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The recording performance of a new magnetic tape based on perpendicularly oriented barium ferrite particles was investigated using a 90-nm-wide giant-magnetoresistive reader and a prototype enhanced-field write head. A linear density of 600 kb/in with a postdetection byte-error rate $ was demonstrated based on measured recording data and a software read channel that used a noise-predictive maximum likelihood detection scheme. Using a new iterative decoding architecture, a user bit-error rate of $ can be achieved at this operating point. To facilitate aggressive scaling of the track density, we made several advances in the area of the track-following servo. First, we developed an experimental low-noise tape transport. Second, we implemented an optimized servo channel that together with an experimental timing-based servo pattern enables the generation of position estimates with nanoscale resolution at a high update rate. Third, we developed a field-programmable gate array-based prototyping platform in which we have implemented the servo channel and an $H_{\infty }$ -based track-following controller, enabling real-time closed-loop track-following experiments. Combining these technologies, we achieved a position-error signal (PES) with a standard deviation of 10.3 nm. This magnitude of PES in combination with a 90-nm-wide reader allows the writing and reading of 177-nm-wide tracks at 600 kb/in, for an equivalent areal density of 85.9 Gb/in $^{2}$ . This paper clearly demonstrates the continued scaling potential of tape technologies based on low-cost particulate media.

On the basis of a realized 12times10 Gb/s card-to-card optical link demonstrator, the capabilities of a polymer-waveguide-based board-level optical interconnect technology are presented. The conception and realization of the modular building blocks required for this board-level optical interconnect technology are described in detail. In particular, we report on the fabrication and characterization of board-integrated optical low-loss polymer waveguides that are compatible with printed circuit board (PCB) manufacturing processes. We also explain our fully passive alignment technique, superseding time-consuming active positioning of components and connectors. To realize optical transceiver modules comprising vertical cavity surface emitting laser (VCSEL) arrays with laser drivers and photodetector arrays with transimpedance amplifiers (TIAs), a mass-production concept based on wafer-level processing has been elaborated and successfully implemented.

Carbon-based electronics is a promising alternative to traditional silicon-based electronics as it could enable faster, smaller and cheaper transistors, interconnects and memory devices. However, the development of carbon-based memory devices has been hampered either by the complex fabrication methods of crystalline carbon allotropes or by poor performance. Here we present an oxygenated amorphous carbon (a-COx) produced by physical vapour deposition that has several properties in common with graphite oxide. Moreover, its simple fabrication method ensures excellent reproducibility and tuning of its properties. Memory devices based on a-COx exhibit outstanding non-volatile resistive memory performance, such as switching times on the order of 10 ns and cycling endurance in excess of 10(4) times. A detailed investigation of the pristine, SET and RESET states indicates a switching mechanism based on the electrochemical redox reaction of carbon. These results suggest that a-COx could play a key role in non-volatile memory technology and carbon-based electronics.

Nanoscale memory devices, whose resistance depends on the history of the electric signals applied, could become critical building blocks in new computing paradigms, such as brain-inspired computing and memcomputing. However, there are key challenges to overcome, such as the high programming power required, noise and resistance drift. Here, to address these, we present the concept of a projected memory device, whose distinguishing feature is that the physical mechanism of resistance storage is decoupled from the information-retrieval process. We designed and fabricated projected memory devices based on the phase-change storage mechanism and convincingly demonstrate the concept through detailed experimentation, supported by extensive modelling and finite-element simulations. The projected memory devices exhibit remarkably low drift and excellent noise performance. We also demonstrate active control and customization of the programming characteristics of the device that reliably realize a multitude of resistance states., Nanoscale resistive memory devices could become critical building blocks in emerging brain-inspired computing paradigms. Here, the authors demonstrate such a device—a projected memory cell—based on a phase-change material that decouples resistance storage from the information-retrieval process.

We report on the 3D integration and interconnect of top-emitting VCSEL and photodiode (PD) arrays on a CMOS substrate. This technology represents a radically new way to increase the I/O bandwidth of processors and enables a path beyond 10Tb/s I/Os by using a high level of integration of opto-electrical devices (OED) directly on the processor. The integration process developed includes an OED placement of better than [email protected], OED thinning down to [email protected], and an interconnect technology with copper vias into the planarization polymer. Although the process is fully compatible with the back-end-of-line of CMOS, the experiments performed were done on dummy CMOS wafers. The opto-electrical characterization performed revealed a minimal impact of the integration process on the OED performance, demonstrating the high potential of the concept.

