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The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD) of silicon nitride (SiNx), particularly for use a low k dielectric spacer. One of the key material properties needed for SiNx films is a low wet etch rate (WER) in hydrofluoric (HF) acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD) of SiNx and evaluate the film’s WER in 100:1 dilutions of HF in H2O. The remote plasma capability available in PEALD, enabled controlling the density of the SiNx film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiNx of 6.1 Å/min, which is similar to WER of SiNx from LPCVD reactions at 850 °C.

We describe the fabrication of a double-layer silicon photonic crystal using self-aligned CMOS-compatible processes and its assembly on a single mode fiber using a wafer template and epoxy bonding. The fiber sensor has sharper resonances and higher temperature sensitivity than the previously-reported single-layer sensor. The new assembly method facilitates batch-production of the sensor and allows for extension to high temperature measurement.

We report the use of an array of electrically gated ~200 nm solid-state pores as nanofluidic transistors to manipulate the capture and passage of DNA. The devices are capable of reversibly altering the rate of DNA capture by over three orders of magnitude using sub-1V biasing of a gate electrode. This efficient gating originates from the counter-balance of electrophoresis and electroosmosis, as revealed by quantitative numerical simulations. Such a reversible electronically-tuneable biomolecular switch may be used to manipulate nucleic acid delivery in a fluidic circuit, and its development is an important first step towards active control of DNA motion through solid-state nanopores for sensing applications.

The majority of extreme ultraviolet (EUV) lithography mask blank defects originate from chemical mechanical polishing (CMP) of the substrate. The fact that CMP has not yet been able to yield EUV substrates with low defect counts highlights the challenges of polishing doped fused silica surfaces. Here we investigate alternative techniques based on processing either the substrate or coatings of amorphous silicon thin films and inorganic metal oxides. In particular, we evaluate a novel polymer-based non-abrasive a-Si CMP process, a photo-induced dry etching of substrate protrusions, a smoothing coat of spin-on or capillary coated Inpria metal oxide solution, CO2 laser polishing of the substrate surface, and annealing an a-Si thin film surface in reducing atmospheres. Although CMP still remains the best process with respect to overall process integration, these techniques have the potential to support CMP in solving the substrate defectivity issue and help pave the way to commercializing EUV mask blanks.

While the literature is rich with data for the electrical behavior of nanotransistors based on semiconductor nanowires and carbon nanotubes, few data are available for ultrascaled metal interconnects that will be demanded by these devices. Atomic layer deposition (ALD), which uses a sequence of self-limiting surface reactions to achieve high-quality nanolayers, provides an unique opportunity to study the limits of electrical and thermal conduction in metal interconnects. This work measures and interprets the electrical and thermal conductivities of free-standing platinum films of thickness 7.3, 9.8, and 12.1 nm in the temperature range from 50 to 320 K. Conductivity data for the 7.3 nm bridge are reduced by 77.8% (electrical) and 66.3% (thermal) compared to bulk values due to electron scattering at material and grain boundaries. The measurement results indicate that the contribution of phonon conduction is significant in the total thermal conductivity of the ALD films.

We present a sensor capable of detecting solution-based nanoparticles using an optical fiber tip functionalized with a photonic crystal cavity. When sensor tips are retracted from a nanoparticle solution after being submerged, we find that a combination of convective fluid forces and optically-induced trapping cause an aggregation of nanoparticles to form directly on cavity surfaces. A simple readout of quantum dot photoluminescence coupled to the optical fiber shows that nanoparticle presence and concentration can be detected through modified cavity properties. Our sensor can detect both gold and iron oxide nanoparticles and can be utilized for molecular sensing applications in biomedicine., Comment: 13 pages, 5 figures

Nano-Electro-Mechanical (NEM) relays are nano-scale switches that can be mechanically actuated by an electrical signal. Unlike conventional CMOS transistors, NEM relays exhibit zero off-state leakage and very sharp on-off transitions. As a result, NEM relays can be potentially used to design highly energy-efficient digital systems. NEM relays are also excellent candidates for programmable routing switches in Field Programmable Gate Arrays (FPGAs) due to their potentially low on-state resistances despite their long mechanical delays. Low-temperature fabrication of NEM relays creates opportunities for their integration on top of silicon CMOS circuits. Hysteresis properties of NEM relays can enable their use as FPGA programmable routing switches without requiring additional routing SRAM cells. In this talk, we will present an overview of NEM relays and their use in digital system design, and discuss design considerations for hybrid CMOS-NEM FPGAs.

