. 3 Institute for Chemistry and Bioanalytics, University of Applied Sciences and Arts Northwestern Switzerland, Muttenz, CH. 4 Laboratory for Microand Nanotechnology, Paul Scherrer Institut, Villigen, CH
Dispositif d'affichage a cristaux liquides comprenant un premier substrat avant (4) et un sec... more Dispositif d'affichage a cristaux liquides comprenant un premier substrat avant (4) et un second substrat arriere (6) separes par un espace (8) delimitant un volume pour le confinement d'une couche de molecules de cristal liquide (10), ces substrats (4, 6) comportant sur leurs faces interieures en regard un premier et un second groupe d'electrodes (12, 14) respectivement, l'application d'une tension de commande appropriee a des electrodes selectionnees permettant de modifier localement les proprietes optiques du cristal liquide, ce dispositif d'affichage (2) comprenant en outre une couche d'alignement heterogene (16) menagee sur la face interieure de l'un au moins des deux substrats (4, 6), cette couche d'alignement (16) comprenant un film (22) qui induit soit un alignement planaire, soit un alignement homeotrope des molecules de cristal liquide et sur lequel est structure un reseau periodique de motifs elementaires (20) qui induisent un alignemen...
Two-photon polymerization by direct laser writing enables to write refractive micro-optical eleme... more Two-photon polymerization by direct laser writing enables to write refractive micro-optical elements with sub-µm precision. The trajectories and layering during the direct writing process often result in roughness in the range of the writing increment, which has adverse effects for optical applications. Instead of increasing overlap between adjacent voxels, roughness in the range of 100 nm can be smoothed out by post-processing. For this a method known as TASTE was developed, which allows polishing of surfaces without changing the structural details or the overall shape. It works particularly well with thermoplastic polymers and enables sub-10 nm roughness. The optical quality was confirmed for an array with several 100 microlenses.
State-of-the-art, polymeric, refractive micro-optics simultaneously require an ultrasmooth threed... more State-of-the-art, polymeric, refractive micro-optics simultaneously require an ultrasmooth threedimensional (3-D) surface and a precise geometry for excellent optical performance with minimal stray light. In earlier work, we have established a surface finishing process for thermoplastic polymer master structures that is only effective on the surface and does not affect the designed optical geometry, thus enabling polishing without touching. Therewith, the high curvature corners of a 50-μm-tall optical diffuser device were maintained while the surface roughness was reduced to about 10-nm root mean square. For this, 3-D master structures were first fabricated by direct write laser-lithography with two-photon polymerization. The master structures were replicated into poly(methyl methacrylate) through a poly(dimethyl siloxane) intermediate replication stamp. Finally, all structures were surface-polished by selective high-energy photon exposure and thermal postprocessing. In this work, we focus on the comparison of the surface smoothening using either postprocessing or dedicated direct writing strategies. For this comparison, strategies for modifying the exposed voxel size and the writing discretization being the primary source of roughness were tested by sweeping the laser exposure dose for two different resist materials and objectives. In conclusion, the postprocessing smoothening resulted in a lower roughness compared to a direct writing strategy-even when 50-nm vertical discretization steps were usedand still enabled 10 times shorter writing times.
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Papers by Helmut Schift