ASTM F615M-95(2008)
(Practice)Standard Practice for Determining Safe Current Pulse-Operating Regions for Metallization on Semiconductor Components (Metric)
Standard Practice for Determining Safe Current Pulse-Operating Regions for Metallization on Semiconductor Components (Metric)
SIGNIFICANCE AND USE
Solid-state electronic devices subjected to stresses from excessive current pulses sometimes fail because a portion of the metallization fuses or vaporizes (suffers burnout). Burnout susceptibility can vary significantly from component to component on a given wafer, regardless of design. This practice provides a procedure for establishing the limits of pulse current overstress within which the metallization of a given device should survive.
This practice can be used as a destructive test in a lot-sampling program to determine the boundaries of the safe operating region having desired survival probabilities and statistical confidence levels when appropriate sample quantities and statistical analyses are used.
Note 2—The practice may be extended to infer the survivability of untested metallization adjacent to the specimen metallization on a semiconductor die or wafer if care is taken that appropriate similarities exist in the design and fabrication variables.
SCOPE
1.1 This practice covers procedures for determining operating regions that are safe from metallization burnout induced by current pulses of less than 1-s duration.
Note 1—In this practice, “metallization” refers to metallic layers on semiconductor components such as interconnect patterns on integrated circuits. The principles of the practice may, however, be extended to nearly any current-carrying path. The term “burnout” refers to either fusing or vaporization.
1.2 This practice is based on the application of unipolar rectangular current test pulses. An extrapolation technique is specified for mapping safe operating regions in the pulse-amplitude versus pulse-duration plane. A procedure is provided in Appendix X2 to relate safe operating regions established from rectangular pulse data to safe operating regions for arbitrary pulse shapes.
1.3 This practice is not intended to apply to metallization damage mechanisms other than fusing or vaporization induced by current pulses and, in particular, is not intended to apply to long-term mechanisms, such as metal migration.
1.4 This practice is not intended to determine the nature of any defect causing failure.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: F615M − 95(Reapproved 2008)
Standard Practice for
Determining Safe Current Pulse-Operating Regions for
Metallization on Semiconductor Components (Metric)
This standard is issued under the fixed designation F615M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 The d-c resistance of each specimen is measured.
1.1 This practice covers procedures for determining operat-
3.3 Each specimen is subjected to stress from rectangular
ingregionsthataresafefrommetallizationburnoutinducedby
current pulses varying in amplitude and duration according to
current pulses of less than 1-s duration.
a predetermined schedule of pulse width and amplitudes.
NOTE 1—In this practice, “metallization” refers to metallic layers on 3.4 A second d-c resistance measurement is made on each
semiconductor components such as interconnect patterns on integrated
specimen after each pulse, and it is characterized as having
circuits. The principles of the practice may, however, be extended to
failed or survived.
nearly any current-carrying path. The term “burnout” refers to either
fusing or vaporization.
3.5 The number, x, of specimens surviving and the total
number, n, of specimens tested at each pulse width and
1.2 This practice is based on the application of unipolar
amplitude are analyzed statistically to determine the burnout
rectangular current test pulses. An extrapolation technique is
level at each test pulse width for the desired burnout survival
specified for mapping safe operating regions in the pulse-
probability and confidence level.
amplitudeversuspulse-durationplane.Aprocedureisprovided
in Appendix X2 to relate safe operating regions established
3.6 A point corresponding to the burnout level (at the
from rectangular pulse data to safe operating regions for
desired probability and confidence level) is plotted for each of
arbitrary pulse shapes.
the test pulse duration values in the pulse-amplitude, pulse-
duration plane. Based on these points, an extrapolation tech-
1.3 This practice is not intended to apply to metallization
nique is used to plot the boundary of the safe operating region.
damage mechanisms other than fusing or vaporization induced
by current pulses and, in particular, is not intended to apply to
3.7 Thefollowingitemsarenotspecifiedbythepracticeand
long-term mechanisms, such as metal migration.
are subject to agreement by the parties to the test:
1.4 This practice is not intended to determine the nature of
3.7.1 The procedure by which the specimens are to be
any defect causing failure.
selected.
3.7.2 Test patterns that will be representative of adjacent
1.5 This standard does not purport to address all of the
metallization on a die or wafer (5.3).
safety concerns, if any, associated with its use. It is the
3.7.3 The schedule of pulse amplitudes and durations to be
responsibility of the user of this standard to establish appro-
applied to the test samples (9.8).
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 3.7.4 The level of probability and confidence to be used in
calculations to establish the boundary of the safe operating
2. Terminology
region (10.1).
2.1 Definitions of Terms Specific to This Standard:
3.7.5 Theamountofchangeofresistancethatwilldefinethe
2.1.1 failure—a change in the measured resistance of
criterion for failure.
610% ∆R/R or as agreed upon by the parties to the test.
3.7.6 The statistical model to be used to determine the
burnout probability at a desired stress level.
3. Summary of Practice
3.7.7 The form and content of the report.
3.1 Specimensareselectedfromthepopulationbeingevalu-
ated.
4. Significance and Use
4.1 Solid-state electronic devices subjected to stresses from
This practice is under the jurisdiction ofASTM Committee F01 on Electronics
and is the direct responsibility of Subcommittee F01.11 on Nuclear and Space
excessive current pulses sometimes fail because a portion of
Radiation Effects.
the metallization fuses or vaporizes (suffers burnout). Burnout
Current edition approved June 15, 2008. Published July 2008. Originally
susceptibility can vary significantly from component to com-
approved in 1995. Last previous edition approved in 2002 as F615M-95(2002).
