Vertically integrated MEMS structure with electronics in a hermetically sealed cavity

• US 7,104,129 B2
• Filed: 02/02/2004
• Issued: 09/12/2006
• Est. Priority Date: 02/02/2004
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Nasiri, Steven S., Flannery, Anthony Francis Jr.
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US10/770,838
• Publication Number:
  US 20050166677A1
• Time in Patent Office: 953 Days
• Field of Search: 735/142.9, 735/141.6, 735/143.2, 735/041.2, 735/040.4, 438 48- 55, 438107-108, 438455-456, 438612-613, 438/64
• US Class Current: 73/514.29
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81C 1/0023 Packaging together an electronic processing unit die and a micromechanical structure die MEMS packages B81B7/0032; MEMS packaging processes B81C1/00261
• CPC Class Codes: B81C 2201/019 Bonding or gluing multiple substrate layers
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• 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: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H03H 9/1057 for microelectro-mechanical devices

Abstract

A MEMS assembly having a MEMS subassembly sandwiched between and bonded to a cap and a base is provided. The MEMS subassembly includes at least one MEMS device element flexibly connected to the MEMS assembly. The vertical separation between the MEMS device element and an electrode on the base is lithographically defined. Precise control of this critical vertical gap dimension is thereby provided.

Claims

1. A vertically integrated microelectromechanical (MEMS) assembly comprising:

a MEMS subassembly including a substantially planar frame and at least one MEMS device element within the frame and flexibly connected to the assembly;

a cap bonded to the frame with a first bond, the first bond being substantially parallel to the frame; and

a base bonded to a surface of the frame facing away from the cap with a second bond;

wherein a gap between an electrode on the base and the MEMS device element is defined by a lithographic feature on the frame;

whereby precise control of the gap is provided and the at least one MEMS device element is enclosed within a cavity.

2. The MEMS assembly of claim 1, wherein the gap between the electrode and the MEMS device element is not equal to a height of the lithographic feature on the frame.

3. The MEMS assembly of claim 1, wherein the gap between the electrode and the MEMS device element is equal to a height of the lithographic feature on the frame.

4. The MEMS assembly of claim 1, wherein the gap is in a range from about 1 micron to about 10 microns.

5. The MEMS assembly of claim 1, wherein the gap is less than about 2 microns.

6. The MEMS assembly of claim 1, further comprising an electrostatic actuator including the electrode for moving the MEMS device element.

7. The MEMS assembly of claim 1, wherein the cap comprises an electrically insulating layer bonded to the frame.

8. The MEMS assembly of claim 1, wherein the cap includes a recess permitting motion of the MEMS device element.

9. The MEMS assembly of claim 1, wherein the cavity is hermetically sealed.

10. The MEMS assembly of claim 9, wherein a gas pressure within the cavity is other than atmospheric pressure.

11. The MEMS assembly of claim 9, wherein a gas within the cavity comprises dry nitrogen, dry air, He, or Ar.

12. The MEMS assembly of claim 1, wherein the base includes a recess permitting motion of the MEMS device element.

13. The MEMS assembly of claim 1, wherein the base further comprises circuitry electrically connected to the MEMS subassembly.

14. The MEMS assembly of claim 13, wherein the circuitry comprises CMOS circuitry.

15. The MEMS assembly of claim 13, wherein the circuitry comprises multilayer metallization, whereby electrical feed through from within the cavity to outside the cavity is provided.

16. The MEMS assembly of claim 13, wherein the second bond is an AlGe bond between Ge on the frame and Al on the base, and wherein the Al is provided by the same processing that provides the circuitry.

17. The MEMS assembly of claim 13, further comprising selective electrical contacts between the frame and the circuitry.

18. A MEMS device comprising a plurality of MEMS assemblies according to claim 1 having a common cap and a common base.