A 1-μW radiation-hard front-end in a 0.18-μm CMOS process for the MALTA2 monolithic sensor

In this article, a low-power, radiation-hard front-end circuit for monolithic pixel sensors, designed to meet the requirements of low noise and low pixel-to-pixel variability, the key features to achieve high detection efficiencies, is presented. The sensor features a small collection electrode to achieve a small capacitance (<5 fF) and allows full CMOS in-pixel circuitry. The circuit is implemented in the 180-nm CMOS imaging technology from the TowerJazz foundry and integrated into the MALTA2 chip, which is part of a development that targets the specifications of the outer pixel layer of the ATLAS Inner Tracker upgrade at the LHC. One of the main challenges for monolithic sensors is a radiation hardness up to 1015 1-MeV neq/cm2 non-ionizing energy loss (NIEL) and 80 Mrad total ionizing dose (TID) required for this application. Tests up to 3⋅1015 1-MeV neq/cm2 and 100 Mrad were performed on the MALTA2 sensor and front-end circuit, which still show good performance even after these levels of irradiation, promising for even more demanding applications such as the future experiments at the high-luminosity large hadron collider (HL-LHC)

Studies for low mass, large area monolithic silicon pixel detector modules using the MALTA CMOS pixel chip

International audienceThe MALTA monolithic silicon pixel sensors have been used to study dicing and thinning of monolithic silicon pixel detectors for large area and low mass modules. Dicing as close as possible to the active circuitry will allow to build modules with very narrow inactive regions between the sensors. Inactive edge regions of less than 5μ m to the electronic circuitry could be achieved for 100μ m thick sensors. The MALTA chip (Cardella et al., 2019) also offers the possibility to transfer data and power directly from chip to chip. Tests have been carried out connecting two MALTA chips directly using ultrasonic wedge wire bonding. Results from lab tests show that the data accumulated in one chip can be transferred via the second chip to the readout system, without the need of a flexible circuit to route the signals. The concept of chip to chip data and power transfer to achieve low mass modules has also been studied on prototype wafers using Cu-stud interconnection bridges. First results are presented, outlining technical challenges and possible future steps to achieve a low mass large area monolithic pixel sensor module

The MALTA CMOS pixel detector prototype for the ATLAS Pixel ITk

The ATLAS experiment is planning a major upgrade of its tracking detectors, both strip and pixel, to take full advantage of the High Luminosity LHC. A novel Monolithic Active Pixel Sensor based on 180 nm TowerJazz CMOS imaging technology, dubbed MALTA, has been designed to meet the radiation hardness requirements (1.5x10$^{15}$ 1 MeV $n_{eq}$/cm$^{2}$) of the outer barrel layers of the ITk Pixel detector. MALTA combines low noise (ENC<20 e$^{-}$) and low power operation (1 $\mu$W/pixel) with a fast signal response (25 ns bunch crossing) in small pixel size (36.4x36.4 $\mu$m$^{2}$), with a novel high-speed asynchronous readout architecture to cope with the high hit-rates expected at HL-LHC. Extensive lab testing and characterisation in particle beam tests have been conducted on this design and compared with previous prototypes of the same technology. An overview of the sensor technology and readout architecture are presented along with the preliminary results from laboratory tests, radioactive source tests and beam tests

CMOS Monolithic Pixel Sensors based on the Column-Drain Architecture for the HL-LHC Upgrade

International audienceDepleted 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 Hadron Collider (HL-LHC)

Radiation hardness and timing performance in MALTA monolithic pixel sensors in TowerJazz 180 nm

The MALTA family of depleted monolithic pixel sensors produced in TowerJazz 180 nm CMOS technology target radiation hard applications for the HL-LHC and beyond. Several process modifications and front-end improvements have resulted in radiation hardness >10$^{15}$ 1 MeV n$_{eq}$/cm$^{2}$ and time resolution below 2 ns, with uniform charge collection and efficiency across the pixel of size 36.4 × 36.4 µm$^{2}$ with small collection electrode. This contribution will present the comparison of samples produced on high-resistivity epitaxial silicon with Czochralski substrates, before and after neutron irradiation, and results from MALTA2 with a new cascoded front-end flavour that further reduces the RTS noise

Measurement of the relative response of small-electrode CMOS sensors at Diamond Light Source

This paper outlines the results of investigations into the effects of radiation damage in the mini-MALTA depleted monolithic pixel sensor prototype. Measurements were carried out at Diamond Light Source using a micro-focus X-ray beam, which scanned across the surface of the device in 2 μm steps. This allowed the in-pixel photon response to be measured directly with high statistics. Three pixel design variations were considered: one with the standard continuous n$^{−}$ layer layout and front-end, and extra deep p-well and n$^{−}$ gap designs with a modified front-end. Five chips were measured: one unirradiated, one neutron irradiated, and three proton irradiated. The standard design showed a decrease of 12% in pixel response after irradiation to 1e15 n$_{eq}$∕cm$^{2}$ . For the two new designs the pixel response did not decrease significantly after irradiation. A decrease of pixel response at high biasing voltages was observed. The charge sharing in the chip was quantified and found to be in agreement with expectations

A 1μ\muW Radiation-Hard Front-End in a 0.18-μ\mum CMOS Process for the MALTA2 Monolithic Sensor

In this article, a low-power, radiation-hard front-end circuit for monolithic pixel sensors, designed to meet the requirements of low noise and low pixel-to-pixel variability, the key features to achieve high detection efficiencies, is presented. The sensor features a small collection electrode to achieve a small capacitance (15 1-MeV $\text {n}_{\text {eq}}/\text {cm}^{{2}}$ non-ionizing energy loss (NIEL) and 80 Mrad total ionizing dose (TID) required for this application. Tests up to ${3} \cdot {10}^{15}$ 1-MeV $\text {n}_{\text {eq}}/\text {cm}^{{2}}$ and 100 Mrad were performed on the MALTA2 sensor and front-end circuit, which still show good performance even after these levels of irradiation, promising for even more demanding applications such as the future experiments at the high-luminosity large hadron collider (HL-LHC)

Radiation hardness and timing performance in MALTA monolithic pixel sensors in TowerJazz 180 nm

The MALTA family of depleted monolithic pixel sensors produced in TowerJazz 180 nm CMOS technology target radiation hard applications for the HL-LHC and beyond. Several process modifications and front-end improvements have resulted in radiation hardness &gt;1015 1 MeV neq/cm2 and time resolution below 2 ns, with uniform charge collection and efficiency across the pixel of size 36.4 × 36.4 µm2 with small collection electrode. This contribution will present the comparison of samples produced on high-resistivity epitaxial silicon with Czochralski substrates, before and after neutron irradiation, and results from MALTA2 with a new cascoded front-end flavour that further reduces the RTS noise