We investigate DNA passage through a nanofluidic transistor (NFT) composed of large diameter nanopores (~200nm) with an embedded metal gate. The nanopores are large enough to be made by currently available photolithography process for manufacturability. We observe that the NFT is capable of electrostatic control of DNA capture rate, the equivalent of current in the electron transistor, with similar operating principle as their electron device counterpart.

This paper demonstrates electrical results of an integrated Si CMOS-electrostatically actuated nanoelectromechanical (NEM) relay circuit. This is an initial step towards realizing previously proposed NEM-CMOS hybrid circuits that predict various benefits compared to CMOS-only circuits. In this work, an e-beam patterned laterally actuated Pt NEM relay is fabricated at CMOS-compatible temperatures (≤ 400 °C) on top of CMOS and is driven by an on-chip CMOS inverter at V DD = 6 V.

We describe a double-layer monolithic silicon photonic crystal (PC) fiber tip sensor. The PC is fabricated using wafer-scale Si processing and epoxy bonding to the fiber. The sensor has sharper resonances and higher sensitivity to refractive index than previously-reported single-layer PC fiber tip sensors. The bonding technique enables batch production.

Microfabricated thermionic emitters form a crucial part of thermionic energy converters, which could find applications in future concentrated solar thermal power plants. Here we report a new stress-relieved design for p-doped and n-doped silicon carbide (SiC) emitters, measurements of their thermionic emission and work functions at temperatures of up to 2900K, and the effect of optical irradiation on both types of SiC emitters. We also report the first observation of the photon-enhanced thermionic emission (PETE) in a thin-film microfabricated emitter.

Laterally actuated nanoelectromechanical (NEM) relays are implemented using a polysilicon structural layer with hafnium oxide (HfO 2 ) and platinum dual sidewall layers. Atomic layer deposition (ALD) HfO 2 provides electrical isolation between the polysilicon beam structure and the sputtered platinum conductive channel. Dual sidewall devices are demonstrated using a Y-shaped device with two contacts that connect source and drain upon actuation. Fabricated devices show up to 1µA current passing between source and drain without beam current flow, confirming successful isolation.

Unlike a traditional capacitive pressure sensor, which uses the entire deflectable diaphragm as the electrode, this paper proposes the use of reduced electrode area to increase the fractional capacitance change and reduce the device's sensitivity to package stresses. Therefore, in addition to the low temperature sensitivity inherent in capacitive sensing, the proposed pressure sensor helps relax signal conditioning requirements typically associated with capacitive sensor interface circuitry.

We present a technique to increase carbon nanotube (CNT) density beyond the as-grown CNT density. We perform multiple transfers, whereby we transfer CNTs from several growth wafers onto the same target surface, thereby linearly increasing CNT density on the target substrate. This process, called transfer of nanotubes through multiple sacrificial layers, is highly scalable, and we demonstrate linear CNT density scaling up to 5 transfers. We also demonstrate that this linear CNT density increase results in an ideal linear increase in drain−source currents of carbon nanotube field effect transistors (CNFETs). Experimental results demonstrate that CNT density can be improved from 2 to 8 CNTs/μm, accompanied by an increase in drain−source CNFET current from 4.3 to 17.4 μA/μm.

HfO x /AlO x bi-layer RRAM devices were fabricated with the atomic layer deposition (ALD) method. Compared with the single-layer HfO x devices, the bi-layer devices showed less variation of the switching voltages and resistances. Inspired by the fact that varying reset stop voltage in a DC sweep can achieve multilevel high resistance state, two equivalent pulse programming schemes were proposed: one linearly increases the reset pulse amplitudes; the other exponentially increases the reset pulse width. The transient current response waveform measurement suggests the former scheme is a more energy efficient programming method.

This work demonstrates the application of pulsed-laser processing for sealing release holes in silicon membranes. Holes in the membrane are sealed without deposition, similar to the silicon surface migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the pulsed-laser process localizes the heat to the top few microns of the substrate, with the bulk kept at near to room temperature. In addition, there is no need for special surface treatment, or for a controlled environment. Furthermore, the treatment can be applied to selected regions of the substrate.

