ASTM F28-02

Standard Test Methods for Minority-Carrier Lifetime in Bulk Germanium and Silicon by Measurement of Photoconductivity Decay (Withdrawn 2003)

SCOPE
This standard was transferred to SEMI (www.semi.org) May 2003
1.1 These test methods cover the measurement of minority carrier lifetime appropriate to carrier recombination processes in bulk specimens of extrinsic single-crystal germanium or silicon.
1.2 These test methods are based on the measurement of the decay of the specimen conductivity after generation of carriers with a light pulse. The following two test methods are described:
1.2.1 Test Method A—Pulsed Light Method, that is suitable for both silicon and germination.
1.2.2 Test Method B—Chopped Light Method, that is specific to silicon specimens with resistivity 1 cm.
1.3 Both test methods are nondestructive in the sense that the specimens can be used repeatedly to carry out the measurement, but these methods require special bar-shaped test specimens of size (see ) and surface condition (lapped) that would be generally unsuitable for other applications.
1.4 The shortest measurable lifetime values are determined by the turn-off characteristics of the light source while the longest values are determined primarily by the size of the test specimen (see Table 2).
Note 1—Minority carrier lifetime may also be deduced from the diffusion length as measured by the surface photovoltage (SPV) method made in accordance with Test Methods F 391. The minority carrier lifetime is the square of the diffusion length divided by the minority carrier diffusion constant which can be calculated from the drift mobility. SPV measurements are sensitive primarily to the minority carriers; the contribution from majority carriers is minimized by the use of a surface depletion region. As a result lifetimes measured by the SPV method are often shorter than lifetimes measured by the photoconductivity decay (PCD) method because the photoconductivity can contain contributions from majority as well as minority carriers. In the absence of carrier trapping, both the SPV and PCD methods should yield the same values of lifetime (1) providing that the correct values of absorption coefficient are used for the SPV measurements and that the contributions from surface recombination are properly accounted for in the PCD measurement.
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. Specific hazard statements are given in Section 9.

General Information

• Status: Withdrawn
• Publication Date: 09-Dec-2002
• Withdrawal Date: 09-May-2003
• ICS: 29.045 - Semiconducting materials
• Technical Committee: F01 - Electronics

Relations

• Replaces: ASTM F28-91(1997) - Standard Test Methods for Minority-Carrier Lifetime in Bulk Germanium and Silicon by Measurement of Photoconductivity Decay
• Effective Date: 10-Dec-2002

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: F 28 – 02
Standard Test Methods for
Minority-Carrier Lifetime in Bulk Germanium and Silicon by
1
Measurement of Photoconductivity Decay
This standard is issued under the fixed designation F 28; 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.
from majority as well as minority carriers. In the absence of carrier
1. Scope
trapping, both the SPV and PCD methods should yield the same values of
1.1 These test methods cover the measurement of minority
4
lifetime (1) providing that the correct values of absorption coefficient are
carrier lifetime appropriate to carrier recombination processes
used for the SPV measurements and that the contributions from surface
in bulk specimens of extrinsic single-crystal germanium or
recombination are properly accounted for in the PCD measurement.
silicon.
1.5 This standard does not purport to address all of the
1.2 These test methods are based on the measurement of the
safety concerns, if any, associated with its use. It is the
decay of the specimen conductivity after generation of carriers
responsibility of the user of this standard to establish appro-
with a light pulse. The following two test methods are
priate safety and health practices and determine the applica-
described:
bility of regulatory limitations prior to use. Specific hazard
1.2.1 Test Method A—Pulsed Light Method, that is suitable
statements are given in Section 9.
2
for both silicon and germination.
1.2.2 Test Method B—Chopped Light Method, that is spe-
2. Referenced Documents
3
cific to silicon specimens with resistivity $1 V·cm.
2.1 ASTM Standards:
1.3 Both test methods are nondestructive in the sense that
D 5127 Guide for Ultra Pure Water Used in the Electronics
the specimens can be used repeatedly to carry out the mea-
5
and Semiconductor Industsry
surement, but these methods require special bar-shaped test
F 42 Test Method for Conductivity Type of Extrinsic
specimens of size (see Table 1) and surface condition (lapped)
6
Semiconducting Materials
that would be generally unsuitable for other applications.
F 43 Test Method for Resistivity of Semiconductor Materi-
1.4 The shortest measurable lifetime values are determined 6
als
by the turn-off characteristics of the light source while the
F 391 Test Methods for Minority Carrier Diffusion Length
longest values are determined primarily by the size of the test
in Extrinsic Semiconductors by Measurement of Steady-
specimen (see Table 2).
6
State Surface Photovoltage
2.2 Other Standards:
NOTE 1—Minority carrier lifetime may also be deduced from the
diffusion length as measured by the surface photovoltage (SPV) method
DIN 50440/1 Measurement of Carrier Lifetime in Silicon
made in accordance with Test Methods F 391. The minority carrier
Single Crystals by Means of Photoconductive Decay:
lifetime is the square of the diffusion length divided by the minority carrier 3
Measurement on Bar-Shaped Test Specimens
diffusion constant which can be calculated from the drift mobility. SPV
IEEE Standard 225 Measurement of Minority-Carrier Life-
measurements are sensitive primarily to the minority carriers; the contri-
time in Germanium and Silicon by the Method of Photo-
bution from majority carriers is minimized by the use of a surface
2
conductive Decay
depletion region. As a result lifetimes measured by the SPV method are
often shorter than lifetimes measured by the photoconductivity decay
3. Terminology
(PCD) method because the photoconductivity can contain contributions
3.1 Definitions:
3.1.1 minority carrier lifetime— of a homogeneous semi-
conductor, the average time interval between the generation
1
These test methods are under the jurisdiction of ASTM Committee F01 on
and recombination of minority carriers.
Electronicsand are the direct responsibility of Subcommittee F01.06 on Silicon
Materials and Process Control. 3.2 Definitions of Terms Specific to This Standard:
Current edition approved Dec. 10, 2002. Published February 2003. Originally
3.2.1 filament lifetime—the time constant, t , (in μs) of the
F
approved in 1963 as F 28–63T. Last previous edition approved in 1991 as
decay of the photoconductivity voltage, as defined by:
F 28 – 91 (1997).
2
This test method is based in part on IEEE Standard 225, Proceedings IRE, Vol
49, 1961, pp. 1292–1299.
3 4
DIN 50440/1 is an equivalent test method. It is the responsibility of DIN The boldface numbers in parenthesis refer to a list of references at the end of
Committee NMP 221, with which Committee F-1 maintains close liaison. DIN these test methods.
5
50440/1, is available from Beuth Verlag GmbH, Burggrafe
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