ISOLATED ACTIVE TEMPERATURE REGULATOR FOR VACUUM PACKAGING OF A DISC RESONATOR GYROSCOPE

• US 20100300201A1
• Filed: 05/27/2009
• Published: 12/02/2010
• Est. Priority Date: 05/27/2009
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Ge, Howard H., Challoner, A. Dorian
• Granted Patent: US 8,327,526 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 7/0048 between the MEMS die and the substrate
• CPC Class Codes: B81B 7/0096 by heating
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: Y10T 29/49007 Indicating transducer
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor
• CPC Class Codes: Y10T 29/49083 Heater type
• CPC Class Codes: Y10T 29/49105 Switch making

Abstract

A micromachined thermal and mechanical isolator for MEMS die that may include two layers, a first layer with an active temperature regulator comprising a built-in heater and temperature sensor and a second layer having mechanical isolation beams supporting the die. The isolator may be inserted between a MEMS die of a disc resonator gyroscope (DRG) chip and the leadless chip carrier (LCC) package to isolate the die from stress and temperature gradients. Thermal and mechanical stress to the DRG can be significantly reduced in addition to mitigating temperature sensitivity of the DRG chip. The small form can drastically reduce cost and power consumption of the MEMS inertial sensor and enable new applications such as smart munitions, compact and integrated space navigation solutions, with significant potential cost savings over the existing inertial systems.

Claims

1. An apparatus for isolating a MEMS die, comprising:

a top layer comprising a resistive heater for regulating temperature of the MEMS die; and

a bottom layer comprising a bottom layer central region, one or more bottom layer periphery regions and a plurality of substantially radial bottom layer isolation beams, each extending from the bottom layer central region to one of the one or more bottom layer periphery regions;

wherein an upper surface of the top layer is bonded to the MEMS die and a lower surface of the top layer is bonded to the bottom layer and a temperature sensor is used with the resistive heater to regulate the temperature of the MEMS die.

2. The apparatus of claim 1, wherein the temperature sensor comprises a frequency difference between a stable clock frequency and a resonant frequency of the MEMS die and regulating the temperature of the MEMS die is performed by operating the resistive heater such that the frequency difference is maintained at a substantially constant value.

3. The apparatus of claim 1, wherein the temperature sensor is disposed on the top layer.

4. The apparatus of claim 1, wherein the top layer and the bottom layer are bonded at one or more top layer periphery regions and the one or more bottom layer periphery regions.

5. The apparatus of claim 4, wherein the one or more bottom layer periphery regions comprise a bottom layer outer frame.

6. The apparatus of claim 5, wherein the lower surface of the top layer is bonded to the bottom layer outer frame.

7. The apparatus of claim 1, wherein the top layer further comprises a top layer central region, one or more top layer periphery regions, and a plurality of substantially radial top layer isolation beams, each extending from the top layer central region to one of the one or more top layer periphery regions.

8. The apparatus of claim 7, wherein the lower surface of the top layer is bonded at the top layer central region to the bottom layer central region.

9. The apparatus of claim 1, wherein the MEMS die comprises a disc resonator having embedded electrostatic electrodes having sidewalls that interact with interior sidewalls of the disc resonator such that vibration modes of the disc resonator are driven and sensed with the embedded electrostatic electrodes to measure motion of the disc resonator;

and

a baseplate having a topside bonded to support the disc resonator and having electrical traces coupled from the embedded electrostatic electrodes and to a baseplate periphery;

wherein the baseplate is bonded to the upper surface of the top layer.

10. The apparatus of claim 9, further comprising a vacuum package comprising electrical feedthroughs where the electrical feedthroughs are coupled to wire bonds which are coupled in turn to the electrical traces at the baseplate periphery;

wherein the bottom layer is bonded to a bottom interior of the vacuum package.

11. The apparatus of claim 10, wherein the vacuum package comprises a lid including a getter material activated to assist producing a vacuum within the vacuum package and the lid is bonded to close out the vacuum package.

12. The apparatus of claim 1, wherein each of the plurality of substantially radial bottom layer isolation beams comprises a plurality of circumferential segments and radial segments connected in series.

13. The apparatus of claim 1, wherein the top layer and the bottom layer comprise a semiconductor material selected from the group consisting of oxidized silicon and fused silica.

14. A method of producing an isolator for a MEMS die, comprising:

producing a top layer comprising a resistive heater for regulating temperature of the MEMS die;

etching a bottom layer comprising a bottom layer central region, one or more bottom layer periphery regions and a plurality of substantially radial bottom layer isolation beams, each extending from the bottom layer central region to one of the one or more bottom layer periphery regions;

bonding a lower surface of the top layer to the bottom layer; and

bonding an upper surface of the top layer to the MEMS die;

wherein a temperature sensor is used with the resistive heater to regulate the temperature of the MEMS die.

15. The method of claim 14, wherein the temperature sensor comprises a frequency difference between a stable clock frequency and a resonant frequency of the MEMS die and regulating the temperature of the MEMS die is performed by operating the resistive heater such that the frequency difference is maintained at a substantially constant value.

16. The method of claim 14, wherein the top layer is produced comprising the temperature sensor.

17. The method of claim 14, wherein the top layer and the bottom layer are bonded at one or more top layer periphery regions and the one or more bottom layer periphery regions.

18. The method of claim 17, wherein the one or more bottom layer periphery regions comprise a bottom layer outer frame.

19. The method of claim 18, wherein bonding the lower surface of the top layer to the bottom layer comprises bonding the lower surface of the top layer to the bottom layer outer frame.

20. The method of claim 14, further comprising etching the top layer to form a top layer central region, one or more top layer periphery regions, and a plurality of substantially radial top layer isolation beams, each extending from the top layer central region to one of the one or more top layer periphery regions.

21. The method of claim 20, wherein the lower surface of the top layer is bonded at the top layer central region to the bottom layer central region.

22. The method of claim 14, wherein the MEMS die comprises a disc resonator having embedded electrostatic electrodes having sidewalls that interact with interior sidewalls of the disc resonator such that vibration modes of the disc resonator are driven and sensed with the embedded electrostatic electrodes to measure motion of the disc resonator;

and

a baseplate having a topside bonded to support the disc resonator and having electrical traces coupled from the embedded electrostatic electrodes and to a baseplate periphery;

wherein the baseplate is bonded to the upper surface of the top layer.

23. The method of claim 22, further comprising a vacuum package comprising electrical feedthroughs where the electrical feedthroughs are coupled to wire bonds which are coupled in turn to the electrical traces at the baseplate periphery;

wherein the bottom layer is bonded to a bottom interior of the vacuum package.

24. The method of claim 23, wherein the vacuum package comprises a lid including a getter material activated to assist producing a vacuum within the vacuum package and the lid is bonded to close out the vacuum package.

25. The method of claim 14, wherein each of the plurality of substantially radial bottom layer isolation beams comprises a plurality of circumferential segments and radial segments connected in series.

26. The method of claim 14, wherein the top layer and the bottom layer comprise a semiconductor material selected from the group consisting of oxidized silicon and fused silica.

27. An apparatus for isolating a MEMS die, comprising:

a top layer comprising a temperature isolation means for substantially actively regulating a temperature of the MEMS die; and

a bottom layer comprising mechanical isolation means for substantially isolating vibration of the MEMS die;

wherein an upper surface of the top layer is bonded to the MEMS die and a lower surface of the top layer is bonded to the bottom layer.

28. The disc resonator gyroscope of claim 27, wherein the MEMS die comprises a disc resonator die.