ASTM F42-93(1997)

Standard Test Methods for Conductivity Type of Extrinsic Semiconducting Materials

SCOPE
1.1 These test methods  cover the determination of the conductivity type of extrinsic semiconductors. While explicit details are given for germanium and silicon, inclusion of other extrinsic materials such as gallium arsenide and indium antimonide should be feasible. For the latter compounds, however, applicability has not been formally verified by round-robin tests. Determinations can be made most reliably on homogeneous bulk material, but these test methods may also be used to map regions of different conductivity type on the surfaces of inhomogeneous specimens. These test methods have not been tested on layered structures such as epitaxial layers. Measurements on these structures may give erroneous indications of conductivity type.  
1.2 Four test methods are described:  
1.2.1 Test Method A -Hot-Probe Thermal EMF Conductivity-Type Test.  
1.2.2 Test Method B -Cold-Probe Thermal EMF Conductivity-Type Test.  
1.2.3 Test Method C -Point-Contact Rectification Conductivity-Type Test.  
1.2.4 Test Method D -Type-All  system operating in two modes:  
1.2.4.1 Rectification Conductivity-Type Test.  
1.2.4.2 Thermal EMF Conductivity-Type Test.  
1.3 Experience has shown that Test Method A (hot-probe) gives dependable results in n- and p-type silicon having a room-temperature resistivity up to 1000 [omega][dot]cm.  Note 1-Resistivity of germanium specimens may be measured in accordance with Test Methods F43 and resistivity of silicon slices may be measured in accordance with Test Methods F43 or Test Method F84.
1.4 Test Method B (cold-probe) gives dependable results for n- and p-type germanium having a room-temperature resistivity of 20 [omega][dot]cm or less and for n- and p-type silicon having a resistivity up to 1000 [omega][dot]cm (Note 1). This technique has the advantage over the hot-probe test method in that the signal amplitude can be increased by developing a greater temperature difference between the two probes.  
1.5 Test Method C (rectification) is a simple convenient technique which gives dependable results for n- and p-type silicon with room-temperature resistivity between 1 and 1000 [omega][dot]cm. This test method is not recommended for germanium (Note 1).  
1.6 Test Method D (type-all rectification mode) is appropriate for use on n- and p-type silicon having a room-temperature resistivity between 0.1 and 1000 [omega][dot]cm, inclusive (Note 1).  
1.7 Test Method D (type-all thermal emf mode) is appropriate for use on n- and p-type silicon having a room-temperature resistivity between 0.002 and 0.1 [omega][dot]cm, inclusive (Note 1).  
1.8 These test methods may apply outside the limits given above, but their suitability outside these limits has not been verified experimentally.  
1.9 It is recommended that if satisfactory results can not be obtained with the use of these test methods that conductivity type be determined from Hall-effect measurements as described in Test Methods F76.  Note 2-DIN 50432 covers technical equivalents to Test Methods A and C of these test methods, but does not include Test Methods B and D.
1.10 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.

General Information

• Status: Historical
• Publication Date: 09-Dec-1997
• ICS: 77.040.01 - Testing of metals in general
• Technical Committee: F01 - Electronics

Relations

• Replaced By: ASTM F42-02 - Standard Test Methods for Conductivity Type of Extrinsic Semiconducting Materials (Withdrawn 2003)
• Effective Date: 10-Dec-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
contact ASTM International (www.astm.org) for the latest information.
DIN 50432
Designation: F 42 – 93 (Reapproved 1997)
Standard Test Methods for
Conductivity Type of Extrinsic Semiconducting Materials
ThisstandardisissuedunderthefixeddesignationF42;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.4 TestMethodB(cold-probe)givesdependableresultsfor
n- and p-type germanium having a room-temperature resistiv-
1.1 These test methods cover the determination of the
ity of 20 V·cm or less and for n- and p-type silicon having a
conductivity type of extrinsic semiconductors. While explicit
resistivity up to 1000 V·cm (Note 1). This technique has the
details are given for germanium and silicon, inclusion of other
advantage over the hot-probe test method in that the signal
extrinsic materials such as gallium arsenide and indium anti-
amplitude can be increased by developing a greater tempera-
monideshouldbefeasible.Forthelattercompounds,however,
ture difference between the two probes.
