3D MEMS device and method of manufacturing

• US 9,309,106 B2
• Filed: 02/13/2015
• Issued: 04/12/2016
• Est. Priority Date: 07/08/2013
• Status: Active Grant

• Current Assignee: Motion Engine inc
• Original Assignee: Motion Engine inc
• Inventors: Boysel, Robert Mark, Ross, Louis
• Primary Examiner(s): Lee, Hsien Ming
• Application Number:
  US14/622,619
• Publication Number:
  US 20150191345A1
• Time in Patent Office: 424 Days
• Field of Search: 257414-418, 257/420, 257/686, 438 48- 56, 438/67, 438/74
• US Class Current: 1/1
• CPC Class Codes: B81B 2207/095 through the lid
• CPC Class Codes: B81B 2207/096 through the substrate
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals
• CPC Class Codes: B81C 1/00301 Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
• CPC Class Codes: H01L 2224/49171 Fan-out arrangements
• CPC Class Codes: H01L 2224/94 at wafer-level, i.e. with connecting carried out on a wafer comprising a plurality of undiced individual devices

Abstract

A MEMS device is provided. The device includes a MEMS wafer, a top cap wafer and a bottom cap wafer. The top and bottom cap wafers are respectively bonded to first and second sides of the MEMS wafer, the MEMS and cap wafers being electrically conductive. The outer side of the top cap wafer is provided with electrical contacts. The MEMS wafer, the top cap wafer and the bottom cap wafer define a cavity for housing a MEMS structure. The device includes insulated conducting pathways extending from within the bottom cap wafer, through the MEMS wafer and through the top cap wafer. The pathways are connected to the respective electrical contacts on the top cap wafer, for routing electrical signals from the bottom cap wafer to the electrical contacts on the top cap wafer. A method of manufacturing the MEMS device is also provided.

Claims

1. A three dimensional (3D) MEMS device comprising:

an electrically conductive MEMS wafer including a MEMS structure, the MEMS wafer having a first side and a second side;

an electrically conductive top cap wafer having an inner top cap side and an outer top cap side, the inner top cap side being bonded to the first side of the MEMS wafer, the outer top cap side having electrical contacts on or over the electrically conductive top cap wafer;

an electrically conductive bottom cap wafer having an inner bottom cap side and an outer bottom cap side, the inner bottom cap side being bonded to the second side of the MEMS wafer such that the MEMS wafer, the top cap wafer and the bottom cap wafer define a cavity for housing the MEMS structure; and

insulated conducting pathways extending from the bottom cap wafer, through the MEMS wafer and through the top cap wafer, to the electrical contacts such that the insulated conducting pathways are operative to conduct electrical signals from portions of the insulated conductive pathways that extend within the bottom cap wafer to the electrical contacts on or over the top cap wafer.

2. The 3D MEMS device according to claim 1, wherein at least one of the insulated conducting pathways comprises a portion formed by a channel extending through the entire thickness of at least the corresponding top cap wafer or the MEMS wafer or the bottom cap wafer.

3. The 3D MEMS device according to claim 2, wherein the channel has a sidewall coated with an insulating material, the inside of the channel being filled with a conducting material.

4. The 3 D MEMS device according to claim 1, wherein at least one of the insulated conducting pathways comprises a portion formed by a trench surrounding a conductive wafer plug.

5. The 3D MEMS device according to claim 4, wherein the trench is filled with an insulating material.

6. The 3D MEMS device according to claim 1, wherein said insulated conducting pathways each comprises a top cap wafer channel, a MEMS wafer channel and a bottom cap wafer channel, said channels being aligned at a first wafer interfaces between the top cap wafer and the MEMS wafer and a second wafer interface between the MEMS wafer and the bottom cap wafer.

7. The 3D MEMS device according to claim 6, wherein for at least one of the insulated conducting pathways, the top cap wafer channel and the bottom cap wafer channel respectively comprises a through silicon via (TSV).

8. The 3D MEMS device according to claim 1, wherein at least one of the electrical contacts on the top cap wafer is connectable to an external potential, the corresponding insulated conducting pathway being a case pathway located at the periphery of the device.

