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Yanbo He

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Universidad Nacional del Sur

Arizona State University

PROF. OM PRAKASH SINHA

Amity University

Suseendran Jayachandran

IMEC

University of Illinois at Urbana-Champaign

National Institute of Technology, Calicut

Pontificia Universidad Catolica de Chile

Abdullah Atalar

Bilkent University

A. H. M. ZAHIRUL ALAM Alam

International Islamic University Malaysia

University of East London

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Papers by Yanbo He

Analysis and Design Considerations for Achieving the Fundamental Limits of Phase Noise in mmWave Oscillators with On-Chip MEMS Resonator

arXiv (Cornell University), May 12, 2020

Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or ac... more Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or acoustic resonators is quite of a concern for oscillator performance, specially at mmWave frequencies. This small coefficient is the manifestation of the small ratio of motional capacitance to static capacitance in the resonators. This work provides a general solution to overcome the problem of relatively high static capacitance at mmWave frequencies and presents analysis and design techniques for achieving extremely low phase noise and a very high figureof-merit (FoM) in an on-chip MEMS resonator based mmWave oscillator. The proposed analysis and techniques are validated with design and simulation of a 30 GHz oscillator with MEMS resonator having quality factor of 10,000 in 14 nm GF technology. Post layout simulation results show that it achieves a phase noise of -132 dBc/Hz and FoM of 217 dBc/Hz at offset of 1 MHz.

Integrated acoustic resonators in commercial fin field-effect transistor technology

Nature Electronics

In radio communication, the growth of beamforming and multiple-input–multiple-output technologies... more In radio communication, the growth of beamforming and multiple-input–multiple-output technologies, which increase transceiver complexity, have led to a drive to reduce the size, weight and power of radio components by integrating them into a single system on chip. One approach is to integrate the frequency references of acoustic microelectromechanical systems (MEMS) with complementary metal–oxide–semiconductor processes, typically through a MEMS-first or MEMS-last approach that requires process customization. Here we report unreleased acoustic resonators that are fabricated in 14 nm fin field-effect transistor technology and operate in the X-band frequency range (8–12 GHz). The devices use phononic waveguides for acoustic confinement and exploit metal–oxide–semiconductor capacitors and transistors to electromechanically drive and sense acoustic vibrations. Fifteen device variations are analysed across 30 bias points, quantifying the importance of phononic confinement on resonator pe...

Dataset for "X-Band Fin Resonant Body Transistors in 14nm CMOS Technology

Companion dataset and code for "X-Band Fin Resonant Body Transistors in 14nm CMOS Technology... more

Piezoelectric MEMS Devices in CMOS-Compatible Platform

Integrating piezoelectrics with the standard complementary metal-oxide-semiconductor (CMOS) proce... more Integrating piezoelectrics with the standard complementary metal-oxide-semiconductor (CMOS) process presents new opportunities for monolithic microelectromechanical systems (MEMS) with scaled size, weight, and power (SWaP). Unlike traditional electrostatic transduction in CMOS platform, piezoelectric actuation allows higher sensitivity and electromechanical coupling, and as such, has been recently adopted by foundries like TSMC and Globalfoundries in their standard CMOS lines for commercial MEMS applications. In this research, a tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS resonator is presented, integrated seamlessly in Texas Instruments' 130nm ferroelectric random-access memory (RAM) process. To achieve high-quality factor (<i>Q</i>) of the resonator, acoustic waveguiding for vertical confinement within the CMOS stack is studied and optimized. The FeCAP resonator is demonstrated with fundamental resonance at 703 MHz and <i>Q</i> of 1...

Analysis and Design Considerations for Achieving the Fundamental Limits of Phase Noise in mmWave Oscillators With On-Chip MEMS Resonator

IEEE Transactions on Circuits and Systems II: Express Briefs, 2021

Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or ac... more Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or acoustic resonators is quite of a concern for oscillator performance, specially at mmWave frequencies. This small coefficient is the manifestation of the small ratio of motional capacitance to static capacitance in the resonators. This work provides a general solution to overcome the problem of relatively high static capacitance at mmWave frequencies and presents analysis and design techniques for achieving extremely low phase noise and a very high figureof-merit (FoM) in an on-chip MEMS resonator based mmWave oscillator. The proposed analysis and techniques are validated with design and simulation of a 30 GHz oscillator with MEMS resonator having quality factor of 10,000 in 14 nm GF technology. Post layout simulation results show that it achieves a phase noise of -132 dBc/Hz and FoM of 217 dBc/Hz at offset of 1 MHz.

