Research

19 pages, 4272 KiB

Open AccessArticle

Surface Passivation by Quantum Exclusion: On the Quantum Efficiency and Stability of Delta-Doped CCDs and CMOS Image Sensors in Space

by Michael E. Hoenk, April D. Jewell, Gillian Kyne, John Hennessy, Todd Jones, Charles Shapiro, Nathan Bush, Shouleh Nikzad, David Morris, Katherine Lawrie and Jesper Skottfelt

Sensors 2023, 23(24), 9857; https://doi.org/10.3390/s23249857 - 15 Dec 2023

Viewed by 698

Abstract

Radiation-induced damage and instabilities in back-illuminated silicon detectors have proved to be challenging in multiple NASA and commercial applications. In this paper, we develop a model of detector quantum efficiency (QE) as a function of Si–SiO₂ interface and oxide trap densities to [...] Read more.

Radiation-induced damage and instabilities in back-illuminated silicon detectors have proved to be challenging in multiple NASA and commercial applications. In this paper, we develop a model of detector quantum efficiency (QE) as a function of Si–SiO₂ interface and oxide trap densities to analyze the performance of silicon detectors and explore the requirements for stable, radiation-hardened surface passivation. By analyzing QE data acquired before, during, and after, exposure to damaging UV radiation, we explore the physical and chemical mechanisms underlying UV-induced surface damage, variable surface charge, QE, and stability in ion-implanted and delta-doped detectors. Delta-doped CCD and CMOS image sensors are shown to be uniquely hardened against surface damage caused by ionizing radiation, enabling the stability and photometric accuracy required by NASA for exoplanet science and time domain astronomy. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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10 pages, 2691 KiB

Open AccessCommunication

A 0.5 MP, 3D-Stacked, Voltage-Domain Global Shutter Image Sensor with NIR QE Enhancement, Event Detection Modes, and 90 dB Dynamic Range

by Adi Xhakoni

Sensors 2023, 23(23), 9448; https://doi.org/10.3390/s23239448 - 27 Nov 2023

Viewed by 921

Abstract

We introduce a compact voltage-domain global shutter CMOS image sensor for a wide range of applications including consumer, IoT, and industrial applications. With 0.5 MP and 2.79 µm pixels packed in a die size of only 2.3 mm × 2.8 mm, the sensor [...] Read more.

We introduce a compact voltage-domain global shutter CMOS image sensor for a wide range of applications including consumer, IoT, and industrial applications. With 0.5 MP and 2.79 µm pixels packed in a die size of only 2.3 mm × 2.8 mm, the sensor achieves more than 92% quantum efficiency (QE) in the visible wavelength and more than 36% at near-infrared (940 nm) all while drawing a mere 20 mW at a 10-bit, 30-frame-per-second operational mode. In this article, we focus on the architecture of the sensor and the design challenges encountered to fit all the necessary circuitry in such a limited footprint. Moreover, we detail the new solutions we have developed to meet the demanding specifications of low-power operation and high dynamic range (HDR). Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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22 pages, 6800 KiB

Open AccessArticle

First-Arrival Differential Counting for SPAD Array Design

by Mel White, Tianyi Zhang, Akshat Dave, Shahaboddin Ghajari, Alyosha Molnar and Ashok Veeraraghavan

Sensors 2023, 23(23), 9445; https://doi.org/10.3390/s23239445 - 27 Nov 2023

Viewed by 900

Abstract

We present a novel architecture for the design of single-photon detecting arrays that captures relative intensity or timing information from a scene, rather than absolute. The proposed method for capturing relative information between pixels or groups of pixels requires very little circuitry, and [...] Read more.

