Fermilab PMG Meeting

1
Response to Committee Comments on Outer Layer
Sensor Review
DØ Inner Layer Sensor Production Readiness
Review August 08, 2003 M. Demarteau, G.
Ginther
2
Sensor Specifications

• sensor specifications were well designed and
  sufficient however, several issues arose which
  need to be clarified in discussions with
  Hamamatsu Photonics (HPK) Recommendation Make
  revisions to the specifications as appropriate
  based on the following points
• The specification for the detector full depletion
  voltage is Vdep lt 300 V. The absence of a lower
  limit could lead to large, undesirable mismatches
  between detectors in the tracker. A lower limit
  of Vdep gt 40 V seems appropriate, but should be
  discussed with HPK to ensure no impact on cost.
• The recommendation to specify a lower limit for
  the detector full depletion voltage of 40 V has
  been adopted and the specifications have been
  adjusted accordingly.
• Comment from Hamamatsu 1) specificationsa) The
  change about 40V lt Vdep lt 300V is not a problem
  for us.

3
Sensor Specifications

• The specification of wafer warp less than 25 mm
  is too stringent, and in practice it may be too
  difficult to achieve. This specification was not
  met for the prototype sensors. DØ should
  understand what the real specification should be.
  The final sensor warp might be less once the
  sensor is glued down. This should be investigated
  and quantified.
• The specification of wafer warp has always been
  on a best effort basis with Hamamatsu. For the
  Layer 1 sensors Hamamatsu has shown that it can
  achieve wafer warps that are within our 25 mm
  window. Our prototype modules show that we can
  tolerate wafer warps of 50 mm. We communicated
  our warp requirements to HPK We have relaxed
  the sensor warp to 100 mm, that is that the
  sensor has to fit within two parallel planes 100
  mm apart. We would like to view this as an upper
  limit if a sensor has a larger warp we reserve
  the right to reject the sensor. We continue to
  work with Hamamatsu on a best effort basis for
  wafer warp, to emphasize that wafer warp is a
  critical parameter for us.
• Comment from Hamamatsuc) The chip warp should be
  within 100 mm max. on the prototypes. Do you have
  the measured data on it ? If so, provide the
  same with us, please.

4
Sensor Specifications

• Stave height along the length of the stave
  Note, current tooling for stave assembly not
  very flat.

75 mm
5
Sensor Specifications

• HPK will not do whole-wafer visual inspections
  for open-circuits or short-circuits, so this part
  of the specification should probably be deleted.
• The experience with Hamamatsu is indeed that they
  are confident enough in the quality of their
  product that they deem whole-wafer visual
  inspections for open-circuits or short-circuits
  at the company redundant. Given that Hamamatsu
  has accepted this requirement we consider it
  prudent to leave it as part of our
  specifications. Recent quality assurance
  measurements of the CMS collaboration reinforce
  our notion that quality assurance at the vendor
  should be emphasized.

6
Sensor Specifications

• The mask alignment specification (2.5 mm) is not
  stringent enough. Mask alignment of 0.5 mm
  should be achieved in order to ensure proper
  metal-implant overlap.
• Our response to committee The recommendation to
  make the mask alignment specification of 2.5 mm
  more stringent was adopted. The prototype sensors
  show that Hamamatsu is able to achieve a mask
  alignment to better than 0.5 mm, and that is our
  new specification.
• Response from Hamamatsu mask alignment
  tolerance of /-0.5um is very tough for us. Could
  you kindly accept the /-2um tolerance although
  the most pcs should be covered by about /-1um
  tolerance ?
• We accepted their proposal. We now also receive
  test structures with alignment marks on them.

