High‐sensitivity surface micromachinable accelerometer using a ferroelectric substrate and its characterization

Abstract

The present study reports the fabrication and characterization of a high-sensitivity surface micromachinable accelerometer using a ferroelectric material having a large dielectric constant, such as bulk PZT (ε r = 2600). The measurement principle is the detection of capacitance change with respect to the dielectric mass movement in the fringe electrical field. Considering the practical fabrication, a ferroelectric material is used for the substrate instead of the suspended proof mass. Since capacitance is increased not mechanically but electrically, high sensitivity can be expected while maintaining mechanical stiffness, which has the advantage of preventing touch down of the proof mass and widening the allowable measuring range of acceleration. A fabricated sensor is characterized. A high sensitivity of several sub-pF/g is confirmed, which is hundreds of times higher compared to that of a sensor fabricated using the Parylene polymer (ε r = 3.15). This sensitivity is an order higher compared to those of other reported capacitive microaccelerometers, which have comparable proof mass sizes and comparable detectable acceleration ranges to the newly fabricated sensor. 

Fabrication of micro accelerometer and magnetoresistive sensor directly on a ceramic substrate

“…(2) Measurement results are shown in table 2. The sensitivity of the fabricated accelerometer was 0.1 pF g −1 , the order of which is the same as that of the previously developed accelerometer using a PZT substrate (0.4 pF g −1 ) [1].…”

“…We have already proposed a new type accelerometer, which uses a ferroelectric material and its fringe capacitance, as shown in figure 2 [1]. There is an interdigitized pair of comb-shaped anode and cathode electrodes under an insulating proof mass, and the fringe electrical field between the two electrodes is used in order to detect the acceleration input to this sensor.…”

“…Therefore, it is important to use highly dielectric material for this sensor. In our previous study on the accelerometer, the capacitors are fabricated on a bulk ferroelectric plate of lead zirconium titanate (PZT) (Pb(Zr, Ti)O 3 , ε r is approximately 2600) for enhancing the sensitivity of accelerometer (figure 2) [1]. However, the fabrication cost was high because the PZT plate is expensive.…”

Micro accelerometer using screen printed BaTiO<inf>3</inf> film on ceramic substrate

“…The output of the accelerometer was measured by an Table 4. The sensitivity of the fabricated accelerometer was 0.1 pF/G, the order of which is the same as that of the previously developed accelerometer using a PZT substrate (0.4 pF/g) [4]. However, the sensitivity was degraded by approximately 1/4.…”

“…In previous, we have proposed a new type capacitive accelerometer, which consists of a dielectric proof mass and comb-shaped planer capacitors [3,4]. In the accelerometer, the capacitors are fabricated on a ferroelectric Pb(Zr,Ti)O 3 (PZT) substrate and its fringe capacitance enhances sensitivity of the accelerometer as shown in Fig.…”