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Humidity Sensitivity of Large Area Silicon Sensors: Study and Mitigation

Dec 17, 2019, 2:40 PM
Sun: B1F-Meeting rooms#4-6; Mon-Wed: B2F-RAN (International Conference Center Hiroshima)

Sun: B1F-Meeting rooms#4-6; Mon-Wed: B2F-RAN

International Conference Center Hiroshima

Peace Memorial Park, Hiroshima-shi
ORAL Strip sensors Session9


Javier Fernandez-Tejero (CNM-Barcelona (ES))


The production of large area sensors is one of the main challenges that the ATLAS collaboration faces for the new Inner-Tracker (ITk) full-silicon detector. During the prototype fabrication phase for the High Luminosity Large Hadron Collider (HL-LHC) upgrade, several ATLAS institutes observed indications of humidity sensitivity of large area sensors, even at relative humidities well below the dew formation. Specially, barrel and end-cap silicon strip sensors fabricated in 6-inch wafers manifest a prompt decrease of the breakdown voltage when operating under relative humidity above a threshold, adversely affecting the performance of the sensors.
This work presents an extensive study of this behavior on large area sensors. The locations of the hotspots at the breakdown voltage for different humidity levels are revealed using different infrared thermography techniques. Several palliative treatments are attempted, proving the influence of sensor cleaning methods or baking on the device performance, but no influence on the humidity sensitivity. Furthermore, an extensive study of the incidence of the sensitivity is presented, showing the time evolution and radiation influence. In addition to the investigation of these prototype sensors, a specific fabrication batch of large sensors with special passivation is also studied and complemented with simulations, allowing for a deeper understanding of the responsible mechanisms.
Finally, a summary of the actions to be taken during sensor production and assembly is derived from this work, in order to minimize the impact of humidity sensitivity on the performance of large area silicon sensors for High Energy Phsyics (HEP) experiments.

Submission declaration Original and unpublished

Primary author

Javier Fernandez-Tejero (CNM-Barcelona (ES))


Philip Patrick Allport (University of Birmingham (UK)) Karola Dette (University of Toronto (CA)) Vitaliy Fadeyev (University of California,Santa Cruz (US)) Celeste Fleta (Instituto de Microelectrónica de Barcelona, Centro Nacional de Microelectrónica (ES)) Dag Gillberg (Carleton University) Laura Gonella (University of Birmingham (UK)) Kazuhiko Hara (University of Tsukuba (JP)) Cole Helling (UC Santa Cruz) Bart Hommels (University of Cambridge (GB)) John Stakely Keller (Carleton University (CA)) Christoph Thomas Klein (University of Cambridge (GB)) Thomas Koffas (Carleton University (CA)) Vera Latonova (Acad. of Sciences of the Czech Rep. (CZ)) Marcela Mikestikova (Acad. of Sciences of the Czech Rep. (CZ)) Robert Orr (University of Toronto (CA)) Simon Pyatt (University of Birmingham (GB)) Urmila Soldevila Serrano (Univ. of Valencia and CSIC (ES)) Ezekiel Staats (Carleton University (CA)) Juergen Thomas (University of Birmingham (GB)) Miguel Ullan Comes (CNM-Barcelona (ES)) Yoshinobu Unno (High Energy Accelerator Research Organization (JP)) Sayaka Wada (University of Tsukuba)

Presentation materials