Sensors (Oct 2023)

A Thin-Film Pinned-Photodiode Imager Pixel with Fully Monolithic Fabrication and beyond 1Me- Full Well Capacity

  • Joo Hyoung Kim,
  • Francois Berghmans,
  • Abu Bakar Siddik,
  • Irem Sutcu,
  • Isabel Pintor Monroy,
  • Jehyeok Yu,
  • Tristan Weydts,
  • Epimitheas Georgitzikis,
  • Jubin Kang,
  • Yannick Baines,
  • Yannick Hermans,
  • Naresh Chandrasekaran,
  • Florian De Roose,
  • Griet Uytterhoeven,
  • Renaud Puybaret,
  • Yunlong Li,
  • Itai Lieberman,
  • Gauri Karve,
  • David Cheyns,
  • Jan Genoe,
  • Paweł E. Malinowski,
  • Paul Heremans,
  • Kris Myny,
  • Nikolas Papadopoulos,
  • Jiwon Lee

DOI
https://doi.org/10.3390/s23218803
Journal volume & issue
Vol. 23, no. 21
p. 8803

Abstract

Read online

Thin-film photodiodes (TFPD) monolithically integrated on the Si Read-Out Integrated Circuitry (ROIC) are promising imaging platforms when beyond-silicon optoelectronic properties are required. Although TFPD device performance has improved significantly, the pixel development has been limited in terms of noise characteristics compared to the Si-based image sensors. Here, a thin-film-based pinned photodiode (TF-PPD) structure is presented, showing reduced kTC noise and dark current, accompanied with a high conversion gain (CG). Indium-gallium-zinc oxide (IGZO) thin-film transistors and quantum dot photodiodes are integrated sequentially on the Si ROIC in a fully monolithic scheme with the introduction of photogate (PG) to achieve PPD operation. This PG brings not only a low noise performance, but also a high full well capacity (FWC) coming from the large capacitance of its metal-oxide-semiconductor (MOS). Hence, the FWC of the pixel is boosted up to 1.37 Me- with a 5 μm pixel pitch, which is 8.3 times larger than the FWC that the TFPD junction capacitor can store. This large FWC, along with the inherent low noise characteristics of the TF-PPD, leads to the three-digit dynamic range (DR) of 100.2 dB. Unlike a Si-based PG pixel, dark current contribution from the depleted semiconductor interfaces is limited, thanks to the wide energy band gap of the IGZO channel material used in this work. We expect that this novel 4 T pixel architecture can accelerate the deployment of monolithic TFPD imaging technology, as it has worked for CMOS Image sensors (CIS).

Keywords