ASTM F617-00

Standard Test Method for Measuring MOSFET Linear Threshold Voltage (Withdrawn 2006)

SCOPE
1.1 This test method covers the measurement of MOSFET (see Note 1) linear threshold voltage under very low sweep rate or d-c conditions. It is a d-c conductance method applicable in the linear region of MOSFET operation where a drain voltage V D of approximately 0.1 V is typical.
Note 1--MOS is an acronym for metal-oxide semiconductor; FET is an acronym for field-effect transistor.
1.2 This test method is applicable to both enhancement-mode and depletion-mode MOSFETs, and for both silicon-on-insulator (SOI) and bulk-silicon MOSFETs. The test method specifies positive voltage and current conventions specifically applicable to n-channel MOSFETs. The substitution of negative voltage and negative current make the test method directly applicable to p-channel MOSFETs.
1.3 The values stated in International System of Units (SI) are to be regarded as standard. No other units of measurement are included in this test method.
1.4 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.
WITHDRAWN RATIONALE
This test method covers the measurement of MOSFET (see Note 1) linear threshold voltage under very low sweep rate or d-c conditions. It is a d-c conductance method applicable in the linear region of MOSFET operation where a drain voltage VD of approximately 0.1 V is typical.
Note 1-MOS is an acronym for metal-oxide semiconductor, FET is an acronym for field-effect transistor.
Formerly under the jurisdiction of Committee F01 on Electronics, this test method was withdrawn in June 2006 in accordance with section 10.6.3.1 of the  Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.

General Information

• Status: Withdrawn
• Publication Date: 09-Jun-2000
• Withdrawal Date: 12-Jul-2006
• ICS: 31.080.30 - Transistors
• Technical Committee: F01 - Electronics
• Drafting Committee: F01.11 - Nuclear and Space Radiation Effects

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F 617 – 00
Standard Test Method for
Measuring MOSFET Linear Threshold Voltage
This standard is issued under the fixed designation F 617; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope source voltage. A linear plot is made of the drain current as a
functionofgatevoltage.Themaximumtangenttotheresulting
1.1 This test method covers the measurement of MOSFET
curve is extrapolated to the gate-voltage axis or to the voltage
(seeNote1)linearthresholdvoltageunderverylowsweeprate
independent line representing the drain-leakage current. This
or d-c conditions. It is a d-c conductance method applicable in
intercept is the threshold voltage for the drain-source voltage
the linear region of MOSFET operation where a drain voltage
and temperature conditions of the test.
V of approximately 0.1 V is typical.
D
3.2 Before this test method can be implemented, test con-
NOTE 1—MOS is an acronym for metal-oxide semiconductor; FET is
ditions appropriate for the MOSFET to be measured must be
an acronym for field-effect transistor.
selected and agreed upon by the parties to the test. Conditions
1.2 This test method is applicable to both enhancement-
will vary from one MOSFET type to another, and are deter-
mode and depletion-mode MOSFETs, and for both silicon-on-
mined in part by the intended application.The following items
insulator (SOI) and bulk-silicon MOSFETs. The test method
are not specified by this test method, and shall be agreed upon
specifies positive voltage and current conventions specifically
between the parties to the test:
applicable to n-channel MOSFETs. The substitution of nega-
3.2.1 Reference temperature to which the measured thresh-
tivevoltageandnegativecurrentmakethetestmethoddirectly
old voltages shall be normalized.
applicable to p-channel MOSFETs.
3.2.2 Permissible range of ambient temperature within
1.3 The values stated in International System of Units (SI)
which the measurement is to be conducted. The reference
are to be regarded as standard. No other units of measurement
temperature shall be within this range.
are included in this test method.
