SPADs in Globalfoundries' 55nm BCD Process

It appears that Globalfoundries becomes a viable option for SPAD-based sensors. At least, three Globalfoundries' employees are co-authors of the following paper:

IEEE Journal of Selected Topics in Quantum Electronics publishes a paper "Engineering Breakdown Probability Profile for PDP and DCR Optimization in a SPAD Fabricated in a Standard 55nm BCD Process" by Francesco Gramuglia, Pouyan Keshavarzian, Ekin Kizilkan, Claudio Bruschini, Shyue Seng Tan, Michelle Tng, Elgin Quek, Myung-Jae Lee, and Edoardo Charbon from EPFL (Switzerland), Glogalfoundries (Singapore), KIST (Korea).

"In this paper, we present SPADs based on DPW/BNW junctions in a standard Bipolar-CMOS-DMOS (BCD) technology with results comparable to the state-of-the-art in terms of sensitivity and noise in a deep sub-micron process. Technology CAD (TCAD) simulations along with analytical modelling are used to iterate through two versions of the proposed SPAD for improved detection efficiency. The result is an 8.8 um diameter SPAD exhibiting 1.2 cps/um2 DCR at 20C with 7 V excess bias. The improved structure obtains a PDP of 62 % and 4.2% at 530 nm and 940 nm, respectively. Afterpulsing probability is < 1 % and the timing response is 106 ps FWHM when measured with passive quench/recharge using external components."

PAM4 in Image Sensor-based Communication

PAM4 signalling has been adopted in many recent high speed interfaces, such as PCIe 6.0, MIPI A-PHY, Auto-Serdes, and many others. In the following OSA paper, PAM4 is being proposed for image sensor based communication:

"PAM4 rolling-shutter demodulation using a pixel-per-symbol labeling neural network for optical camera communications" by Yun-Shen Lin, Chi-Wai Chow, Yang Liu, Yun-Han Chang, Kun-Hsien Lin, Yi-Chang Wang, and Yi-Yuan Chen from National Yang Ming Chiao Tung University, National Chiao Tung University, and Industrial Technology Research Institute, Taiwan, with Philips Hong Kong.

"The typical optical camera communication (OCC) modulation scheme is based on binary intensity modulation. To increase the transmission data rate, multi-level modulation format is highly desirable. In this work, we bring forward and demonstrate a rolling shutter 4-level pulse amplitude modulation (PAM4) demodulation scheme for OCC systems using pixel-per-symbol labeling neural network (PPSL-NN) for the first time up to the authors’ knowledge. A bit-rate distance product of 28.8 kbit/s • m per color is achieved. The proposed scheme is to calculate and re-sample the pixel-per-symbol (PPS) to make sure the same number of pixels in each PAM4 symbol is corresponding to a label for the neural network. Experiment results reveal that the proposed scheme can efficiently demodulate high speed PAM4 signal in the rolling shutter OCC pattern."

New Imaging Technologies Video

New Imaging Technologies (NIT) presents its SWIR and HDR sensors in this video:

Recently, NIT has been awarded with a large funding program by the French Government for improving and industrializing its in-house hybridization technology, paving the way to very small infrared sensor pitch. The so called NH technology allows to perform a 3D stack of a read out circuit with a photodiode array without using the traditional Indium bump bonding technique. The NH yield is extremely high and with this investment program it is expected to reach pixel pitch of less than 5um.

Galaxycore CEO on Growth of China Semiconductor Industry

PerceptionCoreVision publishes a transcript of Galaxycore CEO Zhao Lixin (Stanly Zhao) talk at the 2nd Shanghai Free Trade Zone Lingang New Area Semiconductor Industry Development Forum held on September 15, 2021. Few quotes:

"China has a lot to do in the development of image sensors. From the perspective of sales volume, Galaxycore plus Omnivision's CIS shipments account for more than 50% of the world; from the perspective of value, Gekewei’s 1 billion plus Howe 2 billion, accounting for about 16% of the global 20 billion CIS market.

I often proudly say that our Galaxycore is good. Why is Galaxycore good? We, Galaxycore, were the largest domestic customer of SMIC, the largest foundry in China in 2007. During the financial crisis in 2008, we placed an order of 100,000 8-inch wafers for SMIC. Of course, we were surpassed by HiSilicon, because HiSilicon was too powerful.

