MEMS / NEMS

Micro/nano-technologies enable the fabrication of complex and miniaturized functional systems, called MEMS and NEMS (i.e., micro/nano electro-mechanical systems). MEMS/NEMS provide interface functions (sensors and actuators) between micro- or nanoelectronics and the environment and human beings. Thus, there is a strong relation between sensors and MEMS/NEMS. Prominent microsystem examples from the past are automotive safety sensors (crash sensing, driver assistance) and projection systems (DMDTM ). In MEMS/NEMS we will continue substituting functional micro-scaled structures (e.g. silicon based surface micro-machined capacitive transducers) by new functional materials and nano scaled elements for better performance. Todays prominent examples are macro molecular carbon nanotubes, which have already been explored in MEMS/NEMS for displacement, force, pressure and gas sensing. New functional materials based on graphene layers, or molecular layers and structures applied for functionalization of surfaces and transducers are envisioned. MEMS/NEMS in general are considered enabling devices for all kind of tera-scale systems, which are proposed to interfaces the environment and the ambient of human beings with autonomous, widely distributed and interacting systems. MEMS/NEMS will also become parts of micro- and nano-electronic systems (systems-in-package) providing functions like resonators, filters, switches and RF MEMS/NEMS in general.

Focusing on the programs application areas, we propose to tackle specific challenges in technologies, devices and system integration aspects for MEMS/NEMS to fulfill the specific needs of tera-scale systems, with particular attention to highest functional integration, ultra-low power consumption and energy harvesting and the use of process technologies that can be scaled to industrial production.

Technology

Novel Functional Materials: We propose to evaluate, pattern and integrate new functional materials, which must be compatible, stable, reliable, cost-efficient and suitable for MEMS/NEMS with exceptional properties to support device operation on the micro and nano scale and to provide new functional properties for sensors, actuators and interfaces (i.e. ability to transfer signal information from the physical and/or chemical domain to the electrical domain and vice versa).  This includes materials for nanowires, carbon nanotubes (CNTs), graphene, and materials to achieve components and MEMS/NEMS that integrate micro/nano mechanical, thermal, fluidics and optical structures and structures for chemical and bio-chemical sensing into silicon-based semiconductor processes and alternative material groups (e.g. polymers). A special focus will be doping effects in current nano-materials (e.g. Single-Walled Nanotubes - SWNTs) and the evaluation of their potential usage as new functional materials to be used in MEMS/NEMS.  Examples for first step activities are carbon nanotubes and nanowires for 1D charge state materials and for the utilization of their excellent properties in sensing mechanical, optical and (bio) chemical quantities. This activity leverages research in material sciences, and complements it by developing the fabrication technologies to use novel materials in MEMS/NEMS.

Novel Fabrication and Process Integration Technologies: The challenge for the integration and fabrication of nano sized structures as functional elements in MEMS/NEMS is the synthesis of these structures with predictable and controllable characteristics and the right placement and contacting with nanometer resolution and controlled doping. A new generation of nano sized devices will most probably depend on non-photolithographic placement or structuring techniques like self-assembled growth or assembly of pre-fabricated structures on wafer level. The formation of low resistance contacts for CNTs and nanowires is a big challenge. Metal contacts for nano structures and the respective process flow strongly influence contact resistance and thus device properties. Metrology is needed to efficiently and accurately measure process results, e.g. radius (bandgap) distributions of batch fabricated CNTs.

Therefore examples for the first step activities are research on location and size control of catalyst dots for CNT and nanowire synthesis, concepts to predefine CNT and nanowire radius or size in a narrow distribution, metallicity and band gap, defects and - even more challenging CNT chirality. Furthermore research is needed to understand and control the contact resistance between the CNT and the first level metallization, including the influence of the respective process flow. Device passivation and zero-level packaging must be developed to maintain reliable and stable device operation. Additional, batch fabrication of inter-layer motion based Multi-Walled Nanotube (MWNT) for electromechanical logic, memories, switches and actuators and assembly technologies, i.e. self-assembly, robotic assembly, and hybrid assembly are in the scope of the program. Concepts and methods for efficient and accurate CNT characterization (Raman spectroscopy, Rayleigh scattering, electrical methods) and fast process control must be developed. These first step activities are non-exclusive examples for approaches towards upcoming challenges for the integration of CNTs and nanowires in mainstream and micro- and nano-systems. Other and completely new ideas for nano sized and quantum based structures will come up, providing a complete new set of challenges, which must be solved by focused and inter-disciplinary research.

Devices

Nano Scale Devices: New device concepts and operation models will be the key in the ultimate down scaling. Quantum-size effects, not present in todays optical and mechanical devices offer a tremendous potential for innovative new functions. New approaches towards e.g. quantum computing, nano photonics, nano mechanics and sensors are emerging from research and pushing the limits. 1D structures e.g. CNT and nanowires have been assessed to have greater impact on scaled nanoelectronics than the other concepts on the horizon (e.g. resonant tunneling devices, molecular electronic devices, ferromagnetic logic devices and spin transistors).

