Prime Wafer Geometry Improvement during Haze-free Polishing with Peter Wolters Polishing Head “M-Carrier”

Abstract:
Two different thickness geometry properties of prime wafers are of major interest to the wafermakers – the total thickness variation and the local site flatness. In order to improve these wafer thickness geometry parameters with prime wafer CMP, it is necessary to control the silicon removal profile in a wide range. This control requires the knowledge of the incoming wafer’s geometry and a suitable polishing head technology: We present a way to improve the wafer thickness geometry with prime wafer CMP and discuss the results of test polishing with two different Peter Wolters polishing carriers for the CMP removal step and incoming wafers with significantly different geometry in detail. As a result, the flexible hard-platen polishing head Z-Carrier can help to improve the total thickness variation of 300 mm silicon wafers with a convex thickness diameter profile. Additionally, both the total thickness variation and the site flatness can be improved for wafers with quite different thickness geometries by use of the M-Carrier. Its membrane technology allows the variation and control of the silicon removal profile during CMP, especially at the wafer edge.