D. Tsoukalas

A solid-state pressure-sensing microsystem for biomedical applications

Abstract A pressure-sensing system consisting of a miniature silicon capacitive-type sensor, made with the silicon fusion bonding technique, and a detection integrated circuit is presented. The entire system converts pressure changes, in the pressure range useful for biomedical applications, to frequency changes. The system is equipped with a reference capacitor to cancel out the temperature dependence and the ageing effects.

Ultraminiature silicon capacitive pressure-sensing elements obtained by silicon fusion bonding

Abstract We present a technology to fabricate ultraminiature capacitive-type sensing elements for use in blood-pressure measurements, each of them having a side dimension of only 130 μm. The devices, which are made in an array configuration, are fabricated using the silicon fusionbonding technique and self-aligned boron ion implantation. The process is simple, requiring only three mask levels, and has high yield. Throughout the paper we compare the fabrication process as well as the measurement results of the array configuration with single membranes having the same measurement range. Measurement results are presented for both static and dynamic pressure conditions.

Parameters influencing the flatness and stability of capacitive pressure sensors fabricated with wafer bonding

Abstract In this work we present detailed optical and electrical characterization results on silicon capacitive pressure sensing elements. The device fabrication technology is based on the wafer bonding technique. Using the micro-Raman technique, we investigate the influence of specific process steps as well as of the wafer bonding conditions—performed either in air or in nitrogen ambient—on the flatness and stress distribution of the pressure sensing diaphragms. Emphasis is also given on drift as well as on fatigue measurements since these effects determine the reliability of the devices.

Picosecond and nanosecond laser annealing and simulation of amorphous silicon thin films for solar cell applications

In this work, a picosecond diode pumped solid state laser and a nanosecond Nd:YAG laser have been used for the annealing and the partial nano-crystallization of an amorphous silicon layer. These experiments were conducted as an alternative/complementary to plasma-enhanced chemical vapor deposition method for fabrication of micromorph tandem solar cell. The laser experimental work was combined with simulations of the annealing process, in terms of temperature distribution evolution, in order to predetermine the optimum annealing conditions. The annealed material was studied, as a function of several annealing parameters (wavelength, pulse duration, fluence), as far as it concerns its structural properties, by X-ray diffraction, SEM, and micro-Raman techniques.

Structural Characterization of Layers for Advanced Non-volatile Memories

Non-volatile memory cells are the devices with the most aggressive scaling on the market. For this reason the accurate characterization of their layer stacks is of great importance. We present a review of our recent work on a large variety of such stacks, for charge-trap and resistive memories, which have been characterized structurally with Transmission Electron Microscopy and Conducting Atomic Force Microscopy ; we discuss the features of their structure on their function as memory elements.

Flexible platinum nanoparticle strain sensors

Using a modified magnetron sputtering technique, platinum nanoparticles having a mean diameter of 4-6 nm have been deposited on flexible polyimide substrates. The polyimide substrates have been previously patterned with gold interdigitated electrodes having an inter-finger distance of 10 μm using conventional photo lithography and the e-gun evaporation of gold. By controlling the nanoparticle deposition time, platinum nanoparticle sensors of varying sensitivity can be produced. As a result a flexible cost effective alternative to silicon strain sensors is hereby presented.

Conceptual Design of a Wireless Strain Monitoring System for Space Applications

The conceptual design of the architecture of a wireless strain monitoring network suitable for space applications is presented. The system is a heterogeneous wireless network that consists of battery powered nodes and batteryless nodes that are able to harvest energy from an incident RF field. Battery powered nodes are based on the Zigbee standard. Both battery and batteryless nodes are envisioned to include sensors but some battery powered nodes could simply serve as relaying points to transfer data to the central computer. The structure of the batteryless nodes as well as remote powering and data transmission are analyzed.