Performance of the MALTA Telescope

MALTA is part of the Depleted Monolithic Active Pixel sensors designed in Tower 180nm CMOS imaging technology. A custom telescope with six MALTA planes has been developed for test beam campaigns at SPS, CERN, with the ability to host several devices under test. The telescope system has a dedicated custom readout, online monitoring integrated into DAQ with realtime hit map, time distribution and event hit multiplicity. It hosts a dedicated fully configurable trigger system enabling to trigger on coincidence between telescope planes and timing reference from a scintillator. The excellent time resolution performance allows for fast track reconstruction, due to the possibility to retain a low hit multiplicity per event which reduces the combinatorics. This paper reviews the architecture of the system and its performance during the 2021 and 2022 test beam campaign at the SPS North Area

Recent results with radiation-tolerant TowerJazz 180 nm MALTA sensors

To achieve the physics goals of future colliders, it is necessary to develop novel, radiation-hard silicon sensors for their tracking detectors. We target the replacement of hybrid pixel detectors with Depleted Monolithic Active Pixel Sensors (DMAPS) that are radiation-hard, monolithic CMOS sensors. We have designed, manufactured and tested the MALTA series of sensors, which are DMAPS in the 180 nm TowerJazz CMOS imaging technology. MALTA have a pixel pitch well below current hybrid pixel detectors, high time resolution (<2 ns) and excellent charge collection efficiency across pixel geometries. These sensors have a total silicon thickness of between 50–300 m, implying reduced material budgets and multiple scattering rates for future detectors which utilize such technology. Furthermore, their monolithic design bypasses the costly stage of bump-bonding in hybrid sensors and can substantially reduce detector costs. This contribution presents the latest results from characterization studies of the MALTA2 sensors, including results demonstrating the radiation tolerance of these sensors

Performance of the MALTA telescope

MALTA is part of the Depleted Monolithic Active Pixel sensors designed in Tower 180 nm CMOS imaging technology. A custom telescope with six MALTA planes has been developed for test beam campaigns at SPS, CERN, with the ability to host several devices under test. The telescope system has a dedicated custom readout, online monitoring integrated into DAQ with realtime hit map, time distribution and event hit multiplicity. It hosts a dedicated fully configurable trigger system enabling to trigger on coincidence between telescope planes and timing reference from a scintillator. The excellent time resolution performance allows for fast track reconstruction, due to the possibility to retain a low hit multiplicity per event which reduces the combinatorics. This paper reviews the architecture of the system and its performance during the 2021 and 2022 test beam campaign at the SPS North Area

Radiation hardness of MALTA2 monolithic CMOS imaging sensors on Czochralski substrates

MALTA2 is the latest full-scale prototype of the MALTA family of Depleted Monolithic Active Pixel Sensors (DMAPS) produced in Tower Semiconductor 180 nm CMOS sensor imaging technology. In order to comply with the requirements of high energy physics (HEP) experiments, various process modifications and front-end changes have been implemented to achieve low power consumption, reduce random telegraph signal (RTS) noise, and optimise the charge collection geometry. Compared to its predecessors, MALTA2 targets the use of a high-resistivity, thick Czochralski (Cz) substrates in order to demonstrate radiation hardness in terms of detection efficiency and timing resolution up to 3 × 1015 1 MeV neq/cm2 with backside metallisation to achieve good propagation of the bias voltage. This manuscript shows the results that were obtained with non-irradiated and irradiated MALTA2 samples on Cz substrates from the CERN SPS test beam campaign from 2021 to 2023 using the MALTA telescope

TWEPP 2021 Topical Workshop on Electronics for Particle Physics

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 up to 2e15 n/cm2 and time resolution below 2 ns, with uniform charge collection efficiency across the Pixel of size 36.4 x 36.4 um2 with a 3 um2 electrode size. This contribution will present the results from new cascoded front-end flavour that further reduces the RTS noise and improves the threshold reach, and the comparison of samples produced on high-resistivity epitaxial silicon with Czochralski substrates

On the Accuracy of the Cox-Strack Equation and Method for Contact Resistivity Determination

