Monolithic Integration Piezoelectric Resonators on CMOS for Radio-Frequency and Sensing Applications

Software cognitive radios and Internet of Things (IoT) are recent interest areas that need low loss and low power consumption hardware. More specifically, the area of software cognitive radios requires that hardware be frequency agile and highly selective. Meanwhile, IoT relies on multiple low power sensor networks. By combining Complementary Metal Oxide Semiconductors (CMOS) technology with piezoelectric Micro-Electro-Mechanical Systems (MEMS), we can fabricate Systems-on-Chip (SoC) that can be used as filters or references (oscillators) and highly selective sensors. In this work we developed a die-level compatible process for the monolithic integration of Bulk Acoustic Resonators (BAWs) on CMOS for low power, reduced area and high-quality passives for radio frequency applications. Using CMOS as a fabrication substrate some stringent requirements were added to maintain the dies and the technology’s integrity. A few of these limitations were the need for a low thermal budget fabrication process, die handling and electro-static discharge (ESD) protection. The devices were first fabricated on glass for modeling extraction that was later used for the design of the integrated circuits (IC). Three integrated circuits were designed as substrates for the integration using IBM’s 180nm and TSMC’s 65nm technology. A monolithic BAW oscillator with a resonance frequency of 1.8GHz was demonstrated with an FOM ~186dBc/Hz, comparable to other academia work. Using the developed process, a membrane BAW structure (FBAR) was integrated as well. Using a susceptor coating and zinc oxide’s (ZnO) high temperature coefficient of frequency (TCF) the device was studied as an alternative uncooled infrared sensor. Finally, a reprogrammable IC and an RF PCB were designed for volatile organic compound (VOC) testing using self-assembled monolayers (SAMs) as the absorber layer

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

Monolithically Integrated Acoustic Resonators on CMOS for Radio-Frequency Circuit Applications

Wireless communication circuits rely on the use of high-quality passive elements (inductor-capacitor resonant tanks) for the implementation of selective filters and high-purity frequency references (oscillators). Typically available CMOS, on-chip passives suffer from high losses, primarily inductors, and consume large areas that cannot be populated by transistors leading to a significant area penalty. Mechanical resonators exhibit significantly lower losses than their electrical counterparts due to the reduced parasitic loss mechanisms in the mechanical domain. Efficient transduction schemes such as the piezoelectric effect allow for simple electrical actuation and read-out of such mechanical resonators. Piezoelectric thin-film bulk acoustic resonators (FBARs) are currently among the most promising and widely used mechanical resonator structures. However, FBARs are currently only available as off-chip components, which must be connected to CMOS circuitry through wire-bonding and flip-chip schemes. The use of off-chip interfaces introduces considerable parasitics and significant limitations on integration density. Monolithic integration with CMOS substrates alleviates interconnect parasitics, increases integration density and allows for area sharing whereby FBARs reside atop active CMOS circuitry. Close integration of FBARs and CMOS transistors can also enable new circuit paradigms, which simultaneously leverage the strengths of both components. Described here, is a body of work conducted to integrate FBAR resonators with active CMOS substrates (180nm and 65nm processes). A monolithic fabrication method is described which allows for FBAR devices to be constructed atop the backend small CMOS dies through low thermal-budget (< 300°C) post-processing. Stand-alone fabricated devices are characterized and the extracted electrical model is used to design two oscillator chips. The chips comprise amplifier circuitry that functions along with the integrated FBARs to achieve oscillation in the 0.8-2 GHz range. The chips also include test structures to assess the performance of the underlying CMOS transistors before and after the resonator post-processing. A successful FBAR-CMOS oscillator is demonstrated in 65nm CMOS along with characterization of FBARs built on CMOS. The approach presented here can be used for experimenting with more complex circuits leveraging the co-integration of piezoelectric resonators and CMOS transistors

Resonant body transistors in standard CMOS technology

This work presents Si-based electromechanical resonators fabricated at the transistor level of a standard SOI CMOS technology and realized without the need for any postprocessing or packaging. These so-called Resonant Body Transistors (RBTs) are driven capacitively and sensed by piezoresistively modulating the drain current of a Field Effect Transistor (FET). First generation devices operating at 11.1-11.5 GHz with footprints of 3μm×5μm are demonstrated. These unreleased bulk acoustic resonators are completely buried within the CMOS stack and acoustic energy at resonance is confined using Acoustic Bragg Reflectors (ABRs). The complimentary TCE of Si/SiO[subscript 2] in the resonator and the surrounding ABRs results in a temperature stability TCF of <;3 ppm/K. Comparative behavior of devices is also discussed to analyze the effect of fabrication variations and active sensing.United States. National Security Agency. Trusted Access Program OfficeUnited States. Defense Advanced Research Projects Agency. Leading Edge Access ProgramIBM Researc

RF MEMS/NEMS RESONATORS FOR WIRELESS COMMUNICATION SYSTEMS AND ADSORPTION-DESORPTION PHASE NOISE

During the past two decades a considerable effort has been made to develop radio-frequency (RF) resonators which are fabricated using the micro/nanoelectro-mechanical systems (MEMS/NEMS) technologies, in order to replace conventional large off-chip components in wireless transceivers and other high-speed electronic systems.The first part of the paper presents an overview of RF MEMS and NEMS resonators, including those based on two-dimensional crystals (e.g. graphene). The frequency tuning in MEMS/NEMS resonators is then analyzed. Improvements that would be necessary in order for MEMS/NEMS resonators to meet the requirements of wireless systems are also discussed.The analysis of noise of RF MEMS/NEMS resonators and oscillators is especially important in modern wireless communication systems due to increasingly stringent requirements regarding the acceptable noise level in every next generation. The second part of the paper presents the analysis of adsorption-desorption (AD) noise in RF MEMS/NEMS resonators, which becomes pronounced with the decrease of components' dimensions, and is not sufficiently elaborated in the existing literature about such components. Finally, a theoretical model of phase noise in RF MEMS/NEMS oscillators will be presented, with a special emphasize on the influence of the resonator AD noise on the oscillator phase noise

Gallium Nitride Integrated Microsystems for Radio Frequency Applications.

The focus of this work is design, fabrication, and characterization of novel and advanced electro-acoustic devices and integrated micro/nano systems based on Gallium Nitride (GaN). Looking beyond silicon (Si), compound semiconductors, such as GaN have significantly improved the performance of the existing electronic devices, as well as enabled completely novel micro/nano systems. GaN is of particular interest in the “More than Moore” era because it combines the advantages of a wide-band gap semiconductor with strong piezoelectric properties. Popular in optoelectronics, high-power and high-frequency applications, the added piezoelectric feature, extends the research horizons of GaN to diverse scientific and multi-disciplinary fields. In this work, we have incorporated GaN micro-electro-mechanical systems (MEMS) and acoustic resonators to the GaN baseline process and used high electron mobility transistors (HEMTs) to actuate, sense and amplify the acoustic waves based on depletion, piezoelectric, thermal and piezo-resistive mechanisms and achieved resonance frequencies ranging from 100s of MHz up to 10 GHz with frequency×quality factor (f×Q) values as high as 1013. Such high-performance integrated systems can be utilized in radio frequency (RF) and microwave communication and extreme-environment applications.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135799/1/azadans_1.pd