GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 1

GLAST Large Area Telescope:GLAST Large Area Telescope:

Tracker SubsystemWBS 4.1.4

6B: Silicon Strip Detector Receiving and Inspection

Alessandro BrezINFN Pisa

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 2

SSD Acceptance TestingSSD Acceptance Testing• LAT Tracker Silicon Strip Detectors go through two levels of testing:

– QA provisions: LAT-CR-82 (released); Includes complete plan for verification of the requirements and specifications.

– At the manufacturer, Hamamatsu Photonics (HPK):• Detector IV curve (leakage current versus bias voltage)• Detector CV curve (capacitance versus bias voltage)• Test for bad channels (opens, shorts, broken capacitors)• Specified in the procurement spec: LAT-DS-11 (released)

– At INFN Pisa or INFN Perugia• Measure alignment of the cut edges with the lithography (initial

all SSDs but later changed to a sampling)• Repeat IV and CV curves (all SSDs)• Test methods: LAT-TD-85 (released)• Dimensional and Electrical Test procedure: LAT-TD-527

(released)

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 3

SSD Lot TestingSSD Lot Testing• Sample testing done on structures fabricated on the same wafers as

the SSDs. See LAT-CR-82 for the details of the plan.• At the manufacturer (Specified in LAT-DS-11):

– Resistance of poly bias resistor and aluminum electrode– Manufacturing traceability data, including yield

• By LAT institutes (Hiroshima University):– Radiation tolerance (60Co exposure)– Wire-bonding pads– Coupling capacitance– Capacitor breakdown voltage– Interstrip capacitance– Strip isolation

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 4

SSD Receiving & InspectionSSD Receiving & Inspection• Detailed procedures are in LAT-TD-527• Carried out on identical equipment operated by

– INFN Pisa (in Pisa)– INFN Perugia (in Terni)

• All work is done in Class-100k clean rooms (actually better) and conforms with the Tracker contamination control plan, LAT-MD-228

• Includes Visual, Dimensional, and Electrical Inspections• Resulting data are analyzed and compared with HPK data.• Data are archived in the Tracker Fabrication Database (MS Access);

Summaries are available on the Pisa web site.• Nonconforming wafers are set aside for review and possible

rejection and negotiation with HPK.• Status (March 7, 2003):

– 5261 SSDs received– 4304 tested; 165 reviewed; 38 rejected

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 5

Shift and Rotation

0

50

100

150

200

250

300

350

400

450

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

microns

ShiftRotation

Shift Rotation

Average 0.7256 0.5913

Min -10.99 -8.600

Max 10.485 14.679

RMS 2.0713 2.4900

1689 entries

Dimensional InspectionDimensional Inspection• Specified dicing tolerance: 20 m• Tolerance achieved: < 15 m• Moved to sample testing:

– 3 SSDs from the lot are measured– If any of the 3 show deviations

>10m, then all SSDs in the lot are measured

A

BC

D

305m

200m

300m

SSD Fiducial Marks

Dicing accuracy of the first 1689 flight SSDs

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 6

Electrical TestsElectrical Tests• Individual strips are not contacted (was done at HPK)• Measure IV and CV of the detector as a whole to verify HPK results

_ 

+ Switch positions:

1=I-V curve2=C-V curve

 

2

 

1

 

1

 2

 

2

 

1

 _ 

+ 

 KEITHLEY

2410 Source Meter

 

FIXTURE 

AGILENT4284 A

LCR Meter

 

Bias pad

  SSD

  CHUCK 

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 7

Leakage CurrentLeakage CurrentSpecification: leakage current <500 nA at 25C and 150 V

Leakage current at 150 V

0

50

100

150

200

250

300

350

400

450

500

0 20 40 60 80 100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

Leakage current (nA)

PisaHPK

Pisa HPK

Average 111.96 198.03

Min 40.083 74.510

Max 1788.4 618.79

RMS 62.449 60.551

4304 entries

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 8

Depletion Voltage (from CV curve)Depletion Voltage (from CV curve)Specification: full depletion at less than 120 V bias.

Depletion voltage

0

100

200

300

400

500

600

700

800

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

105

110

115

120

125

130

135

140

145

150

Depletion voltage (V)

PisaHPK

Pisa HPK

Average 66.983 68.012

Min 0 25

Max 145 135

RMS 19.620 19.408

4304 entries

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 9

Position of defects along SSD - all 1903 detectors

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

1 14 27 40 53 66 79 92 105

118

131

144

157

170

183

196

209

222

235

248

261

274

287

300

313

326

339

352

365

378

strip number

num

ber o

f def

ects

Strip defects types

32

21

7

2

7

1

1

1

coupling shortstrip isolationpoly-si resistorimplant shortac-al openimplant openstrip openleaky strip

HPK data statistics: defects HPK data statistics: defects analysisanalysis

bad strips/total strips=72/73075210-4

GLAST LAT Project March 24, 2003

6B Tracker Peer Review, WBS 4.1.4 10

ConclusionsConclusions• The SSD dimensional and electrical inspection procedure is well

under way (> 38% complete).• The results confirm the high quality of the HPK SSDs.• The dicing accuracy is more than adequate for our ladder assembly

methods, which rely on mechanical alignment.• Very few wafers fail the stringent electrical requirements.• The second test site (Terni) is fully operational, so there will be no

conflict between this activity and other Tracker fabrication activities.• The testing is well ahead of (and can easily keep up with) the ladder

assembly, so there are no schedule issues with this procedure.