procurement readiness review : detector fabrication, qualification & assembly at india

Procurement Readiness Review: Detector Fabrication,

Qualification & Assembly at India

M D Ghodgaonkar

Electronics Division, BARC, India

PRR Meeting, July 5-6 2001, CERN

• Present statusIn April, 2001, twenty detectors have been measured at CERN by BARC scientists. These detectors qualify the CERN specs

for leakage current and breakdown voltage.

• Production phaseAfter making the mask for the new geometry, production will be started tentatively by the end of November, 2001.


Specification of detector fabricated in India (Batch VI-VIII)

• Average leakage current per strip - 5-10nA

• Average VFD - 60-70V

• Total leakage current at VFD - 0.1-0.5A

• Total leakage current at VFD+150V - 0.1A - 1A

• Breakdown voltage > 500 V


Wafers - 3-5KΩ-cm TOPSIL ( LT ), polished on both sides – Batch I-III 3-5KΩ-cm and 5-10 KΩ-cm TOPSIL ( HT ), polished on both sides – Batch IV-VI 3.5-4.5 KΩ-cm, single sided polished , WACKER ( W ) , Batch VI-VIII

BatchNo

Total noof wafers

DetectorsMeetingSpecs

Remark

I –Aug1999

4 - LT 0 IL very high –microamps,BD very low – 50-100V

II-Oct1999

6 - LT 0 Same as batch # I

III – Dec1999

8 - LT 0 Reasonably good detectors (2) compared to initial 2 batches.IL about 200nA, BD about 500V for about 40% strips.

IV – Feb2000

20 – LT+HT 1 Process almost optimized.Best detector on high resistivity wafer had all strips with noBD upto1000V& IL <25nA. Other good detectors - IL about 100-200nA

V-July2000

30 – LT+HT 1 Passivation and scribing optimized. Reduction of IL by one order – 10-20nAs. 12 out of 16 good detectors with < 6 bad strips – detectors moreuniform

VI – Sep2000

12 – LT+W 4 - Wacker 12 detectors have = 3 bad strips – detectectors more uniform

VII – Dec2000

12 – W 6 Most of the detectors have = 3 bad strips

VIII-Mar2001

21 – W 10 Most of the detectors have = 2 bad strips


Yield of the last three batches fabricated at BELBatch VI - 4/12 wafers, Batch VII - 6/12 wafers,

Batch VIII - 10/21 wafers

0

10

20

30

40

50

60

Batch VI Batch VII Batch VIII

Batch number

Yie

ld (

%)


I-V at differents temperature for detectors after irradiation at Dubna to a neutron fluence of - 4x10^12

n/cm^2, 1- -30C, 2- 15C, 3- -10.9, 4- -30 (Russia)

0

5

10

15

20

25

0 100 200 300 400 500

Bias, V

Rev

erse

cu

rren

t, m

kA Series1

Series2

Series3

Series4


Production plan

• Mask Design for new geometry• Fabrication of Detectors - Production center - BEL, Banglore• Characterization/Testing of detectors - Regional center-BEL, Banglore• Micromodule assembly• Data Base


Details of Production Plan

• Status of the detector production

- The mask for the 6.3x6.3 cm2geometry has been designed. The mask fabrication will be over by the end of August, 2001.

- Test run using the modified mask will be completed by the end of October, 2001

- The production run will be started by the end of November, 2001


- The technology for the detector production has been optimized to produce passivated and scribed detectors of the required specs

- The yield of the last two batches is about 50% ( after passivation and scribing )

- The production center can produce 1000 detectors or more if required, by October, 2004

- The tentative production schedule will be:

2002 - 250, 2003 - 550, 2004 - 200

- The production schedule will be compatible with the overall micromodule production schedule


Tests on wafers at the foundry and some process related details

• Quality of oxide ( oxide charge & interface states), thickness of oxide & passivation ( ellipsometer ), sheet resistance (four probe), junction depth (groove & stain) have been checked on test wafers.

• Wafers were measured before/after passivation, before/after scribing to optimize these processes so that there is no degradation of the detector performance


• The wafers are scribed using a dicing saw (Microautomation 1100, USA). Dicing wheel of 25m width has been used for a through cut of the wafer.

