Speaker
Description
The development of precision silicon sensors is a key area of advancement in high-energy physics, particularly for the innermost tracking devices of future collider experiments. These sensors require a timing resolution on the order of 50 ps, pixel pitches of 50 µm or below, and radiation tolerance up to 10$^{16-17}$n$_{eq}$.cm$^{-2}$. One such innovation is the Silicon Electron Multiplier (SiEM), which incorporates an internal gain mechanism via a metallic electrode embedded in the silicon bulk. As described in [1], the SiEM aims to offer greater radiation tolerance than existing gain sensors (e.g., LGADs), thanks to its inherently radiation-hard gain mechanism, while maintaining comparable timing performance. It also supports pixel pitches down to 5 µm, a level of segmentation that is difficult to achieve with other silicon sensor technologies.
Between 2020 and 2021, the conceptual foundations of the SiEM were developed using TCAD simulations. The proposed device guides electrons generated by a minimum ionising particle (MIP) into narrow silicon pillars, where charge multiplication occurs via impact ionisation, driven by the high electric field produced by the embedded metallic electrodes. The motion of these multiplied charges then induces a signal on the readout electrode located at the top of each silicon pillar. Simulations showed gain factors well in excess of 10, encouraging further efforts to develop a suitable fabrication process. Since 2022, several approaches have been pursued to fabricate a prototype and demonstrate the validity of the proposed gain mechanism. The qualification of test structures recently produced by Hamamatsu confirmed the viability of the concept and will be presented here for the first time.
In this talk, the authors will describe the operating principles of the SiEM [1] as well as the various production approaches explored over the past couple of years, including both well-established microfabrication techniques, and more experimental methods used produce structures with very high aspect ratio pillars [2]. Finally, the results of the characterisation of demonstrators produced by Hamamatsu will be presented. Both laser systems and minimum ionising particles from the SPS test beam were used in summer 2025 and it demonstrates amplification of charges inside the SiEM structure. Building on this result, the future development of this sensor technology will be discussed.
References:
[1] The Silicon Electron Multiplier, M. H. Halvorsen et. al., NIM A 1041 (2022) 167325
[2] Fabrication of a Silicon Electron Multiplier sensor using Metal Assisted Chemical Etching and its characterisation, M. H. Halvorsen et. al., NIM A 1060 (2024) 169046
| Type of presentation (in-person/online) | in-person presentation |
|---|---|
| Type of presentation (I. scientific results or II. project proposal) | I. Presentation on scientific results |
