Ghosh, P.

Larionov, P.

GSI Repository

Quality assurance tests of silicon microstrip sensors for the Silicon TrackingSystem in the CBM experiment at FAIRP. Larionov1 and P. Ghosh11Goethe Universita¨t, Frankfurt am Main, GermanyThe Compressed Baryonic Matter (CBM) experimentaims to explore the QCD phase diagram in the region ofhigh net baryonic densities and moderate temperatures.The core of the CBM experimental setup — the SiliconTracking System — will consist of 8 stations based ondouble-sided silicon strip sensors and self-triggered read-out. It will have to cope with large track densities and eventrates up to 107 s−1, will have to enable high momentumresolution and detection efficiency as well as stand radia-tion doses up to 1×1014 neq/cm2.A large amount of sensors (about 1400) will be requiredto construct the STS. For the proper operation of the sys-tem, each sensor requires a number of procedures to ensureproper production and to verify the full accordance to thetechnical specifications. Local laboratory tests are as im-portant as verification of the technical specifications pro-vided by the manufacturer. These tests will ensure that thesensors will be suitable for the STS detector and will satisfyits requirements. Both these two procedures define QualityAssurance for the Silicon Tracking System, which includesvisual inspection, bulk and interstrip parameters measure-ments, sensor efficiency and total signal to noise ratio tests,measurements of irradiated sensors, low temperature per-formance and current stability tests. In the following, wereport on QA tests of STS prototype sensors with 256 stripsper side, 300 µm thickness and 58 µm strip pitch [1].Bulk measurements — current-voltage (I-V) andcapacitance-voltage (C-V) characteristics (see Figure 1) —can serve as basic acceptance criteria. These measurementsare a good instrument to assess the quality of the sensor, toverify the manufacturer data and to make sure there hasbeen no damage during sensor manufacturing or handling.Also, some passive electrical characteristics were mea-sured for different strips of the sensor. These measurementsaim to investigate the charge collection and the equivalentnoise charge of the sensor. The value of coupling capaci-tance (Figure 2) allows to judge about the transmission ofthe signal. The ratio of coupling and interstrip capacitancesaffects the value of the signal transmitted to the read-outelectronics. For these measurements the wafer prober Su¨ss-PA300 was adapted in the clean room with temperature andhumidity control.Figure 3 indicates the variation of current-voltage curvesfor sensors that were irradiated with different fluences. Asa part of QA, these measurements were carried out to in-vestigate the sensor’s behavior and perfomance after irra-diation.Future QA activities for STS include long-term stabil-ity tests, low temperature performance measurements andoptimization of the measurement procedures via LabViewsoftware.(a) (b)Figure 1: Bulk measurements: a) current-voltage;b) capacitance-voltage.(a) (b)Figure 2: Coupling capacitance measurements: a) p-side ofthe sensor; b) n-side of the sensor.Bias Voltage, V0 20 40 60 80 100 120 140 160 180 200 220 240Leakage Current, mA-510-410-310-2/cmeqn14 Wafer 08, Fluence 1x10-2/cmeqn13 Wafer 01, Fluence 3x10-2/cmeqn13 Wafer 03, Fluence 1x10-2/cmeqn12 Wafer 24, Fluence 1x10Figure 3: Current-Voltage curves for irradiated sensors.References[1] J. M. Heuser et al., CBM Progress Report 2011, Darmstadt2012, p.17GSI SCIENTIFIC REPORT 2012 PHN-NQM-EXP-1847

Quality assurance tests of silicon microstrip sensors for the  Silicon Tracking System in the CBM experiment at FAIR

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Quality assurance tests of silicon microstrip sensors for the Silicon Tracking System in the CBM experiment at FAIR

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