Silicon micro-cantilever chemical sensors fabricated in double-layer silicon-on-insulator (SOI) wafer

Micro-cantilever piezoresistive sensors are optimally designed and fabricated in a double-layer silicon-on-insulator (SOI) wafer. The sensor geometry is optimized by placing the sensing piezoresistor at the cantilever root region to increase effective piezoreisistive sensing area. According to finite-element simulation results, high sensitivity can be obtained by design the cantilever into a wide and short shape. In order to use single-crystalling silicon to fabricate both the cantilever and the piezoresistor for high sensitivity, double-layer SOI wafer, which has two active layers and two insulating layers, is proposed to fabricate the self-sensing micro-cantilever sensor. The piezoresistor is made of the top active-layer single-crystalline silicon. Without p–n junction isolation, such a piezoresistor can be free from leakage-current relative noise that helps to achieve fine sensing resolution. The bottom active-layer is used to form the cantilever, with well controlled cantilever thickness and high fabrication yield. With the top surface of the micro-cantilever is modified with the functionalized self-assembled monolayer, detection of trace-concentration Trinitrotoluene (TNT) vapor is experimentally carried out, with reproducible sensing response to 7.6 ppb TNT.     

Electromagnetically actuated biaxial scanning micromirror fabricated with silicon on glass wafer

In this paper, we present an electromagnetically actuated two-axis scanning micromirror with large aperture and tilting angle for laser pointing applications. The two-axis micromirror with the plate size of 3 mm in diameter was realized using gimbaled single crystal silicon with a single-turn electroplated copper coil, and it was assembled with permanent magnets forming radial magnetic field. The micromirror was fabricated on SiOG (Silicon on Glass) wafer using 4 photolithography masks. The permanent magnet assembly composed of a cylindrical and a ring-type magnet was designed to optimize the radial magnetic field, and thus maximize the torque on the coil. Three different magnet assemblies were applied to the fabricated micromirror in order to verify the design. Horizontal resonance frequency of the fabricated micromirror was measured 1.421 kHz and vertical resonant frequency was 396 Hz. The vertical scan angle was 16.87°, 26.32° and 22.61° with the cylindrical magnet diameter of 2.6, 4.0 and 4.8 mm, respectively, at 60 Hz sinusoidal input of 640 mA_pp. For horizontal scan, maximum scan angle of 24.45° was obtained at 48 mA_pp input signal in resonance mode. In addition, the temperature distribution on the micromirror surface was measured with the applied current to the coil.

     

Micron-scale polymer-metal cantilever actuators fabricated by focused ion beam

Polymer-metal microcantilever actuators have been fabricated using an innovative approach based on focused ion beam micromachining technology. The fabrication involves depositing a thin metal film onto the surface of the polymer and machining using the ion beam. The microcantilever created is then extracted and transferred to a desirable support using a micromanipulator. This approach demonstrates the potential for maskless and resistless prototyping of cantilevers that can be evaluated for use as MEMS/NEMS actuators. Nanometer-scale displacement of the resulting polystyrene-platinum bimorph microactuator with respect to temperature change is demonstrated via visual monitoring in a scanning electron microscope with a heating stage. The performance of the bimorph cantilever microactuators is verified using both analytical and finite element modeling.     

Cubic millimeter power inductor fabricated in batch-type wafer technology

A hybrid technology for the realization of three-dimensional (3-D) miniaturized power inductors is presented. Our devices consist of planar Cu coils on polyimide substrates, and mm-size ferrite magnetic cores, obtained by three-dimensional micro-patterning of ferrite wafers using powder blasting. The coils are realized using an in-house developed high-resolution polyimide spinning and Cu electroplating process. Winding widths down to 5 /spl mu/m have been obtained and total device volumes are ranging between 1.5 and 10 mm/sup 3/. Inductive and resistive properties are characterized as a function of frequency; inductance values in the 100 /spl mu/H range have been obtained.     

An Analytical Subthreshold Swing Model for fully-depleted MOSFETs with vertical Gaussian profile fabricated on modified silicon-on-insulator wafers

Microsystem Technologies - The objective of this study is to present an analytical subthreshold swing model for fully-depleted metal-oxide semiconductor field-effect transistors (MOSFETs) with...     