Integrated acoustic resonators in commercial fin field-effect transistor technology

Nature electronics, Sep 23, 2022

here is currently an increased focus on the functional diversification of existing semiconductor ... more here is currently an increased focus on the functional diversification of existing semiconductor process nodes to create new technologies 1,2 . This approach increases performance, supply chain resilience and security by reducing the number of chips from different process technologies that must be integrated and packaged into the final product. For technologies such as the fifth generation of wireless communications technology, such innovation is necessary to enable high-performance adaptable radios, where high-frequency resonators are a key element in both filters and voltage-controlled oscillators used. Recent developments in this area include thin-film bulk acoustic resonators with ferroelectric materials, as well as high-frequency Lamb-and Lamé-wave resonators using piezoelectric lithium niobate or aluminium nitride thin films 3-6 . To address band congestion, multiple-input-multiple-output arrays are becoming increasingly common as a way to multiplex transmissions between users in the same band, with large arrays allowing for increased performance across end users sharing the spectrum 7 . The beamforming enabled by such an antenna array is of particular use for higher-frequency bands, where propagation conditions are less stable due to increased radio-frequency (RF) absorption. These RF front ends require many more analogue components to be integrated in a compact form factor, driving research in RF integration into traditional digital processes. Many high-performance technologies require integration using microelectromechanical systems (MEMS)-first or MEMS-last process schemes 8-10 , which provide space and power savings compared with off-chip RF integration. The use of phononic-crystal (PnC) confinement, however, could allow resonator integration directly into a standard complementary metal-oxide-semiconductor (CMOS) process, potentially leading to larger multiple-inputmultiple-output arrays in a smaller footprint at lower power . In addition to reducing parasitics from routing high-frequency signals over long distances, this also provides the opportunity to use high-performance transistors for active transduction, leading to potentially enhanced performance. Such an approach also provides a route to future acoustic coupling between devices co-located on the same chip, which reduces the need for power-hungry phase-locked loops and allows scaled coupled oscillator systems for neuromorphic computing to be explored . In this Article, we report CMOS fin field-effect transistor (FinFET)-based resonators that utilize acoustic waveguiding confinement operating in the Institute of Electrical and Electronics Engineers (IEEE) X-band of 8-12 GHz.

A tunable ferroelectric based unreleased RF resonator

arXiv (Cornell University), May 14, 2019

This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS ... more This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS resonator, integrated seamlessly in Texas Instruments' 130nm Ferroelectric RAM (FeRAM) technology. An array of FeCAPs in this complementary metal-oxide-semiconductor (CMOS) technology's back-end-of-line (BEOL) process were used to define the acoustic resonance cavity as well as the electromechanical transducers. To achieve high quality factor (Q) of the resonator, acoustic waveguiding for vertical confinement within the CMOS stack is studied and optimized. Additional design considerations are discussed to obtain lateral confinement and suppression of spurious modes. An FeCAP resonator is demonstrated with fundamental resonance at 703 MHz and Q of 1012. This gives a frequency-quality factor product 𝑓 • 𝑄 = 7.11 × 10 11 which is 1.6x higher than the most state-of-the-art Pb(Zr,Ti)O3 (PZT) resonators. Due to the ferroelectric characteristics of the FeCAPs, transduction of the resonator can be switched on and off by adjusting the electric polarization. In this case, the resonance can be turned off completely at ±0.3V corresponding to the coercive voltage of the constituent FeCAP transducers. These novel switchable resonators may have promising applications in on-chip timing, ad-hoc radio front ends, and chip-scale sensors.

A Ferroelectric Capacitor (Fecap) Based Unreleased Resonator

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

We present the first Pb(Zr,Ti)O3 (PZT)-transduced unreleased RF MEMS resonator embedded seamlessl... more We present the first Pb(Zr,Ti)O3 (PZT)-transduced unreleased RF MEMS resonator embedded seamlessly in CMOS. The unreleased resonators were realized by using Texas Instruments' Ferroelectric RAM (FeRAM) 130nm technology [1]. A new method of acoustic waveguiding within the CMOS stack was used to confine the resonance mode and an array of ferroelectric capacitors (FeCAPs) inherent to the technology was used as driving and sensing transducers. A resonance frequency of 722 MHz is observed with quality factor Q of 656 and electromechanical coupling coefficient keff 2 of 0.35%. This corresponds to f•Q of 4.7×10 11 , comparable to state-of-the-art PZT resonators [2]. These high Q, small footprint resonators offer a CMOS-integrated RF building block with no post-processing or costly packaging.

A mmWave Oscillator Design Utilizing High-Q Active-Mode On-Chip MEMS Resonators for Improved Fundamental Limits of Phase Noise

Recent progress in MEMS resonant-fin-transistors (RFT) allows very high-Q active mode resonators,... more Recent progress in MEMS resonant-fin-transistors (RFT) allows very high-Q active mode resonators, promising crystal-less monolithic clock generation for mmWave systems. However, there is a strong need for design of mmWave oscillators that utilize the high-Q of active-mode RFT (AM-RFT) optimally, while handling unique challenges such as resonator’s low electromechanical transduction. In this brief, we develop a theory and through design and post-layout simulations in 14-nm Global Foundry process, we show the first active oscillator with AM-RFT at 30 GHz, which improves the fundamental limits of phase noise and figure-of-merit as compared to the oscillators with conventional LC resonators. For AM-RFT with Q-factor of 10K, post layout simulation results show that the proposed oscillator exhibits phase noise <-140 dBc/Hz and figure-of-merit >228 dBc/Hz at 1 MHz offset for 30 GHz center frequency, which are >25 dB better than the existing monolithic LC oscillators. Keywords—Osci...

