TRANSDUCER ELEMENTS WITH A SEMICONDUCTOR CAVITY AND PIEZOELECTRIC FILM
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-08
The term "transducer" applies to any piezoelec- tric devices which perform the transformation of electric energy to mechanical energy or vice versa. One example of such a transducer is the piezoelec- tric 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 electrodes contacting the diaphragm. The diaphragm includes an etch-stop layer for easy fab- rication 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 nucle- ation layer requires a planar, smooth and dense sur- face. Silicon dioxide formed by thermal oxidation of Si or silicon nitride formed by chemical deposi- tion method can serve as a good etch stop and nucleation layer, Figure 1 shows an example of the thin film piezoelectric transducer consisting of these three elements. diaphragm An advantage of this transducer structure is that it can be integrated with semiconductor devices built on the same substrate. Another integration option is by flip-chip bonding of the transducer to a semiconductor device on another substrate.