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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.

A microelectromechanical system actuator based on thermophoretic, or Knudson, forces is proposed using analytical calculations. It can potentially execute scanning or spinning motions of a body that is not mechanically attached to the reference substrate. For a silicon device of 100-[micro]m diameter, it is calculated that it can be levitated at a distance of about 0.5 [micro]m from a substrate and that it can execute scanning motion and use quasi-springs by laterally acting thermal forces. In this way, an engine with spinning motion of a floating body having a diameter of 200/[micro]m with up to 5 kHz can be achieved. [2008-0013] Index Terms--Microactuators, microelectromechanical devices, micromotors, thermophoresis.

We have developed a generic cost-efficient CMOS-compatible heterogeneous device integration method at wafer-scale level. This method enables the distribution of devices from one to numerous wafers using selective transfer technology. We have applied this method for the distribution of atomic force microscopy (AFM) cantilevers and successfully demonstrated the population of multiple wafers from one source wafer. The distribution function has been designed such as to populate 42 wafers with only one source wafer. This CMOS back-end-of-the-line compatible method is particularly suitable for microelectromechanical systems and integrated circuits. Electrical interconnects are compatible with this technology. We present the concept, the selective transfer method, including a laser ablation technique used for the transfer, as well as the process and results of the application for AFM cantilever distribution. [2007-0135] Index Terms--Atomic force microscopy (AFM), heterogeneous device integration, systems-on-chip, wafer-scale 3-D integration.

We describe a planar microelectromechanical systems (MEMS)-based x/y nanopositioner designed for parallel-probe storage applications. The nanopositioner is actuated electromagnetically and has x/y motion capabilities of [+ or -] 60 [micro]m. The mechanical components are fabricated from a single-crystal silicon wafer using a deep-trench-etching process. To render the system robust against vibration, we utilize a mass-balancing concept that makes the system stiff against linear shock, but still compliant for actuation, and therefore results in low power consumption. We present details of the finite-element model used to design the device as well as experimental results for the frequency response, actuation, and vibration-rejection properties of the nanopositioner. Index Terms--Actuators, atomic force microscopy, microelectromechanical devices, motion control, motors.

We have developed a robust, CMOS back end of the line (BEOL) compatible, wafer-scale device transfer, and interconnect method for batch fabricating systems on chip that are especially suitable for MEMS or VLSI-MEMS applications. We have applied this method to transfer arrays of 4096 free-standing cantilevers with good cantilever flatness control and high-density vertical electrical interconnects to the receiver wafer (typically CMOS). Such an array is used in a highly parallel, scanning-probe-based data-storage system, which we internally call 'millipede.' A very high-integration density has been achieved, even for wafer-scale transfer, thanks to the interlocking nature of the interconnect structure, which provides easy alignment with an accuracy of 2 [micro]m. The typical integration density is 100 cantilevers/[mm.sup.2] and 300 electrical interconnects/[mm.sup.2]. Note that only the cantilevers, not a chip with cantilevers, are transferred and, unlike flip-chip technology, our method preserves the device orientation, which is crucial for MEMS applications, where often the MEMS device should have access to its environment (in our case, the cantilever tips are in contact with the storage medium). After device transfer, the system is mechanically and electrically stable up to at least 500 [degrees]C, allowing post-transfer wafer processing. Index Terms--Heterogeneous device integration, probe-based storage device, system on chip (SOC), vertical high-density interconnect, wafer-scale 3-D integration.

In thermomechanical data writing, a resistively-heated atomic force microscope (AFM) cantilever tip forms indentations in a thin polymer film. The same cantilever operates as a thermal proximity sensor to detect the presence of previously written data bits. This paper uses recent progress in thermal analysis of the writing and reading modes to develop new cantilever designs for increased speed, sensitivity, and reduced power consumption in both writing and reading operation. Measurements of cantilever electrical resistance during heating reveals physical limits of cantilever writing and reading, and verifies a finite-difference thermal and electrical simulation of cantilever operation. This work proposes two new cantilever designs that correspond to fabrication technology benchmarks. Simulations predict that the proposed cantilevers have a higher data rate and are more sensitive than the present cantilever. The various cantilever designs offer single-bit writing times of 0.2 [micro]s-25 [micro]s for driving voltages of 2-25 V. The thermal reading [DELTA]R/R sensitivity is as high as 4 x [10.sup.-4] per vertical nm in near steady-state operation. Analysis of the adaptable operation of a single cantilever bounds the operation of a cantilever array. The present cantilever operates with an array data rate as high as 35 Mbit [sec.sup.-1] at a power of 330 mW and can operate at less than 100 mW. Proposed cantilevers offer a factor of 10 improvements in both data rate and power consumption. By considering their thermal, mechanical and electrical design, and by optimizing cantilevers for both writing and reading, this work aims to guide the future development of AFM cantilevers for thermomechanical data storage systems. [774] Index Terms--Atomic force microscope (AFM), data storage, microscale heat transfer, thermal engineering.

