Tuesday, October 12, 2021

ST to Present its Quantum Dot SWIR Sensor at IEDM 2021

IEDM Press Kit shows few figures from STMicro presentation of its quantum dot NIR/SWIR imager paper:

Paper #23.4, “1.62µm Global Shutter Quantum Dot Image Sensor Optimized for Near and Shortwave Infrared,” J.S. Steckel et al, STMicroelectronics

Record Quantum Efficiency for NIR/SWIR Sensors: STMicroelectronics researchers will report a 1.62µm pixel-pitch global shutter sensor for imaging in the near-infrared (NIR) and shortwave infrared (SWIR) regions of the light spectrum. It demonstrated record optical performance: an unprecedented quantum efficiency of >50% and a shutter efficiency of >99.94%. The breakthrough was made possible by use of a novel colloidal PbS quantum dot thin-film technology, and the devices were fabricated on a 300mm manufacturing toolset.

  • The top photo is of a qualification wafer showing (a) elementary quantum film (QF) test structures; (b) pixel matrix test chips; and (c) full image sensor products.
  • Going from left to right in the middle set of images/drawings are a QF photodiode array integrated on top of a CMOS readout IC; the QF photodiode cross-section; and a graphical description of the device stack.
  • At the bottom is an outdoor image taken with the 940nm NIR QF sensor (left) and with a high-end smartphone camera (right). The NIR image shows a significant difference in contrast, and the ability to clearly identify the black electrical wires hidden in the tree leaves, vs. the visible image.


  1. Big breakthrough for the QD image sensor technology! Wafer processing should open up many new applications and create interesting dynamics in the infrared market.

  2. Any one knows the readout noise level please ?

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  4. 1.62um? what is the pixel size from existing SWIR sensor? It seems not much info from competitor
    300mm would mean targeting high volume (low cost?)

    1. What could be the target application?

    2. I always thought the first target application of volume SWIR would be automotive - like this: http://image-sensors-world.blogspot.com/2021/10/artilux-cooperates-with-conti-on-ge-on.html. But here at ST it seems this is something different, right? No word about SPAD, the paper abstract talks about 'global shutter' (which itself is impressive in 1.62u - by far the smallest GS pixel around, right? So we will see a high volume (more volume than automotive, i suppose a smartphone?) application for a global shutter SWIR sensor in 2022. As it was posted in http://image-sensors-world.blogspot.com/2021/10/st-to-start-quantum-dot-image-sensor.html it seems there are still some issues with VCSEL for a type of 'eye safe, no sunlight' application. So maybe the motivation could be to move a feature like face id behind the display? Exciting times for SWIR imaging.

    3. I think it is GS due to the QD acting as a shutter when biased at certain voltages. No pixel storage nodes I suppose. I don't think this competes with GS sensors, more like an access to low cost SWIR. Question is what is the dark current?

  5. How will PbS be compatible with RoHS?

  6. See https://engineering-update.co.uk/2020/01/16/application-for-rohs-exemption-for-pbx-detectors-completed/


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