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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.