Pierre Gérard

Miniaturized Wireless Sensing System for Real-Time Breath Activity Recording

A portable, non-invasive and easy to operate wireless system has been developed for monitoring the breathing activity of patient. The system is composed of a capacitive microsensor (airflow-humidity sensor) integrated on a silicon chip and of a Negative Temperature Coefficient thermistor; both are connected to a wireless network to allow efficient healthcare at home as well as in hospitals. The capacitive sensitive part of the microsensor is an array of interdigitated metallic electrodes covered by 100-nm-thick dense anodized aluminum oxide layer. The breath water vapor is adsorbed over the interdigitated electrodes and changes the sensor characteristic capacitance by up to two orders of magnitude. This modulated signal is then digitized and either stored in a memory or directly transmitted to a monitor through a short distance radio frequency (RF) link. Results show that the wireless platform can be powered by two AAA batteries and deployed in a mesh or star configuration as wireless sensor network. Full size of the microsensor is less than 1 cm2 and is conveniently implemented in a classical adhesive bandage or in nasal prongs. This microsystem is proposed for monitoring sleep-disordered breathing as well as breathing rhythm of athletes during effort.

Silicon-on-Insulator Photodiode on Micro-Hotplate Platform With Improved Responsivity and High-Temperature Application

This paper reports on the performance of a silicon-on-insulator photodiode suspended on a dielectric membrane. The micro-hotplate platform consists of a micro-heater and a thin-film lateral P+/P-/N+ (PIN) photodiode. Without optimizing the multilayer stack on top of the PIN diode, experimental responsivities of the suspended photodiodes at room temperature (RT) are 0.02-0.06/W within the visible and near the IR light range, under a reverse bias of -2 V. Up to 2.5×, responsivity improvement has been achieved with regard to the diodes on the substrate thanks to reflection from the gold finish layer of the device package acting as a bottom mirror. Optimizing the layer stack above the diode, the responsivity of the on-membrane device can be theoretically improved up to 0.09-0.11 A/W within 450-520-nm wavelength range. Measured from RT up to 200 °C, the photodiodes on membrane continuously show an improved optical response under high-power LED illumination. Assisted by the micro-heater as heat source, the suspended photodiode can work stably up to 200 °C with in situ temperature sensing and control, which makes it highly suitable and attractive for high-temperature application. Full 2-D ATLAS device simulations have been comprehensively performed to investigate the optical and electrical characteristics. Very good agreement has been achieved between the numerical simulations and the experimental data.

Ultra low power, harsh environment SOI-CMOS design of temperature sensor based threshold detection and wake-up IC

An ultra-low-power temperature-sensor-based silicon-on-insulator (SOI) CMOS Integrated Circuit (IC) for harsh environment application is presented. It first detects a temperature threshold, secondly generates a wake-up signal that turns on a data-acquisition microprocessor once the threshold has been detected and thirdly operates as a temperature sensor in a harsh environment while being wired to the microprocessor kept in a safe area. The IC is continuously on for a very long period of time and is required to be powered from a ultrathin battery type, hence must be an ultra low power design. It includes a diode-based temperature sensor, a quasi-temperature independent voltage generator, a comparator and a power switch to limit the microprocessor stand-by consumption. Since our application is mainly for harsh environment (e.g. high temperature, radiation), the chip has been designed using the 1-µm high-temperature SOI-CMOS XFAB technology; it occupies an area of 560µm×165µm. The biasing current and power dissipation are 4.12 µA and 20.6 µW respectively at a supply voltage of 5V and temperature of 27°C, according to the post-layout transistor level simulation results.

Ultra-Low Power High Temperature and Radiation Hard Complementary Metal-Oxide-Semiconductor (CMOS) Silicon-on-Insulator (SOI) Voltage Reference

This paper presents an ultra-low power CMOS voltage reference circuit which is robust under biomedical extreme conditions, such as high temperature and high total ionized dose (TID) radiation. To achieve such performances, the voltage reference is designed in a suitable 130 nm Silicon-on-Insulator (SOI) industrial technology and is optimized to work in the subthreshold regime of the transistors. The design simulations have been performed over the temperature range of −40–200 °C and for different process corners. Robustness to radiation was simulated using custom model parameters including TID effects, such as mobilities and threshold voltages degradation. The proposed circuit has been tested up to high total radiation dose, i.e., 1 Mrad (Si) performed at three different temperatures (room temperature, 100 °C and 200 °C). The maximum drift of the reference voltage VREF depends on the considered temperature and on radiation dose; however, it remains lower than 10% of the mean value of 1.5 V. The typical power dissipation at 2.5 V supply voltage is about 20 μW at room temperature and only 75 μW at a high temperature of 200 °C. To understand the effects caused by the combination of high total ionizing dose and temperature on such voltage reference, the threshold voltages of the used SOI MOSFETs were extracted under different conditions. The evolution of VREF and power consumption with temperature and radiation dose can then be explained in terms of the different balance between fixed oxide charge and interface states build-up. The total occupied area including pad-ring is less than 0.09 mm2.

