Archives for November 2023

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ISSCC will be held Feb 18-22, 2024 in San Francisco, CA.

Link to advanced program: https://submissions.mirasmart.com/ISSCC2024/PDF/ISSCC2024AdvanceProgram.pdf

There are several papers of interest in Session 6 on Imagers and Ultrasound. 

6.1 12Mb/s 4×4 Ultrasound MIMO Relay with Wireless Power and Communication for Neural Interfaces
E. So, A. Arbabian (Stanford University, Stanford, CA)

6.2 An Ultrasound-Powering TX with a Global Charge-Redistribution Adiabatic Drive Achieving 69% Power Reduction and 53° Maximum Beam Steering Angle for Implantable Applications
M. Gourdouparis1,2, C. Shi1 , Y. He1 , S. Stanzione1 , R. Ukropec3 , P. Gijsenbergh3 , V. Rochus3 , N. Van Helleputte3 , W. Serdijn2 , Y-H. Liu1,2
 1 imec, Eindhoven, The Netherlands
 2 Delft University of Technology, Delft, The Netherlands
 3 imec, Leuven, Belgium

6.3 Imager with In-Sensor Event Detection and Morphological Transformations with 2.9pJ/pixel×frame Object Segmentation FOM for Always-On Surveillance in 40nm
 J. Vohra, A. Gupta, M. Alioto, National University of Singapore, Singapore, Singapore

6.4 A Resonant High-Voltage Pulser for Battery-Powered Ultrasound Devices
 I. Bellouki1 , N. Rozsa1 , Z-Y. Chang1 , Z. Chen1 , M. Tan1,2, M. Pertijs1
 1 Delft University of Technology, Delft, The Netherlands
 2 SonoSilicon, Hangzhou, China

6.5 A 0.5°-Resolution Hybrid Dual-Band Ultrasound Imaging SoC for UAV Applications
 J. Guo1 , J. Feng1 , S. Chen1 , L. Wu1 , C-W. Tsai1,2, Y. Huang1 , B. Lin1 , J. Yoo1,2
 1 National University of Singapore, Singapore, Singapore
 2 The N.1 Institute for Health, Singapore, Singapore

6.6 A 10,000 Inference/s Vision Chip with SPAD Imaging and Reconfigurable Intelligent Spike-Based Vision Processor
 X. Yang*1 , F. Lei*1 , N. Tian*1 , C. Shi2 , Z. Wang1 , S. Yu1 , R. Dou1 , P. Feng1 , N. Qi1 , J. Liu1 , N. Wu1 , L. Liu1
 1 Chinese Academy of Sciences, Beijing, China 2 Chongqing University, Chongqing, China
 *Equally Credited Authors (ECAs)

6.7 A 160×120 Flash LiDAR Sensor with Fully Analog-Assisted In-Pixel Histogramming TDC Based on Self-Referenced SAR ADC
 S-H. Han1 , S. Park1 , J-H. Chun2,3, J. Choi2,3, S-J. Kim1
 1 Ulsan National Institute of Science and Technology, Ulsan, Korea
 2 Sungkyunkwan University, Suwon, Korea
 3 SolidVue, Seongnam, Korea

6.8 A 256×192-Pixel 30fps Automotive Direct Time-of-Flight LiDAR Using 8× Current-Integrating-Based TIA, Hybrid Pulse Position/Width Converter, and Intensity/CNN-Guided 3D Inpainting
 C. Zou1 , Y. Ou1 , Y. Zhu1 , R. P. Martins1,2, C-H. Chan1 , M. Zhang1
 1 University of Macau, Macau, China
 2 Instituto Superior Tecnico/University of Lisboa, Lisbon, Portugal

6.9 A 0.35V 0.367TOPS/W Image Sensor with 3-Layer Optical-Electronic Hybrid Convolutional Neural Network
 X. Wang*, Z. Huang*, T. Liu, W. Shi, H. Chen, M. Zhang
 Tsinghua University, Beijing, China
 *Equally Credited Authors (ECAs)

6.10 A 1/1.56-inch 50Mpixel CMOS Image Sensor with 0.5μm pitch Quad Photodiode Separated by Front Deep Trench Isolation
 D. Kim, K. Cho, H-C. Ji, M. Kim, J. Kim, T. Kim, S. Seo, D. Im, Y-N. Lee, J. Choi, S. Yoon, I. Noh, J. Kim, K. J. Lee, H. Jung, J. Shin, H. Hur, K. E. Chang, I. Cho, K. Woo, B. S. Moon, J. Kim, Y. Ahn, D. Sim, S. Park, W. Lee, K. Kim, C. K. Chang, H. Yoon, J. Kim, S-I. Kim, H. Kim, C-R. Moon, J. Song
 Samsung Semiconductor, Hwaseong, Korea

