R. Mendicino

Development of a new generation of 3D pixel sensors for HL-LHC

Abstract This paper covers the main technological and design aspects relevant to the development of a new generation of thin 3D pixel sensors with small pixel size aimed at the High-Luminosity LHC upgrades.

The PixFEL project: development of advanced X-ray pixel detectors for application at future FEL facilities

The PixFEL project aims to develop an advanced X-ray camera for imaging suited for the demanding requirements of next generation free electron laser (FEL) facilities. New technologies can be deployed to boost the performance of imaging detectors as well as future pixel devices for tracking. In the first phase of the PixFEL project, approved by the INFN, the focus will be on the development of the microelectronic building blocks, carried out with a 65 nm CMOS technology, implementing a low noise analog front-end channel with high dynamic range and compression features, a low power ADC and high density memory. At the same time PixFEL will investigate and implement some of the enabling technologies to assembly a seamless large area X-ray camera composed by a matrix of multilayer four-side buttable tiles. A pixel matrix with active edge will be developed to minimize the dead area of the sensor layer. Vertical interconnection of two CMOS tiers will be explored to build a four-side buttable readout chip with small pixel pitch and all the on-board required functionalities. The ambitious target requirements of the new pixel device are: single photon resolution, 1 to 104 photons @ 1 keV to 10 keV input dynamic range, 10-bit analog to digital conversion up to 5 MHz, 1 kevent in-pixel memory and 100 μm pixel pitch. The long term goal of PixFEL will be the development of a versatile X-ray camera to be operated either in burst mode (European XFEL), or in continuous mode to cope with the high frame rates foreseen for the upgrade phase of the LCLS-II at SLAC.

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.

Design and testing of an innovative slim-edge termination for silicon radiation detectors

Silicon detectors with reduced or no dead volume along the edges have been attracting a lot of interest in the past few years in many different fields. High Energy Physics (HEP) experiments are demanding this feature to ease the assembly of the innermost tracking layers, where space and material budget are usually a concern. At the same time, other applications like X-Ray imaging, are starting to use matrixes of silicon detectors to cover increasingly larger areas and, in order to do so in a seamless way, minimum edge extension is required. In this paper we report on the design and testing of a new edge termination for silicon 3D detectors able to reduce the edge extension to about 50 μm without increasing the fabrication complexity. In addition, the same edge termination can also be applied to planar detectors with little additional process complexity.

Characterization of new FBK double-sided 3D sensors with improved breakdown voltage

We report on the characterization of a new version of double-sided 3D sensors fabricated at FBK (Trento, Italy). Owing to a modified design and improved technology, the new devices feature a sizable increase of the breakdown voltage with respect to the ones previously fabricated at FBK. Before irradiation, the breakdown voltage is in the range from ~70 V to ~ 130 V, after irradiation up to large fluences, it is typically larger than 200 V, that is high enough for proper 3D sensor biasing even after very high radiation fluences like those foreseen at the High Luminosity LHC.

Design and TCAD simulations of planar active-edge pixel sensors for future XFEL applications

We report on the design and TCAD simulations of planar active-edge pixel sensors within the INFN PixFEL project. These devices are intended as one of the building blocks for the assembly of a multilayer, four-side buttable tile for X-ray imaging applications in future Free Electron Laser facilities. The requirements in terms of very wide dynamic range and tolerance to extremely high ionizing radiation doses call for high operation voltages. A comprehensive TCAD simulation study is presented, aimed at the best trade-offs between the minimization of the edge region size and the sensor breakdown voltage.

Novel 3D silicon sensors for neutron detection

In this paper we report a novel 3D sensor structure to be used as a neutron detector in combination with an organic converter material based on polysiloxane. The first prototypes of the proposed device are presented, with emphasis on the experimental characterization. Selected results from the functional tests (with alpha particle source and pulsed laser scans) are discussed with the aid of TCAD simulations.

Hybrid detectors of neutrons based on 3D silicon sensors with PolySiloxane converter

We report on the first prototypes of hybrid detectors for neutrons from the INFN HYDE project. Devices consist of 3D silicon sensors coupled to PolySiloxane-based converters. The sensor design and fabrication technology are presented, along with initial results from the functional characterization of the devices in response to radioactive sources and neutron beams of different energies.

Hybrid detectors for neutrons combining phenyl-polysiloxanes with 3D silicon detectors

We report on the initial results of a research project aimed at the development hybrid detectors for fast neutrons by combining a phenyl-polysiloxane-based converter with a 3D silicon detector. To this purpose, new 3D sensor structures have been designed, fabricated and electrically tested, showing low depletion voltage and good leakage current. Moreover, the radiation detection capability of 3D sensors was tested by measuring the signals recorded from alpha particles, gamma rays, and pulsed lasers. The converter has been poured into the 3D cavities with excellent coupling, as confirmed by cross-section SEM analyses. Preliminary tests with neutrons have been carried out on the first hybrid detector prototypes at the CN accelerator of INFN LNL. The device design and technology are discussed, along with the first results from the electrical and functional characterization.

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.