Exploitation and scaling of monolithic non-linear CMOS-M/NEMS device characteristics for specific "More Moore" and "More than Moore" applications (KEYNEMS)
The main Project goal is related to demonstrating the feasibility and scaling capabilities of a highly secure monolithic CMOS N/MEMS system that would allow the encryption and transmission of ultrasensitive information through ordinary channels for absolutely inviolable information. Such system is based on developing chaotic CMOS N/MEMS resonators tuned through a system variable impossible of being determined through reverse engineering. The project is aimed at exploring the capabilities of current technologies to develop chaotic CMOS N/MEMS oscillators or compact systems solutions exhibiting much higher performance than the ones obtained up to date, enabling its use in compact security-by-design solutions based on chaos. The main advantage of the system proposed over existing techniques (fully-electronic chaotic circuits or optically-based chaotic systems) is related to its intrinsic secureness against copying or replication.
J. Barcelo, S. Bota, J. Segura, J. Verd
Sensors and Actuators A: Physical, Vol. 272, pp. 33-41, April 2018.
https://doi.org/10.1016/j.sna.2018.01.046
Microelectromechanical resonators nonlinearities can be exploited in many ways to obtain a set of diverse new applications. In particular, some applications of bistable behavior includes threshold mechanical switches, memory cells, energy harvesting and chaotic signal generators. A key step for practical and efficient design for bistability behavior involves accounting for accurate and efficient models. In this paper we present a nonlinear electromechanical model for capacitive clamped-clamped beam resonators implemented in an analog hardware description language (AHDL) enabling system level electrical simulations. The model accounts for nonlinearities from variable resonator-electrode gap, residual fabrication stress, fringing field contributions as well as an accurate resonator deflection profile in contrast to parallel plate approximations. The model has been applied to derive for first time accurate analytical expressions for bistability design conditions. The work includes FEM analysis and experimental data that corroborates the correctness of the model in describing the required bias voltage conditions for bistability.
J. Barcelo, S. Bota, J. Segura and J. Verd
The 31st IEEE International Conference on Micro Electro Mechanical Systems
21-25 January 2018.
Experimental demonstration of bistability in simple, straight and non-axially-forced clamped-clamped microbeam resonators in the MHz range is reported for the first time. Experimental measurements have been also used to validate a nonlinear electromechanical model for microbeam resonators and its tuning procedure through the thermal effect. The model is used to obtain the design and biasing conditions to achieve bistability is such devices. The measured devices were fabricated and monolithically integrated with readout circuitry using a commercial 0.35-μm CMOS technology resulting in a low-cost platform to investigate potential applications of bistability in MEMS devices.
R. Perello-Roig, J. Verd, S. Bota, J. Segura
IEEE Int. Symp. on Cicuits and Systems (ISCAS18), May 27-30, 2018.
We measured the frequency stability of fully integrated self-sustained CMOS-MEMS oscillators and compared it with the theoretical thermomechanical limit. Experimental data obtained from a fully CMOS compatible CC-Beam MEMS resonator with on-chip capacitive readout and electrostatic excitation in open- and closed-loop configuration is provided. Our results show that the frequency stability is 2 ppm in ambient air conditions for an integration time of 40ms and 0.6 ppm in vacuum, being only two times larger than the ultimate limit set by the thermomechanical vibrations.
J. Barcelo, I. de Paul, S. Bota, J. Segura and J. Verd
IEEE Int. Symp. on Cicuits and Systems (ISCAS18), May 27-30, 2018.
A nonlinear electromechanical model for microbeam resonators and its tuning procedure through the thermal effect is presented in this work and compared with experimental results that allows stating the conditions to achieve bistability. Furthermore, the bistable behaviour of a submicrometer scale CMOS-MEMS resonator is experimentally demonstrated for first time as far we know.
R. Perello-Roig, J. Verd, S. Bota and J. Segura
Sensors 2018, 18, 3124; doi:10.3390/s18093124
We analyzed experimentally the noise characteristics of fully integrated CMOS-MEMS resonators to determine the overall thermomechanical noise and its impact on the limit of detection at the system level. Measurements from four MEMS resonator geometries designed for ultrasensitive detection operating between 2-MHz and 8-MHz monolithically integrated with a low-noise CMOS capacitive readout circuit were analyzed and used to determine the resolution achieved in terms of displacement and capacitance variation. The CMOS-MEMS system provides unprecedented detection resolution of 11 yF/(Hz)1/2 equivalent to a minimum detectable displacement (MDD) of 13 fm/(Hz)1/2, enabling noise characterization that is experimentally demonstrated by thermomechanical noise detection and compared to theoretical model values.