Piezoelectric micromachined ultrasonic transducer and its fabrication method

Abstract

Piezoelectric micromachined ultrasonic transducer and its fabrication method are disclosed. A first etch stop layer (104) and a sacrificial layer (106) are deposited (700, 702) to form a structure. A trench (108) extends (704) to the first etch stop layer (104) defining a boundary to a cavity area (110). A refill is deposited (706), forming a barrier being resistive to an etching process of sacrificial material. A second etch stop layer (112) is deposited (708). An opening (114) is etched (710) above the cavity area. A layer of sacrificial layer material (116) is deposited (712) as a horizontal line covering the opening and the other end of the horizontal line not being above the cavity area (110). A third etch stop layer (118) is deposited (714) and a hole (120) formed (716) to horizontal sacrificial layer material line (118) not being above the cavity area (110). Sacrificial material is removed (718) from the cavity area (106) through the hole (120) for forming at least one cavity (122) within the layered structure. First and second metal electrodes (722, 728) and piezo layer (724) are deposited.