7
Sensor Specifications

• The average coupling capacitance was 105 pF,
  about 12 pF below the minimum specification. The
  measurement should be checked - the reason why
  the specification was not met should be
  identified and corrected, or the specification
  should be revised.
• The coupling capacitance measurements shown at
  the review were taken at 10kHz. The full
  frequency dependence of the coupling capacitance
  was measured and a low frequency limit of 140 pF
  was obtained, which is well within our
  specifications. (more results today)

8
Sensor Testing and QA

• Our testing seemed to indicate more bad channels
  than identified by HPK. Recommendation Discuss
  the discrepancies as soon as possible with HPK to
  understand the cause for each discrepancy. This
  will ensure the integrity of the HPK
  measurements, which are relied upon for
  identifying bad strips for the majority of
  sensors.
• Those sensors that showed many more defects in
  our own QA tests than at Hamamatsu were
  re-measured at Fermilab. It was found that some
  of the flaws previously identified were a result
  of a bad contact between the probe and the
  sensor.
• After the review, the QA program at the testing
  centers was reviewed and some significant
  shortcomings in the setup were identified and
  rectified. Results on site qualification and
  comparison will be shown today
• Only two sensors showed defects that were not
  identified at Hamamatsu. Those results have been
  communicated to the vendor.
• HPK response 29) We are afraid they are
  scratches made after our pre-shipping test.5)
  Regarding increase of pinhole at your test from
  ours, complete elimination is unlikely in
  consideration of an insulation layer's life. In
  fact, higher voltage than 80V (say 100 to 120V)
  is applied on our inspection, which should be
  useful for a screening purpose. Incrase of
  pinhole of a few channels may not be avoided.

9
Irradiation

• Recommendation The KSU facilitys dosimetry
  needs to be fully understood and sensors should
  be irradiated at alternative facilities with
  well-understood dosimetry The post-irradiation
  measurements need to be re-examined and fully
  understood.
• Tim Boltons talk will address the dosimetry. For
  the previous PRR the area of an L1 sensor was
  mistakenly used in the normalization of the flux
  (see Boltons talk). We have not performed a
  cross-check of the results at alternate
  facilities, but rather have performed a cross
  check of copper foil activation measurements at
  Fermilab
• Updated results for outer layer sensors made
  available for this PRR
• Results from irradiation of Layer 1 sensors to be
  presented today, with new dosimetry calibration.

10
QA

• Recommendation Identify a physicist who is
  experienced with sensor device testing and
  properties to be responsible for the overall
  testing and QA program. This physicist should
  spend a significant fraction of his/her time on
  sensor QA, full-time if needed. Consistency of
  measurements between the different facilities
  should be ensured by selecting a subsample of
  detectors and comparing the results of the same
  QA tests performed at each facility.
• Mme. Mao and Ralf Bernhard will be full time
  dedicated physicists to the overall sensor
  testing and QA. More details in QA talk.
  Consistency of measurements between various
  facilities has been addressed (see McCarthys
  talk).

11
SVX4 Noise Performance

• Recommendation Perform refined SVX4 noise
  studies with prototype modules using 396 ns
  crossing time electronics to understand issues
  like setup noise and post-irradiation shot noise.
  We recommend DØ get together with CDF to
  understand the SVX4 noise behavior.
• After the review the noise measurements were
  revisited and results communicated to CDF. We
  continue to perform noise measurements with
  modules and irradiated modules exploring the full
  parameter space.

12
Database

• Recommendation DØ should investigate if the
  database selected will serve the upgrade project
  smoothly through the entire project cycle. We
  recommend that this be done together with CDF and
  that databases of ongoing projects (CMS, ATLAS,
  GLAST) be investigated if the present choice is
  found deficient.
• Response Old database relied on student in
  computing department at UIC. Concerns about long
  term stability, support and flexibility motivated
  us to adopt the ATLAS database design with full
  support from the Dzero online group. Please see
  todays QA presentation

13
Hamamatsu Delivery Schedule

• Recommendation Obtain a firm commitment of the
  delivery schedule from HPK to clarify the
  delivery rate for each month of the project
  duration.

Dzero Schedule
CDF Schedule