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."