Radiation Effects in CMOS Image Sensor Technologies

CMOS image sensors are central to modern imaging applications, from consumer electronics to spaceborne and nuclear instrumentation. Exposure to ionising radiation—such as protons, neutrons, electrons and gamma rays—induces two primary damage mechanisms: ionisation effects in dielectric layers and displacement damage in the silicon lattice. Ionisation leads to trapped charge in oxides and at interfaces, elevating dark current, shifting transistor thresholds and degrading noise performance. Displacement damage generates lattice defects that act as generation–recombination centres, increasing dark signal non-uniformity and giving rise to random telegraph signals. Advancements in pinned photodiode architectures and radiation-hard-by-design pixel layouts have mitigated these effects, balancing tolerance against quantum efficiency, dynamic range and noise requirements. Such developments are critical for sensors operating under total ionising doses of up to several megarads and displacement damage fluences exceeding 10^12 n cm^–2, with applications spanning high-energy physics, space exploration and nuclear facility monitoring.

Research from Nature Portfolio

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Research from all publishers

Proton irradiation studies on 0.18 µm backside-illuminated pinned photodiode sensors revealed that cluster defects induce hot pixels with elevated dark current and pronounced random telegraph signals. Activation energy measurements pinpointed mid-gap defect levels, guiding pixel-level compensation and annealing strategies to suppress dark signal non-uniformity under proton fluences.

A CMOS active-pixel sensor designed with radiation-hard-by-design layouts sustained useful imaging performance after exposure up to 10 MGy of X-ray and gamma-ray total dose. Comparative evaluation of four photodiode layouts showed a novel gated-photodiode design preserving quantum efficiency, dark current and noise metrics most effectively, offering a blueprint for extreme-dose applications in nuclear and particle-physics experiments.

Neutron irradiation experiments across varied pixel pitches and photodiode geometries yielded an empirical model of dark current distributions as functions of neutron energy and fluence. The model accurately predicts dark signal non-uniformity for energies above 14 MeV and introduces a single scaling parameter for lower energies, informing sensor design and shielding choices in neutron-rich environments.

Radiation Effects in CMOS Image Sensor Technologies publication trend

The graph below shows the total number of articles in radiation effects in cmos image sensor technologies across all publications each year (not limited to Nature Index journals).

Technical terms

Dark current: Thermally generated charge accumulating in a pixel during integration, contributing to image noise.

Total ionising dose (TID): Cumulative energy deposited by ionising radiation in insulating materials, leading to trapped charges and transistor threshold shifts.

Displacement damage: Crystal lattice defects formed when energetic particles displace silicon atoms, creating generation–recombination centres.

Pinned photodiode (PPD): A photodiode structure with a fixed potential region that suppresses dark current and enables low noise and high dynamic range.

Random telegraph signal (RTS): Discrete, time-dependent fluctuations in pixel output caused by single-defect charge trapping and emission.

References

1. Multi-MGy Radiation Hard CMOS Image Sensor: Design, Characterization and X/Gamma Rays Total Ionizing Dose Tests. IEEE Transactions on Nuclear Science (2015).
2. Pixel pitch and particle energy influence on the dark current distribution of neutron irradiated CMOS image sensors.. Optics Express (2016).