Discrete stress isolator

• US 20070170525A1
• Filed: 01/06/2006
• Published: 07/26/2007
• Est. Priority Date: 01/06/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Eskridge, Mark
• Granted Patent: US 8,129,801 B2
• Time in Patent Office: Days
• US Class Current: 257/404
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81B 7/0048 between the MEMS die and the substrate
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/73257 Bump and wire connectors
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

A discrete stress isolation apparatus for a Micro Electro-Mechanical System (MEMS) inertial sensor device having a mechanism die and a package. A capacitive device mechanism is formed in a substrate layer positioned between the mechanism die and package substrate. A discrete stress isolation structure is formed in the same substrate layer with but physically separated from the capacitive device mechanism. The discrete stress isolation structure is interposed between the mechanism die and the package substrate and provides the mechanical and electrical attachment therebetween.

Claims

1. A Micro Electro-Mechanical System (MEMS) sensor device, comprising:

a package substrate;

a mechanism die) spaced away from the package substrate;

a mechanism device depending from the mechanism die between the mechanism die and the package substrate; and

one or more discrete isolation structures interposed between the mechanism die and the package substrate, the one or more discrete isolation structures attaching the mechanism die to the package substrate.

2. The device of claim 1 wherein the isolation structures are formed in a single substrate layer with the mechanism device.

3. The device of claim 1 wherein the isolation structures are connected to the mechanism die through one or more anchors.

4. The device of claim 1, further comprising stud bumps formed between one or more electrical interface pads formed on the isolation structures and one or more electrical interface pads formed on the package substrate.

5. The device of claim 1 wherein the isolation structures further comprise mutually isolated first and second portions linked by one or more flexures.

6. The device of claim 1, further comprising a cover plate attached to the mechanism device opposite from the mechanism die;

and

wherein the package substrate is further structured to accommodate the cover plate.

7. The device of claim 1 wherein the mechanism device further comprises a device structured for measuring differential capacitance between different capacitors.

8. A Micro Electro-Mechanical System (MEMS) sensor device, comprising:

a package substrate having a plurality of electrical interface pads on a surface thereof;

a base wafer having a relatively thicker handle layer and a relatively thinner active layer;

a mechanism die formed in the handle layer of the base wafer;

a mechanism device formed in the active layer of the base wafer and depending from the mechanism die through one or more anchors; and

a plurality of discrete stress isolation structures formed in the active layer of the base wafer independent of the mechanism device and depending from the mechanism die through one or more anchors, the isolation structures being attached to the electrical interface pads on the surface of the package substrate.

9. The device of claim 8 wherein one or more of the discrete stress isolation structures further comprises a first portion attached to the mechanism die through the one or more anchors, and a second portion attached to the electrical interface pads on the surface of the package substrate, the first and second portions being linked by one or more flexures.

10. The device of claim 8, further comprising one or more stud bumps attaching the isolation structures to the electrical interface pads on the surface of the package substrate.

11. The device of claim 8, further comprising a cover plate attached to the mechanism device opposite from the mechanism die, the cover plate being formed with one or more apertures sized to provide clearance around each of isolator structures;

and

wherein the package substrate further comprises a clearance aperture structured to accommodate the cover plate.

12. The device of claim 8 wherein the mechanism device further comprises a device structured for measuring differential capacitance between different capacitors.

13. The device of claim 12 wherein the mechanism device further comprises one or more moveable portions structured for motion out of a plane of the mechanism device.

14. The device of claim 12 wherein the mechanism device further comprises one or more moveable portions structured for motion in a plane of the mechanism device.

15. A method for forming a Micro Electro-Mechanical System (MEMS) sensor device, the method comprising:

forming a plurality of electrical interface pads on a surface of a package substrate;

of a base wafer having a relatively thicker handle layer and a relatively thinner active layer,

forming a mechanism die in the handle layer,

forming a mechanism device in the active layer,

forming one or more anchors between the mechanism device and the mechanism die,

forming a plurality of discrete stress isolation structures in the active layer independently of the mechanism device,

forming one or more anchors between the isolation structures and the mechanism die, and

forming electrically conductive pathways between the mechanism device and one or more of the isolation structures; and

attaching the isolation structures to the electrical interface pads on the surface of the package substrate.

16. The method of claim 15 wherein the forming a plurality of discrete stress isolation structures in the active layer further comprises forming mutually isolated first and second stress isolation structure portions linked together by one or more flexures.

17. The method of claim 15 wherein the forming a plurality of discrete stress isolation structures further comprises forming one or more metallized bond pads on a surface of the isolation structures facing toward the surface of the package substrate;

and

wherein attaching the isolation structures to the electrical interface pads on the surface of the package substrate further comprises attaching one or more of the metallized bond pads on the surface of the isolation structures to a corresponding one of the electrical interface pads on the surface of the package substrate.

18. The method of claim 17 wherein the attaching one or more of the metallized bond pads on the surface of the isolation structures to a corresponding one of the electrical interface pads on the surface of the package substrate further comprises forming one or more stud bumps between the metallized bond pad on the surface of the isolation structures and the corresponding electrical interface pad on the surface of the package substrate.

19. The method of claim 15, further comprising attaching a cover plate to the mechanism device opposite from the mechanism die, including forming the cover plate with one or more apertures sized to provide clearance around each of isolator structures;

forming a clearance aperture in the package substrate, including structuring the clearance aperture to accommodate the cover plate; and

wherein the attaching the isolation structures to the electrical interface pads on the surface of the package substrate further comprises nesting the cover plate in the clearance aperture in the package substrate.

20. The method of claim 19 wherein structuring the clearance aperture to accommodate the cover plate further comprises forming one or more fingers within the clearance aperture positioned to interface with the isolation structures, the fingers forming the surface having the electrical interface pads formed thereon.