Switchable Mechanical Resonance Induced by Hysteretic Piezoelectricity in Ferroelectric Capacitors

This paper reports on a new switching and frequency hopping mechanism of electromechanical transd... more This paper reports on a new switching and frequency hopping mechanism of electromechanical transduction in ferroelectric capacitor (FeCAP) based CMOS-MEMS resonators implemented in Texas Instruments (TI) FeRAM technology. In this work, poling parameters are investigated to demonstrate bias-dependent pole/zero transitions accompanied by 180° phase shift in multiple mechanical modes of the device. To explain this behavior, the resonator Butterworth-Van Dyke (BVD) model is modified to account for nonlinear capacitance in the FeCAPs. The cancellation of motional branch current and feedthrough current between the Pb(Zr, Ti)O3 (PZT) thin layers with bias voltage enables switching of electromechanical transduction. These switchable, CMOS-integrated FeCAP resonators are solidly confined with no release step using Back-End-of-Line (BEOL) acoustic waveguiding. This study highlights the unique benefits of ferroelectric transducers for nonlinear, tunable MEMS devices, and offers a promising new...

X-Band Fin Resonant Body Transistors in 14nm CMOS Technology

Here we present the first demonstration and in-depth study of unreleased acoustic resonators in 1... more Here we present the first demonstration and in-depth study of unreleased acoustic resonators in 14nm FinFET technology in the IEEE X band, which offer a zero-barrier-to-entry solution for high Q, small footprint, resonant tanks integrated seamlessly in advanced CMOS nodes. These devices leverage phononic waveguides for acoustic confinement, and exploit MOS capacitors and transistors inherent to the technology to electromechanically drive and sense acoustic vibrations. Sixteen device variations are analyzed across thirty bias points to discern the impact of phononic confinement, gate length, and termination scheme on resonator properties. The limiting factor in FinFET resonator performance among design variations tested is shown to be Back End of Line (BEOL) confinement, with devices with acoustic waveguides incorporating Mx and Cx metal layers exhibiting 2.2x higher average quality factor (Q) and peak amplitude, with maximum Q increasing from 115 to 181 and maximum amplitude scaling...

Localized Modes in Asymmetric Phononic Crystals

This paper reports on a localized mechanical resonance induced by a novel phononic crystal (PnC) ... more This paper reports on a localized mechanical resonance induced by a novel phononic crystal (PnC) design demonstrated in a $1\ \mu \mathrm{m}$ aluminum nitride (AlN) thin film. An asymmetric PnC with diagonal beam bridging discs in a square lattice generates an isolated mode inside the PnC bandgap defined by the flexural mode of the connecting beam. Here we investigate the properties of the PnC dispersion relations as a function of key design parameters, defining resonance cavities to excite the localized mode. PnC resonators with localized mode at 156 MHz are characterized as a function of central bar rotation angle ($\theta$), number of actuation layers ($\mathrm{N}_{act}$) and lateral periods (P). This analysis of electromechanical modes with designed flat dispersion relation is an important first step toward Density-Near-Zero (DNZ) metamaterials and resilient elastic wave manipulation on chip.

Band Gap Structure of Two Dimensional Acoustic Metamaterials with Coated Double Hybrid Lattice

Acoustic metamaterials (phononic crystals) have received much recent attention. Over time, severa... more Acoustic metamaterials (phononic crystals) have received much recent attention. Over time, several efforts were proposed to improve the structure in order to enlarge the band gap, lower the band gap frequency, and/or generate greater attenuation of vibration. In this document, a novel two dimensional acoustic metamaterial with Coated Double Hybrid Lattice (CDHL) is proposed. The structure makes use of both the Bragg Scattering Theorem and the Local Resonance Theorem. In the simulation, both a lower frequency band gap and a higher frequency band gap are obtained. According to the modal analysis and phase spectrum analysis, it is proved that the lower frequency band gap is due to local resonance between the double lead cores and the rubber coating. At the same time, the higher frequency band gap is generated as a result of the interaction of Bragg scattering and local resonance effect. The variation in maximum vibration attenuation with respect to the position of the double central le...

32GHz resonant-fin transistors in 14nm FinFET technology

2018 IEEE International Solid - State Circuits Conference - (ISSCC)

Monolithic integration of microelectromechanical resonators in IC technology has been explored ex... more Monolithic integration of microelectromechanical resonators in IC technology has been explored extensively over the past few decades in the effort to achieve on-chip clocks, RF filters, and physical, chemical, and biological sensors. Various approaches for resonator integration, actuation, and sensing have been proposed and demonstrated, targeting high Q and high frequency performance [1]. These include the “MEMS-last” approach with low temperature materials deposited on complete CMOS chips [2,3], and “MEMS-in-the-middle” in which resonators are defined with post-processing of the front end and back end materials of the IC stack [4]. These methods require additional processing and packaging steps that make frequency scaling challenging and may limit resonator Q. Meanwhile, in the case of monolithically integrated MEMS resonators, transistor sensing can be used to enhance transduction efficiency and reduce parasitics, which can prohibit 2-port detection for high frequency resonance [5]. In this work, we introduce the Resonant Fin Transistor (RFT) fabricated in GLOBALFOUNDRIES 14nm FinFET technology, leveraging the vertical 3D geometry of FinFETs (Fig. 21.3.1) to efficiently confine, drive, and sense acoustic vibrations in the solid (unreleased) CMOS stack with no post-processing or custom packaging. We demonstrate 32GHz resonators with Q∼49,000.

