Micromachined ultrasonic transducers and method of fabrication
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsButrus T. Khuri-Yakub, Yongli Huang, Arif S. Ergun
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Abstract
There is described a micromachined ultrasonic transducers (MUTS) and a method of fabrication. The membranes of the transducers are fusion bonded to cavities to form cells. The membranes are formed on a wafer of sacrificial material. This permits handling for fusions bonding. The sacrificial material is then removed to leave the membrane. Membranes of silicon, silicon nitride, etc. can be formed on the sacrificial material. Also described are cMUTs, pMUTs and mMUTs.
Claims11
The method of fabricating a microfabricated ultrasonic transducer comprising the steps of:
- selecting a silicon carrier wafer;
- selecting a silicon-on-insulator wafer having a thin silicon layer supported on an oxide layer;
- thermally oxidizing either the silicon wafer or the silicon layer of the silicon-on-insulator wafer to form a silicon oxide layer of predetermined thickness;
- applying a mask having openings of predetermined size and shape, to expose areas of the oxide layer;
- etching away the oxide at the exposed openings to define oxide walls;
- bonding the two wafers with the thin silicon layer facing the silicon carrier wafer and spaced therefrom by the oxide layer whereby cells are formed;
- and
- removing the wafer and oxide layer of the silicon-on-oxide-on insulator wafer leaving the thin silicon membrane supported spaced from the silicon carrier wafer by the silicon oxide.
The method of forming an ultrasonic transducer the type comprising a membrane supported on a carrier wafer by patterned oxide supports of predetermined size and shape;
- selecting a carrier wafer;
- selecting a silicon-on-insulator wafer having a thin silicon layer supported by an oxide;
- forming an oxide layer of predetermined thickness and by masking and etching removing the oxide layer from selected regions to provide wells having walls of predetermined size and shape;
- bonding the carrier and silicon of the silicon-on-insulator wafer and the oxide walls;
- and
- removing the support oxide and wafer leaving the silicon layer to form membranes which defines cavities of predetermined size and shape.
The method of fabricating ultrasonic transducer cells which comprises the steps of:
- selecting a substrate;
- selecting a wafer including a thin membrane supported by a sacrificial material;
- forming an oxide layer having windows on the thin membrane or on the substrate;
- bonding the thin membrane, oxide layer and substrate to form cells at said windows;
- and
- removing the sacrificial material to leave the membrane supported spaced from the substrate.
The method of fabricating ultrasonic transducer cells which comprises the steps of:
- selecting a substrate;
- selecting a water including a thin membrane supported by a sacrificial material;
- forming an oxide layer on the thin membrane or on the substrate;
- removing by masking and etching selected portions of said oxide layer to form wells;
- bonding the thin membrane, oxide layer and substrate to form cells;
- and
- removing the sacrificial material to leave the membrane supported spaced from the substrate.
Dependencies are inferred from the claim text.