This paper describes single and two layer processes to realize thick resist moulds (40 and 80 µm) with a good reproducibility. The patterning of a thick AZ 4562 photoresist layer is performed with standard photolithography equipment. Different problems related to thick photoresist patterning (edge bead, resist cracking, ...) are discussed and solutions are proposed. Side walls are characterized after nickel electrodeposition and mould dissolution in acetone. Results, process limitations and applications are presented.

Advanced deep reactive ion etching (ADRIE) is a new tool for the fabrication of bulk micromachined devices. Different sensors and actuators which use ADRIE alone or combined with other technologies such as surface micromachining of silicon are presented here. These examples demonstrate the potential and the design freedom of this tool, allowing a large number of different shapes to be patterned and new smart devices to be realized.

There has recently been increased interest in carbon-based resistive random-access (RRAM) memory. Carbon-based RRAM has the potential to scale to atomic dimensions, resulting in ultra-high-density and low-power memory. Here we report reversible unipolar resistance switching in hydrogenated amorphous carbon. The devices used in this study are fabricated using e-beam lithography with built-in series resistors. A thorough analysis of the electrical transport and the resistance switching mechanism is presented.

With the ongoing progress in chip scaling, the data flow to and from chip packages is increasing accordingly. The simultaneous increase of channel count and channel speed in an essentially constant form factor becomes a more and more demanding challenge. The resulting I/O-bottleneck is considered to be a major limiting factor for the overall performance of future chip packages and computing systems. Optical interconnects offer both increased channel density as well as longer link reach at high frequencies. Our current work focuses on integrating optical I/O with standard organic packages in order to maximize the aggregate data flow to and from such packages. We present a novel approach for attaching an electro-optical conversion module directly on top of the organic chip package, together with experimental results of a first prototype implementation.

We report on a card-to-card optical interconnect demonstrator with passively aligned butt-coupled optoelectronic modules onto waveguides embedded into the printed circuit board (PCB). After describing selected building blocks, we will present experimental results obtained with the demonstrator hardware consisting of a parallel 12-channel at 10 Gb/s (120 Gb/s) optical card-to-card link.

In the long-distance telecom, local-area, and rack-to-rack link classes, optical interconnects have gradually replaced electrical interconnects. We believe that this trend will be continued in the short-distance card-backplane-card datacom link class. Convincing arguments for the predicted transition from electrical to optical interconnects are bandwidth-length advantages, density benefits, crosstalk reduction, and finally cost considerations. Based on this forecast, we currently develop a board-level optical interconnect technology facing several challenges, such as I) the manufacturing of reliable polymer waveguides, II) the elaboration of simple light-coupling concepts, III) the development of high-speed electro-optical modules, and IV) the application of cost-efficient packaging approaches. The successful mastering of all these tasks is a prerequisite for convincing high-speed system designers and porting optical interconnect technology into future product development plans. In this paper, we will present different achievements of our optical interconnect technology, e.g.: - 10 Gb/s per channel over 1 m link length, - optical link propagation loss below 0.05 dB/cm at 850 nm, - linear link densities up to 16 channels/mm, - feasibility of 2D channel arrays (e.g. 4 times 12), - a fully passive, low-cost alignment concept with a position accuracy of les 5 mum, enabling coupling losses < 0.5 dB, and - electro-optical transmitter and receiver modules operating at 10 Gb/s per channel. Finally, we will report on the successful realization of a 12 times 10 Gb/s card-to-card optical link demonstrator.

Thick photoresist (about 40 m) was patterned and used as a protective layer for protruding structures (sharp, high aspect ratio atomic force microscope tips) in wet (buffered hydrofluoric acid) and dry (reactive ion etching) etching. The process and results of its use are discussed, and some applications are proposed.

Optical waveguides embedded in a printed circuit board offer a substantial increase in the achievable bandwidth density compared with todays electrical interconnects. Specific challenges and solutions to integrate optical interconnects in a printed circuit board are addressed.

