Thermomechanical Noise Characterization in Fully Monolithic CMOS-MEMS Resonators

Abstract

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.

A Low-g MEMS Accelerometer with High Sensitivity, Low Nonlinearity and Large Dynamic Range Based on Mode-Localization of 3-DoF Weakly Coupled Resonators

“…As discussed previously in [20] and also evident from Equations (14) and (23), both the amplitude and frequency response of the 3-DoF weakly coupled resonators is strongly dependent on the effective stiffness of the resonators. Figure 10a shows the effect of increasing tuning voltage on the amplitude ratio of outer and inner resonators in resonator Set A.…”

“…The thermomechanical noise developed due to dynamic equilibrium between the mechanical energy of the resonator and thermal energy of the surroundings is considered to be the fundamental noise factor for the MEMS resonators within 3 dB bandwidth [20]. Assuming that the noise in the inner resonators in both Set A and Set B is Gaussian and 3 dB bandwidth for a resonator is very less than the resonant frequency i. e. , ∆ << , displacement in the resonator caused only by the thermomechanical noise can be expressed as [23] The minimum detectable amplitude for a resonator is limited by the amplitude fluctuations due to noise in the system. The thermomechanical noise developed due to dynamic equilibrium between the mechanical energy of the resonator and thermal energy of the surroundings is considered to be the fundamental noise factor for the MEMS resonators within 3 dB bandwidth [20].…”

“…The thermomechanical noise developed due to dynamic equilibrium between the mechanical energy of the resonator and thermal energy of the surroundings is considered to be the fundamental noise factor for the MEMS resonators within 3 dB bandwidth [20]. Assuming that the noise in the inner resonators in both Set A and Set B is Gaussian and 3 dB bandwidth for a resonator is very less than the resonant frequency i.e., ∆ f 3dB << f r , displacement in the resonator caused only by the thermomechanical noise can be expressed as [23] x noise…”

Impact of Fluid Flow on CMOS-MEMS Resonators Oriented to Gas Sensing

“…The mechanical resonators used in this work were fabricated on CMOS 0.35 μm commercial technology with an additional final step performed at our lab facilities consisting of a post-CMOS mask-less wet-etch to remove the sacrificial oxide underneath the structure by using a commercial etchant; further details about the fabrication process were provided previously [ 22 ]. The technology used had four metal layers based on an aluminum composite with a TiN film; the top one was used as the resonator structural layer as it provided the larger thickness, thus resulting in a larger capacitive coupling [ 6 ].…”

Manufacturing and Testing of Radio Frequency MEMS Switches Using the Complementary Metal Oxide Semiconductor Process

“…The CMOS-MEMS technology was used to develop microactuators [ 18 , 19 , 20 , 21 ], microsensors [ 22 , 23 , 24 , 25 ], and microgenerators [ 26 ]. Micro devices developed by this technology have a potential to mass-production by silicon manufacturing foundry.…”