Markus Emmenegger

An error indicator and automatic adaptive meshing for electrostatic boundary element simulations

Accurate electrostatic simulations are required for the analysis of micro electromechanical systems (MEMS) and interconnects in very large scale integration (VLSI) design. Typical simulations involve complex three-dimensional (3-D) geometries together with various dielectric materials, conductors, and boundary conditions. The boundary element method is well suited for such computations. For highly accurate solutions, the meshing of the geometry becomes increasingly important. A scheme is presented which allows generating an optimal mesh automatically based on a coarse initial discretization, e.g., a CAD model. An error indicator derived from boundary integral equations monitors the solution accuracy in each boundary element. H-type or p-type mesh refinement is applied to areas which contribute strongly to the overall error. The method applies to both two-dimensional (2-D) and 3-D simulations containing elements of various orders and shapes. The generated refined meshes result in significantly higher solution accuracy for a given simulation size.

Equivalent circuit model of resistive IC sensors derived with the box integration method

We present an automatic method to produce compact equivalent circuit models of spatially inhomogeneous resistors. Local variations in space of the resistivity due to physical interactions such as magnetic fields or mechanical stress are automatically included. The equivalent circuit model is computed using symbolic algebra, such that the functional relation between the resistivity and the fields interacting with it is included in the circuit design model. Modeling is based on the discretization of the sensor geometry with a mesh of elements and vertex nodes together with the current continuity equation using the box integration method. The resistivity is described by the tensor field of electrical conductivity and depends on the physical interactions to be modeled. The element internode conductivity is mapped to a set of lumped conductances and transconductances (voltage controlled current sources) between the nodes of the discretization mesh. These conductances and transconductances are translated into an equivalent circuit net list. Optionally, the electrical network representing the sensor is simplified before translation by symbolic linear algebra. Thus, equivalent circuit models consisting of many simple elements can be generated as well as models with only a few, algebraically complicated elements. The method is demonstrated using the public domain circuit simulator SPICE3 for the example of a magnetic Hall sensor, with and without the piezoresistive effect.

Solenoidal micro coils manufactured with a wire bonder

We present for the first time the development of 3-D solenoidal micro coils using an automatic wire bonder. By developing a stable and repeatable bond process with insulated wire, micro coils with sub-millimeter diameter have been manufactured. The winding process for a single coil takes about 200 ms, whereas the manufacture of a 100-coil-array takes less than a minute. Micro coils with 4 windings and a diameter of 690 mum exhibit an inductance of 12.7 nH and a resistance of 580 muOmega at 300 MHz. These values correspond to a quality factor of 41 and compare favorably lo state-of-the-art micro coil manufacturing technologies.

Simulation of a thermomechanically actuated gas sensor

The physical dimensions of microsystems make the characteristic times of thermal and mechanical phenomena comparable. Thus, for the first time, we require the coupled analysis of this system. This paper tackles this challenge, presenting a general method to routinely investigate the frequency-domain behaviour of MEMS devices thermo-mechanically excited by an AC heating power. In particular, an application to a gas sensor is presented. For the device we can now correctly determine the amplitude/heating power ratio, given the air and structural damping model, together with the geometry and material description, Characteristics of the method are the use of finite elements for the space-discretization, and spectral analysis for the reduction of mechanical degrees of freedom.

An object-oriented design for efficient microsystem simulation

This thesis presents a Solution to the Simulation requirements of an engineer designingelectro-thermo-mechanicalmicrosystems.To efficiently design micro¬ systems, we require to understandthe inner workings of these Systems, know how energy is transferredinsidethe devices, and how the Output signalscome about. A wide ränge of physical effects is exploited in microsystems. At the very mimmurn, electrical, thermal and mechanical effects, as well as the coupling between these domains, has to be taken into account. Additionally, views on the system are used to model the behavior: The stationary viewfocuses on the equilibrium state after a long time, whereas the transientview looks at the short-time behaviorafter a sudden changein the State of the system. Harmonie and eigen value approaches add insight into how the models behave in the time domain. All these modelsare efficiently explored using a Simulation tool. We present the FEMEngine,a multi-physics finite dementSimulator. It allows a designer to gain insight into the physical effects occurring in the devices being developed. In the developmentof the FEMEngine,we have striven to achieve a consistent architectureto allow the flexible extension of the Simulator. To this end, an objeetoriented design method and programming language have been used. The thesis also presents the architecture we have created. and how this architecture allows extensionto additional physical effects and Solution methods. At the end of the thesis, the power of the FEMEngine is illustrated by simulations of a selected set of microsystems.

A new computational method for piezoelectric plate modeling: application to membrane microsensors

Among applications of the piezoelectric effect in micro-electro-mechanical systems (MEMS), several employ membranes as the active region of the device. We have developed a new multilayered piezoelectric composite plate finite element that improves the modeling of piezoelectric membranes. In this paper we present the implementation of the element within the finite element package FEMEngine. We demonstrate the validity of the theory and use the implementation to simulate a viscosity sensor for food-stuff monitoring. Our work is motivated by the fact that the accurate modeling of piezoelectric multilayered membranes is not possible with currently available commercial finite element software.

Smart enumeration in C++: virtual construction, message dispatching and tables

This paper describes a C++ idiom for replacing types. This idiom allows effective and elegant implementations of patterns such as virtual object construction, message dispatching and tables. It also improves compile‐time checks and simultaneously allows rows to be added dynamically to tables.SmartEnums have been developed within a project of numerical software for microsystem simulation. Copyright