- SEMI MF928 - Test Method for Edge Contour of Circular Semiconductor Wafers and Rigid Disk Substrates
This Standard was technically approved by the Silicon Wafer Global Technical Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on February 2, 2017. Available at www.semiviews.org and www.semi.org in March 2017; originally published by ASTM International as ASTM F928-85; previously published October 2014.
The edges of circular wafers of electronic materials are frequently required to be shaped after cutting the wafers from the ingot. Contouring the wafer edge reduces the incidence of chipping and minimizes epitaxial edge crown and photoresist edge bead during subsequent processing of the wafer. Similarly, edges of rigid disk substrates are frequently edge shaped.<br>This Test Method described here provide means to determine that the wafer edge contour is appropriate to meet template-coordinate based edge profile specifications, such as SEMI M1 or SEMI M9, which are intended to provide wafers avoiding the difficulties enumerated above.
This Test Method provides a means for examining the edge contour of circular wafers of silicon, gallium arsenide, and other electronic materials, and determining fit to limits of contour specified by a template-coordinate based edge profile template that defines a permitted zone through which the contour must pass. Principal application of such a template is intended for, but not limited to, wafers that have been deliberately edge shaped.<br>Because this Test Method does not provide quantitative output data, required for statistical process control systems, it is generally employed only for wafers of 200 mm diameter or less.<br>Two test methods are described:<br>Method A is destructive and is limited to inspection of discrete points on the periphery, including flats. The contour of deliberately edge-shaped wafers may not be uniform around the entire periphery, and thus the discrete location(s) may or may not be representative of the entire periphery.<br>Method A is recommended for examining the edge profile of flatted regions of the wafer.<br>Method A is best suited for referee purposes.<br>Method B is nondestructive and suitable for inspection of all points on the wafer periphery except flats or notches.<br>Method B is appropriate for routine process monitoring such as alignment of wafer edge grinders, routine quality control and incoming/outgoing inspection purposes. In view of the uncertainty of precisely locating the intersection of the contour and the wafer surface when carrying out Method B, use of this method for commercial transactions is not recommended unless the parties to the test establish the degree of correlation that can be obtained.<br>Method B may also be applied to the examination of the edge contour of the outer periphery of substrates for rigid disks used for magnetic storage of data; metallic rigid disk substrates cannot conveniently be cleaved.<br>The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
Referenced SEMI Standards
SEMI M1 — Specifications for Polished Single Crystal Silicon Wafers
SEMI M9 — Specification for Polished Monocrystalline Gallium Arsenide Wafers