ASTM F928-93(1999)

Standard Test Methods for Edge Contour of Circular Semiconductor Wafers and Rigid Disk Substrates

SCOPE
1.1 These test methods provide means for examining the edge contour of circular wafers of silicon, gallium arsenide, and other electronic materials, and determining fit to limits of contour specified by a template that defines a permitted zone through which the contour must pass. Principal application of such a template is intended for, but not limited to, wafers that have been deliberately edge shaped.
1.2 Two test methods are described. One is destructive and is limited to inspection of discrete points on the periphery, including flats. The contour of deliberately edge-shaped wafers may not be uniform around the entire periphery, and thus the discrete location(s) may or may not be representative of the entire periphery. The other test method is nondestructive and suitable for inspection of all points on the wafers periphery except flats.
1.3 The nondestructive test method may also be applied to the examination of the edge contour of the outer periphery of substrates for rigid disks used for magnetic storage of data.
Note 1—Reference to wafers in the remainder of this standard shall be interpreted to include substrates for rigid disks unless the phrase "of electronic materials" is also included in the context.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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.

General Information

• Status: Historical
• Publication Date: 09-Jan-2002
• ICS: 29.045 - Semiconducting materials
• Technical Committee: F01 - Electronics

Relations

• Replaced By: ASTM F928-02 - Standard Test Methods for Edge Contour of Circular Semiconductor Wafers and Rigid Disk Substrates (Withdrawn 2003)
• Effective Date: 10-Jan-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: F 928 – 93 (Reapproved 1999)
Standard Test Methods for
Edge Contour of Circular Semiconductor Wafers and Rigid
Disk Substrates
This standard is issued under the fixed designation F 928; 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 Measure of Quality for a Lot or Process
2.2 Military Standard:
1.1 These test methods provide means for examining the
MIL-STD-105D Sampling Procedures and Tables for In-
edge contour of circular wafers of silicon, gallium arsenide,
spection by Attributes
and other electronic materials, and determining fit to limits of
2.3 SEMI Standards:
contour specified by a template that defines a permitted zone
SEMI M1, Specifications for Polished Monocrystalline Sili-
through which the contour must pass. Principal application of
con Wafers
such a template is intended for, but not limited to, wafers that
SEMI M9, Specifications for Polished Monocrystalline
have been deliberately edge shaped.
Gallium Arsenide Slices
1.2 Two test methods are described. One is destructive and
is limited to inspection of discrete points on the periphery,
3. Summary of Test Methods
including flats. The contour of deliberately edge-shaped wafers
3.1 Both test methods employ optical means to project a
may not be uniform around the entire periphery, and thus the
shadow of the edge contour at substantial magnification on a
discrete location(s) may or may not be representative of the
screen. In applying Method A (destructive) the sample wafer is
entire periphery. The other test method is nondestructive and
cleaved or broken along a diameter. A sharply focused image of
suitable for inspection of all points on the wafers periphery
the cross section of the wafer is obtained over a sufficiently
except flats.
large region near the edge with the aid of an optical comparator
1.3 The nondestructive test method may also be applied to
or projection microscope. In Method B (nondestructive) the
the examination of the edge contour of the outer periphery of
unbroken wafer is back lighted with collimated (parallel) light
substrates for rigid disks used for magnetic storage of data.
such that a sharply defined shadow of the wafer edge is
NOTE 1—Reference to wafers in the remainder of this standard shall be
projected on a screen. In this test method the wafer is not
interpreted to include substrates for rigid disks unless the phrase “of
altered in any way.
electronic materials” is also included in the context.
3.2 By either test method, the contour of the wafer edge
1.4 The values stated in SI units are to be regarded as the
profile image is compared to a template that has been mounted
standard. The values given in parentheses are for information
or projected on the screen. The template defines a permitted
only.
zone through which the edge contour must pass.
1.5 This standard does not purport to address all of the
4. Significance and Use
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4.1 The edges of circular wafers of electronic materials are
priate safety and health practices and determine the applica-
frequently required to be shaped after cutting the wafers from
bility of regulatory limitations prior to use.
the ingot. Contouring the wafer edge reduces the incidence of
chipping and minimizes epitaxial edge crown and photoresist
2. Referenced Documents
edge bead during subsequent processing of the wafer. Simi-
2.1 ASTM Standards:
larly, edges of rigid disk substrates are frequently edge shaped.
E 122 Practice for Choice of Sample Size to Estimate a
4.2 The test methods described here provide means to
determine that the wafer edge contour is appropriate to meet
specifications, such as SEMI M1 or SEMI M9, which are
These test methods are under the jurisdiction of ASTM Committee F-1 on
intended to provide wafers avoiding the difficulties enumerated
