High performance MEMS packaging architecture

• US 7,238,999 B2
• Filed: 01/21/2005
• Issued: 07/03/2007
• Est. Priority Date: 01/21/2005
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: LaFond, Peter H., Yu, Lianzhong
• Primary Examiner(s): Weiss; Howard
• Assistant Examiner(s): INGHAM, JOHN C
• Application Number:
  US11/040,208
• Publication Number:
  US 20060163679A1
• Time in Patent Office: 893 Days
• Field of Search: 257/417, 257/E27.006, 735/140.1, 735/142, 438/52
• US Class Current: 257/417
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• 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
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 Silicon [Si]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/10253 Silicon [Si]
• CPC Class Codes: H01L 2924/1461 MEMS

Abstract

An apparatus and method for sensor architecture based on bulk machining of Silicon-On-Oxide wafers and fusion bonding that provides a symmetric, nearly all-silicon, hermetically sealed MEMS device having a sensor mechanism formed in an active semiconductor layer, and opposing silicon cover plates each having active layers bonded to opposite faces of the sensor mechanism. The mechanism is structured with sensor mechanical features structurally supported by at least one mechanism anchor. The active layers of the cover plates each include interior features structured to cooperate with the sensor mechanical features and an anchor structured to cooperate with the mechanism anchor. A handle layer of each cover plate includes a pit extending there through in alignment with the cover plate anchor. An unbroken rim of dielectric material forms a seal between the cover plate anchor and the pit and exposes an external surface of the cover plate anchor.

Claims

1. A microelectromechanical system (MEMS) inertial device, comprising:

a mechanism formed in an active layer of silicon semiconductor material, the mechanism being structured with one or more sensor mechanical features structurally supported by at least one mechanism anchor;

a first cover plate formed of a Silicon-On-Oxide wafer having a semiconductor active layer separated from a semiconductor handle layer by a dielectric layer, the first cover plate active layer being structured with one or more interior cover plate features structured to cooperate with the sensor mechanical features and a cover plate anchor structured to cooperate with the mechanism anchor, the first cover plate handle layer being structured with a pit feature extending there through in alignment with the cover plate anchor, and the first cover plate dielectric layer being structured with an unbroken rim of material arranged to hermetically seal the cover late anchor to the first cover plate handle layer adjacent the pit feature while exposing a surface of the cover plate anchor to the pit feature, the cover plate anchor having a perimeter edge substantially aligned with a perimeter edge of the unbroken rim of the first cover plate dielectric layer;

wherein the cover plate pit feature is further structured having an inverse pyramid shape;

a frame formed in the mechanism active layer surrounding the one or more sensor mechanical features and the mechanism anchor and being bonded to a complementary frame formed in the first cover plate active layer; and

a second cover plate formed of a Silicon-On-Oxide wafer having a semiconductor active layer separated from a semiconductor handle layer by a dielectric layer, the second cover plate active layer being structured with one or more interior cover plate features structured to cooperate with the sensor mechanical features and a frame complementary to the frame formed in the mechanism active layer and being bonded thereto opposite from the first cover plate,

wherein the second cover plate is structured substantially the same as the first cover plate, including the second cover plate active layer being structured with one or more interior cover plate features structured to cooperate with the sensor mechanical features and a cover plate anchor structured to cooperate with the mechanism anchor, the second cover plate handle layer being structured with a pit feature extending there through in alignment with the cover plate anchor, and the second cover plate dielectric layer being structured with an unbroken rim of material arranged to hermetically seal the cover plate anchor to the semiconductor handle layer adjacent the pit feature while exposing a surface of the cover plate anchor to the pit feature; and

a bond formed between the mechanism anchor and the cover plate anchor.

2. The inertial device of claim 1, further comprising an electrically conductive connector formed in the first cover plate active layer between the cover plate anchor and one of the interior cover plate features, and a second cover plate anchor formed in the first cover plate active layer.

3. The inertial device of claim 1, further comprising a radially compliant isolator flange coupled to the frame surrounding the sensor mechanical features and the mechanism anchor.

4. The inertial device of claim 1 wherein the one or more sensor mechanical features of the mechanism and the one or more interior cover plate features formed in each of the first and second cover plate active layers are structured to form an electrostatic accelerometer.

5. The inertial device of claim 1 wherein the one or more sensor mechanical features of the mechanism and the one or more interior cover plate features formed in each of the first and second cover plate active layers are structured to form a Coriolis rate gyroscope.

6. A micro electromechanical system (MEMS) inertial device, comprising:

a sensor mechanism formed in an active layer of a Silicon-On-Oxide mechanism wafer, the sensor mechanism being structured with one or more sensor mechanical features structurally supported by one or more mechanism anchors positioned in a first pattern relative to the sensor mechanical features;

first and second cover plates formed of respective first and second Silicon-On-Oxide cover plate wafers each having a semiconductor active layer separated from a semiconductor handle layer by a relatively thin dielectric layer wherein;

the active layer of at least one of the first and second cover plates is structured with one or more interior cover plate features that are structured to cooperate with the sensor mechanical features, and is further structured with one or more cover plate anchors positioned in a second pattern that is structured to cooperate with the pattern of mechanism anchors,

