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AC-coupled n-in-p pixel detectors on MCz silicon with atomic layer deposition (ALD) grown thin film process

Dec 18, 2019, 9:40 AM
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 Technologies Session11


Akiko Gädda (Helsiki Institute of Physics)


We report the fabrication process and characterization of our novel n+/p-/p+ pixel detectors made on 150mm diameter p-type Magnetic Czochralski silicon (p-MCz Si) wafers. The pixels were segmented 52 × 80 dual column and designed to be AC capacitive coupled. The resistive coupling, allowing Quality Assurance (QA) probing prior the Flip-Chip bonding, between pixels was realized by thin film metal -nitride resistors. The bias resistors were fabricated by Atomic Layer Deposition (ALD) technique and in some cases, by sputtering deposition. This approach allows us to render silicon area consuming punch through resistor structures obsolete and simultaneously reduce overall process complexity. Moreover, our previous studies have emphasized that applying ALD Aluminum Oxide (Al2O3) field insulator and passivation layer results in negative net oxide charge and thus additional p-spray or p-stop surface current termination structures are not necessary.
Our focused application is radiation-hard ALD AC-coupled pixel detector to be used in future use of the High-Luminosity Large Hadron Collider (HL-LHC) experiment. In addition to particle physics experiments and photon science experiments with bright light sources.
The pixel detectors were tested at Helsinki Institute of Physics (HIP) Detector laboratory and Ruđer Bošković Institute (RBI). For further study, AC coupled sensor was hybridized to PSI46dig read out chip (ROC) having 4160 pixels by flip-chip (FC) interconnection technique.
We show measurement data of AC coupled pixel detectors and single pad detectors. Data of electrical properties, full depletion voltage and leakage current are shown as well. The experimental result of bias resistor value 15 kOhm was attained. MOS -capacitor test structures were irradiated by TRIGA reactor neutrons (JSI, Ljubljana ) and by 60Co gamma source (RBI, Zagreb). We observed accumulation of negative oxide charge after neutron irradiation, and introduction of positive mobile charge induced by photon irradiation while fixed oxide charge remained stable. Our Transient Current Technique (TCT) measurements indicated clear pixel segmentation with excellent homogeneity.

Submission declaration Original and unpublished

Primary author

Akiko Gädda (Helsiki Institute of Physics)


Jennifer Ott (Helsinki Institute of Physics (FI)) Shudhashil Bharthuar (University of Helsinki) Dr Matti Kalliokoski (Ruđer Bošković Institute (HR)) Dr Aneliya Karadzhinova-Ferrer (Ruđer Bošković Institute) Jens Erik Brucken (Helsinki Institute of Physics (FI)) Stefanie Kirschenmann Vladyslav Litichevskyi (Helsinki Institute of Physics (FI)) Maria Golovleva (Helsinki Institute of Physics (FI)) Laura Martikainen (Helsinki Institute of Physics (FI)) Tiina Sirea Naaranoja (Helsinki Institute of Physics (FI)) Panja Luukka (Lappeenranta University of Technology (FI)) Dr Jaakko Härkönen (Ruđer Bošković Institute )

Presentation materials