Integrated multi-axis micromachined inertial sensing unit and method of fabrication

• US 20090282917A1
• Filed: 05/19/2008
• Published: 11/19/2009
• Est. Priority Date: 05/19/2008
• Status: Abandoned Application

• Current Assignee: Custom Sensors & Technologies Incorporated (Schneider Electric SE)
• Original Assignee: Custom Sensors & Technologies Incorporated (Schneider Electric SE)
• Inventors: Acar, Cenk
• Application Number:
  US12/122,875
• Publication Number:
  US 20090282917A1
• Time in Patent Office: Days
• US Class Current: 73/514.20
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: H01L 2224/16145 the bodies being stacked
• CPC Class Codes: H01L 2224/48145 the bodies being stacked
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/181 Encapsulation

Abstract

Integrated micromachined inertial sensing unit with multi-axis angular rate and acceleration sensors and method of fabricating the same. Micromachined angular rate and acceleration sensors are integrated together with an application-specific integrated circuit (ASIC) in one compact package. The ASIC combines many separate functions required to operate multiple rate sensors and accelerometers into a single chip. The MEMS sensing elements and the ASIC are die-stacked, and electrically connected either directly using ball-grid-arrays or wirebonding. Through the use of a single package and single ASIC for multiple angular rate and acceleration sensors, significant reduction in cost is achieved.

Claims

1. An inertial sensing unit, comprising:

micromachined angular rate and acceleration sensors formed on at least one MEMS die, a single application specific integrated circuit (ASIC) die with operating circuitry for all of the sensors, the MEMS and ASIC dice being stacked together with at least one of the dice on top of another, electrical connections between the angular rate and acceleration sensors and the circuitry on the ASIC die, and a single package enclosing the stacked dice.

2. The inertial sensing unit of claim 1 wherein each MEMS die is hermetically encapsulated.

3. The inertial sensing unit of claim 1 wherein each MEMS die is flip-chip bonded to the ASIC die.

4. The inertial sensing unit of claim 1 wherein each MEMS die is adhesively bonded to the ASIC die, and the sensors are connected to the circuitry in the ASIC by wire bonding.

5. The inertial sensing unit of claim 1 wherein an angular rate sensor and an accelerometer are formed on a single MEMS die.

6. The inertial sensing unit of claim 1 wherein an angular rate sensor is formed on one MEMS die, and an accelerometer is formed on a second MEMS die.

7. The inertial sensing unit of claim 1 wherein a first angular rate sensor is formed on one MEMS die, a second angular rate sensor is formed on a second MEMS die, and an accelerometer is formed on a third MEMS die.

8. The inertial sensing unit of claim 1 wherein the sensors provide single-axis rate sensing and dual-axis acceleration sensing.

9. An inertial sensing unit, comprising:

a micromachined angular rate sensor and an acceleration sensor formed on a hermetically encapsulated MEMS die, a single application specific integrated circuit (ASIC) die with operating circuitry for both the angular rate sensor and the acceleration sensor, the MEMS die being stacked on top of the ASIC die with the sensors on the MEMS die being interconnected electrically with the circuitry on the ASIC die, and a single package enclosing the stacked dice.

10. The inertial sensing unit of claim 9 wherein the angular rate sensor is a dual-axis rate sensor.

11. The inertial sensing unit of claim 9 wherein the acceleration sensor is a dual-axis acceleration sensor.

12. An inertial sensing unit, comprising:

a micromachined angular rate sensor on a first hermetically encapsulated MEMS die, an acceleration sensor on a second hermetically encapsulated MEMS die, a single application specific integrated circuit (ASIC) die with operating circuitry for both the angular rate sensor and the acceleration sensor, the MEMS dice being stacked on top of the ASIC die with the sensors on the MEMS dice being interconnected electrically with the circuitry on the ASIC die, and a single package enclosing the stacked dice.

13. The inertial sensing unit of claim 12 wherein the angular rate sensor is a dual-axis rate sensor.

14. The inertial sensing unit of claim 12 wherein the acceleration sensor is a dual-axis acceleration sensor.

15. The inertial sensing unit of claim 12 including a second rate sensor on a third MEMS die, with the third MEMS die also being stacked on the ASIC die and the second rate sensor being interconnected electrically with the circuitry on the ASIC die.

16. A method of fabricating an inertial sensing unit, comprising the steps of:

forming angular rate and acceleration sensors on at least one MEMS die, stacking each MEMS die on top of a single application specific integrated circuit (ASIC) die with operating circuitry for all of sensors, interconnecting the sensors on each MEMS die with the circuitry on the ASIC die, and packaging the stacked dice in a single package.

17. The method of claim 16 including the step of hermetically encapsulating each MEMS die before the die is stacked on the ASIC die.

18. The method of claim 16 wherein an array of contact balls are formed on one side of each MEMS die, each MEMS die is placed on the ASIC die with the contact balls facing the ASIC die, and the contact balls are bonded to contact pads on the ASIC die.

19. The method of claim 16 wherein the sensors on each MEMS die are connected to contacts on the ASIC die by wirebonding.