[Show abstract][Hide abstract] ABSTRACT: An integrated position sensor for a dual-axis electromagnetic tilting mirror is presented. This tilting mirror is composed of a silicon based mirror directly assembled on a silicon membrane supported by flexible beams. The position sensors are constituted by 4 Wheatstone bridges of piezoresistors which are fabricated by doping locally the flexible beams. A permanent magnet is attached to the membrane and the scanner is mounted above planar coils deposited on a ceramic substrate to achieve electromagnetic actuation. The performances of the piezoresistive sensors are evaluated by measuring the output signal of the piezoresistors as a function of the tilt of the mirror and the temperature. White light interferometry was performed for all measurement to measure the exact tilt angle. The minimum detectable angle with such sensors was 30µrad (around 13bits) in the range of the minimum resolution of the interferometer. The tilt reproducibility was 0.0186%, obtained by measuring the tilt after repeated actuations with a coil current of 50mA during 30 min and the stability over time was 0.05% in 1h without actuation. The maximum measured tilt angle was 6° (mechanical) limited by nonlinearity of the MEMS system.
[Show abstract][Hide abstract] ABSTRACT: Nanoelectromechanical (NEM) switches have the potential to complement or replace traditional CMOS transistors in the area of ultra-low power digital electronics. This paper reports the demonstration of the first ring oscillator built using cell-level digital logic elements based on curved NEM switches. The NEM switch has a size of 5×3 μm2, an air gap of 60 nm and is coated with amorphous carbon (a-C) for reliable operation. The ring oscillator operates at a frequency of 6.7 MHz and confirms the simulated inverter propagation delay of 25 ns. The successful fabrication and measurement of this demonstrator is a key milestone on the way towards an optimized, scaled technology with sub-nanosecond switching times, lower operating voltages and VLSI implementation.
[Show abstract][Hide abstract] ABSTRACT: Digital circuits based on nanoelectromechanical (NEM) relays hold out the potential of providing an energy efficiency unachievable by conventional CMOS technology. This paper presents a detailed analysis of the operating characteristics of fabricated curved cantilever NEM relays using a comprehensive physical model. The mode of energy distribution within the electrical and mechanical operational domains of the relay is described in detail and the energy saving achievable by the technique of body-biasing is quantified. The analysis further reveals that the latency in a relay can be much larger or much smaller than the nominal mechanical delay depending on the point of actuation in the oscillation of the beam that takes place after pull-out. The methods that can utilize this phenomenon to reduce the latency of relay-based circuits are discussed, thus addressing one of the biggest challenges in NEM relay-based design.
No preview · Article · Aug 2014 · Circuits and Systems I: Regular Papers, IEEE Transactions on
[Show abstract][Hide abstract] ABSTRACT: This paper reports on wafer scale fabrication of MEMS rubidium (Rb) vapor cells used for spectroscopic measurements in miniaturized atomic clocks. The cell filling process is based on pipetting minute amounts of dissolved rubidium azide (RbN3) into cavities etched in a silicon wafer, hermetic sealing of the cavities by anodic bonding of glass caps, and in situ UV decomposition of the RbN3 into Rb and N2. All relevant elements required for operation such as resistive heaters, temperature sensors, and coils are integrated onto the vapor cell using planar technology. Experiments showed short term frequency stability below 10-10 at 1 second integration time.
[Show abstract][Hide abstract] ABSTRACT: This paper reports an amorphous carbon (a-C) contact coating for ultra-low-power curved nanoelectromechanical (NEM) switches. a-C addresses important problems in miniaturization and low-power operation of mechanical relays: i) the surface energy is lower than that of metals, ii) active formation of highly localized a-C conducting filaments offers a way to form nanoscale contacts, and iii) high reliability is achieved through the excellent wear properties of a-C, demonstrated in this paper with more than 100 million hot switching cycles. Finally, a full inverter using a-C contacts is fabricated to demonstrate the viability of the concept.