6.11 A 320x240 CMOS LiDAR Sensor with 6-Transistor nMOS-Only SPAD Analog Front-End and Area-Efficient Priority Histogram Memory
 M. Kim*1 , H. Seo*1,2, S. Kim1 , J-H. Chun1,2, S-J. Kim3 , J. Choi*1,2
 1 Sungkyunkwan University, Suwon, Korea
 2 SolidVue, Seongnam, Korea
 3 Ulsan National Institute of Science and Technology, Ulsan, Korea
 *Equally Credited Authors (ECAs)
 

Imaging papers in other sessions: 

17.3 A Fully Wireless, Miniaturized, Multicolor Fluorescence Image Sensor Implant for Real-Time Monitoring in Cancer Therapy
 R. Rabbani*1 , M. Roschelle*1 , S. Gweon1 , R. Kumar1 , A. Vercruysse1 , N. W. Cho2 , M. H. Spitzer2 , A. M. Niknejad1 , V. M. Stojanovic1 , M. Anwar1,2
 1 University of California, Berkeley, CA
 2 University of California, San Francisco, CA
 *Equally Credited Authors (ECAs)

33.10 A 2.7ps-ToF-Resolution and 12.5mW Frequency-Domain NIRS Readout IC with Dynamic Light Sensing Frontend and Cross-Coupling-Free Inter-Stabilized Data Converter
 Z. Ma1 , Y. Lin1 , C. Chen1 , X. Qi1 , Y. Li1 , K-T. Tang2 , F. Wang3 , T. Zhang4 , G. Wang1 , J. Zhao1
 1 Shanghai Jiao Tong University, Shanghai, China
 2 National Tsing Hua University, Hsinchu, Taiwan
 3 Shanghai United Imaging Microelectronics Technology, Shanghai, China
 4 Shanghai Mental Health Center, Shanghai, China

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Miyauchi et al from Brillnics and  Tohoku University published a paper titled "Analysis of Light Intensity and Charge Holding Time Dependence of Pinned Photodiode Full Well Capacity" in the IISW 2023 special issue of the journal Sensors.

Abstract
In this paper, the light intensity and charge holding time dependence of pinned photodiode (PD) full well capacity (FWC) are studied for our pixel structure with a buried overflow path under the transfer gate. The formulae for PDFWC derived from a simple analytical model show that the relation between light intensity and PDFWC is logarithmic because PDFWC is determined by the balance between the photo-generated current and overflow current under the bright condition. Furthermore, with using pulsed light before a charge holding operation in PD, the accumulated charges in PD decrease with the holding time due to the overflow current, and finally, it reaches equilibrium PDFWC. The analytical model has been successfully validated by the technology computer-aided design (TCAD) device simulation and actual device measurement.

Open access: https://doi.org/10.3390/s23218847

Figure 1. Measured dynamic behaviors of PPD.

Figure 2. Pixel schematic and pulse timing for characterization.

Figure 3. PD cross-section and potential of the buried overflow path.

Figure 4. Potential and charge distribution changes from PD reset to PD saturation.

Figure 7. Potential and charge distribution changes from PD saturation to equilibrium PDFWC.

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Link: https://www.sony.com/lr/electronics/interchangeable-lens-cameras/ilce-9m3

Sony recently announced a full-frame global shutter camera which was featured in several press articles below:

PetaPixel https://petapixel.com/2023/11/07/sony-announces-a9-iii-worlds-first-global-sensor-full-frame-camera/

DPReview https://www.dpreview.com/news/7271416294/sony-announces-a9-iii-world-s-first-full-frame-global-shutter-camera

The Verge https://www.theverge.com/2023/11/7/23950504/sony-a9-iii-mirrorless-camera-global-shutter-price-release

From Sony's official webpage:

[This camera uses the] Newly developed full-frame stacked 24.6 MP Exmor RS™ image sensor with global shutter [...] a stacked CMOS architecture and integral memory [...] advanced A/D conversion enable high-speed processing to proceed with minimal delay. [AI features are implemented using the] BIONZ XR™ processing engine. With up to eight times more processing power than previous versions, the BIONZ XR image processing engine minimises processing latency [...] It's able to process the high volume of data generated by the newly developed Exmor RS image sensor in real-time, even while shooting continuous bursts at up to 120 fps, and it can capture high-quality 14-bit RAW images in all still shooting modes. [...] [The] α9 III can use subject form data to accurately recognise movement. Human pose estimation technology recognises not just eyes but also body and head position with high precision. 

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The deadline for the 2024 ISSW on December 8, 2023 is fast approaching! Paper submission portal is now open!

The 2024 International SPAD Sensor Workshop will be held from 4-6 June 2024 in Trento, Italy.