CO_2激光器加工晶圆切缝控制工艺研究

晶体硅是当前最重要的半导体材料,主要用于微电子技术。随着微电子技术的发展,对晶圆的切割技术要求越来越高,而在实际切割中,对晶圆的切割十分注重于晶圆的切割宽度,以降低晶圆损耗。研究CO2激光切割机的脉宽、频率以及切割速度对晶圆切割宽度的影响,从而达到高效率、小宽度、高标准的激光切割加工。     

A bulk-micromachined bistable relay with U-shaped thermal actuators

This paper reports a deep-reactive ion etching (DRIE)-through-etched laterally bistable MEMS relay for power applications, with a primary emphasis on the design and modeling of its U-shaped transient thermal actuators, and a secondary emphasis on the design and fabrication of its contact element. In this relay, a contact crossbar is carried by a curved-beam bistable mechanism , which is toggled by transient U-shaped thermal actuators with their hot beam adiabaticly heated by electrical pulses. Each U-shaped thermal actuator comprises uniform-thickness hot and cold beams with a gap between them so they bend differently. This paper develops both a basic model and a complete model for the actuator that are verified by Finite Element Analysis and serve as effective design tools. The DRIE process creates nonideal etched surfaces, which pose challenges for good relay contacts. Both contact design and process development are discussed to help alleviate this problem. The fabricated relay exhibits a minimum total on-state resistance of 60 m/spl Omega/, and a maximum current carrying capacity of 3 A. It switches with a 1 ms actuation pulse, and a maximum 5 Hz repetition rate.     

A MEMS sandwich differential capacitive silicon-on-insulator accelerometer

A differential capacitive accelerometer with simple process is designed, simulated, and fabricated. To achieve a precision structure dimension with fewer processing steps, the silicon device layer transfer technology is being used to built a sandwich accelerometer based on a silicon-on-insulator (SOI) wafer, which was assembled by glass-si-glass multilayer anodic bonding. Deep reactive ion etching is being used to define symmetric beams and large mass block of equal thickness together in SOI device layer (up to 100 μm) in a single step to avoid alignment error in double side process. An actual accelerometer which is designed for 50 g measure range is fabricated with six lithography steps. Measurement results show 0.1166 V/g sensitivity and 0.022 % nonlinearity error in ±1 g gravity static response test. The accelerometer also provides a power spectrum less than 10.49 μVrms/Hz^1/2 (89.97 μg/Hz^1/2) in a non-isolated laboratory environment with a capacitive interface circuit.     

A corrective feedback design for nonlinear systems with fast actuators

Recent two-time-scale results can be derived from a geometric framework which allows further extensions and computational improvements. In this note the two-time scale behavior of singularly perturbed systems is exploited to design slow and fast controls and to combine them into a composite control. As an illustration, we present a corrective design to compensate for fast actuator dynamics modeled as singular perturbations.     

A non-linear controller design method for processes with saturating actuators

An optimization approach is proposed to derive non-linear model-based control laws for non-linear processes with actuator saturation non-linearities. The derived control laws induce a linear closed-loop process output response in the absence of input constraints (are input-output linearizing), are able to minimize the mismatch between the constrained and the linear unconstrained process output responses, and inherently include optimal directionality and windup compensators. Connections between the derived control laws and (a) already available, input-output linearizing, non-linear, control methods, (b) modified internal model control, and (c) model state feedback control, are established. The application and performance of the derived control laws are shown by examples.     

A microvalve matrix using piezoelectric actuators

 A microvalve matrix is proposed for controlling gas flow. Mircovalves in the matrix are controlled independently and each one handles a very small gas flow. The microvalve matrix can thus control gas flows precisely in very small steps, over the range from zero flow to fully-open flow, by digitally opening and closing the appropriate number of microvalves. The microvalve proposed for this matrix has a compact and simple design for a high degree of integration. This valve is normally closed and is opened by using the deformation of the port caused by the piezoelectric effect. Calculations show that a microvalve smaller than 1×1 mm can handle a maximum gas flow rate of the order of 10^-4 Pa m³/s (Air, 20 °C). It is easy to reduce the flow rate. Therefore these results indicate that a microvalve matrix can achieve wide dynamic-range flow-control in small flow steps. Received: 1 November 1996/Accepted: 14 November 1996     

Variable impedance actuators: A review

Variable Impedance Actuators (VIA) have received increasing attention in recent years as many novel applications involving interactions with an unknown and dynamic environment including humans require actuators with dynamics that are not well-achieved by classical stiff actuators. This paper presents an overview of the different VIAs developed and proposes a classification based on the principles through which the variable stiffness and damping are achieved. The main classes are active impedance by control, inherent compliance and damping actuators, inertial actuators, and combinations of them, which are then further divided into subclasses. This classification allows for designers of new devices to orientate and take inspiration and users of VIA’s to be guided in the design and implementation process for their targeted application.     

A hermetic glass-silicon micropackage with high-density on-chipfeedthroughs for sensors and actuators

This paper describes the development of a hermetic micropackage with high-density on-chip feedthroughs for sensor and actuator applications. The packaging technique uses low-temperature (320°C) electrostatic bonding of a custom-made glass capsule (Corning 7740, 2×2×8 mm³) to fine grain polysilicon in order to form a hermetically sealed cavity. High-density on-chip multiple polysilicon feedthroughs (200 per millimeter) are used for connecting external sensors and actuators to the electronic circuitry inside the package. A high degree of planarity over feedthrough areas is obtained by using grid-shaped polysilicon feedthrough lines that are covered with phosphosilicate glass (PSG), which is subsequently reflown at 1100°C in steam for 2 h. Saline and DI water soak tests at elevated temperatures (85 and 95°C) were performed to determine the reliability of the package. Preliminary results have shown a mean time to failure (MTTF) of 284 days and 118 days at 85 and 95°C, respectively, in DI water. An Arrhenius diffusion model for moisture penetration yields an expected lifetime of 116 years at body temperature (37°C) for these packages. In vivo tests in guinea pigs and rats for periods ranging from one to two months have shown no sign of infection, inflammation, or tissue abnormality around the implanted package     