NOTE 2—Thetemperaturesensitivityofthethresholdvoltagemaybeas
1.4 This standard does not purport to address all of the
largeas−5mV/°C,ormore.Thereproducibilityofthemeasurementswill
safety concerns, if any, associated with its use. It is the
be degraded accordingly, unless the values of the threshold voltage are
responsibility of the user of this standard to establish appro-
normalized to a common reference temperature. To reduce the effect that
priate safety and health practices and determine the applica- uncertaintiesinthetemperaturesensitivityofthetestdeviceswillhaveon
the reproducibility, no more than an appropriately small range of test
bility of regulatory limitations prior to use.
temperatures should be allowed.
2. Terminology
3.2.3 Drain voltage V at which the measurement is to be
D
2.1 Definitions of Terms Specific to This Standard:
made.
2.1.1 drain-leakage current—of a MOSFET, the d-c current
3.2.4 Maximumdraincurrent, I ,maximumgatevoltage,
DM
from the drain terminal when the gate voltage with respect to
V ,andgatevoltagesteps, DV ,overwhichthemeasurement
GM G
the threshold voltage is such that the MOSFET is in the OFF
istobemade.Valuesfor I , V ,and D V shallbeselected
DM GM G
state.
to permit taking enough data points to define adequately the
2.1.2 threshold voltage—of a MOSFET,foroperationinthe
drain-current, gate-voltage characteristic curve in the region of
linear region, the gate-to-source voltage at which the drain
the inflection point, namely, where the tangent to the curve has
current is reduced to the leakage current.
the largest slope (maximum tangent). The value selected for
DV shall be one of the following: 0.02, 0.05, 0.10, 0.20, or
G
3. Summary of Test Method
0.50 V. The recommended procedure for selecting values for
3.1 The drain-source current of the MOSFET under test is
I , V , and DV is provided in the Appendix.
DM GM G
measured at several values of gate voltage for a fixed drain-
4. Significance and Use
4.1 The threshold voltage is a basic MOSFET parameter
This test method is under the jurisdiction of ASTM Committee F01 on
Electronics and is the direct responsibility of Subcommittee F01.11 on Quality and that must be determined for the design and application of
Hardness Assurance.
discrete MOSFETs and MOS (see Note 1) integrated circuits.
Current edition approved June 10, 2000. Published October 2000. Originally
Threshold voltage is utilized in circuit design to specify the
published as F617–79. Last previous edition F617M–95.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 617–00
turn-on voltage of MOSFETs, and thereby determine perfor- 5.6 Thereproducibilityofthetestmethodisdegradedbythe
mance attributes such as speed, power, noise margin, etc., of uncertainty and variation of the MOSFET temperature during
digital and analog circuitry. the test and by the temperature sensitivity of the threshold
voltage (see Note 2).
4.2 The threshold voltage change in MOSFET devices,
which will be exposed to ionizing radiation is a key factor in 5.6.1 It is expected that the power dissipation of the
MOSFET during the measurement of the linear threshold
the selection of devices to be utilized in such an environment.
voltage will be so low that a negligible increase in device
Radiation induced charges trapped in the gate insulator and in
temperature will occur. This is the reason that the temperature
the insulator-semiconductor interface regions of the MOSFET
of the package ambient is to be measured rather than the
cause changes in the threshold voltage of the device and,
temperature of the MOSFET.
hence,thedeviceperformance.Thismustbeconsideredduring
design and MOSFET selection. 5.6.2 Before the measurement is begun it is important that
the device will have reached its equilibrium temperature after
5. Interferences transfer and handling, for example, and that the temperature
indicator is adjacent to the MOSFET.
5.1 If the gate current is greater than1%ofthe drain
5.6.3 The range of the package-ambient temperature (see
current, the threshold voltage measurement results are not
8.18) is a measure of the uncertainty and variation of the
valid.
MOSFET temperature during the test.
5.2 If the current through voltmeter V (see Fig. 1) is large
5.7 This test method is valid only if the MOSFET stability
enough to alter the threshold voltage, either a meter with a
is sufficient to prevent changes in threshold voltage due to
higher impedance must be used (see 6.2.2) or the drain-current
bias-temperature stress applied during the threshold voltage
reading must be reduced by the amount of the meter current.
measurement.
