Vacuum package fabrication of microelectromechanical system devices with integrated circuit components

• US 6,479,320 B1
• Filed: 02/02/2000
• Issued: 11/12/2002
• Est. Priority Date: 02/02/2000
• Status: Expired due to Term

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Gooch, Roland W.
• Primary Examiner(s): Sherry, Michael
• Assistant Examiner(s): GEYER, SCOTT B
• Application Number:
  US09/496,826
• Time in Patent Office: 1,014 Days
• Field of Search: 438/106, 438/107, 438/125, 438/455, 438/456, 438/109, 257/204, 257/678
• US Class Current: 438/109
• CPC Class Codes: B81B 2207/097 Interconnects arranged on the substrate or the lid, and covered by the package seal
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals

Abstract

A method for vacuum packaging MEMS devices is provided that comprises forming a plurality of MEMS devices (12) on a device wafer (10). A first sealing ring (16) is formed surrounding one of the MEMS devices (12) and any associated mating pads (70). A plurality of integrated circuit devices (80) is formed on a lid wafer (30) where each integrated circuit device (80) has one or more associated mating pads (82) and one or more associated bonding pads (86). A plurality of second sealing rings (32) is formed on the lid wafer (30) where each of the second sealing rings (32) surrounds one of the integrated circuit devices (80) and any associated bonding pads (82). The second sealing ring (32) is positioned between the perimeter of the integrated circuit device (80) and the associated bonding pads (86). A sealing layer is formed on either each first sealing ring (16) or each second sealing ring (32). The device wafer (10) is mated with the lid wafer (30) in a vacuum environment to form a plurality of vacuum packages where each vacuum package encloses one or more of the MEMS devices (12) and one or more of the integrated circuit devices (80).

Claims

1. A method for vacuum packaging MEMS devices during the MEMS fabrication process, comprising:

fabricating on a device wafer a plurality of MEMS devices;

fabricating one or more device mating pads on the device wafer, the device mating pads selectively coupled to the MEMS devices;

forming a plurality of first sealing rings surrounding both one of the plurality of MEMS devices and the one or more device mating pads selectively coupled to the MEMS device;

fabricating on a lid wafer a plurality of CMOS or other integrated circuit devices;

fabricating one or more lid mating pads on the lid wafer, the one or more lid mating pads corresponding in position to the one or more device mating pads selectively coupled to the MEMS devices to enable selective electrical connection of the CMOS or other integrated circuit devices to selected MEMS devices;

fabricating one or more bonding pads on either the one or more device mating pads or the one or more lid mating pads;

forming on the lid wafer a plurality of second sealing rings, each of the plurality of second sealing rings surrounding one of the plurality of CMOS or other integrated circuit devices and the one or more mating pads of the CMOS or other integrated circuit devices, each of the plurality of second sealing rings positioned between the perimeter of the CMOS or other integrated circuit device and one or more bonding pads coupled to the CMOS or other integrated circuit device;

forming a sealing layer on either each of the plurality of first sealing rings or on each of the plurality of second sealing rings; and

mating the device wafer with the lid wafer in a vacuum environment to form a vacuum package within each of the plurality of first sealing rings and second sealing rings, each vacuum package enclosing one or more of the plurality of MEMS devices and one or more of the CMOS or other integrated circuit devices thereby selectively interconnected through one or more bonding pads.

2. The method of claim 1, wherein forming a plurality of first sealing rings comprises first forming a dielectric layer ring surrounding both one of the plurality of MEMS devices and one or more mating pads coupled to the MEMS device.

3. The method of claim 2, wherein forming a plurality of first sealing rings comprises forming a solder adhesion surface on each of the plurality of dielectric layer rings.

4. The method of claim 3, wherein forming a plurality of solder adhesion surfaces comprises:

depositing a layer of titanium;

depositing a layer of palladium on the layer of titanium; and

depositing a layer of gold on the layer of palladium.

5. The method of claim 1, wherein mating the device wafer with the lid wafer comprises:

aligning the device wafer with the lid wafer to align the plurality of first sealing rings with the plurality of second sealing rings leaving a gap between the device wafer and the lid wafer;

placing the aligned device wafer and lid wafer in a vacuum furnace;

generating a vacuum within the vacuum furnace;

closing the gap between the device wafer and lid wafer thereby contacting the plurality of first sealing rings with the plurality of second sealing rings creating a plurality of vacuum packages, each vacuum package enclosing one or more of the plurality of MEMS devices and one or more of the CMOS or other integrated circuit devices.

