MEMS Device with Outgassing Shield

• US 20150115376A1
• Filed: 10/24/2013
• Published: 04/30/2015
• Est. Priority Date: 10/24/2013
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Chen, Li, Nunan, Thomas Kieran, Yang, Kuang L.
• Granted Patent: US 9,764,946 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2207/012 the micromechanical device and the control or processing electronics being separate parts in the same package
• CPC Class Codes: B81B 2207/095 through the lid
• CPC Class Codes: B81B 3/0094 Constitution or structural means for improving or controlling physical properties not provided for in B81B3/0067 - B81B3/0091
• CPC Class Codes: B81B 7/0035 for maintaining a controlled atmosphere inside of the chamber containing the MEMS
• CPC Class Codes: B81B 7/0041 maintaining a controlled atmosphere with techniques not provided for in B81B7/0038
• CPC Class Codes: B81C 1/00293 maintaining a controlled atmosphere with processes not provided for in B81C1/00285
• CPC Class Codes: B81C 2203/019 characterised by the material or arrangement of seals between parts
• CPC Class Codes: B81C 3/001 Bonding of two components

Abstract

A capped micromachined device has a movable micromachined structure in a first hermetic chamber and one or more interconnections in a second hermetic chamber that is hermetically isolated from the first hermetic chamber, and a barrier layer on its cap where the cap faces the first hermetic chamber, such that the first hermetic chamber is isolated from outgassing from the cap.

Claims

1. A capped micromachined device comprising:

a substrate comprising a MEMS structure suspended from the substrate, and at least a first electrical conductor coupled to the MEMS structure;

a semiconductor cap suspended parallel to the substrate and separated from the substrate by a capping gap, the cap comprising at least a second electrical conductor;

a first isolation wall disposed between the substrate and the cap and spanning the capping gap, the first isolation wall and the substrate defining a MEMS chamber enclosing the MEMS structure such that the MEMS structure is movable within the MEMS chamber;

a shield layer disposed between a region of a face of the cap and the MEMS chamber, the region of the face of the cap being a portion of the face of the cap that is directly opposite the MEMS chamber, and configured to provide a complete outgas barrier between the region of the face of the cap and the MEMS chamber;

a second isolation wall disposed between the substrate and the cap and spanning the capping gap, the second isolation wall, the substrate and the cap defining an interconnection chamber, the interconnection chamber hermetically sealed and hermetically isolated from the MEMS chamber; and

an interconnection structure disposed within the interconnection chamber and spanning the capping gap, the interconnection structure electrically coupling the first electrical conductor to the second electrical conductor,

so that the MEMS chamber is hermetically isolated from the interconnection chamber, and the MEMS structure is electrically coupled to the second electrical conductor.

2. The capped micromachined device of claim 1, wherein the cap comprises an integrated circuit including a plurality of active semiconductor devices.

3. The capped micromachined device of claim 1, wherein the MEMS structure comprises one of an accelerometer beam, a gyroscope structure, and a switch arm.

4. The capped micromachined device of claim 1, wherein the second isolation wall comprises one of a solder ring or a glass frit.

5. The capped micromachined device of claim 1, wherein each of the first isolation wall and the second isolation wall comprises a metal seal ring.

6. The capped micromachined device of claim 1, wherein the MEMS chamber is adjacent to the interconnect chamber.

7. The capped micromachined device of claim 1, wherein the MEMS chamber is surrounded by the interconnect chamber.

8. The capped micromachined device of claim 1, wherein the MEMS chamber and the interconnect chamber both enclose an identical initial internal environment.

9. The capped micromachined device of claim 1, wherein the cap is an integrated circuit configured to process output signals from the MEMS structure.

10. The capped micromachined device of claim 1, wherein the shield layer comprises one of titanium nitride and a titanium and titanium nitride combo layer stack and is integrally coupled to the first isolation wall, and is biased to a fixed electrical potential.

11. A method of fabricating a capped micromachined device comprising:

providing a substrate comprising a MEMS structure suspended from the substrate, and at least a first electrical conductor coupled to the MEMS structure;

providing a semiconductor cap, the cap comprising at least a second electrical conductor, and a shield layer on a face of the cap;

providing a first isolation wall configured to extend between the substrate and the cap;

providing a second isolation wall configured to extend between the substrate and the cap;

providing an interconnection structure configured to extend between the substrate and the cap;

coupling the cap to the substrate such that the first isolation wall, the second isolation wall, and the interconnection structure span a capping gap between the cap and the substrate, and such that;

the cap and the first isolation wall define a MEMS chamber enclosing the MEMS structure such that the MEMS structure is movable within the MEMS chamber, with the shield layer disposed so as to provide a complete barrier between the face of the cap and the MEMS chamber, and

the cap and the second isolation wall define an interconnection chamber, the interconnection chamber hermetically sealed and hermetically isolated from the MEMS chamber, the interconnection structure disposed within the interconnection chamber and electrically coupling the first electrical conductor to the second electrical conductor,

so that the MEMS chamber is hermetically isolated from the interconnection chamber, and the MEMS structure is electrically coupled to the second electrical conductor.

12. The capped micromachined device of claim 11, wherein the cap comprises an integrated circuit including a plurality of active semiconductor devices.

13. The capped micromachined device of claim 11, wherein the second isolation wall comprises one of a solder ring or a glass frit.

14. The capped micromachined device of claim 11, wherein each of the first isolation wall and the second isolation wall comprises a metal seal ring.

15. The capped micromachined device of claim 11, wherein the cap is an integrated circuit configured to process output signals from the MEMS structure.

16. The capped micromachined device of claim 11, wherein the shield layer comprises one of titanium nitride and a titanium and titanium nitride combo layer stack.

17. A capped micromachined device comprising:

a substrate comprising a MEMS structure suspended from the substrate, and at least a first electrical conductor coupled to the MEMS structure;

a semiconductor cap suspended parallel to the substrate and separated from the substrate by a capping gap, the cap comprising at least a second electrical conductor;

a first isolation wall disposed between the substrate and the cap and spanning the capping gap, the first isolation wall and the substrate defining a MEMS chamber enclosing the MEMS structure such that the MEMS structure is movable within the MEMS chamber; and

a shield layer disposed between a region of a face of the cap and the MEMS chamber, the region of the face of the cap being a portion of the face of the cap that is directly opposite the MEMS chamber, and configured to provide a complete outgas barrier between the region of the face of the cap and the MEMS chamber;

so that the MEMS chamber is hermetically isolated from the semiconductor cap.

18. The capped micromachined device of claim 17, wherein the shield layer comprises one of titanium nitride, a titanium and titanium nitride combo layer stack, Tungsten, Titanium Tungsten, and a metal silicide.

19. The capped micromachined device of claim 17, wherein the cap comprises an integrated circuit including a plurality of active semiconductor devices.

20. The capped micromachined device of claim 19, wherein the cap comprises an integrated circuit configured to process output signals from the MEMS structure.