1. Hysteresis@TIB.Test.Beam by Anna Macchiolo
INFN and University of Florence
Test Beam Meeting
Tracker Week
October 23rd, 2003
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

2. C. Civinini – INFN Firenze - “Hysteresis”
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)
Scan # 1 TIB (peak)
RUNS , 120 GeV Muons
Scan # 2 TIB (deconvolution)
RUNS , 120 GeV Pions
RUNS , 120 GeV Muons
Scan # 3 TIB+TOB (deconvolution)
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

3. C. Civinini – INFN Firenze - “Hysteresis”
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 – IB V-depl. =180 V (substrate)=2.5 KW cm
Mod #5 – IB V-depl= 138 V (substrate)=3.2 KW cm
All the 6 TOB modules (equipped with sensors OB2 STM ) were hit by the beam
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

4. C. Civinini – INFN Firenze - “Hysteresis”
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
S/N
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

5. C. Civinini – INFN Firenze - “Hysteresis”
Scan # 1 – Peak – TIB Modules
time
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

6. C. Civinini – INFN Firenze - “Hysteresis”
Scan # 2 – Deconvolution –TIB Modules
S/N
time
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

7. C. Civinini – INFN Firenze - “Hysteresis”
Scan # 2 – Deconvolution –TIB Modules
Signal
Noise t t
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

8. C. Civinini – INFN Firenze - “Hysteresis”
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
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

9. C. Civinini – INFN Firenze - “Hysteresis”
Scan # 3 – Deconvolution – TOB Modules t
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

10. C. Civinini – INFN Firenze - “Hysteresis”
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 %)
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

11. C. Civinini – INFN Firenze - “Hysteresis”
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)
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

12. C. Civinini – INFN Firenze - “Hysteresis”
Inter-strip capacitance measured in the CAP-TS-AC structure
HPK V
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

13. C. Civinini – INFN Firenze - “Hysteresis”
Inter-strip capacitance measured in the CAP-TS-AC structure
HPK
D C-int (250V) = 5 %
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

14. C. Civinini – INFN Firenze - “Hysteresis”
Inter-strip capacitance measured in the CAP-TS-AC structure
HPK
D C-int (250V) = 10 %
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

15. C. Civinini – INFN Firenze - “Hysteresis”
Time dependence of the inter-strip capacitance
Measurement as a function of time at constant bias
0.718 pF
22’ 3’30”
Measurement V_bias = 250V when the structure has been kept V
HPK
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

16. C. Civinini – INFN Firenze - “Hysteresis”
Inter-strip capacitance measured in the CAP-TS-AC structure
STM
No hysteresis effect observed in the same experimental conditions
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

17. C. Civinini – INFN Firenze - “Hysteresis”
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 ) RH ~ %
Scan 2 (runs ) RH ~ %
Scan 3 (runs ) 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 ~ %
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

18. TIB test beam relative humidity
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

19. Under low humidity conditions…
RH < 25%
HPK
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

20. C. Civinini – INFN Firenze - “Hysteresis”
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)
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

21. C. Civinini – INFN Firenze - “Hysteresis”
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)
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

22. C. Civinini – INFN Firenze - “Hysteresis”
Finally…
Noise measurements, inv on, common mode subtracted
done with the ARC system
Noise
RH ~ 50 %
Noise
RH < 10 % t
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

23. C. Civinini – INFN Firenze - “Hysteresis”
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
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”

24. C. Civinini – INFN Firenze - “Hysteresis”
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 Rint disappear 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 hysteresis a possible mechanism that produce this effect could be traced to the difference in the oxide thickness and composition among the two manufacturers.
23/10/2003
C. Civinini – INFN Firenze - “Hysteresis”