Metalorganic chemical vapor deposition Pb(Zr,Ti)O-3 and selected lower electrode structures as a pathway to integrated piezoelectric microelectromechanical systems

The actuation mechanism is an important aspect of many micromachined device s. Electrostatic actuation has been the prevailing actuation method due to its relative ease in implementation using conventional silicon microfabrica tion techniques. Other mechanisms are becoming more accessible to micromach ine designs as new materials are introduced into the microfabrication proce ss. Recent progress in nonvolatile memory has led to successful incorporati on of Pb(Zr,Ti)O-3 (PZT) thin films into microelectronic devices. The prese nt work expands on this area and investigates PZT thin films and electrode/ barrier combinations for applications in micromachined devices. Incorporati on of PZT thin films into silicon micromachined devices requires electrode systems and deposition techniques that are compatible with silicon microfab rication. In this study, Ir/IrOx and Ir/(Ti,Al)N lower electrode systems we re developed to suppress diffusion of reactive species (e.g., Pb) into sili con-based microelectromechanical system devices and to enhance PZT film adh esion. Piezoelectric PZT thin films from 0.3 to 1 mum thick were prepared o n silicon wafers with these electrode structures by metalorganic chemical v apor deposition. Hysteresis loops of longitudinal piezoelectric coefficient (d(33)) were measured by dual-beam interferometry and used to characterize piezoelectric activity in these films. The effective d(33) exhibited an ap parent dependence on film thickness. d(33) values up to 70 pm/V were obtain ed for 1,um films, while thinner films exhibited lower d(33) values between 54 and 60 pm/V The dielectric loss (tan delta) was below 2% for most films irrespective of their thickness. (C) 2001 American Vacuum Society.