Tetsuyosi Ogura

A novel temperature compensation method for SAW devices using direct bonding techniques

We have developed a novel temperature compensation method for SAW devices using a direct bonding technique. The SAW device applied this method was composed of a conventional piezoelectric substrate such as LiTaO/sub 3/ and LiNbO/sub 3/, directly bonded without any bonding agents to a glass substrate having a relatively low thermal expansion coefficient (TEC). The piezoelectric substrate and the glass substrate were bonded in an atomic scale and the interface was very uniform. Therefore, the thermal strain at the surface of the bonded substrate caused by the difference between the TECs of the substrates was quite uniform and stable. With this structure, the thermal expansion of the piezoelectric substrate was restrained and the elastic constant of the piezoelectric substrate was changed by the thermal strain. Using this technique, we have succeeded to improve the temperature coefficient of frequency (TCF) of the SAW devices without causing any deterioration in the frequency response. This novel temperature compensation method is very promising for RF-SAW device applications.

Shock sensors using direct bonding of LiNbO/sub 3/ crystals

We have developed a shock sensor made with a bimorph type cantilever using by a technique of directly bonding piezoelectric single crystals. The cantilevers polarization-inverted structure was achieved by directly bonding LiNbO/sub 3/ single-crystal wafers having reverse polarization. This technique did not require any bonding agent. The basic characteristics of the shock sensor were evaluated. The resonance frequency of the cantilever having a length of 2 mm was 20 kHz. The sensor made from 140/spl deg/ rotated Y cut LiNbO/sub 3/ wafers had a high sensitivity of 6.4 mV/G, and excellent linearity.