Before that, Galxycore has been the top four customers of SMIC, and we are also the major customers of packaging factories such as Changjiang Electronics, Jingfang and Huatian. Therefore, only after you have a large scale can you promote the national economy and support the development of this industry. Therefore, I put a lot of emphasis on the shipment volume of a wafer, the Internet emphasizes traffic, and semiconductor companies must emphasize the use of silicon wafers. Galaxycore currently ranks among the top three in terms of silicon wafer usage in China.

The second is to focus on high-end, because only ICs on high-end brand mobile phones have sufficient scale and profits. Without profit, there is no way to do high-end R&D. Therefore, to drive the development of the entire industry chain in China, there must be sufficient profits. Just like a company like Huawei, its high-end mobile phone camera supports three world-renowned companies, Sony, Largan and Sunny. So it can feed so many people with a single chip. But if you can't do high-end, it is unlikely to be profitable.

The development of China's semiconductor industry still requires the use of mobile phones to drive our chip design companies. Design companies drive Foundry factories, packaging factories, and then equipment manufacturers and material manufacturers.

Why can Galaxycore do well? Because Galaxycore is unique in process research and development. Therefore, in order to speed up the research and development of high-end products, we must build our own factories to do the research and development of special processes. Now Lingang is a very good place, so we invested 2.2 billion US dollars in Lingang to build a world's most advanced characteristic process line.

Based on this sales data of Galaxycore, I will tell you about our development history. You can see that from 2006 to 2007, it was the research and development period. In 2008, a large number of shipments were made. In 2009, despite the financial crisis, our business doubled.

In 2014, we made about 340 million U.S. dollars. At this time, we were stuck overseas because we couldn't make BSI crafts. Because the neck of BSI was stuck, we couldn't make high-end products. Then we will cooperate with Samsung around 2016 and 2017 to make our BSI products. At this time, the company's performance is developing by leaps and bounds. Last year we approached 1 billion US dollars.

When there is a breakthrough in research and development, this performance is relatively easy to grow rapidly, and the shipment volume is also amazing. We have achieved shipments of nearly 2.4 billion units. With this scale, we will be able to do more high-end designs later."

Samsung 200MP Sensor Video

Samsung publishes a promotional video about its 200MP HP1 sensor:

Dark Current Reduction in Small Pixels

Seoul National University of Science and Technology publishes a MDPI paper "Reduction of Fluorine Diffusion and Improvement of Dark Current Using Carbon Implantation in CMOS Image Sensor" by Su-Young and Sung-Hoon Choa.

"Recently, the demand of a high resolution complementary metal-oxide semiconductor (CMOS) image sensor is dramatically increasing. As the pixel size reduces to submicron, however, the quality of the sensor image decreases. In particular, the dark current can act as a large noise source resulting in reduction of the quality of the sensor image. Fluorine ion implantation was commonly used to improve the dark current by reducing the trap state density. However, the implanted fluorine diffused to the outside of the silicon surface and disappeared after annealing process. In this paper, we analyzed the effects of carbon implantation on the fluorine diffusion and the dark current characteristics of the CMOS image sensor. As the carbon was implanted with dose of 5.0 × 10^14 and 1 × 10^15 ions/cm2 in N+ area of FD region, the retained dose of fluorine was improved by more than 131% and 242%, respectively than no carbon implantation indicating that the higher concentration of the carbon implantation, the higher the retained dose of fluorine after annealing. As the retained fluorine concentration increased, the minority carriers of electrons or holes decreased by more Si-F bond formation, resulting in increasing the sheet resistance. When carbon was implanted with 1.0 × 10^15 ions/cm2, the defective pixel, dark current, transient noise, and flicker were much improved by 25%, 9.4%, 1%, and 28%, respectively compared to no carbon implantation. Therefore, the diffusion of fluorine after annealing could be improved by the carbon implantation leading to improvement of the dark current characteristics."

