Integrated Aluminum Nitride Piezoelectric Microelectromechanical System for Radio Front Ends

This article summarizes the most recent technological developments in the realization of integrated aluminum nitride (AlN) piezoelectric microelectromechanical system (MEMS) for radio frequency (rf) front ends to be employed in next generation wireless communication devices. The AlN-based resonator and switch technologies are presented, their principle of operation explained, and some key experimental achievements showing device operations between 20 MHz and 10 GHz are introduced. Fundamental material, device, and fabrication aspects that needed to be taken into account for the demonstration of the first integrated rf MEMS solution based on the combination of AlN MEMS resonators and switches are highlighted. Given the ability to operate over a broad range of frequencies on a single silicon chip, the AlN MEMS technology is extremely attractive for the demonstration of reconfigurable and multiband rf transceivers. Next generation rf architectures that take advantage of large scale integration of AlN MEMS resonators and switches are briefly presented

One and Two Port Piezoelectric Higher Order Contour-Mode MEMS Resonators for Mechanical Signal Processing

This paper reports on the design, fabrication and testing of novel one and two port piezoelectric higher order contour-mode MEMS resonators that can be employed in RF wireless communications as frequency reference elements or arranged in arrays to form banks of multi-frequency filters. The paper offers a comparison of one and two port resonant devices exhibiting frequencies approximately ranging from 200 to 800 MHz, quality factor of few thousands (1000–2500) and motional resistances ranging from 25 to 1000 Ω. Fundamental advantages and limitations of each solution are discussed. The reported experimental results focus on the response of a higher order one port resonator under different environmental conditions and a new class of two port contour resonators for narrow band filtering applications. Furthermore, an overview of novel frequency synthesis schemes that can be enabled by these contour-mode resonators is briefly presented

Single-Ended-to-Differential and Differential-to-Differential Channel-Select Filters Based on Piezoelectric AlN Contour-Mode MEMS Resonators

This paper reports on the first demonstration of single-ended-to-differential and differential-to-differential (S2D and D2D) channel-select filters based on single-layer (SL) and dual-layer-stacked (DLS) AlN contour-mode MEMS resonators. The key filter performances in terms of insertion loss (as low as 1.4 dB), operating frequency (250-1280 MHz), and out-of-band rejection (up to 60 dB) constitute a significant advancement over all other state-of-the-art RF MEMS technologies. The fabrication process, namely stacking of two piezoelectric AlN layers (600 nm each) and three Pt electrode layers (100 nm each), is fully compatible with the previously demonstrated AlN RF MEMS switch process (also post-CMOS compatible), which makes it possible to implement multi-frequency switchable filter banks on a single chip. The S2D configuration is also able to combine the balun, filter, and impedance transformer functions in a single MEMS structure and only takes on a very small form factor (60×200 μm). These unique features will potentially revolutionize the field of RF and microwave IC design by enabling MEMS-IC co-design and the development of unconventional and low-power RF architectures

Two-Port Stacked Piezoelectric Aluminum Nitride Contour-Mode Resonant MEMS

This paper reports on design, fabrication and experimental testing of a new class of two-port stacked piezoelectric aluminum nitride contour-mode micromechanical resonators that can be used for RF filtering and timing applications. This novel design consists of two layers of thin film AlN stacked on top of each other and excited in contour mode shapes using the d31 piezoelectric coefficient. Main feature of this design is the ability to reduce capacitive parasitic feedthrough between input and output signals while maintaining strong electromechanical coupling. For example, these piezoelectric contour-mode resonators show a quality factor of 1,700 in air and a motional resistances as low as 175 Ω at a frequency of 82.8 MHz. The input to output capacitance has been limited to values below 80 fF, therefore simplifying signal detection even at high frequencies

Ultra-Thin-Film AlN Contour-Mode Resonators for Sensing Applications

This paper reports on the design and experimental verification of a new class of ultra-thin-film (250 nm) aluminum nitride (AlN) microelectromechanical system (MEMS) contour mode resonators (CMRs) suitable for the fabrication of ultra-sensitive gravimetric sensors. The device thickness was opportunely scaled in order to increase the mass sensitivity, while keeping a constant frequency of operation. In this first demonstration the resonance frequency of the device was set to 178 MHz and a mass sensitivity as high as 38.96 KHz⋅μm2/fg was attained. This device demonstrates the unique capability of the CMR-S technology to decouple resonance frequency from mass sensitivity

High Frequency Piezoelectric Resonant Nanochannel for Bio-Sensing Applications in Liquid Environment

This paper reports on the first demonstration of a 457 MHz AlN Piezolectric Resonant Nanochannel (PRN) for biosensing applications in liquid environment. A novel process consisting of 7 lithographic steps was developed to fabricate the PRN. The new resonant device shows an unchanged value of the electromechanical coupling, kt 2 (about 0.8 %), whether the channel is filled with air or water and a quality factor, Q, in liquid of approximately 170. The value of kt 2 and Q are respectively about 2.7 and 2 times the ones recorded for conventional laterally vibrating AlN Contour Mode Resonant Sensors (CMR-Ss) submerged in water. Overall, these results translate in a ~ 5 fold enhancement in the figure of merit (kt 2 - Q product) of the resonant device when operated in liquid and simultaneously permit the efficient delivery of ultra-low concentrations of fluid samples directly on the surface of the sensor

Power Handling and Related Frequency Scaling Advantages in Piezoelectric AlN Contour-Mode MEMS Resonators

This paper reports on the analytical modeling and experimental verification of the mechanically-limited power handling and nonlinearity in piezoelectric aluminum nitride (AlN) contour-mode resonators (CMR) having different electrode configurations (thickness field excitation, lateral field excitation, one-port and two-port configurations) and operating at different frequencies (177-3047 MHz). Despite its simplicity, the one-dimensional analytical model fits the experimental behavior of AlN CMRs in terms of power handling capabilities. The model and experiment also confirm the advantage of scaling (i.e. miniaturizing) the AlN CMRs to higher frequencies at which higher critical power density can be more easily attained up to values in excess of 10 μW/μm3

Novel Electrode Configurations in Dual-Layer Stacked and Switchable AlN Contour-Mode Resonators for Low Impedance Filter Termination and Reduced Insertion Loss

This paper reports, for the first time, on the design and demonstration of two novel electrode configurations in dual-layer stacked Aluminum Nitride (AlN) piezoelectric contour-mode resonators to obtain low filter termination resistance (down to 300 Ω, which also results in better filter out-of-band rejection) and reduced insertion loss (IL as low as 1.6 dB) in multi-frequency (100 MHz – 1 GHz) AlN MEMS filters. The microfabrication process is fully compatible with the previously demonstrated AlN RF MEMS switches, which makes it possible to design and integrate multi-frequency switchable filter banks on a single chip

5-10 GHz AlN Contour-Mode Nanoelectromechanical Resonators

This paper reports on the design and experimental verification of Super High Frequency (SHF) laterally vibrating NanoElctroMechanical (NEMS) resonators. For the first time, AlN piezoelectric nanoresonators with multiple frequencies of operation ranging between 5 and 10 GHz have been fabricated on the same chip and attained the highest f-Q product (4.6E12 Hz) ever reported in AlN contour-mode devices. These piezoelectric NEMS resonators are the first of their class to demonstrate on-chip sensing and actuation of nanostructures without the need of cumbersome or power consuming excitation and readout systems. Effective piezoelectric activity has been demonstrated in thin AlN films having vertical and lateral features in the range of 250 nm