The areas of interest include nano-scaled MEMS/NEMS based on carbon nanotubes and nanowires: sensors (e.g. micro or nano cantilevers and resonators, CNT / nanowire sensors), micro and nano-fluidic devices and systems, small-scale energy harvesters for autonomous systems.

Examples for the first step activities are research towards understanding the basic physical mechanisms at work in quantum-confined transport at realistic temperatures and towards the characterization of the devices such as transport efficiency, ambipolar conduction, RF response, and - of particular importance in MEMS/NEMS - sensitivity, selectivity, drift, and noise. Deliverables are demonstrators for device function and evaluation of properties.

Quantum Coherent Devices: As device miniaturization proceeds quantum effects will become relevant for future devices. Single-electron effects can for example be exploited for storage concept. More important is, however, the possibility to prepare quantum systems, couple them in a controlled way, tune their coherent evolution with time and read out the result. This requires quantum devices that operate in a coherent way. Such systems have been created in a solid-state environment and the most promising candidates rely on the spin of a single confined electron or the use of a superconducting device as a two-level system. Such qubits offer the principle possibility for upscaling. It is not clear today how large a macroscopic quantum system can be realized (Schrdingers cat) which is still entirely governed by the laws of quantum mechanics. The realization of quantum hardware is a precondition for the perspectives of a future quantum information processor.

One of the most promising approaches relies on a semiconductor environment where the scaling-up process has been powerfully demonstrated for conventional classical transistors. Here we focus on quantum dots, or single-electron transistors, or spin and charge qubits. Another avenue will be to analyze, develop and fabricate such quantum electronic circuits based on superconducting components. This approach follows two main routes. Along the first route the quantum circuit is designed to provide the best possible coherence properties in the presence of realistic sources of noise and allow for the fastest possible manipulations of its quantum state. The second route follows an effort to research and possibly eliminate materials properties that are sources of decoherence. A medium term goal is to demonstrate the realization of a quantum algorithm in superconducting quantum electronic circuits. Other quantum technologies such as single photon generation and detection, quantum limited amplification and quantum interfaces will be explored as well. Also novel quantum phases such as non-Abelian quantum states, potentially realized in certain fractional quantum Hall states, frustrated spin systems or arrays of superconducting Josephson junctions will be investigated with focus on the inherent quantum coherence, in particular applied to nanostructure devices in architectures suitable for engineering scalable quantum information processing. In future quantum information systems, cavity-QED (quantum-electrodynamics) is envisioned to provide the interface between interacting two-level systems that are used to manipulate quantum information and photons that carry it from one location to another.

Small-Scale Energy Sources: Autonomous) systems can harvest energy from the environment on the basis of different physical principles such as heat, radiation, kinetic and chemical energy if applicable. The efficiency of energy harvesters must be increased (output power per volume or weight) by research towards the development of high performance materials, devices and fabrication technologies to realize a variety of micro-power sources, storage and conversion concepts, while packaging will be addressed closely with the specific applications targeted. Examples:

• Bio-energy harvesting and power sources. The proposed activity aims at an implantable direct glucose fuel cell that is capable of delivering sufficient energy to run currently externally powered implants, and at an enzymatic glucose fuel cell for powering integrated drug delivery devices. While both fuel cell types exist as laboratory demonstrators, power density and longevity need to be improved.
• Chemical power generation. The Micro Solid Oxide Fuel Cell project focuses on the development of a miniaturized Solid Oxide Fuel Cell (micro- SOFC) hybrid power source for portable electronic equipment. Processed by microsystems technology and operating directly on liquid gas. This new type of energy device has the potential for a large increase in energy capacity compared to current Li-ion batteries.
• Mechanical energy harvesting. Recent research has demonstrated that the conversion of mechanical energy, in particular vibrational energy, can be efficiently converted into electrical energy using MEMS devices including piezoelectric layers. Encouraging energy conversion has also been demonstrated for nanowires of piezoelectric materials such as ZnO.
• Thermal energy harvesting. The performance (including costs) of thermoelectric converters is determined by a partly interfering set of parameters: thermo-power, internal electrical conductivity (should be high), internal thermal conductivity (should be low), thermal conductivity of the package (should be high ), thermal interface between the package and the hot or cold surface, and last but not least the fabrication costs and weight.
• Solar energy (e.g. photovoltaic). Even with ambient light powering of low consumption devices is possible whereas peak illumination can be employed for recharging and enhancing battery lifetime. We propose innovative miniaturized photovoltaic generators based on the use of novel materials, e.g. chalcopyrites.