This paper presents an uncooled infrared bolometer using a metal thin film that is formed by atomic layer deposition (ALD). Nanometer-thick freestanding layers enabled by ALD have the potential to improve the performance of bolometers with achieving low thermal conductance and near optimal optical properties. The fabrication and characterization of the first implementation are described as well as the electrical properties of ALD platinum films.

We demonstrate a pH sensor utilizing a layout-programmed squeeze-pumped microfluidic platform. The device is fabricated via direct polydimethylsiloxane (PDMS) micromilling and utilizes an external single-actuator squeeze pump for simultaneous pumping of multiple fluids at different layout-determined flow volumes from 300–9000pL/step. The pumping system, akin to the development of Polaroid instant film, provides an inexpensive means for operating disposable microfluidic devices in the field without external power supplies, valves, or fluidic interface ports. The pH sensor demonstrates functionality of this low-cost, disposable, lab-on-a chip microfluidic detection system.

This paper considers the electromechanical response of electrostatic actuators that are driven by both voltage and charge. The model system is an electrostatic actuator in which the suspended electrode is subjected to a driving voltage and the fixed electrode, which is electrostatically floating, is loaded by charge. The response of the system is analyzed using energy methods, and it is shown that the system has two distinct pull-in voltages. It is also shown that the amplitude of charge on the floating electrode is proportional to the average of these two pull-in voltages. Test-actuators were designed, fabricated, and characterized, and their measured response validates the theoretical predictions. A nondisruptive measurement of charge is proposed and demonstrated which enables to monitor charge decay over time.

Nanoelectromechanical (NEM) relays are promising candidates for programmable routing in Field-Programmable-Gate Arrays (FPGAs). This is due to their zero leakage and potentially low on-resistance. Moreover, NEM relays can be fabricated using a low-temperature process and, hence, may be monolithically integrated on top of CMOS circuits. Hysteresis characteristics of NEM relays can be utilized for designing programmable routing switches in FPGAs without requiring corresponding routing SRAM cells. Our simulation results demonstrate that the use of NEM relays for programmable routing in FPGAs can simultaneously provide 43.6% footprint area reduction, 37% leakage power reduction, and up to 28% critical path delay reduction compared to traditional SRAM-based CMOS FPGAs at the 22nm technology node.

We demonstrate that monolithic 2-dimensional silicon photonic crystals confined to the facet of single-mode optical fibers are capable of determining refractive index and temperature of a sample simultaneously from reflectivity measured at two different wavelengths.

The use of Photonic Crystals (PCs) to control electromagnetic fields enables unprecedented scaling of low-loss, free-space optical devices. In this paper, we describe the operation, design, and fabrication of PC mirrors, and demonstrate their applications in microoptical systems.

This paper reports on lateral nanoelectromechanical (NEM) relays based on variations of a two- or three-mask titanium nitride (TiN) sidewall stringer process. Electrically isolated TiN perimeter beams are fabricated from stringers formed on the inside walls of polysilicon trenches, yielding 200nm wide TiN fins and 200nm gaps; these dimensions are 3X smaller than the resolution limit of the optical lithography tool (600nm) utilized. The reduction in the operating voltage is about a factor of 5 compared to 600nm wide polysilicon beams. Simple scaling could potentially enable sub-1V operation. Five-terminal NEM relays demonstrate successful switching in both directions over 1000 DC-sweep cycles with low drain bias (100mV).

We demonstrate that monolithic 2-dimensional photonic crystals (PCs) confined to the facet, or tip, of single-mode optical fibers can be designed as highly sensitive temperature sensors. Monolithic 2-D photonic-crystals are fabricated on silicon wafers and subsequently released and micro-assembled onto the tip of optical fibers. The PC's reflection spectrum is modulated by the temperature of the sensor and its environment and shows sensitivity comparable to Fiber Bragg Gratings (FBGs). In contrast to FBGs, the compact sensing element is localized at the tip of the fiber and the active sensor element is a disk of 10µm diameter and 480 nm thickness. The sensor system is made of robust, high-temperature dielectric materials and therefore has the potential to be used for many applications including measurements in harsh environments.

We developed a new process for laser-printing a thin-film magnetic-polymer composite microstructural material directly onto planar silicon substrates and characterized its magnetic and mechanical properties. Using this technique we fabricated cantilever beams 100–2000µm long, 100–500µm wide, and 6–8µm thick. An external magnet was used to demonstrate actuation via magnetic field gradient forces, and a scanner was constructed able to deflect a laser beam 3°. This technique takes advantage of advances in commercial laser printing technology and is suitable for low-cost, low-temperature, large-area MEMS devices and rapid MEMS fabrication on a variety of substrates.