We present a novel architecture for the design of single-photon detecting arrays that captures relative intensity or timing information from a scene, rather than absolute. The proposed method for capturing relative information between pixels or groups of pixels requires very little circuitry, and thus allows for a significantly higher pixel packing factor than is possible with per-pixel TDC approaches. The inherently compressive nature of the differential measurements also reduces data throughput and lends itself to physical implementations of compressed sensing, such as Haar wavelets. We demonstrate this technique for HDR imaging and LiDAR, and describe possible future applications. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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13 pages, 6394 KiB

Open AccessArticle

Depth Quality Improvement with a 607 MHz Time-Compressive Computational Pseudo-dToF CMOS Image Sensor

by Anh Ngoc Pham, Thoriq Ibrahim, Keita Yasutomi, Shoji Kawahito, Hajime Nagahara and Keiichiro Kagawa

Sensors 2023, 23(23), 9332; https://doi.org/10.3390/s23239332 - 22 Nov 2023

Viewed by 1028

Abstract

In this paper, we present a prototype pseudo-direct time-of-flight (ToF) CMOS image sensor, achieving high distance accuracy, precision, and robustness to multipath interference. An indirect ToF (iToF)-based image sensor, which enables high spatial resolution, is used to acquire temporal compressed signals in the [...] Read more.

In this paper, we present a prototype pseudo-direct time-of-flight (ToF) CMOS image sensor, achieving high distance accuracy, precision, and robustness to multipath interference. An indirect ToF (iToF)-based image sensor, which enables high spatial resolution, is used to acquire temporal compressed signals in the charge domain. Whole received light waveforms, like those acquired with conventional direct ToF (dToF) image sensors, can be obtained after image reconstruction based on compressive sensing. Therefore, this method has the advantages of both dToF and iToF depth image sensors, such as high resolution, high accuracy, immunity to multipath interference, and the absence of motion artifacts. Additionally, two approaches to refine the depth resolution are explained: (1) the introduction of a sub-time window; and (2) oversampling in image reconstruction and quadratic fitting in the depth calculation. Experimental results show the separation of two reflections 40 cm apart under multipath interference conditions and a significant improvement in distance precision down to around 1 cm. Point cloud map videos demonstrate the improvements in depth resolution and accuracy. These results suggest that the proposed method could be a promising approach for virtually implementing dToF imaging suitable for challenging environments with multipath interference. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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16 pages, 7353 KiB

Open AccessArticle

Design and Characterization of 5 μm Pitch InGaAs Photodiodes Using In Situ Doping and Shallow Mesa Architecture for SWIR Sensing

by Jules Tillement, Cyril Cervera, Jacques Baylet, Christophe Jany, François Nardelli, Thomas Di Rito, Sylvain Georges, Gabriel Mugny, Olivier Saxod, Olivier Gravrand, Thierry Baron, François Roy and Frédéric Boeuf

Sensors 2023, 23(22), 9219; https://doi.org/10.3390/s23229219 - 16 Nov 2023

Viewed by 1524

Abstract

This paper presents the complete design, fabrication, and characterization of a shallow-mesa photodiode for short-wave infra-red (SWIR) sensing. We characterized and demonstrated photodiodes collecting 1.55 μm photons with a pixel pitch as small as 3 μm. For a 5 μm pixel pitch photodiode, [...] Read more.

This paper presents the complete design, fabrication, and characterization of a shallow-mesa photodiode for short-wave infra-red (SWIR) sensing. We characterized and demonstrated photodiodes collecting 1.55 μm photons with a pixel pitch as small as 3 μm. For a 5 μm pixel pitch photodiode, we measured the external quantum efficiency reaching as high as 54%. With substrate removal and an ideal anti-reflective coating, we estimated the internal quantum efficiency as achieving 77% at 1.55 μm. The best measured dark current density reached 5 nA/cm² at −0.1 V and at 23 °C. The main contributors responsible for this dark current were investigated through the study of its evolution with temperature. We also highlight the importance of passivation with a perimetric contribution analysis and the correlation between MIS capacitance characterization and dark current performance. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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10 pages, 8335 KiB

Open AccessArticle

Automotive 2.1 μm Full-Depth Deep Trench Isolation CMOS Image Sensor with a 120 dB Single-Exposure Dynamic Range

by Dongsuk Yoo, Youngtae Jang, Youngchan Kim, Jihun Shin, Kangsun Lee, Seok-Yong Park, Seungho Shin, Hongsuk Lee, Seojoo Kim, Joongseok Park, Cheonho Park, Moosup Lim, Hyungjin Bae, Soeun Park, Minwook Jung, Sungkwan Kim, Shinyeol Choi, Sejun Kim, Jinkyeong Heo, Hojoon Lee, KyungChoon Lee, Youngkyun Jeong, Youngsun Oh, Min-Sun Keel, Bumsuk Kim, Haechang Lee and JungChak Ahn Show full author list Hide full author list

