Substrate Bonding with Bonding Material Having Rare Earth Metal

• US 20100062565A1
• Filed: 05/04/2009
• Published: 03/11/2010
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Tsau, Christine H., Frey, Timothy J., Martin, John R.
• Granted Patent: US 7,981,765 B2
• Time in Patent Office: Days
• US Class Current: 438/107
• CPC Class Codes: B81C 1/00269 Bonding of solid lids or wafers to the substrate
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: H01L 23/10 characterised by the material or arrangement of seals between parts, e.g. between cap and base of the container or between leads and walls of the container
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/01079 Gold [Au]

Abstract

A microchip has a bonding material that bonds a first substrate to a second substrate. The bonding material has, among other things, a rare earth metal and other material.

Claims

1. A microchip comprising:

a first substrate;

a second substrate; and

a bonding material bonding the first and second substrates, the bonding material comprising a rare earth metal and other material.

2. The microchip as defined by claim 1 wherein the first substrate comprises a chip or a wafer and the second substrate comprises a chip or a wafer.

3. The microchip as defined by claim 1 wherein the first substrate comprises a wafer having a plurality of MEMS devices, the second substrate comprising a wafer having a plurality of caps, the bonding material forming a plurality of sealing rings hermetically sealing the MEMS devices.

4. The microchip as defined by claim 1 wherein the first substrate has an interior surface, the bonding material substantially covering the interior surface.

5. The microchip as defined by claim 1 wherein the other material does not readily bond with the first substrate in the absence of the rare earth metal.

6. The microchip as defined by claim 1 wherein the bonding material electrically connects the first substrate and the second substrate.

7. The microchip as defined by claim 1 wherein the bonding material forms a seal ring having a width of less than about 100 microns.

8. The microchip as defined by claim 1 wherein the first substrate has at least one pedestal ring with a top surface, the bonding material being between the second substrate and the top surface of the pedestal ring.

9. A method of bonding a first substrate and a second substrate, the method comprising:

forming at least one pedestal ring on the first substrate;

disposing bonding material comprising a rare earth metal onto at least one of the pedestal ring and the second substrate;

contacting the second substrate with the at least one pedestal ring on the first substrate, the bonding material being between the at least one pedestal ring and second substrate; and

heating the bonding material to cause the bonding material to bond with at least one of the first substrate and the second substrate.

10. The method as defined by claim 9 wherein at least one of the first and second substrates includes a plurality of MEMS inertial sensors.

11. The method as defined by claim 9 wherein disposing bonding material comprises forming, within the bonding material, a layer enriched with a rare earth metal.

12. The method as defined by claim 9 wherein heating comprises heating the bonding material before contacting the first and second substrates, heating being in at least one of a vacuum and a forming gas environment.

13. The method as defined by claim 9 wherein one of the substrates includes integrated circuits, the bonding material comprising one of aluminum or an aluminum alloy used as an interconnect material in the integrated circuits.

14. The method as defined by claim 9 wherein the second substrate comprises a non-metallic material comprising at least one of silicon, polysilicon, silicon-germanium, and silicon nitride, at least a portion of the bonding material bonding with the non-metallic material.

15. The method as defined by claim 9 wherein at least one of the substrates includes electronic circuitry.

16. The method as defined by claim 9 wherein at least one of the substrates comprises a plurality of MEMS devices.

17. The method as defined by claim 9 further comprising:

adding a cover material to the bonding material to mitigate oxidation of the bonding material, adding being performed before contacting the second substrate with the at least one pedestal ring.

18. The method as defined by claim 9 wherein heating comprises forming a thermocompression bond between the first substrate and the second substrate.

19. The method as defined by claim 9 wherein heating comprises forming a solder bond with a CMOS fabrication process compatible metal alloy between the first substrate and the second substrate.

20. The method as defined by claim 9 wherein the first substrate is one of a wafer or a chip, the second substrate being one of a wafer or a chip.

21. The method as defined by claim 9 wherein heating forms a hermetic seal.

22. The method as defined by claim 9 wherein the bond material electrically connects the first substrate and the second substrate.

23. The method as defined by claim 9 wherein the first substrate comprises a wafer, the second substrate comprising a wafer, the method further comprising:

at least partially dicing the first and second bonded wafers to produce a plurality of individual chips.

24. The method as defined by claim 9 wherein the first substrate comprises a micro-electromechanical structure, the second substrate forming a cap about the micro-electromechanical structure.

25. The method as defined by claim 9 wherein the bonding material has a width that is generally parallel to the surface of the second substrate, the width being no greater than about 100 microns.

26. The method as defined by claim 9 wherein disposing comprises disposing the bonding material across at least a portion of an interior surface of the second substrate.

27. The method as defined by claim 9 wherein contacting comprises aligning the first substrate and the second substrate.

28. A method of bonding a MEMS wafer to a second wafer, the method comprising:

providing the MEMS wafer with a two-dimensional array of MEMS devices;

providing the second wafer;

depositing a metal alloy onto one or both the MEMS wafer and the second wafer, the metal alloy comprising a rare earth metal;

aligning the MEMS wafer and the second wafer;

forming an intermediate apparatus having the metal alloy between the MEMS wafer and the second wafer;

heating the intermediate apparatus at least to within 75 degrees C. of the melting point of the metal alloy between the MEMS wafer and the second wafer; and

cooling the wafers to form a plurality of conductive hermetic sealing rings about the plurality of the MEMS devices on the MEMS wafer, the sealing rings bonding the MEMS wafer to the second wafer.

29. The method as defined by claim 28 wherein the metal alloy further comprises aluminum/germanium.

30. The method as defined by claim 28 further comprising dicing the wafers to form a plurality of individual, hermetically sealed MEMS devices.