A. Morozzi

Radiation hardness of three-dimensional polycrystalline diamond detectors

The three-dimensional concept in particle detection is based on the fabrication of columnar electrodes perpendicular to the surface of a solid state radiation sensor. It permits to improve the radiation resistance characteristics of a material by lowering the necessary bias voltage and shortening the charge carrier path inside the material. If applied to a long-recognized exceptionally radiation-hard material like diamond, this concept promises to pave the way to the realization of detectors of unprecedented performances. We fabricated conventional and three-dimensional polycrystalline diamond detectors, and tested them before and after neutron damage up to 1.2 ×1016 cm−2, 1 MeV-equivalent neutron fluence. We found that the signal collected by the three-dimensional detectors is up to three times higher than that of the conventional planar ones, at the highest neutron damage ever experimented.

Combined Bulk and Surface Radiation Damage Effects at Very High Fluences in Silicon Detectors: Measurements and TCAD Simulations

In this work we propose a new combined TCAD radiation damage modelling scheme, featuring both bulk and surface radiation damage effects, for the analysis of silicon detectors aimed at the High Luminosity LHC. In particular, a surface damage model has been developed by introducing the relevant parameters (NOX, NIT) extracted from experimental measurements carried out on p-type substrate test structures after gamma irradiations at doses in the range 10-500 Mrad(Si). An extended bulk model, by considering impact ionization and deep-level cross-sections variation, was included as well. The model has been validated through the comparison of the simulation findings with experimental measurements carried out at very high fluences (2 × 1016 1 MeV equivalent n/cm2) thus fostering the application of this TCAD approach for the design and optimization of the new generation of silicon detectors to be used in future HEP experiments.

Measurements and TCAD simulations of bulk and surface radiation damage effects in silicon detectors

In this work we propose the application of a radiation damage model based on the introduction of deep level traps/recombination centers suitable for device level numerical simulation of radiation detectors at very high fluences (e.g. 1÷2×1016 1-MeV equivalent neutrons per square centimeter) combined with a surface damage model developed by using experimental parameters extracted from measurements from gamma irradiated p-type dedicated test structures.

Numerical simulation of ISFET structures for biosensing devices with TCAD tools

BackgroundIon Sensitive Field Effect Transistors (ISFETs) are one of the primitive structures for the fabrication of biosensors (BioFETs). Aiming at the optimization of the design and fabrication processes of BioFETs, the correlation between technological parameters and device electrical response can be obtained by means of an electrical device-level simulation. In this work we present a numerical simulation approach to the study of ISFET structures for bio-sensing devices (BioFET) using Synopsys Sentaurus Technology Computer-Aided Design (TCAD) tools.MethodsThe properties of a custom-defined material were modified in order to reproduce the electrolyte behavior. In particular, the parameters of an intrinsic semiconductor material have been set in order to reproduce an electrolyte solution.By replacing the electrolyte solution with an intrinsic semiconductor, the electrostatic solution of the electrolyte region can therefore be calculated by solving the semiconductor equation within this region.ResultsThe electrostatic behaviour (transfer characteristics) of a general BioFET structure has been simulated when the captured target number increases from 1 to 10. The ID current as a function of the VDS voltage for different positions of a single charged block and for different values of the reference electrode have been calculated.The electrical potential distribution along the electrolyte-insulator-semiconductor structure has been evaluated for different molar concentrations of the electrolyte solution.ConclusionsWe presented a numerical simulation approach to the study of Ion-Sensitive Field Effect Transistor (ISFET) structures for biosensing devices (BioFETs) using the Synopsys Sentaurus Technology Computer-Aided Design (TCAD) tools.A powerful framework for the design and optimization of biosensor has been devised, thus helping in reducing technology development time and cost. The main finding of the analysis of a general reference BioFET shows that there is no linear relationship between the number of charges and the current modulation. Actually, there is a strong position dependent effect: targets localized near the source region are most effective with respect to targets localized near the drain region. In general, even randomly distributed targets are more efficient with respect to locally grouped targets on the current modulation. Moreover, for the device at hand, a small positive biasing of the electrolyte solution, providing that the transistor goes on, will result in a greater enhancement of the current levels, still retaining a good sensitivity but greatly simplifying the operations of a real device.

