March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 1 Summary of Sensor Quality Tests List of Problems F. Hartmann, CMS Tracker Collaboration

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 2 Total Number of Sensor Delivered TypeReceivedMeasuredRejectedAccepted* OB OB W5A W5B W6A W6B W7A W7B *Passing CMS QTC tests February 14, 2003

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 3 Summary of Quality Tests Restrict summary and discussion to sensors delivered after December 1, 2002 (introduction of new QA steps): 187 OB232 W7A 20W5B12 W7B 10W6B 261Sensors in total MeasuredAcceptedRej. Optic.Rej. IVRej. strips %2%3.7%7%

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 4 Sensors to be rejected Sensors measured in Pisa not included.

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 5 Checklist for Pre-Series Qualification Pre-series completedNot yet Delivery procedureST resumed with notification, still some inconsistencies Bar codeo.k. Data formato.k., several files missing Mask designCorrect for all sensors W7B test structure wrong QTC IV problem, scratches, number of bad Cac PQCo.k., assuming ST applies Flatband Voltage cut at 10 V Longtime testo.k. p-irradiationo.k. n-irradiationo.k. Bonding testo.k., 2 batches needed cleaning ? % accepted sensors ~ 90 % Goal of qualification not yet reached.

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 6 Optical Inspection I Quality of cut edges has significantly improved. Still some sensors outside specifications (last delivery). Further improvement needed  m 1464  m 549  m Back view Still 4 rejects out of 261

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 7 Optical Inspection II Many scratches on the surface of almost all sensors: In many cases no electrical failure. In other cases broken or shorted aluminium lines ! Where and how are these scratches introduced ? Can these scratches be avoided with new scheme skipping IV after cutting? Agreed to try on 1000 OB2 sensors. But then we are even more concerned about cutting defects effecting the IV performance. (On single strip basis & and on overall performance!) bad Cac short

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 8 Bad Cac values Two cases: Bad Cac values correlated with scratches. (shorts & opens) One batch (4 sensors): All sensors having hundreds of too low Cac values.  AUTOMATIC Cac CAPACITORS MEASUREMENT Is this or will this be introduced ????

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 9 IV problem - breakdown I Limit Correlation observed: Sensors with higher leakage current have strips with high leakage currentAND strips with high leakage current are often in areas with scratches! Example of W7A, W7B & W6A, W6B sensors:

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 10 IV problem - breakdown II Time dependence observed for some sensors. Important to agree on test procedure.

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 11 Same IV up to “soft strip breakdown” First strip Second strip

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 12 Leaky strips -- scratches

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 13 Hints Almost each high IV sensor has a few „high leaky“ strips! Σ leaky strips ~ IV (  few strips drive IV) EACH leaky strip is scratched ! – not all scratched strips are leaky Clear correlation between IV and leaky strips and scratches on sensors observed! No IV-breaks on Minisensors!  different handling !  Scratch test: –Scratchtest on minisensors to reproduce effect Needle Pencil (2B) screwdriver

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 14 Scratches on minisensor „Soft“ scratches with probe needle Carbon residues of pencil

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 15 Deep scratches on minisensor „Not-so-SOFT“ scratches with screwdriver

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 16 x3 x 70 Total current Single strip current Global IV and Individual strip IV

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 17 A few single strips show high leakage current! Undamaged 400V: Ileak ~ 0,2nA x 192 strips ~ 35nA IV ~ 38nA Damaged 400V:  Ileak damaged strips ~ 55nA  Ileak all ~ 100nA IV ~ 120nA Strip scan (Current)

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 18 Idiel on scratched Minisensor Effect is located in the Al layer, above the oxide!  CMS sensors have metal strip overhang!!! Scratches remove the overhang and introduce pointlike defects No pinholes created!

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 19 Scratch on bias & guard (minisensor)

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 20 Preliminary field simulations (with ISE TCAD)

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 21 Solution!?! Scratches -obviously happening very late in the measuring procedure at ST- are critical! Avoiding scratches will certainly improve the yield with respect to CaC (strip failure), leaky strips (strip failure) and to global IV! BUT There is no guarantee, that avoiding scratches solves ALL problems! Is it enough to skip the IV after cutting?????

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 22 Update Contact Persons CMS ST GeneralM. Krammer G. Fallica Technical M. Krammer G. Valvo Mask DesignE. FocardiG. Valvo Contract and Payment M. MannelliG. Di Stefano ScheduleA. CattaiG. Mendola ShipmentsM. KrammerG. Kauerauf Data Files

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 23 CMS Tracker collaboration has to produce ~15000 silicon detector modules until end of We need to procure ST sensors in 2 years production time. During full production only samples of sensors can be tested by CMS. We have to relay on Quality Control by ST ! Acceptance limit on sensor failure is max 1% ! Due to delays in pre-series production the time schedule is very tight and we have to compress the module production. CMS Module Production

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 24 Example of a CMS Module A module consists of 2 sensors, electronic hybrid, 4-6 APV chips, pitch adapter, carbon frame, etc. For many sensors: The first test of silicon sensor after ST quality control is on an assembled module. Replacement of single sensors is basically impossible! The present failure rate of 10% is not acceptable  20% of all modules would fail!

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 25 Strip failure: Add. measurements by CMS –CaC AUTOMATIC Cac CAPACITORS MEASUREMENT!?! –Leaky Strips (scratches only??) IV (scratches only??) Optical inspection has to be improved! Some improvements in the shipping logistic needed! Acceptance rate must be increased to 99% –Otherwise sensor failure will be detected about 1 year later (2 sensors assembled together with electronics and mechan. parts) Summary

March 17, 2003 Catania, Meeting ST - CMS CMS Sensor Quality Frank Hartmann – University of Karlsruhe 26 Strip leakage current