9. The 3D MEMS device according to claim 1, wherein the outer bottom cap side of the bottom cap wafer has electrical contacts, at least one of the insulated conducting pathways being a device feedthrough extending from one of the electrical contacts on the top cap wafer to one of the electrical contacts on the bottom cap wafer.

10. The 3D MEMS device according to claim 1, wherein the bottom cap wafer comprises bottom cap electrodes, some of the insulated conducting pathways being respectively connected to the bottom cap electrodes, for transmitting electrical signals between the bottom cap electrodes and corresponding electrical contacts on the top cap wafer.

11. The 3D MEMS device according to claim 1, comprising at least one additional insulated conducting pathway extending through the MEMS wafer and through the top cap wafer, said at least one additional insulated conducting pathway connecting the MEMS structure to one of the electrical contacts on the top cap wafer such that the at least one additional insulated conducting pathway transmits electrical signals between the MEMS structure and said one electrical contact.

12. The 3D MEMS device according to claim 1, wherein the MEMS wafer is a silicon-on-insulator (SOI) wafer with an insulating layer separating a device layer from a handle layer, the insulated conducting pathways comprising respective SOI conducting shunts, electrically connecting the device and handle layers.

13. The 3D MEMS device according to claim 12, wherein the MEMS structure is patterned in both the device layer and the handle layer.

14. The 3D MEMS device according to claim 1, wherein the top cap wafer comprises top cap electrodes, the MEMS device comprising other additional insulated conducting pathways respectively extending through the top cap wafer between said top cap electrodes and corresponding electrical contacts on the top cap wafer, for transmitting electrical signals between the top cap electrodes and the corresponding electrical contacts on the top cap wafer.

15. The 3D MEMS device according claim 1, comprising a cap insulating layer deposited on at least one of the outer top cap side of the top cap wafer and the outer bottom cap side of the bottom cap wafer.

16. The 3D MEMS device according to claim 1, wherein the top cap wafer, the MEMS wafer and the bottom cap wafer are made of a silicon semiconductor and wherein the top cap wafer, the MEMS wafer and optionally, the bottom cap wafer are bonded with a conductive bond.

17. The 3D MEMS device according to claim 1, wherein the cavity is hermetically sealed and wherein the cavity is under vacuum or contains fluid.

18. A method for manufacturing a three dimensional MEMS device, the method comprising the steps of:

forming insulated conducting cap wafer channels on an inner side of a first cap wafer and on an inner side of a second cap wafer;

patterning first portions of a MEMS structure and portions of insulated conducting MEMS wafer channels in a first side of a MEMS wafer;

bonding said first side of the patterned MEMS wafer to the inner side of the first cap wafer by aligning the insulated conducting cap wafer channels of said first cap wafer with the portions of the insulated conducting MEMS wafer channels;

patterning second portions of the MEMS structure and further portions of the insulated conducting MEMS wafer channels on a second side of the MEMS wafer;

further bonding the second side of the patterned MEMS wafer to the inner side of the second cap wafer, by aligning such that the insulated conducting cap wafer channels of said second cap wafer are aligned with the further portions of the insulated conducting MEMS wafer channels, thereby forming insulated conducting pathways extending from within the second cap wafer, through the MEMS wafer and through the first cap wafer; and

removing a portion of the an outer sides side of the first cap wafer and a portion of an outer side of the second cap wafer to expose the insulated conducting pathways.

19. The method for manufacturing the three dimensional MEMS device according to claim 18, wherein the forming step comprises patterning trenches on the inner sides of the first cap wafer and the second cap wafer, the trenches extending only partially through the first cap wafer and second cap wafer;

and filling the trenches with an insulating material.

20. The method for manufacturing the three dimensional MEMS device according to claim 18, wherein the forming step comprises patterning a recess in the first cap wafer that comprises a top cap wafer to form part of a cavity for housing the MEMS structure.