5.3 The high (positive) input of the ammeter, A, (see Fig. 1)
5.8 MOSFET threshold voltage measurements should be
must always be connected to the drain side of the MOSFET,
made under dark conditions when the MOSFET package
regardless of the polarity of the device. Note that with such a
admits enough light to increase the apparent leakage current.
connection,theammeterwillgivenegativecurrentreadingsfor
5.9 Caremustbetakenthatthemanufacturer’sspecification
n-channelMOSFETs.Thereasonforconnectingthehighinput
limits on the MOSFET are not exceeded, even for very brief
to the drain side of the MOSFET is to reduce errors in the
periods,orthecharacteristicsoftheMOSFETmaybechanged.
measurement of drain current due to meter-leakage currents.
Electronic ammeters are designed for low internal-leakage
6. Apparatus
operation only when the high input is connected to the
low-leakage, high-resistance side of the current path. 6.1 Transistor Test Fixture, to connect the MOSFET under
test to the test circuit. Electrical contacts shall be clean and of
5.4 Care must be taken to prevent electrical voltage over-
good quality.
stress damage to the gate dielectric as a result of device
6.2 Voltmeters:
handling during the threshold voltage measurement. Under
certain conditions, electrostatic discharge from the human
6.2.1 V , with an input impedance of approximately 10 MV
body can result in permanent damage to the gate insulator.
or greater, and a capability of measuring a voltage as large as
V (see 3.2.4) to within 60.5 mV.
5.5 Valid threshold voltage measurement data will be ob-
GM
tainedonlyifthemagnitudeofthedrainvoltageappliedduring 6.2.2 V , with an input impedance of approximately 10 MV
the threshold voltage measurement is less than the drain- or greater (see 5.2) and a capability of measuring a voltage as
substrate junction-breakdown voltage. large as V (see 3.2.3) to within 61%.
D
FIG. 1 Test Circuit for n -Channel Enhancement-Mode MOSFETs (see 1.2 and 5.3)
F 617–00
6.3 Ammeter, A, capable of measuring I (see 3.2.4) with a 8.12 Record the current indicated by ammeter A and call it
DM
minimum accuracy of 60.5 %. I . This is the drain leakage current to be used in this test
L
6.4 Voltage Sources, VS and VS , meeting the following
method.
1 2
specifications after warmup:
8.13 Adjust voltage source VS until the gate voltage is at
6.4.1 Drift less than 60.15 % of the set voltage over an 8-h
the nearest DV step below V (see 3.2.4 and X1.4).
G GL
period.
8.14 Adjust voltage source VS to change the gate voltage
6.4.2 Periodic and random deviation (noise and ripple) less
by DV in the direction of increasing drain current.
G
than 0.5% of the output voltage.
8.15 Verifythatvoltmeter V continuestoreadthespecified
6.4.3 Voltage adjustable to at least the minimum accuracy
value V and, if necessary, readjust voltage source VS to
D 2
requirements defined for meters V and V , respectively, and
1 2
obtain the specified value V .
D
6.4.4 Capableofsupplyingvoltagesandcurrentsrequiredto
8.16 Record the drain current, I , indicated by ammeter A
make the measurements of the method.
D
and the gate voltage, V , indicated by voltmeter V .
6.5 Temperature-Measuring Device, capable of measuring
G 1
the temperature of the package ambient with a precision of
8.17 Repeat8.14,8.15,and8.16untileither I or V (see
DM GM
60.2°C.
3.2.4) is reached or until it is established that enough data
pointshavebeentakentodeterminethetangentwiththelargest
7. Sampling
slope.
7.1 This test method determines the properties of a single
8.18 Measure and record the temperature of the package
specimen.Ifsamplingproceduresareusedtoselectdevicesfor
ambient.Recordtheaverageandthedifferenceofthetempera-
test, the procedures shall be agreed upon by the parties to the
ture measured here and in step 8.5; call these values the mean
test.
and the range of the package ambient temperatures, respec-
tively.
