Experience with CiS detectors at NIKHEF

1. Experience with CiS detectors at NIKHEF Meeting on CiS reception tests, 16 April 2003 Fred Hartjes, Sandra Muijs, Experience from Five-module miniproduction of spring 2002 Two prequalifier modules February 2003 Latest CiS batch 5195 Improvement by burn-in Conclusions

2. Introduction

3. IV characteristics • Example: Module 15 (CiS batch 5194) • MPI curve shows breakdown starting at 250 V • For NIKHEF curve breakdown starts at 400 V • General tendencies of batch 4893 and 5194 • Breakdown starting at 400 V • Breakdown disappearing after assembly and wire bonding • All modules can held 450 V

4. IV curve for module 16 • Batch 5194 • Again early breakdown observed by MPI, not seen by NIKHEF • Again breakdown above 400 V disappearing after assembly and wire bonding

5. IV curve for module 14 • Batch 5194 • No MPI data for detector 01, value of 10 is doubled • Again breakdown above 400 V disappearing after assembly and wire bonding

6. IV curve for module 13 • Batch 4893 • No curve from on database • Breakdown at low bias current, no breakdown at high bias current

7. IV curve for module 12 • Batch 4893 • No curve from on database • Initial current extremely low, back to normal level after wire bonding

8. IV curves of all 5 modules AFTER wirebonding • Curves almost alike • (almost) no sign of breakdown

9. IV curves module 511 IV curves at different stages during the assembly: In blue, the sum of the IV curves of the individual wafers (reception tests) In orange, the corresponding measurements made by CiS In green, the sum of the front and back wafer after they have been glued to the spine In red, the IV curve of the module, after bonding The breakdown behaviour of the unbonded glued wafers is observed before in earlier modules made at NIKHEF. It appears to be typical behaviour for CiS wafers: as long as they are unbonded, the behaviour is rather unpredictable.

10. IV curves module K5-512 IV curves at different stages during the assembly: In blue, the sum of the IV curves of the individual wafers (reception tests) In orange, the corresponding measurements made by CiS In green, the sum of the front and back wafer after they have been glued to the spine In red, the IV curve of the module, after bonding The breakdown did not disappear after bonding, so these wafers were indeed not good enough to build modules (NB they were selected for dummy modules only).

11. Training of sensor 5195-4 by successive IV measurements • Breakdown voltage gets higher after each measurement • Low Ibias at 100 V => low Vbreakdown • High Ibias at 100 V => high Vbreakdown

12. Burning-in sensors • Batch 5195 • Stable after 80 min • Batch 5005 • Stable after 5 min

13. Sensor 5195-4 after burn-in • Measured a few minutes after burn-in • Almost flat after depletion • Ibias about 100 nA higher than before burn-in • No sign of breakdown until 500 V! • Starting at negative Ibias • Absolutely no hysteresis above 180 V

14. Sensor 5005-10 before and after burn-in • Improvement less striking than for batch 5195 • Minor breakdown starting at 470 V

15. Conclusions • Sensor properties strongly differing between different batches • Not possible to verify the correct sensor handling during module assembly (experience of five-module miniproduction) • Early breakdown often accompanied by low bias current • Grounding strips makes IV curves of two different batches almost equal