Opportunities and challenges of 2D materials in back-end-of-line interconnect scaling

Journal of Applied Physics

As the challenges in continued scaling of the integrated circuit (IC) technology escalate every g... more As the challenges in continued scaling of the integrated circuit (IC) technology escalate every generation, there are urgent needs to find viable solutions for both the front-end-of-line (transistors) and the back-end-of-line (interconnects). For the interconnect technology, it is crucial to replace the conventional barrier and liner with much thinner alternatives so that the current driving capability of the interconnects can be maintained or even improved. Due to the inherent atomically thin body thicknesses, 2D materials have been proposed and explored as Cu diffusion barrier alternatives recently. In this Perspective article, a variety of 2D materials that have been studied, ranging from graphene, h-BN, MoS 2 , WSe 2 , to TaS 2 will be reviewed. Their potentials will be evaluated based on several criteria, including fundamental material properties as well as the feasibility for technology integration. Using TaS 2 as an example, we demonstrate a large set of promising properties and point out there remain challenges in the integration aspects with few possible solutions waiting for validation. Applications of 2D materials for other functions in Cu interconnects and for different metal types will also be introduced, including electromigration, cobalt interconnects, and RF transmission lines. I. Introduction: Copper (Cu) has been the material of choice for interconnects in today's IC chips for more than 20 years. Before the integration scheme for Cu interconnects was available, aluminum (Al) was used as metal interconnects. However, with increasing demands of lower resistivity and better electromigration endurance, Al was eventually replaced with Cu in late 1990s, after many integration challenges had been solved. Overviews of the technology development can be found in refs. 1 and 2. Although Cu offers the advantage of improving interconnect performance, its high diffusivity results in diffusion of Cu atoms/ions into the surrounding dielectric that isolates individual Cu interconnect wires, causing circuit shorting and chip failure 3-6. To prevent this, TaN has been adopted as the "diffusion barrier" to block Cu diffusion 7,8. While possessing a decent diffusion barrier property, the adhesion between TaN and Cu is not ideal. Therefore, Ta has been introduced as the "liner" between Cu and TaN to improve the adhesion 7,8. The schematic of basic interconnect structures is shown in _____________________________

A Ferroelectric Capacitor (Fecap) Based Unreleased Resonator

2018 Solid-State, Actuators, and Microsystems Workshop Technical Digest, May 21, 2018

We present the first Pb(Zr,Ti)O3 (PZT)-transduced unreleased RF MEMS resonator embedded seamlessl... more We present the first Pb(Zr,Ti)O3 (PZT)-transduced unreleased RF MEMS resonator embedded seamlessly in CMOS. The unreleased resonators were realized by using Texas Instruments' Ferroelectric RAM (FeRAM) 130nm technology [1]. A new method of acoustic waveguiding within the CMOS stack was used to confine the resonance mode and an array of ferroelectric capacitors (FeCAPs) inherent to the technology was used as driving and sensing transducers. A resonance frequency of 722 MHz is observed with quality factor Q of 656 and electromechanical coupling coefficient keff 2 of 0.35%. This corresponds to f•Q of 4.7×10 11 , comparable to state-of-the-art PZT resonators [2]. These high Q, small footprint resonators offer a CMOS-integrated RF building block with no post-processing or costly packaging.

Experimental Study of the Transmission Spectrum of a Sonic/Ultrasonic Acoustic Metamaterial

Volume 13: Acoustics, Vibration, and Wave Propagation, 2016

Acoustic metamaterials have received much attention recently. In the past decades, countless stru... more Acoustic metamaterials have received much attention recently. In the past decades, countless structures have been studied for their novel physical phenomenon or potential applications. The goals of many of the works were to explore ways to enlarge the band gap, lower the band gap frequency, and/or generate greater attenuation of vibration. However, most of the work was limited to simulation, with experimental studies rarer. In this work, we would like to experimentally present the transmission spectrum of an acoustic metamaterial with a proposed structure called the coated double hybrid lattice (CDHL) [1]. The CDHL has both crystalline structure and local resonators, which provide high-frequency and low-frequency band gaps, respectively. A structure was fabricated and tested to experimentally determine the transmission spectrum. Both, a higher frequency band gap and a lower frequency band gap, were obtained. Vibration is clearly attenuated in the frequency range of 70–90 kHz. This is due to the Bragg scattering effect. At the same time, around the frequency of 4.8kHz, another band gap is observed which is attributed to local resonance. It turns out that our experimental results coincide with our previous simulation quite well.Copyright © 2016 by ASME

A tunable ferroelectric based unreleased RF resonator

Microsystems & Nanoengineering

This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS ... more This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS resonator, integrated seamlessly in Texas Instruments’ 130 nm Ferroelectric RAM (FeRAM) technology. The designs presented here are monolithically integrated in solid-state CMOS technology, with no post-processing or release step typical of other MEMS devices. An array of FeCAPs in this complementary metal-oxide-semiconductor (CMOS) technology’s back-end-of-line (BEOL) process were used to define the acoustic resonance cavity as well as the electromechanical transducers. To achieve high quality factor (Q) of the resonator, acoustic waveguiding for vertical confinement within the CMOS stack is studied and optimized. Additional design considerations are discussed to obtain lateral confinement and suppression of spurious modes. An FeCAP resonator is demonstrated with fundamental resonance at 703 MHz and Q of 1012. This gives a frequency-quality factor product $$f \cdot Q = 7.11 \times 10^{11...

