Surface acoustic wave device

Abstract

Abstract A surface acoustic wave device (10, 12) having a lithium tetraborate single crystal substrate (11, 21) is proposed. An electro-mechanical coupling coefficient K² of the substrate is about 1% so as to obtain a surface acoustic wave having sufficient practical energy. When cut angles of the substrate and a propagation direction of the surface acoustic wave are expressed by Eulerian angles (90+λ, 90°, 90°), a thickness t of an electrode (12, 13, 22, 23, 24) formed on the substrate falls within a region bounded by a dotted curve and an alternate long and short dash curve in Figure 8. The dotted curve and the alternate long and short dash curve indicate the experimental relationship between the cut angle λ and the thickness t when the TCD is set at 5 and -5 ppm/°C, respectively. When the film thickness t is set within the above-mentioned range, the absolute value of the TCD is set at 5 ppm/°C or less. When the cut angle is 25°, the TCD of the substrate becomes zero. Therefore, using the substrate having the above cut angle, the TCD becomes zero or almost zero in the electrode region and nonelectrode region of the surface of the substrate.

Inventors

• 👤 Yasuo Ebata
• 👤 Hitoshi Suzuki
• 👤 Sadao Matsumura
• 👤 Katsuyoshi Fukuta

Bibliographic Details