Biosensors for analytical microsystems

A modular concept for analytical microsystems with separately developed and optimized components is proposed, where parts can be easily substituted. Since the system should be universal hybrid integration is preferred over monolithic fabrication technology.The biosensor as an essential part of an analytical microsystem is commonly restricted in its functional stability due to the lifetime of the biological component and the adhesion of the sensitive layer at the transducer. Optimum design requirements have to be derived from the particular system to be measured. For the optimization of the (bio)sensor the polymer matrix carrying or covering the enzyme has been modified, the transducer design itself has been varied, and enzymes have been coupled.     

Tactile metrology for active microsystems

Often active microsystems consist of hybrid structures. Usually tactile metrology is here the only possibility to check manufacturing tolerances in the sub-micrometer range and to guarantee a lasting quality assurance of the production. For characterizing microprobes with reference objects and for tactile measurements of micro-components a high precision 3d-positioning system was developed. The improvement of the probing system, which affects the measuring accuracy decisively, was the main topic of the research. First results of probing experiments are shown.     

Polycrystalline silicon-germanium films for integrated microsystems

Two approaches were demonstrated for fabricating microstructures after completion of CMOS circuits with aluminum metallization. The first approach employed n-type poly-Ge deposited at 400/spl deg/C as a structural material with an SiO/sub 2/ sacrificial layer and an HF release. The CMOS circuits were protected from the release etchant with an amorphous Si layer. Clamped-clamped lateral resonator test structures had quality factors in vacuum as high as /spl sim/30000. Following a 500/spl deg/C, 30 s RTA the poly-Ge stress was 200 MPa (tensile) and the resistivity was 5.3 m/spl Omega/-cm. In the second integration approach, p-type poly-Si/sub 0.35/Ge/sub 0.65/ deposited at 450/spl deg/C was the structural material with poly-Ge as the sacrificial material and H/sub 2/O/sub 2/ as the release etchant. The H/sub 2/O/sub 2/ did not significantly etch the p-type poly-SiGe structural layer and no protection of the underlying CMOS layers was needed. For the first time, the fabrication of LPCVD surface microstructures directly on top of standard electronics was demonstrated, providing dramatic reductions in both MEMS-CMOS interconnect parasitics and device area. A folded flexure lateral resonator had a quality factor in vacuum as high as /spl sim/15000. No stress or dopant-activation anneal was needed, since the in situ boron-doped poly-SiGe was found to have an as-deposited stress of only -10 MPa (compressive) and a resistivity of only 1.8 m/spl Omega/-cm.     

Tribology of microsystems

In this work the possibilities for the reduction of friction and wear in micro electro-mechanical systems (MEMS) are investigated. An improvement of the tribological behaviour of microsystems can be realized by optimizing the contact condition and by application of special coatings with low friction and low wear rates. For optimizing the contact condition a defined topography and surface profile is generated by photolithography. Furthermore tribological coatings with low friction and low wear rates are developed and investigated using nanoindentation and micro scratch experiments. Also novel results on micro structured surfaces coated with a-C:H and a-C films will be discussed. The results show the great potential of carbon-based coatings in combination with an optimized geometrical surface design.     

Germanium resistors for RF MEMS based microsystems

This paper introduces the use of germanium as resistive material in RF MicroElectroMechanical (MEMS) devices. Integrated resistors are indeed highly required into RF MEMS components, in order to prevent any RF signal leakage in the bias lines and also to be compatible with ICs. Germanium material presents strong advantages compared to others. It is widely used in microtechnologies, notably as an important semi-conductor in SiGe transistors as well as sacrificial or structural layers and also mask layer in various processes (Si micromachining especially). But it also presents a very high resistivity value. This property is particularly interesting in the elaboration of integrated resistors for RF components, as it assures miniaturized resistors in total agreement with electromagnetic requirements. Its compatibility as resistive material in MEMS has been carried out. Its integration in an entire MEMS process has been fruitfully achieved and led to the successful demonstration and validation of integrated Ge resistors into serial RF MEMS variable capacitors or switches, without any RF perturbations.     

CAD tools for bridging microsystems and foundries

To move microsystems from research prototypes to an industrial market, CMP, the French multiproject wafer service, has adapted an existing commercial tool to the automated design of micromachined devices     

Integrating testability into microsystems

 The integration of sensors and actuators with microelectronics into either compact packages or onto a single silicon die is likely to be of major technological importance over the next decade. These systems are referred to as Microsystems or Micro-Electro-Mechanical-Systems (MEMS). One obstacle to mass-market introduction are difficulties with quality and reliability verification. This paper outlines the difficulties of testing microsystems, shows approaches of test generation and verification transferable from the mixed-signal Integrated-Circuit (IC) domain, and demonstrates an on-line test designed for bridge-type, micromachined accelerometer and pressure sensors [1]. Received: 31 October 1996 / Accepted: 14 November 1996     

