Micro accelerometer using screen printed BaTiO3 film on ceramic substrate

The concept of MEMS sensors directly fabricated on a ceramic substrate, which can be used for a package of end product, was proposed. A micro accelerometer utilizing a fringe capacitance formed in a ferroelectric substrate was focused on. For this sensor, in stead of a previously used bulk PZT plate, a screen-printed BaTiO₃ (BTO) film on an alumina substrate was employed in this study. A screen-printing method can save the amount of raw material of the film, because a comparatively thick film can be deposited only on a specified area. Moreover, BTO does not contain harmful lead material. The optimal condition for fabricating a BTO film with minimum unwanted surface defects was experimentally searched. The number of defects was decreased by employing a metal barrier of Pt layer underneath BTO, and by setting the annealing temperature for crystallization to a higher value of 1,400degC. A comparatively high relative dielectric constant of epsiv_r =926 was achieved. An accelerometer using a BTO film was practically fabricated. The sensitivity of it was estimated as 0.1 pF/G, the order of which is the same as the previously developed accelerometer using a PZT plate.