Initial Tests of Large Format Sensors for the ATLAS ITk Strip Tracker

For the production of the Inner Tracker (ITk) as part of the phase-II upgrade programme to prepare the ATLAS experiment for the High-Luminosity (HL) LHC, batches of Long Strip (LS) and Short Strip (SS) n-in-p type micro-strip sensors have been produced by Hamamatsu Photonics. The full size sensors measure approximately 98 x 98"mm^{2}" and are designed and engineered for tolerance against the 9.7 x "10^{14}", including a safety factor of 1.5, 1 MeV "n_{eq}/cm^{2}" fluence expected at the HL-LHC. Each sensor has 2 or 4 columns of 1280 individual channels arranged at 75.5μm horizontal pitch. To ensure the sensors comply with their specifications, a Quality Control (QC) procedure has been designed, comprising measurements on every individual sensor as well as on a sample basis. Every sensor is subjected to an initial visual inspection, after which the full surface of the sensor is captured with very high resolution by an automated camera setup. Non-contact metrology is performed to obtain the sensor surface profile. Electrical measurements establishing the reverse bias leakage current and depletion voltage are conducted automatically, with the recorded results uploaded to a production database following data quality checks. Sample sensors from every batch are subjected to 40 hour leakage stability checks in controlled atmosphere, and tests on every channel measuring leakage current, coupling capacitance and bias resistance are conducted. In this paper, QC test validation data and the compiled results for the first batches of production grade sensors, consisting of approximately 30 LS and SS sensors each are presented. Data from multiple test sites are compared with the data provided by Hamamatsu Photonics where possible. The QC protocol was validated, and the results of the first production sensors were confirmed to be within specification.