Abstract

The photodiode in a CMOS indirect time-of-flight (ITOF) sensor is a two-tap sensor especially designed for ranging. The three most important parameters are the demodulation contrast (DC), quantum efficiency (QE), and crosstalk. A trench nanostructure is commonly used as isolation layer between the pixels in a backside-illuminated CMOS sensor. In this paper, a trench is used to increase the IR absorption and decrease the crosstalk between pixels without a decrease in the DC. A trench grid is designed on top of a 6 µm thick silicon absorption layer to increase the optical path. A metal layer also is placed under the Si absorption layer as a reflection layer. The absorption of 940 nm infrared light can be increased up to 50%. The estimated QE can reach up to 40% at 940 nm. Deep trench isolation with a 6 µm depth is also used to isolate neighboring pixels. The crosstalk between the pixels can be reduced to less than 4% per neighboring pixel. This result shows a feasible CMOS ITOF sensor pixel design that we believe has great potential for use in solid-state lidar, depth cameras, machine vision, biomedical engineering, and facial recognition.

© 2022 Optica Publishing Group

Design of a CMOS image sensor pixel with embedded polysilicon nano-grating for near-infrared imaging enhancement

Elie Cobo, Sébastien Massenot, Alexandre Le Roch, Franck Corbière, Vincent Goiffon, Pierre Magnan, and Jean-Luc Pelouard
Appl. Opt. 61(4) 960-968 (2022)

Characterization and analysis of electrical crosstalk in a linear array of CMOS image sensors

Mehdi Khabir and Mohammad Azim Karami
Appl. Opt. 61(33) 9851-9859 (2022)

Photon confinement in a silicon cavity of an image sensor by plasmonic diffraction for near-infrared absorption enhancement

Takahito Yoshinaga, Kazuma Hashimoto, Nobukazu Teranishi, and Atsushi Ono
Opt. Express 30(20) 35516-35525 (2022)

Method for power reduction of demodulation driver circuit in indirect time-of-flight CMOS image sensor

Kaiming Nie, Guan Tian, Quanmin Chen, Zeqing Wang, Jiangtao Xu, and Zhiyuan Gao
Appl. Opt. 60(34) 10649-10659 (2021)

Near-infrared sensitivity improvement by plasmonic diffraction for a silicon image sensor with deep trench isolation filled with highly reflective metal

Atsushi Ono, Kazuma Hashimoto, and Nobukazu Teranishi
Opt. Express 29(14) 21313-21319 (2021)