Three-Dimensional, Ultrasonic Transducer Arrays, Methods of Making Ultrasonic Transducer Arrays, and Devices Including Ultrasonic Transducer Arrays

• US 20070264732A1
• Filed: 03/12/2007
• Published: 11/15/2007
• Est. Priority Date: 03/10/2006
• Status: Active Grant

• Current Assignee: UNM Rainforest Innovations (f/k/a STC.UNM) (The University of New Mexico)
• Original Assignee: UNM Rainforest Innovations (f/k/a STC.UNM) (The University of New Mexico)
• Inventors: CHEN, Jingkuang
• Granted Patent: US 8,372,680 B2
• Time in Patent Office: Days
• US Class Current: 438/22
• CPC Class Codes: A61B 1/041 Capsule endoscopes for imaging
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: A61B 8/4472 Wireless probes
• CPC Class Codes: A61B 8/4488 the transducer being a phased array
• CPC Class Codes: A61B 8/4494 characterised by the arrangement of the transducer elements devices for short-range imaging using particular transducer elements arrangements under G01S15/8909; arrangements of transducers in generation of mechanical vibrations of infrasonic, sonic or ultrasonic frequency B06B1/0607
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: B06B 1/06 operating with piezoelectric effect or with electrostriction piezoelectric or electrostrictive devices per se H10N30/00
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: B81C 1/00095 Interconnects
• CPC Class Codes: B81C 3/008 Aspects related to assembling from individually processed components, not covered by groups B81C3/001 - B81C3/002
• CPC Class Codes: G01S 15/8929 using a three-dimensional transducer configuration
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

Medical imaging devices may comprise an array of ultrasonic transducer elements. Each transducer element may comprise a substrate having a doped surface creating a highly conducting surface layer, a layer of thermal oxide on the substrate, a layer of silicon nitride on the layer of thermal oxide, a layer of silicon dioxide on the layer of silicon nitride, and a layer of conducting thin film on the layer of silicon dioxide. The layers of silicon dioxide and thermal oxide may sandwich the layer of silicon nitride, and the layer of conducting thin film may be separated from the layer of silicon nitride by the layer of silicon dioxide.

Claims

1. A medical imaging device comprising:

an array of ultrasonic transducer elements, each transducer element comprising

a substrate having a doped surface creating a highly conducting surface layer,

a layer of thermal oxide on the substrate,

a layer of silicon nitride on the layer of thermal oxide,

a layer of silicon dioxide on the layer of silicon nitride, said layers of silicon dioxide and thermal oxide sandwiching said layer of silicon nitride, and

a layer of conducting thin film on the layer of silicon dioxide, said layer of conducting thin film being separated from said layer of silicon nitride by said layer of silicon dioxide.

2. The device of claim 1, wherein said conducting thin film is not in direct contact with said silicon dioxide.

3. The device of claim 1, wherein said layer of thermal oxide comprises a layer of silicon dioxide.

4. The device of claim 1, wherein said layer of conducting thin film comprises a layer of polysilicon.

5. The device of claim 4, wherein said polysilicon comprises a counter electrode of said transducer element.

6. The device of claim 1, wherein at least two of said elements of the array are connected to one another by a metal interconnect.

7. The device of claim 6, wherein a portion of the silicon nitride layer is removed such that the metal interconnect is not in direct contact with the silicon nitride.

8. A method of fabricating an array of ultrasonic transducers for a medical imaging device, comprising:

doping a surface of a substrate to create a highly conducting surface layer;

growing a layer of thermal oxide on the highly conducting surface layer of the substrate;

depositing a layer of silicon nitride on the layer of thermal oxide;

depositing a layer of silicon dioxide on the layer of silicon nitride, said layers of silicon dioxide and thermal oxide sandwiching said layer of silicon nitride; and

depositing a layer of conducting thin film on the layer of silicon dioxide, said layer of conducting thin film being separated from said layer of silicon nitride by said layer of silicon dioxide.

9. The method of claim 8, wherein said conducting thin film is not in direct contact with said silicon dioxide.

10. The method of claim 8, wherein said layer of thermal oxide comprises a layer of silicon dioxide.

11. The method of claim 8, wherein said layer of conducting thin film comprises a layer of polysilicon.

12. The method of claim 11, further comprising doping said polysilicon layer.

13. The method of claim 8, further comprising creating patterns in the conducting thin film associated with at least two transducer elements of said array.

14. The method of claim 13, further comprising electrically connecting said two elements of the array.

15. The method of claim 14, said connecting comprising connecting the two elements to one another by a metal interconnect.

16. The method of claim 15, further comprising removing a portion of the silicon nitride layer such that the metal interconnect is not in direct contact with the silicon nitride.

17. A medical imaging device comprising:

an array of ultrasonic transducer elements, each transducer element comprising

a substrate having a doped surface creating a highly conducting surface layer,

a plurality of sandwiched dielectric layers,

a first layer of conducting thin film on the dielectric layers, said first layer of conducting thin film and said substrate sandwiching said dielectric layers,

a second layer of conducting thin film having a portion in contact with the first layer of conducting thin film and a portion separated from said first layer of conducting thin film, said second layer having at least one hole therethrough,

a vacuum cavity between said first and second layers of conducting thin film, and

a silicon nitride film on said second layer of conducting thin film, said silicon nitride film extending through said hole in the second layer and into said vacuum cavity so as to prevent portions of the second layer from collapsing the vacuum cavity and contacting said first layer.

18. The device of claim 17, further comprising an oxide layer sandwiched between said silicon nitride film and said second layer.

19. The device of claim 18, wherein said oxide layer substantially limits contact between said silicon nitride film and said second layer to sidewalls of said at least one hole.

20. The device of claim 17, wherein the medical device comprises a wireless capsule endoscope.