the handle layer of the cover plate that is structured with the one or more interior cover plate features and the cover plate anchors is further structured with a pit feature in alignment with one or more of the cover plate anchors that extends through the handle layer from the cover plate anchor to an exterior surface of the handle layer,

a portion of each dielectric layer is arranged as a continuous marginal rim adjacent the pit feature to hermetically seal the cover plate anchor to the handle layer adjacent the pit feature while exposing a surface of the cover plate anchor to the pit feature, the cover plate anchor includes a perimeter edge substantially aligned a perimeter edge of the continuous marginal rim,

wherein both the first and second cover plates are structured with the one or more cover plate anchors positioned in a second pattern that is structured to cooperate with the pattern of mechanism anchors, the handle layer of both the first and second cover plates is structured with the pit feature in alignment with one or more of the cover plate anchors, and the dielectric layer includes the continuous marginal rim; and

a radially compliant isolator flange coupled to the continuous marginal frame surrounding the sensor mechanical features and mechanism anchors.

7. The inertial device of claim 6, wherein the active layer the Silicon-On-Oxide mechanism wafer further comprises a continuous marginal frame completely surrounding the sensor mechanical features and mechanism anchors, and the active layer both the first and second cover plates further comprises a complementary continuous marginal frame bonded to respective first and second surfaces of the mechanism continuous marginal frame.

8. The inertial device of claim 6 wherein the one or more sensor mechanical features of the sensor mechanism and the one or more interior cover plate features formed in each of the first and second cover plate active layers are structured to form an electrostatic accel erometer.

9. The inertial device of claim 6 wherein the one or more sensor mechanical features of the sensor mechanism and the one or more interior cover plate features formed in each of the first and second cover plate active layers are structured to form a Coriolis rate gyroscope.

10. A microelectromechanical system (MEMS) inertial device comprising:

one or more sensor mechanical features structurally supported by one or more mechanism anchors, the sensor mechanical features and mechanism anchors being formed in a semiconductor material active layer of a first Silicon-On-Oxide wafer having a dielectric material layer between a semiconductor material handle layer and the semiconductor material active layer;

one or more interior cover plate features structured to cooperate with the sensor mechanical features to form an inertial device, the interior cover plate features being formed in a semiconductor material active layer of a second Silicon-On-Oxide wafer having a dielectric material layer between a semiconductor material handle layer and the semiconductor material active layer;

one or more cover plate anchors structured to cooperate with the mechanism anchors, the cover plate anchors being formed in the semiconductor material active layer of the second Silicon-On-Oxide wafer;

a pit feature extending through the semiconductor material handle layer of the second Silicon-On-Oxide wafer in alignment with one of the cover plate anchors;

a window formed through the dielectric material layer of the second Silicon-On-Oxide wafer, the window forming an unbroken rim of dielectric material between the cover plate anchor and the pit feature in alignment therewith;

a surface of the cover plate anchor proximate to and in alignment with the cover plate pit feature being exposed through the window formed through the dielectric material layer of the second Silicon-On-Oxide wafer;

a first surface of the mechanism anchors coupled to a surface of the cooperating cover plate anchors opposite from the cover plate dielectric and handle layers with the interior cover plate features positioned relative to the sensor mechanical features for cooperating therewith,

wherein the semiconductor material handle layer and dielectric material layer of the first Silicon-On-Oxide wafer are removed;

a radially compliant isolator coupled to an external surface of a substantially continuous marginal frame, which is formed in the semiconductor material active layer of the first Silicon-On-Oxide wafer, the continuous marginal frame arranged to substantially surround the sensor mechanical features and one or more of the mechanism anchors;

a third Silicon-On-Oxide wafer having a dielectric material layer between a semiconductor material handle layer and the semiconductor material active layer;

one or more interior cover plate features formed in the semiconductor material active layer of the third Silicon-On-Oxide wafer, the interior cover plate features being structured to cooperate with the sensor mechanical features to form an inertial device;

one or more cover plate anchors formed in the semiconductor material active layer of the third Silicon-On-Oxide wafer, the cover plate anchors being structured to cooperate with the mechanism anchors;

a pit feature extending through the semiconductor material handle layer of the third Silicon-On-Oxide wafer in alignment with one of the cover plate anchors;

a window formed through the dielectric material layer of the third Silicon-On-Oxide wafer, the window forming an unbroken rim of dielectric material between the cover plate anchor and the pit feature in alignment therewith; and

a surface of the cover plate anchor proximate to and in alignment with the cover plate pit feature being exposed through the window formed through the dielectric material layer of the third Silicon-On-Oxide wafer.

11. The device of claim 10, further comprising:

in the respective semiconductor material active layer of the second and third Silicon-On-Oxide wafers, a substantially continuous marginal frame being formed corresponding to the marginal frame formed in the semiconductor material active layer of the first Silicon-On-Oxide wafer;

a first surface of the marginal frame formed in the active layer of the first Silicon-On-Oxide wafer being coupled to a surface of the corresponding marginal frame formed in the active layer of the second Silicon-On-Oxide wafer; and

a second surface of the marginal frame formed in the active layer of the first Silicon-On-Oxide wafer opposite from the first surface thereof being coupled to a surface of the corresponding marginal frame formed in the active layer of the third Silicon-On-Oxide wafer.

12. The device of claim 10, wherein the inertial device further comprises an accelerometer.