Development of the monolithic "MALTA" CMOS sensor for the ATLAS ITK outer pixel layer

Abstract

Depleted Monolithic Active Pixel Sensors (DMAPS) are an option for the outermost layer of the upgraded ATLAS ITk Pixel Detector at the CERN LHC. Two large size DMAPS named TJ MALTA and TJ Monopix were produced in a 180 nm CMOS imaging process in a small collection electrode design. The TJ MALTA chip combines a low power front end with a novel matrix readout design to achieve a low power consumption of < 80 mW/cm 2 . Threshold values of ≈ 250 e − with a dispersion of ≈ 30 e − and an ENC of < 10 e − can be achieved before irradiation which is consistent with the results from TJ Monopix. Test beam measurements indicate an average efficiency of 96 % before irradiation, with the inefficiency mainly due to a non fully functional masking scheme, forcing operation at relatively high thresholds. After neutron irradiation to 1 × 10 15 n eq /cm 2 the efficiency in pixel centres is retained, but it is reduced in pixel corners. A proposal to improve charge collection in the corners is backed up by TCAD simulations and promises an improved performance with small modifications.

Snowmass 2021 White Paper: Electron Ion Collider for High Energy Physics

“…The outer radius of the FST is up to 45 cm to cover pseudorapidity from 1 to 3. Three silicon technologies, LGAD [533,534], MALTA [535][536][537] and the ALICE ITS-3 type sensor [538,539], are in consideration. The FST will implement two of these technologies to provide both good spatial and timing resolutions.…”

Overview of CMOS Sensors for Future Tracking Detectors

“…In the former architecture, the address and time stamp is read out in each pixel and then the data are moved selectively to the chip periphery, whereas in the latter architecture the binary data of each pixel are moved immediately to the device periphery and processed there upon a trigger arrival. Another type of asynchronous readout architecture has been also implemented in the TJ-Malta device [13]. These readout architectures are being tested to optimize the integration, cross-talk and speed of the device.…”

“…Large fill-factor structures have been produced in LFoundry Srl [14], ams AG [15] and TSI Semiconductors Corp [16], in the framework of the ATLAS upgrade and the Mu3e experiments, like the H35Demo device [17], implemented in the ams 350 nm process, the LF-Monopix device [11], implemented in the LFoundry 150 nm process, or the MuPix7 and MuPix8 devices [9], implemented in the ams and TSI 180 nm processes, to mention a few ones. Regarding the small fill-factor structures, some devices of this type have been also produced in TowerJazz Ltd. [18] following the TJ 180 nm process as the TJ-Monopix device [11] or the TJ-Malta device [13]. A special type of CMOS technology, the High Voltage Silicon On Insulator, is also available at X-FAB Semiconductor Foundries AG [19], several devices have been implemented in the XFAB 180 nm process, like the XTB01 device [20].…”

Progress on the radiation tolerance of CMOS Monolithic Active Pixel Sensors

“…The MALTA sensor [116][117][118] combines the sensing elements of the above mentioned Investigator with a fast readout electronics. It is equipped with 512 × 512 pixels of 36.4 × 36.4 µm 2 pitch.…”

“…First test of the device show that the sensor features a non-negligible non-gaussian tail in the noise distribution, which was attributed to the presence of RTS [117] in some pixels. As those pixels could not be masked individually, defining a good threshold setting was problematic.…”