The Quality Control (QC) of pre-production strip sensors for the Inner Tracker (ITk) of the ATLAS Inner Detector upgrade has finished, and the collaboration has embarked on the QC test programme for ...production sensors. This programme will last more than 3 years and comprises the evaluation of approximately 22000 sensors. 8 Types of sensors, 2 barrel and 6 endcap, will be measured at many different collaborating institutes. The sustained throughput requirement of the combined QC processes is around 500 sensors per month in total. Measurement protocols have been established and acceptance criteria have been defined in accordance with the terms agreed with the supplier. For effective monitoring of test results, common data file formats have been agreed upon across the collaboration. To enable evaluation of test results produced by many different test setups at the various collaboration institutes, common algorithms have been developed to collate, evaluate, plot and upload measurement data. This allows for objective application of pass/fail criteria and compilation of corresponding yield data. These scripts have been used to process the data of more than 3000 sensors so far, and have been instrumental for identification of faulty sensors and monitoring of QC testing progress.
The ATLAS experiment is going to replace the current Inner Detector with an all new inner tracker (ITk) in the ATLAS detector for HL-LHC at CERN. Silicon strip detectors cover the outer layers of the ...barrel and the endcap sections. We have designed and fabricated a prototype single-sided n+-in-p AC-coupled silicon strip sensor for the outer barrel layer with long strips (LS), ATLAS17LS. It is of the maximum allowable size to fit in a 6-in. silicon wafer, with an outer dimension of 9.80(width)×9.76(length)cm2. The sensor features two rows of LS strip segments, 4.83 cm strip length per segment, a strip pitch of 75.5 μm, and a slim edge design. We have implemented technology for high voltage operation of up to 1000V, with a good signal collection after irradiation fluence of 5.6 × 1014neq∕cm2at the end of HL-LHC operation.
We had two objectives for the ATLAS17LS fabrication: qualification of the sensor design and fabrication quality, and providing an adequate number of the sensors for prototyping the building blocks of the strip detector. The sensors were fabricated in 3 batches by HPK with standard wafers from the foundry (320 μm physical thickness). Additional 10 sensors were fabricated with a thinner active thickness of 240 μm to investigate the influence of active thickness on charge collection. Another additional 5 sensors, with special passivation to investigate the influence of passivation on humidity sensitivity. The visual inspection of fabricated sensors revealed an inadequacy that the designed metal width of 10 μm was too narrow. The initial measurements by the vendor showed that the sensors fulfilled the specifications: onset voltages of Microdischarge VMD above the operation voltage VOP (700V for the 1st and 2nd batches; 500V for the 3rd batch, which has improved the yield), leakage currents of < 0.1μA/cm2 at VOP, full depletion voltages VFD< 330V, and rates of bad strips <<1%.
Strip sensor performance in prototype modules built for ATLAS ITk Helling, C.; Allport, P.; Affolder, A.A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Letnik:
978, Številka:
C
Journal Article
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ATLAS experiment is preparing an upgrade of its detector for High-Luminosity LHC (HL-LHC) operation. The upgrade involves installation of the new all-silicon Inner Tracker (ITk). In the context of ...the ITk preparations, more than 80 strip modules were built with prototype barrel sensors. They were tested with electrical readout on a per-channel basis. In general, an excellent performance was observed, consistent with previous ASIC-level and sensor-level tests. However, the lessons learned included two phenomena important for the future phases of the project. First was the need to store and test the modules in a dry environment due to humidity sensitivity of the sensors. The second was an observation of high noise regions for 2 modules.
The high noise regions were tested further in several ways, including monitoring the performance as a function of time and bias voltage. Additionally, direct sensor-level tests were performed on the affected channels. The inter-strip resistance and bias resistance tests showed low values, indicating a temporary loss of the inter-strip isolation. A subsequent recovery of the noise performance was observed. We present the test details, an analysis of how the inter-strip isolation affects the module noise, and the relationship with sensor-level quality control tests.
