Status of Double Sided Silicon Sensors

1. Status of Double Sided Silicon Sensors Thomas Bergauer (HEPHY Vienna) B2GM

2. Overview Thomas Bergauer (HEPHY Vienna) Introduction Micron Status HPK Status Beam test and Irradiation

3. Introduction Thomas Bergauer (HEPHY Vienna)

4. Vendors for 6” DSSD • Aim is to use double sided silicon detectors with AC-coupled readout and poly-silicon resistor biasing from 6 inch wafer • Hamamatsu decided in the past to abandon the production of double sided sensors • Thus, negotiations with Canberra, SINTEF and Micron started • Finally HPK could be convinced to restart DSSD production on 6” wafers • 6” prototypes ordered from • Hamamatsu (rectangular): First batch delivered in April • Micron (trapezoidal): First batch in July T. Bergauer

5. SVD Layout Thomas Bergauer (HEPHY Vienna)

6. Micron Status Thomas Bergauer (HEPHY Vienna)

7. Trapezoidal Sensors (Micron) • Full wafer designed using self-developed framework • Including test structures and mini sensors to test different p-stop designs • Delivery due July 2010 Trapezoidal sensor with test structures Sensor “programming language” Thomas Bergauer (HEPHY Vienna)

8. 768 readout strips 75-50 µm pitch (fan shaped) 767 intermediate strips (not read out) Trapezoidal sensor – p-side • Multi-guard-ring structure • 10 guard rings to control voltage drop Thomas Bergauer (HEPHY Vienna)

9. 512 readout strips 240 µm pitch 511 intermediate strips (not read out) Trapezoidal sensor – n-side • Similar multi-guard-ring structure • Strips and rings separated by p-stop implants Thomas Bergauer (HEPHY Vienna)

10. Micron Wafer Layout 3 different GCDsfor the n-side Quadratic baby sensors 2,3,4 p-side: 512 strips 50 µm pitch 1 interm. strip n-side: 256 strips 100 µm pitch 0 interm. strip different p-stop patterns Main sensor p-side: 768 strips 75-50 µm pitch 1 interm. strip n-side: 512 strips 240 µm pitch 1 interm. strip combined p-stop Teststructures for p-side 1) atoll p-stop varying distance from strip 2) conventional p-stop varying width 3) combined p-stop varying distance from strip Baby sensor 1 p-side: 512 strips 50 µm pitch 1 interm. strip n-side: 512 strips 100 µm pitch 1 interm. strip atoll p-stop 1) 2) 3) Teststructures for n-side(no GCD) Thomas Bergauer (HEPHY Vienna)

11. News from Micron • Processing of first sensor is finished • is supposed to be tested this week • Last update (29. June): they are currently writing a test software • If OK, final processing of six more sensors this month • Shipping of the first batch end of this month or early next month Thomas Bergauer (HEPHY Vienna)

12. HPK Status Thomas Bergauer (HEPHY Vienna)

13. First batch from HPK • First 20 pieces of 6’’ sensors have been delivered in April 2010 • Technical details: • Dimensions: 59.6 x 124.88 mm • p-side: • Readout pitch: 75 µm • 768 strips • n-side: • Readout pitch: 240 µm • 512 readout strips n-side • P-stop scheme T. Bergauer

14. HPK Polysilicon Resistors T. Bergauer

15. Characterization HPK Sensors • Electrical Characterization done in Vienna and KEK • IV, CV • Stripscan (p- and n-side) • Longterm stability vs. temperature and humidity • Inter-strip resistance • Pull-tests to show bondability T. Bergauer

16. How to bias the DSSD for testing? • 2 strategies: • contacting bias on both p- and n-side (uncomfortable) • contacting bias and n-sub on p-side (easy, bulk tests and strip tests of p-side) • Measurement shows hardly any difference -> we save a lot of trouble!

17. IV Measurements • Consistent between Vienna and HPK measurement (except #2) HPK data Vienna data Manfred Valentan (HEPHY Vienna)

18. CV Measurements • Shows full depletion voltage between 50 and 60V KEK data Vienna data Manfred Valentan (HEPHY Vienna)

19. Long-term IV measurement • Apply bias voltage (100 volts) for 1 week • Measure currents continuously while varying r.H. • => sensors stable with time I [uA] Time [10 min] Thomas Bergauer (HEPHY Vienna)

20. Stripscan (Sensor #4) n-side p-side Thomas Bergauer (HEPHY Vienna)

21. Strip failures in the HPK data Onuki-san HPKinspects all strips in the DSSD. HPK categorizes strip failures as below: - Coupling short - AC AL short - AC AL open - Implant short - Implant open Almost all of failures are implant short and open in P-side. No or only few coupling shorts, AC AL shorts and AC AL opens exist.

