This guide defines standardized positions for measuring diameter of circular wafers of silicon and other semiconducting materials that contain flats or notches (fiducials) on the periphery. It was developed for use with silicon wafers with standard diameter and fiducial positions as given in SEMI M1.

It may be applied to other semiconductor wafers if the flat locations are properly taken into account.

No recommendations are given regarding the test instrumentation to be used, but either contacting (taking suitable precautions to avoid edge chipping) or non-contacting gauges have been found to be satisfactory. Wafers of any size can be measured provided that suitable test jigs and instruments are available.

Roundness of wafers cannot be determined from measurements made solely at the positions defined in this guide. No information is provided concerning the diameter of the wafer at points other than those measured.

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 practices and determine the applicability of regulatory or other limitations prior to use.

The diameter of semiconductor wafers is an important parameter in microelectronic fabrication. Wafer diameters must conform to the limits specified in SEMI M1; or other agreed upon limits, or product that is otherwise suitable may not fit correctly in process equipment.

Cam-follower edge rounding usually results in wafers that are circular. However, wafers ground with edgefollower edge rounding equipment may be elliptically shaped. Measurements made at the three positions specified in this guide do not provide complete information about the roundness of the wafer.