ATLAS Detector Qualification Tests
Tests listed in this document are Cambridge proposals and have
not yet been formally approved by ATLAS.
In order to qualify as a candidate for ATLAS production orders,
detectors from each designated manufacturer must be demonstrated to
satisfy the ATLAS
specifications on delivery, as well as after irradiation to
3x10**14 p.cm-2 as part of the 1998
ATLAS irradiation program.
Several new designs from different manufacturers are becoming
available this summer, and before inclusion in the irradiation
program they should first be checked to ensure that detector and
test-structure electrical properties are consistent with
required ATLAS specifications. These checks should include the following:
- Interstrip capacitance (strip metal to neigbours) should be
measured at 150V bias. The measurement requires at least
a 5-point contact (strip to nearest two neighbours either side). ATLAS
specs require C < 1.2pF/cm.
- Coupling capacitance measured from either the
detector or test-structure. Specs require C > 20pF/cm.
- Interstrip resistance at 150V bias (strip implant to a nearest
neighbour). Specs require interstrip resistance >> biassing
resistance, ie measured R ~ 2 x Rpoly.
- Depletion from either detector or diode CV measurements.
ATLAS specs require Vdep < 150V.
- Series resistance of strip metal, from either the detector or
from the test-structure. Specs require R < 15ohms/cm.
- Resistance of poly biassing from either the detector or from
the test-structures (easiest to do this with the test-structure).
Specs require R= 1.5+/-0.5 Mohm.
- Sheet resistance of n- and p-implants from test-structures or
the detector if possible. Specs require < 400ohm/sq.
- Flat band voltage from CV MOS (no spec reqiurement, but useful
for processing consistency check)
For detector designs satisfying the above criteria, proposed pre- and
post-irradiation tests are listed below:
Tests on every detector before irradiation
- Delivery inspection. Visual check with the detector placed on
the probestation chuck.
- IV characteristic measured up to 350V. This measurement
requires the detector to be placed on the chuck of a
probestation and the IV characteristic measured using a
computer controlled current meter and voltage source.
Detectors should be rejected if
current exceeds 6uA at 150V or 20uA at 350V.
- CV at 1kHz to check detector depletion.
Tests on a detector batch subset before irradiation
These are a verification of the manufacturer's own data.
- All 768 strips will be probed to quantify strip losses due to
metal shorts/opens and oxide pinholes. The detector is
placed on the chuck of an automatic probestation, and each
strip metal is probed under computer control. Continuity
across the strip oxide is determined by a measure of current
between the strip metal and backplane at 100V bias; opens
and shorts between strip metals are determined by measuring
capacitance between strip metal and backplane. An example of
the scheme currently in use at Cambridge is illustrated
here. This test requires a
computer controlled probestation, voltage source, current
meter and LCR meter, and takes about 1.25 hours.
Specs require >98% good strips.
- Detector current at 150V should be monitored over 24 hours
in an inert (nitrogen) atmosphere. Several detectors may be
measured in parallel by use of a switching matrix, though
this will probably require the detectors to be mounted into
Detectors with current
increasing by more than 2uA in 24hours do not satisfy the
ATLAS spec and the remainder of the detector batch will also require testing.
Pre-Irradiation detector preparations
Before irradiation the detectors should be glued (or clamped?)
support cards and bonded to
pitch adaptors for compatibility with readout with both binary
and analogue chips. The glue type should be araldite 2011.
The IV test described in the previous section should be
to check the effects of the glue.
It would also be to great advantage if the detector can be bonded
to readout chips for an analysis of the strip noise distribution,
as this is helpful in the interpretation of post-irradiation
Post-irradiation detector tests
Detectors will be irradiated at the CERN PS to
~3x10**14p.cm-2 with 24GeV/c protons.
After irradiation the detectors should be annealed for ~7 days
at 25degC equivalent temperature in order to reach the minimum
of the depletion anneal. The following tests should
then be performed after the anneal (most post-irradiation
measurements need to be performed at -10degC or cooler to limit
- IV (require <1mA at 350V at -10degC)
- CV at 100Hz for estimate of depletion volts (require plateau
at < 350V).
- IV stability over 24 hours at 350V.
- Oxide punch-throughs measured by automatic probestation. This
test will require the detector to be warmed to room
temperature. A simple continuity test across the strip
oxides requires only a few volts, and the pitch adaptors can
be probed instead of the detector for conveniance.
- Detectors will be bonded to readout chips for an
analysis of strip noise distributions across the full
detector width. Bad strips should
be quantified. We require the pre-irradiation condition
of >98% good strips (taking into account both oxide
punchthroughs as well as noisy strips) to be maintained.
- A sample of irradiated detectors to be bonded to analogue
chips to determine the onset of the plateau in charge
collection efficiency, for use as a cross check on the CV depletion measurement
- Multi-function test-structures evaluated (**NB none yet have
been irradiated, so this is only relevent to future irradiations).
The following is considered to be the minimal list of equipment
required for the
unirradiated detector tests listed in this proposal
Additional equipment required for irradiated detector testing:
- Automatic (computer controlled) probestation, eg Wentworth
AWP-1050, Summit 10K, Alessi 6100 etc
- Voltage source up to 500V or more, both polarities, eg
Keithley 487, Keithley 6517 etc
- Picoammeter, sensitive from <1nA to >=2mA, eg Keithley 487,
Keithley 6517 etc
- LCR meter, from 100Hz to 1kHz or higher, eg Wayne Kerr 6425,
HP 4263B etc
- Switching matrix 2 x n where n=10 or more, eg Pickering
20-360, Keithley etc, for IV stability tests of several detectors
- Bonding machine, manual or automatic.
- Networked PC with GPIB card and appropriate control
software (eg LabView)
- Binary chip hybrids with re-bondable support frame (eg ABCD or LBIC/CDP)
- Analogue chip hybrid(s) with re-bondable support frame (eg
SCT128 or FELIX)
- Ru-106 beta source (activity 185kBq/5uC is ideal) for triggering
- Trigger counters (Hamamatsu model H5783 is ideal)
- PC or workstation equiped with appropriate control and
monitoring software for irradiation module readout
back to main Cambridge Silicon Web Page
back to the ATLAS Irradiation Web Page.
Last modified: Mon Dec 14 11:36:43 MET