Masato Sugimoto

DIRECT BONDING OF LINBO3 SINGLE CRYSTALS FOR OPTICAL WAVEGUIDES

A new fabrication method of optical waveguides using direct bonding of lithium niobate single crystals without using any bonding agents has been developed. The bonded interface was found very uniform and the bonding was performed in an atomic scale in spite of a relatively low heat‐treatment temperature of 400 °C. It was confirmed to be possible to fabricate optical waveguides using the direct bonding. This method is very attractive to obtain high‐performance optical guided‐wave devices because of its versatility.

Direct bonding of piezoelectric crystal onto silicon

A method for bonding a piezoelectric crystal directly onto silicon, without any bonding agents, is reported. The interface microstructure, procedures of fabricating a lithium tantalate (LiTaO3■‐ on‐silicon resonator, and its resonant characteristics are described. This technique is very promising for miniaturizing electroacoustic integrated devices.

Novel composite piezoelectric materials using direct bonding techniques

Novel composite piezoelectric materials for new piezoelectric devices are reported. The fabrication process using direct bonding techniques, bonded interface microstructures, and usefulness for piezoelectric devices are also reported. Monocrystalline piezoelectric materials such as LiNbO/sub 3/ and LiTaO/sub 3/ were successfully bonded directly onto the same material or different materials including semiconductor, without using any adhesive or such, effecting physically and electro-acoustically optically satisfactory interfaces. Despite the relatively low temperature of the heat treatment, the interface was found uniform, virtually void-free, and to be accomplished in an atomic order by TEM observation. Applications to one-chip electro-acoustic ICs and optical guided wave devices are described.

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.

Direct heterobonding of lithium niobate onto lithium tantalate

A new method to bond directly different electro‐optic materials (lithium niobate on lithium tantalate) for fabricating an optical waveguide is reported. Its fabrication process, interface microstructure, and usefulness for optical devices are also related.

Direct Bonding of LiTaO3 Single Crystals.

A new fabrication method for combining lithium tantalate single crystals by direct bonding without using bonding agents has been developed. The bonded interface was found to be very uniform, and bonding on an atomic scale was achieved in spite of a relatively low heat-treatment temperature of 350°C. This method is very promising for realizing new stacked structures and new fabrication processes for piezoelectric and electrooptic devices, such for a layer of ferroelectric single crystal on insulator or semiconductor.

Variable property crystal resonators by direct bonding techniques

Novel single-crystal bulk acoustic wave (BAW) resonators have been developed. These resonators realize desired electrical properties by directly bonding piezoelectric single crystals such as LiNbO/sub 3/ and LiTaO/sub 3/. The direct bonding technique fabricates composite piezoelectric substrates with new electrical properties depend on the combination of bonded wafers. For the first trial, polarization-inverted substrates have been fabricated by directly bonding two wafers of Z-cut LiNbO/sub 3/ single crystals having opposite polarization-direction. Second overtone resonators using these substrates provide excellent performance. Typically, the resonator has a high Q-value over 5,000, a figure of merit of 138, a capacitance ratio of 40, a resonant resistance of 30 /spl Omega/ and a frequency deviation of -50 ppm//spl deg/C.

Direct bonding of piezoelectric materials onto Si

New composite semiconductor-piezoelectric materials fabricated by direct bonding technology are reported. The fabrication process, analysis of the bonded interface microstructures, and their applications are also reported.

Even-order thickness-shear mode resonators using X-cut LiTaO/sub 3/ plates realized by a direct bonding technique

Even-order thickness-shear mode resonators with good temperature characteristics have been achieved by applying direct-bonding techniques to X-cut LiTaO/sub 3/ single crystals. The variations in the resonance frequency of their main fast thickness shear mode was less than 500 ppm over the temperature range of -10 to 60/spl deg/C. Moreover, the results of studies on strip type chip resonators using direct-bonded x-cut LiTaO/sub 3/ wafers suggest that fabrication of small sized resonators with no spurious response is feasible. Their typical Q-value was between 3000 and 5000, and the resonant resistance was 10-20 /spl Omega/ at 13 MHz. These values an ideal for a range of applications. We confirmed that the direct bonding technique was particularly suitable for realizing high frequency resonators because the thickness of the resonator could be double that of a conventional fundamental resonator.

New Piezoelectric Bimorph Structure Actuators with High Performances

Abstract We have developed three types of piezoelectric bimorph structure actuators. The first actuator has a displacement of over 3 mm at 100 Vpk and high reliability by resonance effect of the displacement magnifying part. The second one has a displacement of over 1 mm at 100 Vpk and high stability for change in driving frequency by combined two resonances. The third one has a linearity of displacement until 85% of fracture point and low temperature characteristics by a direct bonding technique that bonds piezoelectric single crystals without using adhesive.