Analysis and Modeling of an 11.8 GHz Fin Resonant Body Transistor in a 14 nm FinFET CMOS Process.

In this work, a compact model is presented for a 14-nm CMOS-based fin resonant body transistor (fRBT) operating at a frequency of 11.8 GHz and targeting radio frequency (RF) generation/filtering for next-generation radio communication, clocking, and sensing applications. Analysis of the phononic dispersion characteristics of the device, which informs the model development, shows the presence of displacement component coupling due to the periodic nature of the back-end-of-line (BEOL) metal phononic crystal (PnC). An eigenfrequency-based extraction process, applicable to resonators based on electrostatic force transduction, has been used to model the resonance cavity. Augmented forms of the Berkeley short channel IGFET model (BSIM)-common multigate (CMG) model for FinFETs are used to model the drive and sense transistors in the fRBT. This model framework allows easy integration with the foundry-supplied process design kits (PDKs) and circuit simulators while being flexible toward change in transduction mechanisms and device architecture. Ultimately, the behavior is validated against RF measured data for the fabricated fRBT device under different operating conditions, leading to the demonstration of the first complete model for this class of resonant device integrated seamlessly in the CMOS stack.

A tunable ferroelectric based unreleased RF resonator.

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 ⋅ Q = 7.11 × 1 0 11 which is 1.6× 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 ±0.3 V 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.

Temperature coefficient of frequency modeling for CMOS-MEMS bulk mode composite resonators.

CMOS-MEMS resonators, which are promising building blocks for achieving monolithic integration of MEMS structure, can be used for timing and filtering applications, and control circuitry. SiO2 has been used to make MEMS resonators with quality factor Q > 10(4), but temperature instability remains a major challenge. In this paper, a design that uses an embedded metal block for temperature compensation is proposed and shows sub-ppm temperature stability (-0.21 ppm/K). A comprehensive analytical model is derived and applied to analyze and optimize the temperature coefficient of frequency (TCF) of the CMOS-MEMS composite material resonator. Comparison with finite element method simulation demonstrates good accuracy. The model can also be applied to predict and analyze the TCF of MEMS resonators with arbitrary mode shape, and its integration with simulation packages enables interactive and efficient design process.