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Microfabricated ultrasonic transducers and related apparatus and methods

  • US 9,910,017 B2
  • Filed: 06/09/2016
  • Issued: 03/06/2018
  • Est. Priority Date: 07/14/2014
  • Status: Active Grant
First Claim
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1. A method of forming an ultrasound-on-a-chip device including an integrated complementary metal oxide semiconductor (CMOS) circuit, the method comprising:

  • forming a cavity in a first wafer, wherein the first wafer comprises a silicon-on-insulator (SOI) wafer;

    forming a composite substrate by fusion bonding a second wafer with the first wafer so as to seal the cavity, and annealing the composite substrate, wherein the second wafer comprises a silicon-on-insulator (SOI) wafer, and wherein forming the composite substrate comprises bonding a silicon device layer of the second wafer with an oxide layer formed on a first side of a silicon device layer of the first wafer, the cavity being formed in the oxide layer;

    forming a conductive contact on an electrode region of the composite substrate;

    removing a handle layer and a buried oxide (BOX) layer of the first wafer prior to bonding the composite substrate to a third wafer having the integrated CMOS circuit formed therein;

    bonding the composite substrate to the third wafer having the integrated CMOS circuit formed therein, using the conductive contact; and

    thinning the composite substrate to form a flexible membrane proximate the cavity.

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