Detecting and quantifying mountain permafrost creep from in situ inventory,space-borne radar interferometry and airborne digital photogrammetry

In this paper three different techniques for detecting and quantifying mountain permafrost creep are compared: (1) rock glacier inventory and characterization from in situ indicators, (2) space-borne radar interferometry, and (3) digital processing of repeated airborne imagery. The specific characteristics of the three methods and their complementarity are investigated for the Fletschhorn mountain range in the Simplon/Saas valley region, Swiss Alps. We found that radar interferometry is suitable to quantify the degree of activity and the order of surface velocity of rock glaciers over large areas in one process, with the possibility to also detect very small movements of inactive and relict rock glaciers. On the other hand, aero-photogrammetry represents a valuable base for additional interpretation of the three-dimensional surface flow field (including speed, direction and change in thickness) of the most active rock glaciers. Results from radar interferometry can also form the basis for further detailed in situ investigations.     

An evaluation of optical profilometry techniques for CMUT characterization

Accurate characterization of thin films and geometric features including the cavities during and after the fabrication process is crucial for proper CMUT operation, reliability, consistent array operation, and improved yield. Three different optical profilometry techniques: white light interferometry, laser confocal microscopy, and structural grid illumination microscopy have been reviewed in this paper with a focus on characterization of various thin films and geometric features during different CMUT fabrication stages and post processing. The relative merits of each technique have been investigated experimentally in the context of CMUT fabrication for better characterization and process development. The surface roughness and diaphragm deformation results have also been compared with AFM data. From the review, it appears that characterization needs of CMUTs are unique and a combination of complex diversified characterization tools is necessary to generate sufficient data for design verification and functional optimization.

     

Microscale material characterization and viscoelastic modeling of organic dielectic thin film in eWLB package

This paper is supposed to discuss the suitability to identify material parameters via nanoindentation of a viscoelastic dielectric thin film attached to a rigid substrate. In microelectronic components, polymer thin films used as packaging materials are gaining more and more importance, thus the full thermo-mechanical characterization of these materials is highly desired. Therefore, in this paper the problem of indentation into a geometrically confined thin film is indicated. With the help of FEM simulations, a function which accounts for the substrate influence in spherical nanoindentation is developed and integrated in the viscoelastic analysis of material parameters. By using a precise laser heat option as add on to the standard nanoindenter equipment (Agilent G200), time and temperature dependencies could be identified in micro scale and compared to conventional thermo-mechanical macroscopic thin film characterization. In both size scales, material models were established and verified in FEM simulation of sphere indentation. Transfering viscoelastic material characterization via nanoindentation onto thin polymer films over a wide range of temperatures and comparing microscopic and macroscopic results, as shown in this paper, is still not a well explored research field.     

Real time thickness measurement of thin film for end-point detector (EPD) of 12-inch spin etcher using the white light interferometry

A real time thickness measurement method based on the wide band white light interferometry for spin etcher is presented for the silicon-oxide and poly-silicon film deposited on 12-inch silicon wafer subject to a rotational vibration and chemical flow. Mathematical model for the vibration and chemical flow is described using a statistical method and analyzed to investigate their effects on the interference of reflected lights from the thin films. A white light interferometry system for the real time thickness measurement of thin films have been also developed to evaluate the performance of the method in experiment and determine the thickness of the films using signal processing techniques including curve-fitting and adaptive filtering. Experiments conducted for thin films ranging form 100 nm to 600 nm in thickness show that the method proposed in the paper is proved to be effective with a good accuracy of maximum 1.8% error.     

