Abstract

Depleted Monolithic Active Pixel Sensors (DMAPS) constitute a promising low cost alternative for the outer layers of the ATLAS experiment Inner Tracker (ITk). Realizations in modern, high resistivity CMOS technologies enhance their radiation tolerance by achieving substantial depletion of the sensing volume. Two DMAPS prototypes that use the same "column-drain" readout architecture and are based on different sensor implementation concepts named LF-Monopix and TJ-Monopix have been developed for the High Luminosity upgrade of the Large Hardon Collider (HL-LHC). LF-Monopix was fabricated in the LFoundry 150 nm technology and features pixel size of $50x250~\mu m^{2}$ and large collection electrode opted for high radiation tolerance. Detection efficiency up to 99\% has been measured after irradiation to $1\cdot10^{15}~n_{eq}/cm^{2}$. TJ-Monopix is a large scale $(1x2~cm^{2})$ prototype featuring pixels of $36x40~\mu m^{2}$ size. It was fabricated in a novel TowerJazz 180 nm modified process that enables full depletion of the sensitive layer, while employing a small collection electrode that is less sensitive to crosstalk. The resulting small sensor capacitance ($<=3~fF$) is exploited by a compact, low power front end optimized to meet the 25ns timing requirement. Measurement results demonstrate the sensor performance in terms of Equivalent Noise Charge (ENC) $\approx11e^{-}$, threshold $\approx300~e^-$, threshold dispersion $\approx30~e^-$ and total power consumption lower than $120~mW/cm^2$.

Highlights

  • IntroductionMonolithic Active Pixel Sensors (MAPS) constitute an attractive alternative in high energy physics experiments as the building blocks of vertex detectors in high precision tracking applications

  • Monolithic Active Pixel Sensors (MAPS) constitute an attractive alternative in high energy physics experiments as the building blocks of vertex detectors in high precision tracking applications. Their prominent advantage stems from the fact that the manufactured devices contain both the sensor and the front end electronics in the same silicon crystal and are ready to be used without the need for the expensive and labor-intensive process of fine pitch bump-bonding

  • Depleted MAPS (DMAPS) prototypes manufactured in different technologies have been reported with encouraging results regarding the sensor radiation tolerance [4,5,6,7]

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Summary

Introduction

Monolithic Active Pixel Sensors (MAPS) constitute an attractive alternative in high energy physics experiments as the building blocks of vertex detectors in high precision tracking applications. Their prominent advantage stems from the fact that the manufactured devices contain both the sensor and the front end electronics in the same silicon crystal and are ready to be used without the need for the expensive and labor-intensive process of fine pitch bump-bonding. The first prototype, called LF-Monopix, is based on a large collection electrode and is manufactured in the LFoundry 150 nm HV-CMOS process. Full functionality of TJ-Monopix after irradiation is demonstrated here for the first time and its performance is evaluated by laboratory and radioactive source measurement results reported in this work

Sensor implementation
Chip architecture
LF-Monopix chip design
TJ-Monopix chip design
LF-Monopix
TJ-Monopix
Findings
Conclusion
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