Dew-Based Wireless Mini Module for Respiratory Rate Monitoring

Miniaturized humidity sensors combined with ZigBee transceiver and efficient data processing offer a powerful system for the monitoring of human breath. Every 10 ms, the expiration/inspiration phase is transmitted, allowing a medical diagnosis as efficient as required by the application. For the sensing system, a micro interdigitated capacitor, covered with a dense hydrophilic alumina layer, is connected to a capacitance-to-frequency circuit interface. A customized nasal canula-prototype embeds the microsystem underneath the patients nostrils while offering cabling until the belt-fixed radio transceiver. The fast data processing, executed in a mini notebook process unit, gives to the medical staff a live broadcast of the patients respiratory rate. In order to improve the size and the functionality of our sensing module, novel techniques for processing complementary metal oxide semiconductor (CMOS) in Silicon-on-Insulator (SOI) technology now allow for the construction of microsensors and CMOS circuits together on the same chip. These sensors consume extremely low power, of the order of 0.1 μW, present high sensitivity, occupy small chip area (1.25 mm2) and offer the prerequisite platform for a large variety of new sensors.

Testbed for IR-UWB based ranging and positioning: Experimental performance and comparison to CRLBs

In this paper we describe a testbed for impulse radio ultra wideband based ranging and positioning. We show the characteristics of the generated, transmitted and received pulses. We consider both the maximum likelihood estimator and a threshold-based estimator for the estimation of the time of arrival. We measure the variances for ranging and positioning and compare them to the Cramer-Rao lower bounds for range and position estimation. We discuss the impact of both false multipath component detection and false sidelobe detection on the estimation accuracy. The obtained variances are close to the Cramer-Rao lower bounds when the mainlobe of the first multi-path component is detected. In realistic multipath environments we can use a threshold-based time of arrival estimator in order to detect the first multipath component which may be missed by the maximum likelihood estimator. We show also that the errors on positioning due to false multipath component and sidelobe detection can be highly mitigated by increasing the number of receivers. For a radiated energy of 8.1 pJ and a distance of 5 meters between the transmit and receive antennas, the obtained accuracy is in the order of one centimeter.

Wide band study of silicon-on-insulator photodiodes on suspended micro-hotplates platforms

In this paper, the performances of a lateral thin-film PIN photodiode based on silicon-on-insulator technology are reported for applications from blue to red wavelengths. The platform consists of a micro-hotplate with a suspended heater and a photodiode. Responsivities of 0.01 to 0.05 A/W were obtained for 450-900 nm light range in reverse bias operation. Suspended photodiodes give up to 5x responsivity improvement with regard to the photodiodes on substrate. In addition to photodetection, the diode can monitor the temperature with a linear voltage decreasing by about 1.4 mV/K, under 50 μA constant forward current for a large range of temperature (measured from 25 to 300°C).

High temperature and radiation hard CMOS SOI sub-threshold voltage reference

A CMOS voltage reference circuit robust under harsh environments such as high temperature and high radiation total dose is presented. To achieve ultra-low-power and harsh environment operation, the voltage reference circuit is designed in a suitable 130 nm Silicon-on-Insulator technology and is optimized to work in sub-threshold regime of the transistors. The design simulations have been performed over all temperature ranges and process corners and with custom model parameters, including shifts in mobilities and threshold voltages caused by radiation effects. The measurements demonstrate a maximum drift of the mean reference voltage (1.5 V) lower than 5% at 1.5 Mrad (Si) total dose radiation. The typical power dissipation up to 200 °C is less than 75 μW at 2.5 V supply voltage. The total occupied area including pad-ring is less than 0.09 mm2.

Reliable characteristics and stabilization of on-membrane SOI MOSFET-based components heated up to 335??C

© 2016 IOP Publishing Ltd. In this work we investigate the characteristics and critical operating temperatures of on-membrane embedded MOSFETs from an experimental and analytical point of view. This study permits us to conclude the possibility of integrating electronic circuitry in the close vicinity of micro-heaters and hot operation transducers. A series of calibrations and measurements has been performed to examine the behaviors of transistors, inverters and diodes, actuated at high temperature, on a membrane equipped with an on-chip integrated micro-heater. The studied n- and p-channel body-tied partially-depleted MOSFETs and CMOS inverter are embedded in a 5 μm-thick membrane fabricated by back-side MEMS micromachining using SOI technology. It has been noted that a pre-stabilization step after the harsh post-CMOS processing, through an in situ high-temperature annealing using the micro-heater, is mandatory in order to stabilize the MOSFETs characteristics. The electrical characteristics and performance of the on-membrane MOS components are discussed when heated up to 335°C. This study supports the possibility of extending the potential of the micro-hotplate concept, under certain conditions, by embedding more electronic functionalities on the interface of on-membrane-based sensors leading to better sensing and actuation performances and a total area reduction, particularly for environmental or industrial applications.

In-situ thermal annealing of on-membrane silicon-on-insulator semiconductor-based devices after high gamma dose irradiation.

In this paper, we investigate the recovery of some semiconductor-based components, such as N/P-type field-effect transistors (FETs) and a complementary metal-oxide-semiconductor (CMOS) inverter, after being exposed to a high total dose of gamma ray radiation. The employed method consists mainly of a rapid, low power and in situ annealing mitigation technique by silicon-on-insulator micro-hotplates. Due to the ionizing effect of the gamma irradiation, the threshold voltages showed an average shift of -580 mV for N-channel transistors, and -360 mV for P-MOSFETs. A 4 min double-cycle annealing of components with a heater temperature up to 465 °C, corresponding to a maximum power of 38 mW, ensured partial recovery but was not sufficient for full recovery. The degradation was completely recovered after the use of a built-in high temperature annealing process, up to 975 °C for 8 min corresponding to a maximum power of 112 mW, which restored the normal operating characteristics for all devices after their irradiation.