Method of fabricating a polymer-based capacitive ultrasonic transducer

Abstract

A method of fabricating a polymer-based capacitive ultrasonic transducer, which comprises the steps of: (a) providing a substrate; (b) forming a first conductor on the substrate; (c) coating a sacrificial layer on the substrate while covering the first conductor by the same; (d) etching the sacrificial layer for forming an island while maintaining the island to contact with the first conductor; (e) coating a first polymer-based material on the substrate while covering the island by the same; (f) forming a second conductor on the first polymer-based material; (g) forming a via hole on the first polymer-based material while enabling the via hole to be channeled to the island; and (h) utilizing the via hole to etch and remove the island for forming a cavity.

1 . A method of fabricating a polymer-based capacitive ultrasonic transducer, comprising steps of:
 (a) providing a substrate;   (b) forming a first conductor on the substrate;   (c) coating a sacrificial layer on the substrate while covering the first conductor by the same;   (d) etching the sacrificial layer for forming an island while maintaining the island to contact with the first conductor;   (e) coating a first polymer-based material on the substrate while covering the island completely by the same;   (f) forming a second conductor on the first polymer-based material;   (g) forming a via hole on the first polymer-based material while enabling the via hole to be channeled to the island; and   (h) utilizing the via hole to etch and remove the island for forming a cavity.   
   
   
       2 . The method of  claim 1 , wherein the step (b) further comprises a step of:
 (b1) coating the first conductor on the substrate while enabling the substrate to be covered completely by the first conductor.   
   
   
       3 . The method of  claim 2 , wherein the step (b1) further comprises a step of:
 (b2) etching the first conductor while patterning the same, the step (b1) being performed after the step (b1).   
   
   
       4 . The method of  claim 1 , further comprising steps of:
 (i) covering the second conductor completely by a second polymer-based material.   
   
   
       5 . The method of  claim 1 , further comprising steps of:
 (i′) covering the second conductor completely by a second polymer-based material wile sealing the via hole by the same.   
   
   
       6 . The method of  claim 1 , wherein the substrate is made of silicon. 
   
   
       7 . The method of  claim 1 , wherein the first conductor is made of a metal. 
   
   
       8 . The method of  claim 7 , wherein the first conductor of step (b) is formed on the substrate by means of sputtering. 
   
   
       9 . The method of  claim 1 , wherein the second conductor is made of a metal. 
   
   
       10 . The method of  claim 9 , wherein the second conductor of step (f) is formed on the first polymer-based material by means of sputtering. 
   
   
       11 . The method of  claim 1 , wherein the sacrificial layer is made of a metal. 
   
   
       12 . The method of  claim 11 , wherein the metal is copper. 
   
   
       13 . The method of  claim 1 , wherein the etching performed in the step (h) is wet etching. 
   
   
       14 . The method of  claim 1 , wherein the first polymer-based material is the SU-8 photo-resist produced by International Business Machines Corp (IBM).