SELF-SUPPORTING DIAMOND WATER AND ITS PRODUCTION

摘要

PURPOSE: To obtain a self-supporting diamond wafer suitable for a window, capable of providing a piezoelectric film for surface elastic wave element and an electrode finely and in high accuracy, having improved light transmission, by removing a substrate from a diamond film formed by a vapor-phase synthesis method to give a wafer and specifying its face roughness and shape. CONSTITUTION: A substrate (e.g. a polycrystalline Si wafer subjected to mirror polishing) is removed from a diamond film applied to the substrate by a vapor- phase synthetic method to give a diamond wafer. The face roughness of at least one face of the wafer is equal to or lower than Rmax 500Åand equal to or lower than Ra 200Å. The wafer is a disc having >=2 inch or has a rectangular shape with the same area as that of the disc and is warped monotonously from the outer periphery to the inner periphery. The diamond film has preferably 0.01-1.5GPa compression stress in the diamond crystal film at the projected side. The warped amount is preferably 2μm<=|ΔH|<=150μm, whenΔH is the difference in height between the outer periphery and the central part.