Compact instrumentation for radiation tolerance test of flash memories in space environment
Aim of this work is the description of a test equipment, designed to be integrated on board of a microsatellite, able to investigate the radiation tolerance of non-volatile memory arrays in a real flight experiment. An FPGA-based design was adopted to preserve a high flexibility degree. Besides standard Program/Read/Erase functions, additional features such as failure data screening and latch-up protection have been implemented. The instrument development phase generated, as a by-product, a non-rad-hard version of the instrument that allowed performing in-situ experiments using 60Co and 10 MeV Boron irradiation facilities on Ground. Preliminary measurement results are reported to show the i…
Ionizing radiation effects on Non Volatile Read Only Memory cells
Threshold voltage (V-th) and drain-source current (I-DS) behaviour of nitride read only memories (NROM) were studied both in situ during irradiation or after irradiation with photons and ions. V-th loss fluctuations are well explained by the same Weibull statistics regardless of the irradiation species and total dose. Results of drain current measurements in-situ during irradiation with photons and ions reveal a step-like increase of I-DS with the total irradiation dose. A brief physical explanation is also provided.
Radiation effects in nitride read-only memories
Abstract We report on the influence of different types of radiation on the nitride read-only memories (NROM®). The memory cells were irradiated by light ions (Boron), X-rays and γ-rays. Memory transistor parameters, such as threshold voltage and subthreshold drain leakage were studied as a function of the accumulated radiation dose and compared to the as-programmed (-erased) devices parameters. Their time evolution was registered in the range from few hours up to 5 months after the irradiation. The NROM® cells showed good radiation robustness up to high accumulated doses. Sufficient program margin (difference of threshold voltage in the programmed state and the read-out voltage level) remai…
On the Relationship between Jetted Inks and Printed Biopatterns:Molecular-Thin Functional Microarrays of Glucose Oxidase
Arrays of circular spots of glucose oxidase have been obtained on functionalized silicon oxide by piezoelectric inkjet printing and the enzymatic activity toward glucose recognition has been monitored. The addition of glycerol to the molecular ink allows to obtain high spot definition and resolution (tens of micrometers wide; one molecule tall), but in spite of its well-known structural stabilizing properties, in dynamic conditions it may lead to increased protein stresses. The jetting voltage and pulse length have been found to be critical factors for both activity retention and pattern definition. High voltages and pulse lengths results in stress effects along with the loss of activity, w…
Si photomultipliers for bio-sensing applications
In this paper, silicon photomultipliers (SiPM) are proposed as optical detectors for bio sensing. Optical transduction is the most used detection mechanism in many biosensor applications, such as DNA microarray and real-time polymerase chain reaction. The performances of a 25 pixels device used for both applications are studied. The results confirm that the SiPM is more sensitive than the traditionally employed detectors. In fact, it is able to experimentally detect 1 nM and 100 fM of fluorophore concentrations in dried samples and solutions, respectively. We present and discuss in details the detector configuration and its characterization as fluorescence detector for bio sensing.
Fabrication and Characterization of Polymeric Optical Waveguides Using Standard Silicon Processing Technology
We report the fabrication and characterization of a rib polymeric waveguide having a thick layer of oxidized porous silicon as an innovative solution for the lower cladding. The waveguide was fabricated using standard silicon substrates and Si-based technology. The multimodal guiding structure has a polymethylmetacrylate (PMMA) core and the innovative lower cladding was obtained by thermal oxidation of a porous silicon layer. The waveguide does not have the upper cladding. Propagation loss measurements were performed at 1.48 /spl mu/m using the cut-back method. We obtained propagation loss of about 1.7 dB/cm, confirming the possibility to use the porous silicon oxide as the lower cladding l…
Design and development of a fNIRS system prototype based on SiPM detectors
Functional Near Infrared Spectroscopy (fNIRS) uses near infrared sources and detectors to measure changes in absorption due to neurovascular dynamics in response to brain activation. The use of Silicon Photomultipliers (SiPMs) in a fNIRS system has been estimated potentially able to increase the spatial resolution. Dedicated SiPM sensors have been designed and fabricated by using an optimized process. Electrical and optical characterizations are presented. The design and implementation of a portable fNIRS embedded system, hosting up to 64 IR-LED sources and 128 SiPM sensors, has been carried out. The system has been based on a scalable architecture whose elementary leaf is a flexible board …
Electrical characterization of deoxyribonucleic acid hybridization in metal-oxide-semiconductor-like structures
In this work, metal-oxide-semiconductor (MOS)-like sensors in which deoxyribonucleic acid (DNA) strands are covalently immobilized either on Si oxide or on a gold surface were electrically characterized. Si oxide fabrication process allowed us to have a surface insensitive to the solution pH. A significant shift in the flat band voltage was measured after single strand DNA immobilization (+0.47 +/- 0.04 V) and after the complementary strand binding (+0.07 +/- 0.02 V). The results show that DNA sensing can be performed using a MOS structure which can be easily integrated in a more complex design, thus avoiding the problems related to the integration of micro-electrochemical cells.
Preliminary radiation hardness tests of single photon Si detectors
Single photon Si detectors were fabricated by STMicroelectronics and fully characterized in standard operation conditions and after irradiations. Both single cells and arrays, of dimensions ranging from 5x5 up to 64x64, were electrically tested. The devices operation was studied as a function of the temperature from -25 degrees C to 65 degrees C varying the voltage over breakdown, from 5% up to 20% of the breakdown voltage before and after irradiation using both light ions, 10 MeV B ions to doses in the range 3x10(7)-5x10(10) cm(-2), and X-rays irradiations in the range 0.5-20 krad(Si). Optical characterization was performed using a laser at 659 nm and opportunely chosen filters to vary the…
Threshold Voltage Variability of NROM Memories After Exposure to Ionizing Radiation
Threshold voltage (V-th) behavior of nitride readonly memories (NROMs) was studied after irradiation with photons (gamma-and X-rays), light and heavy ions. Both programmed and nonprogrammed single cells were investigated. The data suggest that two main physical phenomena are contributing to V-th variation and that the V-th loss and the variability can be modeled by a Weibull statistics with a shape parameter k similar to 2.2 regardless of the irradiation species and total dose. The same peculiarities were found in large memory arrays, confirming the results from single-cell studies but with significantly larger statistics. Hence, once the irradiation dose is known, the V-th loss distributio…
CY5 fluorescence measured with silicon photomultipliers
This paper presents an efficient optical biosensor set up for a low-level light detection, using fluorescent dyes and a novel Si-based detector. Fluorescence emitted by a traditional fluorophore, CY5, widely used as optical label in DNA microarrays, was detected using a 25 pixels Silicon photomultiplier (SiPM), a device formed by avalanche diodes operating in Geiger mode, in parallel connections. We measured the fluorescence current in different deposition (fluorophore concentration; solvent; salt concentration) and operation (angle of analysis, optical laser power, device gain) conditions. The characterization of DNA samples labeled with CY5 is also reported to demonstrate the detector pot…
Radiation tolerance of NROM embedded products
Radiation tolerance of NROM memories is demonstrated at the level of industrial 4 Mbit memory embedded modules, specifically not designed for operation in radiation harsh environments. The memory fabricated in 0.18 um technology remains fully functional after total ionization doses exceeding 100 krad. The tests were performed by irradiating with γ-rays (60Co source) and 10 MeV 11B ions in active (during programming/erase and read-out) and passive (no bias) modes. Comprehensive statistics were obtained by using large memory arrays and comparison of the data with the parameters of irradiated single cells allowed deep understanding of the physical phenomena in the irradiated NROM devices for b…