Piezoresistance in chemically synthesized polypyrrole thin films

The resistance of chemically synthesized polypyrrole (PPy) thin films is investigated as a function of the pressure of various gases as well as of the film thickness. A physical, piezoresistive response is found to coexist with a chemical response if the gas is chemically active, like, e.g., oxygen. The piezoresistance is studied separately by exposing the films to the chemically inert gases such as nitrogen and argon. We observe that the character of the piezoresistive response is a function not only of the film thickness, but also of the pressure. Films of a thickness 70 nm show a decreasing resistance as pressure is applied, while for thicker films, the piezoresistance is positive. Moreover, in some films of thickness ≈70 nm, the piezoresistive response changes from negative to positive as the gas pressure is increased above ≈500 mbar. This behavior is interpreted in terms of a total piezoresistance which is composed of a surface and a bulk component, each of which contributes in a characteristic way. These results suggest that in polypyrrole, chemical sensing and piezoresistivity can coexist, which needs to be kept in mind when interpreting resistive responses of such sensors.     

Ultra thin chips for miniaturized products

The demand to miniaturize products especially for mobile applications and autonomous systems is continuing to drive the evolution of electronic products and manufacturing methods. One key to miniaturization developed in the past was the use of unpackaged, bare dice. Saving the volume and weight of the package, significant reduction in footprint was achieved. A next step conceived to further the miniaturization is the integration of functions on miniaturized subsystems, i.e. System-in-Package (SiP), in contrast to a full silicon integration (System-on-Chip, SoC). The use of recent manufacturing methods allows to merge the SiP approach with a volumetric integration. Up to now, most of the systems utilize single- or double-sided populated system carriers. Embedding of passive components was a first step forward. A new challenge is to incorporate not only passive components, but active circuitry (IC's) and the necessary thermal management as well. Ultra thin chips (i.e. silicon dies thinned down to 50 m total thickness) lend themselves to reach these goals. Chips with that thickness can be embedded in the dielectric layers of modern laminate PCB's. Micro via technology allows to connect the embedded chip to the outer faces of the system circuitry. As an ultimate goal for microsystem integration, the embedding of optical and fluidical system components can be envisioned. This paper presents the first approach to embed thin silicon dies in to polymeric system carriers. The aspects of embedding and making the electrical contact as well as the thermal management are highlighted. To reach the goal of a vertically stackable box-of-bricks type of ultra thin (UT) package, thin silicon chips are embedded and interconnected on a peripheral UT BGA.The authors would like to thank the team of the 3D-CSP and the ChiP task force at IZM Berlin/Munich and TU Berlin as well as the colleagues from the PCB industry having supported this feasibility study with activity and discussion. Part of the work shown here is done in of the BMBF Project Systemintegration in polymere Schaltungsträger, No.02PP2051, co-ordinated by the FZK-PFT. The support is gratefully acknowledged.This paper was presented at the Conference of Micro System Technologies 2001 in March 2001     

Worst case analysis of a greedy algorithm for graph thickness

In this paper, we consider a greedy algorithm for thickness of graphs. The greedy algorithm we consider here takes a maximum planar subgraph away from the current graph in each iteration and repeats this process until the current graph has no edge. The greedy algorithm outputs the number of iterations which is an upper bound of thickness for an input graph G=(V,E). We show that the performance ratio of the greedy algorithm is .     

Parallel Unstructured Dynamic Grid Direct Monte Carlo Simulation of Molecular Gas Dynamics and Its Applications

A new parallel dynamic unstructured grid DSMC method is presented in this paper. The code developed has been applied to the simulation of thin film deposition over microstructures. Surface deformation in such cases poses a challenge for accurate evaluation of gas flow due to the fact that the deposited film thickness is comparable to the feature size. In this study a method is developed to move the mesh at run time. Since in parallel simulation each partition moves independently of the others, a parallel version of moving mesh is proposed to synchronize the displacement of the neighboring partitions, so that there is a smooth transition from one partition to another. An efficient tool for tracking particles during simulation is also presented. Furthermore, the influence of parameters, such as sticking coefficient and aspect ratio on step coverage for a 1m wide trench by sputter deposition was studied. The results showed that the step coverage deteriorated with increasing sticking coefficient and aspect ratio.     

