211 research outputs found
Characterization of FBK small-pitch 3D diodes after neutron irradiation up to 3.5x10**16 neq cm**-2
We report on the characterization by a position resolved laser system of
small-pitch 3D diodes irradiated with neutrons up to an extremely high fluence
of 3.5x10**16 neq cm**-2. We show that very high values of signal efficiency
are obtained, in good agreement with the geometrical expectation based on the
small values of the inter-electrode spacings, and also boosted by charge
multiplication effects at high voltage. These results confirm the very high
radiation tolerance of small-pitch 3D sensors well beyond the maximum fluences
expected at the High Luminosity LHC.Comment: 10 pages, 7 figures, submitted to Proceedings of IWORID 2018 on JINS
Progress in 3D Silicon Radiation Detectors
In the past few years, there has been an increasing interest toward 3D silicon radiation detectors. Owing to their unique architecture, 3D detectors provide a remarkable radiation hardness at relatively low bias voltage (hence low power dissipation), that makes them the most appealing solution for use in the innermost layers of tracking detectors in High Energy Physics (HEP) experiments. Besides this primary application, the use of 3D sensor technology has been extended also to other fields, like thermal neutron detection and microdosimetry for proton and ion therapy. In this paper, we will review the state of the art and on going efforts in 3D detectors, covering the main design and technological issues, as well as selected results from the experimental characterization and TCAD simulation.publishedVersio
Development of New 3D Pixel Sensors for Phase 2 Upgrades at LHC
We report on the development of new 3D pixel sensors for the Phase 2 Upgrades
at the High-Luminosity LHC (HL-LHC). To cope with the requirements of increased
pixel granularity (e.g., 50x50 or 25x100 um2 pixel size) and extreme radiation
hardness (up to a fluence of 2e16 neq cm-2), thinner 3D sensors (~100 um) with
electrodes having narrower size (~ 5 um) and reduced spacing (~ 30 um) are
considered. The paper covers TCAD simulations, as well as technological and
design aspects relevant to the first batch of these 3D sensors, that is
currently being fabricated at FBK on 6-inch wafers.Comment: 4 pages, 8 figures, 2015 IEEE Nuclear Science Symposium and Medical
Imaging Conferenc
TCAD Analysis of Leakage Current and Breakdown Voltage in Small Pitch 3D Pixel Sensors
Small-pitch 3D pixel sensors have been developed to equip the innermost layers of the ATLAS and CMS tracker upgrades at the High Luminosity LHC. They feature 50 Ă— 50 and 25 Ă— 100 ÎĽm2 geometries and are fabricated on p-type Si-Si Direct Wafer Bonded substrates of 150 ÎĽm active thickness with a single-sided process. Due to the short inter-electrode distance, charge trapping effects are strongly mitigated, making these sensors extremely radiation hard. Results from beam test measurements of 3D pixel modules irradiated at large fluences (1016neq/cm2) indeed demonstrated high efficiency at maximum bias voltages of the order of 150 V. However, the downscaled sensor structure also lends itself to high electric fields as the bias voltage is increased, meaning that premature electrical breakdown due to impact ionization is a concern. In this study, TCAD simulations incorporating advanced surface and bulk damage models are used to investigate the leakage current and breakdown behavior of these sensors. Simulations are compared with measured characteristics of 3D diodes irradiated with neutrons at fluences up to 1.5 Ă— 1016neq/cm2. The dependence of the breakdown voltage on geometrical parameters (e.g., the n+ column radius and the gap between the n+ column tip and the highly doped p++ handle wafer) is also discussed for optimization purposes
First Production of New Thin 3D Sensors for HL-LHC at FBK
Owing to their intrinsic (geometry dependent) radiation hardness, 3D pixel
sensors are promising candidates for the innermost tracking layers of the
forthcoming experiment upgrades at the Phase 2 High-Luminosity LHC (HL-LHC). To
this purpose, extreme radiation hardness up to the expected maximum fluence of
2e16 neq.cm-2 must come along with several technological improvements in a new
generation of 3D pixels, i.e., increased pixel granularity (50x50 or 25x100 um2
cell size), thinner active region (~100 um), narrower columnar electrodes (~5
um diameter) with reduced inter-electrode spacing (~30 um), and very slim edges
(~100 um). The fabrication of the first batch of these new 3D sensors was
recently completed at FBK on Si-Si direct wafer bonded 6-inch substrates.
Initial electrical test results, performed at wafer level on sensors and test
structures, highlighted very promising performance, in good agreement with TCAD
simulations: low leakage current (<1 pA/column), intrinsic breakdown voltage of
more than 150 V, capacitance of about 50 fF/column, thus assessing the validity
of the design approach. A large variety of pixel sensors compatible with both
existing (e.g., ATLAS FEI4 and CMS PSI46) and future (e.g., RD53) read-out
chips were fabricated, that were also electrically tested on wafer using a
temporary metal layer patterned as strips shorting rows of pixels together.
This allowed a statistically significant distribution of the relevant
electrical quantities to be obtained, thus gaining insight into the impact of
process-induced defects. A few 3D strip test structures were irradiated with
X-rays, showing inter-strip resistance of at least several GOhm even after 50
Mrad(Si) dose, thus proving the p-spray robustness. We present the most
important design and technological aspects, and results obtained from the
initial investigations.Comment: 8 pages, 7 figures, 2016 IWORI
A 180-nm CMOS Time-of-Flight 3-D Image Sensor
Abstract-We report on the design and the experimental characterization of a new 3-D image sensor, based on a new 120-nm CMOS-compatible photo-detector, which features an internal demodulation mechanism effective up to high frequencies. The distance range covered by our proof-of-concept device spans from 1-m to a few meter, and the resolution is about 1-cm
PixFEL: development of an X-ray diffraction imager for future FEL applications
A readout chip for diffraction imaging applications at new generation X-ray FELs (Free Electron
Lasers) has been designed in a 65 nm CMOS technology. It consists of a 32 Ă— 32 matrix, with
square pixels and a pixel pitch of 110 µm. Each cell includes a low-noise charge sensitive amplifier
(CSA) with dynamic signal compression, covering an input dynamic range from 1 to 104 photons
and featuring single photon resolution at small signals at energies from 1 to 10 keV. The CSA
output is processed by a time-variant shaper performing gated integration and correlated double
sampling. Each pixel includes also a small area, low power 10-bit time-interleaved Successive
Approximation Register (SAR) ADC for in-pixel digitization of the amplitude measurement. The
channel can be operated at rates up to 4.5 MHz, to be compliant with the rates foreseen for future
X-ray FEL machines. The ASIC has been designed in order to be bump bonded to a slim/active
edge pixel sensor, in order to build the first demonstrator for the PixFEL (advanced X-ray PIXel
cameras at FELs) imager
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