ASTM F671-99

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.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 671 – 99
Standard Test Method for
Measuring Flat Length on Wafers of Silicon and Other
Electronic Materials
This standard is issued under the fixed designation F 671; 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 E 122 Practice for Choice of Sample Size to Estimate a
Measure of Quality for a Lot or Process
1.1 This test method covers techniques for determination of
2.2 ANSI/ASQC Standard:
the length of the flatted portion of a wafer periphery.
ANSI/ASQC Z1.4–1993 Sampling Procedures and Tables
1.2 This test method is intended primarily for use on
for Inspection by Attributes
electronic materials in the form of nominally circular edge-
2.3 SEMI Standard:
contoured wafers with flat lengths up to 65 mm. The precision
Specifications M 1, for Polished Monocrystalline Silicon
of this test method has been established directly only for silicon
Wafers
wafers, but it is not expected to be material dependent.
1.3 This test method is suitable for referee measurement
3. Terminology
purposes and may be used for routine acceptance measure-
3.1 Definitions:
ments when specified limits require test precision greater than
3.1.1 offset—a perpendicular deviation at either end region
can be obtained with hand held scale and unaided eye.
of a flat from the horizontal reference line, used to define the
1.4 This test method is independent of surface finish.
flat boundaries (see Fig. 1).
1.5 For application to wafers of diameter 3 in. or smaller,
3.1.2 primary flat—the flat of longest length that is com-
the values stated in inch-pound units are to be regarded as the
monly located with respect to a specific crystal plane; major
standard; the values stated in acceptable metric units are for
flat.
information only. For application to wafers of diameter larger
3.1.3 secondary flat—the flat or flats of a length shorter than
than 3 in., the values stated in acceptable metric units are to be
the primary flat, whose location with respect to the primary flat
regarded as the standard whether or not they appear in
identifies the type and orientation of the wafer (see SEMI
parentheses; the values stated in inch-pound units are for
Specifications M 1); minor flat.
information only.
NOTE 1—DIN 50441, Part 4, is a similar, but not equivalent method 4. Summary of Test Method
for determining flat length. In this method the flat length is calculated from
4.1 The specimen is aligned on an optical comparator. One
a measurement of a flat depth. This method does not provide any
end of the projected image of the flat is positioned on a
correction for rounding at the ends of the flat.
reference point on the viewing screen. The micrometer reading
1.6 This standard does not purport to address the safety
is recorded, and the stage is manipulated to scan to the opposite
concerns, if any, associated with its use. It is the responsibility
end of the flat where the micrometer reading is again recorded.
of the user of this standard to establish appropriate safety and
Flat length is the difference between the first and second
health practices and determine the applicability of regulatory
readings.
limitations prior to use.
5. Significance and Use
2. Referenced Documents
5.1 The length of fiducial flats is an important materials
2.1 ASTM Standards:
characteristic for determining the suitability of material for use
in semiconductor processing.
5.2 Automatic wafer handling equipment widely used in
This test method is under the jurisdiction of ASTM Committee F-1 on
semiconductor device manufacturing processes relies on iden-
Electronics and is the direct responsibility of Subcommittee F01.06 on Silicon
tification and orientation of the primary flat to obtain correct
Materials and Process Control.
alignment.
Current edition approved Dec. 10, 1999. Published February 2000. Originally
published as F 671 – 80. Last previous edition F 671 – 90 (1999).
DIN 50441, Part 4, Testing of Inorganic Semiconductor Materials: Measure-
ment or the Geometric Dimensions of Semiconductor Wafers: Diameter and Flat Annual Book of ASTM Standards, Vol 14.02.
Depth of Wafers is a similar, but not equivalent, method. It is the responsibility of Available from American Society for Quality Control, 611 East Wisconsin Ave.,
DIN Committee NMP 221, with which Committee F-1 maintains close liaison. This Milwaukee, WI 53202
document is available from Beuth Verlag GmbH, Burgrafenstrasse 4–10, D-1000, Available from Semiconductor Equipment and Materials International, 805
Berlin 30, Germany. East Middlefield Rd., Mountain View, CA 94043.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
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 671
FIG. 2 Overlay
FIG. 1 Illustration of the Use of Offset
5.3 This test method is suitable for use in research, devel-
7.2 Microscope Stage Micrometer on clear glass or plastic,
opment, process control, quality assurance, and materials
the scale to be at least 0.05 in. (1.3 mm) long with 0.001-in.
acceptance applications.
(25-μm) divisions.
7.3 Machinists’ Steel Scale, 6 in. (150 mm) minimum
6. Interferences
length, graduated in 0.02 in. (0.50 mm) or 0.01 in. (0.25 mm).
6.1 Some operations performed after slicing, such as me-
chanical edge grinding and chemical etching, may reduce 8. Sampling
profile definition at the ends of the flatted area.
8.1 Unless otherwise specified, Practice E 122 shall be used.
6.2 Backlash in the micrometer head assemblies may result
When so specified, appropriate sample sizes shall be selected
in erroneous readings.
from each lot in accordance with ANSI/ASQC Z1.4–1993.
6.3 Failure to maintain sharp focus on the sample compara-
Inspection levels shall be agreed upon between the supplier and
tor screen image during measurement can introduce errors.
purchaser.
6.4 Comparator optics may sometimes incorporate image-
reversal elements which result in image conditions opposite to 9. Calibration
those described by this test method.
9.1 Comparator Optical Magnification:
9.1.1 Place the microscope stage micrometer on the com-
7. Apparatus
parator sample stage so that its projected image is at the center
7.1 Shadowgraph Comparator, equipped as follows:
of the viewing screen.
7.1.1 203 optical system,
9.1.2 With a steel scale on the viewing screen, count the
7.1.2 Viewing screen with minimum diameter of 10 in. (254
number of 0.001-in. (25-μm) lines projected over a 1-in.
mm), and
(25-mm) distance. Divide the number into 1000 to obtain the
7.1.3 Sample stage capable of minimum micrometer travel
actual magnification.
of 2 in. or 50 mm in the X direction and goniometer rotation in
9.1.3 Magnification must be between 19.8 and 20.2 to be
the X-Y plane.
usable for this method.
7.1.3.1 Stage travel in the X direction shall move the
9.2 Comparator Micrometer Travel—X Direction:
projected image horizontally on the viewing screen. Travel in
9.2.1 Set the X-travel micrometer to zero.
the Y direction shall move the projected image vertically on the
9.2.2 Align the projected image of the microscope stage
viewing screen.
micrometer such that the array
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