Micromechanical elements for detection of molecules and molecular design

Photolithographic preparation of thin films and stacks of them were combined with anisotropic silicon etching and free standing film technology in order to realize three dimensional micro components for studies in detection and optimization of biomolecules. A polymer based SFM sensor was developed and tested in the measurement of thin film roughness and in the detection of holes in molecular films as well as in the detection of single DNA molecules. This novolever shows surprisingly high mechanical stability and provides high resolution SFM images of sensible molecules. Experimental arrangements of miniaturized chemical parallel processing for combinatorial and evolutionary synthesis strategies including silicon micro compartment arrays with free standing optical membranes and thin film filters have been proposed and the manufacturing of micro compartment arrays is described.We thank M. Sossna, B. Rau, H. Porwol, I. Menzel, F. Jahn and W. Schubert for technical assistance. The Inst. of Semiconductor Physics Frankfurt/O is acknowledged for CVD-deposition of membrane films. The work on SFM-sensors was supported by the Max-Planck-Gesellschaft. The work on micro compartment arrays was supported by the BMBF (No 0310713)     

Recognizable trace languages,distributed automata and the distribution problem

We introduce new finite state parallel machines, the (-)distributed automata, for trace languages. We prove that these machines give a new characterization of recognizable trace languages: a trace language is recognizable if and only if it is recognized by a (-)distributed automaton. At last, we show how the classical problem of distribution of uninterpreted tasks on several processors can be straightforward modelized by recognizable trace languages and solved using (-)distributed.This work has been partly supported by the ESPRIT Basic Research Actions N^o 3148 (DEMON) and by the PRC C³ and Math-Info     

Submicron coatings for micro-tribological applications

The miniaturisation of mechanical components and machines enables innovative future products. However, for the improvement of functionality, reliability and lifetime of those micro systems, micro tribological coatings with thicknesses in the sub-micron range are needed. To cover these needs, we investigated different submicron coatings with the aim to develop wear and friction optimized thin films for this application. The basis of this work has been the state of the art know how of well established macroscopic coatings which in general are in a thickness range of a few micrometers. It turned out, that particularly the surface topography and the substrate material influence the properties of very thin films. For investigations with single asperity contact, the coefficient of friction (COF) was reduced by lowering the tip radius and the hardness of the substrate material. In contrast, for larger contact radii (pin-on-disc), an increase of the COF with decreasing substrate Youngs modulus was found. With respect to wear, it turned out that the wear depth increased dramatically with increasing initial surface roughness (R_a).The authors gratefully acknowledge the financial support of the German Research Foundation by grant SFB 516. We also thank T. Staedler and A. Wortmann for their contributions through their respective PhD Theses on this topic.     

Piezoelectric thin films formed by MOD on cantilever beams for micro sensors and actuators

Novel piezoelectric cantilever beams for micro sensors and actuators based on PZT thin films have been batch fabricated by surface micromachining. Lead zirconate titanate (PZT) thin film is formed by metalorganic deposition (MOD) on Pt/Ti/SiO₂/Si (1 0 0) substrates and Pt/Ti/LTO/Si₃N₄ cantilever beams and then annealed at 700 °C in air. The PZT thin film is 0.5 m thick and has dielectric permittivity of 1698, remanent polarization of 13.66 C/cm², and coercive field of 44.5 kV/cm. The influence of deposition temperatures on PZT thin film stress has been investigated. When continuously controlling the deposition temperatures, the stress of the thin film is reduced from 0.313 × 10⁸ to 0.269 × 10⁸ N/m, that is 16.4% decrease. With the total 120 designed devices on 4-inch wafers, the number of functional devices is increased from 82 to 97, that is 12.47%.Tianhong Cui joined the faculty of Institute for Micromanufacturing at Louisisana Tech University in 1999. He received his B.S. from Nanjing University of Aeronautics & Astronautics in 1991, and his Ph.D. from Chinese Academy of Sciences in 1995. He has conducted research and development work for the realization of microsensors and microactuators since 1992. Prior to joining the IfM in 1999, he was at the National Laboratory of Metrology in Japan as a Research Fellow under STA fellowship, and previous to that, served as a Postdoctoral Research Associate at the University of Minnesota. His current research interests include MEMS, polymer micro/nanoelectronics, and nanotechnology.     

