High frequency surface acoustic waves excited on thin oriented LiNbO3 single crystal layers transferred onto silicon (original) (raw)
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IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
The need for high-frequency, wide-band filters has instigated many developments based on combining thin piezoelectric films and high acoustic velocity materials (sapphire, diamond-like carbon, silicon, etc.) to ease the manufacture of devices operating above 2 GHz. In the present work, a technological process has been developed to achieve thin-oriented, single-crystal lithium niobate (LiNbO3) layers deposited on (100) silicon wafers for the fabrication of radio-frequency (RF) surface acoustic wave (SAW) devices. The use of such oriented thin films is expected to favor large coupling coefficients together with a good control of the layer properties, enabling one to chose the best combination of layer orientation to optimize the device. A theoretical analysis of the elastic wave assumed to propagate on such a combination of material is first exposed. Technological aspects then are described briefly. Experimental results are presented and compared to the state of art.
Surface Acoustic Wave Devices Using Lithium Niobate on Silicon Carbide
IEEE Transactions on Microwave Theory and Techniques, 2020
This work demonstrates a group of shear horizontal (SH0) mode resonators and filters using lithium niobate (LiNbO 3) thin films on silicon carbide (SiC). The single-crystalline X-cut LiNbO 3 thin films on 4H-SiC substrates have been prepared by ion-slicing and wafer-bonding processes. The fabricated resonator has demonstrated a large effective electromechanical coupling (k 2) of 26.9% and a high-quality factor (Bode-Q) of 1228, hence resulting in a high figure of merit (FoM = k 2 • Bode-Q) of 330 at 2.28 GHz. Additionally, these fabricated resonators show scalable resonances from 1.61 to 3.05 GHz and impedance ratios between 53.2 and 74.7 dB. Filters based on demonstrated resonators have been demonstrated at 2.16 and 2.29 GHz with sharp roll-off and spurious-free responses over a wide frequency range. The filter with a center frequency of 2.29 GHz shows a 3-dB fractional bandwidth of 9.9%, an insertion loss of 1.38 dB, an out-of-band rejection of 41.6 dB, and a footprint of 0.75 mm 2. Besides, the fabricated filters also show a temperature coefficient of frequency of −48.2 ppm/ • C and power handling of 25 dBm. Although the power handling is limited by arc discharge and migration-induced damage of the interdigital electrodes and some ripples in insertion loss and group delay responses are still present due to the transverse spurious modes, the demonstrations Manuscript
Japanese Journal of Applied Physics, 2003
Lithium niobate (LiNbO 3) films have been grown at 490 C on diamond-coated silicon substrates by radio-frequency magnetron sputtering. A multi-step process was developed to produce thick layers on diamond with a good structure and a smooth morphology. To assess the structural quality of our films, we performed X-ray diffraction, transmission electron microscopy and atomic force microscopy of the films. The structure is conserved whatever the film thickness. A delay line structure of wavelength of 28 mm was realized and transducers were deposited on top of LiNbO 3. The objective was to verify the high velocity in such a multi-layered structure. The first results indicated a SAW velocity estimated of 8200 m/s and a coupling factor was k 2 around 1%. The film growth, the technology and the electrical measurements are described in this paper.
Ferroelectrics, 2008
High-overtone Bulk Acoustic Resonator is an acoustic transducer based on an excitation of a bulk acoustic wave by a thin piezoelectric film bonded to a thick low acoustic loss substrate. This combination of materials aims at providing on the one hand a high frequency transducer as defined by the thickness of the thin piezoelectric layer, and on the other hand the robustness of a thick substrate while keeping the acoustic properties of single crystal piezoelectric materials. More specifically, this architecture provides high quality factors using bulk acoustic wave at frequencies only accessible to surface acoustic wave (SAW) devices with interdigitated transducer generation. The multimode spectrum is well suited for an openloop, wireless interrogation strategy in which the frequency of the incoming electromagnetic wave defines the operating point. We here demonstrate the use of a frequency sweep RADAR-like network analyzer for probing through a wireless link HBARs with different temperature coefficients in order to perform temperature measurements insensitive to other correlated noise sources (capacitive frequency pulling, electrode aging, stress).
