Commercial CMOS Research Articles

ToASt: A 64-channel ASIC for the readout of the Silicon Strip Detectors of the PANDA experiment

The silicon strip sensors for the Micro Vertex Detector (MVD) of the PANDA experiment must provide both the Time of Arrival (ToA) and the charge released by the crossing particle. In order to cope with these requirements a 64-channel dedicated ASIC, named ToASt, has been designed and extensively tested. Each channel includes a charge-sensitive amplifier, a current mode shaper, a linear Time over Threshold (ToT) stage and double threshold discrimination. The ToA and ToT are obtained by storing the value of a 12-bit time stamp at the two edges of the comparator. The two values are immediately readout by a digital interface, formatted in 32-bit words and transmitted, via two 160 MS/s serial links.The ToASt ASIC is designed in a commercial CMOS 110 nm technology. Its digital logic has been triplicated in order to improve its Single-Event Upset (SEU) protection.

Selecting alternative metals for advanced interconnects

Interconnect resistance and reliability have emerged as critical factors limiting the performance of advanced CMOS circuits. With the slowdown of transistor scaling, interconnect scaling has become the primary driver of continued circuit miniaturization. The associated scaling challenges for interconnects are expected to further intensify in future CMOS technology nodes. As interconnect dimensions approach the 10 nm scale, the limitations of conventional Cu dual-damascene metallization are becoming increasingly difficult to overcome, spurring over a decade of focused research into alternative metallization schemes. The selection of alternative metals is a highly complex process, requiring consideration of multiple criteria, including resistivity at reduced dimensions, reliability, thermal performance, process technology readiness, and sustainability. This Tutorial introduces the fundamental criteria for benchmarking and selecting alternative metals and reviews the current state of the art in this field. It covers materials nearing adoption in high-volume manufacturing, materials currently under active research, and potential future directions for fundamental study. While early alternatives to Cu metallization have recently been introduced in commercial CMOS devices, the search for the optimal interconnect metal remains ongoing.

Implementation of the diagnostic capabilities of the CMOS sensor in the NIR environment, using 1070 nm interference filter and a conventional IR-pass filters set

NIR reflectography with silicon sensors (CMOS) is commonly acquired with 780 nm band-pass filters that allow the acquisition of clear images and high shutter speeds, while maintaining a low equipment cost. In this way, however, acquisition between 1000 nm and 1150nm-where the silicon sensor is still formally infrared sensitive-is in fact overhelmed by the stronger sensitivity in the infrared spectrum portion between 780 nm and 980 nm. Coupling a 1070 nm (± 5 nm) interferencial filter to an 87C nm IR pass filter (FHWH 850 nm) acquisitions in this portion of the NIR spectrum were carried out, witnessing a outstanding increase in visibility of underdrawings and pentimenti. A practical test of the effectiveness of the filters system mounted on the Nikon D800 IRUV was made, comparing the results with those obtained by the “Osiris” InGaAs detector by Opus Instruments. The comparison was performed on the “Deposition” (oil on panel) by Antonio Semino (1485–1555) in the collection of the Accademia Ligustica of Genoa, highlighting a significant qualitative proximity between the results obtained with the interference system and those with InGaAs detector, compared to the conventional acquisition with single IR long-pass filter.In addition, the 1070nm+87C filter system was used to increase the recognition capability of azurite pigments. This procedure widens the possibilities of first-impact diagnostics by means of low-cost and market available imaging systems based on commercial CMOS IRUV cameras..

Miniature spectrometer based on graded bandgap perovskite filter.

Miniature spectrometer is powerful tool for scientific research and industrial inspection. Here, we report the fabrication of graded perovskite filters with tunable bandgap and their application in constructing miniature spectrometer. The graded perovskite filters were fabricated using a Finkelstein reaction between in-situ formed halogen ion with a preformed MAPbX3 film. The graded bandgap of perovskite films can be well tunned from 400 to 750 nm by controlling the volume ratio between 5,5-dimethyl-1-pyrroline N-oxide and benzyl chloride(bromide). By combining a deep residual network, graded bandgap perovskite film and commercial CMOS sensor chip, a miniature spectrometer is demonstrated, achieving an accurate spectrum reconstruction (PSNR = 40.749) with monochromatic spectral resolution of 1.31 nm.