Viscous Taylor droplets in axisymmetric and planar tubes: from Bretherton’s theory to empirical models

The aim of this study is to derive accurate models for quantities characterizing the dynamics of droplets of non-vanishing viscosity in capillaries. In particular, we propose models for the uniform-film thickness separating the droplet from the tube walls, for the droplet front and rear curvatures and pressure jumps, and for the droplet velocity in a range of capillary numbers, Ca, from \(10^{-4}\) to 1 and inner-to-outer viscosity ratios, \(\lambda\), from 0, i.e. a bubble, to high-viscosity droplets. Theoretical asymptotic results obtained in the limit of small capillary number are combined with accurate numerical simulations at larger Ca. With these models at hand, we can compute the pressure drop induced by the droplet. The film thickness at low capillary numbers (\(Ca<10^{-3}\)) agrees well with Bretherton’s scaling for bubbles as long as \(\lambda <1\). For larger viscosity ratios, the film thickness increases monotonically, before saturating for \(\lambda>10^3\) to a value \(2^{2/3}\) times larger than the film thickness of a bubble. At larger capillary numbers, the film thickness follows the rational function proposed by Aussillous and Quéré (Phys Fluids 12(10):2367–2371, 2000) for bubbles, with a fitting coefficient which is viscosity-ratio dependent. This coefficient modifies the value to which the film thickness saturates at large capillary numbers. The velocity of the droplet is found to be strongly dependent on the capillary number and viscosity ratio. We also show that the normal viscous stresses at the front and rear caps of the droplets cannot be neglected when calculating the pressure drop for \(Ca>10^{-3}\).     

Logical and algorithmic properties of independence and their application to Bayesian networks

This paper establishes a partial axiomatic characterization of the predicateI(X, Z, Y), to read X is conditionally independent ofY, givenZ. The main aim of such a characterization is to facilitate a solution of theimplication problem namely, deciding whether an arbitrary independence statementI(X, Z, Y) logically follows from a given set of such statements. In this paper, we provide acomplete axiomatization and efficient algorithms for deciding implications in the case where is limited to one of four types of independencies:marginal independencies,fixed context independencies, arecursive set of independencies or afunctional set of independencies. The recursive and functional sets of independencies are the basic building blocks used in the construction ofBayesian networks. For these models, we show that the implication algorithm can be used to efficiently identify which propositions are relevant to a task at hand at any given state of knowledge. We also show that conditional independence is anArmstrong relation [10], i.e., checkingconsistency of a mixed set of independencies and dependencies can be reduced to a sequence of implication problems. This property also implies a strong correspondence between conditional independence and graphical representations: for every undirected graphG there exists a probability distributionP that exhibits all the dependencies and independencies embodied inG.This work was partially supported by the National Science Foundation Grant #IRI-8610155. Graphoids: A Computer Representation for Dependencies and Relevance in Automated Reasoning.     

A Network Game with Attackers and a Defender

Consider an information network with threats called attackers; each attacker uses a probability distribution to choose a node of the network to damage. Opponent to the attackers is a protector entity called defender; the defender scans and cleans from attacks some part of the network (in particular, a link), which it chooses independently using its own probability distribution. Each attacker wishes to maximize the probability of escaping its cleaning by the defender; towards a conflicting objective, the defender aims at maximizing the expected number of attackers it catches. We model this network security scenario as a non-cooperative strategic game on graphs. We are interested in its associated Nash equilibria, where no network entity can unilaterally increase its local objective. We obtain the following results: