Heavily irradiated N-in-p thin planar pixel sensors with and without active edges

S Terzo,R Nisius,A Macchiolo,H G Moser,R H Richter,P Weigell,L Andricek

doi:10.1088/1748-0221/9/05/c05023

S Terzo, R Nisius + Show 5 more

Open Access

https://doi.org/10.1088/1748-0221/9/05/c05023

Copy DOI

Abstract

We present the results of the characterization of silicon pixel modules employing n-in-pplanar sensors with an active thickness of 150 μm, produced at MPP/HLL, and 100–200 μm thin active edge sensor devices, produced at VTT in Finland.These thin sensors are designed as candidates for the ATLAS pixel detector upgrade to be operated at the HL-LHC, as they ensure radiation hardness at high fluences. They are interconnected to theATLAS FE-I3 and FE-I4 read-out chips.Moreover, the n-in-p technology only requires a single side processing and thereby it is a cost-effectivealternative to the n-in-n pixel technology presently employed in the LHC experiments.High precision beam test measurements of the hit efficiency have been performed on thesedevices both at the CERN SpS and at DESY, Hamburg. We studied the behavior of thesesensors at different bias voltages and different beam incident angles up to the maximum oneexpected for the new Insertable B-Layer of ATLAS and for HL-LHC detectors.Results obtained with 150 μm thin sensors, assembled with the new ATLAS FE-I4 chip andirradiated up to a fluence of 4 × 1015 neq/cm2, show that they are excellent candidates for largerradii of the silicon pixel tracker in the upgrade of the ATLAS detector at HL-LHC. In addition, the active edge technologyof the VTT devices maximizes the active area of the sensorand reduces the material budget to suit the requirements for the innermost layers.The edge pixel performance of VTT modules has been investigated at beam test experiments andthe analysis after irradiation up to a fluence of 5 × 1015 neq/cm2 has been performed using radioactive sources in the laboratory.

Highlights

Thin active edge pixels produced at VTTN-in-p planar pixel sensors with active edges have been produced at VTT Finland, on p-type Float Zone (FZ) silicon with an initial resistivity of 10 kΩ cm, and on Magnetic Czochralski (MCz) silicon with orientation 100 and initial resistivity of 2 kΩ cm
A production of 150 μm thin n-in-p silicon sensors designed at the Max-Planck-Institut für Physik has been carried out by the Max-Planck-Gesellschaft Halbleiterlabor (MPG-HLL) on 6 inch wafer of p-type Float Zone (FZ) silicon
N-in-p planar pixel sensors with active edges have been produced at VTT Finland, on p-type FZ silicon with an initial resistivity of 10 kΩ cm, and on Magnetic Czochralski (MCz) silicon with orientation 100 and initial resistivity of 2 kΩ cm

Summary

Thin active edge pixels produced at VTT

N-in-p planar pixel sensors with active edges have been produced at VTT Finland, on p-type FZ silicon with an initial resistivity of 10 kΩ cm, and on Magnetic Czochralski (MCz) silicon with orientation 100 and initial resistivity of 2 kΩ cm. Two different slim edge designs have been implemented characterized by a distance between the last pixel implant and the sensor border of 50 μm with just one floating guard ring, or a 125 μm distance when employing a bias ring structure. Figure 5: breakdown voltages are between 100 V and 130 V and the full depletion voltage is around 15 V as expected from the high bulk resistivity In figure 6 the hit efficiency is shown as a function of the distance from the last pixel column for the two edge structures of 100 μm thin FZ sensors. For the 50 μm edge design a particle traversing this border area can be detected on the last pixel implant with a measured hit efficiency of 84+−914%. A lower hit efficiency of 77±1% is observed only in the 15 μm between the last pixel implant and the bias ring

Charge collection studies after irradiation

Findings

Conclusions