Lead zirconate titanate (PZT) thin films in surface-micromachined sensor structures

Abstract

The suitability of ferroelectric lead zirconate titanate (PZT) thin films for use in microsensor structures is demonstrated. Sensors based on the integration of surface micromachining techniques with sol-gel deposition of PZT films have been fabricated and show promise for sensing schemes based on direct charge detection. The piezoelectric coupling coefficients are between one and two orders of magnitude higher than those for nonferroelectrics such as zinc oxide. The magnitude of the dipole moment offers the possibility of enhanced pyroelectric detection as well, although the high dielectric constant and loss tangent of the films make encapsulation of the films necessary. A significant dipole moment exists in the as-deposited and annealed film prior to any deliberate poling. Sol-gel processing of the PZT films poses a more difficult integration problem that does sputter-deposition, but the techniques remain compatible with integrated circuit processing, assuming that surface micromachining techniques are used. >