J. Verd

Monolithic CMOS MEMS Oscillator Circuit for Sensing in the Attogram Range

This letter presents the design, fabrication, and demonstration of a CMOS/microelectromechanical system (MEMS) electrostatically self-excited resonator based on a submicrometer-scale cantilever with ~1 ag/Hz mass sensitivity. The mechanical resonator is the frequency-determining element of an oscillator circuit monolithically integrated and implemented in a commercial 0.35 mum CMOS process. The oscillator is based on a Pierce topology adapted for the MEMS resonator that presents a mechanical resonance frequency of ~6 MHz, a relative low quality factor of 100, and a large motional resistance of ~25 M. The MEMS oscillator has a frequency stability of ~1.6 Hz resulting in a mass resolution of ~1 ag (1 ag = 10-18 g in air conditions.

Ultrasensitive mass sensor fully integrated with complementary metal-oxide-semiconductor circuitry

Nanomechanical resonators have been monolithically integrated on preprocessed complementary metal-oxide-semiconductor (CMOS) chips. Fabricated resonator systems have been designed to have resonance frequencies up to 1.5 MHz. The systems have been characterized in ambient air and vacuum conditions and display ultrasensitive mass detection in air. A mass sensitivity of 4 ag/Hz has been determined in air by placing a single glycerine drop, having a measured weight of 57 fg, at the apex of a cantilever and subsequently measuring a frequency shift of 14.8 kHz. CMOS integration enables electrostatic excitation, capacitive detection, and amplification of the resonance signal directly on the chip.

Integration of RF-MEMS resonators on submicrometric commercial CMOS technologies

Integration of electrostatically driven and capacitively transduced MEMS resonators in commercial CMOS technologies is discussed. A figure of merit to study the performance of different structural layers and different technologies is defined. High frequency (HF) and very high frequency (VHF) resonance MEMS metal resonators are fabricated on a deep submicron 0.18 µm commercial CMOS technology and are characterized using electrical tests without amplification, demonstrating the applicability of the MEMS fabrication process for future technologies. Moreover, the fabricated devices show comparable performance in terms of Q × fres with previously presented MEMS resonators, whereas the small gap allows obtaining a low motional resistance with a single resonator approach.

Integrated CMOS-MEMS with on-chip readout electronics for high-frequency applications

A bridge-shaped first-lateral-mode 60-MHz mechanical resonator, which is monolithically integrated with capacitive CMOS readout electronics, is presented. The resonator is fabricated directly on a commercial CMOS technology using the top metal level as a structural layer. A maskless single-step wet-etching process for mechanical structure release after the standard CMOS integration process is the only postfabrication requirement. Electrical characterization of the electromechanical device demonstrates the feasibility of implementing a CMOS-microelectromechanical system for high-frequency applications using a standard conventional CMOS technology.

Design, fabrication, and characterization of a submicroelectromechanical resonator with monolithically integrated CMOS readout circuit

In this paper, we report on the main aspects of the design, fabrication, and performance of a microelectromechanical system constituted by a mechanical submicrometer scale resonator (cantilever) and the readout circuitry used for monitoring its oscillation through the detection of the capacitive current. The CMOS circuitry is monolithically integrated with the mechanical resonator by a technology that allows the combination of standard CMOS processes and novel nanofabrication methods. The integrated system constitutes an example of a submicroelectromechanical system to be used as a cantilever-based mass sensor with both a high sensitivity and a high spatial resolution (on the order of 10/sup -18/ g and 300 nm, respectively). Experimental results on the electrical characterization of the resonance curve of the cantilever through the integrated CMOS readout circuit are shown.

Monolithic mass sensor fabricated using a conventional technology with attogram resolution in air conditions

Monolithic mass sensors for ultrasensitive mass detection in air conditions have been fabricated using a conventional 0.35μm complementary metal-oxide-semiconductor (CMOS) process. The mass sensors are based on electrostatically excited submicrometer scale cantilevers integrated with CMOS electronics. The devices have been calibrated obtaining an experimental sensitivity of 6×10−11g∕cm2Hz equivalent to 0.9ag∕Hz for locally deposited mass. Results from time-resolved mass measurements are also presented. An evaluation of the mass resolution have been performed obtaining a value of 2.4×10−17g in air conditions, resulting in an improvement of these devices from previous works in terms of sensitivity, resolution, and fabrication process complexity.

A CMOS–MEMS RF-Tunable Bandpass Filter Based on Two High-

This letter presents the design, fabrication, and demonstration of a CMOS-MEMS filter based on two high-Q submicrometer-scale clamped-clamped beam resonators with resonance frequency around 22 MHz. The MEMS resonators are fabricated with a 0.35-mum CMOS process and monolithically integrated with an on-chip differential amplifier. The CMOS-MEMS resonator shows high-quality factors of 227 in air conditions and 4400 in a vacuum for a bias voltage of 5 V. In air conditions, the CMOS-MEMS parallel filter presents a programmable bandwidth from 100 to 200 kHz with a <1-dB ripple. In a vacuum, the filter presents a stop-band attenuation of 37 dB and a shape factor as low as 2.5 for a CMOS-compatible bias voltage of 5 V, demonstrating competitive performance compared with the state of the art of not fully integrated MEMS filters.

Q

A resonator system has been fabricated directly on a pre-processed CMOS chip. The system is to be used for high sensitivity mass sensing applications in air and vacuum. The resonator system, corresponding of a cantilever and structures for electrostatic actuation and capacitive read-out, have been defined by electron beam lithography on top of a charge and radiation sensitive CMOS layer in predefined areas as a post-process step. This has been accomplished without affecting the electronic properties of the pre-processed CMOS circuits. The subsequent etching steps to fully release the cantilevers have been obtained without stiction of the cantilevers to the substrate. Cantilevers are driven at their mechanical resonance in a lateral mode, and the frequency is monitored by capacitive read-out on the chip. CMOS integration enables signal detection directly on the chip, which radically decreases the parasitic capacitances. Consequently, low-noise electrical measurements with a very high mass sensitivity are obtained. Fabricated resonator systems were characterized to have resonance frequencies of approximately 1.49 MHz, which is in good agreement with a theoretical estimation of 1.41 MHz. The theoretical mass resolution, partial derivativem/partial derivativef, is approximately 17 ag Hz(-1) using a Young modulus value of 160 GPa. (Less)

22-MHz Polysilicon Clamped-Clamped Beam Resonators

Keywords: mass sensors ; nanoelectromechanical systems ; nanolithography ; nanomechanical sensors ; High-Frequency Applications ; Cmos-Mems ; Devices Reference LMIS1-ARTICLE-2009-006doi:10.1002/smll.200990007View record in Web of Science Record created on 2009-01-28, modified on 2017-05-10

Resonators with integrated CMOS circuitry for mass sensing applications, fabricated by electron beam lithography

Miniaturization of cantilever dimensions will increase both the mass and spatial resolution of a resonating cantilever-based mass sensor, which monitors the mass change of the cantilever by measuring its resonant frequency shift. A fabrication method for nanometer-sized cantilevers with electrostatic excitation and integrated capacitive readout is introduced. The dynamic behavior of the nanometer-sized cantilever is characterized at atmospheric pressure using optical microscopy and in vacuum using scanning electron microscopy (SEM). A monolithic integration method for combining the nano-cantilevers with CMOS circuitry is described in detail. The circuitry is used to enhance the capacitive readout. The fabrication results, showing integrated nano-cantilevers with a CMOS analog amplification circuit, are presented along with preliminary electrical characterization of the device.