DOI: 10.1520/F0615M-95R08. ponent on a given wafer, regardless of design. This practice
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F615M − 95 (2008)
providesaprocedureforestablishingthelimitsofpulsecurrent 6.1.1 Risetimeandfalltimelessthan10%ofthepulsewidth
overstress within which the metallization of a given device (full width at half maximum amplitude (FWHM)),
should survive. 6.1.2 Impedance high enough with respect to the specimen
metallization so that the pulse amplitude remains constant to
4.2 This practice can be used as a destructive test in a
within 65% between the end of the rise and beginning of the
lot-sampling program to determine the boundaries of the safe
fall,
operating region having desired survival probabilities and
6.1.3 Jitterinthepulseamplitudeandwidthlessthan65%,
statisticalconfidencelevelswhenappropriatesamplequantities
6.1.4 Current amplitude and pulsewidth capability to pro-
and statistical analyses are used.
vide pulses as agreed upon by the parties to the test, and
NOTE 2—The practice may be extended to infer the survivability of
6.1.5 Single-pulse capability.
untested metallization adjacent to the specimen metallization on a
semiconductor die or wafer if care is taken that appropriate similarities NOTE 6—Refer to Appendix X2 for information relating a rectangular
exist in the design and fabrication variables. pulse to an arbitrary pulse structure.
6.2 Pulse-Monitoring Equipment , as follows:
5. Interferences
6.2.1 Voltage-Monitoring Kelvin Probe , for use in the
5.1 The level at which failure of metallization subjected to
circuit of Fig. 1, with risetime less than or equal to 5% of the
pulsed-current overstress occurs may be dependent on the
pulsewidth of the shortest pulse to be applied, and shunt
temperature experienced by the semiconductor device. If
capacitance sufficiently low so that the pulse shape is not
significant differences in ambient temperature or heat sinking,
distorted more than specified in 6.1:
orboth,existbetweenonetestsituationandanother,theresults
6.2.2 Voltage-Monitoring Resistor (R, Fig. 1), with suffi-
may not be representative.
ciently low inductance, resistance, and shunt capacitance so
that the generated pulse is not distorted more than specified in
NOTE 3—See Appendix X1 for a discussion of factors related to
metallization heat sinking. 6.1 and the value of the resistance is known within 61%.
6.2.3 Current Probe, for use in the circuit of Fig. 2, with
5.2 Ifprobesareusedtocontactthemetallizationspecimen,
risetime less than or equal to 5% of the pulsewidth of the
suitable precautions must be taken or the results may be
shortest pulse to be applied, with an ampere-second product
misleading. The probes must not be allowed to come into
sufficient to ensure nonsaturation for the amplitudes and
contact with the area of metallization being characterized.
durations of the pulses to be used and accurate within 65%.
5.2.1 The use of Kelvin probe connections to make the
resistance measurements is usually required to prevent contact
6.3 Pulse-Recording Equipment, transient digitizer, oscillo-
resistance (at the current injection point) from interfering with
scope with camera, storage oscilloscope, or other pulse record-
the measurement.
ing means having a risetime less than 5% of the width of the
5.2.2 Probe contacts with excessive contact resistance may
shortesttestpulseusedandcapableofrecordingindividualtest
cause damage at the point of contact. Such damage can
pulses.
interfere with the measurement.
6.4 Test Fixture,providingmeansforthecurrentpulsetobe
5.3 If the test is used to infer the survivability of metalliza-
transmitted through the metallization specimen as well as
tion on a wafer or die, the results could be misleading unless
through an equivalent resistance (see 9.5) without distortion of
such factors as the following are identical: (1) metallization
the pulse shape beyond that specified in 6.1. The test fixture
design geometry, (2) oxide step geometry, and (3) orientation
must also provide a means for connecting the metallization
of the metallization paths and oxide steps to the metallization
specimentotheresistance-measuringequipment(see6.5).The
source during deposition.
test fixture will contact the specimen through either standard
component package leads or wafer probes. More than one test
NOTE 4—The design and fabrication factors listed in 5.3 have been
fixture may be used.
shown to be important for systems of aluminum metallization deposited
on SiO /Si substrates.They are given as examples and are not intended to
6.5 Resistance-Measuring Equipment—A curve tracer,
be all inclusive or necessarily to apply to all metallization systems to
ohmmeter, or other means to be used for evaluating the d-c
which this practice may be applied.
resistance and continuity of the current path on the specimen.
NOTE 5—Variations in oxide step geometry must be expected (see
X1.4.2).
The current through the specimen during this measurement
should be minimized (less than 10% of the d-c current rating
5.4 A step-stress pulsing schedule is not recommended. If
of the specimen).
such a schedule is used so that each specimen is subjected to
successive pulses of increasing amplitude until failure occurs,
theresultscouldbemisleading.Itispossiblethatapulseofthe
proper level can cause melting at a defect site without causing
an open circuit; the molten metal may become redistributed so
that the defect appears cured and will lead to failure on
successive pulses.
6. Apparatus
6.1 Current-Pulse Generator—A source of rectangular cur-
FIG. 1 Pulsing Circuit Using Resistor Voltage Drop to Monitor
rent pulses capable of meeting the following requirements: Current Through Specimen
F615M − 95 (2008)
9.9 Measureandrecordthespecimenresistance(see9.3and
9.4).
9.10 Compare the value recorded in 9.9 with that recorded
in 9.4. Characterize the specimen as failed if the resistance of
the specimen
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