[Show abstract][Hide abstract] ABSTRACT: Heated tips offer the possibility to create arbitrary high-resolution
nanostructures by local decomposition and evaporation of resist
materials. Turnaround times of minutes are achieved with this patterning
method due to the high-speed direct-write process and an in-situ imaging
capability. Dense features with 10 nm half-pitch can be written into
thin films of organic resists such as self-amplified depolymerization
(SAD) polymers or molecular glasses. The patterning speed of tSPL has
been increased far beyond usual scanning probe lithography (SPL)
technologies and approaches the speed of Gaussian shaped electron beam
lithography (EBL) for <30 nm resolution. A single tip can write
complex patterns with a pixel rate of 500 kHz and a linear scan speed of
20 mm/s. Moreover, a novel scheme for stitching was developed to extend
the patterning area beyond the <=100 μm range of the piezo stages.
A stitching accuracy of 10 nm is obtained without the use of markers.
Furthermore, the patterning depth can be controlled independently and
accurately (~1 nm) at each position. Thereby, arbitrary 3D structures
can be written in a single step. Finally, we demonstrated an all-dry
tri-layer pattern transfer concept to create high aspect ratio
structures in silicon. Dense fins and trenches with 27 nm half-pitch and
a line edge roughness (LER) below 3nm (3σ) have been fabricated.
No preview · Article · Oct 2013 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: Thermal scanning probe lithography is used for creating lithographic patterns with 27.5 nm half-pitch line density in a 50 nm thick high carbon content organic resist on a Si substrate. The as written patterns in the poly-phthaladehyde thermal resist layer have a depth of 8 nm and they are transformed into high-aspect ratio binary patterns in the high carbon content resist using a SiO$_2$ hard-mask layer with a thickness of merely 4 nm and a sequence of selective reactive ion etching steps. Using this process, a line-edge roughness after transfer of 2.7 nm (3 $\sigma$) has been achieved. The patterns have also been transferred into 50 nm deep structures in the Si substrate with excellent conformal accuracy. The demonstrated process capabilities in terms of feature density and line-edge roughness are in accordance with today's requirements for mask-less lithography for example for the fabrication of EUV-masks.
[Show abstract][Hide abstract] ABSTRACT: A curved design for in-plane micro- and nano-electromechanical switches based on a single clamped cantilever is proposed, optimized with finite-element simulations and demonstrated experimentally. The design enables precise control of the switch motion and of the closed-state air gap, resulting in a uniform electrostatic field and increased robustness. The switch size and curvature are optimized for actuation voltage, actuation energy and the electrostatic field strength. These optimizations and the proposed fabrication process are amenable to micro- and nano-electromechanical switches. The scalability of the concept is demonstrated with simulations of nanoscale relays in terms of force and energy, showing that the concept is suitable for sub-100 aJ switching energy. Experimental results on microscale devices demonstrate the advantages of the curved MEM switches, namely a fabrication process with a single sacrificial layer for a switch with a low actuation voltage and excellent robustness. The designed as well as the experimentally observed breakdown voltage is four times higher than the contact voltage, thus enabling a large operating window for electromechanical switches.
Full-text · Article · Jan 2013 · Journal of Micromechanics and Microengineering
[Show abstract][Hide abstract] ABSTRACT: A reduced-order model for NEM relays is presented that combines electro-mechanical beam actuation and landing of beam tip on the surface electrode. This model shows a deviation of less than 2%, for the DC as well as the transient response for beam actuation in a circuit simulation, when compared to a finite-element simulation. It also shows an excellent match for the energy. The model allows accurate circuit simulation to aid in NEM-relay based logic design, and facilitates the quantification of key gate-level metrics.
[Show abstract][Hide abstract] ABSTRACT: A new type of traveling wave antenna is presented. Key features of the antenna are planar, low mass and wide bandwidth of operation. One such antenna was designed for terahertz radiation detection and realized in standard IBM CMOS-SOI process with subsequent MEMS post processing. Measurements performed at 655GHz showed very good agreement with the theoretical predictions based on full wave simulations. The present article describes the antenna physics, design, fabrication and measurement results.
