Dark Signal Non-uniformity Research Articles

A CMOS Pixel With Embedded ADC, Digital CDS and Gain Correction Capability for Massively Parallel Imaging Array

In the paper, a CMOS pixel has been proposed for imaging arrays with massively parallel image acquisition and simultaneous compensation of dark signal nonuniformity (DSNU) as well as photoresponse nonuniformity (PRNU). In our solution the pixel contains all necessary functional blocks: a photosensor and an analog-to-digital converter (ADC) with built-in correlated double sampling (CDS) integrated together. It is implemented in standard $0.18~\mu \text {m}$ CMOS technology. The size of the pixel with 9-bit resolution is $21~\mu \text {m}\,\,\times 21\,\,\mu \text {m}$ . Measurements of the $128\times 128$ pixel array confirm functionality of the proposed solution. CDS reduces dark FPN from 12 LSB (3%) to 0.8 LSB (0.2%) and light FPN from 14 LSB (3.7%) to 7 LSB (1.8%). Further reduction of the light FPN (to ~1 LSB) was achieved by compensating PRNU using massively parallel innovative digital multiplication which features good resolution (1/511), does not disturb CDS executed at the same time, and can be implemented within a small pixel area.

Degradation and annealing studies on gamma rays irradiated COTS PPD CISs at different dose rates

The degradation and annealing studies on Colbalt-60 gamma-rays irradiated commercial-off-the-shelf (COTS) pinned photodiode (PPD) CMOS image sensors (CISs) at the various dose rates are presented. The irradiation experiments of COTS PPD CISs are carried out at 0.3, 3.0 and 30.0rad(Si)/s. The COTS PPD CISs are manufactured using a standard 0.18-μm CMOS technology with four-transistor pixel PPD architecture. The behavior of the tested CISs shows a remarkable degradation after irradiation and differs in the dose rates. The dark current, dark signal non-uniformity (DSNU), random noise, saturation output, signal to noise ratio (SNR), and dynamic range (DR) versus the total ionizing dose (TID) at the various dose rates are investigated. The tendency of dark current, DSNU, and random noise increase and saturation output, SNR, and DR to decrease at 3.0rad(Si)/s are far greater than those at 0.3 and 30.0rad(Si)/s. The damage mechanisms caused by TID irradiation at the various dose rates are also analyzed. The annealing tests are carried out at room temperature with unbiased conditions after irradiation.

Characterization of total ionizing dose damage in COTS pinned photodiode CMOS image sensors

The characterization of total ionizing dose (TID) damage in COTS pinned photodiode (PPD) CMOS image sensors (CISs) is investigated. The radiation experiments are carried out at a 60Co γ-ray source. The CISs are produced by 0.18-μm CMOS technology and the pixel architecture is 8T global shutter pixel with correlated double sampling (CDS) based on a 4T PPD front end. The parameters of CISs such as temporal domain, spatial domain, and spectral domain are measured at the CIS test system as the EMVA 1288 standard before and after irradiation. The dark current, random noise, dark signal non-uniformity (DSNU), photo response non-uniformity (PRNU), overall system gain, saturation output, dynamic range (DR), signal to noise ratio (SNR), quantum efficiency (QE), and responsivity versus the TID are reported. The behaviors of the tested CISs show remarkable degradations after radiation. The degradation mechanisms of CISs induced by TID damage are also analyzed.

电荷耦合器件中子辐照诱发的位移效应

Displacement damage effects due to neutron irradiations of charge coupled devices were presented through the analysis of the dark signals behavior in pixel arrays. When the fluence of neutron reached the predetermined point,the change of dark signal,dark signal non-uniformity,charge transfer efficiency and saturated output signal was measured off line. The major effect of neutron induced displacement damage on charge coupled device is the increase in dark signals as a result of carrier generation in the bulk depletion region of the pixel. Although the increase in the mean dark signals with neutron irradiation is important,the dark signals non-uniformity is generally the biggest concern for charge coupled device applications in space. Very large dark signals pixels can be produced when a collision occurs in a high electric field region of a pixel as a result of electric field enhanced emission. Another important performance parameter for a charge coupled device is the charge transfer efficiency,which is the fraction of signal charge transferred from pixel to pixel during read out. If a signal charge is trapped by neutron induced defect,and remains trapped for more than one clock cycle,it will be lost from the signalcharge packet. Saturation output signal voltage does not have any obvious degradation even at the highest DDD level. The research will help the designers to know the radiation damage in charge coupled device and improve the tolerance by radiation hardening design.