Paper submission

Workshop papers must be submitted online on Microsoft CMT. Click here to be redirected to the submission website. You may need to register first, then search for the "2024 International SPAD Sensor Workshop" within the list of conferences using the dedicated search bar.

Paper format

Kindly take note that the ISSW employs a single-stage submission process, necessitating the submission of camera-ready papers. Each submission should comprise a 1000-character abstract and a 3-page paper, equivalent to 1 page of text and 2 pages of images. The submission must include the authors' name(s) and affiliation, mailing address, telephone, and email address. The formatting can adhere to either a style that integrates text and figures, akin to the standard IEEE format, or a structure with a page of text followed by figures, mirroring the format of the International Solid-State Circuits Conference (ISSCC) or the IEEE Symposium on VLSI Technology and Circuits. Examples illustrating these formats can be accessed in the online database of the International Image Sensor Society.

The deadline for paper submission is 23:59 CET, Friday December 8th, 2023.

Papers will be considered on the basis of originality and quality. High quality papers on work in progress are also welcome. Papers will be reviewed confidentially by the Technical Program Committee. Accepted papers will be made freely available for download from the International Image Sensor Society website. Please note that no major modifications are allowed. Authors will be notified of the acceptance of their abstract & posters at the latest by Wednesday Jan 31st, 2024.
 
Poster submission 

In addition to talks, we wish to offer all graduate students, post-docs, and early-career researchers an opportunity to present a poster on their research projects or other research relevant to the workshop topics . If you wish to take up this opportunity, please submit a 1000-character abstract and a 1-page description (including figures) of the proposed research activity, along with authors’ name(s) and affiliation, mailing address, telephone, and e-mail address.

The deadline for poster submission is 23:59 CET, Friday December 8th, 2023.

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Li et al. present a new THz imaging technique for defect detection in a recent paper in the journal Nature Communications. The paper is titled "Rapid sensing of hidden objects and defects using a single-pixel diffractive terahertz sensor".

Abstract: Terahertz waves offer advantages for nondestructive detection of hidden objects/defects in materials, as they can penetrate most optically-opaque materials. However, existing terahertz inspection systems face throughput and accuracy restrictions due to their limited imaging speed and resolution. Furthermore, machine-vision-based systems using large-pixel-count imaging encounter bottlenecks due to their data storage, transmission and processing requirements. Here, we report a diffractive sensor that rapidly detects hidden defects/objects within a 3D sample using a single-pixel terahertz detector, eliminating sample scanning or image formation/processing. Leveraging deep-learning-optimized diffractive layers, this diffractive sensor can all-optically probe the 3D structural information of samples by outputting a spectrum, directly indicating the presence/absence of hidden structures or defects. We experimentally validated this framework using a single-pixel terahertz time-domain spectroscopy set-up and 3D-printed diffractive layers, successfully detecting unknown hidden defects inside silicon samples. This technique is valuable for applications including security screening, biomedical sensing and industrial quality control. 

Paper (open access): https://www.nature.com/articles/s41467-023-42554-2

News coverage: https://phys.org/news/2023-11-hidden-defects-materials-single-pixel-terahertz.html

CMOS SPAD Sensors for Solid-state LIDAR

 
In the realm of engineering and material science, detecting hidden structures or defects within materials is crucial. Traditional terahertz imaging systems, which rely on the unique property of terahertz waves to penetrate visibly opaque materials, have been developed to reveal the internal structures of various materials of interest.

This capability provides unprecedented advantages in numerous applications for industrial quality control, security screening, biomedicine, and defense. However, most existing terahertz imaging systems have limited throughput and bulky setups, and they need raster scanning to acquire images of the hidden features.

To change this paradigm, researchers at UCLA Samueli School of Engineering and the California NanoSystems Institute developed a unique terahertz sensor that can rapidly detect hidden defects or objects within a target sample volume using a single-pixel spectroscopic terahertz detector.
Instead of the traditional point-by-point scanning and digital image formation-based methods, this sensor inspects the volume of the test sample illuminated with terahertz radiation in a single snapshot, without forming or digitally processing an image of the sample.

Led by Dr. Aydogan Ozcan, the Chancellor's Professor of Electrical & Computer Engineering and Dr. Mona Jarrahi, the Northrop Grumman Endowed Chair at UCLA, this sensor serves as an all-optical processor, adept at searching for and classifying unexpected sources of waves caused by diffraction through hidden defects. The paper is published in the journal Nature Communications.

"It is a shift in how we view and harness terahertz imaging and sensing as we move away from traditional methods toward more efficient, AI-driven, all-optical sensing systems," said Dr. Ozcan, who is also the Associate Director of the California NanoSystems Institute at UCLA.

This new sensor comprises a series of diffractive layers, automatically optimized using deep learning algorithms. Once trained, these layers are transformed into a physical prototype using additive manufacturing approaches such as 3D printing. This allows the system to perform all-optical processing without the burdensome need for raster scanning or digital image capture/processing.

