S. Ronchin

Double-Sided, Double-Type-Column 3-D Detectors: Design, Fabrication, and Technology Evaluation

We report on the latest results from the development of 3-D silicon radiation detectors at Fondazione Bruno Kessler of Trento (FBK), Italy (formerly ITC-IRST). Building on the results obtained from previous devices (3-D Single-Type-Column), a new detector concept has been defined, namely 3-D-DDTC (Double-sided Double-Type Column), which involves columnar electrodes of both doping types, etched from alternate wafer sides, stopping a short distance (d) from the opposite surface. Simulations prove that, if d is kept small with respect to the wafer thickness, this approach can yield charge collection properties comparable to those of standard 3-D detectors, with the advantage of a simpler fabrication process. Two wafer layouts have been designed with reference to this technology, and two fabrication runs have been performed. Technological and design aspects are reported in this paper, along with simulation results and initial results from the characterization of detectors and test structures belonging to the first 3-D-DDTC batch.

Test beam results of 3D silicon pixel sensors for the ATLAS upgrade

Results on beam tests of 3D silicon pixel sensors aimed at the ATLAS Insertable B-Layer and High Luminosity LHC (HL-LHC) upgrades are presented. Measurements include charge collection, tracking efficiency and charge sharing between pixel cells, as a function of track incident angle, and were performed with and without a 1.6 T magnetic field oriented as the ATLAS inner detector solenoid field. Sensors were bump-bonded to the front-end chip currently used in the ATLAS pixel detector. Full 3D sensors, with electrodes penetrating through the entire wafer thickness and active edge, and double-sided 3D sensors with partially overlapping bias and read-out electrodes were tested and showed comparable performance.

Fabrication of Novel MEMS Microgrippers by Deep Reactive Ion Etching With Metal Hard Mask

The fabrication of a novel class of microgrippers is demonstrated by means of bulk microelectromechanical systems (MEMS) technology using silicon on insulator wafer substrates and deep reactive ion etching. Hard masking is implemented to maximize the selectivity of the bulk etching using sputtered aluminum and aluminum–titanium thin films. The micro-roughness problem related to the use of metal mask is addressed by testing different mask combinations and etching parameters. The O2 flow, SF6 pressure, wafer temperature, and bias power are examined, and the effect of each parameter on micro-masking is assessed. Sidewall damage associated with the use of a metal mask is eliminated by interposing a dielectric layer between silicon substrate and metal mask. Dedicated comb-drive anchors are implemented to etch safely both silicon sides down to the buried oxide, and to preserve the wafer integrity until the final wet release of the completed structures. A first set of complete devices is realized and tested under electrical actuation. [2017-0039]

High-performance PIN photodiodes on TMAH thinned silicon wafers

The electro-optical characteristics of PIN photodiodes fabricated on high-resistivity silicon substrates locally thinned by bulk micromachining techniques are discussed. Experimental results and numerical simulations demonstrate that devices fabricated by the proposed approach have leakage current, quantum efficiency and speed performance comparable to the best commercially available Si PIN photodiodes, with the additional advantage of possible back-side illumination, making them suitable for the implementation of two-dimensional arrays having a read-out electronic chip connected to the front-side.

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.

Functional characterization of 3D-DDTC detectors fabricated at FBK-irst

We present selected results from the functional characterization of 3D-Double-Sided Double-Type Column (3D-DDTC) detectors fabricated at FBK, Trento. This technology features columnar electrodes etched perpendicularly to wafer surface and not passing all the way through the wafer thickness, stopping at short distance from the opposite surface. The detectors under investigation come from the first batch of these devices, made on n-type substrates. We report on the performances of microstrip sensors before and after irradiation up to 2×1015cm−2 fluences. The characterization has been carried out using a micrometer position resolved infrared laser scan and a 90Sr Beta source setup.

Performance evaluation of 3D-DDTC detectors on p-type substrates

We report on the electrical and functional characterization of 3D Double-side, Double-Type-Column (3D-DDTC) detectors fabricated on p-type substrates. Results relevant to detectors in the diode, strip and pixel configurations are presented, and demonstrate a clear improvement in the charge collection performance compared to the first prototypes of these detectors.

Functional characterization of a high-gain BJT radiation detector

n-p-n bipolar phototransistors have been designed and fabricated on high-resistivity silicon substrates. A technology featuring a double implant for the emitter allowed us to obtain a typical current gain of about 600. The device has been tested with /spl alpha/ particles from a /sup 239/Pu source, /spl beta/ particles from /sup 90/Sr, and X-rays from /sup 241/Am using a simple experimental setup, where the detector is directly connected to the oscilloscope. In the case of electrons, pulse heights of 100 mV have been observed, with pulse length of 50 /spl mu/s, measured on a load resistor in series to the emitter. The parameters driving the time performance have been measured, obtaining a good agreement with the electrical model of the device. We report on the functional characterization of the device, in particular the time response, the energy calibration, and the electronic noise measurement.

Radiation hardness and charge collection efficiency of lithium irradiated thin silicon diodes

Due to their low depletion voltage, even after high particle fluences, improved tracking precision and momentum resolution, and reduced material budget, thin substrates are one of the possible choices to provide radiation hard detectors for future high energy physics experiments. In the framework of the CERN RD50 Collaboration, we have developed PIN diode detectors on membranes obtained by locally thinning the silicon substrate by means of TMAH etching from the wafer backside. Diodes of different shapes and sizes have been fabricated on 50-/spl mu/m and 100-/spl mu/m thick membranes and tested, showing a low leakage current (of 300 nA/cm/sup 3/) and a very low depletion voltage (in the order of 1 V for the 50 /spl mu/m membrane) before irradiation. Radiation damage tests have been performed with 58 MeV lithium (Li) ions up to the fluence of 10/sup 14/ Li/cm/sup 2/ in order to determine the depletion voltage and leakage current density increase after irradiation. Charge collection efficiency tests carried out with a /spl beta//sup -/ particle source have been performed on both nonirradiated devices and samples irradiated up to 1.8/spl times/10/sup 13/ Li/cm/sup 2/. Results reported here confirm the advantages of thinned diodes with respect to standard 300-/spl mu/m thick devices in terms of low depletion voltage and high charge collection efficiency.

An improved termination structure for silicon radiation detectors with all-P-type multiguard and cut-line implants

A junction termination structure for silicon radiation detectors is investigated, featuring all-p-type multiguard and scribe-line implants, with metal field-plates providing complete coverage of the oxide upper surface above nonimplanted regions. The sensitive interface between oxide and n-type substrate is thus electrostatically screened from the external environment, resulting in improved long-term stability of the device and excellent insensitivity to ambient conditions both before and after X-ray and neutron irradiations. Careful design of the multiguard layout enables high-voltage operation to be achieved. With respect to a previously proposed structure, the adoption of alternate outward and inward field plates between adjacent rings allows a significant improvement in the voltage handling capability.