Evaluation of the Degradation on a COTS Linear CCD Induced by Total Ionizing Dose Radiation Damage

The evaluation of the degradation on a COTS linear Charge Coupled Device (CCD) induced by total ionizing dose (TID) radiation damage was presented. The radiation experiments were carried out at a60Coγ-ray source. The parameters of DALSA’s linear CCD were measured at the CCD test systems as the EMVA1288 standard before and after the radiation. The dark current, dark signal nonuniformity (DSNU), photo response nonuniformity (PRNU), saturation output, full-well capacity (FWC), quantum efficiency (QE), and responsivity versus the TID were analyzed. The behavior of the tested CCD had shown a remarkable degradation after radiation. The degradation mechanisms of the CCD induced by TID damage were also discussed.

Neutron radiation effects on linear CCDs at different clock pulse frequency

The experiments of reactor neutron radiation effects on linear CCDs are presented. The output voltage in dark field after neutron radiation are presented and compared at different clock pulse frequency. The degradation phenomena are analyzed in depth. The mean dark signal (KD) and dark signal non-uniformity (DSNU) versus neutron fluence is investigated at different clock pulse frequency. The degradation mechanisms of the dark signal and DSNU in linear CCDs are analyzed. The flux of the reactor neutron beams was about 1.33 × 108 n/cm2/s. The samples were exposed to 1MeV neutron-equivalent fluences of 1 × 1011, 5 × 1011, and 1 × 1012 n/cm2, respectively.

Degradation of CMOS APS Image Sensors Induced by Total Ionizing Dose Radiation at Different Dose Rates and Biased Conditions

The experiments of total ionizing dose radiation effects on CMOS APS image sensors at the dose rates of 50.0 and 0.2 rad(Si)/s were presented. The CMOS APS image sensors were manufactured using the standard <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$0.35 - \mu \hbox{m}$</tex></formula> CMOS technology that had a typical gate-oxide thickness of 7.0 nm. The samples were divided into two groups, with one group biased and the other unbiased during <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{60}{\rm Co}\gamma $</tex> </formula> irradiation. When the samples were exposed to the total dose of 200 krad(Si), only one investigated device was still exposed up to the highest total dose of 800 krad(Si), and functional failure was observed. The dark signal ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${K_{\rm D}}$</tex></formula> ), dark signal non-uniformity (DSNU), noise ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${V_{\rm N}}$</tex></formula> ), saturation output signal voltage ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${V_{\rm S}}$</tex></formula> ), and dynamic range (DR) versus the total doses were investigated. The tendency for <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$K_{\rm D}$</tex></formula> , DSNU, and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${V_{\rm N}}$</tex></formula> to increase at 50.0 rad(Si)/s is larger than that at 0.2 rad(Si)/s. The degradation mechanisms of CMOS APS image sensors were analyzed. The room temperature annealing tests were performed at 24 h, 48 h, and 168 h with different biased conditions after irradiation.

Combined reactor neutron beam and 60Co γ-ray radiation effects on CMOS APS image sensors

The combined reactor neutron beam and 60Co γ-ray radiation effects on complementary metal-oxide semiconductor (CMOS) active pixel sensors (APS) have been discussed and some new experimental phenomena are presented. The samples are manufactured in the standard 0.35-μm CMOS technology. Two samples were first exposed to 60Co γ-rays up to the total ionizing dose (TID) level of 200 krad(Si) at the dose rates of 50.0 and 0.2 rad(Si)/s, and then exposed to neutron fluence up to 1 × 1011 n/cm2 (1-MeV equivalent neutron fluence). One sample was first exposed to neutron fluence up to 1 × 1011 n/cm2 (1-MeV equivalent neutron fluence), and then exposed to 60Co γ-rays up to the TID level of 200 krad(Si) at the dose rate of 0.2 rad(Si)/s. The mean dark signal (KD), the dark signal non-uniformity (DSNU), and the noise (VN) versus the total dose and neutron fluence has been investigated. The degradation mechanisms of CMOS APS image sensors have been analyzed, especially for the interaction induced by neutron displacement damage and TID damage.

Investigation of reactor neutron irradiation induced dark signals increase in COTS array CCDs

The experiments of reactor neutron irradiation which induce dark signal increase in COTS array CCDs are presented. The flux of the reactor neutron beams was about 1.33 × 108 n/cm2s. The three samples were exposed to 1MeV neutron-equivalent fluences of 1 × 1011, 5 × 1011, and 1 × 1012 n/cm2, respectively. The mean dark signal (KD), dark signal non-uniformity (DSNU), and dark signal spikes (hot pixels) versus neutron fluence are investigated. The degradation mechanisms of the dark signal in CCDs are analyzed. The mean dark signal increase due to neutron displacement damage appears to be proportional to displacement damage dose. The dark images from the CCDs irradiated by neutrons are presented to investigate the generation of dark signal spike. The 1D and 2D figures which show the output signal voltage of pixels in dark images irradiated by different neutron beam fluences, are presented to compare the degradation of KD, DSNU, and dark signal spike.

