Research Projects

Piazza Micro and Nano Systems Laboratory

 

“Making MEMS and NEMS”

Micromechanical Signal Processors

Nanomechanical Sensors

Nanomechanical Logic

We are currently developing monolithically integrated Micro/NanoElectroMechanical RF front-ends formed by piezoelectric AlN contour-mode resonators, switches and tunable capacitors.  This new technology offers the ability to span a broad frequency range (from few MHz to GHz) on the same silicon substrate.  The laterally vibrating AlN microstructures integrated with AlN switches and tunable components not only provide the advantages of compact size, low power consumption and compatibility with high yield mass producible components, but can also enable paradigm-shifting solutions for reconfigurable RF front-ends and simpler frequency synthesizers.  In order to achieve the aforementioned goals we are working on fundamental and applied engineering problems related to the AlN resonator and switch technologies.

This project focuses on the fabrication of a new class of gravimetric chemical and biological sensors based on  large scale integration of modified piezoelectric resonant transducers based on the AlN contour-mode technology.  Miniaturization, high sensitivity (thanks to high frequency of operation up to 20 GHz), and ultra-low limit of detection (thanks to an f-Q product increasing with frequencies both in air and liquids) are the key features of this new class of devices.  These  sensors are deemed to surpass in performance any existing device and make possible the deployment of portable and low power devices for environmental monitoring, threat alert, medical diagnostics, cancer research and personalized healthcare.

To enhance the device selectivity we have been working with Prof. Charlie Johnson in physics to integrate single stranded DNA (ss-DNA) decorated single wall carbon nanotubes (SWNT) with the resonator technology. In addition we are developing novel circuit elements to devise wireless sensor platforms.

MEMS/NEMS RF Signal Processors

Micro/NanoElectromechanical Sensors

Current solid state FET transistors have pushed computation speed into the GHz regime at the expense of considerable power consumption, especially in the off state. Continuous scaling of power supply below 1 V and technology node below few nm is limited by the fundamental physics of the MOS transistor.  Nanoelectromechanical systems (NEMS) switches offer the promise of performing logic operations with lower power consumption by reducing transistor subthreshold slope and eliminating leakage currents.   We are currently designing and fabricating piezoelectric NEMS devices with the goal of attaining speeds  comparable to FET transistors (1 ns and lower) and actuation voltages well below 1 V.

NanoElectroMechanical Logic

AlN Micro and NanoElectroMechanical Contour-Mode Resonators and Filters

This work deals with RF MEMS/NEMS and IC co-design for next-generation multi-mode reconfigurable wireless communications. The goal is to implement single-chip multi-frequency resonators, filters and oscillators up to 10 GHz based on piezoelectric AlN contour-mode technology. The key challenges resides in quality factor enhancement, parasitic loss reduction, and nanofabrication of the micro/nano electromechanical devices and also their compatibility with standard CMOS process.

Scaling and Loss Mechanisms in AlN Contour-Mode Resonators

The main objective of this research program is to investigate fundamental physics related to the scaling and loss mechanisms in piezoelectric resonators and filters.

Research activities based on advanced material characterization techniques (SEM, AFM, PFM, XRD) and integration of innovative materials (oriented platinum, diamond, AlN and high conductive metals) can provide the pathway for a tenfold improvement in the quality factor of CMOS-compatible RF-MEMS/NEMS resonators and filters. This technology promises to deliver unparallel gains in terms of performance, functionality and design flexibility for next generation low power radio circuits.

AlN MicroElectroMechanical Switches

AlN based piezoelectric switches will help overcoming the limitations of the present technology used for switching (FET or electrostatic-MEMS based) and demonstrate the next level of integration in wireless devices. AlN based switches can attain large isolation, low loss, fast switching speed (< 1 μsec) and repeatable operations thanks to active pull-off.  Our group has already demonstrated the basic operation of an AlN micromechanical switch. Research is now focused on improving the performance and reliability of the switches and on integration of switch technology with contour mode resonators and filters so that we can achieve a single-chip multi-frequency solution.

Hybrid filter formed by electrically cascading two mechanically coupled sub-filters.  This topology enables the implementation of low loss, high rejection and sharp roll off high order filters in a very small form factor.

AlN Contour-Mode based Pierce Oscillator. This is currently a two- chip solution. We are working towards the integration of the resonator on top of CMOS

 

AlN RF MEMS Switch

Current Projects

Past Projects

High frequency MEMS resonators are the enabling technology behind oscillators, filters, and chemical and inertial sensors. We are developing new classes of resonators that can transform RF communications. Our microsystem approach aims at developing ultra-low power mechanical wake up radios and reconfigurable transceivers. The resonator is formed by an AlN layer sandwiched between metal electrodes. Electrical parameters are defined by device geometry. This technology allows single-chip multi-frequency integration. Entire fabrication is done using CMU Nanofab. To achieve the goals mentioned above members at PMaNS focus on flicker noise, damping analysis, ultralow power ovenization, selfheating filters, and CMOS integration.

AlN High Frequency Piezoelectric Resonators

Lithium Niobate (LN) Resonators

Lithium Niobate is used because of its high electromechanical coupling (kt2) which can be in excess of 20% High kt2 and high Q of lithium niobate resonators enable the development of low-power and reconfigurable RF microsystem Suitable for CMOS-MEMS integration for RF and sensing applications.

Acoustic and photonic phenomena can be combined in the same geometries at the microscale. We are exploiting acousto-optic effects in thin film piezoelectric structures to develop high efficiency RF-photonic modulators and oscillators and high sensitivity gyroscopes.

Acousto-Optics

The aim of this project is to develop chipscale piezoelectric communication links that leverage the enhancement of energy transfer occurring at resonance. Acoustic waves are, in effect, used to enable vicinitybased high efficiency power transfer or authenticating communication within different nodes of an integrated circuit (IC). This communication technology can be used to power/communicate with chips that are embedded in microelectronic packages and ultimately sensors to detect counterfeiting in the electronic supply chain. Near-field wireless powering of microsystems operating in hazardous and inaccessible areas are among other potential applications.

 

ChipScale Acoustic Communication