22. Correlation HPK <-> Vienna Data (p-side) Onuki-san Thomas Bergauer (HEPHY Vienna)

23. Correlation HPK <-> Vienna Data (n-side) Onuki-san Thomas Bergauer (HEPHY Vienna)

24. Measurement of the interstrip resistance SMU 1 Method seen in Karlsruhe -100V GND applies bias voltage Electrometer SMU 2 A 0...3V (5V) A GND Current at 0V is strip leakage current, interstrip resistor value from slope of current when ramping GND ramps potential on neighbouring DC pad -> Bias resistor value from slope of current Thomas Bergauer (HEPHY Vienna)

25. Measurement of the interstrip resistance HPK sensor 8, n-side, strip 1-2 HPK sensor 8, p-side, strip 6-7 • I_strip = -5.14 nA • R_int = 92.6 GΩ • R_poly = 2.8 MΩ • I_strip = 1.498 nA • R_int = 158.4 GΩ • R_poly = 17.9 MΩ • PRELIMINARY! These results are from first tests of the method! • First stripscan using this method currently ongoing Thomas Bergauer (HEPHY Vienna)

26. Bonding test • Bonding pad metal feels very soft • > we performed a bond test • p-side : • Corner: 8.73g, σ = 2.2g (non-optimized bonding parameters) • Center: 11.5g, σ = 0.6g (optimized parameters) • n-side : • Corner: 12.2g, σ = 0.6g (optimized parameters) • Center: 12.1g, σ = 0.7g (optimized parameters) • Conclusion: although the metal feels soft when contacting by hand, the bond wires hold tight Thomas Bergauer (HEPHY Vienna) 27

27. Soft metal issue CMS SSSD for comparison n-side p-side Thomas Bergauer (HEPHY Vienna)

28. Scratches & Marks: p-side • Triangular stains • visible by eye • visible under the microscope • occurs on every sensor Thomas Bergauer (HEPHY Vienna) 29

29. Scratches & Marks: n-side • Round scratches • occur on every sensor • maybe due to automatic sensor handling? Thomas Bergauer (HEPHY Vienna) 30

30. Residues and other optical issues Thomas Bergauer (HEPHY Vienna)

31. Last point: BEAM test and Gamma Irradiation Thomas Bergauer (HEPHY Vienna)

32. Thomas Bergauer (HEPHY Vienna)

33. Gamma Irradiation • I was in contact with a person of SCK-CENin Mol, Belgium • They have a very strong gamma source (Co-60) with 30kGy/h • 20 Mrad will be accumulated in 8h • Costs are 2195 Euro (=242k¥) Thomas Bergauer (HEPHY Vienna)

34. What to test? • DSSDs from both HPK and Micron • While powered with HV and read out with origami (=test of APVs, hybrid,…) • Micron p-stop test structures • Other stuff? • Space available: Cylinder with approx 40cm diameter and 60 cm height 1) 2) 3) Markus Friedl (HEPHY Vienna)

35. Schedule • Test beam at SPS (CERN): • 27. September until 11. October 2010 • Idea is to have gamma irradiation in between, which means: • Test Origami ladder and trapezoidal module at CERN (S/N,…) 4 days • Irradiate (3 days with travel) • Re-Test modules at CERN (2 days) • Fits perfectly within two weeks in autumn Thomas Bergauer (HEPHY Vienna)

36. Summary Thomas Bergauer (HEPHY Vienna) • Still waiting for delivery of 1st batch of trapezoidal sensors from Micron • HPK delivered first batch in April • IV behavior reasonable • CV measurements: full depletion voltage ~60V • We are not fully sensitive to their list of single strip failures • Some scratches, residues and soft metal • This is the first try for HPK to produce DSSD on 6” • In summary, sensors are of reasonable quality • HPK is not satisfied itself and delayed delivery of second batch • We are eagerly waiting to see their improvements • Beam test at CERN and Irradiation in Belgium in September/October 2010 under preparation

37. Stripscan Sensor #8 (n-side) • I_strip= -3.31 nA • R_poly=2.76 Mohm • C_ac=186.83 pF • No pinhole • HPK: AC AL short at strips 275/276 - could be verified by C_acmeasurement! Thomas Bergauer (HEPHY Vienna)