Diffraction feature of microlens array with a small aperture size

Park, Seungryong; Park, Jinho; Choi, Hakyu; Yun, Young-Je; Choi, Kwangseon; Kim, Jeahee

doi:10.1117/12.772480

Cited by 1 publication

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“…In the front-end circuits of single-photon avalanche diodes (SPADs), similar approaches effectively reduce the spacing between pixels so the fill factor (FF) can be increased [2]. To further enhance the FF of imaging sensor array with in-pixel circuits, the on-chip micro-lenses have been introduced to achieve a nearly 100% FF [3,4]. However, the previous work showed that the micro-lenses could increase the energy density of incident light by at least 50%, which raised concerns about the reliability of devices and circuits when exposed to high-intensity light sources and/or strong ambient illumination [5].…”

Section: Introductionmentioning

confidence: 99%

N-Channel MOSFET Reliability Issue Induced by Visible/Near-Infrared Photons in Image Sensors

Liu,

Lin

2023

Sensors

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Image sensors such as single-photon avalanched diode (SPAD) arrays typically adopt in-pixel quenching and readout circuits, and the under-illumination first-stage readout circuits often employs high-threshold input/output (I/O) or thick-oxide metal-oxide-semiconductor field-effect transistors (MOSFETs). We have observed reliability issues with high-threshold n-channel MOSFETs when they are exposed to strong visible light. The specific stress conditions have been applied to observe the drain current (Id) variations as a function of gate voltage. The experimental results indicate that photo-induced hot electrons generate interface trap states, leading to Id degradation including increased off-state current (Ioff) and decreased on-state current (Ion). The increased Ioff further activates parasitic bipolar junction transistors (BJT). This reliability issue can be avoided by forming an inversion layer in the channel under appropriate bias conditions or by reducing the incident photon energy.

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