[Papers] Quantum Efficiency Simulation and Electrical Cross-talk Index Development with Monte-Carlo Simulation Based on Boltzmann Transport Equation

Abstract

180 IntroductionAs the pixel size of a color CMOS image sensor (CIS) shrinks downto sub-micron size, cross-talk 1) becomes one of the critical issues of image quality deterioration 2) .Among several types of cross-talks, electrical cross-talk can be suppressed by the introduction of deep trench isolation (DTI) technology 3) between photodiodes (PDs). In section 2, BTE is briefly explained, followed by the Abstract This paper explains a new method to model a photodiode for accurate quantum efficiency simulation. Individual photo-generated particles are modeled by Boltzmann transport equation, and simulated by Monte-Carlo method. Good accuracy is confirmed in terms of similarities of quantum efficiency curves, as well as color correction matrices and SNR10s. Three attributes -"initial energy of the electron", "recombination of electrons at the silicon surface" and "impurity scattering" -are tested to examine their effectiveness in the new model. The theoretical difference to the conventional method with drift-diffusion equation is discussed as well.Using the simulation result, the relationship among the cross-talk, potential barrier, and distance from the boundary has been studied to develop a guideline for cross-talk suppression. It is found that a product of the normal distance from the pixel boundary and the electric field perpendicular to the Z-axis needs to be more than 0.02V to suppress the probability of electron leakage to the adjacent pixel to less than 10%.