2015
Surface acoustic wave (SAW) transducers are a well-established component used in numerous sensors, communications, and electronics devices. In this work, the authors report a systematic study of 320–800 nm period lithium niobate SAW interdigitated transducers (IDTs) corresponding to resonant frequencies in the 4–12 GHz range. An optimized SAW design and a nanofabrication process flow were developed, which enabled superior device performance in terms of frequency, signal losses, and electromagnetic coupling. The influence of the device alignment on the substrate crystal planes, in addition to the IDT period and electrode design, is found to have a significant impact on various process metrics. As an example, two identical SAW transducers fabricated perpendicular to each other may have a resonant frequency difference approaching 1 GHz, for the same harmonic mode. These and other trends are presented and discussed.
Super High Frequency Lithium Niobate Surface Acoustic Wave Transducers up to 14 GHz
2015 IEEE International Electron Devices Meeting (IEDM) Proceedings
We report lithium niobate (LiNbO3) surface acoustic wave (SAW) transducers with the smallest linewidth and the highest resonant frequency. A record 30 nm wide, 200 nm period nanofabricated metallic structure on non-conductive LiNbO3 enables a frequency exceeding 14 GHz. At higher frequencies, greater data throughputs and improved sensor sensitivity are enabled. A systematic study of SAW devices from lamda =200-800 nm is presented taking into account crystal orientation, device design, patterning strategies, and resonant modes. The device performance metrics such as frequency, Q-factor, insertion loss, and coupling coefficient are measured in detail and these metrics are also found to exceed the results of other recent state-of-the-art devices, when compared.
2020
The development of new generations of telecommunication systems requires more and more components and radio-frequency (RF) modules to select and the process signals supporting the information. The solution the most used for this kind of application is always based on the principle of surface acoustic waves (SAW) and its associated components, taking into account their unique spectral quality (insertion losses, out of band rejection, group delay?), their design flexibility and their compactness for L- and S-bands. Although still commonly used today, filters on single-crystals such as lithium tantalate (LiTaO3) and lithium niobate (LiNbO3) cannot be used for future RF modules since the intrinsic stability of these substrates is far from being adapted to meet the challenges of modern telecommunications. To respond to this demands, a new generation of substrates is necessary. The main idea of the work presented here then consists in combining a thin piezoelectric film and a substrate ha...
A Very-High-Velocity Acoustic Wave on a LiNbO$_3$/Sapphire Substrate for Use in Sub-6-GHz Devices
2020
This letter presents a numerical investigation of acoustic modes propagating in an LiNbO$_3$/sapphire substrate under a periodic Al grating, demonstrating the occurrence of longitudinal leaky SAWs (LLSAWs) with a unique combination of very high velocities exceeding 10 000 m/s, an electromechanical coupling coefficients of 4.5%, and negligible leakage into the substrate. The leakage was suppressed by optimizing the LiNbO$_3$ (LN) plate and Al electrode thickness. Compared with conventional SAW substrates, the LN/sapphire substrate offers 2- to 2.5-fold higher frequencies for periodic electrode structures and enables the production of 6-GHz devices by standard photolithographic processes. Moreover, the required LN plate and Al electrode thicknesses remain compatible with existing wafer bonding technologies. An analysis of LLSAW dispersion in a resonator reveals that the wave behaves as a perfect Rayleigh SAW unperturbed by interactions with spurious modes. The found optimal LN/sapphir...
Journal of Crystal Growth, 1981
The liquid phase epitaxy technique has been shown to be successful for developing Nb 5~-richand Na*~modifiedLiNbO 3 films using various flux systems. X-ray diffraction studies showed that the films had a high single crystallinity, and the unit cell aĩ ncreased from 5.143 A for the Li~-richLiNbO3 to 5.155 A for Nat-modified LiNbO3 films. Nat-modified LiNbO3 films, ranging from 10 to 30 pm thickness, showed a reduction in the temperature coefficient of surface acoustic wave (SAW) velocity; the improvement is almost 40%.