M. Mazza

Bulk Lateral MEM Resonator on Thin SOI With High

The fabrication, design, and characterization of high-quality factor microelectromechanical (MEM) resonators fabricated on thin-film silicon-on-insulators (SOIs) are addressed in this paper. In particular, we investigate laterally vibrating bulk-mode resonators based on connected parallel beams [parallel beam resonators (PBRs)]. The experimental characteristics of PBRs are compared to disk resonators and rectangular plate resonators. All the reported MEM resonators are fabricated on 1.25-mum SOI substrates by a hard mask and deep reactive-ion etching process, resulting in transduction gaps smaller than 200 nm. Additionally, this fabrication process allows the growth of a thermal silicon dioxide layer on the resonators, which is used to compensate the resonance-frequency dependence on temperature. Quality factors Q, ranging from 20 000 at 32 MHz up to 100 000 at 24.6 MHz, are experimentally demonstrated. The motional resistances R m are compared for different designs, and values as low as 55 kOmega at 18 V of bias voltage are obtained with the thin SOI substrate. The thermal sensitivity of the resonance frequency is investigated from 200 K to 360 K, showing values of -15 ppm/K for the PBRs, with a possible compensation of 2 ppm/K when using 20 nm of SiO2.

Q

Conventional pharmaceutical processes involving cell culture growth are generally taken under control with expensive and long laboratory tests performed by direct sampling to evaluate quality. This traditional and well-established approach is just partially adequate in providing information about cell state. Electrochemical enzyme-based biosensors offer several advantages towards this application. In particular, they lend themselves to miniaturization and integration with cheap electronics. In the present work we go through the design, the development, and the validation of a self-contained device for the on-line measurement of metabolites in cell culture media. We microfabricated a sensing platform by using thin film technologies. We exploited electrodeposition to precisely immobilize carbon nanotubes and enzymes on miniaturized working electrodes. We designed and realized the electronics to perform the electrochemical measurements and an Android application to display the measurements on smartphones and tablets. In cell culture media glucose biosensor shows a sensitivity of 4.7 ± 1.3 nA mM(-1)mm(-2) and a detection limit of 1.4mM (S/N = 3σ), while for lactate biosensor the sensitivity is 12.2 ± 3.8 nA mM(-1)mm(-2) and the detection limit is 0.3mM. The whole system was then validated by monitoring U937 cell line over 88 h. Metabolic trends were fully congruent with cell density and viability. This self-contained device is a promising tool to provide more detailed information on cell metabolism that are unprecedented in cell biology.

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This work reports on the design, fabrication, and characterization of CMOS pixels for subretinal implants, which seems to be an effective way to recover visual capabilities in some types of blindness. Two possible approaches are presented for CMOS pixel implementation: 1) an approach based on a light-controlled oscillator (LICOS) using a ring oscillator with an odd number of inverters and 2) an approach based on distributing a square signal at each pixel that filters out a number of pulses depending of the light intensity wave across the chip (WATCH). Both types of pixels fabricated in 0.35-/spl mu/m CMOS demonstrate good mimic of the electrical behavior of human retina, with low-power consumption (typically 1 mW for a 14/spl times/14 matrix of pixels) and having small dimensions (75/spl times/78.5 /spl mu/m/sup 2/ for LICOS and 70/spl times/50 /spl mu/m/sup 2/ for WATCH), which make them suitable for practical implants. Experimental validation is reported on physiological solutions. Because of its characteristic, the proposed matrix of pixels could be considered as one of the first stand-alone highly integrated solutions for subretinal implant chips.

Design, development, and validation of an in-situ biosensor array for metabolite monitoring of cell cultures

N-doped polysilicon gated-nanowires (poly-SiNW) are reported. The V-shape and hysteresis of their I-V characteristics are used to build analog and memory circuit cells. Integration of the poly-SiNW in CMOS is demonstrated. A precise current-measurement application with 1pA resolution and negative differential resistor is reported. A nanoscale capacitor-less hysteresis memory cell using constant-current biased poly-SiNW is designed and experimentally validated.

CMOS pixels for subretinal implantable prothesis

Visual capabilities recovery for some kind of illness is possible through subretinal implantable device stimulation. Two possible architectures for retinal pixel are proposed, fabricated in 0.35 /spl mu/m CMOS and compared, including evaluation of electronic response on a human-tissue-like interface. In these solutions, power consumption has been proved to be dominated by electrode stimulation and, in normal light condition, typical consumption is below 1 mW/pixel. The proposed pixel architectures, with 120 /spl mu/m (LICOS) and 100 /spl mu/m (WATCH) inter-pixel step, provide the smallest, standalone, subretinal implantable chips ever reported.This work reports on the design, fabrication, and characterization of CMOS pixels for subretinal implants, which seems to be an effective way to recover visual capabilities in some types of blindness. Two possible approaches are presented for CMOS pixel implementation: 1) an approach based on a light-controlled oscillator (LICOS) using a ring oscillator with an odd number of inverters and 2) an approach based on distributing a square signal at each pixel that filters out a number of pulses depending of the light intensity wave across the chip (WATCH). Both types of pixels fabricated in 0.35-/spl mu/m CMOS demonstrate good mimic of the electrical behavior of human retina, with low-power consumption (typically 1 mW for a 14/spl times/14 matrix of pixels) and having small dimensions (75/spl times/78.5 /spl mu/m/sup 2/ for LICOS and 70/spl times/50 /spl mu/m/sup 2/ for WATCH), which make them suitable for practical implants. Experimental validation is reported on physiological solutions. Because of its characteristic, the proposed matrix of pixels could be considered as one of the first stand-alone highly integrated solutions for subretinal implant chips.

