1. 23.01.2002 IEKP - Universität Karlsruhe (TH) 1 Preliminary Pinhole Studies (not final) F. Hartmann IEKP - Universität Karlsruhe (TH) Creation of defined number of pinholes per chip Increase of leakage current according to LHC years also defines the voltage over the dielectric (with Rpoly= 1.8MOhm) o Effect of pinholes on readout o Gain vs. number of pinholes?? o Gain vs. leakage current (= years of LHC operation) Conclusion

2. 23.01.2002 IEKP - Universität Karlsruhe (TH) 2 Power Consumption 60  A/cm 3  I leak (-10°C)= 270  A (W6b)  540µA (module)  P(500V, -10°C)=135mW/sensor P ~ U FD I ~ d 2 d ~d 3

3. 23.01.2002 IEKP - Universität Karlsruhe (TH) 3 Setup P+ Al SiO2 DC AC bond Ichannel=Itot / #channel=Itot/1024 Vdrop=Istrip*Rpoly = Istrip*1.8MOhm  300µA/1024 *1.8MOhm= 0.5V  30µA=0.05V ... Array of IR LED for cont. illumination  increase in total current with standard reverse bias. Bonding artificial pinholes on purpose!

4. 23.01.2002 IEKP - Universität Karlsruhe (TH) 4 Noise vs. leakage current Vb=500V; Il=0.3µA Vb=500V; Il=30µA Vb=500V; Il=300µA Pinholes highly leakage current dependent Very difficult to tag at starting current level

5. 23.01.2002 IEKP - Universität Karlsruhe (TH) 5 Vb=500V; Il0.3µA Vb=500V; Il 120µA Vb=500V; Il 30µA Vb=500V; Il 300µA Pedestals vs. leakage current NO change

6. 23.01.2002 IEKP - Universität Karlsruhe (TH) 6 Gain vs. leakage current (calibration) (Vbias=500V) (5&6 pinholes) Il 0,3µA  ph 330 Il 90µA  ph 260Il 60µA  ph 280 Il 30µA (Vdrop=0.05V)  ph 300 Preliminary p p p p pp

7. 23.01.2002 IEKP - Universität Karlsruhe (TH) 7 Gain vs. leakage current (calibration) (Vbias=500V) (5&6 pinholes) Il 150µA  ph 255 Il 240µA  ph 255 Il 300µA (0.5V)  ph 255 Preliminary No change in gain at leakage currents above 150µA (up to 300µA) ??

8. 23.01.2002 IEKP - Universität Karlsruhe (TH) 8 Calibration/Gain No pinholes 4 pinholes 3 pinholes p p Vbias=500V; Il 60µA (Vdrop=0.1V)

9. 23.01.2002 IEKP - Universität Karlsruhe (TH) 9 Common mode 0 pinholes 10 pinholes Vbias = 400V Il = 200µA

10. 23.01.2002 IEKP - Universität Karlsruhe (TH) 10 Conclusion We bonded up to 10 pinholes per chip and imposed a current of 300µA/modules (330nA/channel; Vdrop = 0.5V) ~ 5 years of LHC operaton. No saturation of chip seen; but final current level not yet reached. Only 300µA instead of 500-600µA Gain loss and change in common mode with increasing leakage current and number of pinholes Pinholes easy to tag with high current.

11. 23.01.2002 IEKP - Universität Karlsruhe (TH) 11 IV-Curve before/after Irrad.

12. 23.01.2002 IEKP - Universität Karlsruhe (TH) 12