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Open AccessArticle

Front-Inner Lens for High Sensitivity of CMOS Image Sensors

Department of Electronics Engineering, Dong-A University, Busan 49315, Korea
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Sensors 2019, 19(7), 1536; https://doi.org/10.3390/s19071536
Received: 28 February 2019 / Revised: 26 March 2019 / Accepted: 27 March 2019 / Published: 29 March 2019
(This article belongs to the Special Issue Advanced CMOS Image Sensors and Emerging Applications)
Due to the continuing improvements in camera technology, a high-resolution CMOS image sensor is required. However, a high-resolution camera requires that the pixel pitch is smaller than 1.0 μm in the limited sensor area. Accordingly, the optical performance of the pixel deteriorates with the aspect ratio. If the pixel depth is shallow, the aspect ratio is enhanced. Also, optical performance can improve if the sensitivity in the long wavelengths is guaranteed. In this current work, we propose a front-inner lens structure that enhances the sensitivity to the small pixel size and the shallow pixel depth. The front-inner lens was located on the front side of the backside illuminated pixel for enhancement of the absorption. The proposed structures in the 1.0 μm pixel pitch were investigated with 3D optical simulation. The pixel depths were 3.0, 2.0, and 1.0 μm. The materials of the front-inner lens were varied, including air and magnesium fluoride (MgF2). For analysis of the sensitivity enhancement, we compared the typical pixel with the suggested pixel and confirmed that the absorption rate of the suggested pixel was improved by a maximum of 7.27%, 10.47%, and 29.28% for 3.0, 2.0, and 1.0 μm pixel depths, respectively. View Full-Text
Keywords: front-inner lens; CMOS image sensor; FDTD simulation front-inner lens; CMOS image sensor; FDTD simulation
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Seok, G.; Kim, Y. Front-Inner Lens for High Sensitivity of CMOS Image Sensors. Sensors 2019, 19, 1536.

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