Performance of a novel wafer scale CMOS active pixel sensor for bio-medical imaging

Recently CMOS Active Pixels Sensors (APSs) have become a valuable alternative to amorphous Silicon and Selenium Flat Panel Imagers (FPIs) in bio-medical imaging applications. CMOS APSs can now be scaled up to the standard 20 cm diameter wafer size by means of a reticle stitching block process. However despite wafer scale CMOS APS being monolithic, sources of non-uniformity of response and regional variations can persist representing a significant challenge for wafer scale sensor response. Non-uniformity of stitched sensors can arise from a number of factors related to the manufacturing process, including variation of amplification, variation between readout components, wafer defects and process variations across the wafer due to manufacturing processes. This paper reports on an investigation into the spatial non-uniformity and regional variations of a wafer scale stitched CMOS APS. For the first time a per-pixel analysis of the electro-optical performance of a wafer CMOS APS is presented, to address inhomogeneity issues arising from the stitching techniques used to manufacture wafer scale sensors. A complete model of the signal generation in the pixel array has been provided and proved capable of accounting for noise and gain variations across the pixel array. This novel analysis leads to readout noise and conversion gain being evaluated at pixel level, stitching block level and in regions of interest, resulting in a coefficient of variation ≤ 1.9%. The uniformity of the image quality performance has been further investigated in a typical X-ray application, i.e. mammography, showing a uniformity in terms of CNR among the highest when compared with mammography detectors commonly used in clinical practise. Finally, in order to compare the detection capability of this novel APS with the currently used technology (i.e. FPIs), theoretical evaluation of the Detection Quantum Efficiency (DQE) at zero-frequency has been performed, resulting in a higher DQE for this detector compared to FPIs. Optical characterization, X-ray contrast measurements and theoretical DQE evaluation suggest that a trade off can be found between the need of a large imaging area and the requirement of a uniform imaging performance, making the DynAMITe large area CMOS APS suitable for a range of bio-medical applications

Bio-inspired 0.35μm CMOS Time-to-Digital Converter with 29.3ps LSB

Time-to-digital converter (TDC) integrated circuit is introduced in this paper. It is based on chain of delay elements composing a regular scalable structure. The scheme is analogous to the sound direction sensitivity nerve system found in barn owl. The circuit occupies small silicon area, and its direct mapping from time to position-code makes conversion rates up to 500Msps possible. Specialty of the circuit is the structural and functional symmetry. Therefore the role of start and stop signals are interchangeable. In other words negative delay is acceptable: the circuit has no dead time problems. These are benefits of the biology model of the auditory scene representation in the bird's brain. The prototype chip is implemented in 0.35μm CMOS having less than 30ps single-shot resolution in the measurements.Hungarian National Research Foundation TS4085

Recent Design Development in Molecular Imaging for Breast Cancer Detection Using Nanometer CMOS Based Sensors

As one of the key clinical imaging methods, the computed X-ray tomography can be further improved using new nanometer CMOS sensors. This will enhance the current technique's ability in terms of cancer detection size, position, and detection accuracy on the anatomical structures. The current paper reviewed designs of SOI-based CMOS sensors and their architectural design in mammography systems. Based on the existing experimental results, using the SOI technology can provide a low-noise (SNR around 87.8 db) and high-gain (30 v/v) CMOS imager. It is also expected that, together with the fast data acquisition designs, the new type of imagers may play important roles in the near-future high-dimensional images in additional to today's 2D imagers

Miniaturization of fluorescence sensing in optofluidic devices

International audienceSuccessful development of a micro-total-analysis system (μTAS, lab-on-a-chip) is strictly related to the degree of miniaturization, integration, autonomy, sensitivity, selectivity, and repeatability of its detector. Fluorescence sensing is an optical detection method used for a large variety of biological and chemical assays, and its full integration within lab-on-a-chip devices remains a challenge. Important achievements were reported during the last few years, including improvements of previously reported methodologies, as well as new integration strategies. However, a universal paradigm remains elusive. This review considers achievements in the field of fluorescence sensing miniaturization, starting from off-chip approaches, representing miniaturized versions of their lab counter-parts, continuing gradually with strategies that aim to fully integrate fluorescence detection on-chip, and reporting the results around integration strategies based on optical-fiber-based designs,optical layer integrated designs, CMOS-based fluorescence sensing, and organic electronics. Further successful development in this field would enable the implementation of sensing networks in specific environments that, when coupled to Internet of-Things (IoT) and artificial intelligence (AI), could provide real-time data collection and, therefore, revolutionize fields like health, environmental, and industrial sensing