Analysis and Design Considerations for Achieving the Fundamental Limits of Phase Noise in mmWave Oscillators with On-Chip MEMS Resonator

arXiv (Cornell University), May 12, 2020

Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or ac... more Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or acoustic resonators is quite of a concern for oscillator performance, specially at mmWave frequencies. This small coefficient is the manifestation of the small ratio of motional capacitance to static capacitance in the resonators. This work provides a general solution to overcome the problem of relatively high static capacitance at mmWave frequencies and presents analysis and design techniques for achieving extremely low phase noise and a very high figureof-merit (FoM) in an on-chip MEMS resonator based mmWave oscillator. The proposed analysis and techniques are validated with design and simulation of a 30 GHz oscillator with MEMS resonator having quality factor of 10,000 in 14 nm GF technology. Post layout simulation results show that it achieves a phase noise of -132 dBc/Hz and FoM of 217 dBc/Hz at offset of 1 MHz.

Integrated acoustic resonators in commercial fin field-effect transistor technology

Nature Electronics

In radio communication, the growth of beamforming and multiple-input–multiple-output technologies... more In radio communication, the growth of beamforming and multiple-input–multiple-output technologies, which increase transceiver complexity, have led to a drive to reduce the size, weight and power of radio components by integrating them into a single system on chip. One approach is to integrate the frequency references of acoustic microelectromechanical systems (MEMS) with complementary metal–oxide–semiconductor processes, typically through a MEMS-first or MEMS-last approach that requires process customization. Here we report unreleased acoustic resonators that are fabricated in 14 nm fin field-effect transistor technology and operate in the X-band frequency range (8–12 GHz). The devices use phononic waveguides for acoustic confinement and exploit metal–oxide–semiconductor capacitors and transistors to electromechanically drive and sense acoustic vibrations. Fifteen device variations are analysed across 30 bias points, quantifying the importance of phononic confinement on resonator pe...

Dataset for "X-Band Fin Resonant Body Transistors in 14nm CMOS Technology

Companion dataset and code for "X-Band Fin Resonant Body Transistors in 14nm CMOS Technology... more

Piezoelectric MEMS Devices in CMOS-Compatible Platform

Integrating piezoelectrics with the standard complementary metal-oxide-semiconductor (CMOS) proce... more Integrating piezoelectrics with the standard complementary metal-oxide-semiconductor (CMOS) process presents new opportunities for monolithic microelectromechanical systems (MEMS) with scaled size, weight, and power (SWaP). Unlike traditional electrostatic transduction in CMOS platform, piezoelectric actuation allows higher sensitivity and electromechanical coupling, and as such, has been recently adopted by foundries like TSMC and Globalfoundries in their standard CMOS lines for commercial MEMS applications. In this research, a tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS resonator is presented, integrated seamlessly in Texas Instruments' 130nm ferroelectric random-access memory (RAM) process. To achieve high-quality factor (<i>Q</i>) of the resonator, acoustic waveguiding for vertical confinement within the CMOS stack is studied and optimized. The FeCAP resonator is demonstrated with fundamental resonance at 703 MHz and <i>Q</i> of 1...

Analysis and Design Considerations for Achieving the Fundamental Limits of Phase Noise in mmWave Oscillators With On-Chip MEMS Resonator

IEEE Transactions on Circuits and Systems II: Express Briefs, 2021

Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or ac... more Very small electromechanical coupling coefficient in micro-electromechanical systems (MEMS) or acoustic resonators is quite of a concern for oscillator performance, specially at mmWave frequencies. This small coefficient is the manifestation of the small ratio of motional capacitance to static capacitance in the resonators. This work provides a general solution to overcome the problem of relatively high static capacitance at mmWave frequencies and presents analysis and design techniques for achieving extremely low phase noise and a very high figureof-merit (FoM) in an on-chip MEMS resonator based mmWave oscillator. The proposed analysis and techniques are validated with design and simulation of a 30 GHz oscillator with MEMS resonator having quality factor of 10,000 in 14 nm GF technology. Post layout simulation results show that it achieves a phase noise of -132 dBc/Hz and FoM of 217 dBc/Hz at offset of 1 MHz.

Integrated acoustic resonators in commercial fin field-effect transistor technology

