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Single-photon avalanche photodiodes in silicon island arrays for 3D integration with microelectronics



In addition to the fact that sensors based on single-photon avalanche photodiodes (SPADs) are found in cutting-edge scientific fields, their use in devices such as the iPhone demonstrates that this technology is becoming less marginal in the consumer market. audience.

Indeed, SPAD-based photodetectors are also used in medical imaging, particle physics, telemetry, 3D camera systems and quantum telecommunication systems. Photodetectors are sensors capable of converting photon energy from light into electrical signals. Silicon photomultipliers (SiPMs) are responsive single-photon solid-state devices based on arrays of SPADs implemented on common silicon substrates. SiPM detectors are used in the instrumentation markets for radiation detection, medical imaging and telecommunications. In addition, SPADs can measure time-of-flight distance, which is useful for Positron Emission Tomography (PET), 3D cameras in the automotive LIDAR sector, and proximity sensors. These detectors are distinguished by their performance because they are photosensitive to the single photon and have a temporal resolution on the time of arrival of the light.


The new concept of this invention of a thin island of silicon containing a SPAD is a new method of integrating SPADs into a detector, which aims to push the limits of the temporal resolution of the detectors. It enables manufacturing on silicon with existing industrial processes at low cost while integrating and miniaturizing the pixel array. The goal with this architecture is to achieve accuracies of 10 picoseconds (10e-12 seconds) for a compact detector, which is equivalent to millimeter precision in terms of distance measurement at the speed of light. This SPAD network integrated in 3D with the electronics aims to optimize the performance of the detector in terms of photosensitivity and precision on the time of arrival of the photon. The thin silicon island concept avoids costly 3D vertical integration technologies, such as the use of "silicon vias", as well as achieving a purely vertical junction profile, which minimizes error on the arrival time of the photon. In summary, the 3 main things that make this invention unique are 1) a front-illuminated detector, 2) no contact via through the silicon structure to interconnect with the electronics, and 3) the SPADs are manufactured with an optoelectronic process with trenches surrounding the SPADs for optical and electronic isolation.


  • There are similar models, but none have the following features in one model:

  • Front-lit architecture

  • 3D integration process without TSV - ie: no vias through the silicon.

  • Opto-electrical isolation trench surrounding each SPAD pixel - design based on a thin and small silicon island with each SPAD.

  • Slim sensor substrate - total vertical integration

  • Crosstalk assessment and minimization

  • Low Cost Manufacturing 

  • Can be integrated in a standardized way on different CMOS technologies: high performance, automotive certified, etc.

  • Fast detection of UV/visible light

  • Direct interconnect layers between SPAD and CMOS


  • This new 3D approach meets the needs of the following industrial and scientific applications:

  • Medical Imaging 

  • Advantages - Reduced doses, more patients per day, real-time 3D reconstruction, better resolution.

  • Particle physics

  • Benefits - On-chip digital approach, large-scale experience: several square meters.

  • Proximity sensors, 3D cameras and automotive LiDAR systems

  • Advantages - Better spatial resolution thanks to time of flight; IR range of the spectrum.

  • Applications for smartphones, for example facial recognition on the iPhone.

  • Quantum telecommunications

  • Advantages - Speed of communication, miniaturization.

  • Markets where single photon detectors are found: 

  • Consumer 3D cameras - ~US$13.8 billion by 2023.

  • Automotive LiDAR - ~$4.1 billion by 2026.

  • Medical Imaging - ~$35 billion by 2022.

  • Solid State Medical Sensors - ~$350M by 2022.

  • Quantum cryptography - ~$0.94 billion by 2022.



TRL 4-5

  • Demonstration of the manufacture of the SPAD on an industrial production line.

  • The optimization of the prototype continues iteratively with the objectives of low cost, high yields and increased efficiency of detection (in particular of UV radiation).


  • Patent pending.


Development partners. Investments. Licenses.

Project Director: François Nadeau

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