Displacement damage effects on CMOS APS image sensors induced by neutron irradiation from a nuclear reactor

The experiments of displacement damage effects on CMOS APS image sensors induced by neutron irradiation from a nuclear reactor are presented. The CMOS APS image sensors are manufactured in the standard 0.35 μm CMOS technology. The flux of neutron beams was about 1.33 × 108 n/cm2s. The three samples were exposed by 1 MeV neutron equivalent-fluence of 1 × 1011, 5 × 1011, and 1 × 1012 n/cm2, respectively. The mean dark signal (KD), dark signal spike, dark signal non-uniformity (DSNU), noise (VN), saturation output signal voltage (VS), and dynamic range (DR) versus neutron fluence are investigated. The degradation mechanisms of CMOS APS image sensors are analyzed. The mean dark signal increase due to neutron displacement damage appears to be proportional to displacement damage dose. The dark images from CMOS APS image sensors irradiated by neutrons are presented to investigate the generation of dark signal spike.

Research on dark signal degradation in 60Co γ-ray-irradiated CMOS active pixel sensor

A study of ionizing radiation effects is presented for CMOS active pixel sensors manufactured in a 0.5-μm CMOS (complementary metal oxide semiconductor)by n-well technology. The basic mechanisms that may cause failure are also presented. After exposure in γ-rays, the most sensitive parts to radiation-dark signals and dark signal non-uniformity are discussed, i.e. the physical mechanism of the degradation by irradiation. One can see from the experiment that the mean dark signals are dramatically increased with total dose for both operated and static devices. Static device seems more affected by irradiation than operated device. We find that most part of the total dark signal in a pixel comes from the depletion of the photodiode edge at the surface and the rest part is caused by the leakage of the source region of the reset transistor. Dark signal non-uniformity follows the dark current evolution with total dose. Further study of photodiode and LOCOS (local oxidation of silicon) isolation behaviors under irradiation should be done so as to correctly use this qualification techniques on MOS sensors manufactured in CMOS n-well technology process.

Single particle dark current spikes induced in CCDs by high energy neutrons

This paper presents an analysis of dark signal nonuniformity induced in a charge coupled device (CCD) by 90 MeV neutrons. Random telegraph signal switching between multiple levels was seen for some dark current spikes. The probability distribution of the dark current spikes is shown to be pseudo-exponential and the distribution remains exponential during annealing, but with an increasing decay constant. Similar dark current spikes were also observed to be generated in an APS device exposed to high energy neutrons at the WNR facility.

Evaluation and prediction of the degradation of a COTS CCD induced by displacement damage

Proton-irradiation results ranging from 17 MeV to 100 MeV are presented for silicon commercial off-the-shelf charge-coupled devices. Mean degradation of the dark current and the dark-signal nonuniformity are analyzed. A good linearity between proton-nonionizing energy loss and the mean dark-signal degradation is obtained. A method to determine parameters required by the Marshall method prediction is proposed. This method is based on the three experimental and theoretical moments. An excellent agreement is obtained with the experimental degradation. The last step is to perform the method on a continuous proton spectrum. Prediction of dark-signal behavior is in a good agreement with experimental data.

High-energy proton-induced dark signal in silicon charge coupled devices

The distribution of dark signal in 10 and 60 MeV proton irradiated charge-coupled devices is discussed and a newly modified theory of proton-induced dark signal nonuniformity is compared with measurements made on devices from Marconi Applied Technologies with differing pixel sizes. The models previously developed by other workers have been modified to enable better agreement with measurement at low proton fluency. The scaling of bulk dark signal with damage energy as a function of temperature is presented. This makes possible predictions of the mean bulk dark signal and its distribution for a wide range of device types, temperatures and proton fluencies. The dark signal increase from Co/sup 60/ gamma and neutron irradiation is also discussed.

Operation, Performance, And Reliability Testing Of Charge-Coupled Devices For Star Trackers

The improved cosmetic quality, charge-transfer efficiency, and low noise of present-generation CCDs means that modern two-axis star trackers can measure star positions to accuracies of 1/50 of a pixel over the whole chip area. However, CCD selection, testing, screening for enhanced reliability, and careful attention to operating conditions are still necessary. This paper is concerned primarily with the performance, testing, and qualification of English Electric Valve Co. P8604 CCDs for use in star trackers for the German Roentgen-Satellit (ROSAT) x-ray astronomy satellite, although the tests developed should be widely applicable. It was found that the best-quality devices are essentially free of all image blemishes and have a white noise of 15 nV/Hz deferred charge of less than 1 %, response uniformity of 1.5% rms, and dark signal nonuniform ity at 40°C of 30 electrons rms. All of the candidate devices from flight batches passed a burn-in under voltage and temperature stress that are predicted to be equivalent to more than seven years' continuous mission operation.