A virtual prototyping system with reconfigurable actuators for multi-material layered manufacturing

Proliferation of layered manufacturing (LM) in various sectors has been calling for fabrication of large, complex products with more materials and efficiency. We address this issue by integrating reconfigurable manufacturing (RM) with LM. This paper first analyses the benefits of such integration, and then presents a virtual prototyping system with reconfigurable actuators (VPRA) that can increase the number of materials, speed, and build volume to improve the efficiency and flexibility of multi-material layered manufacturing (MMLM). The VPRA system offers a test bed for design, visualization, and validation of MMLM facilities and processes. It takes advantage of the convenient graphics platform of SolidWorks™ for constructing a virtual MMLM facility by selecting reconfigurable actuators from predefined templates. The characteristics, including the dimensions and relative spatial constraints, of the actuators can be conveniently configured to suit design requirements. The mechanism and the operation process of the resulting MMLM facility can then be simulated and validated through digital fabrication of complex objects. Case studies are presented to demonstrate some possible applications of the VPRA system. Overall, the VPRA system gives insights into the characteristics of a reconfigurable MMLM system, which can be subsequently materialized for physical fabrication of multi-material objects. This approach highlights a possible direction for development of MMLM technology.     

Dynamic controllers for systems with actuators

The stabilization of a continuous-time system under the action of a dynamic feedback controller including a saturating actuator is examined. Sufficient conditions in terms of certain matrix-norm inequalities are developed, the satisfaction of which guarantees both the uniform asymptotic and BIBO stability of the closed-loop control system. A computational algorithm is designed and implemented on a typical example     

Peristaltic micropump system with piezoelectric actuators

This work presents a driving system for a peristaltic micropump that is based on piezoelectric actuation. The effects of the actuation sequence on pump performance are also considered. A valveless peristaltic micropump based on piezoelectric actuation is designed and fabricated using microelectromechanical system technology. The pump has three parts––silicon, Pyrex glass and commercially available bulk PZT (lead zirconate titanate) chips. The peristaltic micropump actuated by PZT chips comprises three chambers that are in series. The driving system consists of an ATmega 8535 microprocessor, a high voltage power supply, three differential amplifiers, a phase controller, an A/D converter, a 555 oscillator and an LCD module. It is supplied via a 110 Vrms 60-Hz AC line and is programmable. The system can produce step-function signals with voltages of up to 100 V_pp and frequencies ranging from 10 Hz to 1 kHz, as the inputs for the pump. Fluid pumping with air is successfully demonstrated. Additionally, 3-, 4- and 6-phase actuation sequences for the pump are designed and used to study the effects on pump performance, as revealed by the flow rate and the displacement of a pump diaphragm. The experimental results show that the flow rate and the displacement of the diaphragm actuated by the 4-phase sequence exceed those actuated by the 3- and 6-phase sequences. A flow rate of 17.6 μl min⁻¹ and a displacement of 2.91 μm (peak-to-peak) in 4-phase peristaltic motion are achieved at 100 Hz and 100 V_pp. The results demonstrate that the pump actuated in the 4-phase sequence is the most efficient. Consequently, the actuation sequences can affect the pump performance.     

A new inverse kinematics algorithm for binary manipulators with many actuators

In this paper we present a new, and extremely fast, algorithm for the inverse kinematics of discretely actuated manipulator arms with many degrees of freedom. Our only assumption is that the arm is macroscopically serial in structure, meaning that the overall structure is a serial cascade of units with each unit having either a serial or parallel kinematic structure. Our algorithm builds on previous works in which the authors and coworkers have used the workspace density function in a breadthfirst search for solving the inverse kinematics problem. The novelty of the method presented here is that only the 'mean' of this workspace density function is used. Hence the requirement of storing a sampled version of the workspace density function (which is a function on a six-dimensional space in the case of a spatial manipulator) is circumvented. We illustrate the technique with both planar revolute and variable-geometry-truss manipulators, and briefly describe a new manipulator design for which this algorithm is applicable.     

Exact gradient controllability with strategic actuators

In this paper, we develop results related to the gradient controllability and actuators. The concept of gradient strategic actuators is characterized and applied to the gradient controllability of systems described by a hyperbolic equation. This emphasizes the spatial structure and the location of the actuator in order to achieve the gradient controllability. We combine the Hilbert uniqueness method and the characterization of the strategic actuators to solve the gradient controllability problem for the wave equation. The developed results are illustrated by many examples of specific shapes and systems.