Utilizing layout effects for analog logic locking

While numerous obfuscation techniques are available for securing digital assets in the digital domain, there has been a notable lack of focus on protecting intellectual property (IP) in the analog domain. This is primarily due to the relatively smaller footprint of analog components within an integrated circuit (IC), with the majority of the surface dedicated to digital elements. However, despite their smaller nature, analog components are highly valuable IP and warrant effective protection. In this paper, we present a groundbreaking method for safeguarding analog IP by harnessing layout-based effects that are typically considered undesirable in IC design. Specifically, we exploit the impact of length of oxide diffusion and well proximity effect on transistors to fine-tune critical parameters such as transconductance (gm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_{m}$$\\end{document}) and threshold voltage (Vth\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{th}$$\\end{document}). These parameters remain concealed behind key inputs, akin to the logic locking approach employed in digital ICs. Our research explores the application of layout-based effects in two commercial CMOS technologies, namely a 28 nm and a 65 nm node. To demonstrate the efficacy of our proposed technique, we implement it for locking an operational transconductance amplifier. Extensive simulations are performed, evaluating the obfuscation strength by applying a large number of key sets (over 50,000 and 300,000). The results exhibit a significant degradation in performance metrics, such as open-loop gain (up to 130 dB), phase margin (up to 50∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ $$\\end{document}), 3 dB bandwidth (approximately 2.5 MHz), and power consumption (around 1 mW) when incorrect keys are employed. Our findings highlight the advantages of our approach as well as the associated overhead.

A 5.12-Gbps serializer circuit for front-end fast readout electronics of silicon pixelated detectors

Advanced synchrotron radiation sources are major facilities for analyzing the formation and evolution of material structure in multidisciplinary research, owing to their high luminosity, low emittance, wide energy bandwidth and other characteristics. In China, several advanced synchrotron radiation sources are under construction, including the HEPS (High Energy Photon Source) and SHINE (Shanghai high repetition rate X-ray Free Electron Laser and extreme light facility). These facilities are poised to become major multidisciplinary research platforms in China. To meet the requirements of pixel detectors in these facilities, dedicated pixel readout chips are being developed, including HEPS-BPIX and HYLITE. This paper presents a high-speed serializer circuit developed in a commercial 130-nm CMOS technology for the full-scale (128 × 128) pixel readout chip of HYLITE, which requires a data rate of 4 Gbps currently. The serializer consists of a 16-to-1 binary-tree multiplexer, a ring-oscillating-based phase-locked loop (RO-PLL) and a current-mode logic driving stage with a multi-stage pre-amplifier. Test results demonstrate its expected functionality within a wide operating range from 0.52 Gbps to 5.5 Gbps. At 5.12 Gbps, the measured jitter values are about 2 ps for random jitter, 20 ps for deterministic jitter, and 47 ps for total jitter with a 10−12 bit error rate. Additionally, the horizontal and vertical eye openings are 0.84 UI and 72%, respectively. These positive results indicate that the serializer meets the requirements of HYLITE.

Breakdown performance of guard ring designs for pixel detectors in 150 nm CMOS technology

Silicon pixel sensors manufactured using commercial CMOS processes are promising instruments for high-energy particle physics experiments due to their high yield and proven radiation hardness. As one of the essential factors for the operation of detectors, the breakdown performance of pixel sensors constitutes the upper limit of the operating voltage. Six types of passive CMOS test structures were fabricated on high-resistivity wafers. Each of them features a combination of different inter-pixel designs and sets of floating guard rings, which differ from each other in the geometrical layout, implantation type, and overhang structure. A comparative study based on leakage current measurements in the sensor substrate of unirradiated samples was carried out to identify correlations between guard ring designs and breakdown voltages. TCAD simulations using the design parameters of the test structures were performed to discuss the observations and, together with the measurements, ultimately provide design features targeting higher breakdown voltages.

A 1-16-Gb/s All-Digital Clock and Data Recovery With a Wideband, High-Linearity Phase Interpolator

An all-digital phase interpolator (PI)-based clock and data recovery (CDR) is proposed in this paper to accommodate any data rate continuously from 1 to 16 Gb/s with quadrature sampling clocks from 4 to 8 GHz. A new low-power two-step PI (TSPI) with high linearity over 4–8 GHz range is presented. The all-digital CDR control loop adopts a multimode phase detection scheme enabling continuous data rate support. The digital architecture not only eliminates the large filtering capacitor but also makes the design more tolerant to process, voltage, and temperature variations. The CDR core occupies 0.088 mm2 in a commercial 65-nm CMOS technology and consumes 73.1 mA at 16 Gb/s from a 1.2 V power supply. The differential nonlinearity of the PI is measured to be within 0.48 LSB. The measurement results show that this CDR can function at the proposed phase detection modes and is able to exceed the synchronous optical networking (SONET) OC-192 jitter tolerance mask at least by 0.2 unit interval at high frequencies (4–100 MHz) with a $2^{31}-1$ pseudorandom binary sequence data pattern at 10 Gb/s and a target bit error rate of $10^{-12}$ .

