Sunil A. Bhave

The Resonant Body Transistor

This paper introduces the resonant body transistor (RBT), a silicon-based dielectrically transduced nanoelectromechanical (NEM) resonator embedding a sense transistor directly into the resonator body. Combining the benefits of FET sensing with the frequency scaling capabilities and high quality factors (Q) of internal dielectrically transduced bar resonators, the resonant body transistor achieves >10 GHz frequencies and can be integrated into a standard CMOS process for on-chip clock generation, high-Q microwave circuits, fundamental quantum-state preparation and observation, and high-sensitivity measurements. An 11.7 GHz bulk-mode RBT is demonstrated with a quality factor Q of 1830, marking the highest frequency acoustic resonance measured to date on a silicon wafer.

Fully-differential poly-SiC Lame mode resonator and checkerboard filter

In this paper, we report the first fully-differential, electrostatically transduced RF MEMS resonator. The fully-differential electrode configuration not only cancels capacitive feedthrough between the drive and sense terminals but also eliminates the reduction in electromechanical quality factor (Q) from the large ohmic resistance of the polycrystalline silicon carbide (poly-SiC) suspension and anchor. Using this configuration, we have demonstrated a 173 MHz poly-SiC Lame-mode resonator with a Q of 9,300 in air. By mechanically coupling five Lame-mode resonators into a 2-D checkerboard, we have realized a 173 MHz center frequency band-pass filter with 110 kHz bandwidth and < 2 dB pass-band ripple.

Mechanical spin control of nitrogen-vacancy centers in diamond.

We demonstrate direct coupling between phonons and diamond nitrogen-vacancy (NV) center spins by driving spin transitions with mechanically generated harmonic strain at room temperature. The amplitude of the mechanically driven spin signal varies with the spatial periodicity of the stress standing wave within the diamond substrate, verifying that we drive NV center spins mechanically. These spin-phonon interactions could offer a route to quantum spin control of magnetically forbidden transitions, which would enhance NV-based quantum metrology, grant access to direct transitions between all of the spin-1 quantum states of the NV center, and provide a platform to study spin-phonon interactions at the level of a few interacting spins.

Dielectrically Transduced Single-Ended to Differential MEMS Filter

A single-ended input to balanced output 425MHz mechanically coupled electromechanical filter is presented. This technology provides 1MHz channel select filtering while eliminating the need for RF switches and baluns in front-end transceivers. The filter achieves 8dB insertion loss with -50dB stop-band rejection and -48dB common-mode suppression

A modular process for integrating thick polysilicon MEMS devices with sub-micron CMOS

A new MEMS process module, called Mod MEMS, has been developed to monolithically integrate thick (5-10um), multilayer polysilicon MEMS structures with sub-micron CMOS. This process is particularly useful for advanced inertial MEMS products such as automotive airbag accelerometers where reduced cost and increased functionality is required, or low cost, high performance gyroscopes where thick polysilicon (>6um) and CMOS integration is required to increase poly mass and stiffness, and reduce electrical parasitics in order to optimize angular rate sensing. In this paper we will describe the new modular process flow, development of the critical unit process steps, integration of the module with a foundry sub-micron CMOS process, and provide test data on several inertial designs fabricated with this process.

Internal Dielectric Transduction of a 4.5 GHz Silicon Bar Resonator

This paper presents experimental verification of frequency scaling in an internal dielectric transduced resonator. A silicon bar resonator is excited in its 3rd and 9th longitudinal harmonic modes at 1.53 and 4.51 GHz, respectively. The resonator demonstrates a 2 dB improvement in transduction efficiency in its 9th harmonic relative to its 3rd harmonic, normalized to the quality Q of the resonance. This result is in close agreement with theory, promising low- impedance transduction of silicon bulk acoustic resonators at frequencies exceeding 10 GHz.

Internal Dielectric Transduction in Bulk-Mode Resonators

This paper investigates electrostatic transduction of a longitudinal-mode silicon acoustic resonator with internal dielectric films. Geometric optimization of internal dielectrically transduced resonators is derived analytically and shown experimentally. Analysis of internal dielectric transduction shows a maximum transduction efficiency with thin dielectric films at points of maximum strain of the desired resonant mode. With this design optimization, a silicon bar resonator is realized with a ninth harmonic resonance of 4.5 GHz and a quality factor of over 11 000, resulting in a record high f middotQ product in silicon of 5.1 times 1013. The novel dielectric transducer demonstrates improved resonator performance with increasing frequency, with optimal transduction efficiency when the acoustic wavelength is twice the dielectric thickness. Such frequency scaling behavior enables the realization of resonators up to the super-high-frequency domain.

A monolithic radiation-pressure driven, low phase noise silicon nitride opto-mechanical oscillator

Cavity opto-mechanics enabled radiation pressure (RP) driven oscillators shown in the past offer an all optical Radio Frequency (RF) source without the need for external electrical feedback. However these oscillators require external tapered fiber or prism coupling and non-standard fabrication processes. In this work, we present a CMOS compatible fabrication process to design high optical quality factor opto-mechanical resonators in silicon nitride. The ring resonators designed in this process demonstrate low phase noise RP driven oscillations. Using integrated grating couplers and waveguide to couple light to the micro-resonator eliminates 1/f(3) and other higher order phase noise slopes at close-to-carrier frequencies present in previous demonstrations. We present an RP driven opto-mechanical oscillator (OMO) operating at 41.97 MHz with a signal power of -11 dBm and phase noise of -85 dBc/Hz at 1 kHz offset with only 1/f(2) noise down to 10 Hz offset from carrier.

Performance comparison of Pb(Zr0.52Ti0.48)O3-only and Pb(Zr0.52Ti0.48)O3-on-silicon resonators

This paper provides a quantitative comparison and explores the design space of lead zirconium titanate (PZT)–only and PZT-on-silicon length-extensional mode resonators for incorporation into radio frequency microelectromechanical system filters and oscillators. We experimentally measured the correlation of motional impedance (RX) and quality factor (Q) with the resonators’ silicon layer thickness (tSi). For identical lateral dimensions and PZT-layer thicknesses (tPZT), the PZT-on-silicon resonator has higher resonant frequency (fC), higher Q (5100 versus 140), lower RX (51 Ω versus 205 Ω), and better linearity [third-order input intercept point (IIP3) of +43.7 dBm versus +23.3 dBm]. In contrast, the PZT-only resonator demonstrated much wider frequency tuning range (5.1% versus 0.2%).

Silicon nitride-on-silicon bar resonator using internal electrostatic transduction

This paper demonstrates an electrostatic transducer for lateral-mode bar resonators in which a high dielectric constant (high-K) thin film is sandwiched between polysilicon electrodes and the top surface of the resonator. This internal electrostatic transducer has several advantages over both air-gap electrostatic and piezoelectric transduction, including lower motional impedance (R/sub x/), compatibility with advanced scaled CMOS device technology, and extended dynamic range. The resonators are fabricated on 4 /spl mu/m thick heavily-doped SOI wafers with 200 nm thick silicon nitride film as the dielectric transducer. Using this configuration, we have demonstrated a 121 MHz silicon nitride-on-silicon lateral-mode bar resonator with a quality factor (Q) of 2,100 in air and motional impedance of 9 k/spl Omega/.