Sensors 2023, 23(22), 9150; https://doi.org/10.3390/s23229150 - 13 Nov 2023

Cited by 2 | Viewed by 1458

Abstract

An automotive 2.1 μm CMOS image sensor has been developed with a full-depth deep trench isolation and an advanced readout circuit technology. To achieve a high dynamic range, we employ a sub-pixel structure featuring a high conversion gain of a large photodiode and [...] Read more.

An automotive 2.1 μm CMOS image sensor has been developed with a full-depth deep trench isolation and an advanced readout circuit technology. To achieve a high dynamic range, we employ a sub-pixel structure featuring a high conversion gain of a large photodiode and a lateral overflow of a small photodiode connected to an in-pixel storage capacitor. With the sensitivity ratio of 10, the expanded dynamic range could reach 120 dB at 85 °C by realizing a low random noise of 0.83 e- and a high overflow capacity of 210 ke-. An over 25 dB signal-to-noise ratio is achieved during HDR image synthesis by increasing the full-well capacity of the small photodiode up to 10,000 e- and suppressing the floating diffusion leakage current at 105 °C. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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15 pages, 9117 KiB

Open AccessArticle

A CMOS Image Sensor Dark Current Compensation Using In-Pixel Temperature Sensors

by Accel Abarca and Albert Theuwissen

Sensors 2023, 23(22), 9109; https://doi.org/10.3390/s23229109 - 10 Nov 2023

Cited by 1 | Viewed by 1416

Abstract

This paper presents a novel technique for dark current compensation of a CMOS image sensor (CIS) by using in-pixel temperature sensors (IPTSs) over a temperature range from −40 °C to 90 °C. The IPTS makes use of the 4T pixel as a temperature [...] Read more.

This paper presents a novel technique for dark current compensation of a CMOS image sensor (CIS) by using in-pixel temperature sensors (IPTSs) over a temperature range from −40 °C to 90 °C. The IPTS makes use of the 4T pixel as a temperature sensor. Thus, the 4T pixel has a double functionality, either as a pixel or as a temperature sensor. Therefore, the dark current compensation can be carried out locally by generating an artificial dark reference frame from the temperature measurements of the IPTSs and the temperature behavior of the dark current (previously calibrated). The artificial dark current frame is subtracted from the actual images to reduce/cancel the dark signal level of the pictures. In a temperature range from −40 °C to 90 °C, results show that the temperature sensors have an average temperature coefficient (TC) of 1.15 mV/°C with an inaccuracy of ±0.55 °C. Parameters such as conversion gain, gain of the amplifier, and ADC performance have been analyzed over temperature. The dark signal can be compensated in the order of 80% in its median value, and the nonuniformity is reduced in the order of 55%. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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24 pages, 13986 KiB

Open AccessArticle

A 3.0 µm Pixels and 1.5 µm Pixels Combined Complementary Metal-Oxide Semiconductor Image Sensor for High Dynamic Range Vision beyond 106 dB

by Satoko Iida, Daisuke Kawamata, Yorito Sakano, Takaya Yamanaka, Shohei Nabeyoshi, Tomohiro Matsuura, Masahiro Toshida, Masahiro Baba, Nobuhiko Fujimori, Adarsh Basavalingappa, Sungin Han, Hidetoshi Katayama and Junichiro Azami

Sensors 2023, 23(21), 8998; https://doi.org/10.3390/s23218998 - 06 Nov 2023

Viewed by 1025

Abstract

We propose a new concept image sensor suitable for viewing and sensing applications. This is a report of a CMOS image sensor with a pixel architecture consisting of a 1.5 μm pixel with four-floating-diffusions-shared pixel structures and a 3.0 μm pixel with an [...] Read more.