applicability has not been formally verified by round-robin
1.5 Test Method C (rectification) is a simple convenient
tests. Determinations can be made most reliably on homoge-
technique which gives dependable results for n- and p-type
neousbulkmaterial,butthesetestmethodsmayalsobeusedto
silicon with room-temperature resistivity between 1 and 1000
map regions of different conductivity type on the surfaces of
V·cm. This test method is not recommended for germanium
inhomogeneous specimens. These test methods have not been
(Note 1).
tested on layered structures such as epitaxial layers. Measure-
1.6 Test Method D (type-all rectification mode) is appropri-
ments on these structures may give erroneous indications of
ate for use on n- and p-type silicon having a room-temperature
conductivity type.
resistivity between 0.1 and 1000 V·cm, inclusive (Note 1).
1.2 Four test methods are described:
1.7 Test Method D (type-all thermal emf mode) is appro-
1.2.1 Test Method A—Hot-Probe Thermal EMF
priate for use on n- and p-type silicon having a room-
Conductivity-Type Test.
temperature resistivity between 0.002 and 0.1 V·cm, inclusive
1.2.2 Test Method B—Cold-Probe Thermal EMF
(Note 1).
Conductivity-Type Test.
1.8 These test methods may apply outside the limits given
1.2.3 Test Method C—Point-Contact Rectification
above, but their suitability outside these limits has not been
Conductivity-Type Test.
verified experimentally.
1.2.4 Test Method D—Type-All system operating in two
1.9 It is recommended that if satisfactory results can not be
modes:
obtained with the use of these test methods that conductivity
1.2.4.1 Rectification Conductivity-Type Test.
type be determined from Hall-effect measurements as de-
1.2.4.2 Thermal EMF Conductivity-Type Test.
scribed in Test MethodsF76.
1.3 Experience has shown that Test Method A (hot-probe)
gives dependable results in n- and p-type silicon having a
NOTE 2—DIN 50432 covers technical equivalents to Test Methods A
room-temperature resistivity up to 1000 V·cm. and C of these test methods, but does not include Test Methods B and D.
1.10 This standard does not purport to address all of the
NOTE 1—Resistivity of germanium specimens may be measured in
accordancewithTestMethodsF43andresistivityofsiliconslicesmaybe
safety concerns, if any, associated with its use. It is the
measured in accordance with Test MethodsF43 or Test MethodF84.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
These test methods are under the jurisdiction of ASTM Committee F-1 on
2. Referenced Documents
Electronics, and are the direct responsibility of Subcommittee F01.06 on Silicon
Materials and Process Control.
2.1 ASTM Standards:
Current edition approved Dec. 10, 1997. Published October 1993. Originally
D1125 Test Methods for Electrical Conductivity and Re-
published as F42–64 T. Last previous edition F42–88.
sistivity of Water
DIN 50432 is an equivalent method. It is the responsibility of DIN Committee
NMP 221, with which Committee F-1 maintains close technical liaison.
F43 Test Methods for Resistivity of Semiconductor Mate-
DIN 50432, Testing of Inorganic Semiconductor Materials: Determining the 5
rials
Conductivity Type of Silicon or Germanium by Means of the Rectification Test or
F76 Test Methods for Measuring Resistivity and Hall
Hot Probe, is available from Beuth Verlag GmbH, Burggrafenstrasse 4-10, D-1000
Berlin 30, Federal Republic of Germany.
Keenan, W. A., Schneider, C. P., and Pillus, C. A., “Type-All System for
Determining Semiconductor Conductivity Type,” Solid State Technology, Vol 14, Annual Book of ASTM Standards, Vol 11.01.
No. 3, March 1971. Annual Book of ASTM Standards, Vol 10.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
contact ASTM International (www.astm.org) for the latest information.
F 42 – 93 (1997)
Coefficient and Determining Hall Mobility in Single- contact will be reverse-biased and will experience the major
Crystal Semiconductors portion of the voltage drop. During the following half-cycle
F84 Test Methods for Measuring Resistivity of Silicon this junction will be forward-biased and the voltage drop will
Slices with a Collinear Four-Probe Array besmallcomparedtothatofthefirsthalf-cycle.Thisinequality
of voltages results in a d-c component which is detected by a
3. Terminology
third point contact.