Event Cameras Literature Review

Hong Kong University of Science and Technology publishes Jianhao JIAO's slides "Literature Review on Event Cameras" based on Zurich University paper "Event-based Vision: A Survey" by Guillermo Gallego, Tobi Delbruck, et al. Few  slides from the presentation:

Melexis Integrates 940nm Bandpass Filter on Top of its iToF Sensor

Melexis has developed a new version of its time-of-flight 3D camera MLX75026 with a fully integrated infrared bandpass (IRBP) filter. By integrating the IRBP, it is no longer required to include a separate IR filter in the lens or sensor assembly. This solution is said to be unique in the industry. It reduces design complexity and cost, while creating more design choice when sourcing a lens.

“An IR filter is mandatory in every ToF application to reduce out-of-band infrared light in the operating environment, which could otherwise lower the dynamic range of the sensor,” explained Gualtiero Bagnuoli, Optical sensors marketing manager at Melexis. “A separate filter adds cost and complexity to a design, but by using the MLX75026 with IRBP filter, engineers can avoid both the cost and complexity, and explore the benefits of time-of-flight sensing more easily.”

The integration of the correct IR bandpass filter is not trivial: the passband must be adapted to the illumination and the filter shall accept light from a wide range of incidence at minimal spectral shift (optically hard filter). This facilitates the usage of ToF-lenses with high apertures (low f-number). Melexis is the only ToF sensor manufacturer currently offering this option, which is now available as a variant of the MLX75026.

MLX75026 with IRBP filter has QVGA (320x240 pixels) resolution with a 1/4 inch optical format and supports 940 nm illumination. Samples of the MLX75026 with IRBP filter are available now.

ST Presents its First iToF Sensor at ESSCIRC

ST has presented its first iToF image sensor at 47th European Solid-State Circuits Conference being held this week in a virtual space:

"4.6μm Low Power Indirect Time-of-Flight Pixel Achieving 88.5% Demodulation Contrast at 200MHz for 0.54MPix Depth Camera"

by Cedric Tubert, Pascal Mellot, Yann Desprez, Céline Mas, Arnaud Authié, Laurent Simony, Grégory Bochet, Stephane Drouard, Jeremie Teyssier, Damien Miclo, Jean-Raphael Bezal, Thibault Augey, Franck Hingant, Thomas Bouchet, Blandine Roig, Aurélien Mazard, Raoul Vergara, Gabriel Mugny, Arnaud Tournier, Frédéric Lalanne, Francois Roy, Boris Rodrigues Goncalves, Matteo Vignetti, Pascal Fonteneau, Vincent Farys, Francois Agut, Joao Miguel Melo Santos, David Hadden, Kevin Channon, Christopher Townsend, Bruce Rae, and Sara Pellegrini.

"In this paper, a 4.3e- RMS low noise 4.6μm Time-of-Flight pixel based on charge domain with kTC noise removal is proposed to enhance the depth camera image quality. The pixel takes advantages of 6μm gradually doped epitaxial layer for 88.5% demodulation contrast at 200MHz and 18.5% QE at 940nm. Buried channel transfer gates are used to enable low capacitive switching and allowing best-in-class 1.4μW/pixel power consumption at 200MHz. The pixel is fully isolated due to deep trench isolation and pixel bulk is biased at several hundreds of mV for ultimate low power Time-of-Flight sensor and system. The paper describes the design of 0.54Mpix camera (672 x 804 pixels) implementing demodulation circuits robust against EMI and multi-devices interferences. The performance of an indirect Time-of-Flight system is demonstrated with 1.0% depth noise under 40kLux at 30fps."

ST kindly sent me a few slides from the presentation:

Other ESSCIRC imaging papers are:

• "Advancements in Indirect Time of Flight Image Sensors in Front Side Illuminated CMOS"
  Markus Dielacher, Martin Flatscher, Reinhard Gabl, Richard Gaggl, Dirk Offenberg, and Jens Prima from Infineon and PMD
  "We will present major advances in Time of Flight image sensors for consumer applications. Several innovative elements integrated into a 130nm front side illumination CMOS node reveal superior sensor performance so far only attributed to much more complex backside illumination technologies. The gate controlled pixels comprising deep trenches, buried mirrors and integrated prisms, reveal high quantum efficiency and modulation transfer function close to the physical pixel size. In-pixel common mode suppression prevents saturation even under backlight conditions. The comprehensive System on Chip integrates high speed ADCs, a flexible phase shifter, as well as current monitoring for laser safety."