The inner tracker of the ATLAS detector is scheduled to be replaced by a completely new silicon-based inner tracker (ITk) for the Phase-II of the CERN LHC (HL-LHC). The silicon strip detector covers ...the volume 40<R<100 cm in the radial and |z|<300 cm in the longitudinal directions. The silicon sensors for the detector will be fabricated using the n+-on-p 6-inch wafer technology, for a total of 22,000 wafers. Intensive studies were carried out on the final prototype sensors ATLAS17LS fabricated by Hamamatsu Photonics (HPK). The charge collection properties were examined using penetrating 90Sr β-rays and the ALIBAVA fast readout system for the miniature sensors of 1 cm ×1 cm in area. The samples were irradiated by protons in the 27 MeV Birmingham Cyclotron, the 70 MeV CYRIC at Tohoku University, and the 24 GeV CERN-PS, and by neutrons at Ljubljana TRIGA reactor for fluence values up to 2 × 1015 neq/cm2. The change in the charge collection with fluence was found to be similar to the previous prototype ATLAS12, and acceptable for the ITk. Sensors with two active thicknesses, 300μm (standard) and 240μm (thin), were compared and the difference in the charge collection was observed to be small for bias voltages up to 500 V. Some samples were also irradiated with gamma radiation up to 2 MGy, and the full depletion voltage was found to decrease with the dose. This was caused by the Compton electrons due to the 60Co gamma radiation. To summarize, the design of the ATLAS17LS and technology for its fabrication have been verified for implementation in the ITk. We are in the stage of sensor pre-production with the first sensors already delivered in January of 2020.
Abstract
In preparation for the High Luminosity LHC (HL-LHC) runs,
the ATLAS inner detector will be completely replaced with an all
silicon Inner Tracker (ITk). Hybrid silicon pixel modules will be
...used for the innermost tracking layers, and silicon micro-strip
detectors will be used the outer layers of the tracker. During the
production of the detector, the sensors, readout electronics, and
other components will undergo a series of quality control (QC) and
quality assurance tests. Defects in the fabrication of the sensors
will be flagged early in the manufacturer's and ATLAS QC tests. A
study of the influence of sensor defects was performed to assess the
characteristics of these defects in completed modules, and whether
any defect posed a risk to the operation of the front-end readout
electronics. All defects were found to have no impact on the
performance of the front-end readout electronics for healthy
amplifier channels, and defects that short the coupling between the
strip implant and the metal readout electrode were only noticeable
for strip leakage currents in excess of 250 nA, beyond the
end-of-life currents expected for most sensors at the HL-LHC.
Abstract
Construction of the new all-silicon Inner Tracker (ITk), developed by the ATLAS collaboration to be
able to track charged particles produced at the High-Luminosity LHC, started in 2020 and ...is expected to
continue till 2028. The ITk detector will include 18,000 highly segmented and radiation hard n+-in-p
silicon strip sensors (ATLAS18), which are being manufactured by Hamamatsu Photonics. Mechanical and electrical characteristics of produced sensors are measured upon their delivery at several institutes participating in a complex Quality Control (QC) program. The QC tests performed on each individual sensor check the overall integrity and quality of the sensor.
During the QC testing of ATLAS18 strip sensors, an increased number of sensors that
failed the electrical tests was observed. In particular, IV measurements indicated an early breakdown,
while large areas containing several tens or hundreds of neighbouring strips with low interstrip isolation
were identified by the Full strip tests, and leakage current instabilities were measured in a long-term leakage current stability setup. Moreover, a high surface electrostatic charge reaching a level of several hundreds of volts per inch was measured on a large number of sensors and on the plastic sheets, which
mechanically protect these sensors in their paper envelopes. Accumulated data indicates a clear
correlation between observed electrical failures and the sensor charge-up.
To mitigate the above-described issues, the QC testing sites significantly modified the sensor handling
procedures and introduced sensor recovery techniques based on irradiation of the sensor surface with UV
light or application of intensive flows of ionized gas. In this presentation, we will describe the setups
implemented by the QC testing sites to treat silicon strip sensors affected by static charge and
evaluate the effectiveness of these setups in terms of improvement of the sensor performance.
Abstract
During the prototyping phase of the new ATLAS Inner-Tracker
(ITk) strip sensors, a degradation of the device breakdown voltage
at high humidity was observed. Although the degradation was
...temporary, showing a fast recovery in dry conditions, the study of
the influence of humidity on the sensor performance was critical to
establish counter-measures and handling protocols during production
testing in order to ensure the proper performance of the upgraded
detector.
The work presented here has the objective to study for the first
time the breakdown voltage deterioration in presence of ambient
humidity of ATLAS ITk production-layout strip sensors with different
surface properties, before and after proton, neutron and gamma
irradiations. A study of the humidity sensitivity of miniature ATLAS
ITk strip sensors, before and after proton irradiations, is also
presented to compare the sensitivity of devices with different
sizes.