Experimental demonstration of coupled differential oscillator networks for versatile applications.

Oscillatory neural networks (ONNs) exhibit a high potential for energy-efficient computing. In ONNs, neurons are implemented with oscillators and synapses with resistive and/or capacitive coupling between pairs of oscillators. Computing is carried out on the basis of the rich, complex, non-linear synchronization dynamics of a system of coupled oscillators. The exploited synchronization phenomena in ONNs are an example of fully parallel collective computing. A fast system's convergence to stable states, which correspond to the desired processed information, enables an energy-efficient solution if small area and low-power oscillators are used, specifically when they are built on the basis of the hysteresis exhibited by phase-transition materials such as VO2. In recent years, there have been numerous studies on ONNs using VO2. Most of them report simulation results. Although in some cases experimental results are also shown, they do not implement the design techniques that other works on electrical simulations report that allow to improve the behavior of the ONNs. Experimental validation of these approaches is necessary. Therefore, in this study, we describe an ONN realized in a commercial CMOS technology in which the oscillators are built using a circuit that we have developed to emulate the VO2 device. The purpose is to be able to study in-depth the synchronization dynamics of relaxation oscillators similar to those that can be performed with VO2 devices. The fabricated circuit is very flexible. It allows programming the synapses to implement different ONNs, calibrating the frequency of the oscillators, or controlling their initialization. It uses differential oscillators and resistive synapses, equivalent to the use of memristors. In this article, the designed and fabricated circuits are described in detail, and experimental results are shown. Specifically, its satisfactory operation as an associative memory is demonstrated. The experiments carried out allow us to conclude that the ONN must be operated according to the type of computational task to be solved, and guidelines are extracted in this regard.

Silicon nano-bridge waveguide assisted polarizing beam splitter

A low-loss and wideband silicon polarizing beam splitter is demonstrated with the assistance of a nano-bridge waveguide. Transverse magnetic light can be coupled to the cross port through the nano-bridge waveguide, while the transverse electric light comes out mainly from the through port. The designed device has a coupling length of 19.6 µm, which can realize an extinction ratio of 32.43 dB for TM mode or 34.23 dB for TE mode at a 1565-nm wavelength. Compared with the conventional three-waveguide coupler structure, the proposed device is based on a resonant tunneling principle, which can help to effectively improve the fabrication tolerance. The device is fabricated with a commercial CMOS processing facility, which can achieve an extinction ratio of 23.07 dB for TM or 23.46 dB for TE mode with a low excess loss, and the extinction ratio of more than 10 dB can be realized in the wavelength range from 1525 to 1610 nm for both modes. The device performance can be further improved, which would facilitate its practical applications in commercial integrated optical circuits.

Metal Microelectromechanical Resonator Exhibiting Fast Human Activity Detection.

This work presents a MEMS resonator used as an ultra-high resolution water vapor sensor (humidity sensing) to detect human activity through finger movement as a demonstrator example. This microelectromechanical resonator is designed as a clamped-clamped beam fabricated using the top metal layer of a commercial CMOS technology (0.35 μm CMOS-AMS) and monolithically integrated with conditioning and readout circuitry. Sensing is performed through the resonance frequency change due to the addition of water onto the clamped-clamped beam coming from the moisture created by the evaporation of water in the human body. The sensitivity and high-speed response to the addition of water onto the metal bridge, as well as the quick dewetting of the surface, make it suitable for low-power human activity sensing.

Maximum output power point tracking for photovoltaic energy harvesting systems: Mathematical model and circuit implementation

Maximizing the power transferred to the load is a key feature in any energy harvesting system. Contrary to traditional approaches, this paper mathematically demonstrates that performing a maximum power point tracking on the power delivered to the load instead of on the photogenerated power allows to harvest up to 25% more power due to setting less demanding operating conditions. A circuit implementation of a system that successfully maximizes its output by exclusively taking measurements of the output voltage is designed and demonstrated using a 180 nm commercial CMOS process. The system operates at μW range and achieves a peak power conversion efficiency of 79.04% at 30.74 μW output.

