Testing of Test Structures in Vienna

1. Testing of Test Structures in Vienna Thomas Bergauer (HEPHY Vienna) CMS Sensor-TUPO

2. CMS Process Qualification Center 2001-2007 History Thomas Bergauer (HEPHY Vienna)

3. TS-CAP baby diode MOS 2 GCD sheet CAP-TS-AC CAP-TS-AC MOS 1 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 Thomas Bergauer (HEPHY Vienna)

4. 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 Thomas Bergauer (HEPHY Vienna) 4

5. Three Setups have been installed Thomas Bergauer (HEPHY Vienna)

6. Mechanical support (Vienna) Microscope Probecard (green) in support TS fixed with vacuum onto support XY-Table for alignment Thomas Bergauer (HEPHY Vienna)

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

8. 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 7154 Thomas Bergauer (HEPHY Vienna)

9. 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. 30min per half moon to produce this: Thomas Bergauer (HEPHY Vienna)

10. 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) Thomas Bergauer (HEPHY Vienna) 10

11. Example of identified problems Inter strip resistance issue during CMS sensor production • Limit: Rint > 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 Thomas Bergauer (HEPHY Vienna)

12. 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 • Most of the issues have been solved by the vendors after an intervention from us 3.5 kOhm Thomas Bergauer (HEPHY Vienna) 12

13. Instruments and Cold Chuck Actual SETUP for SLHC Upgrade Thomas Bergauer (HEPHY Vienna)

14. 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 Thomas Bergauer (HEPHY Vienna)

15. 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 Thomas Bergauer (HEPHY Vienna)

16. 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 Thomas Bergauer (HEPHY Vienna)

17. 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 Thomas Bergauer (HEPHY Vienna)

18. TS-CAP: Coupling capacitance CAC to determine oxide thickness IV-Curve: breakthrough voltage of oxide Sheet: Aluminium resistivity p+-impantresistivity Polysilicon resistivity GCD: Gate Controlled Diode IV-Curve to determine surface current Isurface Characterize Si-SiO2 interface CAP-TS-AC: Inter-strip capacitance Cint Baby-Sensor: IV-Curve for dark current Bulk breakthrough voltage CAP-TS-DC: Inter-strip Resistance Rint 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 (MOS1) For thin readout oxide (MOS2) TS-CAP MOS 2 baby diode GCD sheet CAP-TS-AC CAP-TS-AC MOS 1 Measurements performed for CMS Thomas Bergauer (HEPHY Vienna)

19. 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 Thomas Bergauer (HEPHY Vienna)

20. Measurements: IV Non-irradiated irradiated Thomas Bergauer (HEPHY Vienna)

21. Measurements CV Comparison Unirradiated vs. Irradiated sample Thomas Bergauer (HEPHY Vienna)

22. Measurements MOS Non-irradiated irradiated Thomas Bergauer (HEPHY Vienna)

23. 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 Thomas Bergauer (HEPHY Vienna)

24. Test Structures of new Layout Layout of new HPK wafer: Sheet Cap-TS-DC Diode GCD TS_cap MOS Via-TS Cap-TS-AC f. C_int measurement Thomas Bergauer (HEPHY Vienna)

25. 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 • 0.2 - 1 FTE Thomas Bergauer (HEPHY Vienna)

26. 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 Thomas Bergauer (HEPHY Vienna)

27. Backup slides follow The end Markus Friedl (HEPHY Vienna)

28. Test Structures of new Layout Layout of new HPK wafer and position of possible probe-card Cap-TS-AC f. C_int measurement Thomas Bergauer (HEPHY Vienna)