Thick silicon Hi-Rho CMOS with high red response

I. Read; D. Jordan; R. Mackie; J. Pratlong

doi:10.1117/12.2629951

29 August 2022 Thick silicon Hi-Rho CMOS with high red response

I. Read, D. Jordan, R. Mackie, J. Pratlong

Proceedings Volume 12191, X-Ray, Optical, and Infrared Detectors for Astronomy X; 121910F (2022) https://doi.org/10.1117/12.2629951
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

CMOS image sensors traditionally have used a pinned photodiode with a transfer gate to achieve low dark signal and noise. One drawback of the pinned photodiode is the inability to achieve good Modulation Transfer Function (MTF) as the sensor thickness is increased beyond epitaxial thicknesses greater than 10μm as required for higher red response. This is due to the pinned photodiode providing only a very small voltage to deplete the silicon, which results in significant lateral charge diffusion and poor resolution. The limitation in device thickness means that the QE at longer wavelengths (>600nm) is limited for conventional CMOS pixel technologies. A way to increase the depletion depth is to apply a back bias from the rear of the device, however if one were to do this on standard CMOS image sensors then there would be significant leakage current between the back bias and components on the device causing it to not function. A new patented DDE (Deep Depletion Extension) implant helps diode depletion regions to merge laterally creating a “pinch-off” and prevent leakage from in-pixel transistors. This enables epitaxial thickness of up to 50μm to be fully depleted with negligible leakage. The CIS220 is a new ESA GSTP funded derivative of the CIS120 Capella Space Imager platform which incorporates this patented HiRho back bias structure allowing full depletion of the sensor thickness. This paper will present initial results from back-thinned CIS220 devices with 17μm and 33μm thicknesses and will explore the effect of the back bias on electro-optical test results.

Conference Presentation

Citation Download Citation

I. Read, D. Jordan, R. Mackie, and J. Pratlong "Thick silicon Hi-Rho CMOS with high red response", Proc. SPIE 12191, X-Ray, Optical, and Infrared Detectors for Astronomy X, 121910F (29 August 2022); https://doi.org/10.1117/12.2629951

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