4.4 Test Method D, Thermal EMF Mode—In this test
3.1 Definitions of Terms Specific to This Standard:
method,athermalgradientisestablishedinthespecimenbyan
3.1.1 conductivity type—Defines the nature of the majority
alternatingcurrentpassingthroughapairofpointcontacts.The
of carriers in the specimen.
thermal emf resulting from the thermal gradient is then
3.1.2 n-type—avarietyofsemiconductivematerialinwhich
detected by a second pair of point contacts. The point contact
the majority current carriers are electrons, formed when donor
nearestthefirstpairwillbethewarmerand,in n-typematerial,
impurities are incorporated into the crystal structure in small
will be positive with respect to the second point contact of the
concentrations.
pair. With p-type material the warmer contact will be negative
3.1.3 p-type—avarietyofsemiconductivematerialinwhich
with respect to the second contact.
the majority current carriers are holes, formed when acceptor
impurities are incorporated into the crystal structure in small
concentrations. 5. Significance and Use
3.1.4 thermal emf—the net emf set up in a thermocouple
5.1 Thedeterminationofconductivitytypeandthepresence
under conditions of zero current. Synonymous with Seebeck
of junctions in semiconductors is important in research and
emf.
development, and in processing or inspection of semiconduct-
ing materials for device fabrication.
4. Summary of Test Methods
4.1 Test Methods A and B—In both of these test methods,
6. Interferences
thesignofthethermalemfgeneratedbetweentwometalprobe
6.1 Test Method A (Hot-Probe):
contacts to the specimen held at different temperatures is used
6.1.1 Some high-resistivity silicon and germanium speci-
to determine conductivity type. One of the probes is main-
mens may be nearly intrinsic at the hot-probe temperature;
tained at room temperature while the other is heated (Test
since the mobility of the electrons exceeds that of holes, the
MethodA) or cooled (Test Method B). The warmer probe will
thermoelectric power is always negative at these temperatures.
bepositivewithrespecttothecoolerprobewhenthespecimen
6.1.2 Oxide coating buildup on the hot probe can produce
is n-type and negative when the specimen is p-type. The
unreliable measurements.
polarityisobservedonacenter-zerometerwhichmaybeeither
6.1.3 n-typegermanium with room-temperature resistivity
voltage or current sensitive. Since most of the temperature
greater than 40 V·cm can show p-type conductivity due to
difference occurs in the region of the probe which is not at
insufficient probe force (Note 1).
room temperature, the sign observed is governed by the
6.2 Test Method B (Cold Probe):
conductivity type of the portion of the specimen at this probe
6.2.1 The cold probe should be maintained free of ice. Ice
contact.
formed during prolonged periods of usage in ordinary ambient
4.2 Test Method C—In this test method, the direction of the
air has been found to give erratic results.
current through a point contact is used to determine the
6.2.2 Oxide coating buildup on the cold probe can produce
conductivity type of the specimen. A metal point contact to a
unreliable measurements.
p-type semiconductor will pass current when the semiconduc-
6.2.3 n-type germanium with room-temperature resistivity
tor is positive while a metal point contact to an n-type
greater than 20 V·cm can show p-type conductivity due to
semiconductor will pass current when the semiconductor is
insufficient probe force (Note 1).
negative.An alternating potential is applied between the point
6.3 Test Method C (Rectification):
contact and a second large area contact. The direction of
6.3.1 Since this test method indicates primarily the surface-
current is observed on a zero-center current sensitive meter, an
conductivitytype,extremecaremustbetakeninpropersurface
oscilloscope, or a curve tracer. Since rectification occurs at the
preparation. A surface oxide can act as an insulator so that no
point contact rather than at the large area contact, the direction
voltage is indicated by the meter.
of current is governed by the conductivity type of the portion
6.3.2 Reversed readings can sometimes occur if the large-
of the specimen at the point contact.
area contact is not held firmly. In such cases, a heavy force on
4.3 Test Method D, Rectification Mode—Inthistestmethod,
thepointcontactcancausethelarge-areacontacttobecomethe
the polarity of the voltage required to reverse-bias a point
effective rectifying contact and give reversed meter readings.
contact is used to determine the conductivity type of the
6.3.3 Erroneous readings may arise from stray pickup
specimen. An alternating potential is applied between two
caused by touching the specimen with hands or objects other
point contacts to the specimen. During one half-cycle a given
than the probe.
