Standalone Tensile Testing of Thin Film Materials for MEMS/NEMS Applications

The microelectronics industry has been consistently driven by the scaling roadmap, colloquially referred to as the Moore’s law. Consequently, during the past decades, integrated circuits have scaled down further. This shrinkage could have never been possible without the efficient integration and exploitation of thin film materials. Thin film materials, on the other hand, are the essential building blocks of the micro- and nano-electromechanical systems (MEMS and NEMS). Utilization of thin film materials provides a unique capability of further miniaturizing electromechanical devices in micro- and nano-scale. These devices are the main components of many sensors and actuators that perform electrical, mechanical, chemical, and biological functions. In addition to the wide application of thin film materials in micro- and nano-systems, this class of materials has been historically utilized in optical components, wear resistant coatings, protective and decorative coatings, as well as thermal barrier coatings on gas turbine blades. In some applications, thin film materials are used mainly as the load-bearing component of the device. Microelectromechanical systems (MEMS) are the example of these applications. Thin film materials carry mechanical loads in thermal actuators, switches and capacitors in RF MEMS, optical switches, micro-mirror hinges, micro-motors, and many other miniaturized devices. In these applications, one of the main criteria to choose a specific material is its ability to perform the mechanical requirements. Therefore, a clear understanding of the mechanical behavior of thin film materials is of great importance in these applications. This understanding helps better analyze the creep in thermal actuators (Tuck et al., 2005; Paryab et al., 2006), to investigate the fatigue of polysilicon (Mulhstein et al., 2001; Shrotriya et al., 2004) and metallic micro-structures (Eberl et al., 2006; Larsen et al., 2003), to scrutinize the relaxation and creep behavior of switches made of aluminum (Park et al., 2006; Modlinski et al., 2004) and gold films (Gall et al., 2004), to study the hinge memory effect (creep) in micro-mirrors (Sontheimer, 2002), and to address the wear issues in micro-motors. (van Spengen, 2003) In some other applications, the thin film material is not necessarily performing a mechanical function. However, during the fabrication process or over the normal life, the device experiences mechanical loads and hence may suffer from any of the mechanical failure issues. Examples of these cases are the thermal fatigue in IC interconnects (Gudmundson & Wikstrom, 2002), strain ratcheting in passivated films (Huang et al., 2002; He et al., 2000), the fracture and delamination of thin films on flexible substrates (Li & Suo, 2006), the fracture of porous low-k dielectrics (Tsui et al., 2005), electromigration (He et al., 2004), the chip-package-interaction (CPI) (Wang & Ho, 2005), and thin film buckling and delamination (Sridhar et al., 2001). In order to address the above-mentioned failure issues and to design a device that has mechanical integrity and material reliability, an in-depth knowledge of the mechanical behavior of thin film materials is required. This information will help engineers integrate materials and design devices that are mechanically reliable and can perform their specific functions during their life-time without any mechanical failure. In addition to the tremendous industrial and technological driving force that was mentioned earlier, there is a strong scientific motivation to study the mechanical behavior of thin film materials. The mechanical behavior of thin film structures have been known to drastically differ from their bulk counterparts. (Xiang, 2005) This discrepancy that has been referred to as the length-scale effect has been one of the main motivations in the scientific society to study the mechanical behavior of thin film materials. In order to provide fundamental mechanistic understanding of this class of materials, old problems and many of the known physical laws in materials science and mechanical engineering have to be revisited from a different and multidisciplinary prospective. These investigations will not be possible unless a concrete understanding of the mechanical behavior of thin film materials is achieved through rigorous experimental and theoretical research in this area.Natural Sciences and Engineering Research Council (NSERC) of Canad

An interdisciplinary approach to the nanomanipulation of SiO2 nanoparticles. Design, fabricationand feasibility

Although some recent developments in nanotechnology made the prospects of a direct mechanical manipulation of micro- or nano-objects quite realistic, there are still several concerns and difficulties that affect such an endeavor. This is probably due to the large base of knowledge that is necessary to approach the problem of handling a nano-object by means of a nano- or micro-device. Therefore, any progress in this field is possible only by means of an integrated and interdisciplinary approach, which takes into account different aspects of the phenomenon. During the actual pioneering phase, there is a certain convenience in handling nano-objects that: (a) have peculiar known characteristics; (b) are easily recognizable, and (c) are interesting to the scientific community. This paper presents the interdisciplinary activities that were necessary to set up an experiment where specifically synthesized SiO2 particles came in contact with the tips of specifically-designed and -fabricated nanomanipulators. SiO2 mesoporous nanoparticles (KCC-1), having a peculiar dendritic structure, have been selected as a suitable nano-object because of the possibility to easily modulate their morphology. The expected contact force has been also calculated by means of Finite Element Analysis (FEA) electro-mechanical simulations

Workshop on "Control issues in the micro / nano - world".

