Microfabrication processes for chemical and biochemical sensors are reviewed. Standard processing steps originating from semiconductor technology are detailed, and specific micromachining steps to fabricate three-dimensional mechanical structures are described. Fundamental chemical sensor principles are briefly abstracted and corresponding state-of-the-art examples of microfabricated chemical sensors and biosensors are given. The advantages and disadvantages of either fabricating devices in IC fabrication technology with additional microfabrication steps, or of using custom-designed nonstandard microfabrication process flows are debated. Finally, monolithic integrated chemical and biological microsensor systems are presented, which include transducer structures and operation circuitry on a single chip.

The first micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. This device is composed of an 8/spl times/8 array of cells each having four orthogonally oriented actuators in on overall die-size of 9.4 mm/spl times/9.4 mm. The polyimide based actuators were fabricated directly above the selection and drive circuitry. Selection and activation of actuators in this array shows that integration was successful. The integration of CMOS electronics and MEMS micromechanisms allows the implementation of new task-level micromanipulation strategies. New low-level control algorithms (actuator gaits) were also demonstrated. The array was programmed to perform several kinds of manipulation tasks, including linear translation, diagonal motion, as well as vector field operations such as squeeze field and radial field orienting and centering. Preliminary experiments were also performed using thin silicon dice of about 3 mm/spl times/3 mm/spl times/0.5 mm size as the object being moved.

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 © 1999 John Wiley & Sons, Ltd.

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.

An integrated circuit (IC) approach to thermal microsensors is presented. The focus is on thermal sensors with on-chip bias and signal conditioning circuits made by industrial complementary metal-oxide-semiconductor (CMOS) IC technology in combination with post-CMOS micromachining or deposition techniques. CMOS materials and physical effects pertinent to thermal sensors are summarized together with basic structures used for microheaters, thermistors, thermocouples, thermal isolation, and heat sinks. As examples of sensors using temperature measurement, we present micromachined CMOS radiation sensors and thermal converters. Examples for sensors based on thermal actuation include thermal flow and pressure sensors, as well as thermally excited microresonators for position and chemical sensing. We also address sensors for the characterization of process-dependent thermal properties of CMOS materials, such as thermal conductivity, Seebeck coefficient, and heat capacity, whose knowledge is indispensable for thermal sensor design. Last, two complete packaged microsystems-a thermoelectric air-flow sensor and a thermoelectric infrared intrusion detector-are reported as demonstrators.

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.

The solution of Poisson's simulations in large, geometrically complex domains with various boundary conditions are of interest in many physical computations. In this paper, we focus on electrostatic analysis. This is important for microactuator (MEMS) and interconnect modeling and also in the simulation of the electrostatic properties in VLSI chips, such as CCD sensors and DRAM cells. The computation of the static electric potential and field distribution involves the solution of the Poisson's equation, or in case of charge free space, Laplace's equation. The boundary element method has proven to be well suited for the solution of these partial differential equations in both 2- and 3-D. The required computational resources can be significantly reduced with the use of multipole acceleration techniques. An enhanced multipole (MP) acceleration technique is presented, allowing for reduced computational time and memory requirements in all stages of the computational process: the assembly of the global system of equations, the solution of the system and the evaluation of the potential and flux at specified internal positions. Contrary to previous applications of MP acceleration to Poisson's equation, the method allows the treatment of a wider class of boundary conditions, including Neumann and floating. The method is applicable both in two and three dimensions using a constant or high order boundary elements.

In this paper we propose an A/D converter for smart sensor read-out systems with limited bandwidth. The system can be associated with various sensors in the case where digital output and high resolution are required. The converter is intended to be cointegrated with IC compatible microsensors. An application of the proposed A/D converter is demonstrated in combination with a two dimensional magnetic vector probe for accurate measurement of the angle of a magnetic field parallel to the chip plane. A two dimensional magnetotransistor serves as sensing element. The converter can be configured to achieve the angle calculation with good accuracy. This system is designed to be used in automotive and drive applications. We successfully implemented the proposed A/D converter in a standard 2 /spl mu/m CMOS technology together with a two dimensional magnetic vector probe.

In this paper we present a new modulator architecture for A/D conversion. This modulator allows a great simplification of the analog front end at the expense of a more complex digital signal processing for the bit stream decoding. Moreover, the system can be partitioned into two blocks communicating through noise immune signal lines. These two features, are very advantageous for sensor interfaces in remote locations and where only a minimal amount of circuitry can be co-integrated with the sensor. Extensive computer simulations demonstrate the feasibility of this approach.>

In this paper we propose new approach to operate Suppressed Sidewall Injection dual collector Magnetotransistor (SSIMT), which allows one to reduce the power consumption and to implement directly switched capacitor signal-processing functions. This is obtained using charge instead of current to drive the device. Because of the clocked operation, the static power dissipation is eliminated and a sampled signal is obtained directly from the sensor. The proposed approach has been experimentally verified and the obtained results are presented.>

Two-dimensional numerical solutions to the system of partial differential equations governing galvanomagnetic carrier transport in magnetic-field-sensitive integrated bipolar transistors are presented. The equations are discretized using the finite box procedure with a variation in the standard Scharfetter-Gummel approach adopted for the current continuity equations. High-resolution computations of the potentials in the base region of realistic device structures and operating conditions show that the magnitude of the Hall voltage at the emitter-base junction is too small to cause any appreciable asymmetric minority carrier injection thus invalidating the widely invoked emitter injection modulation model. Measured data obtained using in situ Hall probes are in support of the conclusions derived from the numerical model.>

With the increasing need for microsensors, development of simulation tools (based on adequate physical models to facilitate microsensor analysis and design) is a crucial task. The authors review the variety of physical approximations, model equations, and boundary conditions along with an outline of pertinent numerical procedures used in the numerical simulation of semiconductor microsensors. In particular, physical microsensors for thermal, optical, magnetic, and mechanical measurands are considered and selected simulation results are presented.>

A magnetic field sensor is an entrance transducer that converts a magnetic field into an electronic signal. Semiconductor magnetic field sensors exploit the galvanomagnetic effects due to the Lorentz force on charge carriers. Integrated semiconductor, notably silicon, magnetic field sensors, are manufactured using integrated circuit technologies. Integrated sensors are being increasingly developed for a variety of applications in view of the advantage offered by the integration of the magnetic field sensitive element together with support and signal processing circuitry on the same semiconductor chip. The ultimate goal is to develop a broad range of inexpensive batch-fabricated high-performance sensors interfaced with the rapidly proliferating microprocessor. This review aims at the recent progress in integrated silicon magnetic devices such as integrated Hall plates, magnetic field-effect transistors, vertical and lateral bipolar magnetotransistors, magnetodiodes, and current-domain magnetometers. The current development of integrated magnetic field sensors based on III-V semiconductors is described as well. Bulk Hall-effect devices are also reviewed and serve to define terms of performance reference. Magnetic device modeling and the incorporation of magnetic devices into an integrated circuit offering in situ amplification and compensation of offset and temperature effects are further topics of this paper. Silicon will continue to be aggressively exploited in a variety of magnetic (and other) sensor applications, complementary to its traditional role as integrated circuit material.