(Invited) AlN and ScAlN Contour Mode Resonators for RF Filters

Henry, Michael David; Timon, Robert P.; Young, Travis Ryan; Nordquist, C.D.; Griffin, Benjamin A.

doi:10.1149/07706.0023ecst

Cited by 17 publications

(8 citation statements)

References 14 publications

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“…For example, we have completed simulations that indicate less scattering of vibration energy would result for certain resonator shapes. As for materials, contour-mode resonators made with AlScN were recently demonstrated and showed improved Q and kt 2 compared to AlN [461]. New fabrication processes could also yield benefits such as achieving flat material layers and the freedom to use more conductive (or lighter) materials for the IDE, if the layer sequence were inverted.…”

Section: Mems Me Sensorsmentioning

confidence: 99%

Roadmap on Magnetoelectric Materials and Devices

et al. 2021

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The possibility to tune the magnetic properties of materials with voltage (converse magnetoelectricity) or to generate electric voltage with magnetic fields (direct magnetoelectricity) has opened new avenues in a large variety of technological fields, ranging from information technologies to healthcare devices and including a great number of multifunctional integrated systems such as mechanical antennas, magnetometers, radiofrequency (RF) tunable inductors, etc., which have been realized due to the strong strainmediated magnetoelectric (ME) coupling found in ME composites. The development of singlephase multiferroic materials (which exhibit simultaneous ferroelectric and ferromagnetic or antiferromagnetic orders), multiferroic heterostructures, as well as progress in other ME mechanisms, such as electrostatic surface charging or magneto-ionics (voltage-driven ion migration) have a large potential to boost energy efficiency in spintronics and magnetic actuators. This paper focuses on existing ME materials and devices and reviews the state of the art in their

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Section: Mems Me Sensorsmentioning

confidence: 99%

Roadmap on Magnetoelectric Materials and Devices

et al. 2021

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“…As for single-crystalline Al 1−x Sc x N, the reduction in etch rate occurred much faster: at x = 0.02, the etch rate already reduced to 15% of AlN, and at x = 0.15, it was 12.7% [ 16 ]. Not only has the existence of scandium retarded the etch rate, but its non-volatile etching by-products also re-deposit during the etch process, resulting in a roughened and tapered side wall less than 76° if Ion Beam Etching (IBE) is not used [ 17 , 18 ]. The poor selectivity requires very thick, hard masks during processing and makes it challenging to stop the AlScN etch on underlying metal electrode materials.…”

Section: Introductionmentioning

confidence: 99%

Vertical and Lateral Etch Survey of Ferroelectric AlN/Al1−xScxN in Aqueous KOH Solutions

et al. 2022

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Due to their favorable electromechanical properties, such as high sound velocity, low dielectric permittivity and high electromechanical coupling, Aluminum Nitride (AlN) and Aluminum Scandium Nitride (Al1−xScxN) thin films have achieved widespread application in radio frequency (RF) acoustic devices. The resistance to etching at high scandium alloying, however, has inhibited the realization of devices able to exploit the highest electromechanical coupling coefficients. In this work, we investigated the vertical and lateral etch rates of sputtered AlN and Al1−xScxN with Sc concentration x ranging from 0 to 0.42 in aqueous potassium hydroxide (KOH). Etch rates and the sidewall angles were reported at different temperatures and KOH concentrations. We found that the trends of the etch rate were unanimous: while the vertical etch rate decreases with increasing Sc alloying, the lateral etch rate exhibits a V-shaped transition with a minimum etch rate at x = 0.125. By performing an etch on an 800 nm thick Al0.875Sc0.125N film with 10 wt% KOH at 65 °C for 20 min, a vertical sidewall was formed by exploiting the ratio of the 1011¯ planes and 11¯00 planes etch rates. This method does not require preliminary processing and is potentially beneficial for the fabrication of lamb wave resonators (LWRs) or other microelectromechanical systems (MEMS) structures, laser mirrors and Ultraviolet Light-Emitting Diodes (UV-LEDs). It was demonstrated that the sidewall angle tracks the trajectory that follows the 1¯212¯ of the hexagonal crystal structure when different c/a ratios were considered for elevated Sc alloying levels, which may be used as a convenient tool for structure/composition analysis.

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“…Besides, opting for LiNbO3 to replace AlN imposes fabrication and integration complexities and results in resonators with significantly larger temperature sensitivity due to the large temperature coefficient of elastic constants. To address the challenge of low kt 2 in Lamb-wave resonators, a recent wave of research efforts focuses on enhancing the piezoelectric properties of AlN films through introduction of scandium (Sc) doping [4][5][6]. Experimental studies on the piezoelectric characteristics of Sc-doped AlN (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…ScAlN) thin films has shown a 400-500% improvement in the piezoelectric coefficients for a doping concentration of 40% [7]. Such an improvement translates to a kt 2 of ~30% [6], a value that is 4-5 times larger compared to state-of-art thickness-mode AlN FBARs.…”

Section: Introductionmentioning

confidence: 99%

“…Although successful in improving the kt 2 , ScAlN Lamb-wave resonators suffer from low Qs that are nearly an order of magnitude lower compared to FBARs at the same frequency. The degradation in Q with Sc doping can be attributed to (a) formation of (100)crystalline inclusions in (002) oriented ScAlN films [6] and (b) nonideal etching profile of the films that results in rough and tapered sidewalls [8].…”

Section: Introductionmentioning

confidence: 99%

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HIGH Kt2∙Q LAMB-WAVE SCALN-ON-SILICON UHF AND SHF RESONATORS

Ghatge¹,

Felmetsger²,

Tabrizian³

2018

2018 Solid-State, Actuators, and Microsystems Workshop Technical Digest

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This paper reports, for the first time, on waveguide-based resonators implemented in scandium-doped aluminum nitride-onsilicon (ScAlN-on-Si) stack to simultaneously benefit from large piezoelectric constants of ScAlN and low acoustic dissipation in single crystal silicon. 1m-thick ScAlN film with Sc content of 7% is reactively sputtered on silicon substrates using ac-powered dualtarget S-gun magnetron with Al targets containing embedded pure Sc pellets. A Cl2/H2 based low-power plasma etching recipe is developed to pattern resonators with smooth vertical sidewalls. Inand out-of-plane waveguide-based resonator prototypes with large electromechanical coupling coefficient (kt 2 ) and high quality-factor (Q) are implemented over 80 MHz -3.5 GHz demonstrating kt 2 of 0.7%-2.9% and Q of 2000-6400. Specifically, a high 0 × of 4.3 × 10 12 is measured for a resonator at 3.5 GHz, and a high 2 × of 51 is measured at 108 MHz. The large 2 × of ScAlNon-Si waveguide-based resonators along with lithographical frequency tailorability demonstrate their potential for realization of highly integrated front-end filters for multi-band 5G systems.

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(Invited) AlN and ScAlN Contour Mode Resonators for RF Filters

Cited by 17 publications

References 14 publications

Roadmap on Magnetoelectric Materials and Devices

Roadmap on Magnetoelectric Materials and Devices

Vertical and Lateral Etch Survey of Ferroelectric AlN/Al1−xScxN in Aqueous KOH Solutions

HIGH Kt2∙Q LAMB-WAVE SCALN-ON-SILICON UHF AND SHF RESONATORS

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