scope:

1. Scope

1.1 This test method covers a noncontacting, nondestructive procedure to determine the warp and total thickness variation (TTV) of clean, dry silicon wafers in a free (unclamped) condition. The procedure uses a three-point back surface reference plane for determining warp.

1.2 The test method is applicable to circular silicon wafers 50 mm or larger in diameter, and 100 µm (0.004 in. approximately) and larger in thickness, independent of thickness variation and surface finish. The test method is applicable to wafers of semiconductors other than silicon with these same physical characteristics.

1.3 This test method is not intended to measure surface flatness; warp, which is not to be confused with flatness, is a bulk property of the wafer.

1.4 This test method measures warp or TTV of a wafer with no mechanical force applied during the test. Therefore, the procedure described gives the unconstrained value of warp or TTV. Gravity-induced deflection alters the shape of the wafer and is included in the measurement.

1.5 For silicon wafers of diameter 3 in. or smaller, the values stated in inch-pound units are to be regarded as standard; the values stated in acceptable metric units in parentheses are for information only. For silicon wafers of diameter larger than 3 in., the values stated in acceptable metric units are to be regarded as standard whether or not they appear with parentheses; inch-pound units are for information only.

1.6 This standard does not purport to address 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.