• A layer of 0.8 m PSG (phosphosilicate glass) and 0.3 m of undoped glass is used for passivation

• The wafers are not numbered at the back-side. After scribing they are out put in particle free envelopes which have wafer and batch number and then stored in sealed boxes.

• During production, detectors will be put in mylar envelopes which will have barcodes and will be stored in dry environment.


Tests and MeasurementsRegional center - BEL, Banglore

Silicon sensors tests

- Tests and measurements will be carried out at BEL in a class 100,000 environment. The temperature and humidity will be controlled as required.

- BARC has developed IV and CV measurement systems for automated and simultaneous measurements of 32 strips.


Specifications of setups developed at BARC

IV & CV setup - Automated simultaneous measurements of all 32 strips

- Bias voltage - up to 1000V with resolution of 0.3V

- Current range (IV) - 10A with resolution of 0.3 nA

- Measurement frequency (CV) - 1kHz, 10kHz & 100kHz

- Capacitance range - 500pF with resolution of 0.5pf

The measurement setup has been calibrated with respect to the setup at CERN by carrying out measurements on the same detectors at both places.


• Equipment for measurements ( IV/CV) - Keithley 6517 & 237, HP 4284 is being procured. These instruments will be interfaced using LabView and the software provided by CERN.

• Probe heads for making contacts to strips are being made by BARC and also are being purchased from Russia.

• The geometric compliance measurements will be carried out using jig provided by CERN ( for width ) and by a comparator ( thickness)


Estimation of time for tests and measurements during mass production

- Width - 5 min

- Thickness - 5 min

- Visual inspection - 10 min

- IV - 20 min, CV - 20 min - parallel

- Noise - 15 min?

Total estimated time - about 60 min

Manpower - Three-four persons for eight

hours per day


Micromodule Assembly• Production center - BEL, Banglore- Class 100,000 clean room for assembly

- well equipped hybrid facility with manual/automatic Aluminum wire bonders ( Shinkova, Japan )

- It is possible to carry out bonding of the sensors to the hybrid using 1 mil Al wire

- Skilled man power is available at BEL for carrying out the assembly.

- Alignment/gluing of the detector to the ceramic and then to Al tile can be carried out using alignment tools, substrate and glue supplied by CERN& Dubna

- Manpower for assembly ( gluing and aligning ceramic substrate/Al tile ) - from BEL


Manpower for detector production, testing & assemblyRegional center contact person - Dr S K Kataria

Contact person for detector production, testing & assembly - Anita Topkar

Detector production - BEL, Banglore

Detector qualification tests - BEL, BangloreBARC - Anita Topkar, M Y Dixit, Bharati Agarwal,

Vijay Mishra

Delhi University - Ashutosh Bhardwaj, Kirti Ranjan, Ajay Shrivastava, Ashish Kumar, Sudeep Chaterjee, Manoj Jha

Detector assembly - BEL, Banglore


Data Base

• The data base designed by CERN will be installed at BEL and BARC

• Connectivity at BEL, Banglore will be established for sending the data to BARC

• Connectivity between BARC and CERN will be established so that the data can be sent to CERN


Irradiation center - BARC

Nuclear reactor at BARC - Neutron irradiation can be carried out at different

neutron fluence by selecting the location of the sample in the reactor and by operating at different power levels.

- Neutron spectrum: Depends on power level. Approx.- fast ( 1MeV or above)-30%, epithermal ( 1-2 eV to 1MeV ) & thermal ( 0.025 eV ) - 70 %

Flux - 5E11/cm2/s at 200KW,

1E10/ cm2/s at 4 KW

- Time for irradiation up to 2x10E14 - 15-20 min at 200KW power


- Irradiation can be carried out without bias and at room temperature

- Detectors will be stored in a deep freezer at

-50C after irradiation. Total or individual strip current and capacitance will be monitored. One set of equipment will be kept at BARC for these measurements


Summary• Production of preshower silicon detectors will

be started at BEL by the end of November, 2001.

• The test and measurement equipment required for carrying out detector quality check is being procured and is also partly available right now.

• By the time production starts, the complete detector characterization facility will be setup at BEL in a class 100,000 clean room. The hybrid facility available at BEL will be used for making modules.

procurement readiness review : detector fabrication, qualification & assembly at india

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