[Show abstract][Hide abstract] ABSTRACT: We report on the design, fabrication and measurements of a new THz sensor concept based on an antenna-coupled MOSFET bolometer for room-temperature passive THz imaging for security and medical-diagnostic applications. The device is fabricated in a 180-nm CMOS SOI technology followed by a post-CMOS MEMS process. In this sensor, the antenna absorbing the THz electromagnetic field is directly coupled to the bolometer for maximum energy collection, whereas its design aims at minimizing its thermal mass as is necessary for fast frame rates. DC measurements before and after the MEMS process as well as thermal time constant and THz antenna measurements are presented.
[Show abstract][Hide abstract] ABSTRACT: THz-imaging enables promising applications in the medical and security domain, such as detectors for skin cancer or full-body scanners. These new possibilities arise the need for detectors in the THz frequency range. An antenna-coupled bolometer approach in a standard CMOS-SOI process, followed by a MEMS post CMOS process, is suggested to fabricate such a detector. Therefore, in this paper a cloverleaf shaped antenna design for the frequency range 0.5 THz to 1.5 THz is presented. Several design steps are shown together with measurement results regarding the influence of the MEMS process.
[Show abstract][Hide abstract] ABSTRACT: The design of a broadband on-chip antenna for passive THz imaging in the frequency range of 0.6 THz to 1.4 THz is reported. The antenna design has to fulfill the requirements of the IBM CMOS process and the MEMS post CMOS processing. The antenna is coupled directly to the sensor, a MOSFET bolometer. Because of this direct coupling and the need for real time imaging, only extremely physically small antennas are feasible. Hence, typical broadband antennas like the toothed log-periodic antenna are not useable for this application and new antenna approaches have to be examined.
[Show abstract][Hide abstract] ABSTRACT: We discuss the fundamental processes including electron conduction and adhesion of metallic contacts pertaining to the scaling of the performance metrics of nano-electro-mechanical switches. In particular, we show that under most circumstances, the switching energy is governed by the force that is needed in order to break the electrical contact when opening the switch. For an optimally designed parallel plate capacitor switch, the energy consumption does not depend on the actuation voltage. However, stray capacitances degrade the energy efficiency if a high operating voltage is chosen. The limit is of the order of 1 V for an aggressively scaled Si device, for which an overall switching energy of the order of 150 eV, a footprint area of 2500 nm2 and a switching time of 200 ps are predicted. The scaling analysis also stipulates that materials with a low free electron density and high effective mass should be used for the electrical contact, which is counter-intuitive, as such materials are known to be poor conductors on the macroscopic scale.
Preview · Article · Dec 2012 · New Journal of Physics
[Show abstract][Hide abstract] ABSTRACT: We report the design, fabrication, and characterization of cantilevers with integrated AlN actuators and conductive PtSi tips for multi-frequency atomic force microscopy. These cantilevers also possess a stepped-rectangular geometry. The excellent dynamic behavior of these cantilevers is investigated using both finite-element simulations and experimental methods. Several imaging experiments are presented to illustrate the efficacy and versatility of these cantilevers. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4755749]
No preview · Article · Sep 2012 · The Review of scientific instruments
[Show abstract][Hide abstract] ABSTRACT: Recently several multi-frequency imaging techniques have been proposed that have opened up a multitude of information channels to probe surface properties in atomic force microscopy (AFM). However, the dynamics involved are significantly more complicated than in the traditional AFM modes, and hence quantitative multi-frequency AFM (MF- AFM) remains a key challenge. In this paper, we introduce custom-made micro-cantilevers with integrated actuators and a systems-theoretic modeling framework for MF-AFM, which together provide powerful experimental and theoretical tools for quantitative measurement of tip-sample interaction forces and sample properties.
[Show abstract][Hide abstract] ABSTRACT: Structural variability and flexibility are crucial factors for biomolecular function. Here we have reduced the invasiness and enhanced the spatial resolution of atomic force microscopy (AFM) to visualize, for the first time, different structural conformations of the two polynucleotide strands in the DNA double helix, for single molecules under near-physiological conditions. This is achieved by identifying and tracking the anomalous resonance behavior of nanoscale AFM cantilevers in the immediate vicinity of the sample.
[Show abstract][Hide abstract] ABSTRACT: In this paper the state-of-the-art in wafer-level heterogeneous D integration technologies for micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS) is reviewed. Various examples of commercial and experimental heterogeneous D integration processes for MEMS and NEMS devices are presented and discussed.