Nature electronics, Sep 23, 2022

here is currently an increased focus on the functional diversification of existing semiconductor ... more here is currently an increased focus on the functional diversification of existing semiconductor process nodes to create new technologies 1,2 . This approach increases performance, supply chain resilience and security by reducing the number of chips from different process technologies that must be integrated and packaged into the final product. For technologies such as the fifth generation of wireless communications technology, such innovation is necessary to enable high-performance adaptable radios, where high-frequency resonators are a key element in both filters and voltage-controlled oscillators used. Recent developments in this area include thin-film bulk acoustic resonators with ferroelectric materials, as well as high-frequency Lamb-and Lamé-wave resonators using piezoelectric lithium niobate or aluminium nitride thin films 3-6 . To address band congestion, multiple-input-multiple-output arrays are becoming increasingly common as a way to multiplex transmissions between users in the same band, with large arrays allowing for increased performance across end users sharing the spectrum 7 . The beamforming enabled by such an antenna array is of particular use for higher-frequency bands, where propagation conditions are less stable due to increased radio-frequency (RF) absorption. These RF front ends require many more analogue components to be integrated in a compact form factor, driving research in RF integration into traditional digital processes. Many high-performance technologies require integration using microelectromechanical systems (MEMS)-first or MEMS-last process schemes 8-10 , which provide space and power savings compared with off-chip RF integration. The use of phononic-crystal (PnC) confinement, however, could allow resonator integration directly into a standard complementary metal-oxide-semiconductor (CMOS) process, potentially leading to larger multiple-inputmultiple-output arrays in a smaller footprint at lower power . In addition to reducing parasitics from routing high-frequency signals over long distances, this also provides the opportunity to use high-performance transistors for active transduction, leading to potentially enhanced performance. Such an approach also provides a route to future acoustic coupling between devices co-located on the same chip, which reduces the need for power-hungry phase-locked loops and allows scaled coupled oscillator systems for neuromorphic computing to be explored . In this Article, we report CMOS fin field-effect transistor (FinFET)-based resonators that utilize acoustic waveguiding confinement operating in the Institute of Electrical and Electronics Engineers (IEEE) X-band of 8-12 GHz.

A tunable ferroelectric based unreleased RF resonator

arXiv (Cornell University), May 14, 2019

This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS ... more This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS resonator, integrated seamlessly in Texas Instruments' 130nm Ferroelectric RAM (FeRAM) technology. An array of FeCAPs in this complementary metal-oxide-semiconductor (CMOS) technology's back-end-of-line (BEOL) process were used to define the acoustic resonance cavity as well as the electromechanical transducers. To achieve high quality factor (Q) of the resonator, acoustic waveguiding for vertical confinement within the CMOS stack is studied and optimized. Additional design considerations are discussed to obtain lateral confinement and suppression of spurious modes. An FeCAP resonator is demonstrated with fundamental resonance at 703 MHz and Q of 1012. This gives a frequency-quality factor product 𝑓 • 𝑄 = 7.11 × 10 11 which is 1.6x higher than the most state-of-the-art Pb(Zr,Ti)O3 (PZT) resonators. Due to the ferroelectric characteristics of the FeCAPs, transduction of the resonator can be switched on and off by adjusting the electric polarization. In this case, the resonance can be turned off completely at ±0.3V corresponding to the coercive voltage of the constituent FeCAP transducers. These novel switchable resonators may have promising applications in on-chip timing, ad-hoc radio front ends, and chip-scale sensors.

A Ferroelectric Capacitor (Fecap) Based Unreleased Resonator

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

We present the first Pb(Zr,Ti)O3 (PZT)-transduced unreleased RF MEMS resonator embedded seamlessl... more We present the first Pb(Zr,Ti)O3 (PZT)-transduced unreleased RF MEMS resonator embedded seamlessly in CMOS. The unreleased resonators were realized by using Texas Instruments' Ferroelectric RAM (FeRAM) 130nm technology [1]. A new method of acoustic waveguiding within the CMOS stack was used to confine the resonance mode and an array of ferroelectric capacitors (FeCAPs) inherent to the technology was used as driving and sensing transducers. A resonance frequency of 722 MHz is observed with quality factor Q of 656 and electromechanical coupling coefficient keff 2 of 0.35%. This corresponds to f•Q of 4.7×10 11 , comparable to state-of-the-art PZT resonators [2]. These high Q, small footprint resonators offer a CMOS-integrated RF building block with no post-processing or costly packaging.

A mmWave Oscillator Design Utilizing High-Q Active-Mode On-Chip MEMS Resonators for Improved Fundamental Limits of Phase Noise

Recent progress in MEMS resonant-fin-transistors (RFT) allows very high-Q active mode resonators,... more Recent progress in MEMS resonant-fin-transistors (RFT) allows very high-Q active mode resonators, promising crystal-less monolithic clock generation for mmWave systems. However, there is a strong need for design of mmWave oscillators that utilize the high-Q of active-mode RFT (AM-RFT) optimally, while handling unique challenges such as resonator’s low electromechanical transduction. In this brief, we develop a theory and through design and post-layout simulations in 14-nm Global Foundry process, we show the first active oscillator with AM-RFT at 30 GHz, which improves the fundamental limits of phase noise and figure-of-merit as compared to the oscillators with conventional LC resonators. For AM-RFT with Q-factor of 10K, post layout simulation results show that the proposed oscillator exhibits phase noise <-140 dBc/Hz and figure-of-merit >228 dBc/Hz at 1 MHz offset for 30 GHz center frequency, which are >25 dB better than the existing monolithic LC oscillators. Keywords—Osci...

