ASTM F674-92(1999)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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 674 – 92 (Reapproved 1999)
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 Practice for
Preparing Silicon for Spreading Resistance Measurements
This standard is issued under the fixed designation F 674; 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 preparation. The interpretation of spreading resistance mea-
surements depends in turn on the reproducibility of test
1.1 This practice covers the surface preparation of silicon
specimen measurements and on the reproducibility of calibra-
samples prior to measurement of resistivity variations by the
tion specimen measurements.
spreading resistance technique.
3.2 The procedures given are intended to confer a high
1.2 Separate procedures are given for preparation of large-
degree of reproducibility to spreading resistance measure-
area specimens for measurement of lateral resistivity variations
ments, and offer improvement over other preparation tech-
and for preparation of bevel-sectioned specimens (usually
niques.
small chips) for measurement of vertical variations of resistiv-
ity (depth profiling).
4. Interferences
NOTE 1—Benefits derived from diamond polishing are (1) stability and
4.1 Polishing of silicon with diamond causes light but
reproducibility of spreading resistance values on large area or beveled
controllable and uniform scratch damage to the silicon surface.
specimens, and (2) acuity of beveled surface geometry. The benefits of
Nevertheless, such uniform damage is compatible with spread-
stability and reproducibility are likely to apply to both conductivity types
ing resistance measurement data having very low scatter.
and all resistivity values; however, they have been demonstrated exten-
Contamination of the polishing medium with hard foreign
sively only for (111) n-type above 1 V·cm. Enhanced bevel acuity is
independent of conductivity-type or resistivity value.
particles can cause random heavy scratch damage to a speci-
men. If encountered by the spreading resistance probes, heavily
1.3 This standard does not purport to address all of the
scratch-damaged regions may yield erratic measurement re-
safety concerns, if any, associated with its use. It is the
sults.
responsibility of the user of this standard to establish appro-
4.2 Contamination of the specimen with water subsequent
priate safety and health practices and determine the applica-
to polishing may adversely affect the reproducibility of spread-
bility of regulatory limitations prior to use.
ing resistance measurements.
2. Summary of Practice
5. Front-Surface Diamond Polishing
2.1 Silicon specimens are polished using fine-grain diamond
5.1 Apparatus:
compound in a non-aqueous fluid. Polishing of silicon wafers
5.1.1 Polishing Machine—Oscillating-tubpolisher or other
or other large-area specimens is done against a nonwoven
similar small laboratory-scale polishing machine capable of
polishing cloth; bevel polishing of small specimens is done
providing randomized motion of the silicon specimen over the
against a frosted lapped glass surface. When polishing is
polishing pad.
complete, residual polishing compound is removed by an
5.1.2 Mounting Block and Fixture, to support and apply
organic solvent.
vertical load to the silicon specimen during polishing.
3. Significance and Use
5.1.3 Polishing Pad—Nonwoven cloth pad of a texture
specified as being compatible with the grain size of diamond
3.1 Resistivity is probably the single most important param-
used during polishing. The polishing pad should be adhesive-
eter for the characterization of silicon starting material for
backed for attaching to a support plate.
semiconductor device fabrication. Spreading resistance mea-
surements are used to measure resistivity variations in raw
NOTE 2—The preferred material is of a type identified as a “chemotex-
silicon crystals and completed semiconductor devices. The
tile.”
reproducibility of spreading resistance measurements on sili-
5.1.4 Support Plate, of glass or other similar hard material
con specimens is known to depend on the manner of specimen
compatible with the chosen polishing machine and capable of
This practice is under the jurisdiction of ASTM Committee F-1 on Electron-
icsand is the direct responsibility of Subcommittee F01.06 on Silicon Materials and Ehrstein, J. R., Ricks, D. R. and Robinson, L. A., “Spreading Resistance
Process Control. Measurements, Measurement Techniques for High Power Semiconductor Materials
Current edition approved May 15, 1992. Published July 1992. Originally and Devices,” Annual Report, Oct. 1, 1977 to Sept. 30, 1978, NBSIR 79-1756, F.F.
published as F 674 – 80. Last previous edition F 674 – 86. Oettinger, ed.
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.¬
F 674
providing a flat support for the polishing pad during polishing. 5.3 Procedure:
5.1.5 Microscope—Optical microscope having a total mag-
5.3.1 If not previously done, attach the polishing pad to the
nification of at least 303 and provision for oblique illumina-
rigid plate and place several drops of diamond polishing slurry
tion of the specimen.
at random locations on the polishing pad surface. Spread drops
5.1.6 Hot Plate capable of heating the sample mounting
of slurry in a reasonably uniform manner over the pad so that
block and wax to 150°C.
the pad surface becomes damp and so that there are no
5.2 Reagents and Materials:
freestanding layers of slurry. If the diamond is suspended in
5.2.1 Diamond Slurry—Synthetic or natural diamond with
paste, be sparing in the amount of paste applied to the pad.
grain size in the range 0.5 to 3 μm, inclusive, suspended in a
NOTE 6—Some polishing slurry adheres to the specimen and mounting
nonaqueous liquid or paste carrier.
fixture and is lost every time a specimen is removed and cleaned.
NOTE 3—The predominant causes of variation in the surface finish of
Replenish the slurry on the pad regularly with a few drops of fresh slurry.
the silicon specimen are expected to result from (1) the uniformity of
5.3.2 With the hot plate, heat the mounting block to the
particle size in the diamond grit, (2) the inclusion of a large fraction of
melting temperature of the wax. Mount the silicon specimen to
needle-shaped grains (fines) in addition to the preferred symmetric grains
(blocky diamond), and (3) in the case of diamond suspended in paste, the
the block with the wax. Allow the block to cool to room
uniformity of the diamond distribution in the paste. For a fixed diamond
temperature.
grain size, whether the diamond is natural, single-crystal synthetic, or
5.3.3 Assemble the mounting block and attach specimen to
polycrystalline synthetic should make little difference in the resulting
the sample mounting fixture and place this assembly on the
surface finish. However, the abrasive breakdown mechanisms differ
polishing pad in the polishing machine.
somewhat for the different types of diamond. Consequently, the size and
type of diamond should be chosen to give an acceptable cutting rate for the
5.3.4 In accordance with the manufacturer’s instructions for
specimen and machine conditions that will be used.
the polishing machine, polish until the specimen surface
NOTE 4—For use with large-area specimens, the appropriate size
exhibits a uniform density of random-direction scratches com-
diamond grain and, in part, the type of diamond to be used should be
parable to the pattern shown in Fig. 1. For this test, remove the
compatible with (1) the starting surface texture of the silicon, which may
polishing slurry from the specimen surface and examine that
range from as-sawn to prepolished, and (2) the load that is applied during
surface with the microscope.
polishing.
5.2.2 Solvent—Suitable nonaqueous solvent for removing
NOTE 7—The time required to reach a uniform surface finish w
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