RF Filter using Boundary Acoustic Wave

Abstract

In this paper, we report a new structure of a shear horizontal (SH) type boundary acoustic wave for cellular phone applications. Such a structure composed of electrodes with a low shear wave velocity between two materials, namely, the SiO 2 film/Au-electrode/LiNbO 3 substrate, is proposed. The ladder filter used in this paper had this structure. By changing the propagation angle of the acoustic wave, the electromechanical coupling factor k 2 range from 0 to 16% was obtained, as well as a normalized bandwidth range 0.67 to 1.85 fold as large as that of a 36 -46 Y-X LiTaO 3 leaky surface acoustic wave (LT-LSAW) filter. In addition, an excellent temperature coefficient of delay time (TCD ¼ 25 ppm/ C) and a large mutual coupling coefficient 12 (¼ 0:15) were also obtained.

Wafer-level packaged SAW filters with resistance to transfer molding

“…In order to move forward in miniaturization, particularly toward lower profiles, a variety of wafer-level packaging (WLP) technologies have been applied to the packaging of SAW filters [2,3,4]. WLP technology reported in [2] is based on through-wafer interconnection and wafer-to-wafer bonding techniques, and the technology in [3] makes a hollow space in the piezoelectric substrate utilizing the sacrificial layer.…”

“…WLP technology reported in [2] is based on through-wafer interconnection and wafer-to-wafer bonding techniques, and the technology in [3] makes a hollow space in the piezoelectric substrate utilizing the sacrificial layer. The approach in [4] uses boundary acoustic wave to realize filters which operate without the hollow space on the surface.…”

6E-5 High Performance and Miniature Surface Acoustic Wave Devices with Excellent Temperature Stability Using High Density Metal Electrodes

“…To realize them, SAW substrates combining a high density metal electrode and a piezoelectric substrate have been investigated. The author has succeeded in exciting various SAWs having large electromechanical coupling factor, large reflection coefficient, and excellent temperature stability, by combining high density metal electrode such as tantalum (Ta), copper (Cu), and gold (Au) and the various substrates [2][3] [4][5] [6] [7][8] [9][10] [11] [12].By applying their features, following various miniature SAW devices such as IF filters, duplexers, and RF filters with good temperature stability and good frequency characteristics were developed.…”

“…(4) RF filtrs without cavity on the chip surface using a elastic boundary wave (EBW) between thick SiO 2 (high velocity)/thin Au electrode (low one)/0∼15 • YXLiNbO 3 substrate (high one) structure [11] [12].…”

P3I-2 Cavityless Wafer Level Packaging of SAW Devices

“…Alternative concepts based on boundary and interface waves that do not require cavity are known and they have shown useful performance of devices. These approaches make use of acoustic waves that are confined near internal interfaces in solids like Stonely [1], Sezawa [2], MaerfeldTournois [3] and boundary waves [4], [5], [6] and [7].…”