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SEMI MF43-0705 © SEMI 2003, 2005 3 4.4 DIN Standar ds 50430 — Measurement of the Specific Electrical Resistivit y of Silicon or Germanium Single Crystals in Bars Using the Two-probe Direct Current Method 4 50431 — Measur…
SEMI MF43-0705 © SEMI 2003, 2005 2
3.1.1 Photoconductive and photovoltaic effects can seriously influence the observed resistivity, particularly with
nearly intrinsic material. Therefore make all determinations in a dark chamber unless experience has shown that the
material is insensitive to ambient illumination.
3.1.2 Spurious currents can be introduced in the testing circuit when the equipment is located near high-frequency
generators. If equipment is located near such sources, adequate shielding must be provided.
3.1.3 Minority carrier injection during the measurement can occur due to the electric field in the specimen. With
material possessing high minority carrier lifetime and high resistivity, such injection can result in a lowering of the
resistivity for distance of several centimeters. Carrier injection can be detected by repeating the measurements at
lower current. In the absence of injection no increase in resistivity should be observed. It is recommended that the
current used in a resistivity measurement be as low as possible, consistent with the required precision.
3.1.4 Semiconductors have a significant temperature coefficient of resistivity. Consequently, the temperature of
the specimen should be known at the time of the measurement and the current used should be small to avoid
resistive heating. If resistive heating is suspected, it can be detected by a change in readings as a function of time
starting immediately after the current is applied. Temperature coefficients for extrinsic germanium and silicon near
room temperature are available in the literature.
1
For referee purposes, it is recommended that the test be performed
at 23 ± 0.5°C.
NOTE 3: Temperature correction factors for silicon are given in tabular form in SEMI MF84 together with equations for
generating the factors.
3.1.5 Vibration of the probes sometimes causes troublesome changes in the contact resistance. If difficulty is
encountered, shock mount the apparatus.
4 Referenced Standards and Documents
4.1 SEMI Standards
SEMI M1 — Specifications for Polished Monocrystalline Silicon Wafers
SEMI M59 — Terminology for Silicon Technology
SEMI MF84 — Test Method for Measuring Resistivity of Silicon Wafers with an In-line Four-point Probe
SEMI MF374 — Test Method for Sheet Resistance of Silicon Epitaxial, Diffused, Polysilicon, and Ion-implanted
Layers Using an In-line Four-point Probe
SEMI MF397 — Test Method for Resistivity of Silicon Bars Using a Two-point Probe
SEMI MF533 — Test Method for Thickness and Thickness Variation of Silicon Slices
SEMI MF2074 — Guide for Measuring Diameter of Silicon and Other Semiconductor Wafers
4.2 ANSI Standard
B74.10 — Specification for Grading of Abrasive Microgrits
2
4.3 ASTM Standard
F 76 — Test Methods for Measuring Resistivity and Hall Coefficient and Determining Hall Mobility in Single-
Crystal Semiconductors
3
1 Bullis, W. M., Brewer, F. H., Kolstad, C. D., and Swaratzendruber, L. I., “Temperature Coefficient of Resistivity of Silicon and Germanium
near Room Temperature,” Solid State Electron. 11, 639646 (1968).
2 American National Standards Institute, American National Standards Institute, New York Office: 25 West 43rd Street, New York, NY 10036,
USA. Telephone: 212.642.4900, Fax: 212.398.0023, Website:
www.ansi.org
.
3 Annual Book of ASTM Standards, Vol 10.04, ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. Telephone: 610-
832-9500, Fax: 610-832-9555, Website:
www.astm.org
.
SEMI MF43-0705 © SEMI 2003, 2005 3
4.4 DIN Standards
50430 — Measurement of the Specific Electrical Resistivity of Silicon or Germanium Single Crystals in Bars Using
the Two-probe Direct Current Method
4
50431 — Measurement of the Electrical Resistivity of Silicon or Germanium Single Crystals by Means of the Four-
point-probe Direct Current Method with Collinear Four-probe Array
4
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 Definitions
5.1.1 Terms relating to silicon and other semiconductor technology are defined in SEMI M59.
6 Summary of Test Methods
6.1 Two-Probe Method — A direct current, I, is passed through ohmic contacts at the ends of a bar specimen and
the potential difference, V, is determined between two probes placed along the current direction (Figure 1). The
resistivity,
, is calculated from the current and potential values and factors appropriate to the geometry.
