ASTM F996-98

Standard Test Method for Separating an Ionizing Radiation-Induced MOSFET Threshold Voltage Shift Into Components Due to Oxide Trapped Holes and Interface States Using the Subthreshold Current-Voltage Characteristics

SCOPE
1.1 This test method covers the use of the subthreshold charge separation technique for analysis of ionizing radiation degradation of a gate dielectric in a metal-oxide-semiconducter-field-effect transistor (MOSFET) and an isolation dielectic in a parasitic MOSFET.      The subthreshold technique is used to separate the ionizing radiation-induced inversion voltage shift, [delta]VINV into voltage shifts due to oxide trapped charge, [delta]Vot and interface traps, [delta]Vit. This technique uses the pre- and post-irradiation drain to source current versus gate voltage characteristics in the MOSFET subthreshold region.
1.2 Procedures are given for measuring the MOSFET subthreshold current-voltage characteristics and for the calculation of results.
1.3 The application of this test method requires the MOSFET to have a substrate (body) contact. MOSFETs on silicon-on-insulator (SOI) technology must have body ties.
1.4 Both pre- and post-irradiation MOSFET subthreshold source or drain curves must follow an exponential dependence on gate voltage for a minimum of two decades of current.
1.5 This standard does not purport to address all of the safety problems, 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.

General Information

• Status: Historical
• Publication Date: 09-May-1998
• ICS: 31.080.30 - Transistors
• Technical Committee: F01 - Electronics
• Drafting Committee: F01.11 - Nuclear and Space Radiation Effects

Relations

• Replaced By: ASTM F996-98(2003) - Standard Test Method for Separating an Ionizing Radiation-Induced MOSFET Threshold Voltage Shift Into Components Due to Oxide Trapped Holes and Interface States Using the Subthreshold Current-Voltage Characteristics
• Effective Date: 10-May-1998

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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 996 – 98
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Separating an Ionizing Radiation-Induced MOSFET
Threshold Voltage Shift Into Components Due to Oxide
Trapped Holes and Interface States Using the Subthreshold
1
Current–Voltage Characteristics
This standard is issued under the fixed designation F 996; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope bility of regulatory limitations prior to use.
1.1 This test method covers the use of the subthreshold
2. Terminology
charge separation technique for analysis of ionizing radiation
2.1 Definitions of Terms Specific to This Standard:
degradation of a gate dielectric in a metal-oxide-
2.1.1 anneal conditions—the bias and temperature of the
semiconducter-field-effect transistor (MOSFET) and an isola-
2 , 3, 4
MOSFET in the time period between irradiation and measure-
tion dielectic in a parasitic MOSFET. The subthreshold
ment.
technique is used to separate the ionizing radiation-induced
2.1.2 doping concentration, N—N-or P-type doping, is the
inversion voltage shift, DV into voltage shifts due to oxide
INV
concentration of the MOSFET channel region adjacent to the
trapped charge,D V and interface traps,D V . This technique
ot it
oxide/silicon interface.
uses the pre- and post-irradiation drain to source current versus
2.1.3 inversion current, I —the MOSFET channel current
INV
gate voltage characteristics in the MOSFET subthreshold
at a gate-source voltage equal to the inversion voltage.
region.
2.1.4 inversion voltage, V —the gate-source voltage cor-
INV
1.2 Procedures are given for measuring the MOSFET sub-
responding to a surface potential of 2f .
B
threshold current-voltage characteristics and for the calculation
2.1.5 irradiation biases—the biases on the gate, drain,
of results.
source, and substrate of the MOSFET during irradiation.
1.3 The application of this test method requires the MOS-
2.1.6 midgap current, I —the MOSFET channel current
MG
FET to have a substrate (body) contact.
at a gate-source voltage equal to the midgap voltage.
1.4 Both pre- and post-irradiation MOSFET subthreshold
2.1.7 midgap voltage, V —the gate-source voltage corre-
MG
source or drain curves must follow an exponential dependence
sponding to a surface potential of f .
B
on gate voltage for a minimum of two decades of current.
2.1.8 oxide thickness, t —the thickness of the oxide of the
ox
1.5 The values given in SI units are to be regarded as
MOSFET under test.
standard. No other units of measurement are included in this
2.1.9 potential, f —the potential difference between the
B
test method.
Fermi level and the intrinsic Fermi level.
1.6 This standard does not purport to address all of the
2.1.10 subthreshold swing—the change in the gate-source
safety concerns, if any, associated with its use. It is the
voltage per change in the log source or drain current of the
responsibility of the user of this standard to establish appro-
MOSFET channel current below the inversion current. The
priate safety and health practices and determine the applica-
value of the subthreshold swing is expressed in V/decade (of
current).
1
This test method is under the jurisdiction of ASTM Committee F–1 on 2.1.11 surface potential, f —the potential at the MOSFET
s
Electronics and is the direct responsibility of Subcommittee F01.11 on Quality and
semiconductor surface measured with respect to the intrinsic
Hardness Assurance.
Fermi level.
Current edition approved May 10, 1998. Published September 1998. Originally
published as F 996 – 91. Last previous edition F 996 – 92.
2
3. Summary of Test Method
For formulation of subthreshold charge separation technique see McWhorter, P.
J. and P. S. Winokur, “Simple Technique for Separating the Effects of Interface Traps
3.1 The subthreshold charge separation technique is based
and Trapped Oxide Charge in MOS Transistors,” Applied Physics Letters, Vol 48,
on standard MOSFET subthreshold current-voltage character-
1986, pp. 133–135.
3
DNA-TR-89-157, Subthreshold Technique for Fixed and Interface Trapped istics. The subthreshold drain or source current at a fixed drain
Charge Separation in Irradiated MOSFETs, available from National Technical
to source voltage, V , is measured as a function of gate
DS
Information Service, 5285 Port Royal Rd., Springfield, VA 22161.
voltage from the leakage current (or limiting resolution of the
4
Saks, N. S., and Anacona, M. G., “Generation of Interface States by Ionizing
mea
...