Method of manufacturing implantable wireless sensor for in vivo pressure measurement

• US 20060283007A1
• Filed: 08/16/2005
• Published: 12/21/2006
• Est. Priority Date: 06/21/2005
• Status: Active Grant

• Current Assignee: St. Jude Medical Luxembourg Holdings Ii S.A.R.L.
• Original Assignee: CardioMEMS Incorporated
• Inventors: Park, Jin Woo, O'Brien, David, Cros, Florent, Singh, Angad, Fonseca, Michael, Abercrombie, Matthew
• Granted Patent: US 7,621,036 B2
• Time in Patent Office: Days
• US Class Current: 29/602.100
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/076 Permanent implantations telemetry using implanted circuitry A61B5/0031; implanted stimulators for therapy A61N1/3605, A61N1/362, A61N1/372
• CPC Class Codes: A61B 5/6882 Anchoring means
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• CPC Class Codes: Y10T 29/43 Electric condenser making
• CPC Class Codes: Y10T 29/435 Solid dielectric type
• CPC Class Codes: Y10T 29/49007 Indicating transducer
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor
• CPC Class Codes: Y10T 29/49078 Laminated
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base
• CPC Class Codes: Y10T 29/49171 with encapsulating

Abstract

A method of manufacturing a sensor for in vivo applications includes the steps of providing two wafers of an electrically insulating material. A recess is formed in the first wafer, and a capacitor plate is formed in the recess of the first wafer. A second capacitor plate is formed in a corresponding region of the second wafer, and the two wafers are affixed to one another such that the first and second capacitor plates are arranged in parallel, spaced-apart relation.

Claims

1. A method of manufacturing a sensor for in vivo applications, comprising the steps of:

providing first and second wafers of an electrically insulating material;

forming a recess in said first wafer;

forming a first capacitor plate in said recess of said first wafer;

forming a second capacitor plate in a corresponding region of said second wafer;

mutually imposing said first and second wafers such that said first and second capacitor plates are arranged in parallel, spaced-apart relation; and

affixing said first and second wafers to one another in said mutually imposed position.

2. The method of claim 1, comprising the further step of:

providing an inductor coil having first and second leads;

electrically coupling said first lead of said inductor coil to said first capacitor plate; and

electrically coupling said second lead of said inductor coil to said second capacitor plate.

3. The method of claim 2, wherein said inductor coil is immobilized with respect to said capacitor plates and changes in coil configuration.

4. The method of claim 3, where the method for coil immobilization comprises using wire of sufficient strength so the coil does not shift position relative to the capacitor plates.

5. The method of claim 3, where the method for coil immobilization comprises using a coil formed on a bobbin.

6. The method of claim 5, where the bobbin is comprised of a thermoplastic material and heated to encapsulate and/or adhere to the surface of the coil receiving trench.

7. The method of claim 5, where the bobbin is press fit to at least one surface of the coil receiving trench.

8. The method of claim 3, where the method for coil immobilization comprises use of a thermosetting or thermoplastic material applied to a pre-formed coil to impart additional stability to said coil.

9. The method of claim 8, where a thermosetting polymer is applied to at least one space between the coil and the coil receiving trench in liquid form and cured.

10. The method of claim 8, where at least one thermoplastic preform is inserted and heated to fill the gap between at least one space between the coil and the coil receiving trench.

11. The method of claim 1, further comprising the step of reducing the thickness of one of said wafers underlying at least a portion of a corresponding one of said capacitor plates, whereby said reduced thickness portion is more deflectable in response to changes in ambient pressure than the unreduced thickness of said one of said wafers.

12. The method of claim 1, comprising the further step of forming a recess in said corresponding region of said second wafer, and

wherein said step of forming a second capacitor plate in a corresponding region of said second wafer comprises the step of forming a second capacitor plate in said recess of said second wafer.

13. The method of claim 1, wherein said step of providing first and second wafers of an electrically insulating material comprises the step of providing first and second wafers of a material selected from the group consisting of fused silica, quartz, Pyrex, and sintered zirconia.

14. The method of claim 1, wherein said step of affixing said first and second wafers to one another in said mutually imposed position comprises the step of laser-cutting said mutually imposed wafers to reduce the sensor to its final size and to hermetically fuse the two wafers together.

15. The method of claim 14, wherein said step of laser-cutting said mutually imposed wafers comprises the step of controlling a laser to deliver a power sufficiently large to cut and fuse the wafers together, while at the same time being sufficiently small that the internal components of the sensor are not damaged by excessive heat.

16. The method of claim 15, wherein said step of controlling said laser to deliver a power sufficiently large to cut and fuse the wafers together, while at the same time being sufficiently small that the internal components of the sensor are not damaged by excessive heat, comprises the step of controlling said laser to have a peak wavelength of approximately 10 micrometers when the wafers are comprised of fused silica.