The Cox-Strack method is commonly applied to assess the contact resistivity between a metal and a semiconductor since the 1960s, while the underlying assumptions have not yet been rigorously assessed. In this article, a combination of finite-element modeling and mathematical analysis is used to investigate the accuracy of the conventional Cox-Strack equation for generic metal-semiconductor junctions. A systematic error in the spreading resistance equation is quantified, and alternative, more accurate equations are presented. Furthermore, it is shown that commonly used experimental configurations can lead to highly overestimated contact resistivities. Guidelines are formulated for accurate extraction of the contact resistivity from the Cox-Strack measurements

MALTA3: Concepts for a new radiation tolerant sensor in the TowerJazz 180 nm technology

The upgrade of the MALTA DMAPS designed in Tower 180 nm CMOS Imaging process will implement the numerous modifications, as well as front-end changes in order to boost the charge collection efficiency after the targeted fluence of 1x10$^{15}$ 1 MeV$n_{eq}$/cm$^{2}$. The effectiveness of these changes have been demonstrated in recent measurements with a small-scale Mini-MALTA demonstrator chip. Multiple changes in the digital periphery are proposed: The asynchronous address generator will be revised to provide more control over the pulse length. The Synchronization memory will be upgraded with the goal of achieving a sub-nanosecond timing resolution. Serial chip to chip data transfer will be prototyped, in order to gauge the plausibility of implementation on a future full sized chip. Apart from these changes, research of the overall sensor architecture will be discussed as well

MALTA3: concepts for a new radiation tolerant sensor in the TowerJazz 180 nm technology

The upgrade of the MALTA DMAPS designed in Tower 180 nm CMOS Imaging process will implement the numerous modifications, as well as front-end changes in order to boost the charge collection efficiency after the targeted fluence of 1x10^15 1 MeVneq/cm2. The effectiveness of these changes have been demonstrated in recent measurements with a small-scale Mini-MALTA demonstrator chip. Multiple changes in the digital periphery are proposed: The asynchronous address generator will be revised to provide more control over the pulse length. The Synchronisation memory will be upgraded with the goal of achieving a sub-nanosecond timing resolution. Serial chip to chip data transfer will be prototyped, in order to gauge the plausibility of implementation on a future full sized chip. Apart from these changes, research of the overall sensor architecture will be discussed as well

Recent results with radiation-tolerant TowerJazz 180 nm MALTA sensors

To achieve the physics goals of future colliders, it is necessary to develop novel, radiation-hard silicon sensors for their tracking detectors. We target the replacement of hybrid pixel detectors with Depleted Monolithic Active Pixel Sensors (DMAPS) that are radiation-hard, monolithic CMOS sensors. We have designed, manufactured and tested the MALTA series of sensors, which are DMAPS in the 180 nm TowerJazz CMOS imaging technology. MALTA have a pixel pitch well below current hybrid pixel detectors, high time resolution (<2ns) and excellent charge collection efficiency across pixel geometries. These sensors have a total silicon thickness of between 50–300 μm, implying reduced material budgets and multiple scattering rates for future detectors which utilise such technology. Furthermore, their monolithic design bypasses the costly stage of bump-bonding in hybrid sensors and can substantially reduce detector costs. This contribution presents the latest results from characterisation studies of the MALTA2 sensors, including results demonstrating the radiation tolerance of these sensors

Radiation Hardness of MALTA2 Monolithic CMOS Sensors on Czochralski Substrates

MALTA2 is the latest full-scale prototype of the MALTA family of Depleted Monolithic Active Pixel Sensors (DMAPS) produced in Tower Semiconductor 180 nm CMOS technology. In order to comply with the requirements of High Energy Physics (HEP) experiments, various process modifications and front-end changes have been implemented to achieve low power consumption, reduce Random Telegraph Signal (RTS) noise, and optimise the charge collection geometry. Compared to its predecessors, MALTA2 targets the use of a high-resistivity, thick Czochralski (Cz) substrates in order to demonstrate radiation hardness in terms of detection efficiency and timing resolution up to 3E15 1 MeV neq/cm2 with backside metallisation to achieve good propagation of the bias voltage. This manuscript shows the results that were obtained with non-irradiated and irradiated MALTA2 samples on Cz substrates from the CERN SPS test beam campaign from 2021-2023 using the MALTA telescope