9 February 2007 Improvement of crosstalk on 5M CMOS image sensor with 1.7x1.7&mgr;m2 pixels
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Crosstalk of CMOS Image Sensor (CIS) causes degradation of spatial resolution, color mixing and leads to image noise. Crosstalk consists of spectral, optical and electrical components, but definition of each component is obscure and difficult to quantify. For the first time, quantifiable definition of each component is proposed to perform crosstalk analysis in this paper. Contribution of each component to the total crosstalk is analyzed using opto-electrical simulation. Simulation is performed with an internally developed 2D finite difference time domain (FDTD) simulator coupled to a commercial device simulator. Simulation domain consists of set of four pixels. Plane wave propagation from micro-lens to the photodiode is analyzed with FDTD and the optical simulation result is transformed into the photo-current in the photodiode using electrical simulation. The total crosstalk consists of 43% of spectral crosstalk, 14% of optical cross talk, and 43% of electrical crosstalk at the normal incident light. Spectral crosstalk can be suppressed through careful selection of color filter materials with good selectivity of color spectrum. Characteristics of crosstalk and photosensitivity show contrary trend to one another as a function of color filter thickness. Therefore, the crosstalk target is fixed and simulation is performed to determine the minimum color filter thickness that satisfies the crosstalk target. By color filter material and thickness optimization, 10% increase in photosensitivity and 7% decrease spectral crosstalk were obtained. Electrical crosstalk showed 11% and 9% improvement through applying to new implantation process and stacking multi-epi layer on the p-type substrate, respectively.
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Chang-Hyo Koo, Chang-Hyo Koo, Hong-Ki Kim, Hong-Ki Kim, Kee-Hyun Paik, Kee-Hyun Paik, Doo-Chul Park, Doo-Chul Park, Keun-Ho Lee, Keun-Ho Lee, Young-Kwan Park, Young-Kwan Park, Chang-Rok Moon, Chang-Rok Moon, Seok-Ha Lee, Seok-Ha Lee, Sung-Ho Hwang, Sung-Ho Hwang, Duck-Hyung Lee, Duck-Hyung Lee, Jeong-Taek Kong, Jeong-Taek Kong, } "Improvement of crosstalk on 5M CMOS image sensor with 1.7x1.7&mgr;m2 pixels", Proc. SPIE 6471, Ultrafast Phenomena in Semiconductors and Nanostructure Materials XI and Semiconductor Photodetectors IV, 647115 (9 February 2007); doi: 10.1117/12.701705; https://doi.org/10.1117/12.701705

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