International audienceDuring the last decade, the need of systems with micro/nanometers accuracy and fast dynamics has been growing rapidly. Such systems occur in applications including 1) micromanipulation of biological cells, 2) micrassembly of MEMS/MOEMS, 3) micro/nanosensors for environmental monitoring, 4) nanometer resolution imaging and metrology (AFM and SEM). The scale and requirement of such systems present a number of challenges to the control system design that will be addressed in this workshop. Working in the micro/nano-world involves displacements from nanometers to tens of microns. Because of this precision requirement, environmental conditions such as temperature, humidity, vibration, could generate noise and disturbance that are in the same range as the displacements of interest. The so-called smart materials, e.g., piezoceramics, magnetostrictive, shape memory, electroactive polymer, have been used for actuation or sensing in the micro/nano-world. They allow high resolution positioning as compared to hinges based systems. However, these materials exhibit hysteresis nonlinearity, and in the case of piezoelectric materials, drifts (called creep) in response to constant inputs In the case of oscillating micro/nano-structures (cantilever, tube), these nonlinearities and vibrations strongly decrease their performances. Many MEMS and NEMS applications involve gripping, feeding, or sorting, operations, where sensor feedback is necessary for their execution. Sensors that are readily available, e.g., interferometer, triangulation laser, and machine vision, are bulky and expensive. Sensors that are compact in size and convenient for packaging, e.g., strain gage, piezoceramic charge sensor, etc., have limited performance or robustness. To account for these difficulties, new control oriented techniques are emerging, such as[d the combination of two or more ‘packageable' sensors , the use of feedforward control technique which does not require sensors, and the use of robust controllers which account the sensor characteristics. The aim of this workshop is to provide a forum for specialists to present and overview the different approaches of control system design for the micro/nano-world and to initiate collaborations and joint projects

Hybrid Microassembly in Environmental Scanning Electron Microscope Using Robotic Manipulator and Adhesives

Peer reviewe

The Performance Evaluation of SMA Spring as Actuator for Gripping Manipulation

This paper is to present the evaluation of a TiNi Shape Memory Alloy (SMA) spring as actuator for the gripping manipulation. The SMA spring employed was a TiNi tensile spring which has a diameter of 50 mm wire and 350 gram hanging mass. The gripper fabricated consists of two fingers and each finger is actuated by the SMA spring. The total angular displacement of the gripper is 300. The power consumptions, the movements and force generations experimentations have been conducted. The DC signal and PWM signal with 12, 12Hz, 25Hz, 125Hz, 250Hz and the 1150Hz have been employed for driving the SMA. The experimental results indicated that the 125Hz of PWM signal was likely to be had a better performance than the other signals. The 125Hz PWM signal generated faster movement, lower power consumption, and constant rate of force. In this study, closed-loop control for gripping manipulation was also conducted. The close loop controller used is PID controller. The Ziegler-Nichols method has been used to predict the optimal gain of the controller, but the best performance was determined by experimentally tuning of the gains. The experimental results indicated that the PID controller is likely to be reliable controller for gripping manipulation of the SMA spring. To obtain the better performance, it is important to consider the SMA cooling responses and the long time of retain in certain position of the gripper

Grasping and releasing agarose micro beads in water drops

The micromanipulation of micro objects is nowadays the focus of several investigations, specially in biomedical applications. Therefore, some manipulation tasks are required to be in aqueous environment and become more challenging because they depend upon observation and actuation methods that are compatible with MEMS Technology based micromanipulators. This paper describes how three grasping-releasing based tasks have been successfully applied to agarose micro beads whose average size is about 60 \u3bcm: (i) the extraction of a single micro bead from a water drop; (ii) the insertion of a single micro bead into the drop; (iii) the grasping of a single micro bead inside the drop. The success of the performed tasks rely on the use of a microgripper previously designed, fabricated, and tested

Recursive Least Squares Filtering Algorithms for On-Line Viscoelastic Characterization of Biosamples

The mechanical characterization of biological samples is a fundamental issue in biology and related fields, such as tissue and cell mechanics, regenerative medicine and diagnosis of diseases. In this paper, a novel approach for the identification of the stiffness and damping coefficients of biosamples is introduced. According to the proposed method, a MEMS-based microgripper in operational condition is used as a measurement tool. The mechanical model describing the dynamics of the gripper-sample system considers the pseudo-rigid body model for the microgripper, and the Kelvin–Voigt constitutive law of viscoelasticity for the sample. Then, two algorithms based on recursive least square (RLS) methods are implemented for the estimation of the mechanical coefficients, that are the forgetting factor based RLS and the normalised gradient based RLS algorithms. Numerical simulations are performed to verify the effectiveness of the proposed approach. Results confirm the feasibility of the method that enables the ability to perform simultaneously two tasks: sample manipulation and parameters identification

NEMS by sidewall transfer lithography

A batch fabrication process for nano-electro-mechanical systems (NEMS) based on sidewall transfer lithography (STL) is developed and demonstrated. The STL is used to form nanoscale flexible silicon suspensions entirely by conventional lithography. A two-step process is designed for single-layer STL to fabricate simple electrothermal actuators, while a three-step process is designed to allow nanoscale features intersecting with each other for more complicated device lay-outs. Fabricated nanoscale features has a minimum in-plane width of approx. 100nm and a high aspect ratio of 50 : 1. Combined structures with microscale and nanoscale parts are transferred together into silicon by deep reactive etching (DRIE). Suspensions are achieved either by plasma undercut or HF vapour etch based on BSOI. The STL processes are used to form nanoscale suspensions while conventional lithography is used to form localised microscale features such as anchors. A wide variety of demonstrator devices have been fabricated with high feature quality. Analytic models have been developed to compare with experimental characterization and finite element analysis (FEA) predictions. Lattice structures fabricated by multi-layer STL have also be investigated as a novel type of mechanical metamaterial. Thus, the process could allow low-cost and mass parallel fabrication of future NEMS with a wider range of potential applications.Open Acces