8. Procedure
8.1 Assemble the test circuit shown in Fig. 1. 9. Calculations and Interpretation
8.2 If a substrate electrode is provided on the MOSFET,
9.1 Option I—Determination of Threshold Voltage by Graph
connect the substrate to the source electrode.
Analysis:
8.3 Turn on the apparatus and allow it to warm up at least
9.1.1 Data shall be graphed so that the gate voltage, V ,is
G
for the period specified by the apparatus manufacturer before
plotted on the abscissa and the drain current, I , is plotted on
D
proceeding further.
the ordinate (Fig. 2).
8.4 Set voltage sources VS and VS to 0 V and insert the
1 2
9.1.1.1 Select the voltage scale, V (voltage/cm), in accor-
MOSFET to be tested into the test fixture. Wait until the
S
dance with the value of D V specified (see X1.4), as shown
MOSFEThasreacheditsequilibriumtemperatureinthefixture
G
below:
before proceeding further.
NOTE 3—The time for the device to reach an equilibrium temperature
after having been handled or transferred from a different temperature
environment can be a minute or more, depending on the magnitude of the
temperature change and the design of the package.
8.5 Measure and record the temperature of the package
ambient and ensure that the temperature is within the range
agreed upon between the parties to the test (see 3.2.2).
8.6 Adjust the voltage source VS until voltmeter V indi-
2 2
cates the specified voltage value V (see 3.2.3 and 1.1).
D
8.7 Adjust voltage source VS to change the gate voltage
(indicated by voltmeter V ) in the direction of increasing drain
current, I ,untilacurrentisattainedthatisapproximately1%
D
of the specified value of I (see 3.2.4).
DM
8.8 Verify that voltmeter V continues to read the specified
value V and, if necessary, readjust voltage source VS to
D 2
obtain the specified value V .
D
8.9 Record the drain current, I , indicated by ammeter, A
D
(see 6.3). Record the gate voltage, V , and call this voltage
G
V .
GL
8.10 Adjust voltage source VS , to change the gate voltage
an amount equal to 0.5 ?V 2 V ? in the direction of
GM GL
NOTE 1—Thesizeofthedatapointsinthisgraphisgrosslyexaggerated
decreasing drain current.
for the purpose of clarity.
8.11 Verifythatvoltmeter V continuestoreadthespecified
FIG. 2 Illustrative Data for an n -Channel Enhancement Device
value V and, if necessary, readjust voltage source VS to
D 2 with a Reading of 3.746 V for the Threshold Voltage
obtain the specified value V .
D
F 617–00
threshold voltage, V , for the drain voltage and temperature
DV (V) V (v/cm)
G S T
0.02 # 0.02
conditions of the test. Record the value of V on the graph of
T
0.05 # 0.05
9.1.1.
0.10 # 0.05
0.20 # 0.10 9.1.11 If the conditions stated in 9.1.10 do not hold, the
0.50 # 0.20
value for DV selected in X1.4 is too large and the method
G
must be repeated using an appropriately reduced value for
9.1.1.2 Select the current scale, I (current/cm), so that
S
DV .
G
I ·V
DM S
I ;
S
10 DV
G
NOTE 5—To ensure that the threshold voltage measurement was made
in the linear region of operation, examine the plot. If the lowest value of
using the value for V obtained in 9.1.1.1 and the values
S
the gate voltage that lies on the line of maximum slope (drawn in 9.1.5)
specified for D V and I (see X1.2).
G DM
is greater than the sum of the drain voltage and the threshold voltage, the
9.1.1.3 In each case, convenient scales for reading and
threshold voltage was determined for the linear region of operation.
graphing shall be used where the major unit (centimetre) is
r 9.1.12 If a value for the temperature coefficient of the
divided decimally and equals 1, 2, or 5 310 units of voltage
threshold voltage (a) is available for the devices under test,
or current, where r is a positive
...