Test beam analysis of irradiated stitched passive CMOS strip sensors

Abstract: With the ever increasing performance requirements of current and future high-energy particle detectors also the total area of the silicon detectors employed in them increases, making them one, if not the, main cost drivers for detectors. This, coupled together with the drastically increasing energy costs and inflation, facilitates the need for the research in and development of cost efficient and radiation hard sensors. A key technology in this effort is CMOS, which is a widespread industry standard for the processing of silicon chips. The main advantage of the CMOS process consists of the large number of vendors offering it, allowing relatively easy access to the already existing industrial production lines, enabling fast, cheap and reliable production of large areas of silicon, without creating a dependence on a single vendor. Traditional foundries, used for the production of silicon detectors thus far, use wafer-size masks in the processing, which CMOS foundries do not offer. Their mask size is limited to a few cm2 and they use a process called stitching to create larger, electrically connected structures.
For stitching, the entire sensor structure is divided into smaller substructures, with each having its own mask set. During the sensor processing, these masks are used to imprint their structure onto the silicon, then they are moved very precisely next to the just processed area and imprinted again. By repeating this process as often as is desired, with different masks if needed, larger, electrically fully connected structures are created. The main goal of this thesis is to determine if the stitching negatively impacts sensor characteristics, like charge collection, spatial resolution and hit detection efficiency, and if the stitches degrade due to irradiation. Furthermore the overall performance and radiation hardness of the sensors is tested.
Three different designs of stitched passive CMOS sensors, produced by LFoundry in a 150 nm process and with up to five stitches, are investigated in this thesis. Some of the sensors have been irradiated with reactor neutrons up to a fluence of 1 · 1015 neq/cm2. All irradiated sensors have undergone benefical annealing. In this thesis the probe-station, the β-setup and the test beam at the DESY-II accelerator were used to determine the basic IV-charcacteristics, charge collection, mean cluster size, spatial resolution, hit detection efficiency and fake cluster rate of the sensors.
No negative impact of the stitching on any of the aforementioned properties and no degradation of the stitches with irradiation was found, meaning the CMOS process can be successfully used to produce silicon strip sensors for high-energy particle detectors. A significant loss of resolution and efficiency for irradiated samples was observed, leading to the conclusion that further development in the radiation tolerance of the sensors is needed

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Universität Freiburg, Masterarbeit, 2023

Classification and Topics

• Keyword: Streifendetektor ; CMOS ; Hochenergiephysik

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2024
• Creator: Lex, Fabian Simon
• Contributor: Jakobs, Karl ; Experimentelle Teilchenphysik, Abt. Prof. Karl Jakobs

Further information

• DOI: 10.6094/UNIFR/243332
• URN: urn:nbn:de:bsz:25-freidok-2433323
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 25.03.2025, 1:48 PM CET