Packaging of microelectromechanical systems (MEMS) is a critical step in the transition from product development to production. This paper presents a robust, hermetically-sealed encapsulation method that can accommodate many traditional MEMS devices by allowing large lateral deflection structures within a clean environment. Using the new technology described in this paper, trench widths ranging from 1?m to 100?m were successfully encapsulated at the wafer level while maintaining devices as thick as 20?m. Devices produced with this method have proven durable enough to withstand harsh post-processing such as dicing and wire bonding. Two different types of MEMS resonators are also discussed, demonstrating the use of both large and small trench widths within the encapsulation.

We report on experimental measurements of the optical properties of thin films of poly-crystalline silicon carbide (poly-SiC) deposited by means of low pressure chemical vapor deposition (LPCVD). Measurements in the mid-IR region of the EM spectrum show strong dependence of both far field transmission and surface modes upon the deposition conditions including doping levels, ratio of dichlorosilane (DCS) to 1,3 disilabutane (DSB), and anneals performed on the film. We observe the link between the relative strength of near field phonon polariton resonances, the appearance of a polariton gap, and the achievement of extraordinary optical transmission (EOT).

This paper describes a microelectromechanical resonator interface to a nanomechanical structure. Our approach to microresonator-nanowire integration employs silicon nanowires as mechanical tuning elements, which perturb the frequency response of the resonator system. Two coupling configurations were designed and tested, the first with a nanowire beam coupled to the maximum displacement points of clamped-clamped microresonators and the second with a coupling beam attached 1.5 mum away from the anchors of the bending mode resonators. A focused-ion-beam (FIB) tool was used to tune the frequency response of the coupled systems. Finally a nanowire coupled bandpass filter with a 3 dB bandwidth about 120 kHz at 17.9 MHz was demonstrated.

The operation and performance of complementary nanoelectromechanical (CNEM) logic gates are investigated. NEMS structures featuring dimensions 2 to 3 orders of magnitude smaller than the present MEMS relays are considered. Various metals are benchmarked to silicon as the cantilever beam material. We show that the CNEM inverters featuring laterally actuated beams, 10 nm gap and low density materials such as Si or Al can achieve nanosecond pull-in delay and sub-0.1 fJ switching energy at VDD = 1.5 V while occupying an area as small as 0.03 mum2.

We report on the experimental observation of the effect of periodic hole arrays in the infrared reflection spectra of suspended polycrystalline silicon carbide (poly-SiC) membranes. The poly-SiC was deposited by low pressure chemical vapor deposition (LPCVD), patterned with contact photolithography, and etched by reactive ion etching (RIE). The spectra are shown to be strongly dependent on the pitch and aperture size of the hole arrays, indicating poly-SiC has promise as a mid-IR optical material.

We report on the effect of stacking a pair of metallic subwavelength hole arrays on the extraordinary transmission spectrum. A novel fabrication process was developed to create a self-aligned vertical stack of subwavelength metal gratings with precise control of the separation between the two metal films. For separations within the coupling region of the evanescent surface modes of the metal films, minor sharpening of the transmission filter characteristics was observed.

As Navy warships transition to the "Electric Ship"paradigm, technologies capable of automatically monitoring and remotely controlling the systems involved in distribution of electric power become a significant consideration for reducing manpower, improving reliability and facilitating Distance Support. DRS TCS has developed a network design, the "Networked Intelligent Instrumentation & Control System for Switchboards (NPCS) ", that is capable of providing automated monitoring and control of all the ship power systems from a centralized location. Notably, adding to the cost benefits of the approach, it is achieved through a dedicated Local Area Network (LAN), such as the US Navy's Fiber Optic Data Multiplex System (FODMS). Coupling this proposed system with advancements in current and developing sensor measuring technology also provides increased diagnostic capability and a drastic reduction in sensor component weight when compared with conventional techniques. This synergistic analysis and maintenance network provides a streamlined interface to power distribution equipment while providing an increased level of reliability and the capability to build on a rich feature set including data trending, power consumption analyses, and full reconfiguration of power distribution. It permits rapid reaction to emergency situations and user-friendly maintenance. Most importantly in an era of minimally manned ships, it has the potential to reduce traditional manpower requirements.

