TRANSDUCER ELEMENTS WITH A SEMICONDUCTOR CAVITY AND PIEZOELECTRIC FILM
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2002-Apr-22
The term "transducer" applies to any piezoelec- tric devices which perform the transformation of elec- tric energy to mechanical energy or vice versa. One example of such a transducer is the piezoelectric thin film resonator which can be potentially used as RF filters, IF filters, chemical sensors, and pressure sensors. The fundamental elements of the transducer are proposed. These transducer elements are (1) a semiconductor cavity, (2) a suspended diaphragm consisting of a piezoelectric film, and (3) metal elec- trodes contacting the diaphragm. The diaphragm includes an etch-stop layer for easy fabrication of the semiconductor cavity. The etch-stop layer also serves as a nucleation layer for preferred orientation grain growth of the piezoelectric film (eg.AlN ) by the sputter deposition. A good nucleation layer requires a planar, smooth and dense surface. Silicon dioxide formed by thermal oxidation of Si or silicon nitride formed by chemical deposition method can serve as a good etch stop and nucleation layer. Fig- ure 1 shows an example of the thin film piezoelec- tric transducer consisting ofthese three elements.