Electronics and are the direct responsibility of Subcommittee F01.06 on Silicon
Materials and Process Control.
above.
Current edition approved Aug. 15, 1993. Published October 1993. Originally
published as F 928 – 85. Last previous edition F 928 – 92.
DIN 50441/2 is equivalent to Method B of this standard. It is the responsibility 3
Annual Book of ASTM Standards, Vol 14.02.
of DIN Committee NMP 221 with which Committee F-1 maintains close technical 4
Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700
liaison. DIN 50441/2, Measurement of the Geometric Dimensions of Semiconductor
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Slices; Testing of Edge Rounding, is available from Beuth Verlag GmbH, Burg- 5
Available from the Semiconductor Equipment and Materials International, 805
grafenstrasse 4-10, D-1000 Berlin 30, FRG.
East Middlefield Road, Mountain View, CA 94043.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
F 928
4.3 Method A is recommended for examining the edge lenses to give 1003 magnification and TV monitor capable of
profile of flatted regions of the wafer. displayinga1by 1-mm (0.04 by 0.04-in.) area.
4.4 Method A is best suited for referee purposes. Method B
NOTE 2—An adjustable camera mount, slice holding fixture, or lens
is appropriate for routine process monitoring such as alignment
adjustment is desirable for sharp focusing.
of wafer edge grinders, routine quality control and incoming/
6.3 Fixture, for holding the wafer to be tested. The fixture
outgoing inspection purposes. In view of the uncertainty of
must provide means for positioning the wafer such that the
precisely locating the intersection of the contour and the wafer
plane of the surface of the wafer is parallel to the viewing
surface when carrying out Method B, use of this method for
direction. The fixture should be arranged in such a way that its
commercial transactions is not recommended unless the parties
position and orientation in a plan perpendicular to the viewing
to the test establish the degree of correlation that can be
direction can be adjusted conveniently, or alternatively, the
obtained.
template can be moved. Optionally, for Method B, the fixture
4.5 Method B is suitable for examining the outer circum-
can provide means for rotation of the wafer about its axis of
ference or rigid disk substrates; metallic rigid disk substrates
symmetry. The design of the fixture for Method B should be
cannot conveniently be cleaved.
such that the wafer may be loaded, held in position, and
5. Interferences unloaded with minimum risk of contamination or damage to
the wafer.
5.1 In Method B, the profile of the parallel surfaces of the
6.4 Template, having transparent regions defining the area
wafer may not be sharply focused at distances exceeding
through which the contour of the edge of the wafer must pass
approximately 0.5 mm (0.020 in.) from the extreme wafer edge
and a semi-transparent region bounding the space. An example
toward the wafer center. This uncertainty in the wafer surface
of a template is given in Fig. 1. Instructions for constructing
location may cause inaccuracy in positioning the wafer with
templates are given in Section 10.
respect to template lines. It may also make it difficult to
6.5 Gage Block or Precision Rod, with dimensions approxi-
determine whether the wafer edge profile lies within the
mately the same as the thickness of the wafer to be tested and
permitted zone at point B of the template. These difficulties can
accurately known for use in establishing the magnification of
be overcome by aligning a straight edge to the wafer surface by
the apparatus.
direct contact, observing the shadow extension in the sharply
6.6 Rule, 150 mm (6 in.) long with scale gradations of 0.5
focused region, and extrapolating the straight line edge of the
mm (0.02 in.) or less.
template reference. In applying this technique, exercise care to
avoid damaging or contaminating the wafer surface.
7. Sampling
5.1.1 This limitation renders Method B unsuitable for de-
7.1 Unless otherwise specified, Practice E 122 shall be used.
termining the distance between the front and back wafer
When so specified, appropriate sample sizes shall be selected
surfaces. The edge contours near the front and back surfaces of
from each lot in accordance with MIL-STD-105D. Inspection
the wafer must be inspected separately.
levels shall be agreed upon between the supplier and purchaser.
5.2 In Method B, attempting to view the complete wafer
7.2 The number and location of the test points on the
periphery, except flats, through wafer rotation necessitates
periphery of each wafer shall be agreed upon between the
frequent focus adjustment due to variations in wafer roundness
supplier and purchaser.
and fixturing precision, including wafer centering.
5.3 By either test method, any foreign material such as large
8. Specimen Preparation
particles or high spots on the wafer surface in the light path will
present a false edge contour by masking the true contour shape. 8.1 For Method A, cleave or fracture the wafer along a
diameter.
5.4 It is not always feasible to provide a uniform radius or
bevel to the edges of wafers because silicon, gallium arsenide,
NOTE 3—This may be conveniently accomplished by positioning the
and many other electronic materials as well as glass disk
wafer over a small diameter rod and pressing downward on both sides.
substrates are both hard and brittle. Wear of grinding tools,
(Alignment by eye is sufficient.) If required by the sampling plan, cleave
process variations, and the presence o
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