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SEMI MF847-0705 © SEMI 2003, 2005 1 SEMI MF847-0705 TEST METHODS FO R MEASURING CRYSTALLOGRAPHIC ORIENTATION OF FLATS ON SING LE CRYSTAL SILICON WAFERS BY X-RAY TECHNIQUES These test methods were techni cal ly approved b…

SEMI MF928-0305 © SEMI 2005 6

14 Keywords

Contour; edge contour; gallium arsenide; optical comparator; projection microscope; rigid disk; semiconductor;

silicon; wafer

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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).

SEMI MF847-0705 © SEMI 2003, 2005 2

2.5 The values stated in SI units are to be regarded as the standard. The inch-pound values given in parentheses are

for information only.

NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the

responsibility of the user of this standard to establish appropriate safety and health guides and determine the

applicability of regulatory or other limitations prior to use.

3 Limitations

3.1 The alignment of the flat against the reference fence may be affected by the straightness of the flat. In the

unlikely event that the flat profile is convex, the flat orientation may not be unique. More often the flat surface will

touch the reference fence along two lines perpendicular to the wafer surface at two points. In this case, the

orientation determined is that of the plane through the two lines on the plane perpendicular to the wafer surface that

passes through the two points. In the latter cases, the orientation determined is that which is obtained in subsequent

processing of the wafer when the alignment is between the flat and a reference fence.

3.2 Misalignment of the various fixtures degrades both the interlaboratory reproducibility and the absolute accuracy

of both test methods. The single-instrument repeatability is not degraded provided the fixturing is rigid.

4 Referenced Standards and Documents

4.1 SEMI Standards

SEMI M1 — Specifications for Polished Monocrystalline Silicon Wafers

SEMI M59 — Terminology for Silicon Technology

SEMI MF26 — Test Methods for Determining the Orientation of a Semiconductive Single Crystal

4.2 ASTM Standards

E 82 — Test Method for Determining the Orientation of a Metal Crystal

E 122 — Practice for Choice of Sample Size to Estimate a Measure of Quality for a Lot or Process

4.3 DIN Standard

50433, Part 3 — Determination of the Orientation of Single Crystals by Means of Laue Back Scattering

4.4 ANSI Standard

ANSI/ASQC Z1.4 — Sampling Procedures and Tables for Inspection by Attributes

4.5 Other Standard

Code of Federal Regulations, Title 10, Part 20, Standards for Protection Against Radiation

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 technology are defined in SEMI M59.

3 Annual Book of ASTM Standards, Vol 03.01, ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. Telephone: 610-

832-9500, Fax: 610-832-9555, Website:

www.astm.org.

4 Annual Book of ASTM Standards, Vol 14.02.

5 Deutches Institut für Normung 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.

6 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

7 Published in Federal Register, Nov. 16, 1960. Available from Superintendent of Documents, U.S. Government Printing Office, Washington,

DC 20402.