recipe for strips to leave unbonded

Tracker Week, CERN, 20-24 Oct 2003

21 Oct 2003Tracker Week - Bonding WGSalvatore Costa - Catania

Which strips should the Bonders skip

because of known Sensor defects

(a question from Bonding WG to Sensor experts)

21 Oct 2003Tracker Week - Bonding WG 2 Salvatore Costa - Catania

Recipe for strips to leave unbonded

• React only to bond immediately upstream of sensor with bad strip

• Skip (= leave unbonded)– All bad IDIEL (considered pinholes)

(IDIEL_1_SEN_.POSITION_OF_BAD_STRIPS)

– All Isolated bad CAC (believed to have high chance to develop into pinholes with irradiation) (CAC100HZ_1_ SEN_.POSITION_OF_BAD_STRIPS)

– All but lowest in a bad CAC chain (believed to represent shorts) (CAC100HZ_1_ SEN_.POSITION_OF_BAD_STRIPS)

CAC Example: 3 34 35 36 37 skip isolated 3, skip all but lowest in 34-37 chain, or: bond only 34


Isolated bad-CAC strips

Recently questioned, because:• They should fail the Pinhole search with Karlsruhe’s LED

system • But some Italian Labs and UCSB have bonded them

anyways in this initial Module Prod for investigation purposes and found no evidence of pinholes:

• >>>>>>>>>>>> LED test NEVER failed <<<<<<<<<<<<We wanted to learn more on bad I_DIEL & bad C_AC strips I’ve performed a comprehensive study of the bad

strips…and… as a result of this study, we are no longer confident on

any part of our current rule to skip bad strips So we are turning to Sensor experts for guidance!


Bad strips study

• In DB there are relevant data, in Tables IDIEL & CAC100HZ, for 2427 Sensors

• For 7 Sensors, data are nonsense 2420 Sensors are included in this study• For each of 2420 sensors, download from DB:

1) I_DIEL value (in nA) for all strips

2) List of bad strips for I_DIEL

3) C_AC value (in pF) for all strips

4) List of bad strips for C_AC


Bad strips study

Accounting: out of 2420 Sensors…1. Bad-I_DIEL strips are 2898 in total (~1.2 per Sensor in average)2. Bad-C_AC strips are 10251 in total (~4 per Sensor in average)

1. Of these, 3707 are ‘isolated’, 6544 are ‘chain’ (‘shorted’)2. Out of the 3707 isolated bad-C_AC strips:

1. 1146 (30%) are also flagged as bad-I_IDIEL2. 2561 (70%) are not flagged as bad-I_IDIEL

Plot Distributions of:1. I_DIEL for good-I_DIEL strips (expect ~0)2. I_DIEL for bad-I_DIEL strips (expect >0, but… )3. ‘relative’ C_AC for isolated bad-C_AC strips (expect small values, <1)3. ‘relative’ C_AC for chain bad-C_AC strips (expect integer multiples, 2, 3,…, but… )4. IDIEL for isolated bad-C_AC strips which are also in bad-I_DIEL list5. IDIEL for isolated bad-C_AC strips which are not in bad-I_DIEL list


I_DIEL for good strips (1)

• Plotted for 869,158 strips

(approx 1700 Sensors)• Extends to ~1A

but peaks near 0 as expected




(approx 1700 Sensors)• 857,754 (99 %) are within

1 nA




(approx 1700 Sensors• 742,388 (85 %) are within

0.1 nA• ~560,000 (65%) have

I_DIEL=0.00• There are a few negative

values


I_DIEL for bad-IDIEL strips (1)

• 2400 Sensors• 2898 bad-

IDIEL strips• (~1.2/Sensor)• Extends to

1.2x107, but most are much lower



• 2400 Sensors• 2898 bad-IDIEL

strips• (~1.2/Sensor)• 0<I_DIEL<1.2x107nA• 1576 (54%)

1A<I_DIEL≤1mA



• 2400 Sensors• 2898 bad-IDIEL strips• (~1.2/Sensor)• 0<I_DIEL<1.2x107nA• 1576 (54%)

1A<I_DIEL≤1mA• 797 ( 27%)

0.1nA<I_DIEL≤1A• A peak at ~100 nA

?



