IISW 2021 Annouces Second Invited Presentation

The second invited paper at the International Image Sensor Workshop to be held on-line in September 2021 is devoted to modern EUV photolithography and presented by Wim Van der Zande from ASML. A quote from the abstract:

"The present generation of ASML machines use EUV, or Extreme Ultraviolet “light”, which is not only absorbed by air, but also when it contacts materials like glass. Therefore it is not possible to use lenses or transparent reticles, which the previous method of photolithography did. The solution to these problems is the use of mirrors and reflective reticles and operate the process in a controlled vacuum. The EUV photons no longer come in contact with air and no longer need to pass through a lens. Reflective reticles are used to replace the traditional reticle.

In order to ensure a fully working chip, accuracy is very important. The accuracy of an ASML machine is measured in nanometers and is called overlay. Beard hair grows up to 10 nanometers per second. In my contribution, I concentrate on the present high volume manufacturing tools operating at EUV wavelengths and will explain the translation of the specifications needed to produce modern chips into the creation of sufficient EUV light, the required quality of the reflective optics and touch on the mechanical requirements of the fast moving reticles and wafers in our tools. Finally, I will make a link to imaging techniques that can be found in our tools as part of performance and operational metrology.

Wim van der Zande, Director of Research, D&E Source Laser."

The first IISW 2021 invited paper has been announced earlier.

200km-Range dToF Camera

Chinese researchers from University of Science and Technology of China at Hefei and Shanghai and Shanghai Research Center for Quantum Sciences publish OSA paper "Single-photon imaging over 200 km" by Zheng-Ping Li, Jun-Tian Ye, Xin Huang, Peng-Yu Jiang, Yuan Cao, Yu Hong, Chao Yu, Jun Zhang, Qiang Zhang, Cheng-Zhi Peng, Feihu Xu, and Jian-Wei Pan.

"Long-range active imaging has widespread applications in remote sensing and target recognition. Single-photon light detection and ranging (lidar) has been shown to have high sensitivity and temporal resolution. On the application front, however, the operating range of practical single-photon lidar systems is limited to about tens of kilometers over the Earth’s atmosphere, mainly due to the weak echo signal mixed with high background noise. Here, we present a compact coaxial single-photon lidar system capable of realizing 3D imaging at up to 201.5 km. It is achieved by using high-efficiency optical devices for collection and detection, and what we believe is a new noise-suppression technique that is efficient for long-range applications. We show that photon-efficient computational algorithms enable accurate 3D imaging over hundreds of kilometers with as few as 0.44 signal photons per pixel. The results represent a significant step toward practical, low-power lidar over extra-long ranges."

Chronoptics iToF Multipath Tutorial

Chronoptics CTO Refael Whyte publishes an article "Multipath Interference in Indirect Time-of-Flight Depth Sensors."

Branching Pixel for 1MP, 2.59Gfps Sensor

MDPI paper "A Pixel Design of a Branching Ultra-Highspeed Image Sensor" by Nguyen Hoai Ngo, Kazuhiro Shimonomura, Taeko Ando, Takayoshi Shimura, Heiji Watanabe, Kohsei Takehara, Anh Quang Nguyen, Edoardo Charbon, and Takeharu Goji Etoh from Ritsumeikan University, Osaka University, Kindai University, Hanoi University of Science and Technology, and EPFL presents a new CCD pixel:

"A burst image sensor named Hanabi, meaning fireworks in Japanese, includes a branching CCD and multiple CMOS readout circuits. The sensor is backside-illuminated with a light/charge guide pipe to minimize the temporal resolution by suppressing the horizontal motion of signal carriers. On the front side, the pixel has a guide gate at the center, branching to six first-branching gates, each bifurcating to second-branching gates, and finally connected to 12 (=6×2) floating diffusions. The signals are either read out after an image capture operation to replay 12 to 48 consecutive images, or continuously transferred to a memory chip stacked on the front side of the sensor chip and converted to digital signals. A CCD burst image sensor enables a noiseless signal transfer from a photodiode to the in-situ storage even at very high frame rates. However, the pixel count conflicts with the frame count due to the large pixel size for the relatively large in-pixel CCD memory elements. A CMOS burst image sensor can use small trench-type capacitors for memory elements, instead of CCD channels. However, the transfer noise from a floating diffusion to the memory element increases in proportion to the square root of the frame rate. The Hanabi chip overcomes the compromise between these pros and cons."