Dynamic characteristics of micro air bearings for microsystems

This paper reports on the dynamic characteristics of micro air bearings that include thrust and journal air bearings for microsystems. The dynamic thrust air bearing employs a spiral groove configuration. Analysis shows that the motion stability and load capacity of a thrust air bearing imposes a contradictive requirement on the groove pattern of the air bearing. The dynamic journal air bearing is realized by using a plain circular trench with a narrow radial clearance of C, and a very small aspect ratio of bearing length versus diameter (L/D). Analysis on the shock tolerance of the journal air bearing shows that the shock tolerance increases with the bearing number, the bearing aspect ratio of L/D and its initial equilibrium eccentricity ratio ε ₀. The optimum values of the bearing parameters are explored and recommended. A prototype of turbine device has been designed based on the recommended bearing configurations and realized via microfabrication.     

Multilayer polyimide film substrates for interconnections in microsystems

 Currently there is a great interest in flexible substrates for their use in the packaging of semiconductors. They allow high packaging density and permit mechanical motion of the components, if necessary. This paper describes a new substrate material which possesses a high flexibility and which can be used for the realization of interconnection cables and MCM-D. These substrates are not only highly flexible but also mechanically stable, chemically inert and can be produced with the same processes as those for rigid substrates. Received: 14 December 1998 / Accepted: 28 December 1998     

Modular software system for computer aided design of microsystems

A modular software system to assist engineers in designing microsystems is presented. The different modules support both the system and the component design and are linked with each other by a workflow management system. In particular, this paper presents the co-operation of the modules rumtopf, suzana and μ-toast. They assist the designer in the definition and validation of process sequences, the simulation of wet chemical etching of silicon and the tolerance management. The usage and usefulness of the presented software system is illustrated by an example showing the design of an acceleration sensor.     

Fluidic heterogeneous microsystems assembly and packaging

The nonrobotic fabrication of packaged microsystems that contain nonidentical parts has been accomplished by a directed self-assembly process. The self-assembly process uses geometrical shape recognition to identify different components and subsequent bond formation between liquid solder and metal-coated areas to form mechanical and electrical connections. We applied this concept of shape recognition and subsequent formation of contacts to assemble and package microsystems that contained nonidentical subunits. The self-assembly of three-component assemblies is demonstrated by sequentially adding device segments to the assembly solution including 200-/spl mu/m-sized light-emitting diodes. Six hundred AlGaInP-GaAs light-emitting diode segments self-assembled onto device carriers in 2min without defects. Encapsulation units self-assembled onto the LED-carrier assemblies to form a three-dimensional (3-D) circuit path to operate the final device. The reported procedure provides a new route to the creation of autonomous heterogeneous microsystems including the realization of autonomous wireless sensor system that requires nonidentical units: CMOS circuitry, Non-CMOS sensor unit for sensing, III-V components for communication, and encapsulation units to form 3-D electrical interconnects. The creation of such systems is being discussed and a proof of concept experiment is being demonstrated.     

Micro-ECM for production of microsystems with a high aspect ratio

The most used processes for production of microsytem components are basically from the semiconductor technology. The material properties of used silicon often dont achieve the demands of for example: micro-surgery, biotechnology life science, fluidics or high temperature environment. For microstructuring of highly stressed metals, like stainless and heat resisting steels, cold work tool steels, hot work tool steels and nickel-base-alloys and a variety of metals there is no manufacturing-process. An interesting possibility for structuring this type of materials are the electrochemical machining processes (ECM). Some new developed ECM-sinking-processes are working with oscillating tool-electrode, to improve shape accuracy.     

Lifetime modelling for microsystems integration: from nano to systems

Due to the rapid development of IC technology the traditional packaging concepts are making a transition into more complex system integration techniques in order to enable the constantly increasing demand for more functionality, performance, miniaturisation and lower cost. These new packaging concepts (as e.g. system in package, 3D integration, MEMS-devices) will have to combine smaller structures and layers made of new materials with even higher reliability. As these structures will more and more display nano-features, a coupled experimental and simulative approach has to account for this development to assure design for reliability in the future. A necessary “nano-reliability” approach as a scientific discipline has to encompass research on the properties and failure behaviour of materials and material interfaces under explicit consideration of their micro- and nano-structure and the effects hereby induced. It uses micro- and nano-analytical methods in simulation and experiment to consistently describe failure mechanisms over these length scales for more accurate and physically motivated lifetime prediction models. This paper deals with the thermo-mechanical reliability of microelectronic components and systems and methods to analyse and predict it. Various methods are presented to enable lifetime prediction on system, component and material level, the latter promoting the field of nano-reliability for future packaging challenges in advanced electronics system integration.