We propose a new concept image sensor suitable for viewing and sensing applications. This is a report of a CMOS image sensor with a pixel architecture consisting of a 1.5 μm pixel with four-floating-diffusions-shared pixel structures and a 3.0 μm pixel with an in-pixel capacitor. These pixels are four small quadrate pixels and one big square pixel, also called quadrate–square pixels. They are arranged in a staggered pitch array. The 1.5 μm pixel pitch allows for a resolution high enough to recognize distant road signs. The 3 μm pixel with intra-pixel capacitance provides two types of signal outputs: a low-noise signal with high conversion efficiency and a highly saturated signal output, resulting in a high dynamic range (HDR). Two types of signals with long exposure times are read out from the vertical pixel, and four types of signals are read out from the horizontal pixel. In addition, two signals with short exposure times are read out again from the square pixel. A total of eight different signals are read out. This allows two rows to be read out simultaneously while reducing motion blur. This architecture achieves both an HDR of 106 dB and LED flicker mitigation (LFM), as well as being motion-artifact-free and motion-blur-less. As a result, moving subjects can be accurately recognized and detected with good color reproducibility in any lighting environment. This allows a single sensor to deliver the performance required for viewing and sensing applications. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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0 pages, 9809 KiB

Open AccessArticle

Guided Direct Time-of-Flight Lidar Using Stereo Cameras for Enhanced Laser Power Efficiency

by Filip Taneski, Istvan Gyongy, Tarek Al Abbas and Robert K. Henderson

Sensors 2023, 23(21), 8943; https://doi.org/10.3390/s23218943 - 03 Nov 2023

Viewed by 1023

Abstract

Self-driving vehicles demand efficient and reliable depth-sensing technologies. Lidar, with its capability for long-distance, high-precision measurement, is a crucial component in this pursuit. However, conventional mechanical scanning implementations suffer from reliability, cost, and frame rate limitations. Solid-state lidar solutions have emerged as a [...] Read more.

Self-driving vehicles demand efficient and reliable depth-sensing technologies. Lidar, with its capability for long-distance, high-precision measurement, is a crucial component in this pursuit. However, conventional mechanical scanning implementations suffer from reliability, cost, and frame rate limitations. Solid-state lidar solutions have emerged as a promising alternative, but the vast amount of photon data processed and stored using conventional direct time-of-flight (dToF) prevents long-distance sensing unless power-intensive partial histogram approaches are used. In this paper, we introduce a groundbreaking ‘guided’ dToF approach, harnessing external guidance from other onboard sensors to narrow down the depth search space for a power and data-efficient solution. This approach centers around a dToF sensor in which the exposed time window of independent pixels can be dynamically adjusted. We utilize a 64-by-32 macropixel dToF sensor and a pair of vision cameras to provide the guiding depth estimates. Our demonstrator captures a dynamic outdoor scene at 3 fps with distances up to 75 m. Compared to a conventional full histogram approach, on-chip data is reduced by over twenty times, while the total laser cycles in each frame are reduced by at least six times compared to any partial histogram approach. The capability of guided dToF to mitigate multipath reflections is also demonstrated. For self-driving vehicles where a wealth of sensor data is already available, guided dToF opens new possibilities for efficient solid-state lidar. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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14 pages, 7582 KiB

Open AccessArticle

A 3.06 μm Single-Photon Avalanche Diode Pixel with Embedded Metal Contact and Power Grid on Deep Trench Pixel Isolation for High-Resolution Photon Counting

by Jun Ogi, Fumiaki Sano, Tatsuya Nakata, Yoshiki Kubo, Wataru Onishi, Charith Koswaththage, Takeya Mochizuki, Yoshiaki Tashiro, Kazuki Hizu, Takafumi Takatsuka, Iori Watanabe, Fumihiko Koga, Tomoyuki Hirano and Yusuke Oike

Sensors 2023, 23(21), 8906; https://doi.org/10.3390/s23218906 - 01 Nov 2023

Cited by 1 | Viewed by 1433

Abstract

In this study, a 3.06 μm pitch single-photon avalanche diode (SPAD) pixel with an embedded metal contact and power grid on two-step deep trench isolation in the pixel is presented. The embedded metal contact can suppress edge breakdown and reduce the dark count [...] Read more.

