1. CMS Tracker Electronics
APV25 wafer testing status
s1 wafers received so far
previous 10 wafers (engineering run – Sept. 2000)
all cut now, ~1300 remaining KGD available presently at IC
2 production wafer lots delivered January: = 45 out of 48 ordered
shortfall of 3 in 2nd lot (rejected by manufacturer QA)
processing problems identified (low yield) – both lots to be replaced
3rd full lot launched to provide remaining 3 (25 wafers/lot)
3 wafers delivered mid Feb.
remaining 22 requested and delivered early March
high yield restored, 13 wafers currently being diced
Mark Raymond
April, 2002
CMS Tracker Electronics

2. CMS Tracker Electronics
Problems with 1st two lots
1st lot (13 of 24 wafers tested) – low yield (17 – 36 %)
some good chips around periphery
circular area of good chips in centre
failure modes: ~ even split between digital
and channel (pedestals or gain) failures
2nd lot (12 of 21 wafers tested) – lower yield (1 – 21%)
similar circular geometry but no good chips in centre
central chips with v. high currents
IBM notified (formal procedure handled through CERN (F.Faccio)
– regular telephone conference)
investigation launched
early acknowledgement of likely process problem
example wafers returned and investigated
problem traced to localised absences of silicide layer
(contact layer to gates and source/drain implants)
3 more wafer lots launched (mid March) to provide replacements with extra checking at critical process steps
grey = bad
white = good
April, 2002
CMS Tracker Electronics

3. Results from 3rd wafer lot (25 wafers)
average yield 79%
some wafers v. high yield
others good but
still show pattern
36 chips in incomplete reticles
now excluded from yield
calculation
(previously not the case)
94%
73%
April, 2002
CMS Tracker Electronics

4. CMS Tracker Electronics
Incomplete reticles
any reticle within ~ 3mm
of wafer edge not completely
processed (via layers omitted)
penalty for us due to chip
grouping (4 APVs/reticle)
April, 2002
CMS Tracker Electronics

5. CMS Tracker Electronics
present chip availability
1300 now - remaining chips from engineering run
3800 soon - 13 wafers (from 3rd lot) currently being diced
5100
KGD on remaining uncut 3rd lot wafers
8400 currently in-hand
3 wafer lots currently in production (first due end April)
already passed silicide steps with no problem observed
all 3 lots should yield further ~ 20,000 KGD
April, 2002
CMS Tracker Electronics

6. CMS Tracker Electronics
Summary
Process problems with first two production lots
investigation still under way but these lots will be replaced
communication channel (via CERN) to manufacturer effective
manufacturer’s response very constructive and helpful throughout
3rd lot yield back at expected high level (average 79%)
1st replacement lot due end April
probe test time/chip now ~ 1min, can handle 2 wafers/day on single station
April, 2002
CMS Tracker Electronics