CMOS-compatible self-quenched active recovery (SQUARE) single-photon detector

Current CMOS single-photon detectors operating in Geiger mode use passive quenching, yielding slow recovery due to the RC delay. Active quenching of CMOS photon detectors operating in the Geiger mode requires external quenching circuitry that occupies a large area, reducing the fill factor and spatial resolution. Here, we demonstrate a self-quenched active recovery (SQUARE) single-photon detector having its recovery accelerated by a secondary carrier multiplication process. The device consists of two gain regions, one giving rise to the photon response and the other quenching the device and amplifying the residual current for a speedy self-recovery. The first gain region is a crystalline silicon p/n junction fabricated through a commercial CMOS process, and the second gain region is a carbon-doped amorphous silicon layer deposited on the top metal layer of a completed CMOS wafer. The SQUARE single-photon detector shows a Geiger-mode gain greater than 100 000 and achieved <30 ns self-recovery time, much faster than self-quenched and passively quenched single-photon avalanche photodiodes reported to date.

Neutron autoradiography with nuclear tracks detectors: an imaging technique for Boron Neutron Capture Therapy

Boron Neutron Capture Therapy (BNCT) is a radiation treatment modality for cancer based on the 10B(n,α)7Li (BNC) reaction. Knowledge of the spatial location of boron atoms is essential when considering a BNCT treatment, since the BNC reaction products cause lethal damage in a range comparable to cell diameter. Neutron autoradiography is a technique able to provide this information with high resolution at relatively low cost. First a boron-loaded biological matrix is laid on a nuclear track detector (NTD). By irradiating this assembly with thermal neutrons, the emitted particles of the BNC reaction produce damaged zones in the NTD along each incident ion trajectory, and by mapping these nuclear tracks boron spatial distribution in the sample can be assessed. In our laboratory, we have established different approaches: high fluence autoradiography (HFA), to observe boron microdistribution through differences in shades of gray; quantitative autoradiography (QTA), which allows the correlation between track density measurements and boron concentration; and UV-C sensitization of polymers (UVC-a), which produces an imprint of the biological material in the NTD, thus improving the spatial resolution. Moreover, we aim to develop a technique using commercial CMOS sensors in order to simultaneously detect the BNC events and the image of the biological sample during irradiation. The objective of this work is to describe the mentioned approaches and to discuss future perspectives.

Laboratory Characterisation of a Commercial RGB CMOS Camera for Measuring Night Sky Brightness

The use of RGB cameras in photometric applications has grown over the last few decades in many fields such as industrial applications, light engineering and the analysis of the quality of the night sky. In this last field, they are often used in conjunction with a Sky Quality Meter (SQM), an instrument used for the measurement of night sky brightness (NSB), mainly when there is a significant amount of artificial light at night (ALAN). The performances of these two instruments are compared here. A simple source composed of nine narrowband LEDs in an integrating sphere was used to excite the two instruments and therefore measure the spectral responsivity of the SQM and of the three channels of the camera. The estimated uncertainties regarding spectral responsivity were less than 10%. A synthetic instrument approximating the SQM’s responsivity can be created using a combination of the R, G and B channels. The outputs of the two instruments were compared by measuring the spectral radiance of the night sky. An evaluation of the spectral mismatch between the two instruments completed the analysis of their spectral sensitivity. Finally, the measurements of real SQMs in four sites experiencing different levels of light pollution were compared with the values obtained by processing the recorded RGB images. Overall, the analysis shows that the two instruments have significantly different levels of spectral responsivity, and the alignment of their outputs requires the use of a correction which depends on the spectral distribution of the light coming from the sky. A synthetic SQM will always underestimate real SQM measures; an average correction factor was evaluated considering nine sky spectra under low and medium levels of light pollution; this was determined to be 1.11 and, on average, compensated for the gap. A linear correction was also supposed based on the correlation between the NSB levels measured by the two instruments; the mean squared error after the correction was 0.03 mag arcsec−2.

Three-dimensional oxygen concentration monitoring in hydrogels using low-cost phosphorescence lifetime imaging for tissue engineering.

