Suppression of transverse-mode spurious responses for zero temperature coefficient of frequency SAW resonator on a SiO<inf>2</inf>/Al/LiNbO<inf>3</inf> structure

Abstract

This paper describes a suppression of transverse-mode spurious responses for zero temperature coefficient of frequency (TCF) surface acoustic wave (SAW) resonator on a SiO 2 /Al/LiNbO 3 structure. We investigated to use thinning of SiO 2 on the dummy electrodes and studied how the transverse-mode responses change with remaining SiO 2 thickness h on the dummy electrode region. As the results, we could realize high performance SAW resonator with complete suppression of the transverse-mode spurious responses when h is set at 0.20λ. It was demonstrated that the selective SiO 2 removal technique is effective to suppress transverse-mode spurious responses for SAW resonators employing the SiO 2 /Al/LiNbO 3 structure for wide range of SiO 2 thicknesses, provided that the SiO 2 thickness at the dummy electrode region is adjusted properly.

Recent development of temperature compensated SAW Devices

“…The best angle in this aspect depends on the electrode and SiO 2 thicknesses, widths, shape, etc. Thus the device structure including the rotation angle must be optimized for each application [17,18]. Difference of this result from that shown in Fig.…”

“…Use of apodized IDTs is the traditional countermeasure [12,37]. Since the apodization may cause Q reduction and relatively large device size [37], various techniques were proposed as another means [17,18,38].…”

“…The TCF can be further improved to about 0 ppm/ºC by increasing the SiO 2 thickness. The above-mentioned techniques can be also applicable to the SAW resonator with zero TCF [15,18]. The techniques show promising advance for the DPX performances.…”

“…First one is based on deposition of an amorphous SiO 2 layer on interdigital transducers (IDTs) and reflectors fabricated on a traditional LN/LT substrate [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. This is based on a unique feature of SiO 2 , i.e., it becomes mechanically stiff with T, giving positive temperature coefficient of elasticity (TCE) and TCV.…”

Frequency response study of surface acoustic wave devices with SiO x N y film using LiTaO3 substrate

“…There are also previous research studies that investigated the effect of the deposited shape of the SiO 2 film on SAW device characteristics. [14][15][16][17][18][19] The reason why research studies on the SiO 2 film have been actively conducted is that the SiO 2 film has TCF whereby positive and negative are different from those of the substrate materials. Therefore, when it is necessary to improve the TCF of the SAW devices, the SiO 2 film for passivation is better than the Si 3 N 4 film, which has the same sign of TCF as the substrate materials.…”