17. The method of claim 1, wherein said step of affixing said first and second wafers to one another comprises the step of bonding said first and second wafers together using glass frit.

18. The method of claim 1, wherein said step of affixing said first and second wafers to one another comprises the step of adhering said wafers to one another.

19. The method of claim 1, wherein said step of affixing said first and second wafers to one another comprises the step of bonding said wafers together using a process selected from the group consisting of gold compression bonding, laser bonding, and anodic bonding.

20. The method of claim 1, wherein said step of forming a first capacitor plate in said recess of said first wafer comprises the step of electroplating.

21. The method of claim 20, comprising the further step, subsequent to said step of electroplating, of polishing said plate using chemical/mechanical polishing to effect at least one of planarizing and reducing the height of said plate.

22. The method of claim 20, comprising the further step, subsequent to said step of electroplating, of chemically etching said plate by a selective etchant to reduce the height of said plate.

23. The method of claim 1, wherein said step of forming a first capacitor plate in said recess of said first wafer comprises the step of using physical vapor deposition to deposit a layer of metal.

24. The method of claim 23, comprising the further steps, subsequent to said step of using physical vapor deposition, of:

applying photoresist over at least a portion of said layer of metal;

using a mask to pattern said photoresist; and

selectively etching exposed portions of said photoresist to define a desired pattern.

25. The method of claim 1, wherein said capacitor plates are spaced apart by a distance of from 0.1 to 10 micrometers.

26. The method of claim 17, wherein said capacitor plates are spaced apart by a distance of from 0.1 to 2 micrometers.

27. A method of manufacturing a sensor for in vivo applications, comprising the steps of:

providing three wafers of an electrically non-conductive material;

forming first and second capacitor plates on an upper surface of a first of said three wafers;

forming a third capacitor plate on a lower surface of a second of said three wafers;

mutually imposing said first and second wafers such that said third capacitor plate is positioned in generally parallel, spaced-apart relation from said first and second capacitor plates;

positioning an inductor coil having first and second leads on top of an upper surface of said second wafer;

electrically connecting a first one of said inductor coil leads to said first capacitor plate;

electrically connecting a second one of said inductor coil leads to said second capacitor plate;

forming a cavity in a third of said three wafers sufficient to receive said inductor coil;

positioning said third wafer on top of said second wafer with said inductor coil being received within said cavity of said third wafer; and

bonding said second wafer to said first and third wafers.

28. The method of claim 27, wherein said step of forming a cavity in said third wafer comprises the step of forming a cavity which extends all the way through said third wafer, and wherein said method further comprises the step of:

providing a fourth wafer;

positioning said fourth wafer atop said third wafer so as to close off an upper end of said cavity; and

bonding said fourth wafer to said third wafer.

29. A method of manufacturing a sensor for in vivo applications, comprising the steps of:

forming a bottom plate on a wafer of electrically insulating material;

forming a sacrificial layer over said bottom plate;

forming a top plate on top of said sacrificial layer;

removing said sacrificial layer to leave said bottom and top plates in spaced-apart relation.

30. The method of claim 29, wherein said step of forming a top plate on top of said sacrificial layer comprises the steps of:

forming a seed layer on top of said sacrificial layer; and

depositing a metal on top of said seed layer to form said top plate.

31. A method of manufacturing a sensor for in vivo applications, comprising the steps of:

providing first and second wafers;

forming a recess in said first wafer;

forming a first plate in said recess of said first wafer;

forming a coil-receiving trench in an upper surface of said second wafer;

forming second and third plates on said upper surface of said second wafer within the perimeter of said coil-receiving trench;

providing an inductor coil having first and second leads;

positioning said inductor coil within said coil-receiving trench in said upper surface of said second wafer;

electrically connecting said first and second leads of said inductor coil to said second and third plates on said upper surface of said second wafer;

mutually imposing said first and second wafers such that said first plate in said recess of said first wafer is in parallel, spaced apart relation to said second and third plates on said upper surface of said second wafer; and

affixing said first and second wafers to one another in said mutually imposed position.

32. The method of claim 31, wherein said step of affixing said first and second wafers to one another in said mutually imposed position comprises the step of cutting said first and second wafers outside said coil-receiving trench such that said wafers are both cut and fused by the heat of said laser.

33. The method of claim 32, further comprising the steps of:

prior to said step of cutting said first and second wafers, forming a dicing trench in a lower surface of said second wafer outside said coil-receiving trench; and

wherein said step of cutting said first and second wafers outside said coil-receiving trench comprises the step of cutting said mutually imposed first and second wafers with a laser at a base of said dicing trench.