Method for fabricating a sealed-cavity microstructure

• US 20010022207A1
• Filed: 04/17/2001
• Published: 09/20/2001
• Est. Priority Date: 07/10/1998
• Status: Active Grant

• Current Assignee: DRS Network & Imaging Systems, LLC (Leonardo S.p.A.)
• Original Assignee: DRS Sensors & Targeting Systems, Inc. (Leonardo S.p.A.)
• Inventors: Fitzgibbons, Eugene Timothy, Bisignano, Alan Glenn, Hays, Kenneth Maxwell
• Granted Patent: US 6,596,117 B2
• Time in Patent Office: Days
• US Class Current: 148/518
• CPC Class Codes: B81C 1/00269 Bonding of solid lids or wafers to the substrate
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/045 Sealings; Vacuum enclosures; Encapsulated packages; Wafer bonding structures; Getter arrangements getter arrangements per se H01L23/26 and H01L21/3221
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: Y10T 156/1054 and simultaneously bonding [e.g., cut-seaming]

Abstract

A sealed cavity microstructure and an associated fabrication method are provided that incorporate both a tight pressure seal and a rugged structural bond. A rugged microstructure device incorporating a pressure-maintained cavity may thereby be fabricated. A vacuum cavity microbolometer is also provided that is fabricated using the associated method. The sealed cavity microstructure and the vacuum cavity microbolometer are thereby adapted to low-cost wafer-scale batch processing.

Claims

1. A method of fabricating a microstructure with at least one pressure-maintained cavity, the method comprising steps of:

providing first and second wafers, wherein at least one wafer defines a recessed portion;

joining said first and second wafers such that the recessed portion of at least one of the wafers forms a cavity therebetween;

forming a pressure seal between said first and second wafers to maintain a pre-determined pressure within said cavity; and

forming a structural bond between said first and second wafers to structurally integrate at least a portion of said first and second wafers.

2. The method of

claim 1

wherein said pressure seal forming step comprises depositing a deformable metal peripherally about the cavity on at least one of said first and second wafers.

3. The method of

claim 2

wherein said depositing step comprises depositing at least one deformable metal selected from the group consisting of gold, tin, lead and indium.

4. The method of

claim 2

wherein said depositing step comprises sputtering at least one deformable metal peripherally about the cavity.

5. The method of

claim 1

further comprising the step of forming a seal ring on at least one of said first and second wafers so as to surround the cavity, wherein said step of forming a pressure seal comprises forming a seal on said seal ring.

6. The method of

claim 1

wherein said structural bond forming step is selected from the group consisting of anodic bonding the first and second wafers, direct bonding the first and second wafers, micro-velcro bonding the first and second wafers, and soldering the first and second wafers.

7. The method of

claim 1

wherein a plurality of cavities are defined by the first and second wafers, and wherein the method further comprises the step of dividing the first and second wafers into a plurality of microstructures that each have at least one cavity.

8. The method of

claim 1

wherein a plurality of cavities are defined by the first and second wafers, wherein the method further comprises the step of forming seal rings on at least one of said first and second wafers so as to surround respective ones of the cavities, wherein said pressure seal forming step comprises depositing a deformable metal on each seal ring, wherein said structural bond forming step comprises forming a structural bond outside of and peripherally about at least a portion of each seal ring, and wherein the method further comprises the step of dividing the first and second wafers into a plurality of microstructures that each have at least one cavity.

9. A microstructure with at least one pressure-maintained cavity, said microstructure comprising:

first and second wafers defining a cavity therebetween;

a pressure seal between said first and second wafers that extends peripherally about the cavity to maintain a pre-determined pressure within said cavity; and

a structural bond between said first and second wafers to structurally integrate at least a portion of said first and second wafers.

10. The microstructure of

claim 9

wherein said pressure seal comprises a deformable metal deposited on at least one of said first and second wafers.

11. The microstructure of

claim 10

wherein said deformable metal comprises at least one metal selected from the group consisting of gold, tin, lead and indium.

12. The microstructure of

claim 9

wherein at least one of said first and second wafers defines a seal ring extending peripherally about the cavity.

13. The microstructure of

claim 12

wherein said seal ring comprises a dielectric material.

14. The microstructure of

claim 9

wherein said structural bond is selected from the group consisting of an anodic bond, a direct bond, a micro-velcro bond, and a soldered bond.

15. The microstructure of

claim 9

further comprising a MEMS device disposed within the cavity defined by said first and second wafers.

16. The microstructure of

claim 9

further comprising a microbolometer including an array of radiation detectors within the cavity.

17. The microstructure of

claim 9

wherein at least one of said first and second wafers defines a seal ring that extends peripherally about the cavity, wherein the pressure seal comprises a deformable metal deposited on the seal ring, and wherein the structural bond comprises a structural bond formed outside of and peripherally about at least a portion of the seal ring.

18. A microbolometer comprising:

first and second wafers defining a cavity therebetween;

at least one radiation detector suspended within the cavity;

a vacuum seal between said first and second wafers that extends peripherally about the cavity to maintain a vacuum within said cavity; and

a structural bond between said first and second wafers to structurally integrate at least a portion of said first and second wafers.

19. The microbolometer of

claim 18

wherein at least one of said first and second wafers further comprises an electrical circuit adapted to sense the temperature of said at least one radiation detector.

20. The microbolometer of

claim 18

wherein at least one of said first and second wafers further comprises an antireflective coating.