6.3.4 An etched surface is not recommended because vari-
ousetchantsandetchingtechniquemayintroduceuncontrolled
Scaff, J. H. and Thearer, H. C., Edited by Scaff, J. H., Bridgers, H. E., and
variations in surface characteristics.
Shive, J. N., Transistor Technology, D. Van Nostrand Co., Inc., New York, Vol 1,
1958, p. 12. 6.4 Test Method D (Type-All):
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Please
contact ASTM International (www.astm.org) for the latest information.
F 42 – 93 (1997)
6.4.1 Erroneous indications may result if the rectification
modeisusedwithverylow-resistivitymaterialwhichresultsin
alowoutputsignal.Forsilicon,useoftherectificationmodein
cases where the output is less than 0.5 V is not recommended.
6.4.2 Erroneous indications may result if the thermal emf
mode is used with high-resistivity material.
6.5 All test methods may give erroneous readings if exces-
sivelightfallsonthespecimen,especiallywithhigh-resistivity
material.
6.6 Ambient radio-frequency energy may cause spurious
rectification and erroneous indications.
7. Apparatus
NOTE 3—The instrumentation described in these test methods was in
common use at the time the test methods were developed. It is now
possible to perform many of the necessary functions using more modern
instruments. Such instruments may be substitutes for the apparatus
described in this section provided the user can show equivalence for the
purposes of the measurement.
FIG. 2 Apparatus for Determination of Conductivity Type by Cold-
7.1 Test Method A (Hot-Probe)—The apparatus required
Probe Thermal EMF
consists of the following (Fig. 1):
7.1.1 Two Probes, preferably stainless steel or nickel, each
probe tips shall be tapered to nominal 60° cones and the radius
with one end terminated in a 60° cone. One of the probes has
of contact shall be approximately 200 µm.
a 10 to 25-W heater wound about its shank. The heater is
7.2.2 Center-Zero Null Indicator, with a deflection sensitiv-
electrically insulated from the probe. This probe may be
−9
ity of at least, 1 310 A/mm.
conveniently fashioned from a midget-type soldering iron by
7.3 Test Method C (Rectification)—The apparatus required
attachingtheconnectingleaddirectlytoapointnearthetipand
consists of the following (Fig. 3, Fig. 4, and Fig. 5):
inserting a probe point, as described above, into the tip.
7.3.1 Adjustable Autotransformer, such that a 50 to 60-Hz
7.1.2 Variable Power Supply, capable of raising the tem-
signal of 0 to 15-V peak to peak can be supplied to the
perature of the heated probe to 40 to 60°C.
specimen (Fig. 3 and Fig. 4).
7.1.3 Center-Zero Null Indicator, with a deflection sensitiv-
−9
7.3.2 Isolation Transformer, to avoid grounding problems
ity of at least 1 310 A/mm.
and for safety (Fig. 3 and Fig. 4).
7.1.4 Suitable Temperature Sensor, for determining tem-
7.3.3 Probe, consisting of a suitable conductor such as
perature of the hot probe in the range from 40 to 60°C.
copper,tungsten,aluminum,orsilver.Oneendshallbetapered
7.2 Test Method B (Cold-Probe)—The apparatus required
with a point radius not greater than 50 µm.
consists of the following (Fig. 2):
7.3.4 Large-Area Ohmic Contact, consisting of a flexible
7.2.1 Two Probes, with tips of copper or aluminum and
conductor such as lead or indium foil secured firmly to the
shanks insulated with a material such as phenolic fiber. The
specimen by a spring-loaded clamp or other equivalent means.
thermal mass of one of the probes shall be at least that of 15 g
7.3.5 Center-Zero Meter, with a sensitivity of at least 200
ofaluminumsothatitwillremainatorbelow−40°Cfor5min
µAfullscale(Fig.3),anoscilloscope(Fig.4),oracurvetracer
in an ambient of 25°C after immersion in liquid nitrogen. The
(Fig. 5).
7.4 Test Method D (Type-All, Rectification Mode)—The
apparatus required consists of the following (Fig. 6):
FIG. 1 Apparatus for Determination of Conductivity Type by Hot- FIG. 3 Circuit for Determination of Conductivity Type by Point-
Probe Thermal EMF Contact Rectification with the Use of a Current Detector
NOTICE: This stand
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