Acoustic isolator having a high impedance layer of hafnium oxide

Details Acoustic isolator having a high impedance layer of hafnium oxide Acoustic isolator having a high impedance layer of hafnium oxide

1996-01-04

1997-07-08

Lee, Benny T.

Wave transmission lines and networks

Coupling networks

Electromechanical filter

310320, 333188, H03H 900

Patent

active

056465831

ABSTRACT:
A resonant acoustic isolator supports a thin film acoustic resonator comprising a layer of piezoelectric material having top and bottom electrical contacts. The resonant acoustic isolator comprises at least one pair of layers of materials having different acoustic impedances. The isolator materials are deposited in alternating layers of high and low impedance material, with each layer having a thickness of 1/4 acoustic wavelength at resonant frequency. Silicon dioxide (SiO.sub.2) is preferred for the low impedance material because it is ubiquitous in the semiconductor industry, it has relatively low acoustic impedance with very low intrinsic acoustic loss, and it can be deposited using a variety of convenient methods. Hafnium oxide (HfO.sub.2) is preferred for the high acoustic impedance material because it can be deposited by evaporation to form a hard, dense dielectric having a relatively high acoustic impedance. Deposition of an entire stack of alternating SiO.sub.2 and HfO.sub.2 layers can be performed in the same chamber using electron beam deposition techniques for low cost production.

REFERENCES:
patent: 3767579 (1973-10-01), Tsubouchi et al.
patent: 5373268 (1994-12-01), Dworsky et al.
K.M. Laken, G.R. Kline, K.T. McCarron, "Development of Miniature Filters for Wireless Applications," IEEE, WE4A-1, pp. 883-886 (1995).
W.E. Newell, "Face-Mounted Piezoelectric Resonators," IEEE, vol. 53, pp. 575-581, Jun. 1965.

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