Sunday, January 05, 2020

IEDM 2019: Sony SWIR Imager

Sony IEDM paper "High-definition Visible-SWIR InGaAs Image Sensor using Cu-Cu Bonding of III-V to Silicon Wafer" by S. Manda, R. Matsumoto, S. Saito, S. Maruyama, H. Minari, T. Hirano, T. Takachi, N. Fujii, Y. Yamamoto, Y. Zaizen, T. Hirano, and H. Iwamoto describes a process of bonding small InGaAs dies onto a Si wafer:

"We developed a back-illuminated InGaAs image sensor with 1280x1040 pixels at 5-um pitch by using Cu-Cu hybridization connecting different materials, a III-V InGaAs/InP of photodiode array (PDA), and a silicon readout integrated circuit (ROIC). A new process architecture using an InGaAs/InP dies-to-silicon wafer and Cu-Cu bonding was established for high productivity and pixel-pitch scaling. We achieved low dark current and high sensitivity for wavelengths ranging from visible to short-wavelength infrared (SWIR)."

7 comments:

  1. Generally, how does dark current relate to pixel pitch, if measured per sensor area? In other words, will a 2x2 micron pixel produce more, the same or less dark current then four 1x1 micron pixels? (Visual range, BSI CMOS, total effective area, not just active pixel area).

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    1. Albert Theuwissen - Harvest ImagingJanuary 6, 2020 at 9:42 PM

      It depends on several parameters like lay-out and technology. But in general I would say that a 2x2 um2 pixel will have LESS dark current than 4 times a 1x1 um2 pixel. Because the larger pixel has less perimeter, has less edges/corners and has less mechanical stress than the 4 times 1x1 um2. But once more, lay-out and technology play a very important role !

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  2. Look to the scaling.
    regular SWIR detectors are now in the order of 10-12 um pixel size. Reducing to 5 um pixel size will certainly reduce the dark current in case of a planar process.

    There is another important aspect: the photon flux will reduce also with a factor 4, when keeping all other parameters constant (distance, object resolution). This means that the noise in dark conditions shall also reduce with a factor 4 to keep performance equal.

    in SWIR pixel size or image sensor area is still a very important cost driver. this development will reduce the cost (!!) with a factor of 4.

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    1. Sorry I asked this after the SWIR article. I got hung up in fig. 14. and meant to ask for the visual range 380-700nm, with or without CFA. I want to know if SW pixel binning are as good as having physically larger pixels, given the same low light conditions, same physical sensor size, same physical image size, same viewing distance etc.

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  3. Is it correct that the papers presented at IEDM are not publically available? Or do they get published somewhere after some time?

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    1. The papers are usually published in IEEE library few months after the conference. However, the presentation materials are not publicly available, as far as I know.

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  4. Very interesting. Did they give the overall read noise performance of the sensor, details on the ROIC architecture ?

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