This paper reports on the integration of subwavelength metal gratings with surface micro-machined, electrostatic MEMS actuators to produce a tunable electromagnetic filter. Metal films perforated with periodically-spaced subwavelength diameter holes have been shown to transmit light with greater efficiency than predicted by classical models for evanescent propagation. Additionally, the field propagation shows strong dependance on the index of refraction on either surface of the metal. This characteristic performance leads to electric field enhancement at the apertures in the metal, an effect that holds promise for nanoscale optical sensors. We describe our work on the integration of MEMS electrostatic actuators with patterned metal films that were interrogated using infrared (IR) radiation. We report a transmission modulation factor of 7 with an actuation voltage of 46V.

The first reported square array of subwavelength holes patterned with nanoimprint lithography in an aluminum film is presented. Optical modes vary linearly with the refractive index of the fluid in contact with the aluminum grating

Metal films perforated with periodically-spaced subwavelength diameter holes have been shown to transmit light with greater efficiency than predicted by classical models for evanescent propagation. This transmission mechanism is caused either by the coupling of light to surface plasmon polariton modes on the surfaces of the metal film or by diffraction patterns in the lateral evanescent modes of electromagnetic field. Regardless of the root cause, this characteristic performance leads to electric field enhancement at the apertures in the metal, an effect that holds promise for nanoscale optical sensors. In particular, the propagation of these modes is very sensitive to changes in the index of refraction on either surface of the metal. This paper will describe our work on patterned metal films which are interrogated using infrared (IR) radiation. These metal gratings are fabricated using a surface micromachining process, allowing MEMS actuators to be integrated alongside the optically-active surface. The integration of MEMS structures with subwavelength optical structures can be used to create structures whose optical properties are modulated by changes in the position of a MEMS element, resulting in mechanical sensors and tunable optical filters. We will describe structures in which small changes in the separation between the metal film and a dielectric substrate result in large changes in the optical transmission and reflection spectra.

We report on an Optical Add/Drop Multiplexer designed from a single Arrayed Waveguide Grating and a MEMS optical switch. Three different MEMS switches were tested, the most promising being a potentially integrable binary actuator array.

We demonstrate embedding of chiplets into wafers to bypass the monolithic integration challenges of combining micro-mechanical devices with active circuitry. Dry alignment is provided by passive guide tabs, which are created through polysilicon refill of frontside etched trenches. The guide tabs are compatible with further processing on the wafer. Precision chiplets are created by through-wafer etching. After chiplet drop-in, optical detection provides feedback of chiplet jamming, and horizontal driving of the chiplets finishes the zero insertion force assembly process. We demonstrate less than 2.5 µm of chiplet to substrate alignment error. Theoretical scaling of alignment accuracy reaches numbers comparable to photolithography, allowing high density interconnects for heterogeneous integration without precision manipulators.

We demonstrate a simple and rapid epoxy-based method for transferring photonic crystal cavities to the facets of optical fibers. Passive Si cavities were measured via fiber taper coupling as well as direct transmission from the fiber facet. Active quantum dot containing GaAs cavities showed photoluminescence that was collected both in free space and back through the original fiber. Cavities maintain a high quality factor (2000-4000) in both material systems. This new design architecture provides a practical mechanically stable platform for the integration of photonic crystal cavities with macroscale optics and opens the door for novel research on fiber-coupled cavity devices., Comment: 10 pages, 5 figures

This article describes direct laser printing of thin-film polymer onto rigid substrates for use as an etch mask or liftoff layer in patterning on-chip electrical components. Using this technique, the authors fabricated planar spiral inductors of 12×12mm2 with 2.5–5.5 turns producing series inductance Ls=80–180nH as well as planar interdigitated capacitors of 10×10mm2 with two to nine fingers producing series capacitance Cs=100–1600nF. This technique is a low cost, low temperature, rapid turn around, maskless, resist-free means of patterning device features as small as 130μm.

Silicon migration in four nonreducing gas ambients of helium, neon, argon, and nitrogen at a low pressure (10 ―3 Torr) and in an ultrahigh vacuum (10 ―9 Torr) is studied by monitoring the effect on microfabricated trench structures after a 5 min anneal at 1000°C in each environment. The measurements of the trench corner curvature are used to extract the relative migration rates for each ambient. The migration rate has no ambient gas dependence for the noble gases at 10- 3 Torr and has pressure dependence in the 10 ―3 ―10 ―9 Torr range.