Testing of Test Structures in Vienna Thomas Bergauer (HEPHY Vienna) CEC Meeting Berlin 19 May 2010
Status Vienna CMS Process Qualification Center 2001 -2007 HISTORY 19 May 2010 Thomas Bergauer (HEPHY Vienna) 2
Status Vienna 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 properation • Worked extremely well during CMS sensor production – Several problems have been identified during CMS quality assurance tests TS-CAP sheet 19 May 2010 baby GCD Thomas Bergauer (HEPHY Vienna) CAP-TS-AC diode MOS 2 MOS 1 3
Status Vienna 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 19 May 2010 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 Thomas Bergauer (HEPHY Vienna) 4
Status Vienna Three Setups have been installed 19 May 2010 Thomas Bergauer (HEPHY Vienna) 5
Status Vienna Mechanical support (Vienna) Microscope Probecard (green) in support TS fixed with vacuum onto support XY-Table for alignment 19 May 2010 Thomas Bergauer (HEPHY Vienna) 6
Status Vienna Probe-Card to switching matrix 2 nd Version Probe-card 19 May 2010 4 pcs. Keithley 1 x 10 multiplexer cards (part of switching system) Individual shielded cables Thomas Bergauer (HEPHY Vienna) 7
Status Vienna Instruments available in Vienna • Source Measure Unit: – Keithley 237 and 2410 • LCR Meter – Keithley 595 (quasistatic) – Agilent 4274 A (10 Hz-100 k. Hz) – Agilent 4285 A (75 k. Hz to 30 MHz) • Switching System – Keithley 7002 – 4 x 5 pt. matrix cards 7153 – 1 x 10 pt multiplexer cards 7154 19 May 2010 Thomas Bergauer (HEPHY Vienna) 8
Status Vienna Software: Labview Blue Fields: Obtained results extracted from graph by linear fits (red/green lines) Yellow Fields: Limits and cuts for qualification Fully automatic measurement procedure takes approx. 30 min per half moon to produce this: 19 May 2010 Thomas Bergauer (HEPHY Vienna) 9
Status Vienna 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) 19 May 2010 Thomas Bergauer (HEPHY Vienna) 10
Status Vienna Example of identified problems Inter strip resistance issue during CMS sensor production • • • 19 May 2010 Limit: Rint > 1 GΩ 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 Thomas Bergauer (HEPHY Vienna) 11
Status Vienna Solved Problems • 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 3. 5 k. Ohm Most of the issues have been solved by the vendors after an intervention from us 19 May 2010 Thomas Bergauer (HEPHY Vienna) 12
Status Vienna Instruments and Cold Chuck ACTUAL SETUP FOR SLHC UPGRADE 19 May 2010 Thomas Bergauer (HEPHY Vienna) 14
Status Vienna 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 19 May 2010 Thomas Bergauer (HEPHY Vienna) 15
Status Vienna Cold Chuck • 2 x 240 W 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 19 May 2010 Thomas Bergauer (HEPHY Vienna) 16
Status Vienna Cold Chuck in Measurement Box 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 19 May 2010 Thomas Bergauer (HEPHY Vienna) 17
Status Vienna 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 19 May 2010 Thomas Bergauer (HEPHY Vienna) 18
Status Vienna Measurements performed for CMS • • TS-CAP: – Coupling capacitance CAC to determine oxide thickness – IV-Curve: breakthrough voltage of oxide • – Inter-strip capacitance Cint • • • – Gate Controlled Diode – IV-Curve to determine surface current Isurface – Characterize Si-Si. O 2 interface CAP-TS-DC: – Inter-strip Resistance Rint • GCD: Baby-Sensor: – IV-Curve for dark current – Bulk breakthrough voltage Sheet: – Aluminium resistivity – p+-impant resistivity – Polysilicon resistivity CAP-TS-AC: Diode: – CV-Curve to determine depletion voltage Vdepletion – Calculate resistivity of silicon bulk • MOS: – CV-Curve to extract flatband voltage Vflatband to characterize fixed oxide charges – For thick interstrip oxide (MOS 1) – For thin readout oxide (MOS 2) TSCAP sheet 19 May 2010 MOS 2 baby diode GCD CAP-TS-AC MOS 1 Thomas Bergauer (HEPHY Vienna) 19
Status Vienna Measurements performed so far • In November 2009 we have received one protonirradiated CMS halfmoon from Karlsruhe • The structures were irradiated with protons to 5. 24 E 14 n(equiv) and are annealed (80 min at 60°C). • Measurements performed so far: – – 19 May 2010 IV on baby, diode CV Diode and Baby with comparison CV MOS C_int, R_int Thomas Bergauer (HEPHY Vienna) 20
Status Vienna Measurements: IV Non-irradiated 19 May 2010 Thomas Bergauer (HEPHY Vienna) irradiated 21
Status Vienna Measurements CV Comparison Unirradiated vs. Irradiated sample 19 May 2010 Thomas Bergauer (HEPHY Vienna) 22
Status Vienna Measurements MOS Non-irradiated 19 May 2010 Thomas Bergauer (HEPHY Vienna) irradiated 23
Status Vienna Strip scans at room temperature • We can also perform strip-by strip measurements of unirradiated sensors only (other setup without cold chuck) – – 19 May 2010 Single strip current Poly-silicon resistors Coupling capacitance Dielectric current Thomas Bergauer (HEPHY Vienna) 24
Status Vienna Test Structures of new Layout Diode Via-TS GCD TS_cap Sheet Cap-TS-DC Layout of new HPK wafer: MOS Cap-TS-AC f. C_int measurement 19 May 2010 Thomas Bergauer (HEPHY Vienna) 25
Status Vienna Manpower / Timing • Time Estimate for full half moon: 4 h – Manual measurements, no probe-card • Time estimate with probecard: 30 minutes – But: effort necessary to design und buy probe-card Available manpower • Technicians – 0 -2 FTE as necessary • Physicist – 0 -2 FTE as necessary • Students – 0. 2 - 1 FTE – Large effort to modify setup – Setup not flexible for other measurements anymore 19 May 2010 Thomas Bergauer (HEPHY Vienna) 26
Status Vienna 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 Tracker. DB 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 19 May 2010 Thomas Bergauer (HEPHY Vienna) 27
Status Vienna Backup slides follow THE END 19 May 2010 Thomas Bergauer (HEPHY Vienna) 28
Status Vienna Test Structures of new Layout of new HPK wafer and position of possible probe-card Cap-TS-AC f. C_int measurement 19 May 2010 Thomas Bergauer (HEPHY Vienna) 29
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