Optical frequency combs have become a very powerful tool in metrology and beyond, thanks to their ability to link radio frequencies with optical frequencies via a process known as self-referencing. Typical self-referencing is accomplished in two steps: the generation of an octave-spanning supercontinuum spectrum and the frequency-doubling of one part of that spectrum. Traditionally, these two steps have been performed by two separate optical components. With the advent of photonic integrated circuits, the combination of these two steps has become possible in a single small and monolithic chip. One photonic integrated circuit platform very well suited for on-chip self-referencing is lithium niobate on insulator—a platform characterized by high second and third order nonlinearities. Here, we show that combining a lithium niobate on insulator waveguide with a silicon photodiode results in a very compact and direct low-noise path toward self-referencing of mode-locked lasers. Using digital servo electronics, the resulting frequency comb is fully stabilized. Its high degree of stability is verified with an independent out-of-loop measurement and is quantified to be 6.8 mHz. Furthermore, we show that the spectrum generated inside the lithium niobate waveguide remains stable over many hours. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We report on wafer-level transfer technologies to integrate PZT-based radio frequency (RF) microelectromechanical-systems switches on CMOS. Such heterogeneous integration can overcome the incompatibility of PZT material with backend- of-the-line (BEOL) CMOS technology. The PZT stack and the transfer process have been optimized to avoid degradation of the PZT actuators during the transfer. In particular, we have optimized the seed layer for the growth of highly oriented PZT on a patterned TiO2-Pt layer, optimized the electrodes structure, and developed an Al2O3 capping layer to prevent degradation of PZT during the transfer process. A full wafer-level transfer process and a selective transfer technology allowing the distribution of RF switches from one source wafer to many receiving wafers has been demonstrated. The latest transfer process demonstrated exhibits great potential for cost optimization of wafer-level transfer of microdevices. In a separate experiment, we have demonstrated the BEOL CMOS compatibility of our integration technique. Switch characterization showed insertion loss of less than 0.5 dB and an isolation better than 30 dB for the 0.4- to 6-GHz frequency range with 15-V actuation voltage. [ABSTRACT FROM AUTHOR]

Understanding friction and wear at the nanoscale is important for many applications that involve nanoscale components sliding on a surface, such as nanolithography, nanometrology and nanomanufacturing. Defects, cracks and other phenomena that influence material strength and wear at macroscopic scales are less important at the nanoscale, which is why nanowires can, for example, show higher strengths than bulk samples. The contact area between the materials must also be described differently at the nanoscale. Diamond-like carbon is routinely used as a surface coating in applications that require low friction and wear because it is resistant to wear at the macroscale, but there has been considerable debate about the wear mechanisms of diamond-like carbon at the nanoscale because it is difficult to fabricate diamond-like carbon structures with nanoscale fidelity. Here, we demonstrate the batch fabrication of ultrasharp diamond-like carbon tips that contain significant amounts of silicon on silicon microcantilevers for use in atomic force microscopy. This material is known to possess low friction in humid conditions, and we find that, at the nanoscale, it is three orders of magnitude more wear-resistant than silicon under ambient conditions. A wear rate of one atom per micrometre of sliding on SiO2 is demonstrated. We find that the classical wear law of Archard does not hold at the nanoscale; instead, atom-by-atom attrition dominates the wear mechanisms at these length scales. We estimate that the effective energy barrier for the removal of a single atom is ∼1 eV, with an effective activation volume of ∼1 × 10−28 m. [ABSTRACT FROM AUTHOR]

Encapsulated conducting probes that can sustain high currents are used to study the nanoscale properties of thin-film stacks comprising of a phase-change chalcogenide, Ge2Sb2Te5. Scaling studies on this promising candidate for random-access memory devices had thus far required extensive lithography and nanoscale growth. This seriously hampers rapid materials characterization. This article describes the use of two key techniques, an encapsulated conductive probe and its use in retraction mode, whereby the attractive force between tip and sample is used to maintain electrical contact. The effective transformation of nanoscale dots of amorphous Ge2Sb2Te5 into the crystalline state is achieved and the electrical conductivity of the transformed structures is probed. The use of retraction force microscopy in a robust manner is demonstrated by reading the conductivity of the crystalline dots. Both these techniques could enable rapid electrical characterization of nanoscale materials, without extensive nanopatterning, thus reducing material development cycles. [ABSTRACT FROM AUTHOR]