Oxygen concentration measurement in 3D hydrogels is vital in 3D cell culture and tissue engineering. However, standard 3D imaging systems capable of measuring oxygen concentration with adequate precision are based on advanced microscopy platforms, which are not accessible in many laboratories due to the system's complexity and the high price. In this work, we present a fast and low-cost phosphorescence lifetime imaging design for measuring the lifetime of oxygen-quenched phosphorescence emission with 0.25 µs temporal precision and sub-millimeter spatial resolution in 3D. By combining light-sheet illumination and the frequency-domain lifetime measurement using a commercial rolling-shutter CMOS camera in the structure of a conventional optical microscope, this design is highly customizable to accommodate application-specific research needs while also being low-cost as compared to advanced instruments. As a demonstration, we made a fluidic device with a gas-permeable film to create an artificial oxygen gradient in the hydrogel sample. Dye-embedded beads were distributed in the hydrogel to conduct continuous emission lifetime monitoring when nitrogen was pumped through the fluidic channel and changed oxygen distribution in the sample. The dynamics of the changes in lifetime co-related with their location in the gel of size 0.5 mm×1.5 mm×700 µm demonstrate the ability of this design to measure the oxygen concentration stably and precisely in 3D samples.

An IEEE-Compatible JTAG Test-Access-Port Controller for RSFQ Logic and Systems

JTAG, an IEEE-standard test protocol, is widely used for testing commercial and experimental CMOS chips but appears unused for testing superconducting chips. The test-access-port (TAP) controller described here facilitates the use of JTAG to reduce the cost – in time and effort – of testing superconductive circuits. Our RSFQ-based TAP controller shifts data serially through a scan chain that transfers data in parallel to and from a circuit under test. Suitably designed scan chains can provide initial values to superconducting circuits and retrieve results to explore circuit behavior. A control computer or an internet connection can operate our TAP controller through a simple five-wire interface. Our TAP controller implements the TAP part of IEEE standard 1149.8.1-2012 in an area of only 580 x 280 micrometers, less area than two bonding pads. Our TAP Controller design information and MIT SFQ5ee layout will be freely available.

Time-Domain Multiply–Accumulate Unit

In this article, a novel approach for performing multiply–accumulate (MAC) operations in the time-domain is presented. The Internet of Things, machine learning, and 5G are driving up demand for this type of operation, which is also crucial for many applications that rely on digital signal processing (DSP). For accomplishing this operation, a fully time-domain MAC unit capable of consecutively multiplying two input time pulses and adding them to previously stored signals is proposed. The main component of the circuit is the time register, which adds and stores time information. The MAC unit design is realized in commercial 180-nm CMOS process and occupies an estimated area of about 3167 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The proposed circuit can perform MAC operations with less than 5% error for a dynamic range (DR) of 19 ns, presenting an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R$</tex-math> </inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> linearity of over 0.99. Its power consumption is 1.72 mW from a 1.8-V supply.

The “LED‐version” of the electron gun

SummaryWe report on our progress to develop and optimize electron sources for practical applications. A simple fabrication process is introduced based on a wafer dicing saw and a wet chemical etch step without the need for a clean room. Due to the formation of crystal facets the samples show a homogeneous geometry throughout the array. Characterization techniques are developed to systematically compare various arrays. A very defined measurement procedure based on current controlled IV‐sweeps as well as lifetime measurements at various currents is proposed. To investigate the current distribution in the array a commercial CMOS detector is used and shows the potential for in depth analysis of the arrays. Finally, a compact hermetically sealed housing is presented enabling electron generation in atmospheric pressure environments.

The LiTE-DTU: A Data Conversion and Compression ASIC for the Readout of the CMS Electromagnetic Calorimeter

The High-Luminosity phase of operation of the CERN LHC collider (HL-LHC) will pose new challenges to the detectors and their readout electronics. In particular, the CMS barrel electromagnetic calorimeter will require a full redesign of the electronic readout chain in order to cope with the increase in luminosity and trigger rate. In this framework, a new Application Specific Integrated Circuit (ASIC) integrating A/D conversion, lossless data compression and high speed transmission has been developed and tested. The ASIC, named LiTE-DTU, is designed in a commercial CMOS 65 nm process and embeds two 12-bit, 160 MS/s Analog to Digital Converters (ADCs), a data selection and compression logic, and a 1.28 Gb/s output serial link. The high-speed 1.28 GHz clock is generated internally from the 160 MHz input by a clock multiplication Phase-Locked Loop (PLL). The circuit has been designed implementing radiation tolerant techniques in order to work in the harsh environment of the HL-LHC upgrade. The LiTE-DTU is currently in the pre-production phase. A sample of 600 chips has been tested and incorporated into front end boards for systems performance testing.