Hysteresis@TIB.Test.Beam

1. Hysteresis@TIB.Test.Beam by Anna Macchiolo INFN and University of Florence Test Beam Meeting Tracker Week October 23rd, 2003 C. Civinini – INFN Firenze -“Hysteresis”

2. RUNS 1196-1204, 120 GeV Muons Scan # 1 TIB (peak) RUNS 30024-30054, 120 GeV Pions Scan # 2 TIB (deconvolution) RUNS 30133-30175, 120 GeV Muons Scan # 3 TIB+TOB (deconvolution) Introduction A hysteresis effect has been observed in the TIB modules S/N values depend on the voltages at which the modules have been biased before (memory of the recent biasing history) During the test beam in May 2003 several voltage scans have been performed(0  Vmax 0) C. Civinini – INFN Firenze -“Hysteresis”

3. Modules and sensors in the beam-test • The TIB modules (equipped with sensors HPK) where the beam was impinging during the voltage scan were: Mod #2 – IB2 302 202 261 065 24 V-depl. =180 V (substrate)=2.5 KW cm Mod #5 – IB2 302 202 261 242 41 V-depl= 138 V (substrate)=3.2 KW cm • All the 6 TOB modules (equipped with sensors OB2 STM ) were hit by the beam C. Civinini – INFN Firenze -“Hysteresis”

4. Module # 6 TIB- Dec. Mode • In a “standard” operative procedure (bias voltage driven directly from 0 V to the working point) the expected performance have been found, both for TIB and TOB modules Deconvolution mode S/N (TIB)~18 @350V S/N (TOB)~24 @350V C. Civinini – INFN Firenze -“Hysteresis”

5. Scan # 1 – Peak – TIB Modules time C. Civinini – INFN Firenze -“Hysteresis”

6. Scan # 2 – Deconvolution –TIB Modules S/N time C. Civinini – INFN Firenze -“Hysteresis”

7. Scan # 2 – Deconvolution –TIB Modules Signal Noise t t C. Civinini – INFN Firenze -“Hysteresis”

8. Scan # 2 – Deconvolution – TIB Modules t • Decreasing the bias voltage the cluster width increases • The difference in the average cluster width between the two modules are due to the different inclination wrt the beam direction C. Civinini – INFN Firenze -“Hysteresis”

9. Scan # 3 – Deconvolution – TOB Modules t C. Civinini – INFN Firenze -“Hysteresis”

10. How the hysteresis effect shows up for the TIB modules in the beam-test data ? For instance in deconvolution mode at 300 V: • The signal decreases (8 %) • The noise increases (9 % ) • S/N decreases (17 %) • The cluster width increases (16 %) C. Civinini – INFN Firenze -“Hysteresis”

11. From beam-test to the lab • The increase of the cluster width and of the noise can be linked to an increase in the inter-strip capacitance (C_int) of the sensors. • In the lab we studied the C_int behavior repeating bias cycles similar to those done in the beam test. Lab measurement scheme (PQC) C. Civinini – INFN Firenze -“Hysteresis”

12. Inter-strip capacitance measured in the CAP-TS-AC structure HPK 20 minutes @ 450 V C. Civinini – INFN Firenze -“Hysteresis”

13. Inter-strip capacitance measured in the CAP-TS-AC structure HPK DC-int (250V) = 5 % C. Civinini – INFN Firenze -“Hysteresis”

14. Inter-strip capacitance measured in the CAP-TS-AC structure HPK DC-int (250V) = 10 % C. Civinini – INFN Firenze -“Hysteresis”

15. Time dependence of the inter-strip capacitance Measurement as a function of time at constant bias 0.718 pF 22’ 3’30” Measurement done @ V_bias = 250V when the structure has been kept 75 minutes @ 450V HPK C. Civinini – INFN Firenze -“Hysteresis”

16. Inter-strip capacitance measured in the CAP-TS-AC structure STM No hysteresis effect observed in the same experimental conditions C. Civinini – INFN Firenze -“Hysteresis”

17. A hypothesis • From PQC standard measurements we know a hysteresis effect that affects HPK test structures only: the interstrip resistance drops by several orders of magnitude (from hundreds of G to hundreds of M) when the substrate has been biased to high voltages • This phenomenon verifies only when the environment relative humidity is quite high (>30-40 %). • The relative humidity measured for the TIB modules during the beam test is: Scan 1 (runs 1196-1204) RH ~ 45-50 % Scan 2 (runs 30024-30054) RH ~ 45-50 % Scan 3 (runs 30142-30175) RH from 60 % to 4% (nitrogen flux in TIB box) • During all the beam test time the TOB modules have been kept under nitrogen with low relative humidity (~ 4 %) • All the lab measurements shown before have been done with RH ~ 45-50 % C. Civinini – INFN Firenze -“Hysteresis”

18. TIB test beam relative humidity C. Civinini – INFN Firenze -“Hysteresis”

19. Under low humidity conditions… RH < 25% HPK C. Civinini – INFN Firenze -“Hysteresis”

20. At relative humidity close to 0% 360 GW IV on mini-sensor up to 700 V R-int before and after bringing the substrate at 700 V 147 GW from J.C. Fontaine (PQC Strasbourg) C. Civinini – INFN Firenze -“Hysteresis”

21. At relative humidity close to 50% 21 GW R-int before and after bringing the substrate at 700 V. 9 GW Hysteresis from J.C. Fontaine (PQC Strasbourg) C. Civinini – INFN Firenze -“Hysteresis”

22. Finally… Noise measurements, inv on, common mode subtracted done with the ARC system Noise Noise RH ~ 50 % RH < 10 % t C. Civinini – INFN Firenze -“Hysteresis”

23. Scan 3 – Deconvolution – Module 2 TIB • During the first ramp up the TIB box has been fluxed with nitrogen, so the other measurements have been taken with a relative humidity close to 3% Order of magnitude of the hysteresis (15%) in the previous scan C. Civinini – INFN Firenze -“Hysteresis”

24. Conclusions • The hysteresis effect observed for the TIB modules during the X5 beam test voltage scans can be related to the interstrip capacitance and resistance behaviour of the HPK sensors • PQC studies show that hysteresis effects on Cint and Rintdisappear if the measurements are done at relative humidity less than 35-40% • Hysteresis free results are obtained for the TIB noise lab measurements (done after the beam test) and for the TIB S/N scan performed during the May test beam at low relative humidity • Since ST sensors don’t show any hysteresisa possible mechanism that produce this effect could be traced to the difference in the oxide thickness and composition among the two manufacturers. C. Civinini – INFN Firenze -“Hysteresis”