Multi-Tap Pixels: Not Only ToF

Japanese Journal ITE Transactions on Media Technology and Applications publishes an invited paper "Functional Imaging with Multi-tap CMOS Pixels" by Keiichiro Kagawa from Shizuoka University.

"Multi-tap CMOS pixels that are composed of a single photodiode, multiple sets of a charge transfer gate and storage diode, and a draining gate can implement functional imaging. In this paper, imaging systems based on the multi-tap CMOS pixel are categorized into those with synchronized active illuminations and those using coded exposure. Applications for quantitative wide-field imaging based on spatial frequency domain imaging (SFDI) using structured light projection and multi-exposure laser speckle contrast blood flow imaging (MELSCI) utilizing multiple exposure times are shown. The multi-tap CMOS pixel provides additional benefits like suppression of ambient light and motion artifact with SFDI and efficient sampling at a video rate with MELSCI."

In Search for Holy Grail of Color Routers

Jinan University, Guangzhou, China and University of Glasgow, UK, publish arxiv.org paper "Full-color nanorouter for high-resolution imaging" by Mingjie Chen, Long Wen, Dahui Pan, David R. S. Cumming, Xianguang Yang, and Qin Chen.

"Pixel scaling effects have been a major issue for the development of high-resolution color image sensors due to the reduced photoelectric signal and the color crosstalk. Various structural color techniques have been proposed and demonstrated the large freedom in color manipulation by the structure design. However, the optical efficiency and the color distortion limit the practical applications due to its intrinsic filtering mechanism. Instead, on-chip full-color routing is quite charming for improving the signal-to-noise ratio. In this paper, a single-layer quick response code like nanorouter is proposed for the full-color light routing in a pixel level of image sensors. It shows much higher routing efficiency than various planar lens schemes for signal wavelength focusing. Moreover, over 60% signal enhancement with robust polarization insensitivity is obtained in all three primary color bands with a same nanorouter by a multi-objective optimization method. Negligible color distortion is observed from the reconstructed color image. Such a simple nanorouter structure is promising for the development of image sensor, photovoltaics and display."

ON Semi SPAD Evaluation Kit

ON Semi publishes a video demo of its Pandion SPAD evaluation kit:

Pixpolar Announces New MIG Sensor

After a few years hiatus, Pixpolar announces a new MIG sensor on its LinkedIn page:

The company also publishes its new business plan (in Finnish) with more comparisons with other companies and technologies:

Pixpolar's 2014 and 2015 papers explains MIG pixel operation:

Mars Supercam and Its Super-Sensors

The French Space Agency (CNES) has reported the first images obtained on Mars using the Remote Micro-Imager (RMI) of the SuperCam instrument (the French contribution to NASA JPL PERSEVERANCE Rover) during the CNES Press Conference. The instrument provides high resolution (<70 µrad per pixel) color images for planetologists.

The image sensor used is a CMV4000 (4MP, with RGB color filters and microlenses) from AMS CMOSIS qualified by CNES. The French Space Agency started to work on the CMV image sensor family in 2011. Since then, CNES has demonstrated through radiation effect studies and intensive qualification work that using COTS sensors for space scientific missions can be reliable and cost-effective. Especially, the radiation hardness of pinned photodiode, Bayer color filter arrays, and per-pixel microlenses has been found to be compatible with Mars exploration mission requirements.

Cédric Virmontois is in charge of the RMI at CNES. For more than a decade, ISAE-SUPAERO / CNES PhD students have been participating in the fundamental study of radiation effects on CMOS image sensors.

Axcelis Announces Multiple Shipments of High Energy Ion Implanters to Leading CIS Manufacturers

PRNewswire:  Axcelis has shipped multiple Purion VXE high energy systems to leading CMOS image sensor manufacturers. These shipments include a follow on order to the recently closed Purion VXE evaluation. The systems shipped in the first quarter.

EVP of Product Development, Bill Bintz, commented, "Axcelis has created a flexible, highly differentiated high energy product portfolio that is the implant solution of choice for image sensor manufacturers.  These shipments, combined with our recent Purion VXE evaluation closure and Purion XEmax evaluation shipments, enhance our leadership position in this market. The Purion VXE and Purion XEmax were designed specifically to address the exact needs of customers manufacturing image sensors for applications requiring ultra-high energy implants with extremely precise and deep doping profiles."