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.

7 comments:

  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.

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  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?)

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    1. What could be the target application?

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    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.

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    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?

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