We have designed and fabricated a cryogenic variable-temperature current-in-plane tunneling apparatus to measure the magnetoresistive properties of unpatterned magnetic tunnel junction wafers as a function of temperature. The wafer is mounted on the cold finger of a liquid helium continuous flow cryostat. The temperature can be continuously varied between 7 and 330 K. We describe the design and fabrication of the micromachined silicon probe head that comprises a comb of 20 measuring and 4 leveling probes. The measuring probes are typically 0.7 μm wide and 1.2 μm thick, with lengths of 10, 7, and 4 μm, and a pitch that varies from 1.5 to 30 μm. The leveling probes are used in conjunction with a tilt stage to adjust the parallelism between the comb and the sample wafer during the approach of the probe head. The probe head is mounted on a nonmagnetic x-y stage, which can access a 22×22 mm2 area with a repeatability of ∼1 μm. The first measurements taken at room and cryogenic temperatures are shown. [ABSTRACT FROM AUTHOR]

We report on a new atomic force microscope (AFM)-based data storage concept called the "Millipede" that has a potentially ultrahigh density, terabit capacity, small form factor, and high data rate. Its potential for ultrahigh storage density has been demonstrated by a new thermomechanical local-probe technique to store and read back data in very thin polymer films. With this new technique, 30-40-nm-sized bit indentations of similar pitch size have been made by a single cantilever/tip in a thin (50-nm) polymethylmethacrylate (PMMA) layer, resulting in a data storage density of 400-500 Gb/in.[sup 2] High data rates are achieved by parallel operation of large two-dimensional (2D) AFM arrays that have been batch-fabricated by silicon surface-micromachining techniques. The very large scale integration (VLSI) of micro/nanomechanical devices (cantilevers/tips) on a single chip leads to the largest and densest 2D array of 32 x 32 (1024) AFM cantilevers with integrated write/read storage functionality ever built. Time-multiplexed electronics control the write/read storage cycles for parallel operation of the Millipede array chip. Initial areal densities of 100-200 Gb/in.[sup 2] have been achieved with the 32 x 32 array chip, which has potential for further improvements. In addition to data storage in polymers or other media, and not excluding magnetics, we envision areas in nanoscale science and technology such as lithography, high-speed/large-scale imaging, molecular and atomic manipulation, and many others in which Millipede may open up new perspectives and opportunities. [ABSTRACT FROM AUTHOR]

A new microcantilever array design is investigated comprising eight flexible microcantilevers introducing two solid bars, enabling to subtract contributions from differences in refractive index in an optical laser read out system. Changes in the refractive index do not contribute undesirably to bending signals at picomolar to micromolar DNA or protein concentrations. However, measurements of samples with high salt concentrations or serum are affected, requiring corrections for refractive index artifacts. Moreover, to obtain a deeper understanding of molecular stress formation, the differential curvature of cantilevers is analyzed by positioning the laser spots along the surface of the levers during pH experiments. [ABSTRACT FROM AUTHOR]

We have developed a cantilever device for applying a time-of-flight scanning force microscope (TOF–SFM) system. The cantilever device consists of a switchable cantilever with an integrated bimorph actuator, an integrated extraction electrode to minimize the ion extraction voltage, and an interlocking structure for precise tip–EE alignment. The TOF–SFM with the cantilever device allows quasisimultaneous topographical and chemical analyses of solid surfaces to be performed in the same way as with the conventional scanning probe technique. The switching properties of the bimorph actuator are demonstrated for use in two operating systems. Field emission measurements and a TOF analysis of a Pt-coated tip are conducted with the TOF–SFM. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Heat conduction governs the ultimate writing and reading capabilities of a thermomechanical data storage device. This work investigates transient heat conduction in a resistively heated atomic force microscope cantilever through measurement and simulation of cantilever thermal and electrical behavior. The time required to heat a single cantilever to bit-writing temperature is near 1 μs and the thermal data reading sensitivity ΔR/R is near 1x10[sup -4] per vertical nm. Finite-difference thermal and electrical simulation results compare well with electrical measurements during writing and reading, indicating design tradeoffs in power requirements, data writing speed, and data reading sensitivity. We present a design for a proposed cantilever that is predicted to be faster and more sensitive than the present cantilever. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article discusses the parallel arrangement of cantilever arrays to achieve the speed needed for data storage applications in atomic force microscopy, the most widely used scanning probe technique by the IBM Zurich Research Lab team. It drags a tiny cantilever on a surface processed by a computer into a graphical image. The probe storage technology which leverages silicon-on-insulator is optimized for minimal power consumption to be suited for digital cameras and cellular telephones.