"It is like the sensor has its own built-in intelligence," said Dr. Ozcan, drawing parallels with their previous AI-designed optical neural networks. "Our design comprises several diffractive layers that modify the input terahertz spectrum depending on the presence or absence of hidden structures or defects within materials under test. Think of it as giving our sensor the capability to 'sense and respond' based on what it 'sees' at the speed of light."

To demonstrate their novel concept, the UCLA team fabricated a diffractive terahertz sensor using 3D printing and successfully detected hidden defects in silicon samples. These samples consisted of stacked wafers, with one layer containing defects and the other concealing them. The smart system accurately revealed the presence of unknown hidden defects with various shapes and positions.
The team believes their diffractive defect sensor framework can also work across other wavelengths, such as infrared and X-rays. This versatility heralds a plethora of applications, from manufacturing quality control to security screening and even cultural heritage preservation.

The simplicity, high throughput, and cost-effectiveness of this non-imaging approach promise transformative advances in applications where speed, efficiency, and precision are paramount.

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Oripov et al. from NIST and JPL recently published a paper titled "A superconducting nanowire single-photon camera with 400,000 pixels" in Nature.

Abstract: For the past 50 years, superconducting detectors have offered exceptional sensitivity and speed for detecting faint electromagnetic signals in a wide range of applications. These detectors operate at very low temperatures and generate a minimum of excess noise, making them ideal for testing the non-local nature of reality, investigating dark matter, mapping the early universe and performing quantum computation and communication. Despite their appealing properties, however, there are at present no large-scale superconducting cameras—even the largest demonstrations have never exceeded 20,000 pixels. This is especially true for superconducting nanowire single-photon detectors (SNSPDs). These detectors have been demonstrated with system detection efficiencies of 98.0%, sub-3-ps timing jitter, sensitivity from the ultraviolet to the mid-infrared and microhertz dark-count rates, but have never achieved an array size larger than a kilopixel. Here we report on the development of a 400,000-pixel SNSPD camera, a factor of 400 improvement over the state of the art. The array spanned an area of 4 × 2.5 mm with 5 × 5-μm resolution, reached unity quantum efficiency at wavelengths of 370 nm and 635 nm, counted at a rate of 1.1 × 105 counts per second (cps) and had a dark-count rate of 1.0 × 10^−4 cps per detector (corresponding to 0.13 cps over the whole array). The imaging area contains no ancillary circuitry and the architecture is scalable well beyond the present demonstration, paving the way for large-format superconducting cameras with near-unity detection efficiencies across a wide range of the electromagnetic spectrum.

Link: https://www.nature.com/articles/s41586-023-06550-2

a, Circuit diagram of a bus and one section of 50 detectors with ancillary readout components. SNSPDs are shown in the grey boxes and all other components are placed outside the imaging area. A photon that arrives at time t0 has its location determined by a time-of-flight readout process based on the time-of-arrival difference t2 − t1. b, Oscilloscope traces from a photon detection showing the arrival of positive (green) and negative (red) pulses at times t1 and t2, respectively.

a, Histogram of the pulse differential time delays Δt = t1 − t2 from the north bus during flood illumination with a Gaussian spot. All 400 detectors resolved clearly, with gaps indicating detectors that were pruned. Inset, zoomed-in region showing that counts from adjacent detectors are easily resolvable and no counts were generated by a pruned detector. b, Plot of raw trow and tcol time delays when flood illuminated at 370 nm. c, Zoomed-in subsection of the array with 25 × 25 detectors. d, Histogram of time delays for a 2 × 2 detector subset with 10-ps bin size showing clear distinguishability between adjacent detectors.

a, Count rate versus optical attenuation for a section of detectors biased at 45 μA per detector. The dashed purple line shows a slope of 1, with deviations from that line at higher rates indicating blocking loss. b, System jitter of a 50-detector section. Detection delay was calculated as the time elapsed between the optical pulse being generated and the detection event being read out.

News coverage: https://www.universetoday.com/163959/a-new-superconducting-camera-can-resolve-single-photons/

A New Superconducting Camera can Resolve Single Photons

Researchers have built a superconducting camera with 400,000 pixels, which is so sensitive it can detect single photons. It comprises a grid of superconducting wires with no resistance until a photon strikes one or more wires. This shuts down the superconductivity in the grid, sending a signal. By combining the locations and intensities of the signals, the camera generates an image.

The researchers who built the camera, from the US National Institute of Standards and Technology (NIST) say the architecture is scalable, and so this current iteration paves the way for even larger-format superconducting cameras that could make detections across a wide range of the electromagnetic spectrum. This would be ideal for astronomical ventures such as imaging faint galaxies or extrasolar planets, as well as biomedical research using near-infrared light to peer into human tissue.

