A digital output accelerometer using MEMS-based piezoelectric accelerometers and arrayed CMOS inverters with satellite capacitors

Abstract

The present paper describes the development of a digital output accelerometer composed of microelectromechanical systems (MEMS)-based piezoelectric accelerometers and arrayed complementary metal-oxide-semiconductor (CMOS) inverters accompanied by capacitors. The piezoelectric accelerometers were fabricated from multilayers of Pt/Ti/PZT/Pt/Ti/SiO 2 deposited on silicon-on-insulator (SOI) wafers. The fabricated piezoelectric accelerometers were connected to arrayed CMOS inverters. Each of the CMOS inverters was accompanied by a capacitor with a different capacitance called a 'satellite capacitor'.We have confirmed that the output voltage generated from the piezoelectric accelerometers can vary the output of the CMOS inverters from a high to a low level; the state of the CMOS inverters has turned from the 'off-state' into the 'on-state' when the output voltage of the piezoelectric accelerometers is larger than the threshold voltage of the CMOS inverters. We have also confirmed that the CMOS inverters accompanied by the larger satellite capacitor have become 'on-state' at a lower acceleration. On increasing the acceleration, the number of on-state CMOS inverters has increased.Assuming that the on-state and off-state of CMOS inverters correspond to logic '0' and '1', the present digital output accelerometers have expressed the accelerations of 2.0, 3.0, 5.0, and 5.5 m s −2 as digital outputs of 111, 110, 100, and 000, respectively.

A Simple Analytical Model for MEMS Cantilever Beam Piezoelectric Accelerometer and High Sensitivity Design for SHM (structural health monitoring) Applications

“…Piezoelectric accelerometers have many desirable features, such as extremely low power consumption, high sensitivity, inherent temperature stability, compatibility with the CMOS (complementary metal-oxide semiconductor) manufacturing process [8][9][10], high Q in the range of 80 to 100, high output impedance, and wide operating temperature range (up to 300℃) [8,11,12]. The design and fabrication of micromachined piezoelectric accelerometers have been reported widely [7][8][9][10][11][12][13][14]. Such an accelerometer will record translational and rotational inertial accelerations, as well as gravitational acceleration, as long as parts of these acceleration vectors are in line with the accelerometer's axis of sensitivity.…”

“…From equation (14), it can be seen that the induced voltage, V in (x) is a non-linear function with respect to distance and reaches maximum at the fixed end as shown in Fig. 2.…”

“…By integrating E in (x, z) with respect to z, the induced voltage at any given x is then (14) for 0<x<L. Here,…”

“…Peak Voltage (14) for 0<x<L. Here, and piezoelectric layers, respectively. In order to calculate the tip displacement of the cantilever, the following boundary condition has been used: the axial displacement and its first derivative are zero at the fixed end.…”

“…The design and fabrication of micromachined piezoelectric accelerometers have been reported widely [7][8][9][10][11][12][13][14]. Such an accelerometer will record translational and rotational inertial accelerations, as well as gravitational acceleration, as long as parts of these acceleration vectors are in line with the accelerometer's axis of sensitivity.…”