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SEMI MF928-0305 © SEMI 2005 6 14 Keywords Contour; edge contour; gallium arsenide; optical co mparator; projection microscope; rigid disk; semiconductor; silicon; wafer NOTICE: SEMI makes no warranties or represen tation…
SEMI MF928-0305 © SEMI 2005 5
specimen. Adjust wafer or template position and focus as required to assure proper judgment of template fit.
Repeat ¶11.2.3 and ¶11.2.4 at specified points in accordance with the sampling plan.
NOTE 6: Flatted regions of the wafer periphery cannot be evaluated by this test method.
11.2.6 Repeat ¶11.2.3 through ¶11.2.5 with the opposite side of the contour profile image tangent to the overlay
template at both the edge and the back surface.
11.2.7 Record as “passed” those wafers for which all edge contours examined lie entirely within the permitted zone
and which meet all other specification requirements.
12 Report
12.1 Report as a minimum the following information:
12.1.1 Date of test,
12.1.2 Name of person conducting the test,
12.1.3 The lot number of other identification of the material,
12.1.4 Method used, A or B,
12.1.5 Position(s) on the wafer periphery that were examined,
12.1.6 The number of wafers in the lot,
12.1.7 The number of test wafers, and
12.1.8 The number of accepted wafers.
13 Precision and Bias
13.1 Although these test methods do not return a test result, an interlaboratory test was conducted to determine the
reliability of the nondestructive Method B when applied to silicon wafers. In this test, a lot of 25, 125 mm diameter,
edge profiled, silicon wafers was tested in accordance with Method B against the edge contour template and other
requirements of SEMI M1. The wafers were measured by nine different organizations using several types of
commercially available edge contour measuring instruments, all of which had similar optical systems. In one case
the magnification used was 60× instead of 100× as specified in ¶6.2.
13.1.1 In no case was a wafer judged to be within the specification requirements by all participants. Only three
wafers were judged by all participants to fail, but different participants reported different reasons for failure; the
other 22 wafers were judged to pass by some and to fail by others, but again the same failure mode was not always
reported. Most of the difficulty centered around determination of whether or not the edge profile extended further
into the wafer than 0.508 mm (the specified location of point B in the SEMI template). Some participants reported
failure on the front of the wafer, some on the back, and some reported that failure occurred because the contour
passed inside point C. These results confirm the difficulties with locating the wafer surface indicated in ¶3.1. No
participant reported use of the straight-edge technique suggested in ¶3.1, so the efficacy of that procedure was not
evaluated in the test.
13.1.2 The results also confirmed the difficulties with interference from particulate contaminants. Several
observers reported protrusions or sharp points on the wafer periphery, but these were not generally reported.
Examination of the wafers under conditions in which the edge of the wafer could be accessed during the test showed
that such apparent protrusions could be removed by blowing or wiping with lens cleaning tissue.
13.1.3 For more details, refer to the Research Report.
2
13.2 At the recommended magnification, 100×, a dimension of 25 m (0.001 in.) at the object plane produces a
screen image of 2.5 mm (0.1 in.). The smallest size details of edge contours to be inspected by these test methods
are of comparable dimensions.
2 Available on request from SEMI Headquarters, 3081 Zanker Road, San Jose, CA, Telephone 408-943-7021, Fax: 408-943-7015, e-mail:
standards@semi.org. Request International Standards Research Report MF0928.
SEMI MF928-0305 © SEMI 2005 6
14 Keywords
Contour; edge contour; gallium arsenide; optical comparator; projection microscope; rigid disk; semiconductor;
silicon; wafer
NOTICE: SEMI makes no warranties or representations as to the suitability of the standards set forth herein for any
particular application. The determination of the suitability of the standard is solely the responsibility of the user.
Users are cautioned to refer to manufacturer's instructions, product labels, product data sheets, and other relevant
literature, respecting any materials or equipment mentioned herein. These standards are subject to change without
notice.