These devices have been possible for decades but with a fraction of the pixel count. This new version has 400 times more pixels than any other device of its type. Previous versions have not been very practical because of the low-quality output.

In the past, it was found to be difficult-to-impossible to chill the camera’s superconducting components – which would be hundreds of thousands of wires – by connecting them each to a cooling system.
According to NIST, researchers Adam McCaughan and Bakhrom Oripov and their collaborators at NASA’s Jet Propulsion Laboratory in Pasadena, California, and the University of Colorado Boulder overcame that obstacle by constructing the wires to form multiple rows and columns, like those in a tic-tac-toe game, where each intersection point is a pixel. Then they combined the signals from many pixels onto just a few room-temperature readout nanowires.

The detectors can discern differences in the arrival time of signals as short as 50 trillionths of a second. They can also detect up to 100,000 photons a second striking the grid.
McCaughan said the readout technology can easily be scaled up for even larger cameras, and predicted that a superconducting single-photon camera with tens or hundreds of millions of pixels could soon be available.

In the meantime, the team plans to improve the sensitivity of their prototype camera so that it can capture virtually every incoming photon. That will enable the camera to tackle quantum imaging techniques that could be a game changer for many fields, including astronomy and medical imaging.

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Robotics Summit & Expo - 1-2 May 2024 - Boston, Massachusetts, USA - Website

CLEO - Congress on Lasers and Electro-Optics  -  5-10 May 2024 - Charlotte, North Carolina, USA - Website

Automate - 6-9 May 2024 - Detroit, Michigan, USA - Website

8th International Conference on Bio-Sensing Technology - 12-15 May 2024 - Seville, Spain - Website

16th Optatec - 14-16 May 2024 - Frankfurt, Germany - Website

The 4th International Electronic Conference on Biosensors - 20-22 May 2024 - Online - Website

Auto-Sens USA - 21-23 May 2024 - Detroit, Michigan, USA - Website

ALLSENSORS 2024 - 26-30 May 2024 - Barcelona, Spain - Website

20th WCNDT - 27-31 May 2024 - Incheon, Korea - Website

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The 2023 workshop on Radiation Effects on Optoelectronic Detectors and Photonics Technologies (RADOPT) will be co-organised by CNES, UJM, SODERN, ISAE-SUPAERO AIRBUS DEFENCE & SPACE, THALES ALENIA SPACE in Touluse, France on November 29 and 30, 2023.

After the success of RADOPT 2021, this second edition of the workshop, will continue to combine and replace two well-known events from the Photonic Devices and IC’s community: the “Optical Fibers in Radiation Environments Days -FMR” and the Radiation effects on Optoelectronic Detectors Workshop, traditionally organized every-two years by the COMET OOE of CNES.

The objective of the workshop is to provide a forum for the presentation and discussion of recent developments regarding the use of optoelectronics and photonics technologies in radiation-rich environments. The workshop also offers the opportunity to highlight future prospects in the fast-moving space, high energy physics, fusion and fission research fields and to enhance exchanges and collaborations between scientists. Participation of young researchers (PhD) is especially encouraged.

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Kim et al. from imec and coauthors from universities in Belgium and Korea recently published a paper titled "A Thin-Film Pinned-Photodiode Imager Pixel with Fully Monolithic Fabrication and beyond 1Me- Full Well Capacity" in MDPI Sensors. This paper describes imec's recent thin film pinned photodiode technology.

Open access paper link: https://www.mdpi.com/1424-8220/23/21/8803

Abstract
Thin-film photodiodes (TFPD) monolithically integrated on the Si Read-Out Integrated Circuitry (ROIC) are promising imaging platforms when beyond-silicon optoelectronic properties are required. Although TFPD device performance has improved significantly, the pixel development has been limited in terms of noise characteristics compared to the Si-based image sensors. Here, a thin-film-based pinned photodiode (TF-PPD) structure is presented, showing reduced kTC noise and dark current, accompanied with a high conversion gain (CG). Indium-gallium-zinc oxide (IGZO) thin-film transistors and quantum dot photodiodes are integrated sequentially on the Si ROIC in a fully monolithic scheme with the introduction of photogate (PG) to achieve PPD operation. This PG brings not only a low noise performance, but also a high full well capacity (FWC) coming from the large capacitance of its metal-oxide-semiconductor (MOS). Hence, the FWC of the pixel is boosted up to 1.37 Me- with a 5 μm pixel pitch, which is 8.3 times larger than the FWC that the TFPD junction capacitor can store. This large FWC, along with the inherent low noise characteristics of the TF-PPD, leads to the three-digit dynamic range (DR) of 100.2 dB. Unlike a Si-based PG pixel, dark current contribution from the depleted semiconductor interfaces is limited, thanks to the wide energy band gap of the IGZO channel material used in this work. We expect that this novel 4 T pixel architecture can accelerate the deployment of monolithic TFPD imaging technology, as it has worked for CMOS Image sensors (CIS).

