Film-bulk acoustic wave resonator with motion plate

Abstract

The present invention discloses an apparatus and method for measuring a target environmental variable (TEV) using a thin film bulk acoustic resonator with a moving plate. The film bulk acoustic resonator (FBAR) includes an acoustic reflector having a surface formed in the FBAR wafer. The first electrode is formed on a surface of the acoustic reflector and has a surface. The piezoelectric layer is formed on the surface of the first electrode and has one surface. The second electrode is formed on the surface of the piezoelectric layer. The motion board is suspended in air at a predetermined distance relative to the surface of the second electrode and is capacitively coupled to the FBAR.

Description

technical field [0001] The present invention relates to thin film bulk acoustic resonators with moving plates. Background technique [0002] Capacitive pressure sensors are well known in the art. A typical pressure sensor includes a fixed element having a rigid planar conductive surface forming one plate of a substantially parallel plate capacitor. A displaceable (relative to the fixed element) conductive member, such as a metal diaphragm, or a plated non-conductive member, such as a metallized ceramic diaphragm, forms the other plate of the capacitor. [0003] The diaphragm is supported along the edges so that the central portion is substantially parallel to and opposite the stationary plate. Because the sensor generally has the form of a plate capacitor, the characteristic capacitance C of the sensor can be approximated by the following formula: C=(ε*A) / d, where ε is the dielectric constant of the material between the parallel plates, and A is the parallel The surface a...

AI Technical Summary

Problems solved by technology

[0008] A disadvantage of capacitive pressure sensors utilizing this configuration is that the oscillator circuit operates at a lower resonant frequency

Another disadvantage of capacitive pressure sensors utilizing this configuration is that the fabrication of the sensor capacitor and oscillator circuit is often complex

[0009] A further disadvantage of existing capacitive pressure sensors is that the resulting sensor capacitors and tank circuits are often bulky and space-inefficient

Therefore, these existing capacitive pressure sensors cannot meet the demanding size and space requirements of portable applications or other compact applications

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