We are developing monolithic pixel sensors based on a 0.2 $mu$m fully-depleted Silicon-on-Insulator (SOI) technology for HEP experiment applications. The total ionizing dose (TID) effect is the major issue in the applications for hard radiation environments in HEP experiments. To compensate for TID damage, we have introduced a Double SOI structure which has a Middle Silicon layer (SOI2 layer) in addition. We studied the recovery from TID damage induced by $mathrm{^{60}Co}~gamma$s and other characteristics of an Integration-type Double SOI sensor. The Double SOI sensor irradiated to 100 kGy showed a response for IR laser similar to of a non-irradiated sensor when we applied a negative voltage to the SOI2 layer. We conclude that the Double SOI sensor is radiation hard enough to be used in HEP experiments in harsh radiation environments such as at Bell II or ILC.
Investigation of HV-CMOS sensors for use as a tracking detector in the ATLAS experiment at the upgraded LHC (HL-LHC) has recently been an active field of research. A potential candidate for a pixel detector built in Silicon-On-Insulator (SOI) technology has already been characterized in terms of radiation hardness to TID (Total Ionizing Dose) and charge collection after a moderate neutron irradiation. In this article we present results of an extensive irradiation hardness study with neutrons up to a fluence of 1x10e16 neq/cm2. Charge collection in a passive pixelated structure was measured by Edge Transient Current Technique (E-TCT). The evolution of the effective space charge concentration was found to be compliant with the acceptor removal model, with the minimum of the space charge concentration being reached after 5x10e14 neq/cm2. An investigation of the in-pixel uniformity of the detector response revealed parasitic charge collection by the epitaxial silicon layer characteristic for the SOI design. The results were backed by a numerical simulation of charge collection in an equivalent detector layout.
HV-CMOS pixel sensors are a promising option for the tracker upgrade of the ATLAS experiment at the LHC, as well as for other future tracking applications in which large areas are to be instrumented with radiation-tolerant silicon pixel sensors. We present results of testbeam characterisations of the $4^{mathrm{th}}$ generation of Capacitively Coupled Pixel Detectors (CCPDv4) produced with the ams H18 HV-CMOS process that have been irradiated with different particles (reactor neutrons and 18 MeV protons) to fluences between $1cdot 10^{14}$ and $5cdot 10^{15}$ 1-MeV-n$_textrm{eq}$/cm$^2$. The sensors were glued to ATLAS FE-I4 pixel readout chips and measured at the CERN SPS H8 beamline using the FE-I4 beam telescope. Results for all fluences are very encouraging with all hit efficiencies being better than 97% for bias voltages of $85,$V. The sample irradiated to a fluence of $1cdot 10^{15}$ n$_textrm{eq}$/cm$^2$ - a relevant value for a large volume of the upgraded tracker - exhibited 99.7% average hit efficiency. The results give strong evidence for the radiation tolerance of HV-CMOS sensors and their suitability as sensors for the experimental HL-LHC upgrades and future large-area silicon-based tracking detectors in high-radiation environments.
Charge collection measurements performed on heavily irradiated p-spray dofz pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes signal trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in ISE TCAD software can be tuned to produce a doubly-peaked electric field which describes the data reasonably well at two different fluences. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of signal trapping observed in the data.
In this paper we discuss results relevant to 3D Double-Side Double Type Column (3D-DDTC) pixel sensors fabricated at FBK (Trento, Italy) and oriented to the ATLAS upgrade. Some assemblies of these sensors featuring different columnar electrode configurations (2, 3, or 4 columns per pixel) and coupled to the ATLAS FEI3 read-out chip were irradiated up to large proton fluences and tested in laboratory with radioactive sources. In spite of the non optimized columnar electrode overlap, sensors exhibit reasonably good charge collection properties up to an irradiation fluence of 2 x 10**15 neq/cm2, while requiring bias voltages in the order of 100 V. Sensor operation is further investigated by means of TCAD simulations which can effectively explain the basic mechanisms responsible for charge loss after irradiation.
In this paper we discuss the measurement of charge collection in irradiated silicon pixel sensors and the comparison with a detailed simulation. The simulation implements a model of radiation damage by including two defect levels with opposite charge states and trapping of charge carriers. The modeling proves that a doubly peaked electric field generated by the two defect levels is necessary to describe the data and excludes a description based on acceptor defects uniformly distributed across the sensor bulk. In addition, the dependence of trap concentrations upon fluence is established by comparing the measured and simulated profiles at several fluences and bias voltages.
Mari Asano
,Kazuhiko Hara
,Daisuke Sekigawa
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(2015)
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"Characteristics of Non-Irradiated and Irradiated Double SOI Integration Type Sensor"
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Mari Asano
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