Prototype Evaluation of Silicon Sensors and Other Detector Components Suitable for Future CMS Tracker

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Title: Prototype Evaluation of Silicon Sensors and Other Detector Components Suitable for Future CMS Tracker
Author: Bharthuar, Shudhashil
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2019
Language: eng
Thesis level: master's thesis
Discipline: Fysiikka
Abstract: The High-Luminosity phase of the Large Hadron Collider (HL-LHC), that is expected to become operational in 2026, aims at increasing the luminosity of the LHC up to ten times higher than its current nominal value. This in turn calls for improving the radiation hardness of the CMS tracker detectors that will be subjected to significantly greater levels of radiation. The following thesis aims at examining the electrical properties of metal–oxide semiconductor (MOS) capacitors and silicon sensors of different structures with a design developed for CMS Beam Luminosity Telescope (BLT). These were fabricated on three different wafers and the atomic layer deposition (ALD) of alumina on the p-type silicon substrate was done by using either ozone (O3), water (H2O), or water and ozone (H2O+O3) pulsed directly one after the other, as oxygen precursor. The same study is made on Radiation Monitoring (RADMON)-type sensors with n-type silicon substrate and Titanium Nitride (TiN) based bias resistors generated on substrate by deposition of a thin TiN layer by radio-frequency sputtering with different sputtering parameters. Electrical properties of these sensors are derived by measuring their capacitance–voltage and current–voltage characteristics. The results demonstrate that BLT diodes from the three different wafers, having the same thickness, give the same value for full depletion voltage. However, structures with larger metalization area have larger surface currents. RADMON and standard BLT diodes of the same wafer do not show any significant difference in full depletion voltage. However, leakage current for the p-type sensor is higher in comparison to that of the n-type sensor. Results also show that MOS capacitor samples from the H2O+O3 wafer are more sensitive to radiation compared to those from the H2O and O3 wafers. Further, TiN based bias resistor samples produced with shorter sputtering time and lower Argon gas flow rate and a high Nitrogen gas flow rate have a higher resistance.

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