Switchable Mechanical Resonance Induced by Hysteretic Piezoelectricity in Ferroelectric Capacitors

This paper reports on a new switching and frequency hopping mechanism of electromechanical transd... more This paper reports on a new switching and frequency hopping mechanism of electromechanical transduction in ferroelectric capacitor (FeCAP) based CMOS-MEMS resonators implemented in Texas Instruments (TI) FeRAM technology. In this work, poling parameters are investigated to demonstrate bias-dependent pole/zero transitions accompanied by 180° phase shift in multiple mechanical modes of the device. To explain this behavior, the resonator Butterworth-Van Dyke (BVD) model is modified to account for nonlinear capacitance in the FeCAPs. The cancellation of motional branch current and feedthrough current between the Pb(Zr, Ti)O3 (PZT) thin layers with bias voltage enables switching of electromechanical transduction. These switchable, CMOS-integrated FeCAP resonators are solidly confined with no release step using Back-End-of-Line (BEOL) acoustic waveguiding. This study highlights the unique benefits of ferroelectric transducers for nonlinear, tunable MEMS devices, and offers a promising new...

X-Band Fin Resonant Body Transistors in 14nm CMOS Technology

Here we present the first demonstration and in-depth study of unreleased acoustic resonators in 1... more Here we present the first demonstration and in-depth study of unreleased acoustic resonators in 14nm FinFET technology in the IEEE X band, which offer a zero-barrier-to-entry solution for high Q, small footprint, resonant tanks integrated seamlessly in advanced CMOS nodes. These devices leverage phononic waveguides for acoustic confinement, and exploit MOS capacitors and transistors inherent to the technology to electromechanically drive and sense acoustic vibrations. Sixteen device variations are analyzed across thirty bias points to discern the impact of phononic confinement, gate length, and termination scheme on resonator properties. The limiting factor in FinFET resonator performance among design variations tested is shown to be Back End of Line (BEOL) confinement, with devices with acoustic waveguides incorporating Mx and Cx metal layers exhibiting 2.2x higher average quality factor (Q) and peak amplitude, with maximum Q increasing from 115 to 181 and maximum amplitude scaling...

Localized Modes in Asymmetric Phononic Crystals

This paper reports on a localized mechanical resonance induced by a novel phononic crystal (PnC) ... more This paper reports on a localized mechanical resonance induced by a novel phononic crystal (PnC) design demonstrated in a $1\ \mu \mathrm{m}$ aluminum nitride (AlN) thin film. An asymmetric PnC with diagonal beam bridging discs in a square lattice generates an isolated mode inside the PnC bandgap defined by the flexural mode of the connecting beam. Here we investigate the properties of the PnC dispersion relations as a function of key design parameters, defining resonance cavities to excite the localized mode. PnC resonators with localized mode at 156 MHz are characterized as a function of central bar rotation angle ($\theta$), number of actuation layers ($\mathrm{N}_{act}$) and lateral periods (P). This analysis of electromechanical modes with designed flat dispersion relation is an important first step toward Density-Near-Zero (DNZ) metamaterials and resilient elastic wave manipulation on chip.

Band Gap Structure of Two Dimensional Acoustic Metamaterials with Coated Double Hybrid Lattice

Acoustic metamaterials (phononic crystals) have received much recent attention. Over time, severa... more Acoustic metamaterials (phononic crystals) have received much recent attention. Over time, several efforts were proposed to improve the structure in order to enlarge the band gap, lower the band gap frequency, and/or generate greater attenuation of vibration. In this document, a novel two dimensional acoustic metamaterial with Coated Double Hybrid Lattice (CDHL) is proposed. The structure makes use of both the Bragg Scattering Theorem and the Local Resonance Theorem. In the simulation, both a lower frequency band gap and a higher frequency band gap are obtained. According to the modal analysis and phase spectrum analysis, it is proved that the lower frequency band gap is due to local resonance between the double lead cores and the rubber coating. At the same time, the higher frequency band gap is generated as a result of the interaction of Bragg scattering and local resonance effect. The variation in maximum vibration attenuation with respect to the position of the double central le...

32GHz resonant-fin transistors in 14nm FinFET technology

2018 IEEE International Solid - State Circuits Conference - (ISSCC)

Monolithic integration of microelectromechanical resonators in IC technology has been explored ex... more Monolithic integration of microelectromechanical resonators in IC technology has been explored extensively over the past few decades in the effort to achieve on-chip clocks, RF filters, and physical, chemical, and biological sensors. Various approaches for resonator integration, actuation, and sensing have been proposed and demonstrated, targeting high Q and high frequency performance [1]. These include the “MEMS-last” approach with low temperature materials deposited on complete CMOS chips [2,3], and “MEMS-in-the-middle” in which resonators are defined with post-processing of the front end and back end materials of the IC stack [4]. These methods require additional processing and packaging steps that make frequency scaling challenging and may limit resonator Q. Meanwhile, in the case of monolithically integrated MEMS resonators, transistor sensing can be used to enhance transduction efficiency and reduce parasitics, which can prohibit 2-port detection for high frequency resonance [5]. In this work, we introduce the Resonant Fin Transistor (RFT) fabricated in GLOBALFOUNDRIES 14nm FinFET technology, leveraging the vertical 3D geometry of FinFETs (Fig. 21.3.1) to efficiently confine, drive, and sense acoustic vibrations in the solid (unreleased) CMOS stack with no post-processing or custom packaging. We demonstrate 32GHz resonators with Q∼49,000.

