LiNbO3 Single Crystal Layer Transfer Techniques for High Performances RF Filters

Abstract

In this paper we present the realization of engineered substrates based on thin single crystal piezoelectric layers. Their potential interest for next generation of ultra wide band RF filters has been demonstrated. For this purpose we propose two different methods to transfer a thin monocrystalline layer: the Smart Cut{trade mark, serif} technology and a "bond and etch back" technology. Lithium Niobate (LiNbO3) has been chosen for its high electromechanical coupling factor of about 45% for bulk acoustic waves but also for its availability as single crystal wafers diameters up to 6 inches. Engineered substrate process, material and electrical characterizations are presented. The first objective of this study is to demonstrate LiNbO3 piezoelectric property preservation after processes whatever the used technology. High overtone Bulk Acoustic Resonators have been used as test vehicles to characterize these layers so as to evaluate layer transfer achievement of sub micron single crystal LiNbO3.