• "Dark Count Rate in Single-Photon Avalanche Diodes: Characterization and Modeling Study"
  Mathieu Sicre, Megan Agnew, Christel Buj, Jean Coignus, Dominik Golanski, Rémi Helleboid, Bastien Mamdy, Isobel Nicholson, Sara Pellegrini, Denis Rideau, David Roy, and Francis Calmon from CEA-Leti, INSA Lyon, STMicroelectronics.
  "Dark Count Rate (DCR) in Single-Photon Avalanche Diodes (SPAD) in Complementary Metal-Oxide Semiconductor technology is characterized and analyzed with a comprehensive simulation methodology. Based on a series of measurements of SPAD with various architectures, on an extended range of voltages and temperatures, the DCR measurements are correlated to the spatial localization of traps within the device and their parameters. To this aim, process and electrical simulations using Technology Computer-Aided Design (TCAD) tools are combined with an in-house McIntyre solver to compute the breakdown probability (Pt). The traps are accounted for using thermal SRH carrier generation-recombination mechanism which is coupled with the position-dependent breakdown probability. This rigorous methodology makes it possible to directly compare with DCR measurements, since only generated carriers with a non-negligible avalanche probability are considered."

• "A High-Speed Low-Power Sun Sensor with Solar Cells and Continuous Operation"
  Rubén Gómez-Merchán, María López-Carmona, Juan Antonio Leñero-Bardallo, Ángel Rodríguez-Vázquez from Universidad de Sevilla-IMSE-CNM CSIC, Spain.
  "A novel sun sensor concept is presented. Photodiodes operating as solar cells with continuous operation and dedicated logic to calculate the centroid position are integrated to achieve lower latency and energy consumption. The output data flow is remarkably reduced because the centroid of the illuminated pixels is the only sensor output data. It overcomes conventional digital sun sensors based on Active Pixel Sensor (APS) pixels and Address Event Representation (AER) in terms of latency and power consumption. Its latency is in the order of microseconds with an average power consumption lower than 100 uW. Experimental results are provided and benchmarked."

• "A 0.94-μVrms Input Noise Pixel-Level Continuous Time ΣΔ IADC Interface for THz Sensing"
  Gabriele Quarta, Matteo Perenzoni, Stefano D'Amico from Fondazione Bruno Kessler and Università Del Salento, Italy
  "The goal of this work is the design, realization, and characterization of a pixel-level front-end in 0.15μm CMOS technology, that allows to directly convert in the digital domain the weak output signal from the Field-Effect Transistor (FET) TeraHertz (THz) detector, in a noise-efficient way. The chosen architecture is a Continuous-Time Sigma-Delta Incremental Analog-to-Digital Converter (CT ΣΔ IADC) with a current DAC feedback, chopper technique and digital lock-in modulation. The measured SNR of this interface is 67.45dB, corresponding to an equivalent number of bit (ENOB) of 10.91. The pixel readout area is 0.072mm2, and the power consumption is 65μW from 1.8V supply. The Noise Equivalent Power (NEP) of the THz detector and readout chain is 268pW/√𝐇𝐳. The readout channel Input Referred Noise (IRN) is 1.2μVrms with the FET, and 0.94μVrms for the channel without detector.

• "The Essential Contribution of CMOS Imaging Technologies to Earth Observation Applications"
  Pierre Magnan, ISAE-SUPAERO, France
  "In this paper we discuss how the high performances CMOS imaging process improvements, strongly driven by consumer market’s needs, has allowed this technologies to pop-up in the field of Earth Observation instruments traditionally making use of dedicated Charge Coupled Devices (CCD). After reviewing the various Earth image captures techniques and related sensor architectures, the specific requirements on the sensor process will be examined and it will be shown how modern CMOS imaging process, although developed initially for high volume small pixel pitch application, can efficiently fulfill these needs, even allow new performances level, and thanks to additional features enable new achievements particularly suited to the New Space context."