21. The method for manufacturing the three dimensional MEMS device according to claim 18, wherein the forming step comprises patterning trenches on the first cap wafer and the second cap wafer and filling the trenches for forming to form cap wafer electrodes and/or leads.

22. The method for manufacturing the three dimensional MEMS device according to claim 18, the MEMS wafer being an a silicon-on-insulator (SOI) wafer with an insulating layer separating a device layer from a handle layer, wherein the patterning first portions step comprises forming SOI conducting shunts through the device layer and the insulating layer, and further comprising etching trenches surrounding some one or more of the SOI conducting shunts, for forming said further portions of the insulated conducting MEMS wafer channels.

23. The method for manufacturing the three dimensional MEMS device according to claim 18, wherein the patterning first portions step comprises etching trenches on the first side of the MEMS wafer for forming MEMS electrodes and/or leads.

24. The method for manufacturing the three dimensional MEMS device according to claim 18, wherein the bonding step comprises bonding a top cap wafer to the first side of the MEMS wafer with a conductive bond and wherein the further bonding step comprises bonding a bottom cap wafer to the second side of the MEMS wafer with a conductive bond, the conductive bond comprising a bonding layer or a fusion bond.

25. The method for manufacturing the three dimensional MEMS device according to claim 18, wherein the patterning second portions step comprises etching trenches on the second side of the MEMS wafer to form a further portion of the MEMS structure and to form conductive wafer plugs part of the insulated conducting MEMS wafer channels.

26. The method for manufacturing the three dimensional MEMS device according to claim 18, wherein the removing step comprises grinding and polishing the outer sides of the first cap wafer comprising a top cap wafer and the second cap wafer comprising a bottom cap wafer and wherein the removing step comprises electrically passivating the outer sides of the top cap wafer and the bottom cap wafer with cap insulating layers.

27. The method for manufacturing the three dimensional MEMS device according to claim 18, further comprising forming electrical contacts on the outer side of the first cap wafer comprising a top cap wafer connected with the insulated conducting pathways, such that the insulated conducting pathways conduct electrical signals from the second cap wafer comprising a bottom cap wafer to said electrical contacts on the top cap wafer.

28. The method for manufacturing the three dimensional MEMS device according to claim 27, wherein the electrical contacts forming step further comprises forming electrical contacts on an outer side of the bottom cap wafer connected to one or more of the insulated conducting pathways, allowing routing of electrical signals to the electrical contacts on the bottom cap wafer.

29. The method for manufacturing the three dimensional MEMS device according to claim 28, wherein the electrical contacts forming step comprises forming openings in the a cap insulating layer on an outer side of the top cap wafer and/or the bottom cap wafer, said openings being in line with the insulated conducting cap wafer channels;

applying a metallic layer on said cap insulating layer and patterning the metallic layer to form electrical leads and bond pads; and

applying a passivating film over the electrical leads and the bond pads, and forming openings in said passivating film over the bond pads.

30. A three dimensional (3D) MEMS device comprising:

an electrically conductive MEMS wafer including a MEMS structure, the MEMS wafer having a first side and a second side;

an electrically conductive top cap wafer having an inner top cap side and an outer top cap side, the inner top cap side being bonded to the first side of the MEMS wafer, the outer top cap side having electrical contacts;

an electrically conductive bottom cap wafer having an inner bottom cap side and an outer bottom cap side, the inner bottom cap side being bonded to the second side of the MEMS wafer such that the MEMS wafer, the top cap wafer and the bottom cap wafer define a cavity for housing the MEMS structure; and

insulated conducting pathways extending from the bottom cap wafer, through the MEMS wafer and through the top cap wafer, to respective electrical contacts such that the insulated conducting pathways are operative to conduct electrical signals from portions of the insulated conducting pathways extending from within the bottom cap wafer to the electrical contacts on the top cap wafer, wherein at least one of said insulated conducting pathways comprises a top cap wafer channel, a MEMS wafer channel and a bottom cap wafer channel, said channels being aligned at a first wafer interface between the top cap wafer and the MEMS wafer and a second wafer interface between the MEMS wafer and the bottom cap wafer.