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respecting the validity of any patent rights or copyrights asserted in connection with any items mentioned in this
standard. Users of this standard are expressly advised that determination of any such patent rights or copyrights, and
the risk of infringement of such rights are entirely their own responsibility.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction of
the contents in whole or in part is forbidden without express written
consent of SEMI.
SEMI MF847-0705 © SEMI 2003, 2005 1
SEMI MF847-0705
TEST METHODS FOR MEASURING CRYSTALLOGRAPHIC
ORIENTATION OF FLATS ON SINGLE CRYSTAL SILICON WAFERS
BY X-RAY TECHNIQUES
These test methods were technically approved by the global Silicon Wafer Committee. This edition was
approved for publication by the global Audits and Reviews Subcommittee on April 7, 2005. It was available
at www.semi.org in June 2005 and on CD-ROM in July 2005. Original edition published by ASTM
International as ASTM F 847-83. Last previous edition SEMI MF847-02.
1 Purpose
1.1 The orientation of flats on silicon wafers is an important materials acceptance requirement. The flats are used in
semiconductor device processing to provide consistent alignment of device geometries with respect to
crystallographic planes and directions.
1.2 The orientation of a wafer flat is the orientation of the surface of the flat (on the edge of the wafer). Flats are
usually specified with respect to a low-index plane, such as a (110) plane. In such cases the orientation of the flat
may be described in terms of its angular deviation from the low-index plane.
1.3 This standard covers two test methods for determining flat orientation.
1.4 Either one of these test methods is appropriate for process development and quality assurance applications.
Until the interlaboratory precision of these test methods has been determined, it is not recommended that they be
used between supplier and customer unless correlation studies are completed satisfactorily.
2 Scope
2.1 These test methods cover the determination of
, the angular deviation between the crystallographic orientation
of the direction perpendicular to the plane of a fiducial flat on a circular silicon wafer, and the specified orientation
of the flat in the plane of the wafer surface.
2.2 These test methods are applicable for wafers with flat length values in the range of those specified for silicon
wafers in SEMI M1. They are suitable for use only on wafers with angular deviations in the range from 5 to +5°.
2.3 The orientation accuracy achieved by these test methods depends directly on the accuracy with which the flat
surface can be aligned with a reference fence and the accuracy of the orientation of the reference fence with respect
to the X-ray beam.
2.4 Two test methods are covered as follows:
Test Method A — X-Ray Edge Diffraction Method §8 through §13
Test Method B — Laue Back Reflection X-Ray Method §14 through §18
2.4.1 Test Method A is nondestructive and is similar to Test Method A of SEMI MF26, except that it uses special
wafer holding fixtures to orient the wafer uniquely with respect to the X-ray goniometer. The technique is capable
of measuring the crystallographic direction of flats to a greater precision than the Laue back reflection method.
2.4.2 Test Method B is also nondestructive, and is similar to ASTM Test Method E 82, and to DIN 50 433, Part 3,
except that it uses “instant” film and special fixturing to orient the flat with respect to the X-ray beam. Although it
is simpler and more rapid, it does not have the precision of Test Method A because it uses less precise and less
expensive fixturing and equipment. It produces a permanent film record of the test.
NOTE 1: The Laue photograph may be interpreted to provide information regarding the crystallographic directions of wafer
misorientation; however, this is beyond the scope of the present test method. Users desiring to carry out such interpretation
should refer to ASTM Test Method E 82, to DIN 50 433, Part 3, or to a standard X-ray textbook.
1,2
With different wafer holding
fixturing, Test Method B is also applicable to determination of the orientation of a wafer surface.
1 Wood, E. A., Crystal Orientation Manual, (Columbia University Press, New York, NY, 1963).
2 Barret, C. S., and Massalski, T. B., The Structure of Metals, 3rd edition (McGraw-Hill, New York, NY, 1966).