A successful implementation of optics into PCBs (printed circuit boards) requires a precise passive alignment of optical elements relative to the optical waveguides in the board. We tackled this challenge with a novel concept that allows the passive alignment onto a PCB of any optical or optoelectronic building block with a precision of a few micrometers. Markers, structured into a copper layer during manufacturing, are used as a position reference for the polymer waveguide fabrication and for the formation of mechanical alignment features. To form the latter, laser drilling, a standard process for via formation in PCBs, is used. We were able to demonstrate repeated insertions of adapter elements into these alignment slots with a standard deviation of 3 /spl mu/m for in-plane displacements. Afterwards, optical modules were mounted onto the adapters, using a standard MT interface provided by the adapter. We measured a standard deviation of the order of 5 /spl mu/m for the in-plane and out-of-plane misalignments of the module with respect to the optical waveguides. The passive alignment concept demonstrated enables accurate and simple plug-in of any kind of element, in particular of optical and opto-electronic elements, into a PCB. The concept is based on established PCB manufacturing processes, which is crucial for the development towards a low-cost optical interconnect technology.

This paper presents the Butt-coupled silicon optoelectronic modules for high-speed optical interconnects. The optoelectronic (OE) modules is populated by flip-chip bonding either with VCSELs or detectors placed in direct contact with the waveguides without additional optical elements. The light is guided through the Si module by integrated waveguides based on holes etched through the silicon, which are then oxidized and filled with a polymer. This integrated OE module concept requires only one alignment step in the board and is compatible with a multi-layer waveguide approach. Data transmission of up to 5 Gbps has been demonstrated.

Polymer waveguides embedded in a printed circuit board offer a substantial increase in the achievable bandwidth density compared with today's electrical interconnects. We present our results on the polymer waveguide technology and the building blocks that perform the optoelectronic conversion. Specific challenges in integrating optics in a printed circuit board are addressed. Data transfer measurements are presented.

Building blocks and experimental results of an optical card-backplane-card link with waveguides embedded into the boards and butt-coupled optoelectronic modules are presented. Important next steps for acceptance of the technology by system developers are listed.

Copper-film ion-exchange in glass is highly promising for fabricating optical waveguides. Enhanced steepness of the refractive index profile results from applying an electric field also during cooling. Optical waveguides present losses of 0.22 dB/cm at 1300 nm.

We discuss some of the trade-offs that we are facing when choosing design parameters for future optical backplane interconnects. We present some of our current choices, along with experimental module- and system-level results.

We report on the material evaluation, design, fabrication, and characterization of low-loss multimode polymer waveguides that are compatible with standard PCB manufacturing processes for use in large-area high-density high speed optical backplane interconnects.

We identify applications for optics-enabled printed circuit boards, together with a list of requirements that have to be met for real-world products. We draw conclusions for the technology choices, and present our approaches and experiments.

The development of optical interconnects in printed circuit boards (PCBs) is driven by the increasing bandwidth requirements in servers, supercomputers and switch routers. At higher data rates, electrical connections exhibit an increase in crosstalk and attenuation; which limits channel density and leads to high power dissipation. Optical interconnects may overcome these drawbacks, although open questions still need to be resolved. We have realized multimode acrylate-polymer-based waveguides on PCBs that have propagation losses below 0.04 dB/cm at a wavelength of 850 nm and 0.12 dB/cm at 980 nm. Transmission measurements at a data rate of 12.5 Gb/s over a 1-m-long waveguide show good eye openings, independent of the incoupling conditions. In the interconnect system, the transmitter and receiver arrays are flip-chip-positioned on the top of the board with turning mirrors to redirect the light. The coupling concept is based on the collimated-beam approach with microlenses in front of the waveguides and the optoelectronic components. As we aim for large two-dimensional waveguide arrays, optical crosstalk is an important parameter to be understood. Accordingly, we have measured optical crosstalk for a linear array of 12 optical channels at a pitch of 250 um. The influence of misalignment at the transmitter and the receiver side on optical crosstalk will be presented as a function of the distance between waveguide and transmitter/receiver.

We present the development of a 4×4 matrix of optical switches based on silicon microfabricated switches and integrated waveguides. The device consists of two chips connected together by flip-chip bonding. The first chip has 16 latched silicon switches with micro-mirrors, while the second one contains the integrated waveguides and ensures the electrical connection of the 16 switches. The incorporation of integrated waveguides, patterned using a SU-8 mask and deep reactive ion etching, in our switch devices allows both the size and the packaging complexity to be reduced, and a technology for higher order matrices to be developed.

