ASTM F847-94(1999)

1.1 These test methods cover the determination of [alpha], 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.

1.2 These test methods are applicable for wafers with flat length values in the range of those specified for silicon wafers in SEMI Specification M1. They are suitable for use only on wafers with angular deviations of less than +5°.

1.3 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.

1.4 Two test methods are covered as follows:

Sections Test Method A---X-Ray Edge Diffraction 8 to 13 Method Test Method B---Laue Back Reflection 14 to 18 X-Ray Method

1.4.1 Test Method A is nondestructive and is similar to Test Method A of Test Methods F26 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.

1.4.2 Test Method B is also nondestructive, and is similar to Test Method E82, 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 Test Method E82 and to DIN 50 433, Part 3, or to a standard X-ray textbook. With different wafer holding fixturing, Test Method B is also applicable to determination of the orientation of a wafer surface.

1.5 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.

1.6 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. For specific hazard statements see Section 6.