Linear displacement microactuators utilizing piezoelectric thin films

• Main Author: Glumac, Daniel E
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1995
• Subjects: Electrical engineering; Materials science
• ISBN: 9798209120476

Two novel types of compact linear motion microactuators which utilize the piezoelectric PZT (lead zirconate titanite) have been fabricated. The meander line actuator is made up of several piezoelectric bars configured in a serpentine geometry. The alternating expansions and contractions of adjacent bars generate a net horizontal displacement. The unimorph (vertical) actuator consists of several serially arranged composite bars of PZT and a rigid material in a tethered geometry configuration. Bending moments generated by the unimorph construction cause the bars to bend, and a net displacement perpendicular to the longitudinal axis of the bar is produced. Macroscale versions of these actuators have been constructed with bulk PZT bars for the purposes of modeling and characterization, and bead-blasted bulk devices and microscale silicon micromachined versions have been fabricated. The on-chip structures consist of an LPVCD silicon nitride/polysilicon core, a thin film of PZT, and top and bottom electrodes (Pt/Ti). The thin film PZT is deposited with a sol-gel spincoating technique. Beneath the structure are two layers of spacer oxide that are delineated to free the devices. The surface sacrificial layer is LPCVD phosphosilicate glass. The lower layer is made up of several recessed oxide wells that are each separated by five microns. These silicon substrate separation widths act as rails to help prevent device stiction during the final drying. Prior to the structure material patterning, an encapsulant is used to protect the piezoelectric material during the sacrificial etch. Some simple cantilever beam structures are also included on the chip.