Super-High-Frequency SAW Resonators on AlN/Diamond

Abstract

Abstract-This letter describes the procedure to manufacture high-performance surface acoustic wave (SAW) resonators on AlN/diamond heterostructures working at frequencies beyond 10 GHz. In the design of SAW devices on AlN/diamond systems, the thickness of the piezoelectric layer is a key parameter. The influence of the film thickness on the SAW device response has been studied. Optimized thin films combined with advanced e-beam lithographic techniques have allowed the fabrication of one-port SAW resonators with finger width and pitch of 200 nm operating in the 10-14 GHz range with up to 36 dB out-of-band rejection.Index Terms-AlN/diamond, surface acoustic wave (SAW) resonator, super-high-frequency band, thickness influence.

High precision pressure sensors based on SAW devices in the GHz range

“…Moreover, the achieved frequency is the highest obtained among other freestanding NCD structures [22][23][24]. In addition, these results are in agreement with the ones obtained before [28], and confirm that the AIN/free-standing NCD structure is an alternative to the more expensive polished MCD for the processing of high performance and high frequency SAW devices.…”

“…Here, the influence of the AIN thickness on the SAW response of these freestanding structures is studied. The optimum AIN thickness was found to be 300 nm and allows manufacturing high performance and high frequency SAW resonators working above 10 GHz, with similar performance as those achieved before on polished MCD [28]. A sensitivity of 0.33 MHz/bar was observed under pressure conditions.…”

“…The film-thickness-to-wavelength ratio (H¡k) are kH=2TiHjk = 9A2, 4.71, 2.36 and 1.18, respectively. As it was presented elsewhere [28], the electromechanical coupling coefficient (K 2 ) and the propagation velocity of the acoustic waves depend on the H/k. By decreasing the piezoelectric film thickness (small H/k), its crystal quality and orientation decrease, thus the piezoelectricity worsens.…”

“…The principal resonance for the SAW one port resonator fabricated on this film is 12.5 GHz, corresponding to the first Sezawa mode, and it shows a Q. factor of 643 and an out of band rejection of 11 dB. The Qand out of band rejection are better for the device processed on A1N/MCD due to the better quality of the AIN film [28]. Nevertheless, the results obtained for the devices processed on AIN/free-standing NCD are the highest obtained so far on nanocrystalline diamond [32].…”

Surface plasma pretreatment for enhanced diamond nucleation on AlN

“…In the former case, the seeding density improves by almost three orders of magnitude as compared to the untreated and N 2 pretreated samples, and allows to grow pinhole-free nanocrystalline diamond film on AlN. Finally, we demonstrate a route towards selective diamond growth on AlN thin films by employing CF 4 Chemical vapor deposition (CVD) diamond is a versatile material with extreme mechanical, thermal, electronic, and optical properties. Because of its very good chemical stability and bio-inertness, it is currently being studied for a range of applications that make use of its surface and bulk properties, including novel generation of neuroprosthetics 1,2 and (bio-sensing) diamond-based acoustic devices.…”