Encapsulated MEMS device and method to form the same

• US 8,349,635 B1
• Filed: 05/20/2008
• Issued: 01/08/2013
• Est. Priority Date: 05/20/2008
• Status: Active Grant

• Current Assignee: Semiconductor Manufacturing International (Shanghai) Corporation (Semiconductor Manufacturing International Corporation)
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Gan, Qing, Quevy, Emmanuel P.
• Primary Examiner(s): Stark, Jarrett
• Assistant Examiner(s): Fan, Michele
• Application Number:
  US12/124,043
• Time in Patent Office: 1,694 Days
• Field of Search: 438 50- 52, 438 54- 55, 257/E23.001, 257/E23.18, 257/E29.324, 257/E21.48, 257/E21.519
• US Class Current: 438/50
• CPC Class Codes: B81B 7/0038 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81B 7/0064 for protecting against electromagnetic or electrostatic interferences
• CPC Class Codes: G01C 19/5783 Mountings or housings not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719
• CPC Class Codes: G01L 9/0019 of a semiconductive element
• CPC Class Codes: G01P 2015/088 for providing wafer-level encapsulation

Abstract

An encapsulated MEMS device and a method to form an encapsulated MEMS device are described. An apparatus includes a first substrate having a silicon-germanium seal ring disposed thereon and a second substrate having a metal seal ring disposed thereon. The metal seal ring is aligned with and bonded to the silicon-germanium seal ring to provide a sealed cavity. A MEMS device is housed in the sealed cavity. A method includes forming a silicon-germanium seal ring on a first substrate and forming a metal seal ring on a second substrate. The metal seal ring is bonded to the silicon-germanium seal ring to provide a sealed cavity that houses a MEMS device.

Claims

1. A method, comprising:

forming a silicon-germanium seal ring on a first substrate on which a MEMS device is disposed inside of a region enclosed by the silicon-germanium seal ring;

forming a vertical seal ring stack on a second substrate, the vertical seal ring stack including a metal seal ring;

forming a metal shielding layer on said second substrate including on a sidewall of the vertical seal ring stack;

bonding said metal seal ring to said silicon-germanium seal ring to provide a sealed cavity that houses the MEMS device, and to electrically couple the MEMS device and the metal shielding layer.

2. The method of claim 1, wherein bonding said metal seal ring to said silicon-germanium seal ring comprises forming a eutectic bond between said metal seal ring and said silicon-germanium seal ring.

3. The method of claim 2, wherein said metal seal ring comprises gold, and wherein said eutectic bond forms at a temperature less than approximately 400 degrees Celsius.

4. The method of claim 2, wherein said metal seal ring comprises aluminum, and wherein said eutectic bond forms at a temperature less than approximately 450 degrees Celsius.

5. The method of claim 1, wherein a width of the wall of said metal seal ring is smaller than a width of the wall of said silicon-germanium seal ring.

6. The method of claim 5, wherein the width of the wall of said metal seal ring is approximately in the range of 20-40 microns, and wherein the width of the wall of said silicon-germanium seal ring is approximately in the range of 50-70 microns.

7. The method of claim 1, wherein a combined height of a wall of said vertical seal ring stack and a wall of said silicon-germanium seal ring is approximately in the range of 60-100 microns.

8. The method of claim 1, wherein a second MEMS device is housed in said sealed cavity, and wherein the second MEMS device is disposed on said second substrate, inside of a region enclosed by said metal seal ring.

9. The method of claim 1, wherein said MEMS device is disposed on said second substrate, inside of the region enclosed by said metal seal ring.

10. The method of claim 1, wherein said metal shielding layer comprises a material selected from the group consisting of titanium, tungsten, chromium and alloys thereof.

11. The method of claim 1, wherein bonding said metal seal ring to said silicon-germanium seal ring comprises bonding in a reduced pressure atmosphere.

12. The method of claim 1, wherein bonding said metal seal ring to said silicon-germanium seal ring comprises bonding in an ambient atmosphere.

13. The method of claim 1, wherein bonding said metal seal ring to said silicon-germanium seal ring comprises bonding in an increased pressure atmosphere.

14. The method as recited in claim 1 wherein the metal seal ring has a width, prior to bonding, smaller than a seed layer.

15. The method as recited in claim 1 further comprising:

forming an interconnect in the first substrate to electrically couple the MEMS device through the interconnect, the silicon-germanium seal ring, and the metal seal ring, to the metal shielding layer.

16. The method as recited in claim 1 further comprising:

forming the metal shielding layer on the sidewall of the vertical seal ring stack inside of a region enclosed by said metal seal ring.

17. The method as recited in claim 1 further comprising:

forming the metal shielding layer on the sidewall of the vertical seal ring stack outside of a region enclosed by said metal seal ring.

18. The method as recited in claim 1 further comprising:

forming a grounding interconnect on the second substrate that is electrically connected through the metal shielding layer to the MEMS device after the bonding.

19. The method as recited in claim 1 comprising:

forming a set of trenches in a top surface of said second substrate, outside of the region enclosed by said metal seal ring;

thinning said second substrate, from a bottom surface of said second substrate, to expose said set of trenches and to provide a set of windows in said second substrate;

dicing said second substrate outside of the region enclosed by said metal seal ring, wherein said set of windows is used as a set of alignment marks for the dicing; and

dicing said first substrate outside of the region enclosed by said silicon-germanium seal ring.

20. The method of claim 19, wherein each trench of said set of trenches is formed to a depth approximately in the range of 100-400 microns.

21. The method of claim 19, wherein thinning said first substrate comprises grinding the bottom surface of said first substrate.

22. A method comprising:

forming a silicon-germanium seal ring on a first substrate;

forming a metal seal ring above a second substrate, wherein said metal seal ring is formed as part of a metal seal ring stack;

bonding said metal seal ring to said silicon-germanium seal ring to provide a sealed cavity that houses a MEMS device;

forming a metal shielding layer on said second substrate including on a sidewall of the metal seal ring stack, inside of a region enclosed by said metal seal ring, prior to bonding said metal seal ring to said silicon-germanium seal ring; and

forming an interconnect in the first substrate to electrically couple the MEMS device through the interconnect and the silicon-germanium seal ring to the metal shielding layer.

23. A method, comprising:

forming a silicon-germanium seal ring on a first substrate;

forming a metal seal ring on a second substrate;

forming inlets in the second substrate to provide an opening to a cavity, the inlets having a V-groove profile with a wider portion closer to the MEMS device, the inlets arranged to provide constructive interference of sound waves; and

bonding said metal seal ring to said silicon-germanium seal ring to provide the cavity that houses a MEMS device disposed on the first substrate.

24. A method, comprising:

forming a silicon-germanium seal ring on a first substrate;

forming a metal seal ring on a second substrate;

forming inlets in the second substrate to provide an opening to a cavity, the inlets having a V-groove profile with a wider portion closer to the MEMS device, the inlets arranged to provide constructive interference of optical waves; and

bonding said metal seal ring to said silicon-germanium seal ring to provide the cavity that houses a MEMS device disposed on the first substrate.