Figure 1. Pixel cross-section for the monolithic TFPD image sensor (a) 3 T and (b) 4 T (TF-PPD) structure (TCO: transparent conductive oxide, HTL: hole transport layer, PG: photogate, TG: transfer gate, FD: floating diffusion). Electric potential and signal readout configuration for 3 T pixel (c) and for 4 T pixel (d). Pixel circuit diagram for 3 T pixel (e) and for the 4 T pixel (f).

Figure 2. I-V characteristic of QDPD test structure (a) and of IGZO TFT (b), a micrograph of the TF-PPD passive pixel array (c), and its measurement schematic (d). Band diagrams for the PD (e) and PG (f).

Figure 3. Silvaco TCAD simulation results; (a) simulated structure, (b) lateral potential profile along the IGZO layer, and (c) potential profile when TG is turned off and (d) on.

Figure 4. Signal output vs. integration time with different VPG and VTG values with the illumination. Signal curves with the fixed VTG (−1 V), varying VPG (−4~−1 V) (a), the same graphs for the fixed VPG (−2 V), and different VTGs (−6.5~−1 V) (b).

Figure 4. Signal output vs. integration time with different VPG and VTG values with the illumination. Signal curves with the fixed VTG (−1 V), varying VPG (−4~−1 V) (a), the same graphs for the fixed VPG (−2 V), and different VTGs (−6.5~−1 V) (b).

Figure 5. (a) Pixel output vs. integration time for different pixel pitches. (b) FWC comparison between estimation and measurement.

Figure 6. FWC comparison by different pixel fill factors. Pixel schematics for different shapes (a), and FWC by different pixel shapes and pitches (b).

Figure 7. Potential diagram describing FWC increase by the larger VPG (a), and FWC vs. VPG (b).

Figure 8. Passive pixel dark current (a) and Arrhenius plots (b) for the QDPD test structure and the passive pixel.

Figure 9. FWC vs. pixel area. A guideline showing the FWC density per unit area for this work (blue) and a trend line for the most of CISs (red).

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SPIE Photonics Europe - 7-11 Apr 2024 - Strasbourg, France - Website

Position Sensitive Neutron Detectors (PSND 24) - 8-11 Apr 2024 - Oxford, UK - Website

IEEE Silicon Photonics Conference - 15-18 April 2024 - Hilton Tokyo Bay, Japan - Website

Compound Semiconductor International Conference -  16-17 Apr 2024 - Brussels, Belgium - Website

IEEE Custom Integrated Circuits Conference (CICC) - 21-24 Apr 2024 - Denver, Colorado, USA - Website

2024 MRS Spring Meeting & Exhibit - 22-26 Apr 2024 - Seattle, Washington, USA - Website

SPIE Defense and Commercial Sensing - 23-25 Apr 2024 - National Harbor, Maryland, USA - Website

SPIE Future Sensing Technologies  -  23-25 Apr 2024 - Yokohama, Japan - Website

OPIE ’24 (OPTICS & PHOTONICS International Exhibition 2024) - 24-26 Apr 2024 - Yokohama, Japan - Website

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Full article: https://www.eetimes.eu/imec-taps-pinned-photodiode-to-build-a-better-swir-sensor/

Imec Taps Pinned Photodiode to Build a Better SWIR Sensor

‘Monolithic hybrid’ prototype integrates PPD into the TFT structure to lower the cost of light detection in the nonvisible range, with improved noise performance. 

Silicon-based image sensors can detect light within a limited range of wavelengths and thus have limitations in applications like automotive and medical imaging. Sensors that can capture light beyond the visible range, such as short-wave infrared (SWIR), can be built using III-V materials, which combine such elements as gallium, indium, aluminum and phosphorous. But while those sensors perform well, their manufacture requires a high degree of precision and control, increasing their cost.

Research into less expensive alternatives has yielded thin-film absorbers such as quantum-dot (QD) and other organic photodiode (OPD) materials that are compatible with the CMOS readout circuits found in electronic devices, an advantage that has boosted their adoption for IR detection. But thin-film absorbers exhibit higher levels of noise when capturing IR light, resulting in lower image quality. They are also known to have lower sensitivity to IR.

The challenge, then, is to design a cost-effective image sensor that uses thin-film absorbers but offers better noise performance. Imec has taken aim at the problem by revisiting a technology that was first used in the 1980s to improve noise in early CMOS image sensors: the pinned photodiode (PPD).
The PPD structure’s ability to completely remove electrical charges before starting a new capture cycle makes it an efficient approach, as the sensor can reset without unwanted background noise (kTC noise) or any lingering influence from the previous image frame. PPDs quickly became the go-to choice for consumer-grade silicon-based image sensors. Their low noise and high power efficiency made them a favorite among camera manufacturers.