The sensors were also exposed for several days to high humidity with
the aim to recreate and evaluate the influence of the detector
integration environment expected during the Large Hadron Collider
(LHC) Long Shutdown 3 (LS3) in 2026, where the sensors will be
exposed to ambient humidity for prolonged times.
Detailed studies of full-size ATLAS12 sensors Hommels, L.B.A.; Baca, M.; Broughton, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2016, Letnik:
831
Journal Article
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The “ATLAS ITk Strip Sensor Collaboration” R&D group has developed a second iteration of single-sided n+-in-p type micro-strip sensors for use in the tracker upgrade of the ATLAS experiment at the ...High-Luminosity (HL) LHC. The full size sensors measure approximately 97×97mm2 and are designed for tolerance against the 1.1×1015neq/cm2 fluence expected at the HL-LHC. Each sensor has 4 columns of 1280 individual 23.9mm long channels, arranged at 74.5μm pitch. Four batches comprising 120 sensors produced by Hamamatsu Photonics were evaluated for their mechanical, and electrical bulk and strip characteristics. Optical microscopy measurements were performed to obtain the sensor surface profile. Leakage current and bulk capacitance properties were measured for each individual sensor. For sample strips across the sensor batches, the inter-strip capacitance and resistance as well as properties of the punch-through protection structure were measured. A multi-channel probecard was used to measure leakage current, coupling capacitance and bias resistance for each individual channel of 100 sensors in three batches. The compiled results for 120 unirradiated sensors are presented in this paper, including summary results for almost 500,000 strips probed. Results on the reverse bias voltage dependence of various parameters and frequency dependence of tested capacitances are included for validation of the experimental methods used. Comparing results with specified values, almost all sensors fall well within specification.
Charge collection properties of particle detectors made in HV-CMOS technology were investigated before and after irradiation with reactor neutrons. Two different sensor types were designed and ...processed in 180 and 350 nm technology by AMS. Edge-TCT and charge collection measurements with electrons from super(90)Sr source were employed. Diffusion of generated carriers from undepleted substrate contributes significantly to the charge collection before irradiation, while after irradiation the drift contribution prevails as shown by charge measurements at different shaping times. The depleted region at a given bias voltage was found to grow with irradiation in the fluence range of interest for strip detectors at the HL-LHC. This leads to large gains in the measured charge with respect to the one before irradiation. The increase of the depleted region was attributed to removal of effective acceptors. The evolution of depleted region with fluence was investigated and modeled. Initial studies show a small effect of short term annealing on charge collection.
A radiation hard n+-in-p micro-strip sensor for the use in the Upgrade of the strip tracker of the ATLAS experiment at the High Luminosity Large Hadron Collider (HL-LHC) has been developed by the ...“ATLAS ITk Strip Sensor collaboration” and produced by Hamamatsu Photonics.
Surface properties of different types of end-cap and barrel miniature sensors of the latest sensor design ATLAS12 have been studied before and after irradiation. The tested barrel sensors vary in “punch-through protection” (PTP) structure, and the end-cap sensors, whose stereo-strips differ in fan geometry, in strip pitch and in edge strip ganging options. Sensors have been irradiated with proton fluences of up to 1×1016 neq/cm2, by reactor neutron fluence of 1×1015 neq/cm2 and by gamma rays from 60Co up to dose of 1MGy. The main goal of the present study is to characterize the leakage current for micro-discharge breakdown voltage estimation, the inter-strip resistance and capacitance, the bias resistance and the effectiveness of PTP structures as a function of bias voltage and fluence. It has been verified that the ATLAS12 sensors have high breakdown voltage well above the operational voltage which implies that different geometries of sensors do not influence their stability. The inter-strip isolation is a strong function of irradiation fluence, however the sensor performance is acceptable in the expected range for HL-LHC. New gated PTP structure exhibits low PTP onset voltage and sharp cut-off of effective resistance even at the highest tested radiation fluence. The inter-strip capacitance complies with the technical specification required before irradiation and no radiation-induced degradation was observed. A summary of ATLAS12 sensors tests is presented including a comparison of results from different irradiation sites. The measured characteristics are compared with the previous prototype of the sensor design, ATLAS07.
•Surface study verified high radiation resistance of developed n-in-p strip sensors.•Sensors have high breakdown voltage before and after irradiation.•Inter-strip capacitance is sufficiently low and does not change with irradiation.•Primary factor of inter-strip resistance decrease is total ionizing dose.•New gated PTP doubles current flowing into bias rail without onset voltage increase.
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