• 2400 Sensors• 2898 bad-IDIEL strips• (~1.2/Sensor)• 0<I_DIEL<1.2x107nA

– 1576 (54%)

1A<I_DIEL≤1mA– 797 ( 27%)

0.1nA<I_DIEL≤1A

• 476 (16%) have ‘normal’

(=as 85% of good strips) I_DIEL < 0.1nA !!!

Bond or not?


Relative C_AC for Isolated bad-CAC strips (1)

• 2400 Sensors• 10251 bad-C_AC strips• (~4/Sensor)• 3707 Isolated• (~1.5/Sensor)• Extends from

-10000< <2000

but most are much lower

C_AC

<C_AC>


Relative C_AC for Isolated bad-CAC strips (2)

• 2400 Sensors• 3707 Isolated bad C_AC

strips• (~1.5/Sensor)

-10000< <2000

• 3566 (96%)

-2 < < 2

• Some negative values• Peaks at ~0 and ~0.6

Bond or not?

C_AC

<C_AC>

C_AC

<C_AC>


I_DIEL for Isolated bad-CAC strips (1)


strips• (~1.5/Sensor)• 1148 (30%) also in bad

I_DIEL list• I_DIEL Distributions are

similar to the whole bad-I_DIEL ones in all scale ranges (as expected)




strips• (~1.5/Sensor)• 1148 (30%) also in bad


similar to the whole bad-I_DIEL ones in all scale ranges (as expected)

Picked in bad IDIEL list



• 2400 Sensors• 3707 Isolated bad-

C_AC strips• (~1.5/Sensor)• 2561 (70%) not in bad


similar to the whole good-I_DIEL ones in all scale ranges


• Out of the 2561 not in bad I_DIEL list:

• 2556 (~100%)

0 < I_DIEL < 1nA• 2358 (92%) have ‘normal’

0 < I_DIEL < 0.1nA• Only 193 (8%) have

0.1nA < I_DIEL < 1nA

(not shown)

Bond or not?



Relative C_AC for Chain bad-CAC strips (1)

• 2400 Sensors• 10251 bad-C_AC strips• (~4/Sensor)• 6544 Chain• (~2.7/Sensor)• Extends from

-200< <1000

but most are much lower

C_AC

<C_AC>




strips• (~2.7/Sensor)• -200< <1000

• 6508 (99%) -2 < < 8

• Expected integers (2,3,4…) Some do, but most have <1 with distrib ~ Isolated:

Our rule that assumed them to be all shorts might be too naïve!

C_AC

<C_AC>

C_AC

<C_AC>



• 2400 Sensors• 6544 Isolated bad C_AC strips• (~2.7/Sensor)• -200< <1000

5889 (90%)

-2 < < 2

Neighbors, but ‘isolated’? 619 (10%)

2< <8

There is a peak at 2.5 Actually shorted?

C_AC

<C_AC>

C_AC

<C_AC>

C_AC

<C_AC>


Summary & Request for guidance

1. Strips in bad-IDIEL list: 16 % do not seem to have a bad I_DIEL: bond or skip?2. Isolated strips in bad-CAC list:

– They all seem to have bad C_AC (‘relative’ C_AC mostly <1)– 30 % are also in bad-IDIEL list– 70 % are not in bad-IDIEL list – 92% of those not in bad-IDIEL list have indeed good I_DIEL, 8% slightly

high I_DIEL, almost none outrageously high I_DIEL– Those tested with LED pinhole search, all pass it

We wonder if we should bond these3. Chain strips in bad-CAC list:

– Only 10% of these seem to actually be shorted (‘relative’ C_AC >1)– Most (90%) behave just like the isolated ones

We wonder if we should bond or skip these or treat them in a more sophisticated way, such as: compute relative C_AC, then If <some threshold (1?), treat them the same way as the isolated If > , apply the current rule for shorts i.e. bond only the 1st in chain

In all cases we ask Sensor experts for guidanceIf adopted, new v.3.2 of DB I/F needed to implement new rules

recipe for strips to leave unbonded

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