Overview

This International Standard applies to the manufacture of synthetic quartz, lithium niobate (LN), lithium tantalate (LT), lithium tetraborate (LBO), and lanthanum gallium silicate (LGS) single crystal wafers intended for use as substrates in the manufacture of surface acoustic wave (SAW) filters and resonators. A variety of piezoelectric materials are used for surface acoustic wave (SAW) filters and resonators. Prior to the 1996 Rotterdam IEC/TC 49 meeting, wafer specifications were typically negotiated between users and suppliers. This standard has been prepared in order to provide industry standard technical specifications for manufacturing piezoelectric single crystal wafers to be used in surface acoustic wave devices. Clause 3 of the standard introduces the necessary terms and definitions. Additional clauses dealing with the requirements, the sampling plan, and the test methods follow. Clause 7 contains information regarding identification, labelling, packaging and delivery conditions. Extensive information regarding measurement of Curie temperature, measurement of lattice constant (Bond method), measurement of face angle by X-ray, measurement of volume resistivity and appearance inspections are provided in additional clauses. Normative Annex A includes information for piezoelectric single crystals using Euler angle description. Material properties of piezoelectric single crystals, such as piezoelectric constants, elastic constants and dielectric constants have been generally determined in terms of the rectangular axes (X,Y,Z) which have been defined in place of the crystal axes. Wafer cuts used for manufacture of SAW equipment are generally circular cuts. The description of the Euler angles represents a possibility to describe the crystal orientation of the perpendicular with respect to the wafer surface and the direction of orientation flat corresponding with the SAW wave propagation. Informative Annex B describes manufacturing processes for SAW wafers. The first clause introduces crystal growth methods. When using the Czochralski method single crystals are grown by dipping a seed crystal into the melt in a crucible. While the crystal and/or crucible are/is rotated, the seed crystal is pulled up slowly and, after it has cooled from the melt and becomes solid, is formed into a single crystal. This method is named after the Polish developer, Jan Czochralski, who used it in 1916 for the first time to manufacture single crystals from metals. Industrial mass production using this method began with single crystals from germanium (Ge) und silicon (Si). The first crystals from LN and LT were manufactured in 1965 by the Bell telephone lab and in laboratories in the former Soviet Union. While there are r.f. induction heating and resistance heating as the heating method, regarding LN, LT and LGS, single crystals are grown generally by r.f. induction heating method. The following starting materials are generally provided: pulverised Li₂Co₃ and Nb₂O₅ (Ta₂O₅) with a Li/Nb-(Li/Ta-) mole ratio of 0,93 to 0,95 are mixed and calcinated after press forming. The polycrystalline ceramic obtained from LN (LT) is placed in a crucible and melted by heating the crucible. For LGS the starting materials are obtained by mixing La₂O₃, Ga₂O₃ and SiO₂ at a stoichiometric ratio. The mixture is pressed into pellets and annealed for several hours at temperatures of above 1 200 °C. The obtained polycrystalline LGS is used in an identical manner to LN or LT. The responsible committee is DKE/K 642 "Piezoelektrische Bauteile zur Frequenzstabilisierung und -selektion" ("Piezoelectric and dielectric devices for frequency control and selection") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.

Responsible national committee

DKE/K 642 - Piezoelektrische Bauteile zur Frequenzstabilisierung und -selektion