# Presentation: 680069

## The D0 Silicon Tracker

- _Outline:_
- Tracker design
- Detector delivery & testing
- Readout
- Mechanical assembly
- Prospects & conclusions

- 8th International Workshop on Vertex Detectors
- June 20-26, 1999 Texel, NL

**Frank Lehner**
**Fermilab**
**on behalf of the **
**D0-Collaboration**

## The D0 Upgrade

- Run II will deliver 100x increase in luminosity with 132 and 396 ns bunchcrossing
- Upgraded muon
- New calorimeter electronics
- Forward/backward preshowers
- 2 Tesla solenoid
- Upgrades to trigger & DAQ
- Sci. Fiber-tracker
- Silicon detector

## Tracker Design

- Major Subsystems:
- single sided ladders
- double sided ladders (20)
- double sided ladders (900)
- F-Disks
- H-Disks

## Tracker Design

- Driven by large (=25cm) interaction region
- 3D track reconstruction capability
- good acceptance for high pT-tracks (top-decay)
- Si-based tracking/vertexing in forward region (2<||<3)
- Six 12 cm barrel modules with interspersed disks (F-disks) for forward tracking
- barrels consists of 4 layers
- external large area disks for forward momentum resolution
- detectors and inboard electronics radiation hard up to 3 MRad

## Tracker Design

- Total ~793,000 channels
- intermediate in size between previous generation of collider detectors and LHC

## Silicon Detectors

- Barrels:
- Single sided barrels detectors (144)
- Properties:
- single sided AC coupling
- Pitch 50 m
- Status:
- all detectors received
- tested, 75% yield @ 99.5% good strips

## Silicon Detectors

- Barrels:
- 20 stereo barrel detectors (432)
- Properties:
- double sided
- 50m (p-side) and 62.5 m (n-side) pitch
- Status:
- have ~50% A-Grade in hand
- get sensors in reasonable rate:

## Silicon Detectors

- Barrels:
- 900 stereo barrel detectors (144)
- Properties:
- double sided, double metal in 6’’ technology
- 50m (p-side) and 153 m (n-side) pitch
- Status:
- final design recently approved
- first good detectors arrived & tested

## Silicon Detectors

- Disks:
- F-wedge detectors (144)
- Properties:
- double sided wedges with ±150
- 50 m (p-side) and 62.5 m (n-side) pitch, variable strip length
- Status:
- under production at Micron, but slowly
- additional vendor
-    found, split order
-    between Micron
-    and Eurisys

## Silicon Detectors

- Disks:
- H-wedge detectors (384)
- Properties:
- 40 m strip pitch
- single sided, AC coupled
- glued back to back with ±7.50
- Status:
- produced at ELMA near Moscow
- already ~300 in hands
- delivery has held steady for ~ 8 months and will be finished this summer

## SVX-II Chip

- 128 channel device (5mW/channel)
- noise: ~350*e *+ 50*e/pF*
- dimension: 6.4 x 9.7 mm
- preamplifier, 32 cell pipeline,  8 bit ADC and sparsification
- programmable test patterns, ADC ramp, pedestal, bandwidth and polarity
- designed for 53 MHz readout & digitization
- all features have been tested and are working
- have all SVX-II chips in hand

## Readout Scheme

- ladder

- HDI pigtail

- Sequencer

- VME unit:

- Level 3

- VBD

- Monitor
- system

- Transition card

- Interface card

- Low mass cable (8ft)

- High mass
- cable

- VRBs

- VRBC

- Optical
- Link

## 10% System Test

- Full crate readout test:
- with Sequencer/VRB/Level 3
- 600 Hz DAQ rate, 12Mbyte/s
- > 20,000 equivalent channels
- error rate < 10-14 achieved
- understanding of cabling, electronics and system problems
- test will turn into a real 10% system test this summer...

## Detector Testing I

- Quality control of sensors done at Micron & Fermilab
- Have D0 technicians & probe equipment directly at vendor
- Check on all detectors:
- leakage currents (<0.5A/cm2 @ 2@Udepl)
- depletion voltage (20<Udepl<60V)
- bias & interstrip resistances    (1<Rbias<10 Mohm; Rinter~GOhm)
- coupling capacitors (15pF/cm)
- search for shorted capacitors  (breakdown >100V/50V for p/n-side)
- allow totally 2% bad strips on each side

## Test results 900 DSDM

- Coupling Capacitors
-      ~30pF/cm

- leakage currents

- bulk capacitance
- Udepl~18V

## Detector Testing II

- Major problems for some batches were:
- broken vias in double metal layer for 900 detectors
- cured by thicker metallization
- too high Rbias (15-30 MOhm, instead <10 MOhm)
- variation of Rbias by up to ±50% across the strips
- caused by plasma etching, soon under control
- low interstrip resistances on p-side for F-Disks & 900 detectors
- contaminated Nitrogen purge gas in the annealing process?
- mobile charge in Oxide?
- additional cleaning/rinsing process introduced

## Low Interstrip Resistance

- Temperature aging (@T=2500C) under bias stress (±10V) for MOS structures:

- Flatband Voltage shift indicates positive (Na+) mobile charge in SiO2 layer (~1011cm-2)
-  leads to loss of strip isolation?
-  need better control of oxidation process

## Ladder (Hybrid-) Design

- Barrels:
- active (cooled) and passive Beryllium support and bulkheads
- operation temperature ~5-10 0C
- ladder alignment using machined posts/notches on bulkheads/ladders
- ladder placement accurate to 20m and measured to <5m (ZEISS CMM)
- barrel/disk geometry with 2mm gap forces   to move electronics and cables inboard
- flexible HDI tails

## High Density Interconnect (HDI)

- Kapton based flex circuits, double sided with 0.2 mm pitch, for chip mounting
- Barrels/Disk geometry requires 9 types  (3 differ only in pigtail length)
- all HDIs for 3- & 9-chip ladders received
- other types under production
- Fabrication:
- visual inspection
- Lamination to Be Substrate
- Component, Chip mounting at Promex
- Testing, Burn-in and encapsulation

- H-disk HDI 6-chip

- 9-chip barrel HDI

## Ladder Assembly

- Successfully started with 3-chip and 9-chip ladder production
- big production job: ~1000 ladders with ~1.5 Million wirebonds
- careful tests of each ladder on teststands
- started now to assemble first barrel/disk

## Ladder Fabrication 

- Aligning silicon
- on fixture

- Gluing HDI

- Allowing to cure
- under weight

## Ladder Fabrication

- bonding

- Gluing rails and
- Be-substrate

- Flip over and glue
- HDI on n-side

## Laser Test Stand

- Laser signal

- Plateau
- charge collection

- Bad channels

## Overall Status

## Conclusions

- Much progress has been made over the last 1/2 year:
- successfully started ladder production
- commissioned test stands
- most parts for production in hand
- ramped up detector delivery
- Some issues remain:
- detector delivery rather slow for       F-disks & 900 detectors
- quality control of production
- More work is needed:
- 10% system test
- barrel assembly
- cables & installation

## Conclusion 

- Conclusion

- The D0 Silicon Tracker is under construction

- and will be ready for Run II data
- in the summer of 2000