Fabrication of surface-micromachined structures by a post-processing module above standard IC circuits is an efficient way to produce monolithic microsystems, allowing nearly independent optimization of the circuitry and the MEMS process. However, until now the high-temperature steps needed for deposition of poly-Si have limited its application. SiGeM explores the possibilities offered by the low-temperature (450 degrees C) deposition and structuring of poly-SiGe layers, which is compatible with the temperature budget of fully-processed standard IC wafers. In the SiGeM project several low-temperature deposition methods (CVD, PECVD, LPCVD) were developed, and were evaluated with respect to growth rate and material quality. The interconnection technology to the underlying CMOS circuitry was also developed. The capabilities of this new integration technology will be demonstrated in a monolithic high-performance rate-of-turn sensor, currently considered the most demanding MEMs application in terms of material properties of the structural layer (thickness > 10 mu m, stress gradient < 03MPa/mu m) and signal processing circuitry (capacitance resolution in the aF range, SNR > 110 dB). System partitioning will combine analog and DSP circuit techniques to maximize resolution and stability. Parasitic electrical coupling within different parts of the system has been analyzed, and countermeasures to reduce it have been incorporated in the design. The feasibility of the approach has already been proved by preliminary characterization of working prototypes containing released microstructures deposited on top of preamplifier circuits built on a 0.35 mu m, 5-metal, 2-poly, standard CMOS process from Philips Semiconductors. Resonance frequencies are in good agreement with predictions, and quality factors above 8000 have been obtained at pressures of 0.8 mTorr. Measured SNR confirms the capability to achieve a resolution of 0.015 degrees/s over a bandwidth of 50 Hz.

This chapter contains sections titled: Basic Considerations and Definitions Classification of Sensor-Input Signals Signal Conversion and Signal Extraction (Signal Path) Sensor Output Signals Summary and Outlook References

With the recent progress in microsystems technology there is a growing need for accurate knowledge of material properties in design. Especially on thin films, material properties are strongly affected by layer thickness and deposition parameters. Since traditional methods for the characterization of bulk materials are hardly applicable on thin films novel extraction techniques are required. The following paper deals with a resonant method to determine Young's modulus and residual stress simultaneously. Therefore an array of microbridges with variable length is etched into the layer material. Samples are stimulated electrostatically to small signal oscillations and their resonance frequency is measured by a laser doppler interferometer. Based on the theory of prestressed beams both material parameters can be separated independently by nonlinear function fitting. Accuracy of this approach will be assessed and first results are presented.

On the example of bulk-micromachined electrostatically driven micromirror arrays, the influence of partially absorbed laser power on the surface deformation by the caused temperature rise is discussed in this contribution. A maximum power rating can he estimated regarding the measurement results.

A new application of synchronously working micromachined silicon mirrors for a laser beam projection technique producing images on the whole circumference of a cylindrical shaped screen will be discussed within this contribution. The mechanically active mirror area of 12 square millimeters has been divided into 49 single mirrors in order to achieve both fast steering and light power distribution. Diffraction of the laser beam due to the regularly arranged mirrors and its influence to the contrast has been experimentally determined on a small sized projection system. Analytically calculated thermal effects on the mirror shape caused by light power dissipation and heat transfer correspond to the measurements by thermographic imaging and topographic metrology. Investigations concerning phase lag and amplitude difference between the mirrors lead to a design of specially shaped hinges with reduced sensitivity to the main fabrication tolerances.

Heat transfer mechanisms in electrostatically actuated torsion mirrors are dominated by heat conduction in the torsion springs and the air gap between mirror plate and driving electrodes and by convection above the mirror. The maximum optical power rate capability of micromirrors strongly depends on the reflectivity of the mirror surface and of the heat transfer out of the mirror plate. The results provide important knowledge since increased mirror temperature influences its optical parameters like flatness and roughness, the dynamical system behavior or even damages the reflective layer. This paper deals with investigations of the heat transfer by conduction and convection. The cumulative heat resistance of micromirrors is calculated using analytical formulas and by means of finite element modelling. Theoretical results are compared with experimental data. A thermographic imaging system and electrical heating is used to measure the thermal decay function which evaluates the resistance at known capacitance. It can be deduced that an optical power of several Watt can be steered by micromirrors.

Within this paper novel applications of low temperature silicon wafer bonding technologies for the fabrication of high frequency silicon microscanners are presented. Two technological approaches are discussed, both using low temperature bonding as a key technological step. Results of the integration of a special low temperature bonding process within the bulk technology approach are shown. Micromirror arrays fabricated with this technology are presented and show promising results for optical applications.

This paper deals with micromirror arrays for high frequency applications. The use of monocrystalline silicon as mechanical material results in a low hysteresis, good reproducibility and high reliability. General characteristics, advantages and limitations of large analogously working mirror arrays in comparison with single elements will be discussed with respect to the requirements of desired applications. Special aspects of the design of micromirror arrays, experimental results concerning the behavior of the electromechanical system and optical properties will be presented as well. It will be shown that cascaded elements allow beside higher quality factors or resonant band width concerning the dynamic behavior also higher quasistatic deflection angles at diminished electrode gaps and lower driving voltages.

This paper deals with design, technology and experimental investigations of mirrors and micromirror arrays made of monocrystalline silicon. Electrostatically operated twin-directional deflecting mirrors and mirror arrays convenient for continuous scanning with working frequencies between several 100 Hz up to 20 kHz will be presented. An experimental data based method to improve the accuracy of model parameters for simulations and to determine the cross coupling between array cells is new in the field of micromechanics and will be shown

Methods to calculate the fluid depending forces in movable micromechanical structures will be shown in this paper. In most cases fluid flow within narrow air gaps can be simply described by the Reynolds gas film equation. Analytical solutions are known for simple plate shapes. New ways to describe the damping and squeeze film effect for nontrivial plate shapes using analogy relations are discussed. Reynolds equation fails in the case of large air gaps between plates or if free outstream conditions are not valid. In these cases the general Navier-Stokes-Equation must be used. FE-tools with fluidmechanical capabilities are able to solve this partial differential equation and allow a damping analysis. Phase shift between plates velocity and reaction forces can be interpreted as additional inertial or squeeze forces. Results of simulation and experimental analysis are verified on a gyroscope and a micromirror array

Recently scanning actuator arrays have been developed using metal, e.g. aluminium, or polysilicon as mirror material. Design and technology of micro mirror arrays made of monocrystalline silicon an discussed in this paper as well as experimental results characterising the arrays. Micro mirror arrays with up to 1000 simultaneously movable electrostatically operated cells convenient for continuous scanning with frequencies of several hundred Hz up to some kHz will be presented. The technological approaches consist of the use of silicon wet- and dry-etching, wafer bonding (silicon fusion and anodic bonding) and metallization. A novel modified BESOI technology with CMP, wafer bonding with buried refractory metal electrodes and sacrificial layer etching has been developed and will be discussed. The design process is based on simple analytical calculations of the mechanical behaviour, the fluid flow surrounding the movable mirror and the electrostatic field as well as numerical simulations by means of the finite element method and network analysis. Furthermore, some experimental methods to characterise the electro-mechanical behaviour of micro mirror arrays are discussed. In order to evaluate theoretic models describing the behaviour, the natural frequencies, the damping coefficients and the frequency transfer function are measured. The adaptation of the model parameters leads to more accurate values simulating the behaviour.