Current Optics and Photonics

Optical Society of Korea (한국광학회)
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High-sensitivity NIR Sensing with Stacked Photodiode Architecture

  • Hyunjoon Sung (Department of ICT Integrated Safe Ocean Smart Cities Engineering, Dong-A University) ;
  • Yunkyung Kim (Department of ICT Integrated Safe Ocean Smart Cities Engineering, Dong-A University)
  • Received : 2022.09.28
  • Accepted : 2023.01.10
  • Published : 2023.04.25
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Abstract

Near-infrared (NIR) sensing technology using CMOS image sensors is used in many applications, including automobiles, biological inspection, surveillance, and mobile devices. An intuitive way to improve NIR sensitivity is to thicken the light absorption layer (silicon). However, thickened silicon lacks NIR sensitivity and has other disadvantages, such as diminished optical performance (e.g. crosstalk) and difficulty in processing. In this paper, a pixel structure for NIR sensing using a stacked CMOS image sensor is introduced. There are two photodetection layers, a conventional layer and a bottom photodiode, in the stacked CMOS image sensor. The bottom photodiode is used as the NIR absorption layer. Therefore, the suggested pixel structure does not change the thickness of the conventional photodiode. To verify the suggested pixel structure, sensitivity was simulated using an optical simulator. As a result, the sensitivity was improved by a maximum of 130% and 160% at wavelengths of 850 nm and 940 nm, respectively, with a pixel size of 1.2 ㎛. Therefore, the proposed pixel structure is useful for NIR sensing without thickening the silicon.

Keywords

Acknowledgement

The EDA tool was supported by the IC Design Education Center (IDEC), Korea.

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