Photoresponse analysis and pixel shape optimization for CMOS APS

  • Authors:

  • Igor Shcherback;Orly Yadid-Pecht

  • Affiliations:

  • The VLSI Systems Center, Ben-Gurion University, P.O.B. 653 Beer-Sheva 84105, ISRAEL;The VLSI Systems Center, Ben-Gurion University, P.O.B. 653 Beer-Sheva 84105, ISRAEL

  • Venue:
  • CMOS imagers
  • Year:
  • 2004

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Abstract

A semi-analytical model has been developed for the estimation of the photoresponse of a photodiode-based CMOS active pixel sensor (APS). This model, based on a thorough analysis of experimental data, incorporates the effects of substrate diffusion as well as geometrical shape and size of the potodiode active area. It describes the dependence of pixel response on integration photocarriers and on conversion gain. The model also demonstrates that the tradeoff between these two conflicting factors gives rise to an optimum geometry, enabling the extraction of a maximum photoresponse. The dependence of the parameters on the process and design data is discussed, and the degree of accuracy for the photoresponse modeling is assessed.