Researchers at imec integrated a PPD structure into thin-film–transistor (TFT) image sensors to yield a hybrid prototype. The sensor structure also uses imec’s proprietary indium gallium zinc oxide (IGZO) technology for electron transport.

“You can call such systems ‘monolithic hybrid’ sensors, where the photodiode is not a part of the CMOS circuit [as in CMOS image sensors, in which silicon is used for light absorption], but is formed with another material as the photoactive layer,” Pawel Malinowski, Pixel Innovations program manager at imec, told EE Times Europe. “The spectrum this photodiode captures is something separate … By introducing an additional thin-film transistor in between, it enables separation of the storage and readout nodes, making it possible to fully deplete the photodiode and transfer all charges to the readout, [thereby] preventing the generation of kTC noise and reducing image lag.”

Unlike the conventional thin-film-based pixel architecture, imec’s TFT hybrid PPD structure introduces a separate thin-film transistor (TFT) to the design, which acts as a transfer gate and a photogate—in other words, it functions as a middleman. Here, imec’s IGZO technology serves as an effective electron transport layer, as it has higher electron mobility. Also acting as the gate dielectric, it contributes to the performance of the sensor by controlling the flow of charges and enhancing absorption characteristics.
With the new elements strategically placed within the traditional PDD structure, the prototype 4T image sensor showed a low readout noise of 6.1e-, compared to >100e- for the conventional 3T sensor, demonstrating its superior noise performance, imec stated. Because of IGZO’s large bandgap, the TFT hybrid PPD structure also entails lower dark current than traditional CMOS image sensors. This means the image sensor can capture infrared images with less noise, less distortion or interference and more accuracy and detail, according to imec

Figure 1: Top (a) and cross-sectional (b) view of structure of TF-PPD pixels

By using thin-film absorbers, imec’s prototype image sensor can detect at SWIR wavelengths and beyond, imec said. Image sensors operating in the near-infrared range are already used in automotive applications and consumer apps like iPhone Face ID. Going to longer wavelengths, such as SWIR, enables better transmission through OLED displays, which leads to better “hiding” of the components behind the screen and reduction of the “notch.”

Malinowski said, “In automotive, going to longer wavelengths can enable better visibility in adverse weather conditions, such as visibility through fog, smoke or clouds, [and achieve] increased contrast of some materials that are hard to distinguish against a dark background—for example, high contrast of textiles against poorly illuminated, shaded places.” Using the thin-film image sensor could make intruder detection and monitoring in dark conditions more effective and cost-efficient. It could also aid in medical imaging, which uses SWIR to study veins, blood flow and tissue properties.

Looking ahead, imec plans to diversify the thin-film photodiodes that can be used in the proposed architecture. The current research has tested for two types of photodiodes: a photodiode sensitive to near-infrared and a QD photodiode sensitive to SWIR.

“Current developments were focused on realizing a proof-of-concept device, with many design and process variations to arrive at a generic module,” Malinowski said. “Further steps include testing the PPD structure with different photodiodes—for example, other OPD and QDPD versions. Furthermore, next-generation devices are planned to focus on a more specific use case, with a custom readout suitable for a particular application.

“SWIR imaging with quantum dots is one of the avenues for further developments and is also a topic with high interest from the imaging community,” Malinowski added. “We are open to collaborations with industrial players to explore and mature this exciting sensor technology.”

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Press release: https://www.onsemi.com/company/news-media/press-announcements/en/onsemi-introduces-lowest-power-image-sensor-family-for-smart-home-and-office

onsemi Introduces Lowest Power Image Sensor Family for Smart Home and Office 

Hyperlux LP Image Sensors can extend battery life by up to 40%¹

What's New: Today onsemi introduced the Hyperlux LP image sensor family ideally suited for industrial and commercial cameras such as smart doorbells, security cameras, AR/VR/XR headsets, machine vision and video conferencing. These 1.4 µm pixel sensors deliver industry-leading image quality and low power consumption while maximizing performance to capture crisp, vibrant images even in difficult lighting conditions.

The product family also features a stacked architecture design that minimizes its footprint and at its smallest approaches the size of a grain of rice, making it ideal for devices where size is critical. Depending on the use case, customers can choose between the 5-megapixel AR0544, the 8-megapixel AR0830 or the 20-megapixel AR2020.

Why It Matters: Home and business owners continue to choose cameras to protect themselves more than any other security measure, with the market expected to triple by the end of the decade.² As a result, consumers are demanding devices that offer better image quality, reliability and longer battery life to improve the overall user experience.

With the image sensors, cameras can deliver clearer images and more accurate object detection even in harsh weather and lighting conditions. Additionally, these cameras are often placed in locations that can be difficult to access to replace or recharge batteries, making low power consumption a critical feature.

