Daniel Lapadatu

Electrostatic forces and their effects on capacitive mechanical sensors

Abstract This paper describes the electrostatic forces developed between the plates of capacitive mechanical sensors built in crystalline silicon and their effects on the measurement and the fabrication process. In single capaciti sensors the electrical forces can introduce offset errors in the measuring process, or can cause the collapse of the sensing structure or jeopardize the functionality of the final device due to the sticking or even bonding of the movable parts. Also it is investigated how the limits are affected when scaling down the dimensions of the sensors. Finally, some solutions to avoid the negative effects of the electrostatic forces are proposed.

Extremely miniaturized capacitive movement sensors using new suspension systems

Abstract An extremely miniaturized implantable capacitive accelerometer using novel suspension systems is presented. The main objectives are low power consumption, high sensitivity and very small size (13 mm×1.2 mm× 1.3 mm). Low power consumption can be achieved by selecting the capacitive sensing principle. In order to achieve the extreme miniaturization and also to improve the sensitivity, new suspension systems are investigated: torsional, meander- and spring-shaped beams. A very high sensitivity (5 μ/ g ) can be reached using the latter. The capacitance at rest is typically 4 pF and aΔC of 200% can be obtained. This new device combines the miniaturization demands with the simplicity of the technological process. The general design concept, electrical considerations and the most important fabrication steps are presented. With respect to the measuring system, the influence of d.c. and a.c. voltage supply is investigated in order to control the effective electrostatic forces.

A low power multi-sensor interface for injectable microprocessor-based animal monitoring system

Abstract In the research field of several biomedical disciplines a major need exists for reliable and implantable telemetry sensor systems. Apart from the demands for small size, light weight and long operational lifetime, the sensor systems should preferably also be flexible, versatile and intelligent. As a follow-up of previous work, a novel and more powerful transponder is developed, specifically tailored for applications in large-scale animal husbandry. It is a read—write telemetry device based on a microprocessor configuration, containing a dedicated sensor interface chip (SIC), SMD thermistor and subminiature capacitive accelerometers.

Corrugated silicon nitride membranes as suspensions in micromachined silicon accelerometers

This paper presents some theoretical considerations and experimental results carried out to investigate the potential use of corrugated silicon nitride membranes as a mechanical suspension in micromachined silicon capacitive accelerometers.

A model for the etch-stop location on reverse-biased pn junctions

Abstract This paper reports a model to predict where the silicon anisotropic electrochemical etching terminates on reverse-biased pn junctions. The model explains why the etching process terminates well before the metallurgical junction. The effects of the substrate doping, the type of junction (step or graded), the etching temperature and voltage bias, as well as the technique used (three and four electrodes) are analysed and compared with the experimental data. Some limitations and deviations from this theory are also pointed out.

On the anodic passivation of silicon in aqueous KOH solutions

Abstract This paper proposes a new explanation to account for the anodic passivation of single-crystalline silicon in aqueous KOH. The effects of experimental results.

A double-sided capacitive miniaturized accelerometer based on photovoltaic etch-stop technique

Abstract A double-sided capacitive miniaturized accelerometer is presented. The photovoltaic etch-stop technique (PHET) is used to simplify the device fabrication. PHET being a relatively new technique, the paper emphasizes the design rules required in order to have an etch stop. The device is a uniaxial accelerometer with practically no cross-sensitivity, which can sense accelerations in the range -5g to 5g. The parasitic capacitances and the effects of the electric forces driving the device are cancelled out by its symmetry. The final device measures 2.2 mm × 2.0 mm × 1.5 mm.

A Double Sided Capacitive Miniaturised Accelerometer Based On Photovoltaic Etch Stop Technique

A double sided capacitive miniaturised accelerometer is presented. The photovoltaic etch stop technique, PHET [ 11, is used to simplify the device fabrication. P E T being a relatively new technique, the paper emphasises on the design rules required in order to have an etch stop. The device is an uniaxial accelerometer with practically no cross sensitivity, which can sense accelerations in the range of -5 to 5 g. The parasitic capacitances and the effects of the electric forces driving the device are cancelled out by its symmetry. The final device measures 2.2 . 2.0. 1.5 mm3.