4 May 2010 Thomas Bergauer (HEPHY Vienna) Testing of Test Structures in Vienna CMS Sensor-TUPO

HISTORY CMS Process Qualification Center Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Process Monitoring on Test Structures What is Process monitoring? –Each wafer hosts additional test structures around main detector –“standard” set of test structures is called “half moon” (because of its shape) –Test structures used to determine one parameter per structure –Assuming that sensor and test structures behave identically –Some parameters are not accessible on main detector (e.g. flatband voltage of MOS), but important for proper operation Worked extremely well during CMS sensor production –Several problems have been identified during CMS quality assurance tests TS-CAP sheet GCD CAP-TS-AC babydiode MOS 1 MOS 2 3Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Measurement Setup Probe-card with 40 needles contacts all pads of test structures in parallel –Half moon fixed by vacuum –Micropositioner used for Alignment –In light-tight box with humidity and temperature control Instruments –Source Measurement Unit (SMU) –Voltage Source –LCR-Meter (Capacitance) Heart of the system: Cross-point switching box, used to switch instruments to different needles 4Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Three Setups have been installed 5Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Mechanical support (Vienna) Microscope Probecard (green) in support TS fixed with vacuum onto support XY-Table for alignment 6Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Probe-Card to switching matrix 2nd Version Individual shielded cables 7Thomas Bergauer (HEPHY Vienna)4 May 2010 Probe-card 4 pcs. Keithley 1x10 multiplexer cards (part of switching system)

CMS Sensor-TUPO Instruments available in Vienna Source Measure Unit: –Keithley 237 and 2410 LCR Meter –Keithley 595 (quasistatic) –Agilent 4274A (10Hz-100kHz) –Agilent 4285A (75kHz to 30MHz) Switching System –Keithley 7002 –4x5 pt. matrix cards 7153 –1x10 pt multiplexer cards Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Yellow Fields: Limits and cuts for qualification Blue Fields: Obtained results extracted from graph by linear fits (red/green lines) Software: Labview Fully automatic measurement procedure takes approx. 30min per half moon to produce this: 9Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Passed/Not Passed Lights After all measurements finished Window pops up One light for each test –Green: within limits –Red: out of limits Allows immediate judgment about quality Pressing “OK” button writes data directly into Tracker Construction database (Oracle) 10Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Example of identified problems Limit: R int > 1GΩ to have a good separation of neighbouring strips Each dot in the left plot shows one measurement Value started to getting below limit We reported this to the company Due to the long production pipeline, a significant amount of ~1000 sensors were affected Inter strip resistance issue during CMS sensor production 11Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO In total, more than 4500 Half moons have been tested in the three labs Different problems of several sensor batches have been discovered, e.g.: –Too high flatband voltage –Too high poly-Si resistor –Too high Al sheet resistivity –Too low inter-strip resistance –Too high bulk resistivity Most of the issues have been solved by the vendors after an intervention from us 3.5 kOhm 12Thomas Bergauer (HEPHY Vienna)4 May 2010 Solved Problems

CMS Sensor-TUPO In fairness, I have to say that the majority of monitored parameters were pretty stable vs. time For example: –Coupling capacitance (top) –Breakthrough of dielectric (bottom) Specification requires > 100 V 13Thomas Bergauer (HEPHY Vienna)4 May 2010 Other Results

CMS Sensor-TUPO ACTUAL SETUP FOR SLHC UPGRADE Instruments and Cold Chuck 14Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Setup today Picture above shows the current status of the setup Unchanged (wrt. CMS sensor production): SMU, LCR-Meter and other instruments New: cold chuck for testing irradiated structures Different: currently no probe-card, but individual needles 15Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Cold Chuck 2x 240W water cooled Peltier modules Chiller filled with alcohol/water mixture to remove heat from back of Peltier modules 2-channel power supply from Vienna Cold box connected to peltier elements HEPHY-made TRHX System for monitoring of temperatures and relative humidity 16Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Cold Chuck in Measurement Box 17Thomas Bergauer (HEPHY Vienna)4 May 2010 Acrylic glas box for minimizing of dry volume; Flooded with dry air (DP -60 deg.C) “glovebox” with gloves Opening with cover to change sensor/halfmoon

CMS Sensor-TUPO Individual needles instead of probe-card Although a probe-card is very handy for doing repeated measurements on thousands of test structures, the layout of halfmoon is fixed and other measurements cannot be performed Thus, we will keep individual needles for the moment 18Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Measurements performed for CMS TS-CAP: –Coupling capacitance C AC to determine oxide thickness –IV-Curve: breakthrough voltage of oxide Sheet: –Aluminium resistivity –p + -impant resistivity –Polysilicon resistivity GCD: –Gate Controlled Diode –IV-Curve to determine surface current I surface –Characterize Si-SiO 2 interface CAP-TS-AC: –Inter-strip capacitance C int Baby-Sensor: –IV-Curve for dark current –Bulk breakthrough voltage CAP-TS-DC: –Inter-strip Resistance R int Diode: –CV-Curve to determine depletion voltage V depletion –Calculate resistivity of silicon bulk MOS: –CV-Curve to extract flatband voltage V flatband to characterize fixed oxide charges –For thick interstrip oxide (MOS1) –For thin readout oxide (MOS2) TS- CAP sheet GCD CAP-TS-AC babydiode MOS 1 MOS 2 19Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Measurements performed so far In November 2009 we have received one proton-irradiated CMS halfmoon from Karlsruhe The structures were irradiated with protons to 5.24E14 n(equiv) and are annealed (80min at 60°C). Measurements performed so far: –IV on baby, diode –CV Diode and Baby with comparison –CV MOS –C_int, R_int 20Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Measurements: IV Non-irradiatedirradiated 21Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Measurements CV Comparison Unirradiated vs. Irradiated sample 22Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Measurements MOS Non-irradiatedirradiated 23Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Strip scans at room temperature We can also perform strip-by strip measurements of unirradiated sensors only (other setup without cold chuck) –Single strip current –Poly-silicon resistors –Coupling capacitance –Dielectric current 24Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Test Structures of new Layout Layout of new HPK wafer: DiodeGCD TS_cap Cap-TS-AC f. C_int measurement Sheet MOS Via-TS Cap-TS-DC 25Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Manpower / Timing Time Estimate for full half moon: 4h –Manual measurements, no probe-card Time estimate with probe- card: 30 minutes –But: effort necessary to design und buy probe-card –Large effort to modify setup –Setup not flexible for other measurements anymore Available manpower Technicians –0-2 FTE as necessary Physicist –0-2 FTE as necessary Students – FTE 26Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO Planning/Summary Currently: We are re-measuring all parameters of irradiated/not irradiated structures that our student gets familiar with it Necessary modification of software –improve fits –DB interaction (once TrackerDB stuff gets settled) We will perform n-irradiation in our own reactor for testing purposes in near future We are ready for the delivery from HPK 27Thomas Bergauer (HEPHY Vienna)4 May 2010

CMS Sensor-TUPO THE END Backup slides follow 28Markus Friedl (HEPHY Vienna)20 October 2009

CMS Sensor-TUPO Test Structures of new Layout Layout of new HPK wafer and position of possible probe-card Cap-TS-AC f. C_int measurement 29Thomas Bergauer (HEPHY Vienna)4 May 2010