How It Works: The Hyperlux LP family is packed with features and proprietary technologies that optimize performance and resolution including:

•  Wake on Motion – Enables the sensors to operate in a low-power mode that draws a fraction of the power needed in the full-performance mode. Once the sensor detects movement, it moves to a higher performance state in less time than it takes to snap a photo.
•  Smart ROI – Delivers more than one region of interest (ROI) to give a context view of the scene at reduced bandwidth and a separate ROI in original detail.
•  Near-Infrared (NIR) Performance – Delivers superior image quality due to the innovative silicon design and pixel architecture, with minimal supplemental lighting.
•  Low Power – Reduces thermal noise which negatively impacts image quality and eliminates the need for heat sinks, reducing the overall cost of the vision system.

Supporting Quotes:
“By leveraging our superior analog design and pixel architecture, our sensors elevate the two most important elements people consider when buying a device, picture quality and battery life. Our new image sensor family delivers performance that matters with a significantly increased battery life and exquisite, highly detailed images,” said Ross Jatou, senior vice president and general manager, Intelligent Sensing Group, onsemi.

In addition to smart home devices, one of the other applications the Hyperlux LP family can improve is the office meeting experience with more intuitive, seamless videoconferencing solutions.
“Our video collaboration solutions require high-quality image sensors that bring together multiple factors for the best user experience. The superior optical performance, innovative features and extremely low power consumption of the Hyperlux LP image sensors enable us to deliver a completely immersive virtual meeting experience in highly intelligent and optimized videoconferencing systems,” said Ashish Thanawala, Sr. Director of Systems Engineering, Owl Labs.

What's Next: The Hyperlux LP Image Sensor Family will be available in the fourth quarter of 2023.

More Information:
 Learn more about the AR2020, the AR0830 and the AR0544.
 Read the blog: A Closer Look - Hyperlux LP Image Sensors

¹ Based on internal tests conducted under specific conditions. Actual results may vary based on device, usage patterns, and other external factors.
² Status of the CMOS Image Sensor Industry, Yole Intelligence Report, 2023.

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In this invited talk at ESSCIRC 2023, Dr. Pellegrini shares her insights on circuits and sensor design through her research career at Politecnico Milano, Heriot Watt and now at STMicro. The lecture covers basics of LiDAR and SPAD sensors, and various design challenges such as low signal strength and background illumination.

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Imaging Time: Cameras for the Fourth Dimension

Abstract
Time is often considered as the fourth dimension, along with the length, width and depth that form the fabric of space-time. Conventional cameras observe only two of those dimensions inferring depth from spatial cues and record time only coarsely relative to many fast phenomena in the natural world. In this talk, I will introduce the concept of time cameras, devices based on single photon avalanche diodes (SPADs) that can record the time dimension of a scene at the picosecond scales commensurate with the speed of light. This talk will chart 2 decades of my research into these devices which have seen their transformation from a research curiosity to a mainstream semiconductor technology with billions of SPAD devices in consumer use in mobile phones for depth sensing autofocus-assist. We will illustrate the talk with videos and demonstrations of ultrafast SPAD cameras developed at the University of Edinburgh. I am proud that my group’s research maintains the University position at forefront of imaging technology which has transformed our lives, seeing the transition from chemical film to digital cameras, the omnipresence of camera phones and video meetings. In the near future, SPAD-based time cameras can also be expected to play a major societal role, within optical radars (LIDARs) for robotic vision and driverless cars, surgical guidance for cancer and perhaps even to add two further dimensions to the phone camera in your pocket!

Biography
Robert K. Henderson is a Professor of Electronic Imaging in the School of Engineering at the University of Edinburgh. He obtained his PhD in 1990 from the University of Glasgow. From 1991, he was a research engineer at the Swiss Centre for Microelectronics, Neuchatel, Switzerland. In 1996, he was appointed senior VLSI engineer at VLSI Vision Ltd, Edinburgh, UK where he worked on the world’s first single chip video camera. From 2000, as principal VLSI engineer in STMicroelectronics Imaging Division he developed image sensors for mobile phone applications. He joined University of Edinburgh in 2005, designing the first SPAD image sensors in nanometer CMOS technologies in the MegaFrame and SPADnet EU projects. This research activity led to the first volume SPAD time-of-flight products in 2013 in the form of STMicroelectronics FlightSense series, which perform an autofocus-assist now present in over 1 billion smartphones. He benefits from a long-term research partnership with STMicroelectronics in which he explores medical, scientific and high speed imaging applications of SPAD technology. In 2014, he was awarded a prestigious ERC advanced fellowship. He is an advisor to Ouster Automotive and a Fellow of the IEEE and the Royal Society of Edinburgh.

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