Sealed-cavity microstructure and microbolometer and associated fabrication methods

• US 6,252,229 B1
• Filed: 07/10/1998
• Issued: 06/26/2001
• Est. Priority Date: 07/10/1998
• Status: Expired due to Term

• Current Assignee: DRS Network & Imaging Systems, LLC (Leonardo S.p.A.)
• Original Assignee: Boeing North American Incorporated (The Boeing Co.)
• Inventors: Fitzgibbons, Eugene Timothy, Bisignano, Alan Glenn, Hays, Kenneth Maxwell
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US09/113,472
• Time in Patent Office: 1,082 Days
• Field of Search: 250/338.4
• US Class Current: 250/338.4
• 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 method for manufacturing the microstructure. Specifically, the microstructure includes first and second wafers that are positioned relative to one another so as to form a cavity between the wafers. The microstructure further includes a seal between the first and second wafers and surrounding the cavity to create a pressure seal for the cavity. This seal allows the cavity of the microstructure to be maintained at a predetermined pressure different from that of the atmosphere outside the cavity. Importantly, the microstructure further includes a structural bond between the first and second wafers that structurally integrates the first and second wafers. The structural bond renders the microstructure more rugged such that the microstructure can withstand expansion, vibrational, and shock stresses experienced by the microstructure during subsequent manufacturing and use. In one additional embodiment, the microstructure is a microbolometer that includes in addition to the seal and structural bond, a radiation detector suspended in the cavity.

Claims

1. 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, wherein said structural bond provides sufficient support to said first and second wafers such that said pressure seal is maintained intact during subsequent manufacture and use of the said microstructure.

2. The microstructure of claim 1 wherein said pressure seal comprises a deformable metal deposited on at least one of said first and second wafers.

3. The microstructure of claim 2 wherein said deformable metal comprises at least one metal selected from the group consisting of gold, tin, lead and indium.

4. The microstructure of claim 1 wherein at least one of said first and second wafers defines a seal ring extending peripherally about the cavity.

5. The microstructure of claim 4 wherein said seal ring comprises a dielectric material.

6. The microstructure of claim 1 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.

7. The microstructure of claim 1 further comprising a MEMS device disposed within the cavity defined by said first and second wafers.

8. The microstructure of claim 1 further comprising a microbolometer including an array of radiation detectors within the 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,

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.

10. 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, wherein said structural bond provides sufficient support to said first and second wafers such that said vacuum seal is maintained intact during subsequent manufacture and use of the said microbolometer.

11. The microbolometer of claim 10 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.

12. The microbolometer of claim 10 wherein at least one of said first and second wafers further comprises an antireflective coating.

13. 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, wherein said structural bond is formed outside of and peripherally about at least a portion of said pressure seal.

14. 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,

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

15. 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, wherein said structural bond is formed outside of and peripherally about at least a portion of said vacuum seal.