Thomas Fritzsch | Searcharxiv

arXiv2026

Evaluation of polymer-metal-hybrid bonded wafer-stacks and sensor wafers for ultra-thin hybrid silicon detectors

Semiconductor pixel detectors are widely established in High Energy Physics (HEP) and Medical physics for their high spatial resolution and tracking capabilities. Research on both monolithic detectors and hybrid detectors is ongoing. Monolithic detectors, which integrate the sensor and the read-out electronics in the same die, provide the benefit of reduced thickness but the needed intricate imaging process is only offered by a limited number of chip vendors. The hybrid approach instead facilitates the design and fabrication of sensor and read-out chip using different technologies and opens up access to a large market of semiconductor vendors. For the production of silicon pixel detectors, the interconnection between sensor and read-out chip is usually realized on an individual die level. The needed mechanical stability during the handling of the dies limits their possible thinness. The wafer-to-wafer interconnection process being developed in this project uses a polymer underfill layer between the wafers to provide additional mechanical stability. This allows one to thin the wafer stack significantly after interconnection, bringing the total thickness close to that of monolithic detectors. In this paper, we present first results on the bump bonding yield of the process based on daisy-chain wafer measurements. For the first hybrid pixel detectors produced with this technique, a dedicated sensor wafer was designed and fabricated to be bonded to Timepix3 read-out chip wafers. Results of the characterization of the sensor wafer before hybridization are presented. We show that the wafer-to-wafer bonding process is suitable for hybrid semiconductor pixel detectors.

physics.ins-det↗

arXiv2022

Development of novel single-die hybridisation processes for small-pitch pixel detectors

Hybrid pixel detectors require a reliable and cost-effective interconnect technology adapted to the pitch and die sizes of the respective applications. During the ASIC and sensor R\&D phase, especially for small-scale applications, such interconnect technologies need to be suitable for the assembly of single dies, typically available from Multi-Project-Wafer submissions. Within the CERN EP R&D programme and the AIDAinnova collaboration, innovative hybridisation concepts targeting vertex-detector applications at future colliders are under development. Recent results of two novel interconnect methods for pixel pitches of 25um and 55um are presented in this contribution -- an industrial fine-pitch SnAg solder bump-bonding process adapted to single-die processing using support wafers, as well as a newly developed in-house single-die interconnection process based on ACF. The fine-pitch bump-bonding process is qualified with hybrid assemblies from a recent bonding campaign at Frauenhofer IZM. Individual CLICpix2 ASICs with 25um pixel pitch were bump-bonded to active-edge silicon sensors with thicknesses ranging from 50um to 130um. The device characterisation was conducted in the laboratory as well as during a beam test campaign at the CERN SPS beam-line, demonstrating an interconnect yield of about 99.7%. The ACF interconnect technology replaces the solder bumps by conductive micro-particles embedded in an epoxy film. The electro-mechanical connection between the sensor and ASIC is achieved via thermocompression of the ACF using a flip-chip device bonder. The required pixel pad topology is achieved with an in-house ENIG plating process. This newly developed ACF hybridisation process is first qualified with the Timepix3 ASICs and sensors with 55um pixel pitch. The technology can be also used for ASIC-PCB/FPC integration, replacing wire bonding or large-pitch solder bumping techniques.

physics.ins-det↗