6. The method of claim 1, wherein mating the device wafer with the lid wafer comprises:

aligning the device wafer with the lid wafer to align the plurality of first sealing rings with the plurality of second sealing rings leaving a gap between the device wafer and the lid wafer;

placing the aligned device wafer and lid wafer in a vacuum furnace;

generating a vacuum within the vacuum furnace;

outgassing surface areas of the device wafer and lid wafer assembly by heating the vacuum furnace to a temperature sufficient to outgas the surface areas;

closing the gap between the device wafer and lid wafer thereby contacting the plurality of first sealing rings with the plurality of second sealing rings creating a plurality of vacuum packages, each vacuum package enclosing one or more of the plurality of MEMS devices and one or more of the CMOS or other integrated circuit devices; and

cooling the completed device wafer and lid wafer assembly at a rate determined to minimize subsequent outgassing of surfaces within the plurality of vacuum packages while minimizing thermal stresses on the plurality of vacuum packages.

7. The method of claim 1, wherein mating the device wafer with the lid wafer comprises:

aligning the device wafer with the lid wafer to align the plurality of first sealing rings with the plurality of second sealing rings leaving a gap between the device wafer and the lid wafer;

placing the aligned device wafer and lid wafer in a vacuum furnace;

heating and generating a vacuum within the vacuum furnace;

closing the gap between the device wafer and lid wafer thereby contacting the plurality of first sealing rings with the plurality of second sealing rings creating a plurality of vacuum packages, each vacuum package enclosing one or more of the plurality of MEMS devices and one or more of the CMOS or other integrated circuit devices; and

cooling the completed device wafer and lid wafer assembly at a rate determined to minimize subsequent outgassing of surfaces within the plurality of vacuum packages while minimizing thermal stresses on the plurality of vacuum packages.

8. The method of claim 1, wherein forming a sealing layer comprises forming an indium compression seal on each of the second sealing rings.

9. The method of claim 1, further comprising:

coating the inner surface of the lid wafer within each of the second sealing rings with an anti-reflective coating; and

coating the outer surface of the lid wafer with an anti-reflective coating.

10. The method of claim 1, further comprising:

forming one or more spacers on the plurality of second sealing rings.

11. The method of claim 1, further comprising:

forming one or more bonding pad channels in the device wafer corresponding in location to the bonding pads on the lid wafer.

12. A method for vacuum packaging MEMS devices during the MEMS fabrication process, comprising:

fabricating on a device wafer a plurality of MEMS devices;

fabricating one or more device mating pads on the device wafer, the mating pads selectively coupled to the MEMS devices;

forming a plurality of first sealing rings surrounding both one of the plurality of MEMS devices and the one or more mating pads selectively coupled to the MEMS device;

fabricating on a lid wafer a plurality of CMOS or other integrated circuit devices;

fabricating one or more lid mating pads on the lid wafer, the one or more lid mating pads corresponding in position to the one or more device mating pads selectively coupled to the MEMS device to enable selective electrical connection of the CMOS or other integrated circuit devices to selected MEMS devices;

fabricating one or more bonding pads on either the one or more device mating pads or the one or more lid mating pads;

forming on the lid wafer a plurality of second sealing rings, each of the plurality of second sealing rings surrounding one of the plurality of CMOS or other integrated circuit devices and the one or more lid mating pads of the CMOS or other integrated circuit devices, each of the plurality of second sealing rings positioned between the perimeter of the CMOS or other integrated circuit device and one or more bonding pads coupled to the COMOS or other integrated circuit device;

forming a solder layer on either each of the plurality of first sealing rings or on each of the plurality of second sealing rings; and

mating the device wafer with the lid wafer in a vacuum environment to form a vacuum package within each of the plurality of first sealing rings and second sealing rings, each vacuum package enclosing one or more of the plurality of MEMS devices and one or more of the CMOS or other integrated circuit devices thereby selectively interconnected through one or more bonding pads.