CMOS pixel sensor development: a fast read-out architecture with integrated zero suppression

International audienceCMOS Monolithic Active Pixel Sensors (MAPS) have demonstrated their strong potential for tracking devices, particularly for flavour tagging. They are foreseen to equip several vertex detectors and beam telescopes. Most applications require high read-out speed, which imposes sensors to feature digital output with integrated zero suppression. The most recent development of MAPS at IPHC and IRFU addressing this issue will be reviewed. The design architecture, combining pixel array, column-level discriminators and zero suppression circuits, will be presented. Each pixel features a preamplifier and a correlated double sampling (CDS) micro-circuit reducing the temporal and fixed pattern noises. The sensor is fully programmable and can be monitored. It will equip experimental apparatus starting data taking in 2009/2010

Monolithic Perimeter Gated Single Photon Avalanche Diode Based Optical Detector in Standard CMOS

Since the 1930\u27s photomultiplier tubes (PMTs) have been used in single photon detection. Single photon avalanche diodes (SPADs) are p-n junctions operated in the Geiger mode. Unlike PMTs, CMOS based SPADs are smaller in size, insensitive to magnetic fields, less expensive, less temperature dependent, and have lower bias voltages. Using appropriate readout circuitry, they measure properties of single photons, such as energy, arrival time, and spatial path making them excellent candidates for single photon detection. CMOS SPADs suffer from premature breakdown due to the non-uniform distribution of the electric field. This prevents full volumetric breakdown of the device and reduces the detection effciency by increasing the noise. A novel device known as the perimeter gated SPAD (PGSPAD) is adopted in this dissertation for mitigating the premature perimeter breakdown without compromising the fill-factor of the device. The novel contributions of this work are as follows. A novel simulation model, including SPICE characteristics and the stochastic behavior, has been developed for the perimeter gated SPAD. This model has the ability to simulate the static current-voltage and dynamic response characteristics. It also simulates the noise and spectral response. A perimeter gated silicon photomultiplier, with improved signal to noise ratio, is reported for the first time. The gate voltage reduces the dark current of the silicon photomultiplier by preventing the premature breakdown. A digital SPAD with the tunable dynamic range and sensitivity is demonstrated for the first time. This pixel can be used for weak optical signal application when relatively higher sensitivity and lower input dynamic range is required. By making the sensitivity-dynamic range trade-off the same detector can be used for applications with relatively higher optical power. Finally, an array has been developed using the digital silicon photomultiplier in which the dead time of the pixels have been reduced. This digital photomultiplier features noise variation compensation between the pixels

Bioelectronics for Amperometric Biosensors

The Discrete-to-Integrated Electronics group (D2In), at the University of Barcelona, in partnership with the Bioelectronics and Nanobioengineering Group (SICBIO), is researching Smart Self-Powered Bio-Electronic Systems. Our interest is focused on the development of custom built electronic solutions for bio-electronics applications, from discrete devices to Application-specific integrated circuit (ASIC) solutions. The integration of medical and electronic technologies allows the development of biomedical devices able to diagnose and/or treat pathologies by detecting and/or monitoring pathogens, multiple ions, PH changes, and so on. Currently this integration enables advances in various areas such as microelectronics, microfluidics, microsensors and bio-compatible materials which open the door to developing human body Lab-on-a-Chip implantable devices, Pointof- Care in vitro devices, etc. In this chapter the main attention is focused on the design of instrumentation related to amperometrics biosensor: biopotentiostat amplifiers and lock-in amplifiers. A potentiostat is a useful tool in many fields of investigation and industry performing electrochemical trials [1], so the quantity and variety of them is very extensive. Since they can be used in studies and targets as different as the study of chemical metal conversions [2] or carcinogenic cells detection, neuronal activity detection or Deoxyribonucleic acid (DNA) recognition, their characteristics are very varied..