Effects of Interface Donor Trap States on Isolation Properties of Detectors Operating at High-Luminosity LHC

The very high radiation fluences expected at the high-luminosity large hadron collider (LHC) impose new challenges in terms of design of radiation resistant silicon detectors. The choice to use p-type substrates to improve the charge collection efficiency involves an optimization of the strip isolation to interrupt the inversion layer between the

Radiation damage effects on p-type silicon detectors for high-luminosity operations: Test and modeling

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A combined surface and bulk TCAD damage model for the analysis of radiation detectors operating at HL-LHC fluences

implants, limiting the breakdown voltage. To this purpose, TCAD modeling and simulation schemes, already developed and validated at typical LHC fluences have to be adapted to take into account effects usually neglected at lower fluences. To better understand in a comprehensive framework, the complex and articulated phenomena related to bulk and surface radiation damage, measurements on test structures and sensors, as well as TCAD simulations related to bulk, surface and interface effects, have been carried out. In particular, we have studied the properties of the SiO2 layer and of the Si-SiO2 interface, using MOS capacitors and gate-controlled diodes (gated diodes) manufactured by different vendors on a high-resistivity p-type silicon before and after irradiation with X-rays in the range from 50 krad to 10 Mrad. In this paper, we present the results of the experimental characterizations as well as the simulation findings, in order to analyze the effects of the interface traps on the strip isolation. This analysis helps us to validate the model and to identify the most sensitive technological and design parameters to be optimized for the design of advanced 2-D and 3-D silicon radiation detectors.

Simulation and test of Silicon-on-Diamond sensors for particle detection

The very high radiation fluences expected at the High Luminosity LHC (HL-LHC) impose new challenges in terms of design of effective silicon radiation detectors. To this purpose, TCAD modeling and simulation schemes, already developed and validated at typical LHC fluences, have to be adapted to take into account new effects usually neglected at lower fluences. To better understand in a comprehensive framework these complex and articulated phenomena, measurements on test structures and sensors, as well as TCAD simulations related to surface and interface effects, have been carried out. In particular, we have studied the properties of the SiO2 layer and of the Si-SiO2 interface, using MOS capacitors and gate-controlled diodes (gated diodes) manufactured on high-resistivity p-type silicon before and after irradiation with X-ray in the range from 50 krad to 10 Mrad. In this work we present the results of the experimental characterizations as well as the simulation findings, in order to validate the model and to identify the most sensitive technological and design parameters to be optimized for the design of advanced 2D and 3D silicon radiation detectors.

A TCAD modeling approach for diamond particle detectors: Simulation and test

In this work we present the development and the application of a new TCAD modelling scheme to simulate the effects of radiation damage on silicon radiation detectors at the very high fluence levels expected at High Luminosity LHC (up to 2 × 1016 1MeV n/cm2). In particular, we propose a combined approach for the analysis of the surface effects (oxide charge build-up and interface trap states introduction) as well as bulk effects (deep level traps and/or recombination centers introduction). Experimental measurements have been carried out aiming at: i) extraction from simple test structures of relevant parameters to be included within the TCAD model and ii) validation of the new modelling scheme through comparison with measurements of different test structures (e.g. different technologies) before and after irradiation. The good agreements between experimental measurements and simulation findings foster the suitability of the TCAD modelling approach as a predictive tool for investigating the radiation detector behavior at different fluences and operating conditions. This would allow the design and optimization of innovative 3D and planar silicon detectors for future HL-LHC High Energy Physics experiments.

Evaluation of a 3D diamond detector for medical radiation dosimetry

A laser bonding technique has been developed recently to create an innovative material based on a silicon/diamond interface. In this work, we propose the development and the application of a numerical model for TCAD simulations of poly-crystalline diamond conceived for Silicon-on-Diamond (SoD) sensors to be used, e.g., as particle detectors in High Energy Physics (HEP) experiments. The model is based on the introduction of an articulated, yet physically based, picture of deep-level defects acting as a recombination centers and/or trap states. The modelling scheme has been validated by comparing the simulation findings with experimental measurements carried out on real devices featuring a thinned CMOS Active Pixel Sensor chip bonded to a poly-crystalline diamond substrate. Eventually, this technique could foster the exploration of innovative semiconductor devices conjugating the properties of diamond substrates and the capabilities of CMOS electronics.