Method for the preparation of a ferroelectric substrate plate

Abstract

The invention provides a method for surface-finishing of a single crystal wafer of a ferroelectric material into a substrate plate suitable for use, for example, as a SAW filter element which is mirror-polished only on one of the surfaces, the other surface having an adequate roughness. Different from conventional methods, the inventive method comprises the successive steps of (a) slicing a single crystal boule into wafers, (b) lapping of the wafer on both surfaces to impart adequate roughness to the surfaces, (c) chemically etching the thus lapped surfaces to remove the strain produced in the preceding mechanical working, and (d) mirror-polishing one of the thus etched surfaces so that high uniformity of the thickness and greatly decreased warping of the wafer can be ensured.

Dependencies are inferred from the claim text.