6.2 Four-Probe Method — An in-line four-point probe is placed on a flat surface of a solid specimen which can be
approximated as semi-infinite. A direct current, I, is passed through the specimen between the outer probes and the
resulting potential difference, V, is measured between the inner probes (Figure 2). The resistivity,
, is calculated
from the current and potential values and factors appropriate to the geometry.
4 Deutches Institut für Normung e.V., standards are available in both English and German editions from Beuth Verlag GmbH, Burggrafenstrasse
6, 10787 Berlin, Germany, Telephone: 49.30.2601-0, Fax: 49.30.2601.1263, Website:
www.beuth.de.
Figure 1
Specimen and Probe Arrangement for Two-Probe
Measurements on a Rectangular Bar
Figure 2
Specimen and Probe Arrangement for Four-Probe
Measurements on a Semi-Infinite Solid Specimen
7 Apparatus
7.1 Jigs — Suitable for mounting the specimens and contacting them with either two or four probes as required.
7.1.1 Probes — Shall be individually spring mounted and shall be loaded with a force of 1.5 ± 0.5 N. The probes
may be made from hardened tool steel, tungsten carbide, or other conducting metal and may be chisel shaped for
measurement of curved surfaces or pointed for measurement on flat sections. In the case of point probes, the
nominal radius of the tips shall be initially 25 to 50 m. With all probing devices, frequent checking of the probe
spacing with a calibrating microscope is desirable. Probes shall be replaced or resharpened when necessary to
maintain the required spacing tolerance. Isolation resistance between the probes shall be at least 10
9
.
SEMI MF43-0705 © SEMI 2003, 2005 4
NOTE 4: Detailed procedures for in situ determination of the spacing between adjacent probes of an in-line four-point probe are
given in the Probe Assembly paragraph of the Suitability of Test Equipment section of SEMI MF84. These procedures, for
which equipment described in the Probe Alignment and Separation paragraph of the Apparatus section of SEMI MF84 is
required, can be used to establish probe spacings and their repeatability for both two- and four-probe assemblies. When four-
probe measurements are made on semi-infinite solids, the probe spacing correction factor, F
sp
, in Equation 5 of the Suitability of
Test Equipment section, of SEMI MF84 should be replaced by:
s
s
F
sp
2
12511 . (1)
where:
s
2
= spacing between inner pair of probes, cm, and
s = average probe spacing, cm.
In general, however, the correction for unequal probe spacing is neglected.
7.1.2 Probe Mountings — Shall be furnished with appropriate guides to ensure that the probes contact the
specimen reproducibly with a probe spacing tolerance of ±0.5%.
7.2 Electrical Circuit (see Figure 3)
7.2.1 Constant Current Source — Capable of supplying currents between 10
1
and 10
5
A. The current must be
known and maintained constant to ±0.5% during the measurement.
7.2.2 Current Reversing Switch
7.2.3 Standard Resistor — With a resistance within a factor of 100 of that of the specimen. (See Note 5.)
7.2.4 Double-Throw, Double-Pole Potential Selector Switch. (See Note 5.)
7.2.5 Potentiometer-Galvanometer or Electronic Voltmeter — Capable of measuring potential differences between
10
4
and 1 V of either polarity to ±0.5%. The input impedance must exceed 1000 times the total contact plus bulk
resistance of the specimen.
NOTE 5: The standard resistor and potential selector switch are not required for routine four-probe measurements if a calibrated
current source is used.
NOTE: The standard resistor and potential selector switch are not required for routine
four-probe measurements if a calibrated current source is used.
Figure 3
Recommended Electrical Circuit for Two-Probe and Four-Probe Resistivity Measurements
NOTE 6: The electrical measuring circuit may also measure either resistance or current directly. Any electrical circuit that
meets the requirements of the Electrical Equipment part of the Suitability of Test Equipment section, of SEMI MF84 is
acceptable for use in this test method. If the procedures of SEMI MF84 are used to evaluate the adequacy of the electrical
equipment, an appropriate analog test circuit as described in the Analog Test Circuit paragraph of the Apparatus section of
SEMI MF84 is required.