Characterization of Heavily Irradiated Dielectrics for Pixel Sensors Coupling Insulator Applications

S. Bharthuar*, M. Golovleva, M. Bezak, E. Brücken, A. Gädda, J. Härkönen, A. Karadzhinova-Ferrer, N. Kramarenko, S. Kirschenmann, P. Koponen, P. Luukka, K. Mizohata, J. Ott, E. Tuominen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
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An increase in the radiation levels during the high-luminosity operation of the Large Hadron Collider calls for the development of silicon-based pixel detectors that are used for particle tracking and vertex reconstruction. Unlike the conventionally used conductively coupled (DC-coupled) detectors that are prone to an increment in leakage currents due to radiation, capacitively coupled (AC-coupled) detectors are anticipated to be in operation in future collider experiments suitable for tracking purposes. The implementation of AC-coupling to micro-scale pixel sensor areas enables one to provide an enhanced isolation of radiation-induced leakage currents. The motivation of this study is the development of new generation capacitively coupled (AC-coupled) pixel sensors with coupling insulators having good dielectric strength and radiation hardness simultaneously. The AC-coupling insulator thin films were aluminum oxide (Al2O3) and hafnium oxide (HfO2) grown by the atomic layer deposition (ALD) method. A comparison study was performed based on the dielectric material used in MOS, MOSFET, and AC-coupled pixel prototypes processed on high resistivity p-type Magnetic Czochralski silicon (MCz-Si) substrates. Post-irradiation studies with 10 MeV protons up to a fluence of 1015 protons/cm2 suggest HfO2 to be a better candidate as it provides higher sensitivity with negative charge accumulation on irradiation. Furthermore, even though the nature of the dielectric does not affect the electric field within the AC-coupled pixel sensor, samples with HfO2 are comparatively less susceptible to undergo an early breakdown due to irradiation. Edge-transient current technique (e-TCT) measurements show a prominent double-junction effect as expected in heavily irradiated p-type detectors, in accordance with the simulation studies.

Original languageEnglish
Article number769947
JournalFrontiers in materials
Publication statusPublished - 19 Jan 2022
MoE publication typeA1 Journal article-refereed


  • AC-pixel sensors
  • ALD (atomic layer deposition)
  • alumina
  • hafnia
  • magnetic Czochralski
  • MOS capacitor
  • radiation hardness


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