Wafer level method of capping multiple MEMS elements

• US 6,448,109 B1
• Filed: 11/15/2000
• Issued: 09/10/2002
• Est. Priority Date: 11/15/2000
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Karpman, Maurice S.
• Primary Examiner(s): Fourson, George
• Assistant Examiner(s): Pham, Thanh V
• Application Number:
  US09/713,693
• Time in Patent Office: 664 Days
• Field of Search: 156/182, 156/299, 156/300, 438/51, 438/55, 438/108, 438/113-127, 438/455-459, 438/462, 438/464
• US Class Current: 438/108
• CPC Class Codes: B81B 7/0077 Other packages not provided for in groups B81B7/0035 - B81B7/0074
• CPC Class Codes: B81C 1/00873 characterised by special arrangements of the devices, allowing an easier separation
• CPC Class Codes: H01L 21/50 Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
• CPC Class Codes: H01L 2924/15153 the die mounting substrate comprising a recess for hosting the device
• CPC Class Codes: Y10T 156/1092 All laminae planar and face to face

Abstract

Individual caps are provided for mutually spaced MEMS on a common wafer by establishing a fixed spatial array of caps in positions that correspond to the positions of the MEMS on the wafer, and simultaneously bonding the caps to corresponding MEMS. The caps are preferably held in place within recesses in a template, and include protective sealing rings that are bonded to the MEMS wafer. The wafer is diced into individual MEMS chips after the caps have been bonded. The caps can be provided with circuitry that faces away from MEMS wafer and is wire bonded to the wafer, or that faces towards the wafer with a flip-chip mounting.

Claims

1. A method of capping a plurality of mutually spaced microelectromechanical systems (MEMS) on a common wafer, comprising:

establishing a fixed spatial array of discrete, mutually spaced caps for said MEMS, with the caps positioned within the array at locations corresponding to the positions of said MEMS on said wafer, and

simultaneously bonding said caps to said wafer to cap corresponding ones of said MEMS.

2. The method of claim 1, wherein said caps are removeably positioned in said array by a common cap holder.

3. The method of claim 2, wherein said cap holder comprises a template with an array of recesses for holding respective caps.

4. The method of claim 3, wherein said recesses have depths that cause said caps to be substantially coplanar.

5. The method of claim 1, wherein said caps are bonded to said MEMS with protective ring seals.

6. The method of claim 5, wherein said caps are bonded to said MEMS by applying ring seals to a plurality of caps, inspecting said caps and ring seals, and bonding only caps which pass said inspection over said MEMS.

7. The method of claim 1, further comprising the step of dicing said wafer into individual MEMS chips after said caps have been bonded.

8. The method of claim 1, said caps and wafer having different thermal coefficients of expansion, wherein said caps are bonded to said MEMs at a temperature that would be high enough to cause excessive strain in the materials used for the caps and common wafer if a single continuous cap wafer were bonded to the common wafer, further comprising the step of processing said wafer after said caps have been bonded.

9. The method of claim 1, wherein electrical circuits for said MEMS are provided on their respective caps, and said caps are flip-chip bonded to said wafer.

10. The method of claim 1, wherein electrical circuits for said MEMS are provided on one side of their respective caps, contact pads for said circuits are provided on said wafer, said caps are bonded to their respective MEMS with their circuit sides facing away from said wafer, and said contact pads are thereafter wire bonded to said circuits.

11. A method of capping a plurality of mutually spaced microelectromechanical systems (MEMS) on a common wafer, comprising:

providing a cap template having an array of mutually spaced recesses sized to removeably retain caps of a desired size for said MEMS,

placing individual caps for respective ones of said MEMS in respective recesses of said array,

positioning said wafer with respect to said array so that said caps are aligned with their respective MEMS,

bonding said caps in said template recesses to said wafer to form protective seals around their respective MEMS,

removing said caps from said recesses, and

dicing said wafer into individual MEMS chips.

12. The method of claim 11, wherein said recesses have side walls that are sloped outwards to facilitate placement of said caps in their respective recesses.

13. The method of claim 11, wherein ring seals are formed on said caps, said caps and ring seals are inspected, and only those caps which pass said inspection are bonded to said wafer, with said ring seals forming said protective seals.

14. The method of claim 11, wherein said caps are originally provided as a common cap wafer, ring seals are formed on said caps in their wafer state, said cap wafer is thereafter diced into said individual caps, and said ring seals form said protective seals when said caps are bonded to said MEMS wafer.

15. The method of claim 11, wherein electrical circuits for said MEMS are provided on their respective caps, and said caps are flip-chip bonded to said wafer.

16. The method of claim 11, wherein electrical circuits for said MEMS are provided on one side of their respective caps, contact pads for said circuits are provided on said wafer, said caps are bonded to their respective MEMS with their circuit sides facing away from said wafer, and said contact pads are thereafter wire bonded to said circuits.