Influence of displacement damage dose on dark current distributions of irradiated CMOS image sensors

We developed silicon epitaxial wafers with high gettering capability by using hydrocarbon–molecular–ion implantation. These wafers also have the effect of hydrogen passivation on process-induced defects and a barrier to out-diffusion of oxygen of the Czochralski silicon (CZ) substrate bulk during Complementary metal-oxide-semiconductor (CMOS) device fabrication processes. We evaluated the electrical device performance of CMOS image sensor fabricated on this type of wafer by using dark current spectroscopy. We found fewer white spot defects compared with those of intrinsic gettering (IG) silicon wafers. We believe that these hydrocarbon–molecular–ion–implanted silicon epitaxial wafers will improve the device performance of CMOS image sensors.

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Random Telegraph Noises from the Source Follower, the Photodiode Dark Current, and the Gate-Induced Sense Node Leakage in CMOS Image Sensors

Sensors ◽

10.3390/s19245447 ◽

2019 ◽

Vol 19 (24) ◽

pp. 5447

Author(s):

Calvin Yi-Ping Chao ◽

Shang-Fu Yeh ◽

Meng-Hsu Wu ◽

Kuo-Yu Chou ◽

Honyih Tu ◽

...

Keyword(s):

Dark Current ◽

Image Sensors ◽

Integration Time ◽

X Ray ◽

Multiple Sampling ◽

Cmos Image Sensors ◽

Measurement Results ◽

Source Follower ◽

Different Types ◽

Dark Signal

In this paper we present a systematic approach to sort out different types of random telegraph noises (RTN) in CMOS image sensors (CIS) by examining their dependencies on the transfer gate off-voltage, the reset gate off-voltage, the photodiode integration time, and the sense node charge retention time. Besides the well-known source follower RTN, we have identified the RTN caused by varying photodiode dark current, transfer-gate and reset-gate induced sense node leakage. These four types of RTN and the dark signal shot noises dominate the noise distribution tails of CIS and non-CIS chips under test, either with or without X-ray irradiation. The effect of correlated multiple sampling (CMS) on noise reduction is studied and a theoretical model is developed to account for the measurement results.

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CMOS Image Sensors and Plasma Processes: How PMD Nitride Charging Acts on the Dark Current

Sensors ◽

10.3390/s19245534 ◽

2019 ◽

Vol 19 (24) ◽

pp. 5534

Author(s):

Yolène Sacchettini ◽

Jean-Pierre Carrère ◽

Romain Duru ◽

Jean-Pierre Oddou ◽

Vincent Goiffon ◽

...

Keyword(s):

Dark Current ◽

Uv Light ◽

Degradation Mechanism ◽

Nitride Layer ◽

Image Sensors ◽

Electron Hole ◽

Cmos Image Sensors ◽

Depth Analysis

Plasma processes are known to be prone to inducing damage by charging effects. For CMOS image sensors, this can lead to dark current degradation both in value and uniformity. An in-depth analysis, motivated by the different degrading behavior of two different plasma processes, has been performed in order to determine the degradation mechanisms associated with one plasma process. It is based on in situ plasma-induced charge characterization techniques for various dielectric stack structures (dielectric nature and stack configuration). A degradation mechanism is proposed, highlighting the role of ultraviolet (UV) light from the plasma in creating an electron hole which induces positive charges in the nitride layer at the wafer center, and negative ones at the edge. The trapped charges de-passivate the SiO2/Si interface by inducing a depleted interface above the photodiode, thus emphasizing the generation of dark current. A good correlation between the spatial distribution of the total charges and the value of dark current has been observed.

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