Opportunities and challenges of 2D materials in back-end-of-line interconnect scaling

Journal of Applied Physics

As the challenges in continued scaling of the integrated circuit (IC) technology escalate every g... more As the challenges in continued scaling of the integrated circuit (IC) technology escalate every generation, there are urgent needs to find viable solutions for both the front-end-of-line (transistors) and the back-end-of-line (interconnects). For the interconnect technology, it is crucial to replace the conventional barrier and liner with much thinner alternatives so that the current driving capability of the interconnects can be maintained or even improved. Due to the inherent atomically thin body thicknesses, 2D materials have been proposed and explored as Cu diffusion barrier alternatives recently. In this Perspective article, a variety of 2D materials that have been studied, ranging from graphene, h-BN, MoS 2 , WSe 2 , to TaS 2 will be reviewed. Their potentials will be evaluated based on several criteria, including fundamental material properties as well as the feasibility for technology integration. Using TaS 2 as an example, we demonstrate a large set of promising properties and point out there remain challenges in the integration aspects with few possible solutions waiting for validation. Applications of 2D materials for other functions in Cu interconnects and for different metal types will also be introduced, including electromigration, cobalt interconnects, and RF transmission lines. I. Introduction: Copper (Cu) has been the material of choice for interconnects in today's IC chips for more than 20 years. Before the integration scheme for Cu interconnects was available, aluminum (Al) was used as metal interconnects. However, with increasing demands of lower resistivity and better electromigration endurance, Al was eventually replaced with Cu in late 1990s, after many integration challenges had been solved. Overviews of the technology development can be found in refs. 1 and 2. Although Cu offers the advantage of improving interconnect performance, its high diffusivity results in diffusion of Cu atoms/ions into the surrounding dielectric that isolates individual Cu interconnect wires, causing circuit shorting and chip failure 3-6. To prevent this, TaN has been adopted as the "diffusion barrier" to block Cu diffusion 7,8. While possessing a decent diffusion barrier property, the adhesion between TaN and Cu is not ideal. Therefore, Ta has been introduced as the "liner" between Cu and TaN to improve the adhesion 7,8. The schematic of basic interconnect structures is shown in _____________________________

A Ferroelectric Capacitor (Fecap) Based Unreleased Resonator

2018 Solid-State, Actuators, and Microsystems Workshop Technical Digest, May 21, 2018

We present the first Pb(Zr,Ti)O3 (PZT)-transduced unreleased RF MEMS resonator embedded seamlessl... more We present the first Pb(Zr,Ti)O3 (PZT)-transduced unreleased RF MEMS resonator embedded seamlessly in CMOS. The unreleased resonators were realized by using Texas Instruments' Ferroelectric RAM (FeRAM) 130nm technology [1]. A new method of acoustic waveguiding within the CMOS stack was used to confine the resonance mode and an array of ferroelectric capacitors (FeCAPs) inherent to the technology was used as driving and sensing transducers. A resonance frequency of 722 MHz is observed with quality factor Q of 656 and electromechanical coupling coefficient keff 2 of 0.35%. This corresponds to f•Q of 4.7×10 11 , comparable to state-of-the-art PZT resonators [2]. These high Q, small footprint resonators offer a CMOS-integrated RF building block with no post-processing or costly packaging.

Experimental Study of the Transmission Spectrum of a Sonic/Ultrasonic Acoustic Metamaterial

Volume 13: Acoustics, Vibration, and Wave Propagation, 2016

Acoustic metamaterials have received much attention recently. In the past decades, countless stru... more Acoustic metamaterials have received much attention recently. In the past decades, countless structures have been studied for their novel physical phenomenon or potential applications. The goals of many of the works were to explore ways to enlarge the band gap, lower the band gap frequency, and/or generate greater attenuation of vibration. However, most of the work was limited to simulation, with experimental studies rarer. In this work, we would like to experimentally present the transmission spectrum of an acoustic metamaterial with a proposed structure called the coated double hybrid lattice (CDHL) [1]. The CDHL has both crystalline structure and local resonators, which provide high-frequency and low-frequency band gaps, respectively. A structure was fabricated and tested to experimentally determine the transmission spectrum. Both, a higher frequency band gap and a lower frequency band gap, were obtained. Vibration is clearly attenuated in the frequency range of 70–90 kHz. This is due to the Bragg scattering effect. At the same time, around the frequency of 4.8kHz, another band gap is observed which is attributed to local resonance. It turns out that our experimental results coincide with our previous simulation quite well.Copyright © 2016 by ASME

A tunable ferroelectric based unreleased RF resonator

Microsystems & Nanoengineering

This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS ... more This paper introduces the first tunable ferroelectric capacitor (FeCAP)-based unreleased RF MEMS resonator, integrated seamlessly in Texas Instruments’ 130 nm Ferroelectric RAM (FeRAM) technology. The designs presented here are monolithically integrated in solid-state CMOS technology, with no post-processing or release step typical of other MEMS devices. An array of FeCAPs in this complementary metal-oxide-semiconductor (CMOS) technology’s back-end-of-line (BEOL) process were used to define the acoustic resonance cavity as well as the electromechanical transducers. To achieve high quality factor (Q) of the resonator, acoustic waveguiding for vertical confinement within the CMOS stack is studied and optimized. Additional design considerations are discussed to obtain lateral confinement and suppression of spurious modes. An FeCAP resonator is demonstrated with fundamental resonance at 703 MHz and Q of 1012. This gives a frequency-quality factor product $$f \cdot Q = 7.11 \times 10^{11...