Asymetric membrane cMUT devices and fabrication methods

• US 20050203397A1
• Filed: 03/11/2005
• Published: 09/15/2005
• Est. Priority Date: 02/27/2004
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Degertekin, F. Levent
• Granted Patent: US 7,646,133 B2
• Time in Patent Office: Days
• US Class Current: 600/437
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type

Abstract

Asymmetric membrane capacitive micromachined ultrasonic transducer (“cMUT”) devices and fabrication methods are provided. In a preferred embodiment, a cMUT device according to the present invention generally comprises a membrane having asymmetric properties. The membrane can have a varied width across its length so that its ends have different widths. The asymmetric membrane can have varied flex characteristics due to its varied width dimensions. In another preferred embodiment, a cMUT device according to the present invention generally comprises an electrode element having asymmetric properties. The electrode element can have a varied width across its length so that its ends have different widths. The asymmetric electrode element can have different reception and transmission characteristics due to its varied width dimensions. In another preferred embodiment, a mass load positioned along the membrane can alter the mass distribution of the membrane. Other embodiments are also claimed and described.

Claims

1. A cMUT comprising:

a membrane having a length and a width;

wherein the membrane is asymmetric about a line of bisection across the length of the membrane.

2. The cMUT of claim 1, the membrane further having a first end and a second end, wherein the width of the membrane at the first end is greater than the width of the membrane at the second end, and wherein the distance from the first end to the second end defines the length of the membrane.

3. The cMUT of claim 1, wherein the membrane requires a first collapse force to drive the membrane to a collapse state at a first point proximate the first end and a second collapse force to drive the membrane to a collapse state at a second point proximate the second end, and wherein the first collapse force is lower than the second collapse force.

4. The cMUT of claim 1, further comprising:

an electrode element having a length defined as the distance between a first end and a second end;

wherein the electrode element is asymmetric about a line of bisection across the length of the electrode element.

5. The cMUT of claim 3, further comprising:

an electrode element having a length and a width, the length defined as the distance between a first end and a second end;

wherein the width of the electrode element at the first end is less than the width of the electrode element at the second end.

6. The cMUT of claim 5, wherein the electrode element is adapted to provide the first collapse force and the second collapse force, flexing the membrane at the first point and the second point a substantially equal amount.

7. The cMUT of claim 1, wherein the membrane width varies across the length of the membrane such that the membrane has a plurality of cross sections, wherein each cross section of the plurality of cross sections has a different width, and wherein each cross section of the plurality of cross sections has a different fundamental frequency.

8. The cMUT of claim 2, wherein the length of the membrane is greater than two times the width of the membrane at the first end.

9. The cMUT of claim 1, further comprising

an electrode element having a length and a width, the length defined as the distance between a first end and a second end, wherein the width of the electrode element at the first end is less than the width of the electrode element at the second end, and wherein the electrode element is adapted to provide a first collapse force and a second collapse force, flexing the membrane at the first point and the second point a substantially equal amount;

and

wherein the membrane has a vibration mode and wherein the width of the membrane is adapted to alter the vibration mode of the membrane and the flexing characteristics of the membrane.

10. The cMUT of claim 1, wherein the membrane is adapted to transmit and receive ultra-wideband signals.

11. The cMUT of claim 1, wherein the membrane is substantially trapezoidal.

12. A method of fabricating a cMUT comprising the steps of:

providing a membrane having a length and a width; and

configuring the membrane to be asymmetric about a line of bisection across the length of the membrane.

13. The method of claim 12, wherein the step of configuring the membrane to be substantially asymmetric about a lateral line of bisection across the length of the membrane comprises the step of:

configuring the membrane to have a first width at a first end of the membrane and a second width at the second end of the membrane;

wherein the first width is greater than the second width, and wherein the distance from the first end to the second end defines the length of the membrane.

14. The method of claim 12, further comprising the step of:

providing an electrode element having a length defined as the distance between a first end and a second end; and

wherein the electrode element is asymmetric about a line of bisection across the length of the electrode element.

15. The method of claim 12, further comprising the steps of:

providing an electrode element having a length defined as the distance between a first end and a second end; and

configuring the electrode element to have a first width at the first end of the electrode element and a second width at the second end of the electrode element;

wherein the first width is less than the second width.

16. The method of claim 12, further comprising the step of:

configuring the membrane to have a first collapse force to drive the membrane to a collapse state at a first point proximate a first end and a second collapse force to drive the membrane to a collapse state at a second point proximate a second end, and wherein the first collapse force is lower than the second collapse force.

17. The method of claim 16, further comprising the steps of:

providing an electrode element; and

configuring the electrode element to provide the first collapse force and the second collapse force, flexing the membrane at the first point and the second point a substantially equal amount.

18. The method of claim 12, further comprising the step of:

configuring the membrane such that the length of the membrane is greater than two times the width of the membrane measured at one of the first end and the second end.

19. The method of claim 12, further comprising the step of:

configuring the membrane to transmit and receive ultra-wideband signals.

20. The method of claim 12, wherein the step of configuring the membrane to be substantially asymmetric about a lateral line of bisection across the length of the membrane comprises the step of:

configuring the membrane into a substantially trapezoidal shape.