We present the design and characterization of a new 4 X 4 switch based on the previously developed 2 X 2 fiber switch. The switching principle uses plasma etched vertical mirrors that can be moved in and out of two pairs of optical fibers with the integrated electrostatic actuator. The 4 X 4 switch is built by connecting 16 individual 2 X 2 switches in a common package (100 X 50 X 35 mm). Instead of integrating the 16 switch elements on the same chip, we preferred assembling the switches by fusion splicing. The insertion loss is less than 1.8 dB for each state.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report on recent advances in micro fabrication technology using micromolding and high aspect ratio structuring of photopolymer. The direct application is the realization of components for millimeter-size, ultrasonic piezoelectric motors. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demonstrated. Photopolymer structures have also been realized and released using a positive tone resist as sacrificial layer. The main advantages over past fabrication methods are better design flexibility, simplicity of the fabrication process, the capability to combine metallic materials (Ni) with polymeric materials ( SU-8), and the use of positive tone resist as a sacrificial layer. (C) 1998 Elsevier Science S.A. All rights reserved.

We report on recent advances in micro fabrication technology using micromoulding and high-aspect ratio structuring of photopolymer. The direct application is the realization of components for millimeter-size, ultrasonic piezoelectric motors. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demonstrated. Photopolymer structures have also been realized and released using a positive tone resist as sacrificial layer. The main advantages over past fabrication methods are better design flexibility, simplicity of the fabrication process, the capability to combine metallic materials (Ni) with polymeric materials (SU-8), and the use of positive tone resist as a sacrificial layer.

Briefly reports on advances in the fabrication technology of components for millimeter size ultrasonic piezoelectric motors. A very large height to width aspect ratio with good lateral patterning resolution is required for the active component in acoustic mode conversion. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demonstrated. The main advantages over past fabrication methods are better flexibility in the design, simplicity of the fabrication process and the combination of metallic materials (Ni) with polymeric materials (SU-8). The mechanical properties of SU-8 have been measured using free cantilever beam structures.

The continuous progress in micro- and nano-system technologies has allowed the successful development of many innovative products in process control, environmental monitoring, healthcare, automotive and aerospace as well as information processing systems. In this paper on overview will be given of current progress in micro- and nanofabrication process technologies, such as deep reactive ion etching, micro-electro discharge machining, thick photoresistant processing and plating. The availibility of these micro- and nanofabrication processes will be illustrated with examples of new generations of silicon-based sensors, actuators and Microsystems with a particular emphasis on real applications of these components and systems.

This paper will focus on the fabrication and characterization of two types of piezoelectric motors based on the elastic force motor principle. The initial motivation for this work was the development of a motor for wristwatch applications, combining high torque (1 /spl mu/m) with low power consumption (10 /spl mu/W) and small dimensions. Previously reported motors were based on a hybrid assembly of a copper-beryllium rotor, obtained by laser cutting, and a stator consisting of a circular membrane, clamped along its border. The membrane was anisotropically etched in silicon and covered with either ZnO or PZT. We report on an improved and further miniaturized version with fully microfabricated rotors and a new stator design.

After microelectromechanical systems (MEMS) devices have been well established, components of higher complexity are now developed. Particularly, the combination with optical components has been very successful and have led to optical MEMS. The technology of choice for us is the silicon-on-insulator (SOI) technology, which has also been successfully used by other groups. The applications presented here give an overview over what is possible with this technology. In particular, we demonstrate four completely different devices: (a) a 2 /spl times/ 2 optical cross connector (OXC)with an insertion loss of about 0.4 dB at a switching time of 500 /spl mu/s and its extension to a 4 /spl times/ 4 OXC, (b) a variable optical attenuators (VOA), which has an attenuation range of more than 50 dB (c) a Fourier transform spectrometer (FTS) with a spectral resolution of 6 nm in the visible, and (d) an accelerometer with optical readout that achieves a linear dynamic range of 40 dB over /spl plusmn/6 g. Except for the FTS, all the applications utilized optical fibers, which are held and self-aligned within the MEMS component by U-grooves and small leaf springs. All devices show high reliability and a very low power consumption.