In this study, a 3.06 μm pitch single-photon avalanche diode (SPAD) pixel with an embedded metal contact and power grid on two-step deep trench isolation in the pixel is presented. The embedded metal contact can suppress edge breakdown and reduce the dark count rate to 15.8 cps with the optimized potential design. The embedded metal for the contact is also used as an optical shield and a low crosstalk probability of 0.4% is achieved, while the photon detection efficiency is as high as 57%. In addition, the integration of a power grid and the polysilicon resistor on SPAD pixels can help to reduce the voltage drop in anode power supply and reduce the power consumption with SPAD multiplication, respectively, in a large SPAD pixel array for a high-resolution photon-counting image sensor. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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12 pages, 4414 KiB

Open AccessArticle

Analysis of Light Intensity and Charge Holding Time Dependence of Pinned Photodiode Full Well Capacity

by Ken Miyauchi, Toshiyuki Isozaki, Rimon Ikeno and Junichi Nakamura

Sensors 2023, 23(21), 8847; https://doi.org/10.3390/s23218847 - 31 Oct 2023

Viewed by 1279

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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18 pages, 16777 KiB

Open AccessArticle

A 316MP, 120FPS, High Dynamic Range CMOS Image Sensor for Next Generation Immersive Displays

by Abhinav Agarwal, Jatin Hansrani, Sam Bagwell, Oleksandr Rytov, Varun Shah, Kai Ling Ong, Daniel Van Blerkom, Jonathan Bergey, Neil Kumar, Tim Lu, Deanan DaSilva, Michael Graae and David Dibble

Sensors 2023, 23(20), 8383; https://doi.org/10.3390/s23208383 - 11 Oct 2023

Cited by 1 | Viewed by 5002

Abstract

We present a 2D-stitched, 316MP, 120FPS, high dynamic range CMOS image sensor with 92 CML output ports operating at a cumulative date rate of 515 Gbit/s. The total die size is 9.92 cm × 8.31 cm and the chip is fabricated in a [...] Read more.

We present a 2D-stitched, 316MP, 120FPS, high dynamic range CMOS image sensor with 92 CML output ports operating at a cumulative date rate of 515 Gbit/s. The total die size is 9.92 cm × 8.31 cm and the chip is fabricated in a 65 nm, 4 metal BSI process with an overall power consumption of 23 W. A 4.3 µm dual-gain pixel has a high and low conversion gain full well of 6600e- and 41,000e-, respectively, with a total high gain temporal noise of 1.8e- achieving a composite dynamic range of 87 dB. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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14 pages, 7724 KiB

Open AccessArticle

Random Telegraph Noise Degradation Caused by Hot Carrier Injection in a 0.8 μm-Pitch 8.3Mpixel Stacked CMOS Image Sensor

by Calvin Yi-Ping Chao, Thomas Meng-Hsiu Wu, Shang-Fu Yeh, Chih-Lin Lee, Honyih Tu, Joey Chiao-Yi Huang and Chin-Hao Chang

Sensors 2023, 23(18), 7959; https://doi.org/10.3390/s23187959 - 18 Sep 2023

Viewed by 1388

Abstract

In this work, the degradation of the random telegraph noise (RTN) and the threshold voltage (

V_{t}

) shift of an 8.3Mpixel stacked CMOS image sensor (CIS) under hot carrier injection (HCI) stress are investigated. We report for the first time the [...] Read more.

In this work, the degradation of the random telegraph noise (RTN) and the threshold voltage (

V_{t}

) shift of an 8.3Mpixel stacked CMOS image sensor (CIS) under hot carrier injection (HCI) stress are investigated. We report for the first time the significant statistical differences between these two device aging phenomena. The

V_{t}

shift is relatively uniform among all the devices and gradually evolves over time. By contrast, the RTN degradation is evidently abrupt and random in nature and only happens to a small percentage of devices. The generation of new RTN traps by HCI during times of stress is demonstrated both statistically and on the individual device level. An improved method is developed to identify RTN devices with degenerate amplitude histograms. Full article

(This article belongs to the Special Issue Special Issue on the 2023 International Image Sensor Workshop (IISW2023))

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