Simulation and Modeling: Understanding the physical mechanisms and chemical processes, which determine device operation and material synthesis is crucial for successful device development and fabrication and for interpreting measurement results in nanotechnology. The separation between bulk and interface of a functional structure will vanish and contact properties will become important in device operation. Ab-initio simulations to calculate (e.g.) equilibrium energies, density of states and transport phenomena in nanostructures may be combined with multi-scale, multi-energy and multi-physics models to predict device operation. MDS may be combined with continuum models to evaluate the mechanisms during material synthesis and sensor operation (e.g. for nano gas sensors). On system level high integration density, nanowire interconnects, guiding of high speed data, optimum layout of semiconductor structures and development of radio frequency devices require electromagnetic based simulation, also to avoid electromagnetic compatibility (EMC) problems.

The areas of interest include simulation and modeling techniques considering fabrication processes, device functions, sensor and interface functions, quantum effects and EMC phenomena: This will include multi-scale and multi-physics simulation, ab-initio calculations and molecular dynamics simulation to account for the challenge by combining different materials on multiple scales, as well as for interfaces and sensor interaction with the environment.

System Integration

MEMS/NEMS for Personal Safety in Smart Environments: MEMS/NEMS are required to measure environmental conditions, which affect the health and security of people. Sensors including those which monitor the level of personal activity, movements, and position can provide information vital to the health and safety of elderly persons who are living alone, for example. MEMS/NEMS based monitoring of dangerous gases can be of use for persons living or working near industrial areas or congested traffic regions. It can be envisioned that sensor systems can be deployed and networked on a local platform, i.e. on a person or in a building, or on a larger scale, such as in a community or city, to monitor the environmental conditions. The networked sensors can take automated communicative/control actions if hazardous conditions arise, or if someone requires emergency assistance. If the sensor systems are on a mobile platform, such as with a person, it is especially important that they are lightweight, low power, and compact.

The areas of interest within this MEMS/NEMS section is to develop MEMS/NEMS, which provide high level of functional integration, high sensitivity, reliable operation and most important, low power operation for mobile applications. These MEMS/NEMS will be parts of System-in-Package (SIP) approaches, which may also include wireless transceivers and autonomous power supplies (e.g. energy harvesters). An example for a first step activity is the development and evaluation of a 5-degree-of freedom inertia MEMS/NEMS for context monitoring and activity control of people with need for special care.

MEMS/NEMS Integration with CMOS Electronics: Heterogeneous Systems: MEMS/NEMS systems are widely used to provide the interface between the environment and data processing systems. There are formidable challenges involved in this interface including, calibration of individual MEMS/NEMS devices, retrieval of information from sensors, signal conditioning for actuators, local signal processing, data compression and multiplexing, as well as efficient wireless communication for implantable systems. We will explore the possibilities for monolithic integration of MEMS/NEMS components together with the CMOS-based data processing blocks.

The CMOS data processing and the MEMS/NEMS parts of the system may need different substrate materials and their respective processing steps may be incompatible (or economically unfeasible) with each other. Additionally, the intended environmental operating conditions of such MEMS/NEMS systems may impose strict constraints on the electronic components. In order to address these issues we will develop heterogeneous system integration techniques.

MEMS/NEMS for Harsh Environments, Packaging and Reliability: More and more applications are demanding MEMS/NEMS (both sensing and actuation), which can reliably operate in harsh environments such as off-shore (oil and gas exploration) and high temperature environments (over 500C), automotive, aerospace, space and even in medical applications if implantation is proposed.

New materials and new processes will be required to satisfy such challenging conditions. We plan to pursue projects, which will address research on MEMS/NEMS for harsh environments, including micromachining process development (in particular Deep Reactive Ion Etching) of wide band gap semiconductors such as SiC and the related metallization processes for the application at high temperature. A strong demand exists already for pressure and vibration monitoring at temperature range from 500C until 1000C.

Packaging of such MEMS/NEMS devices for reliable operation is a major challenge. Reliability and durability of micro- and nano-structured devices is strongly influenced by several levels of packaging protecting functional elements and interconnects from environmental influence. Of particular importance are zero level coatings for passivation and protection against contamination and corrosion. For MEMS/NEMS in harsh environments research on the application of ceramic materials such as Low Temperature Co-fired Ceramics (LTCC) or ALD insulators (e.g. alumina) could meet the reliability requirements for operating the MEMS/NEMS devices in extreme conditions.

For MEMS/NEMS interconnects and protection of alternative (to silicon) nano-devices like single and multi-wall CNTs, nanowires, quantum dots and wires, and molecular electronics are unsolved or have even not been addressed yet.  New materials and procedures for zero level packaging without altering basic characteristics of nano- and quantum devices, like electronic band structure, thermo-mechanical and fatigue behavior, to avoid defect generation in and dissipation of functional structures, and to protect them from adjacent components and the environment have to be developed and implemented.

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