13. The method of claim 12, further comprising:

heating the solder layer prior to mating the device wafer with the lid wafer.

14. The method of claim 12, wherein depositing a solder layer comprises positioning a preform solder pattern in alignment with either the plurality of first sealing rings or the plurality of second sealing rings.

15. The method of claim 12, wherein depositing a solder layer comprises electroplating a wafer to deposit the solder layer.

16. The method of claim 12, wherein depositing a solder layer comprises vacuum deposition of the solder layer.

17. The method of claim 12, wherein depositing a solder layer comprises electroless plating.

18. The method of claim 12, wherein forming a plurality of second sealing rings comprises forming on a lid wafer a plurality of solder adhesion surfaces corresponding in number and location to the plurality of first sealing rings.

19. A method for vacuum packaging MEMS devices during the MEMS fabrication process, comprising:

fabricating on a device wafer a plurality of MEMS devices;

fabricating one or more device mating pads on the device wafer, the mating pads selectively coupled to the MEMS devices;

fabricating on a lid wafer a plurality of CMOS or other integrated circuit devices;

fabricating one or more lid mating pads on the lid wafer, the one or more lid mating pads corresponding in position to the one or more device mating pads selectively coupled to the MEMS device to enable selective electrical connection of the CMOS or other integrated circuit devices to selected MEMS devices;

fabricating one or more bonding pads on either the one or more device mating pads or the one or more lid mating pads;

forming on the lid wafer a plurality of second sealing rings, each of the plurality of second sealing rings surrounding one of the plurality of CMOS or other integrated circuit devices and the one or more mating pads of the CMOS or other integrated circuit devices, each of the plurality of second sealing rings positioned between the perimeter of the CMOS or other integrated circuit device and one or more bonding pads coupled to the CMOS or other integrated circuit device;

forming a sealing layer on either each of the plurality of first sealing rings or on each of the plurality of second sealing rings;

mating the device wafer with the lid wafer in a vacuum environment to form a vacuum package within each of the plurality of first sealing rings and second sealing rings, each vacuum package enclosing one or more of the plurality of MEMS devices and one or more of the CMOS or other integrated circuit devices thereby selectively interconnected through one or more bonding pads;

opening a plurality of probe access channels in the lid wafer following the formation of a plurality of vacuum packages, the plurality of probe access channels providing access to the bonding pads for testing of a plurality of vacuum packaged integrated circuit devices;

testing each of the plurality of vacuum packaged integrated circuit devices by probing the bonding pads coupled to each integrated circuit device; and

dicing the plurality of vacuum packaged integrated circuit devices following testing thereof.

20. The method of claim 19 further comprising:

forming a plurality of cavities on the lid wafer, each of the plurality of cavities formed within and surrounded by one of the plurality of second sealing rings, the cavities formed so as to not interfere with the CMOS or other integrated circuit devices and the one or more mating pads enclosed within each of the plurality of second sealing rings.

21. The method of claim 20, wherein forming a plurality of cavities comprises etching a plurality of pits in the lid wafer, each pit surrounded by one of the plurality of second sealing rings thereby leaving a cavity surrounded by one of the plurality of second sealing rings.

22. A vacuum package containing a MEMS device and one or more integrated circuit devices, comprising:

a MEMS device fabricated on a device wafer;

one or more device mating pads fabricated on the device wafer, the device mating pads selectively coupled to the MEMS device;

a sealing ring formed around the perimeter of the MEMS device and the one or more device mating pads associated with the MEMS device, the sealing ring surrounding the MEMS device and the device mating pads;

one or more integrated circuit devices fabricated on a lid wafer;

one or more lid mating pads fabricated on the lid wafer, the one or more lid mating pads corresponding in location to the one or more device mating pads to enable selective electrical connection of the MEMS device to the one or more integrated circuit devices;

one or more bonding pads on either of the one or more device mating pads or the one or more lid mating pads; and

wherein the sealing ring seals the lid wafer to the device wafer providing a vacuum package enclosing the MEMS device and the one or more integrated circuit devices, each of the one or more device mating pads coupled to the corresponding one of the one or more lid mating pads by the one or more bonding pads.

23. The device of claim 22, further comprising:

one or more spacers formed on the sealing ring.