Nano-wires for room temperature operated hybrid CMOS-NANO integrated circuits

Thermo-optical and electro-optical (plasma dispersion) effects for silicon based integrated optical modulators are becoming attractive and effective solutions for telecommunications applications such as switching for programmable optical add-drop multiplexing for WDM. In this paper, a simple yet highly efficient novel electro-optical modulator device that exploits a SOI Schottky diode integrated in silicon rib wave-guide is proposed. Numerical 2D electrical (ATLAS/sup /spl copy/1/) and 3D optical (BPM/spl I.bar/CAD/sup /spl copy/2/)simulations are used to validate the principle and to explore the performances of the new device. We demonstrate that the SOI Schottky modulator has much better injection efficiency and significantly lower thermal effects compared to any conventional electro-optical modulators that use SOI p-i-n diodes, and, furthermore, by appropriate scaling down, can achieve unrivaled GHz high speed switching.

CMOS pixel for subretinal implantable prothesis

Scaling photonics devices in silicon on insulator (SOI) substrates has the potential to address important issues in the fields of optical telecommunications and optical interconnects. Silicon, is highly transparent in the infra-red spectral region and etching ribs or rectangular channels can create the condition for single-mode low-loss waveguiding. The high index difference between silicon and the surrounding media, typically SiO2 or air, is extremely favorable for the development of ultra-compact photonic devices. Active functionality can be performed by free charge injection in the waveguide resulting in a phase shift of the propagating fundamental mode. Moreover this technology is fully CMOS compatible allowing a low-cost monolithic integration of control electronics. Limitations deriving from an aggressive scaling of SOI waveguides are a lowered efficiency in the in-out coupling of light and higher propagation losses due to increased roughness scattering. We report on the perspectives and issues of scaling SOI photonics devices for both passive and active functionality. Results show that scaled waveguides can have very low bending radii down to the micrometer range. We also propose a new method and architecture for light phase modulation based on a Schottky barrier diode; a process flow will be analyzed and validated experimentally.

A novel SOI Schottky electro-optical modulator for GHz high-speed switching

This talk aims to demonstrate that a silicon-on-insulator (SOI) nanowire technological platform could be a realistic approach to address the development of various types of multifunctional devices. Particularly, SOI nanowires could be a unique technological platform to co-fabricate: (i) nano-scaled solid-state MOS devices (such as the multi-gate MOSFETs); (ii) single-electron transistors and single electron memories; (iii) solid-state optoelectronic nano-scaled devices (modulators, optical switches, filters or even optical, interconnects for on-chip clock distribution...); and (iv) MEMS nano-resonators for full integrated RF IC functions. All these various categories of devices can take advantage of SOI intrinsic properties (technological toolset similar to silicon, natural lateral and vertical isolation, specific electrical, mechanical and optical properties) together with their aggressive scalability. Moreover, such, a technological platform could be hybridized with other nanotechnologies like molecular devices and carbon nanotubes. Some key examples, based on ongoing research projects at the Swiss Federal Institute of Technology Lausanne and world wide state-of-the-art was presented.

Scaling SOI photonics to micron and sub-micron devices

Partial visual capabilities for some kind of blindness are still possible through direct electrical stimulation of retinal tissue. In this work, tunable implantable silicon CMOS pixel are presented and experimentally validated. Pulse width, stimulating output current and light sensibility may be regulated by external voltages, making this solution suitable for an auto-adapting artificial retina. Power consumption due to light detection and conversion is absolutely negligible compared to dissipation required for stimulating photoreceptors. The pixel pitch of around 70mum makes it among the smallest reported to-date

Emerging nanoelectronics: multi-functional nanowires

This paper presents the electrical design and characterization of a wafer-level, or 0-level, package for micro-electromechanical resonators. We start by identifying the requirements on the electrical parasitics of a packaged resonator, derived from an analysis of the oscillator circuit comprising the resonator. Then, using the deduced requirements as a starting point, an optimized design of the package is developed in a two-step procedure. First, initial choices for the package topology are made on the basis of intuitive and physical circuit models. Second, a more detailed analysis is carried out by means of full-wave simulations and circuit models extractions. Measured results on empty packages are presented, validating both circuit models and full-wave simulation results. Finally, the parasitics values obtained are discussed in the light of the implementation of an oscillator circuit, demonstrating the possibility to implement functioning oscillators based on the proposed package.