Ultrasonic Transducer Electrode Assembly

Abstract

The present disclosure provides a method of fabricating an ultrasound transducer. A substrate having a first side and a second side opposite the first side is provided. A bottom electrode is formed over the first side of the substrate. A piezoelectric element is formed over the bottom electrode. The piezoelectric element has a chamfered sidewall. A top electrode is formed over the piezoelectric element. A step metal element is formed over a portion of the top electrode proximate to the chamfered sidewall of the piezoelectric element.

What is claimed is: 
     
         1 . A micromachined ultrasound transducer, comprising:
 a substrate;   a bottom electrode disposed over the substrate;   a piezoelectric element disposed over the bottom electrode;   a top electrode disposed over at least a top surface and a sidewall of the piezoelectric element; and   a step metal element disposed over a sidewall of the top electrode.   
     
     
         2 . The micromachined ultrasound transducer of  claim 1 , wherein the step metal element and the top electrode have substantially similar material compositions. 
     
     
         3 . The micromachined ultrasound transducer of  claim 1 , wherein the piezoelectric element has a chamfer. 
     
     
         4 . The micromachined ultrasound transducer of  claim 1 , further comprising: a well disposed in the substrate. 
     
     
         5 . The micromachined ultrasound transducer of  claim 4 , wherein the well is at least partially filled with a backing material. 
     
     
         6 . The micromachined ultrasound transducer of  claim 4 , wherein portions of the top electrode, the bottom electrode, and the piezoelectric element disposed over the well each have an arcuate shape. 
     
     
         7 . The micromachined ultrasound transducer of  claim 1 , further comprising a dielectric layer disposed between the substrate and at least the bottom electrode. 
     
     
         8 . The micromachined ultrasound transducer of  claim 1 , wherein the piezoelectric element contains polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), or polyvinylidene fluoride-tetrafluoroethlene (PVDF-TFE). 
     
     
         9 . The micromachined ultrasound transducer of  claim 1 , wherein the top electrode includes:
 a top segment disposed over the top surface of the piezoelectric element;   a bottom segment disposed over the substrate, the bottom segment being non-planar with the top segment; and   a via coupling the top segment to the bottom segment.   
     
     
         10 . The micromachined ultrasound transducer of  claim 9 , wherein the via is disposed directly on the bottom segment. 
     
     
         11 . The micromachined ultrasound transducer of  claim 9 , wherein the via includes a recessed portion of the top electrode. 
     
     
         12 . An ultrasound system, comprising:
 an imaging component that includes a flexible elongate member and a piezoelectric micromachined ultrasound transducer (PMUT) coupled to a distal end of the elongate member, wherein the PMUT includes:
 a substrate having a front surface and a back surface opposite the first surface; 
 a well located in the substrate, the well extending from the back surface of the substrate to, but not beyond, the front surface of the substrate, wherein the well is at least partially filled with a backing material; 
 a transducer membrane disposed over the well, wherein the transducer member includes a piezoelectric element disposed between a top electrode and a bottom electrode; and 
 a step metal element disposed over a sidewall of the piezoelectric element; 
   an interface module configured to engage with a proximal end of the elongate member; and   an ultrasound processing component in communication with the interface module.   
     
     
         13 . The ultrasound system of  claim 12 , wherein the step metal element and the top electrode have substantially similar material compositions. 
     
     
         14 . The ultrasound system of  claim 12 , wherein the piezoelectric element has a chamfer. 
     
     
         15 . The ultrasound system of  claim 12 , wherein portions of the transducer membrane disposed over the well has an arcuate profile. 
     
     
         16 . The ultrasound system of  claim 12 , further comprising a dielectric layer disposed between the substrate and the bottom electrode. 
     
     
         17 . The ultrasound system of  claim 12 , wherein the piezoelectric element contains polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), or polyvinylidene fluoride-tetrafluoroethlene (PVDF-TFE). 
     
     
         18 . The ultrasound system of  claim 12 , wherein the top electrode includes:
 a top segment disposed over a top surface of the piezoelectric element;   a bottom segment disposed over the substrate, the bottom segment being non-planar with the top segment; and   a via coupling the top segment to the bottom segment.   
     
     
         19 . The ultrasound system of  claim 18 , wherein the via is disposed directly on the bottom segment. 
     
     
         20 . The ultrasound system of  claim 18 , wherein the via includes a recessed portion of the top electrode. 
     
     
         21 . A method of fabricating an ultrasound transducer, the method comprising:
 providing a substrate having a first side and a second side opposite the first side;   forming a bottom electrode over the first side of the substrate;   forming a piezoelectric element over the bottom electrode, the piezoelectric element having a chamfered sidewall;   forming a top electrode over the piezoelectric element; and   forming a step metal element over a portion of the top electrode proximate to the chamfered sidewall of the piezoelectric element.   
     
     
         22 . The method of  claim 21 , wherein the top electrode, the piezoelectric element, and the bottom electrode collectively form a transducer membrane, and further comprising:
 forming a well in the substrate from the second side; and   deflecting a portion of the transducer membrane disposed over the well into an arcuate shape.   
     
     
         23 . The method of  claim 22 , further comprising: filling the well with a backing material. 
     
     
         24 . The method of  claim 21 , further comprising: forming, before the forming of the bottom electrode, a dielectric layer over the first side of the substrate. 
     
     
         25 . The method of  claim 21 , wherein the step metal element and the top electrode have substantially similar material compositions. 
     
     
         26 . The method of  claim 21 , wherein the piezoelectric element contains polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), or polyvinylidene fluoride-tetrafluoroethlene (PVDF-TFE). 
     
     
         27 . The method of  claim 21 , wherein the forming of the top electrode is performed so that the top electrode includes:
 a top segment disposed over a top surface of the piezoelectric element;   a bottom segment disposed over the substrate, the bottom segment being non-planar with the top segment; and   a via coupling the top segment to the bottom segment.   
     
     
         28 . The method of  claim 27 , wherein the via is disposed directly on the bottom segment. 
     
     
         29 . The method of  claim 27 , wherein the via includes a recessed portion of the top electrode.