Periodic Reporting for period 4 - MONOLITH (Monolithic Multi-Junction Picosecond Avalanche Detector for future physics experiments and applications)
Période du rapport: 2025-01-01 au 2025-06-30
Modern particle-physics experiments and many other fields of science increasingly require thin, low-mass sensors capable of measuring both the position and time of particle hits with extreme precision. However, current detector technologies are limited by the physical and technical constraints of hybrid architectures, where the sensing and readout elements are fabricated separately and connected through complex, costly assembly steps. This limits scalability, increases latency, and makes the deployment of large detection areas prohibitively expensive.
The MONOLITH project introduces a novel silicon-sensor structure, the patented monolithic Picosecond Avalanche Detector (PicoAD), designed to overcome these intrinsic limitations. The PicoAD provides picosecond-level timing and high spatial resolution simultaneously, implemented in a fully monolithic CMOS process. This approach removes the need for hybridization, dramatically reduces cost and complexity, and enables large-scale production using standard microelectronics fabrication lines.
The technological breakthrough achieved by MONOLITH goes well beyond the boundaries of particle physics. The ability to detect particles and photons with tens of picoseconds time precision and micrometric spatial accuracy has transformative potential across multiple domains. In fundamental science, the PicoAD concept offers a sustainable, scalable solution for the next generation of experiments at hadron colliders, in nuclear and astroparticle physics, and for space-borne cosmic-ray and solar-physics missions, where lightweight, radiation-hard, and high-performance sensors are essential.
In applied science and technology, the same innovations can enable significant societal benefits:
• In medical imaging, particularly Time-of-Flight PET and X-ray imaging, the detector ultra-fast response can improve image quality and reduce patient radiation dose.
• In autonomous systems, including LiDAR for self-driving vehicles, robotics, and drone navigation, they can provide real-time 3D vision with improved depth accuracy and lower latency, directly enhancing safety and reliability.
• In quantum photonics and precision metrology, the combination of fast timing and CMOS integration opens new possibilities for compact, scalable sensing systems.
By demonstrating that such high performance can be achieved in standard CMOS technology, MONOLITH contributes to European leadership and sustainability in semiconductor innovation, a key strategic area for science, technology, and industry.
The overall goal of the MONOLITH project is to realize and demonstrate a new generation of monolithic silicon detectors combining:
1. Picosecond-level time resolution,
2. High spatial precision and efficiency, and
3. Cost-effective, scalable CMOS manufacturing.
To achieve this, the project integrates advanced device simulation, ASIC design, microfabrication, and testbeam validation to prove the PicoAD sensor concept.
Specific objectives include:
• Demonstrating that monolithic timing detectors can reach and surpass the performance of hybrid pixel detectors at a fraction of the cost.
• Establishing a technology platform adaptable for diverse domains, from collider experiments to medical and industrial imaging, autonomous sensing, and quantum detection.
• Creating a sustainable innovation pathway, exemplified by the establishment of a spin-off company that will transfer the PicoAD technology to real-world applications.
In essence, MONOLITH transforms a fundamental instrumentation challenge into a broad technological opportunity, offering a single, scalable detector concept that unites scientific discovery and societal innovation.
The MONOLITH project introduces a novel silicon-sensor structure, the patented monolithic Picosecond Avalanche Detector (PicoAD), designed to overcome these intrinsic limitations. The PicoAD provides picosecond-level timing and high spatial resolution simultaneously, implemented in a fully monolithic CMOS process. This approach removes the need for hybridization, dramatically reduces cost and complexity, and enables large-scale production using standard microelectronics fabrication lines.
The technological breakthrough achieved by MONOLITH goes well beyond the boundaries of particle physics. The ability to detect particles and photons with tens of picoseconds time precision and micrometric spatial accuracy has transformative potential across multiple domains. In fundamental science, the PicoAD concept offers a sustainable, scalable solution for the next generation of experiments at hadron colliders, in nuclear and astroparticle physics, and for space-borne cosmic-ray and solar-physics missions, where lightweight, radiation-hard, and high-performance sensors are essential.
In applied science and technology, the same innovations can enable significant societal benefits:
• In medical imaging, particularly Time-of-Flight PET and X-ray imaging, the detector ultra-fast response can improve image quality and reduce patient radiation dose.
• In autonomous systems, including LiDAR for self-driving vehicles, robotics, and drone navigation, they can provide real-time 3D vision with improved depth accuracy and lower latency, directly enhancing safety and reliability.
• In quantum photonics and precision metrology, the combination of fast timing and CMOS integration opens new possibilities for compact, scalable sensing systems.
By demonstrating that such high performance can be achieved in standard CMOS technology, MONOLITH contributes to European leadership and sustainability in semiconductor innovation, a key strategic area for science, technology, and industry.
The overall goal of the MONOLITH project is to realize and demonstrate a new generation of monolithic silicon detectors combining:
1. Picosecond-level time resolution,
2. High spatial precision and efficiency, and
3. Cost-effective, scalable CMOS manufacturing.
To achieve this, the project integrates advanced device simulation, ASIC design, microfabrication, and testbeam validation to prove the PicoAD sensor concept.
Specific objectives include:
• Demonstrating that monolithic timing detectors can reach and surpass the performance of hybrid pixel detectors at a fraction of the cost.
• Establishing a technology platform adaptable for diverse domains, from collider experiments to medical and industrial imaging, autonomous sensing, and quantum detection.
• Creating a sustainable innovation pathway, exemplified by the establishment of a spin-off company that will transfer the PicoAD technology to real-world applications.
