79 research outputs found
Displacement Damage Effects in Pinned Photodiode CMOS Image Sensors
No full textThis paper investigates the effects of displacement damage in Pinned Photodiode (PPD) CMOS Image Sensors (CIS) using proton and neutron irradiations. The DDD ranges from 12 TeV/g to TeV/g. Particle fluence up to n.cm is investigated to observe electro-optic degradation in harsh environments. The dark current is also investigated and it would appear that it is possible to use the dark current spectroscopy in PPD CIS. The dark current random telegraph signal is also observed and characterized using the maximum transition amplitude
Similarities Between Proton and Neutron Induced Dark Current Distribution in CMOS Image Sensors
No full textSeveral CMOS image sensors were exposed to neutron or proton beams (displacement damage dose range from 4 TeV/g to 1825 TeV/g) and their radiation-induced dark current distributions are compared. It appears that for a given displacement damage dose, the hot pixel tail distributions are very similar, if normalized properly. This behavior is observed on all the tested CIS designs (4 designs, 2 technologies) and all the tested particles (protons from 50 MeV to 500 MeV and neutrons from 14 MeV to 22 MeV). Thanks to this result, all the dark current distribution presented in this paper can be fitted by a simple model with a unique set of two factors (not varying from one experimental condition to another). The proposed normalization method of the dark current histogram can be used to compare any dark current distribution to the distributions observed in this work. This paper suggests that this model could be applied to other devices and/or irradiation conditions
Generic radiation hardened photodiode layouts for deep submicron CMOS image sensor processes
No full textSelected radiation hardened photodiode layouts, manufactured in a deep submicron CMOS Image Sensor technology, are irradiated by 60Co gamma-rays up to 2.2 Mrad(SiO2) and studied in order to identify the most efficient structures and the guidelines (recess distance, bias voltage) to follow to make them work efficiently in such technology. To do so, both photodiode arrays and active pixel sensors are used. After 2.2 Mrad(SiO2), the studied sensors are fully functional and most of the radiation hardened photodiodes exhibit radiation induced dark current values more than one order of magnitude lower than the standard photodiode
Radiation Effects in CMOS Isolation Oxides: Differences and Similarities With Thermal Oxides
No full textRadiation effects in thick isolation oxides of modern CMOS technologies are investigated using dedicated test structures designed using two commercial foundries. Shallow Trench Isolation and Pre-Metal Dielectric are studied using electrical measurements performed after X-ray irradiations and isochronal annealing cycles. This paper shows that trapping properties of such isolation oxides can strongly differ from those of traditional thermal oxides usually used to process the gate oxide of Metal Oxide Semiconductor Field Effect Transistors. Buildup and annealing of both radiation-induced oxide-trap charge and radiation-induced interface traps are discussed as a function of the oxide type, foundry and bias condition during irradiation. Radiation-induced interface traps in such isolation oxides are shown to anneal below 100°C contrary to what is usually observed in thermal oxides. Implications for design hardening and radiation tests of CMOS Integrated Circuits are discussed
Radiation Effects in Pinned Photodiode CMOS Image Sensors: Pixel Performance Degradation Due to Total Ionizing Dose
No full textSeveral Pinned Photodiode (PPD) CMOS Image Sensors (CIS) are designed, manufactured, characterized and exposed biased to ionizing radiation up to 10 kGy(SiO2 ). In addition to the usually reported dark current increase and quantum efficiency drop at short wavelengths, several original radiation effects are shown: an increase of the pinning voltage, a decrease of the buried photodiode full well capacity, a large change in charge transfer efficiency, the creation of a large number of Total Ionizing Dose (TID) induced Dark Current Random Telegraph Signal (DC-RTS) centers active in the photodiode (even when the Transfer Gate (TG) is accumulated) and the complete depletion of the Pre-Metal Dielectric (PMD) interface at the highest TID leading to a large dark current and the loss of control of the TG on the dark current. The proposed mechanisms at the origin of these degradations are discussed. It is also demonstrated that biasing (i.e., operating) the PPD CIS during irradiation does not enhance the degradations compared to sensors grounded during irradiation
In-Pixel source follower transistor RTS noise behavior under ionizing radiation in CMOS image sensors
No full textThis paper presents temporal noise measurement results for several total ionizing dose (TID) steps up to 2.19 Mrad of an image sensor designed with a 0.18-μm CMOS image sensor process. The noise measurements are focused on the random telegraph signal (RTS) noise due to the in-pixel source follower transistor of the sensor readout chain inducing noisy pixels. Results show no significant RTS noise degradation up to 300 krad of TID. Beyond this TID step, a limited RTS noise degradation is observed, and for the 2.19-Mrad step, an additional increase of total noise, including thermal, 1/f, and RTS noises, is noted.
Noisy pixels have been studied for high TIDs, and three cases have been observed: 1) no change on RTS behavior; 2) creation of RTS behavior; and 3) modifications of RTS behavior
Overview of ionizing radiation effects in image sensors fabricated in a deep-submicrometer CMOS imaging technology
No full textAn overview of ionizing radiation effects in imagers
manufactured in a 0.18-μm CMOS image sensor technology is presented. Fourteen types of image sensors are characterized and irradiated by a 60Co source up to 5 kGy. The differences between these 14 designs allow us to separately estimate the effect of ionizing radiation on microlenses, on low- and zero-threshold-voltage MOSFETs and on several pixel layouts using P+ guard-rings and edgeless transistors. After irradiation, wavelength dependent responsivity drops are observed. All the sensors exhibit a large dark current increase attributed to the shallow trench isolation that surrounds the photodiodes. Saturation voltage rises and readout chain gain variations are also reported. Finally, the radiation hardening perspectives resulting from this paper are discussed
New source of random telegraph signal in CMOS image sensors
No full textWe report a new source of dark current random telegraph signal in CMOS image sensors due to meta-stable Shockley-Read-Hall generation mechanism at oxide interfaces. The role of oxide defects is discriminated thanks to the use of ionizing radiations
Evidence of a novel source of random telegraph signal in CMOS image sensors
No full textThis letter reports a new source of dark current random telegraph signal in CMOS image sensors due to meta-stable Shockley-Read-Hall generation mechanism at oxide interfaces. The role of oxide defects is discriminated thanks to the use of ionizing radiations. A dedicated RTS detection technique and several test conditions (radiation dose, temperature, integration time, photodiode bias) reveal the particularities of this novel source of RTS
Single Event Effects in CMOS Image Sensors
No full textIn this work, 3T Active Pixel Sensors (APS) are exposed to heavy ions (N, Ar, Kr, Xe), and Single Event Effects (SEE) are studied. Devices were fully functional during exposure, no Single Event Latch-up (SEL) or Single Event Functional Interrupt (SEFI) happened. However Single Event Transient (SET) effects happened on frames: line disturbances, and half or full circular clusters of white pixels. The collection of charges in cluster was investigated with arrays of two pixel width (7 and 10 \textmu{}m), with bulk and epitaxial substrates. This paper shows technological and design parameters involved in the transient events. It also shows that STARDUST simulation software can predict cluster obtained for bulk substrate devices. However, the discrepancies in epitaxial layer devices are large - which shows the need for an improved model
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