• "Luximos: a 768x64 900-fps Tileable Pipelined X-Ray CMOS Image Sensor for Dental Imaging with 2.6 LSB/nGy Sensitivity"
  Nicola Massari, Xu Hesong, Alessandro Tarolli, Luca Parmesan, Daniele Perenzoni, Sabrina Colpo, Nicola Fronza, David Stoppa, Matteo Perenzoni, Alfredo Maglione from AdvanSid, FBK, and AMS

• "Comprehensive Modeling and Characterization of Photon Detection Efficiency and Jitter in Advanced SPAD Devices"
  Rémi Helleboid, Denis Rideau, Isobel Nicholson, Norbert Moussy, Olivier Saxod, Marie Basset, Jérémy Grebot, Antonin Zimmerman, Bastien Mamdy, Dominik Golanski, Megan Agnew, Sara Pellegrini, and Mathieu Sicre from CEA-Leti, STMicroelectronics, INRIA

• "High Tuning Range Spiking 1R-1T VO2 Voltage-Controlled Oscillator for Integrated RF and Optical Sensing"
  Teodor Rosca, Fatemeh Qaderi, and Adrian Mihai Ionescu from EPFL
  "In this work we propose and experimentally validate a relaxation oscillator architecture with ultra-high tuning range (higher than 400%, from 5KHz to more than 25kHz when the control voltage is varied from 2.5 to 5V) that exploits the reversible metal-insulator transition in 2-terminal Vanadium Dioxide thin film devices loaded to a MOSFET common source amplifier. We propose and validate an analytical model that connects key output signal metrics to the intrinsic properties of the phase-change VO2 device employed. In addition, we demonstrate RF and optical sensing capabilities, with sensitivities of 4.64 Hz/dBm and 4.23 Hz/mW to RF and Optical Power, respectively."

Silicon Integrated Presents 5um BSI Pixel iToF Sensor, Expects dToF Product till the Year End

Laoyaoba, EET-China, Sohu: Silicon Integrated, also known as Wuhan Juxin Microelectronics and Polycore Microelectronics, presents SIF2610, a VGA iToF sensor based on 5um BSI pixel. This is the company's 2nd generation product with improved resolution, depth accuracy, and ambient light tolerance. Silicon Integrated emphasizes that the sensor is based on its own self-developed IP and know-how accumulated over the years of ToF experience.

"As ToF products with VGA-level resolution have gradually become the security standard for face payment, PolyCore has brought SIF2610, an excellent performance iToF product, to the industry, which will provide services such as 3D face recognition, smart door locks, interactive perception, Applications such as VSLAM have brought a better user experience," Juxin Microelectronics co-founder and CMO Kong Fanxiao said. "We will also launch high-resolution dToF products based on the 3D stacking process within this year to help the application of 3D sensing in AR/VR and automotive lidar applications."

In August 2021, Silicon Integrated completed a series C financing of hundreds of millions of yuan. It includes a strategic investment from the three major mobile phone brands.

Sony Fab 5 Clean Rooms Consume 30% Less Power

Sony publishes its sustainability initiatives with a focus on image sensor production this year:

• "Responsibility" regarding the environment:
  ＜Energy Conservation＞ At the newly constructed Fab 5 within Nagasaki Technology Center, installation of the latest energy-saving technology has resulted in a 30% improvement in the energy efficiency of clean rooms*. Additionally, 70% of the water used on the production lines is collected and reused.
  * Estimate based on data from the Nagasaki Technology Center for the fiscal year ended March 31, 2016 (FY2015).
• ＜Renewable Energy＞ Sony is proceeding with the installation of solar panels at its manufacturing sites in Japan. In addition, Sony Device Technology (Thailand) Co., Ltd. is moving forward with the largest scale installation of solar panels among any facility within the Sony Group. Together with the purchase of Renewable Energy Certificates, the site is expected to run on 100% renewable electricity by the end of the current fiscal year ending March 31, 2022 (FY2021).
• "Contribution" to the environment:
  The "IMX500" intelligent vision sensor developed by Sony Semiconductor Solutions Corporation is equipped with AI processing functionality within the logic chip of the image sensor. This technology is expected to support advancement in areas such as the Internet of Things (IoT). Processing data on the sensor itself, at the edge of edge systems, makes it possible to extract only the required metadata (semantic information). As a result, this technology contributes to a reduction in power consumption by lowering the volume of data sent to and processed within the cloud, while also enhancing latency (response speed) and having positive implications for privacy.
  "IMX500" is being used in trials of solutions addressing social issues such as traffic congestion and accidents in urban areas, and as part of the effort to reduce the energy consumed by air conditioning systems in buildings.