In essence, MONOLITH transforms a fundamental instrumentation challenge into a broad technological opportunity, offering a single, scalable detector concept that unites scientific discovery and societal innovation.
The first monolithic chip prototype integrating the patented multi-PN junction PicoAD sensor and ultra-fast, low-noise front-end electronics was extensively tested at the University of Geneva cleanroom facilities using radioactive sources and in beam lines at CERN. The sensor was fully functional and showed an average time resolution of (17 ± 1) ps. These results represent an excellent first demonstration of the PicoAD concept and confirmed the validity of the design approach.
A second prototype was produced in 2022, incorporating improvements to both the sensor and the readout electronics. A first version without an internal gain layer demonstrated full detection efficiency and time resolutions down to 20 ps. Several devices were irradiated at a cyclotron up to a proton fluence of 10¹⁶ neq/cm², equivalent to the harshest conditions expected at the future High-Luminosity LHC programme at CERN. Remarkably, the detectors remained fully operational: test-beam measurements showed that the time resolution increased modestly from 20 ps (unirradiated) to 45 ps after 10¹⁶ neq/cm². These results clearly demonstrate the excellent radiation hardness of the low noise electronics based on SiGe HBT realised by the MONOLITH team.
Detailed TCAD and circuit simulations were carried out to optimize the PicoAD silicon wafer layering and gain-implant parameters. Multiple detector variants were fabricated, featuring absorption epitaxial layers of 3 and 5 µm, drift epitaxial layers of 15 and 25 µm, and four distinct gain-layer implant doses. All detector variants were successfully processed and tested. In particular, the version with 5 µm + 15 µm layers and the highest gain-layer dose achieved exceptional performance in CERN test beam experiments: the sensor exhibited full efficiency and a time resolution of 12 ps, establishing a new performance benchmark for monolithic timing detectors.
In parallel, a standalone chip implementing a novel Time-to-Digital Converter architecture, also designed and patented by MONOLITH team members, was produced and tested. The circuit achieved picosecond-level timing precision, matching the requirements of the monolithic detector. This validated the full electronic chain needed for time measurement within the MONOLITH architecture.
The results of MONOLITH represent a major technological advance in the field of particle-detection instrumentation and open new avenues for both fundamental research and applied technology. The project has published key findings in peer-reviewed journals and presented results atinternational conference proceedings. A spin-off company has been created to transfer the monolithic timing-detector technology to industrial applications, notably LiDAR systems for autonomous mobility, robotics, and drones. This ensures long-term exploitation and societal impact.
Overall, the MONOLITH project has successfully demonstrated the feasibility and performance of monolithic picosecond-timing silicon detectors, achieving world-leading results and establishing a solid foundation for both continued academic research and commercial innovation.
A second prototype was produced in 2022, incorporating improvements to both the sensor and the readout electronics. A first version without an internal gain layer demonstrated full detection efficiency and time resolutions down to 20 ps. Several devices were irradiated at a cyclotron up to a proton fluence of 10¹⁶ neq/cm², equivalent to the harshest conditions expected at the future High-Luminosity LHC programme at CERN. Remarkably, the detectors remained fully operational: test-beam measurements showed that the time resolution increased modestly from 20 ps (unirradiated) to 45 ps after 10¹⁶ neq/cm². These results clearly demonstrate the excellent radiation hardness of the low noise electronics based on SiGe HBT realised by the MONOLITH team.
Detailed TCAD and circuit simulations were carried out to optimize the PicoAD silicon wafer layering and gain-implant parameters. Multiple detector variants were fabricated, featuring absorption epitaxial layers of 3 and 5 µm, drift epitaxial layers of 15 and 25 µm, and four distinct gain-layer implant doses. All detector variants were successfully processed and tested. In particular, the version with 5 µm + 15 µm layers and the highest gain-layer dose achieved exceptional performance in CERN test beam experiments: the sensor exhibited full efficiency and a time resolution of 12 ps, establishing a new performance benchmark for monolithic timing detectors.
In parallel, a standalone chip implementing a novel Time-to-Digital Converter architecture, also designed and patented by MONOLITH team members, was produced and tested. The circuit achieved picosecond-level timing precision, matching the requirements of the monolithic detector. This validated the full electronic chain needed for time measurement within the MONOLITH architecture.
The results of MONOLITH represent a major technological advance in the field of particle-detection instrumentation and open new avenues for both fundamental research and applied technology. The project has published key findings in peer-reviewed journals and presented results atinternational conference proceedings. A spin-off company has been created to transfer the monolithic timing-detector technology to industrial applications, notably LiDAR systems for autonomous mobility, robotics, and drones. This ensures long-term exploitation and societal impact.
Overall, the MONOLITH project has successfully demonstrated the feasibility and performance of monolithic picosecond-timing silicon detectors, achieving world-leading results and establishing a solid foundation for both continued academic research and commercial innovation.
The project aims at providing a low-noise, low-power and ultra-fast electronics able to process signals with picosecond resolution.
This electronics will be produced in standard CMOS processes and implemented in the same wafer of a very fast sensor (patented) in a "monolithic" implementation, therefore allowing for simplified assembly process and reduced production cost.
The sensor and the electronics will be radiation tolerant, in order to be used in particle and nuclear physics experiments as well as in medical and space applications.
This electronics will be produced in standard CMOS processes and implemented in the same wafer of a very fast sensor (patented) in a "monolithic" implementation, therefore allowing for simplified assembly process and reduced production cost.
The sensor and the electronics will be radiation tolerant, in order to be used in particle and nuclear physics experiments as well as in medical and space applications.